JP2898435B2 - Optical transmission system for wireless link - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a case where a main base station which modulates and demodulates a baseband signal and a slave base station provided with a transmission / reception device for transmitting / receiving a terminal station via a radio line are separated. The present invention relates to an optical transmission system for a wireless link for transmitting a signal to be transmitted / received via the wireless line (hereinafter, referred to as a signal for a wireless link) using an optical fiber cable, and particularly to an automobile telephone system and a personal communication system The present invention relates to an optical transmission system for a wireless link applicable to a mobile communication system such as the above.

[0002]

2. Description of the Related Art In a conventional mobile communication system, a base station performs a signal processing of a baseband signal, so that the configuration of the base station becomes complicated and large, and a small radius of a zone requiring a large number of base stations is required. It has become difficult to install base stations in each of the cell zone or pico cell zone. In order to solve this problem, the slave base station covering the micro cell zone or the pico cell zone is not provided with a signal processing device for a baseband signal, but is provided with only a transmission / reception device for only analog signal processing related to wireless communication, and Simplification has been proposed.

Specifically, for example, after modulating a carrier with a multiplexed signal obtained by multiplexing a baseband signal in a main base station, the modulated signal is transmitted via a wireless line or a wired line using a coaxial cable. Transmit to the slave base station. Then, the slave base station frequency-converts the received modulated signal into a radio signal, transmits the radio signal to the mobile terminal station, and performs radio communication.

[0004]

However, in this conventional system, when a main base station and a sub base station are connected via a radio line, a large number of connections are made between the main base station and a plurality of sub base stations. Since it is necessary to set up a wireless line, it is difficult to effectively use radio waves, and the wireless lines connecting the main base station and the slave base station, as well as the wireless line, the slave base station, and the mobile terminal station, There is a problem that it is necessary to avoid the problem of radio wave interference with the wireless line connecting the.

In the above-mentioned conventional system, when the main base station and the subordinate base station are connected via a wired line using a coaxial cable, there is an upper limit in the carrier frequency due to the line loss of the coaxial cable. And the distance between the master base station and the slave base station is limited.

An object of the present invention is to solve the above problems, to have a simpler structure than the conventional example, and to connect a main base station and a subordinate base station without using a radio line and to transmit a radio link signal. An object of the present invention is to provide an optical transmission system for a wireless link capable of transmitting.

[0007]

According to the first aspect of the present invention, there is provided an optical transmission system for a radio link, comprising: a main base station; a sub base station provided at a predetermined distance from the main base station; An optical transmission system for a radio link, comprising first and second optical transmission lines connecting said master base station and said slave base station, wherein said master base station converts a carrier signal into a first information signal. Modulating means for modulating the modulated signal to output a modulated signal; and converting the modulated signal output from the modulating means into a light signal and outputting a first optical signal including the modulated signal to the first optical transmission line. First electrical-optical conversion means, and second electrical-optical conversion means for performing electrical-optical conversion of the local oscillation signal and outputting a second optical signal including the local oscillation signal to the second optical transmission line. And the slave base station transmits the second electrical-optical conversion means to the second base station. First optical-to-electrical conversion means for performing optical-to-electrical conversion of the second optical signal transmitted via the transmission line and outputting the local oscillation signal; In response to the first optical signal transmitted via the optical transmission line, converts the modulated signal included in the first optical signal into the local oscillation signal output from the first optical-to-electrical conversion means. It is characterized by comprising frequency conversion means for converting the frequency of the signal into a radio signal using a signal, and transmission means for transmitting the radio signal frequency-converted by the frequency conversion means to the terminal station of the slave base station.

According to a second aspect of the present invention, in the optical transmission system for a wireless link according to the first aspect, the slave base station further transmits a second information signal wirelessly transmitted from the terminal station. Receiving means for receiving a wireless signal including the wireless signal, electrical-optical conversion of the wireless signal received by the receiving means, and third electrical-optical conversion means for outputting a third optical signal to a third optical transmission line; Wherein the main base station further optically / electrically converts the third optical signal transmitted from the third electric / optical conversion means via the third optical transmission line and receives the third optical signal. The second light that outputs a radio signal
And a demodulator for demodulating the received wireless signal output from the second optical-electrical converter and outputting the second information signal.

According to a third aspect of the present invention, there is provided an optical transmission system for a radio link, comprising: a main base station; a sub base station provided at a predetermined distance from the main base station; An optical transmission system for a wireless link, comprising first, second, and third optical transmission lines connecting a slave base station,
The main base station modulates a carrier signal with a first information signal to output a modulated signal, and a first signal including a modulated signal output from the modulating means being subjected to electro-optical conversion and including the modulated signal. A first optical signal to be output to the first optical transmission line.
And electrical and optical conversion means for converting the local oscillation signal to electrical and optical and outputting a second optical signal including the local oscillation signal to the second optical transmission line. Prepared,
The slave base station optically / electrically converts a second optical signal transmitted from the second electrical / optical conversion means via the second optical transmission line and outputs the local oscillation signal. Light of·
An electric conversion unit, and the modulation signal included in the first optical signal in response to a first optical signal transmitted from the first electric / optical conversion unit via the first optical transmission line. To
First frequency conversion means for converting the frequency of the local oscillation signal output from the first optical-to-electrical conversion means into a radio signal, and converting the radio signal frequency-converted by the first frequency conversion means to Transmitting means for wirelessly transmitting to a terminal station of a slave base station, receiving means for receiving a wireless signal including a second information signal wirelessly transmitted from the terminal station, and a wireless signal received by the receiving means, The first light
A second frequency converting means for converting the frequency of the intermediate frequency signal into an intermediate frequency signal using the local oscillation signal output from the electric converting means, A third optical-to-optical converter for outputting a third optical signal to the third optical transmission line, wherein the main base station further includes a third optical-to-optical converter that outputs the third optical signal from the third optical-to-optical converter. A second optical-to-electrical conversion unit that performs optical-to-electrical conversion of the third optical signal transmitted via the transmission line and outputs the intermediate frequency signal, and an output from the second optical-to-electrical conversion unit Demodulating means for demodulating the intermediate frequency signal and outputting the second information signal.

According to a fourth aspect of the present invention, there is provided an optical transmission system for a radio link, comprising: a main base station; a sub base station provided at a predetermined distance from the main base station; An optical transmission system for a wireless link, comprising first, second, and third optical transmission lines connecting a slave base station,
The main base station modulates a carrier signal with a first information signal to output a modulated signal, and a first signal including a modulated signal output from the modulating means being subjected to electro-optical conversion and including the modulated signal. A first optical signal to be output to the first optical transmission line.
And a non-linear electrical-optical conversion characteristic, wherein the local oscillation signal is converted into a fundamental component and at least one harmonic component of the local oscillation signal using the nonlinear electrical-optical conversion characteristic. A second electrical-optical conversion means for performing electrical-optical conversion to generate a second optical signal including a fundamental component and at least one harmonic component of the local oscillation signal to the second optical transmission line; Wherein the slave base station optically / electrically converts a second optical signal transmitted from the second electric / optical conversion means via the second optical transmission line, and converts the second oscillation signal into a local oscillation signal. First optical-electrical conversion means for outputting a fundamental wave component and at least one harmonic component, and a fundamental wave component and at least one harmonic of the local oscillation signal output from the first optical-electrical conversion means The height of one of the predetermined components A first filtering means for band-pass filtering a wave component; and a first optical signal transmitted from the first electrical / optical conversion means via the first optical transmission line, the first optical signal A first frequency converter for frequency-converting the modulated signal included in the first optical signal into a wireless signal using the harmonic component band-filtered by the first filter;
Transmitting means for wirelessly transmitting a radio signal frequency-converted by the first frequency converting means to a terminal station of the slave base station; and a fundamental wave of the local oscillation signal output from the first optical-electrical converting means A second filtering means for band-filtering a predetermined one of the components and at least one harmonic component, and a radio signal including a second information signal wirelessly transmitted from the terminal station. Receiving means for receiving, and second frequency converting means for frequency-converting the radio signal received by the receiving means into an intermediate frequency signal using the harmonic component band-filtered by the second filtering means And third electrical-optical conversion means for electrical-optical conversion of the intermediate frequency signal frequency-converted by the second frequency conversion means and outputting a third optical signal to the third optical transmission line. Equipped, the above main group The station further optically / electrically converts the third optical signal transmitted from the third electrical / optical conversion means via the third optical transmission line and outputs the intermediate frequency signal. A light-to-electricity conversion means, and a demodulation means for demodulating the intermediate frequency signal output from the second light-to-electricity conversion means and outputting the second information signal.

According to a fifth aspect of the present invention, there is provided an optical transmission system for a radio link, comprising: a main base station; a sub base station provided at a predetermined distance from the main base station; An optical transmission system for a wireless link, comprising first, second, and third optical transmission lines connecting a slave base station,
The main base station modulates a carrier signal with a first information signal to output a modulated signal, and a first signal including a modulated signal output from the modulating means being subjected to electro-optical conversion and including the modulated signal. A first optical signal to be output to the first optical transmission line.
And a non-linear electrical-optical conversion characteristic, wherein the local oscillation signal is converted into a fundamental component and at least one harmonic component of the local oscillation signal using the nonlinear electrical-optical conversion characteristic. A second electrical-optical conversion means for performing electrical-optical conversion to generate a second optical signal including a fundamental component and at least one harmonic component of the local oscillation signal to the second optical transmission line; Wherein the slave base station optically / electrically converts a first optical signal transmitted from the first electrical / optical conversion means via the first optical transmission line, and outputs the modulated signal. A first optical-to-electrical converting unit that responds to a second optical signal transmitted from the second electrical-to-optical converting unit via the second optical transmission line.
A first frequency for frequency-converting the modulated signal output from the electric conversion means into a radio signal using a predetermined harmonic component among a fundamental component and at least one harmonic component included in the optical signal; Converting means; transmitting means for wirelessly transmitting a radio signal frequency-converted by the first frequency converting means to the terminal station of the slave base station;
The second optical signal transmitted through the second optical transmission line from the electrical / optical converter is optically / electrically converted to output a fundamental component and at least one harmonic component of the local oscillation signal. A third optical-to-electrical conversion unit, and a predetermined one of the fundamental component and at least one harmonic component of the local oscillation signal output from the third optical-to-electrical conversion unit. Filtering means for performing band filtering, receiving means for receiving a wireless signal including a second information signal wirelessly transmitted from the terminal station, and filtering the wireless signal received by the receiving means by the filtering means. A second frequency converting means for converting the frequency of the filtered harmonic component into an intermediate frequency signal, and a third frequency converting means for converting the intermediate frequency signal frequency-converted by the second frequency converting means into a third signal. Up the light signal A third electrical / optical conversion means for outputting to the third optical transmission line, wherein the main base station is further transmitted from the third electrical / optical conversion means via the third optical transmission line. A second optical-to-electrical conversion means for optically / electrically converting the third optical signal to output the intermediate frequency signal, and demodulating the intermediate frequency signal output from the second optical / electrical conversion means And demodulating means for outputting the second information signal.

According to a sixth aspect of the present invention, in the optical transmission system for a wireless link according to the first, second, third, fourth or fifth aspect, the first and second optical signals are wavelength-multiplexed. And transmitted via one optical transmission line.

According to a seventh aspect of the present invention, in the optical transmission system for a wireless link according to the second, third, fourth or fifth aspect, the first, second and third optical signals are wavelength-division multiplexed. And transmitted via one optical transmission line.

[0014]

In the optical transmission system for a radio link according to the first aspect, in the main base station, the modulating means modulates a carrier signal with a first information signal and outputs a modulated signal. The electric / optical conversion means converts the modulated signal output from the modulating means to electric light, and outputs a first optical signal including the modulated signal to the first optical transmission line. On the other hand, the second electrical-optical converter converts the local oscillation signal into an optical signal, and outputs a second optical signal including the local oscillation signal to the second optical transmission line. In the slave base station, the first optical / electrical conversion means converts a second optical signal transmitted from the second electrical / optical conversion means via the second optical transmission line into an optical / electrical conversion. After outputting the local oscillation signal, the frequency converting means responds to the first optical signal transmitted from the first electric / optical converting means via the first optical transmission line, The modulation signal included in the first optical signal is frequency-converted into a radio signal using the local oscillation signal output from the first optical-electrical conversion unit. Next, the transmitting means wirelessly transmits the radio signal frequency-converted by the frequency converting means to the terminal station of the slave base station.

In the optical transmission system for a wireless link according to the first aspect of the present invention, the main base station and the subordinate base station are connected using the first and second optical transmission lines. Therefore, it is possible to eliminate radio wave interference from the power supply system to a wireless line set between the slave base station and the terminal station. By appropriately setting the carrier frequency and the local oscillation frequency of the first information signal on the main base station side, the radio frequency in the radio line set between the slave base station and the terminal station can be set to an arbitrary value. Therefore, there is an advantage that the radio frequency can be easily set in a plurality of microcell zones formed by a plurality of slave base stations, for example. Further, since the slave base station does not include the signal processing device for the information signal, the configuration of the slave base station can be reduced in size and economy, and the slave base station is installed in a smaller space. be able to. Therefore, it is possible to install a large number of wireless devices for each wireless channel in each microcell zone in a predetermined installation space of the slave base station. Further, the frequency stability of the high-frequency signal transmitted from the slave base station includes the frequency stability of the carrier signal of the modulated signal contained in the optical signal input to the frequency conversion means, and the frequency stability of the local oscillation signal. It is easily used as a transmission signal in a radio line by increasing the stability of the oscillation frequency of the carrier signal generator and the stability of the oscillation frequency of the local oscillation signal generator in the main base station. The frequency stability of the high-frequency signal can be increased.

In the optical transmission system for a wireless link according to the present invention, preferably, the slave base station is further wirelessly transmitted from the terminal station. Receiving means for receiving a wireless signal including a second information signal; and a third means for converting the wireless signal received by the receiving means into an optical signal and outputting a third optical signal to a third optical transmission line. Electrical / optical conversion means, wherein the main base station further converts the third optical signal transmitted from the third electrical / optical conversion means via the third optical transmission line into optical / electrical conversion. A second optical-to-electrical conversion means for outputting the received radio signal,
And demodulating means for demodulating the received wireless signal output from the optical-to-electrical converting means and outputting the second information signal.

Further, in the optical transmission system for a wireless link according to claim 3, in the main base station, the modulating means modulates a carrier signal with a first information signal and outputs a modulated signal. The first electrical-optical conversion means performs electrical-optical conversion of the modulation signal output from the modulation means, and outputs a first optical signal including the modulation signal to the first optical transmission line. On the other hand, the second electrical-optical converter converts the local oscillation signal into an optical signal, and outputs a second optical signal including the local oscillation signal to the second optical transmission line. In the slave base station, the first optical / electrical conversion means converts a second optical signal transmitted from the second electrical / optical conversion means via the second optical transmission line into an optical / electrical conversion. And outputting the local oscillation signal, the first frequency conversion means responds to the first optical signal transmitted from the first electric / optical conversion means via the first optical transmission line. Then, the modulation signal included in the first optical signal is frequency-converted into a radio signal using the local oscillation signal output from the first optical-electrical conversion means. Next, the transmitting means wirelessly transmits the radio signal frequency-converted by the first frequency converting means to the terminal station of the slave base station. On the other hand, after receiving the wireless signal including the second information signal wirelessly transmitted from the terminal station, the second frequency conversion unit converts the wireless signal received by the receiving unit into the wireless signal. After frequency conversion into an intermediate frequency signal using the local oscillation signal output from the first optical-to-electrical converter, the third electrical-to-optical converter is frequency-converted by the second frequency converter. The third optical signal is output to the third optical transmission line by converting the intermediate frequency signal into an electrical signal and an optical signal. Further, in the main base station, the second optical-to-electrical conversion means converts the third optical signal transmitted from the third electrical-to-optical conversion means via the third optical transmission line into an optical signal.・ After electrical conversion and output of the above intermediate frequency signal,
The demodulation means demodulates the intermediate frequency signal output from the second optical / electrical conversion means and outputs the second information signal.

Here, the received radio signal can be down-converted to a lower intermediate frequency signal using the local oscillation signal by the second frequency conversion means, and transmitted to the main base station. It can be used as a modulated signal for modulating the third optical signal. Since the received radio signal can be frequency-converted to a lower frequency, the third signal having the lower highest driving frequency
Electrical-optical conversion means can be used. In addition, since a local oscillation signal obtained by optical-to-electrical conversion of the optical signal transmitted from the main base station is used for frequency conversion of the received radio signal, the local oscillation The configuration of the slave base station can be simplified as compared with the case where a generator for generating a signal is provided, thereby making it possible to reduce the size and cost of the slave base station.

In the optical transmission system for a wireless link according to claim 4, in the main base station, the modulating means modulates a carrier signal with a first information signal and outputs a modulated signal. The first electrical-optical conversion means performs electrical-optical conversion of the modulation signal output from the modulation means, and outputs a first optical signal including the modulation signal to the first optical transmission line. On the other hand, the second electrical-optical conversion means has a non-linear electrical-optical conversion characteristic, and converts the local oscillation signal into a fundamental wave component of the local oscillation signal and at least one The second optical signal including the fundamental component of the local oscillation signal and at least one harmonic component is output to the second optical transmission line by performing the electrical / optical conversion so that two harmonic components are generated. In the slave base station, the first optical-to-electrical conversion means includes the second electric / electrical conversion means.
After optical-to-electrical conversion of the second optical signal transmitted from the optical conversion means via the second optical transmission line to output a fundamental component and at least one harmonic component of the local oscillation signal, The first filtering unit filters a predetermined one of the fundamental component and at least one harmonic component of the local oscillation signal output from the first optical-to-electrical conversion unit. Waves. Next, the first frequency converting means converts the first electric / optical converting means into the first frequency.
The modulated signal included in the first optical signal in response to the first optical signal transmitted via the optical transmission line, After performing frequency conversion to a radio signal using the component, the transmission unit wirelessly transmits the radio signal frequency-converted by the first frequency conversion unit to the terminal station of the slave base station. On the other hand, the second filtering means is a predetermined one of a fundamental component and at least one harmonic component of the local oscillation signal output from the first optical-to-electrical conversion means. Band-pass filter. Further, the receiving means includes:
After receiving a wireless signal including a second information signal wirelessly transmitted from the terminal station, the second frequency converting means converts the wireless signal received by the receiving means by the second filtering means. The frequency conversion is performed to an intermediate frequency signal using the above-mentioned harmonic component that has been subjected to the band filtering. Next, the third electrical / optical converter converts the intermediate frequency signal, which has been frequency-converted by the second frequency converter, into electrical / optical conversion, and outputs a third optical signal to the third optical transmission line. I do. Further, in the main base station, the second optical-to-electrical converting means converts the third optical signal transmitted from the third electrical-to-optical converting means via the third optical transmission line. After performing the optical-to-electrical conversion and outputting the intermediate frequency signal, the demodulating means demodulates the intermediate frequency signal output from the second optical-electrical converting means and outputs the second information signal. .

Therefore, since the harmonic component of the local oscillation signal generated by the main base station is used as the local oscillation signal in the first and second frequency conversion means of the slave base station, The degree of freedom in setting the transmission / reception frequency of the wireless line between the terminal and the terminal station can be increased as compared with the conventional example.

Further, in the optical transmission system for a wireless link according to claim 5, in the main base station, the modulating means modulates a carrier signal with a first information signal and outputs a modulated signal. The first electric / optical means converts the modulated signal output from the modulating means to electric / optical conversion, and outputs a first optical signal including the modulated signal to the first optical transmission line. On the other hand, the second electrical-optical conversion means has a non-linear electrical-optical conversion characteristic, and converts the local oscillation signal into a fundamental wave component of the local oscillation signal and at least one The second optical signal including the fundamental component of the local oscillation signal and at least one harmonic component is output to the second optical transmission line by performing the electrical / optical conversion so that two harmonic components are generated. In the slave base station, the first optical-to-electrical conversion means includes a first optical-to-optical conversion means that transmits the first optical-to-electrical conversion means via the first optical transmission line.
The optical signal is optically / electrically converted to output the modulated signal.
On the other hand, the first frequency conversion means is configured to output the second electric power
The optical signal includes the modulated signal output from the first optical-to-electrical conversion unit in response to the second optical signal transmitted from the optical conversion unit via the second optical transmission line. The frequency is converted into a radio signal using a predetermined harmonic component of the fundamental component and at least one harmonic component. Next, the transmitting means wirelessly transmits the radio signal frequency-converted by the first frequency converting means to the terminal station of the slave base station. On the other hand, the third optical-to-electrical converter converts the second optical signal transmitted from the second electrical-to-optical converter via the second optical transmission line into an optical signal and an electrical signal. After outputting the fundamental wave component and at least one harmonic component of the oscillation signal, the filtering unit outputs the fundamental wave component and at least one harmonic component of the local oscillation signal output from the third optical-electrical conversion unit. One predetermined harmonic component of the wave components is band-filtered. Further, the receiving means, after receiving a wireless signal including a second information signal wirelessly transmitted from the terminal station, the second frequency converting means converts the wireless signal received by the receiving means into the wireless signal The frequency component is converted into an intermediate frequency signal by using the above-mentioned harmonic component band-filtered by the filtering means. Next, the third electrical / optical converter converts the intermediate frequency signal, which has been frequency-converted by the second frequency converter, into electrical / optical conversion, and outputs a third optical signal to the third optical transmission line. I do. Further, in the main base station, the second optical-to-electrical conversion means converts the third optical signal transmitted from the third electrical-to-optical conversion means via the third optical transmission line into an optical signal.・ After electrical conversion and output of the above intermediate frequency signal,
The demodulation means demodulates the intermediate frequency signal output from the second optical / electrical conversion means and outputs the second information signal.

Accordingly, since the harmonic component of the local oscillation signal generated in the main base station is used as the local oscillation signal in the first and second frequency conversion means of the slave base station, The degree of freedom in setting the transmission / reception frequency of the wireless line between the terminal and the terminal station can be increased as compared with the conventional example.

Further, in the optical transmission system for a wireless link according to the sixth aspect, in the optical transmission system for a wireless link according to the first, second, third, fourth or fifth aspect, preferably, the first and second optical transmission systems are used. Are multiplexed and transmitted via one optical transmission line. Thus, the number of optical transmission lines connected between the master base station and the slave base station can be reduced.

Further, in the optical transmission system for a wireless link according to the seventh aspect, in the optical transmission system for a wireless link according to the second, third, fourth or fifth aspect, preferably, the first, second, and second optical transmission systems are used. The three optical signals are wavelength-multiplexed and 1
It is transmitted via the optical transmission line of the book. Thus, the number of optical transmission lines connected between the master base station and the slave base station can be reduced.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 is a block diagram of a wireless link optical transmission system according to a first embodiment of the present invention.

The optical transmission system for a wireless link according to the first embodiment includes a main base station 100, a subordinate base station 200 provided at a predetermined distance from the main base station 100, and a subordinate base station 100. Three optical fiber cables FC1 to FC3 for connecting to the base station 200;
And a mobile terminal station 300 connected via a wireless line, and is obtained by FM-modulating a carrier signal with a baseband signal (hereinafter abbreviated as a BB signal in the drawings).
The M signal is optically modulated and converted into a first optical signal, and the first optical signal is transmitted to the slave base station 2 via the optical fiber cable FC1.
00, the local oscillation signal is optically modulated and converted into a second optical signal, and the second optical signal is transmitted to the slave base station 200 via the optical fiber cable FC2. The first optical signal is directly input to the mixer 41 after being amplified, while the second optical signal is optically detected, a local oscillation signal is demodulated and input to the mixer 41, and the first optical signal is input to the mixer 41. Is directly transmitted to the mobile terminal station 30 using the local oscillation signal.
It is characterized in that it is frequency-converted into a radio transmission signal for 0.

As shown in FIG. 1, the main base station 100 includes laser diodes 10 and 20, optical modulators 11 and 21,
It includes a baseband signal generator 12, an FM modulator 13, a local oscillation signal generator 22, an optical detector 30, and an FM demodulator 31. On the other hand, the slave base station 200
0, a mixer 41, an optical detector 42, an amplifier 43,
It includes a band-pass filter 44, a transmission power amplifier 45, an antenna duplexer 46, a transmission / reception antenna 50, a reception amplifier 47, a laser diode 48, and an optical modulator 49.

In the main base station 100, the optical signal generated by the laser diode 10 is input to the optical modulator 11. On the other hand, the baseband signal generated by the baseband signal generator 12 is input to the FM modulator 13 and the frequency f
The s carrier signal is FM-modulated with the baseband signal, and the baseband FM signal is input to the optical modulator 11. The optical signal input to the optical modulator 11 is intensity-modulated by the FM signal, and then transmitted to the optical amplifier 40 in the slave base station 200 via the optical fiber cable FC1.

On the other hand, the optical signal generated by the laser diode 20 is input to an optical modulator 21, and the optical signal is intensity-modulated by a local oscillation signal having a frequency fl output from a local oscillation signal generator 22. The signal is transmitted to the optical detector 42 in the slave base station 200 via the optical fiber cable FC2.

In the slave base station 200, the optical signal transmitted to the optical amplifier 40 via the optical fiber cable FC1 is amplified and then input to the main signal input terminal of the mixer 41. On the other hand, the optical signal transmitted to the optical detector 42 via the optical fiber cable FC2 is detected by the optical detector 42, and is optically / electrically converted into an original local oscillation signal. The signal is input to the local oscillation signal input terminal of the mixer 41 via the amplifier 43. The mixer 41 mixes and multiplies the input optical signal and the local oscillation signal, and passes an electric signal having a frequency (fs + fl) or (fs-fl) resulting from the multiplication mainly through only the frequency (fs + fl). A transmission power amplifier 45 via a band-pass filter 44
Output to The transmission power amplifier 45 power-amplifies the input high frequency signal of the frequency (fs + fl), outputs the amplified high frequency signal to the transmission / reception antenna 50 via the antenna duplexer 46, and directs the high frequency signal to the transmission / reception antenna 51 of the mobile terminal station 300. Radio transmission.

Here, the carrier signal of the frequency fs can be up-converted into a higher frequency signal in the mixer 41 using the local oscillation signal of the frequency fl, and the high frequency signal after the frequency conversion is transmitted to the mobile terminal station 300. Can be used as a transmission radio signal. That is, by appropriately setting the frequency fs of the carrier signal and the frequency fl of the local oscillation signal, the high-frequency signal serving as the transmission radio signal can be easily generated. Mixer 41
Can be composed of, for example, a high-speed photodiode or a phototransistor.

A radio signal of a frequency (fs + fl + fd) transmitted from the transmission / reception antenna 51 of the mobile terminal station 300 to the transmission / reception antenna 50 of the slave base station 200 is received by the transmission / reception antenna 50, and then received by the antenna duplexer 46 and the reception amplifier. The light is input to an optical modulator 49 via a switch 47. Here, the frequency fd is a transmission / reception frequency interval in a wireless channel between the slave base station 200 and the mobile terminal station 300. On the other hand, the optical signal generated by the laser diode 48 is
After being intensity-modulated by the input received radio signal, the modulated optical signal is supplied to the optical fiber cable FC3.
Is transmitted to the optical detector 30 in the main base station 100 via

In the main base station 100, the optical detector 30 detects the transmitted optical signal, that is, performs optical-electrical conversion, and outputs the converted electric signal to the FM demodulator 31.
The FM demodulator 31 performs an FM demodulation process on the input electric signal to demodulate and output a baseband signal.

FIG. 6 shows the slave base station 2 in the first embodiment.
13 is a graph showing an example of a characteristic of an output power level with respect to a local oscillation signal power level when the mixer 41 of No. 00 is configured using a photodiode. The parameter Id in FIG. 6 is the bias current of the transmitting laser diode 10. Each set value at the time of measuring this characteristic is as follows. Frequency fs of carrier signal included in input optical signal = 0.9
GHz, power level P of the electric signal included in the input optical signal
in = 13 dBm, frequency of local oscillation signal fl = 10 G
Hz, the bias voltage Vd of the photodiode used for the receiving mixer 41 is -0.5 V.

As is apparent from FIG. 6, by adjusting the power level of the local oscillation signal output from the amplifier 43, it is possible to set an optimum frequency conversion loss in the mixer 41.

In the optical transmission system for a radio link configured as described above, the master base station 100 and the slave base station 20
0 is connected using the optical fiber cables FC1 to FC3, so that it is possible to eliminate radio wave interference from the power supply system to the wireless line set between the slave base station 200 and the mobile terminal station 300. By appropriately setting the carrier frequency fs and the local oscillation frequency fl on the side of the main base station 100, it is possible to arbitrarily set a radio frequency in a radio line set between the slave base station 200 and the mobile terminal station 300. Therefore, for example, there is an advantage that setting of radio frequencies in a plurality of microcell zones formed by a plurality of slave base stations 200 can be easily performed.

Further, since the slave base station 200 is not provided with a signal processing device for baseband signals, the configuration of the slave base station 200 can be reduced in size and economy, and the slave base station 200 can be installed in a smaller space. A station 200 can be installed. Therefore, it is possible to install a large number of wireless devices for each wireless channel in each microcell zone in a predetermined installation space of the slave base station 200.

Further, the stability of the frequency of the high-frequency signal transmitted from the slave base station 200 depends on the stability of the frequency fs of the carrier signal included in the optical signal input to the mixer 41,
Since it is determined by the stability of the frequency fl of the local oscillation signal, the stability of the oscillation frequency of the carrier signal generator in the FM modulator 13 in the main base station 100 and the stability of the oscillation frequency of the local oscillation signal generator 22 are determined. By increasing the frequency, the stability of the frequency of a high-frequency signal used as a transmission signal in a wireless channel can be easily increased.

In the first embodiment described above, the optical signal output from the laser diode 10 or 20 is transmitted to the optical modulator 1
Although the intensity is modulated by the modulated signal by 1 or 21,
The present invention is not limited to this, and the laser diode 10 or 20
May be directly driven by the modulated signal to perform intensity modulation.

In the first embodiment, the optical signal output from the laser diode 48 is intensity-modulated by the modulated signal by the optical modulator 49. However, the present invention is not limited to this. The intensity modulation may be performed by directly driving the modulated signal.

In the above-described first embodiment, only one slave base station 200 and one mobile terminal station 300 are shown. However, the present invention is not limited to this.
And a plurality of mobile terminal stations 300 may be provided.

<Second Embodiment> FIG. 2 is a block diagram of a wireless link optical transmission system according to a second embodiment of the present invention.

The optical transmission system for a radio link according to the second embodiment is different from the first embodiment in that the slave base station 201 includes a mixer 60 for a received radio signal, a band-pass filter 61 and an amplifier. 62 is further provided. Hereinafter, differences from the first embodiment will be described.

In the slave base station 201, the local oscillation signal output from the amplifier 43 is input to the mixer 41 and also to the local oscillation signal input terminal of the mixer 60. On the other hand, the radio signal of the frequency fr received from the mobile terminal station 300 by the transmitting / receiving antenna 50 is
6 and to the main signal input terminal of the mixer 60 via the receiving amplifier 47. The mixer 60 mixes and multiplies the input received radio signal and the local oscillation signal, and converts an electric signal such as a frequency (fr + fl) or (fr-fl) resulting from the multiplication into mainly the frequency (fr-fl) only. Modulator 4 via a band-pass filter 61 and an amplifier 62
9 is output.

Here, the received radio signal of the frequency fr can be down-converted to a lower high-frequency signal in the mixer 60 using the local oscillation signal of the frequency fl, and the optical signal transmitted to the main base station 100 is It can be used as a modulated signal for modulation. Since the received radio signal can be frequency-converted to a lower frequency,
An optical modulator 49 having a lower maximum driving frequency (the upper limit of the frequency at which the circuit can be driven, the same applies hereinafter) can be used as compared with the first embodiment. Also, the first
In the case where the laser diode 48 is directly driven by the signal to be modulated to perform intensity modulation as in the modification of the embodiment, there is an advantage that a laser diode having a lower maximum driving frequency can be used.

In the second embodiment, a local oscillation signal obtained by optically / electrically converting an optical signal transmitted from the main base station 100 is used for frequency conversion of a received radio signal. Compared to the case where a generator for generating a local oscillation signal is provided in the slave base station 201, the slave base station 20
1 can be simplified, whereby the size and cost of the slave base station 201 can be reduced.

<Third Embodiment> FIG. 3 is a block diagram of a wireless link optical transmission system according to a third embodiment of the present invention.

The optical transmission system for a radio link according to the third embodiment differs from the second embodiment in that the optical signal generated by the laser diode 23 in the main base station 101 is directly and locally converted by the local oscillation signal. The intensity modulation is performed so as to generate a plurality of harmonic components, and the slave base station 202 optically / electrically converts the optical signal including the harmonic components with the optical detector 70, and performs the optical / electrical conversion. The second harmonic component of the local oscillation signal among the plurality of harmonic components of the obtained order is used as the local oscillation signal for up-conversion for generating the high-frequency signal for transmission. The third harmonic component of the local oscillation signal among the harmonic components of the following order is used as the local oscillation signal for down-converting the received radio signal. Hereinafter, differences from the second embodiment will be described.

In the main base station 101, the local oscillation signal of frequency fl generated by the local oscillation signal generator 22 is input to the laser diode 23, and the optical signal generated by the laser diode 23 is converted into the nonlinear signal of the laser diode 23. Intensity modulation is performed on the input local oscillation signal so that a harmonic is generated using the electric-optical conversion characteristic, and the laser diode 23 outputs the intensity-modulated optical signal to the optical fiber cable FC2, and The signal is transmitted to the optical detector 70 of the slave base station 202. This optical signal includes, in addition to the fundamental wave of the local oscillation signal, harmonic components such as the first harmonic, the second harmonic, and the third harmonic.

In the slave base station 202, the optical detector 70
Converts the optical signal transmitted through the optical fiber cable FC2 into an electric signal including a fundamental wave and a harmonic component of a local oscillation signal, and then converts the optical signal into band-pass filters 72 and 73 through an amplifier 71. Output. After the band-pass filter 72 mainly filters only the second harmonic signal of the local oscillation signal among the input electric signals, the mixer 41
Output to the local oscillation signal input terminal. The mixer 41 mixes and multiplies the input optical signal and the local oscillation signal, and passes an electric signal such as a frequency (fs + 2fl) or (fs-2fl) resulting from the multiplication mainly through only the frequency (fs + 2fl). The signal is output to the transmission power amplifier 45 via the band-pass filter 44. The transmission power amplifier 45 power-amplifies the input high-frequency signal of the frequency (fs + 2fl), outputs the amplified high-frequency signal to the transmission / reception antenna 50 via the antenna duplexer 46, and directs the high-frequency signal to the transmission / reception antenna 51 of the mobile terminal station 300. Radio transmission.

The band-pass filter 73 mainly filters only the third harmonic signal of the local oscillation signal among the input electric signals, and outputs the resultant signal to the local oscillation signal input terminal of the mixer 60. The mixer 60 mixes and multiplies the received radio signal and the local oscillation signal, and converts the multiplied electric signals such as the frequencies (fr + 3fl) and (fr-3fl) into mainly the frequency (fr-3fl). Is output to an optical modulator 49 via a band-pass filter 61 and an amplifier 62 that pass the signal.

In the third embodiment, the harmonic component of the local oscillation signal generated by the main base station 101 is used as the local oscillation signal in each of the mixers 41 and 60 of the slave base station 202. Slave base station 202 and mobile terminal station 30
The degree of freedom in setting the transmission / reception frequency of the wireless line between 0 and 0 can be increased as compared with the conventional example.

In the third embodiment, the slave base station 2
02 uses the second harmonic of the local oscillation signal as its local oscillation signal in the mixer 41, and the mixer 60 uses the third harmonic of the local oscillation signal as its local oscillation signal. However, the harmonic signal of any order of the local oscillation signal may be used as the local oscillation signal in each of the mixers 41 and 60.

<Fourth Embodiment> FIG. 4 is a block diagram of a wireless link optical transmission system according to a fourth embodiment of the present invention.

In the optical transmission system for a wireless link according to the fourth embodiment, in the slave base station 203, the optical signal transmitted via the optical fiber cable FC1 is optically / electrically converted by the optical detector 80 to the baseband. The FM signal is extracted, and the baseband FM signal is input to the mixer 82 as a local oscillation signal. On the other hand, the optical signal transmitted via the optical fiber cable FC2 and containing the fundamental wave component and the harmonic component of the local oscillation signal is mixed. Input to the device 82 as a main signal,
The optical signal including the fundamental wave component and the harmonic component of the transmitted local oscillation signal is subjected to optical / electrical conversion by the optical detector 84 to extract the fundamental wave component and the harmonic component of the local oscillation signal, and the second harmonic The wave component is input to the mixer 60 as a local oscillation signal. Hereinafter, differences from the third embodiment will be described. In addition, the main base station 1
01 has the same configuration as in the third embodiment.

As shown in FIG. 4, in the slave base station 203, the optical signal transmitted from the optical modulator 11 of the master base station 101 via the optical fiber cable FC1 is input to the optical detector 80. The optical detector 80 converts the transmitted optical signal into an optical signal
The baseband FM signal is extracted by electrical conversion, and the baseband FM signal is input to the mixer 82 via the amplifier 81 as a local oscillation signal.

On the other hand, the optical signal transmitted from the laser diode 23 of the main base station 101 via the optical fiber cable FC2 and including the fundamental wave component and the harmonic wave component of the local oscillation signal is input to the optical amplifier 83 and amplified. , And 82 as a main signal and to a photodetector 84. The mixer 82 mixes and multiplies the input optical signal and the optical-electrically converted baseband FM signal signal, and calculates the multiplication results of the frequencies (fs + fl) and (fs + 2f).
l), (fs + 3fl), (fs-fl), (fs-2)
An electric signal such as (fl) and (fs-3fl) is output to the transmission power amplifier 45 through a band-pass filter 44 that mainly passes only the frequency (fs + 2fl). The mixer 82 can be composed of a photodiode, a phototransistor, or the like. The transmission power amplifier 45 power-amplifies the input high-frequency signal of the frequency (fs + 2fl), outputs the amplified high-frequency signal to the transmission / reception antenna 50 via the antenna duplexer 46, and directs the high-frequency signal to the transmission / reception antenna 51 of the mobile terminal station 300. Radio transmission.

The optical detector 84 performs optical-to-electrical conversion on the input optical signal, extracts the fundamental wave component and the harmonic wave component of the local oscillation signal, and outputs the same to the band-pass filter 85. The band-pass filter 85 mainly filters only the third harmonic component of the local oscillation signal among the input electric signals, and inputs the resultant signal to the mixer 60 as the local oscillation signal. The mixer 60 mixes and multiplies the input received radio signal and the local oscillation signal, and calculates a frequency (fr + 3fl),
Band-pass filter 6 that passes an electric signal such as (fr-3fl) mainly through only the frequency (fr-3fl)
1 and output to the optical modulator 49 via the amplifier 62.

FIG. 7 shows a slave base station 2 according to the fourth embodiment.
13 is a graph illustrating an example of characteristics of an output power level with respect to a power level of an electric signal included in an input optical signal when the mixer 82 of No. 03 is configured using a photodiode. The parameters in FIG. 7 are frequency components output from the mixer 82. Each set value at the time of measuring this characteristic is as follows.

The frequency fl = 4 GHz of the fundamental component of the local oscillation signal included in the input optical signal, the local oscillation signal generator 2
2, the power level Pl of the local oscillation signal input to the transmission laser diode 23 from Pl = 10 dBm, the bias current Id of the transmission laser diode 23 = 25 mA, the carrier signal frequency fs = 0.9 GHz, and the reception mixer 82. Photodiode bias voltage Vd = -1.0
V.

As is apparent from FIG. 7, by adjusting the power level of the optical signal of the main signal output from the amplifier 83, it is possible to set the optimum frequency conversion loss in the mixer 82.

In the above fourth embodiment, the slave base station 2
03 in the band-pass filter 44 (fs + 2fl)
The present invention is not limited to this, and the present invention is not limited to this. The high-frequency signal obtained by mixing the carrier signal carrying the baseband FM signal with one harmonic component of any order of the local oscillation signal is used. The signal may be band-filtered and transmitted wirelessly.

In the above fourth embodiment, the slave base station 2
In the bandpass filter 85 of No. 03, the third harmonic signal of the frequency 3fl is band-filtered. However, the present invention is not limited to this, and one harmonic component of any order of the local oscillation signal is band-filtered. And output to the mixer 60.

<Fifth Embodiment> FIG. 5 is a block diagram of a wireless link optical transmission system according to a fifth embodiment of the present invention.

The optical transmission system for a radio link according to the fifth embodiment comprises a main base station 102 and three slave base stations 2 provided at predetermined distances from the main base station 102, respectively.
00a, 200b, and 200c, nine optical fiber cables FC1 to FC9 for connecting the main base station 102 to each of the slave base stations 200a, 200b, and 200c, and a wireless line connected to the slave base station 200a. A mobile terminal station 300a connected to the slave base station 200b via a wireless link, and a mobile terminal station 300c connected to the slave base station 200c via a wireless link.

In the main base station 102, the laser diodes 10a, 10b, and 10c generate optical signals having first to third wavelengths different from each other and output the optical signals to the optical modulators 11a, 11b, and 11c, respectively. On the other hand, each baseband FM signal obtained by FM-modulating a predetermined carrier signal with each different baseband signal is applied to an optical modulator 11.
a, 11b, and 11c. The optical signal input to the optical modulator 11a is intensity-modulated by the input baseband FM signal and then output to the optical synthesizer 90, and the optical signal input to the optical modulator 11b is output to the input baseband FM signal. After being intensity-modulated with the signal, the optical signal is output to the optical combiner 90, and the optical signal input to the optical modulator 11c is intensity-modulated with the input baseband FM signal.
Output to 0. Next, the photosynthesizer 90 outputs the input 3
After wavelength division multiplexing of the optical signals, the multiplexed optical signal is transmitted to the optical branch circuit 93a provided in the slave base station 200a via the optical fiber cable FC1.

The laser diodes 20a, 20a
b and 20c generate optical signals having fourth to sixth wavelengths different from each other, and respectively generate optical modulators 21a, 21b,
21c. On the other hand, each local oscillation signal generator 22
a, 22b and 22c respectively generate local oscillation signals and output them to the optical modulators 21a, 21b and 21c. The optical signal input to the optical modulator 21a is output to the optical combiner 91 after being intensity-modulated by the input local oscillation signal, and the optical signal input to the optical modulator 21b is the input local oscillation signal. The intensity-modulated light is output to the optical combiner 91, and the optical signal input to the optical modulator 21c is intensity-modulated by the input local oscillation signal and output to the optical combiner 91. Next, the optical combiner 91 wavelength-multiplexes and combines the three input optical signals, and then transmits the multiplexed optical signal to the optical branch circuit 94a provided in the slave base station 200a via the optical fiber cable FC2.

In the slave base station 200a, the optical branching circuit 9
3a selectively filters an optical signal having a first wavelength out of the input multiplexed optical signals and outputs the filtered optical signal to a slave base station 200a, and also converts each optical signal having a second and a third wavelength into an optical fiber cable FC4. To the optical branch circuit 93b provided in the slave base station 200b. Also, the optical branch circuit 94
a selectively filters an optical signal having a fourth wavelength out of the input multiplexed optical signals and outputs the filtered optical signal to the slave base station 200a, and outputs each optical signal having the fifth and sixth wavelengths to the optical fiber cable FC5. To the optical branch circuit 94b provided in the slave base station 200b. The slave base station 200a receives the optical signal from the slave base station 20a of the first embodiment.
The same processing as 0 is performed. Here, a radio channel is set between the transmission / reception antenna 50a of the slave base station 200a and the transmission / reception antenna 51a of the mobile terminal station 300a as in the first embodiment. The optical signal including the information of the radio signal received by the slave base station 200a is output to the optical combiner 95a. The optical combiner 95a wavelength-multiplexes and combines the optical signal transmitted from the optical combiner 95b via the optical fiber cable FC6 and the optical signal output from the slave base station 200a as described later in detail, and combines the multiplexed signals. The optical signal is transmitted to the optical distributor 92 of the main base station 102 via the optical fiber cable FC3.

In the slave base station 200b, the optical branching circuit 9
3b selects and filters the optical signal having the second wavelength out of the input multiplexed optical signals and outputs the optical signal to the slave base station 200b, and also filters the optical signal having the third wavelength via the optical fiber cable FC7. It transmits to base station 200c. The optical branching circuit 94b selectively filters the optical signal having the fifth wavelength out of the input multiplexed optical signals and outputs it to the slave base station 200b, and also converts the optical signal having the sixth wavelength into an optical fiber cable. The data is transmitted to the slave base station 200c via the FC8. The slave base station 200b performs the same processing as that of the slave base station 200 of the first embodiment for each input optical signal.
Here, the transmitting / receiving antenna 50b of the slave base station 200b,
A wireless line is set between the transmitting / receiving antenna 51b of the mobile terminal station 300b and the transmitting / receiving antenna 51b as in the first embodiment. Slave base station 2
The optical signal including the information of the radio signal received at 00b is output to the optical combiner 95b. The optical combiner 95b is connected to the optical fiber cable F from the base station 200c as described in detail later.
The optical signal transmitted via C9 and the optical signal output from the slave base station 200b are wavelength-multiplexed and combined, and the combined multiplexed optical signal is transmitted to the optical combiner 95a via the optical fiber cable FC6.

The slave base station 200c performs the same processing on each transmitted optical signal as the slave base station 200 of the first embodiment. Here, the transmitting / receiving antenna 5 of the slave base station 200c
A wireless channel is set between the transmission and reception antenna 0c and the transmitting / receiving antenna 51c of the mobile terminal station 300c in the same manner as in the first embodiment. The optical signal including the information of the radio signal received by the slave base station 200c is transmitted to the optical combiner 95b via the optical fiber cable FC9.
Is transmitted to

In the main base station 100, the optical distributor 92 distributes each transmitted optical signal for each wavelength, and
a, 30b, and 30c. Here, the slave base station 20
The optical signal output from Oa and transmitted is transmitted to the optical detector 3
0a, the optical signal output from the slave base station 200b and transmitted is output to the optical detector 30b, and the optical signal output from the slave base station 200c and transmitted is output to the optical detector 30c. You. The optical detector 30a detects the input optical signal, that is, performs optical-electrical conversion, and outputs the converted electric signal to the FM demodulator 31a. Then
The FM demodulator 31a performs the FM demodulation on the input electric signal.
A demodulation process is performed to demodulate and output a baseband signal. The optical detector 30b detects the input optical signal, that is, performs optical-electrical conversion, and outputs the converted electrical signal to the FM demodulator 31b. Next, the FM demodulator 31
b performs FM demodulation on the input electric signal to demodulate and output a baseband signal. Further, the optical detector 30c detects the input optical signal, that is, performs optical-electrical conversion, and converts the converted electric signal into an FM demodulator 3c.
1c. Next, the FM demodulator 31c performs an FM demodulation process on the input electric signal to demodulate and output a baseband signal.

In the above fifth embodiment, when each of the slave base stations 200a, 200b, 200c uses one set of transmission / reception frequencies, a plurality of baseband signals are transmitted in a time division multiplexed manner. Signal may be used. In addition, each slave base station 200a, 20
When a plurality of sets of transmission and reception frequencies are used in Ob and 200c, the baseband FM signal to be transmitted may be a signal obtained by frequency-multiplexing a plurality of baseband signals.

In the above fifth embodiment, the slave base station 2
Although 00a, 200b, and 200c have the same configuration as the slave base station 200 of the first embodiment, the present invention is not limited to this, and the slave base station of the second, third, or fourth embodiment is not limited thereto. Station 20
You may comprise so that it may have the structure similar to 1,202 or 203.

In the above fifth embodiment, each optical signal generated by each of the laser diodes 10a, 10b and 10c is intensity-modulated by each of the local oscillation signals in each of the optical modulators 11a, 11b and 11c. The present invention is not limited to this,
Each local oscillation signal is transmitted to the laser diodes 10a, 10b, 1
0c may be directly input to perform intensity modulation. In the above fifth embodiment, each optical signal generated by each of the laser diodes 20a, 20b, and 20c is intensity-modulated by each of the local oscillation signals in each of the optical modulators 21a, 21b, and 21c. The present invention is not limited to this, and the local oscillation signals may be input to the laser diodes 20a, 20b, and 20c to directly perform intensity modulation.

<Other Embodiments> In the first to fourth embodiments, the FM modulator 13 is used. However, the present invention is not limited to this, and modulation of another modulation method such as an FSK modulator is used. A vessel may be used.

In the above first to fourth embodiments, each optical signal transmitted through the optical fiber cables FC1 and FC2 may be wavelength-multiplexed and transmitted using one optical fiber cable. In addition, the optical fiber cables FC1,
Each optical signal transmitted through FC2 and FC3 may be wavelength-multiplexed and transmitted using one optical fiber cable.

In the first to fourth embodiments, the baseband signal is generated by the baseband signal generator 12 in the main base station and input to the FM modulator 13, but the present invention is not limited to this. Instead, a baseband signal generated by an external device may be directly input to the FM modulator 13.

[0079]

As described above in detail, according to the optical transmission system for a radio link according to the present invention, a main base station, a sub base station provided at a predetermined distance from the main base station,
An optical transmission system for a radio link, comprising first and second optical transmission lines connecting said master base station and said slave base station, wherein said master base station converts a carrier signal into a first information signal. Modulating means for modulating the modulated signal to output a modulated signal; and converting the modulated signal output from the modulating means into a light signal and outputting a first optical signal including the modulated signal to the first optical transmission line. First electrical-optical conversion means, and second electrical-optical conversion means for performing electrical-optical conversion of the local oscillation signal and outputting a second optical signal including the local oscillation signal to the second optical transmission line. Wherein the slave base station optically / electrically converts a second optical signal transmitted from the second electrical / optical conversion means via the second optical transmission line, and converts the local oscillation signal to The first to output
In response to a first optical signal transmitted from the first electrical-to-optical converter via the first optical transmission line, and included in the first optical signal. Frequency conversion means for converting the frequency of the modulated signal into a radio signal using the local oscillation signal output from the first optical / electrical conversion means; Transmitting means for wirelessly transmitting to the terminal station of the base station.

Therefore, since the main base station and the slave base station are connected by using the first and second optical transmission lines, the power supply system connects the slave base station and the terminal station with each other. The radio wave interference to the wireless line set by the above can be eliminated. By appropriately setting the carrier frequency and the local oscillation frequency of the first information signal on the main base station side, the radio frequency in the radio line set between the slave base station and the terminal station can be set to an arbitrary value. Therefore, there is an advantage that the radio frequency can be easily set in a plurality of microcell zones formed by a plurality of slave base stations, for example.

Further, since the slave base station is not provided with a signal processing device for the information signal, the configuration of the slave base station can be reduced in size and economy, and the slave base station can be installed in a smaller space. Can be installed. Therefore, it is possible to install a large number of wireless devices for each wireless channel in each microcell zone in a predetermined installation space of the slave base station.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical transmission system for a wireless link according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an optical transmission system for a wireless link according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a wireless link optical transmission system according to a third embodiment of the present invention.

FIG. 4 is a block diagram of a wireless link optical transmission system according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram of an optical transmission system for a wireless link according to a fifth embodiment of the present invention.

FIG. 6 is a graph illustrating a characteristic example of an output power level with respect to a local oscillation signal power level when a mixer of a slave base station according to the first embodiment is configured using a photodiode.

FIG. 7 is a graph showing a characteristic example of an output power level with respect to a power level of an electric signal included in an input optical signal when a mixer of a slave base station in the fourth embodiment is configured using a photodiode. .

[Explanation of symbols]

 10, 20, 23, 48 ... laser diode, 11, 21, 49 ... optical modulator, 12 ... baseband signal generator, 13 ... FM modulator, 22 ... local oscillation signal generator, 30, 42, 70, 84 ... Optical detector, 31 ... FM demodulator, 41,60 ... Mixer, 44,61,72,73,85 ... Bandpass filter, 45 ... Transmission power amplifier, 47 ... Receiving amplifier, 50,51 ... Transceiving antenna, 100, 101, 102: master base station, 200, 201, 202, 203: slave base station, 300: mobile terminal station, FC1 to FC3: optical fiber cable.

Continuation of the front page (72) Inventor Yoshiaki Kamiya Kyoto, Soraku-gun, Seika-cho, 5F, Inani, 5F, Sanpira, ATR Optical Co., Ltd. Inside the Radio Communication Research Laboratory (56) References JP-A-2-9236 (JP, A) JP-A-62-274934 (JP, A) JP-A-58-19512 (JP, U) Hiroyo Ogawa "Optical fiber link millimeter-wave personal communication system" IEICE Autumn National Convention B-736 (1990)

Claims (7)

(57) [Claims] 1. A main base station, a sub base station provided at a predetermined distance from the main base station, and first and second optical transmissions connecting the main base station and the sub base station. An optical transmission system for a radio link, comprising: a transmission line; a modulation unit that modulates a carrier signal with a first information signal to output a modulation signal; and a modulation output from the modulation unit. A first electro-optical converter for converting a signal into an optical signal and outputting a first optical signal including the modulation signal to the first optical transmission line; Outputting a second optical signal including a local oscillation signal to the second optical transmission line;
Wherein the slave base station optically / electrically converts a second optical signal transmitted from the second electric / optical conversion means via the second optical transmission line. First optical-to-electrical conversion means for outputting the local oscillation signal, and in response to a first optical signal transmitted from the first electric-to-optical conversion means via the first optical transmission line. , The first
Frequency converting means for converting the modulated signal included in the optical signal into a radio signal using the local oscillation signal output from the first optical-to-electrical converting means; Transmission means for wirelessly transmitting the wireless signal to the terminal station of the slave base station. 2. The slave base station further comprises: receiving means for receiving a wireless signal including a second information signal wirelessly transmitted from the terminal station; and electrical-optical conversion of the wireless signal received by the receiving means. And outputs a third optical signal to a third optical transmission line.
The main base station further comprises: a third optical signal transmitted from the third electrical / optical conversion unit via the third optical transmission line; Second optical-to-electrical conversion means for converting and outputting the received wireless signal; and demodulating the received wireless signal output from the second optical-to-electrical conversion means for obtaining the second information. The optical transmission system for a wireless link according to claim 1, further comprising demodulation means for outputting a signal. 3. A main base station, a sub base station provided at a predetermined distance from the main base station, and first, second, and third connecting the main base station and the sub base station. An optical transmission system for a radio link, comprising: an optical transmission line, wherein the main base station modulates a carrier signal with a first information signal and outputs a modulation signal; First electrical-optical conversion means for performing electrical-optical conversion on the modulated signal to be output and outputting a first optical signal including the modulated signal to the first optical transmission line; and electrical-optical conversion of the local oscillation signal And outputting a second optical signal including the local oscillation signal to the second optical transmission line.
Wherein the slave base station optically / electrically converts a second optical signal transmitted from the second electric / optical conversion means via the second optical transmission line. First optical-to-electrical conversion means for outputting the local oscillation signal, and in response to a first optical signal transmitted from the first electric-to-optical conversion means via the first optical transmission line. , The first
First frequency conversion means for frequency-converting the modulated signal included in the optical signal into a radio signal using the local oscillation signal output from the first optical-electrical conversion means; and the first frequency Transmitting means for wirelessly transmitting the wireless signal frequency-converted by the converting means to the terminal station of the slave base station; receiving means for receiving a wireless signal including a second information signal wirelessly transmitted from the terminal station; The wireless signal received by the receiving means is transmitted to the first
Frequency conversion means for converting the frequency of the intermediate frequency signal into an intermediate frequency signal using a local oscillation signal output from the optical / electrical conversion means; Convert the third optical signal to the third optical signal.
And a third electric / optical conversion means for outputting to the optical transmission line. The main base station further comprises: a third electric / optical conversion means for transmitting the electric power from the third electric / optical conversion means via the third optical transmission line. A second optical-to-electrical converter for optically / electrically converting the third optical signal to output the intermediate frequency signal; and a demodulator for demodulating the intermediate frequency signal output from the second optical / electrical converter. An optical transmission system for a wireless link, comprising: a demodulation unit that outputs the second information signal. 4. A main base station, a sub base station provided at a predetermined distance from the main base station, and first, second, and third connecting the main base station and the sub base station. An optical transmission system for a radio link, comprising: an optical transmission line, wherein the main base station modulates a carrier signal with a first information signal and outputs a modulation signal; A first electrical-optical conversion means for performing electrical-optical conversion of the modulated signal to be output and outputting a first optical signal including the modulated signal to the first optical transmission line; And converting the local oscillation signal from light to light so as to generate a fundamental wave component and at least one harmonic component of the local oscillation signal using the non-linear electric / light conversion characteristics. Optical signal comprising a component and at least one harmonic component A second electrical / optical converter for outputting to the second optical transmission line, wherein the slave base station is transmitted from the second electrical / optical converter via the second optical transmission line. First optical-to-electrical conversion means for performing optical-to-electrical conversion of the second optical signal and outputting a fundamental wave component and at least one harmonic component of the local oscillation signal; and the first optical-to-electrical conversion means First filtering means for band-filtering a predetermined one of a fundamental component and at least one harmonic component of the local oscillation signal output from the first and second harmonic components; In response to the first optical signal transmitted from the conversion means via the first optical transmission line, the first optical signal
A first frequency converter for frequency-converting the modulated signal included in the optical signal into a radio signal using the harmonic component band-filtered by the first filter; Transmitting means for wirelessly transmitting a radio signal frequency-converted by the converting means to the terminal station of the slave base station; and a fundamental wave component of the local oscillation signal output from the first optical / electrical converting means and at least one of Second filtering means for band-filtering a predetermined one of the harmonic components, and receiving means for receiving a wireless signal including a second information signal wirelessly transmitted from the terminal station. Transmitting the radio signal received by the receiving means to the second
Second frequency conversion means for converting the frequency of the intermediate frequency signal into an intermediate frequency signal using the harmonic component band-filtered by the second frequency conversion means; Optically converts the third optical signal into the third optical signal.
And a third electric / optical conversion means for outputting to the optical transmission line. The main base station further comprises: a third electric / optical conversion means for transmitting the electric power from the third electric / optical conversion means via the third optical transmission line. A second optical-to-electrical converter for optically / electrically converting the third optical signal to output the intermediate frequency signal; and a demodulator for demodulating the intermediate frequency signal output from the second optical / electrical converter. An optical transmission system for a wireless link, comprising: a demodulation unit that outputs the second information signal. 5. A main base station, a sub base station provided at a predetermined distance from the main base station, and first, second, and third connecting the main base station and the sub base station. An optical transmission system for a radio link, comprising: an optical transmission line, wherein the main base station modulates a carrier signal with a first information signal and outputs a modulation signal; A first electrical-optical conversion means for performing electrical-optical conversion of the modulated signal to be output and outputting a first optical signal including the modulated signal to the first optical transmission line; And converting the local oscillation signal from light to light so as to generate a fundamental wave component and at least one harmonic component of the local oscillation signal using the non-linear electric / light conversion characteristics. Optical signal comprising a component and at least one harmonic component A second electrical / optical conversion means for outputting to the second optical transmission line, wherein the slave base station is transmitted from the first electrical / optical conversion means via the first optical transmission line. A first optical-to-electrical conversion unit that performs optical-to-electrical conversion on the first optical signal and outputs the modulated signal, and transmits the second optical-to-optical conversion unit via the second optical transmission line. The first optical signal in response to the second optical signal
Converting the modulated signal output from the optical-to-electrical conversion means into a radio signal using a predetermined harmonic component of a fundamental component and at least one harmonic component included in the optical signal. (1) frequency converting means, transmitting means for wirelessly transmitting a radio signal frequency-converted by the first frequency converting means to a terminal station of the slave base station, and Third optical-electrical conversion means for performing optical-electrical conversion of the second optical signal transmitted via the optical transmission line and outputting a fundamental wave component and at least one harmonic component of the local oscillation signal; A filtering means for band-filtering one predetermined harmonic component of the fundamental component and at least one harmonic component of the local oscillation signal output from the third optical / electrical conversion means; From terminal station Receiving means for receiving a wireless signal including a second information signal wirelessly transmitted; and an intermediate frequency using the harmonic component band-filtered by the filtering means for converting the wireless signal received by the receiving means. A second frequency converting means for converting the frequency into a signal; and an electrical / optical conversion of the intermediate frequency signal frequency-converted by the second frequency converting means to convert the third optical signal into the third optical signal.
And a third electric / optical conversion means for outputting to the optical transmission line. The main base station further comprises: a third electric / optical conversion means for transmitting the electric power from the third electric / optical conversion means via the third optical transmission line. A second optical-to-electrical converter for optically / electrically converting a third optical signal to output the intermediate frequency signal; and a demodulator for demodulating the intermediate frequency signal output from the second optical / electrical converter. An optical transmission system for a wireless link, comprising: a demodulation unit that outputs the second information signal. 6. The wireless device according to claim 1, wherein the first and second optical signals are wavelength-multiplexed and transmitted via one optical transmission line. Optical transmission system for link. 7. The method according to claim 2, wherein the first, second and third optical signals are wavelength-division multiplexed and transmitted via one optical transmission line. Optical transmission system for wireless links.