JPH0824283B2 - Communications system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a communication system that performs bidirectional communication using an optical multiplex signal.

[Prior Art] In conventional communication systems, particularly in the field of LAN (local area network), a transmission method such as a baseband type, a broadband type, or an optical fiber type is used. Various products such as communication devices of different systems have been announced. Also, CATV has been put to practical use for video signal transmission.

On the other hand, in terms of the switching function corresponding to these various transmission methods, the electronic exchange is still the mainstream, and the current situation is that the research of the optical exchange is actively conducted with the spread of optical communication.

[Problems to be Solved by the Invention] The above conventional example has the following problems.

(1) When bidirectional transmission of video is performed using CATV, the line amplifier becomes very expensive and the channel allocation becomes strict. Also, it is difficult for specific subscribers to communicate with each other.

(2) When exchange is performed using an electronic exchange, quality deterioration due to crosstalk occurs during transmission of high frequency signals. Further, in order to perform an arbitrary N-to-N exchange, an N × N circuit scale is required, and when the subscriber system N increases, the circuit scale increases in proportion to the square of N.

(3) Research on optical switchboards has been actively conducted, but it has not yet reached the practical stage.

(4) It is difficult for existing LANs to cope with the increase in transmission capacity.

The present invention has been made in view of the above-mentioned conventional example, and it is possible to independently perform communication between nodes having a plurality of terminals and communication between a plurality of terminals in a node, and also to attenuate communication between nodes. It is an object of the present invention to provide a communication system capable of transmitting and receiving with less communication.

[Means for Solving Problems] In order to achieve the above object, the communication system of the present invention has the following configuration. That is, in a communication system having a plurality of terminals connected to a plurality of nodes, each of the plurality of nodes is connected via an optical cable, the terminal modulates transmission data into a signal of a first frequency, Outputting means for converting into an optical signal of a predetermined wavelength and outputting to the optical cable, inputting means for inputting an optical signal of a predetermined wavelength from the wavelength-multiplexed optical signal from the optical cable, and the predetermined inputting by the inputting means A conversion means for converting an optical signal of a wavelength into an electric signal; and a reception means for receiving an electric signal having a second frequency among the electric signals converted by the conversion means, wherein the node is connected to the optical cable. A means for multiplexing optical signals having a plurality of frequencies and a plurality of wavelengths output from a plurality of terminals, and a method of frequency tuning and wavelength selection at the transmitting side terminal and the receiving side terminal. At least, there is provided control means for instructing either one, and frequency conversion means for converting the frequency of the signal transmitted from the own node to another node.

[Operation] In the above configuration, the terminal in the node modulates the transmission data into the signal of the first frequency, converts it into the optical signal of the predetermined wavelength and outputs it to the optical cable, and the wavelength-multiplexed optical signal from the optical cable is used. An optical signal having a predetermined wavelength is input from the signal, the input optical signal having the predetermined wavelength is converted into an electric signal, and an electric signal having a second frequency is received from the electric signal. Further, each node multiplexes an optical signal having a plurality of frequencies and a plurality of wavelengths output from a plurality of terminals on an optical cable, and controls at least frequency tuning and wavelength selection at the transmitting side terminal and the receiving side terminal by the control means. One of them is instructed to operate so as to convert the frequency of a signal transmitted from its own node to another node.

[Embodiment] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[Description of Communication System (FIG. 1)] FIG. 1 is a diagram showing the basic configuration of the communication system of the first embodiment.

FIG. 2 is a diagram showing a configuration of an optical star coupler node corresponding to each node (node 1 to node 3) of FIG. 1 which is a basic unit in the configuration of this system. First, regarding the configuration of the node of FIG. Explaining this, in each node, each terminal 12 (12a to 12c) is connected to the corresponding interface unit 11 (11a to 11c), and each interface unit 11 is connected via the optical fiber cable 16 (16a to 16c). It is connected to a corresponding pair of input / output ports of the star coupler 10. A remote bridge 14 for transmitting data between a controller 13 and a node at a long distance is connected to a specific input / output port of the optical star coupler 10, and the remote bridge 14 is connected to a controller via a bus 15. It is connected to 13 and controlled by the controller 13.

Each node (node 1 to node 3) in FIG. 1 corresponds to the node shown in FIG. 2, and the distance between the remote bridges (14-1 to 14-6) provided in each node. The communication line 17 for distance is, for example, NTT special reselection or optical fiber line, the control line 18 between the controllers is composed of a telephone line, etc., and the controllers send and receive control signals to each other via the control line 18. The control between each node is executed.

With this configuration, it is possible to communicate via a plurality of nodes. At this time, the combination of the remote bridge 14 and the controller 13 causes the entire node to function as a repeater having a relay function.

The optical star coupler 10 has n fibers connected to the input / output ports, and a pair of input / output lines of the corresponding ports are connected to the interface unit 11 or the controller 13 and the remote bridge 14. At this time, a signal in which optical signals having different wavelengths and frequencies of all input ports are superimposed is output to the signal line of any output port.
Each interface section selectively receives this signal at a desired frequency and wavelength.

At least one controller 13 is arranged in the node, and is connected to the interface section 11 via the optical star coupler 10 and to the remote bridge 14 by a bus line 15. Line status in the node, line "connection",
In addition to "off" and exchange functions, all controls such as billing management are performed. At the same time, in long-distance node-to-node communication, the controllers are connected via a public telephone line or the like via a modem, so that frequency allocation of the line channels or mutual control of wavelengths of optical signals to be used can be performed by handshake.

[Explanation of Interface Unit (FIG. 3)] FIG. 3 is a diagram showing the structure and connection of the interface unit 11, and the same parts as those in FIGS. 1 and 2 are designated by the same symbols.

The transmission data 20 from the terminal 12 is modulated by the modulator 21 at the unique carrier frequency assigned to the own channel by the controller 13. The frequency instruction to the modulator 21 is given by the instruction from the CPU 22. The multiplexer 23 is the modulator 2
The modulated signal 24 from 1 and the control signal of the CPU 22 (fault check, in-use check, light wavelength instruction, tuner control, ringing signal, etc.) are combined and output. The electric-optical (E / O) converter 80 converts the electric signal from the multiplexer 23 into a predetermined wavelength or CP.
It is converted to an optical signal of the wavelength designated by U22 and sent to the optical star coupler 10.

On the other hand, of the optical signals 83 input from the optical star coupler 10, an optical signal having a predetermined wavelength in the optical demultiplexing circuit 84 or
Only the optical signal of the wavelength designated by the CPU 22 is input.
This optical signal is transmitted data from each terminal and controller 13
Control signals (fault check, in-use check, optical wavelength indication, tuner control, ringing signal, etc.). The optical signal input from the optical demultiplexing circuit 84 is converted into an electrical signal by the optical-electrical (O / E) converter 82, and separated by the demultiplexer 26 composed of a band filter, a band elimination filter, or the like. It is sent to the CPU 22 and the variable tuner section 27. The variable tuner 27 tunes the input signal at the frequency instructed by the CPU 22, demodulates the modulated input signal, and outputs it as received data 28 to the terminal 12.

With the above configuration, when the terminal 12 wants to communicate with another terminal in the same node, the bus 29 specifies the terminal with which the CPU 22 wants to communicate. This causes the CPU 22 to pass through the multiplexer 23,
The electric-optical (E / O) converter 80 converts the optical signal of a predetermined wavelength into an optical signal of the other party's terminal and transmits the other party's designation data (control signal) to the controller 13 via the optical star coupler 10.

When the controller 13 receives the above-mentioned control signal, as a response, the receiving frequency and the receiving light wavelength of the partner terminal and the transmitting frequency and the sending light wavelength of the partner terminal are optical star couplers.
Output to 10. The interface circuit 11 inputs the optical signal of the wavelength selected by the optical demultiplexing circuit 84 among the optical signals from the optical star coupler 10 and converts the optical signal into an electrical signal by the optical-electrical converter 82. This electric signal is demultiplexed by the demultiplexer 26, and the control signal is input to the CPU 22.

When the CPU 22 recognizes the used frequency (transmission / reception frequency) of the other terminal based on the signal of the demultiplexer 26 and the wavelength of the optical signal to be used, the modulator 21 and the variable tuner 27 respectively receive the reception frequency and the transmission of the other terminal. Electricity according to frequency
The wavelength of the optical signal output from the optical converter 80 is indicated, and the optical demultiplexing circuit 84
The input wavelength of is matched with the output wavelength of the other terminal.

The tuning of this frequency may be performed by the other terminal matching the frequency of the communication requesting terminal. Alternatively, the transmission frequency from each terminal may be fixed, and the tuning frequency of the variable tuner 27 on the receiving side may be adjusted to the transmission frequency of the other terminal.

Similarly, the matching of the wavelengths of the optical signals between the terminals may be performed so that the other terminal matches the wavelength of the optical signal input / output by the communication requesting terminal, and the wavelength of the optical signal output by each terminal is fixed. Alternatively, the demultiplexing wavelength of the optical demultiplexing circuit 84 on the receiving side may be matched with the wavelength of the optical signal on the transmitting side.

Further, if there is an unused frequency band and wavelength band in the frequency band and wavelength light that can be used in this communication network (node), the controller 4 allocates the frequency band and wavelength band to the communication requesting terminal. good.

By doing so, it is possible to easily add or reduce terminals in the communication system.

[Explanation of Controller Operation (FIGS. 1 to 4)] FIG. 4 is a flow chart of pre-processing of communication by the controller 13, and this program is started by communication request from the interface section 11.

First, in step S1, from the interface unit 11 of the terminal 12,
When the terminal 12 designates the partner terminal which desires to communicate, the process proceeds to step S2, and at step S2, a communication request is sent to the interface section of the partner terminal and the operation of the partner terminal is checked. In step S3, check whether the other terminal can communicate, and if communication is possible, proceed to step S4
The communication terminal 12 is informed to the communication terminal 12 via the bus 29 that the communication is not possible, and the processing ends.

If the other terminal can communicate with step S3, step
In step S5, the frequency band not currently used in the communication network and the wavelength of the optical signal are checked, and in step S6, the terminal 12 and the partner terminal are instructed. According to this instruction, the interface unit of each terminal changes either or both of the transmission and reception frequencies, and also changes either or both of the transmission and reception wavelengths of the optical signal for communication. If the transmission frequency or the output light wavelength of each terminal is fixed, the controller 4 omits step S5, and in step S6 instructs the interface section of each terminal about the transmission frequency and the output light wavelength of the other terminal. The interface units need only set the demultiplexing wavelength of the optical demultiplexing circuit 84 and the tuning frequency of the variable tuner 27 to the instructed values.

[Explanation of the operation of the interface unit (Figs. 3 and 5)] Fig. 5 is a flow chart of a program for pre-communication processing by the interface unit 11. This program is the CP of Fig. 3.
It is stored in the ROM of U22. It should be noted that this program is started by a communication instruction from the connected terminal.

This flow chart shows the operation executed corresponding to the operation of the controller 13 shown in FIG.
When there is a further communication request, the process proceeds to step S10, where the multiplexer 23,
Through the electric-optical converter 80 and the optical star coupler 10, the controller 13 is designated as a partner terminal with which communication is desired. In step S11, the optical demultiplexing circuit 84, the optical-electrical converter 82, the demultiplexer 2
Wait for a response from the controller 13 input via 6, and check in step S12 if the other terminal can communicate.

If communication is not possible, the process proceeds to step S13 and the terminal 12 is notified to that effect, and the process ends, but if communication is possible with the partner terminal, the process proceeds to step S14 and the transmission or reception frequency and the optical signal instructed by the controller 13 are sent. To correspond to the wavelength of the signal, the modulation frequency of the modulator 21 and the variable tuner 27
Either or both of the tuning frequencies are set, and the output light wavelength of the electro-optical converter 80 and the optical demultiplexing circuit 8 are set in step S15.
Either or both of the demultiplexing wavelengths of 4 are set, and communication is started in step S16. It goes without saying that the setting of the frequency and the wavelength of the light here corresponds to the frequency and the wavelength of the light designated by the controller 13 in step S6 of FIG. 4 as described above.

[Explanation of Optical Star Coupler (FIG. 6)] FIGS. 6A and 6B are views showing a specific example of the unidirectional optical star coupler used in the present embodiment.

FIG. 6A is a view showing an optical star coupler having an orthogonal biconical taper structure, in which a plurality of optical fiber cables are fused at a portion 70. FIG. 6B shows a concentrated coupling type optical star coupler by the plane plate mixer 71.

[Description of Optical Demultiplexing Circuit (FIG. 7)] FIG. 7 is a diagram showing an example of the optical demultiplexing circuit.

The basic components of the optical demultiplexing circuit for wavelength division multiplexing are broadly divided into angular dispersion elements such as diffraction gratings and prisms,
There are wavelength-selective reflection / transmission films such as interference filters of dielectric multilayer films, and optical waveguides.

In FIG. 7, 72 is an optical signal from the optical star coupler 10.
An optical fiber 83 is incident on the optical fiber, and 73 is a lens for collimating the incident light of the optical signal 83. 74 is an angle dispersion element that reflects incident light by changing the reflection angle for each wavelength, and 75 is an exit lens,
The angular position conversion by the angle dispersion element 74 is combined and distributed to the light receiving elements 76 and 77 on the emission side. In this way, optical signals having different wavelengths are input to the respective light receiving elements, and the light is demultiplexed.

An optical multiplexer that couples a plurality of light beams to one transmission line can be realized in principle by reversing the input / output terminals of the optical demultiplexing circuit described above.

[Description of Remote Bridge (FIG. 8)] FIG. 8 is a diagram showing the configuration of the remote bridge 14.

The remote bridge 14 is used during communication between the optical star couplers 10 (between the nodes), and the remote bridge 14 is connected to a pair of input / output ports of the optical star coupler 10 with an optical fiber cable, and is connected to an NTT dedicated line or It is connected to a long-distance line 17 such as an optical fiber.

The signal from the optical star coupler 10 is converted into an electric signal by the optical-electrical (O / E) converter 90, and then is demultiplexed by the demultiplexer 91 (variable tuner group) controlled by the controller 13 via the bus line 15. It is split. In order to convert this demultiplexed signal to the frequency assigned to the channel for long distance transmission,
The signals from the controller 13 are used to control the VFOs 92-1 to 92-n, and the mixers 93-1 to 93-n perform conversion. After that, the signal is sent to the long-distance line 17 by the driver 95 through the multiplexer 94. However, if line 17 is optical fiber at this time, E /
O converter 96 is required.

In the example of this description, the control signal from the controller 13 is sent via the bus line 15, but as explained in the interface of the terminal, it is transmitted on the optical signal and separated by the demultiplexer and taken out. But it is possible.

On the other hand, the signal from the long-distance line 17 is received by the receiver 98.
Received by (O / E converter 9 if line 17 is optical fiber)
7 is required), converted into an optical signal by the electro-optical (E / O) converter 99, and then sent to the optical star coupler 10. However, when the long-distance line 17 is a high-speed digital line, the above function is performed by digital processing.

[Explanation of controller operation (Fig. 9)] Fig. 9 is a flow chart of communication pre-processing by the controller 13. This program is executed by the communication request from the interface unit 11 connected to the communication request terminal in the node. Be started.

First, in step S20, the interface unit 11 of the terminal 12 inputs a command for designating the other terminal with which the terminal 12 desires to communicate. If the partner terminal is a terminal within the same node, the process proceeds to step S22 to check whether the partner terminal can communicate. The operation of steps S23 to S27 is the same as the operation of steps S3 to S7 in FIG.

If the other terminal is not in the same node in step S21, the process proceeds to step S28 and the other node controller
For example, through the control line 18 such as a public telephone line,
It conveys terminal instructions and usable long-distance transmission and reception frequencies. The other party's controller checks if the instructed terminal can communicate, and when it returns the status, checks in step S29 if the other terminal can communicate, and if it cannot communicate, proceeds to step S24 and cannot communicate. Is notified to the communication requesting terminal, and the processing ends.

On the other hand, when communication is possible, the controller of the partner node checks the free frequency band in the node among the frequencies that can be transmitted / received at its own node (partner node) to determine the transmission frequency f _x and the reception frequency f _y . decide. Then, the carrier frequency of the remote bridge of the node is set to f _x and the frequency is notified to the node desiring communication via the line 18. As a result, the process proceeds to step S30, and the controller of the node desiring communication communicates the above-mentioned frequencies f _x and f _y with the control line.
It is input via 18, and in step S31 the transmission / reception frequency is instructed to the communication requesting terminal in the own node via the optical fiber cable 16 and the optical star coupler 10.

As a result, the interface unit corresponding to the communication requesting terminal
11 sets the tuning frequency of the variable tuner 27 to f _x .
It is needless to say that this frequency may be set for either or both of the transmission frequency and the reception frequency as required.

In step S32, the duplexer 91 of the remote bridge 14 is controlled to set the carrier frequency of the terminal desired to communicate, and VF
Controls O92-i and the frequency f _y by the corresponding mixer 93-i outputs.

In the above description, the transmission / reception frequency of the terminal desiring communication is set to match the transmission / reception frequency of the other terminal (other node), but for communication within each node, an independent frequency and wavelength are used for each node. Therefore, it is not always necessary to change the transmission / reception frequency of the communication request terminal or the wavelength of the optical signal.

[Explanation of frequency band (Fig. 10)] Fig. 10 is a diagram showing a frequency band used in this embodiment.
Band 110 is assigned to a control signal between controllers between nodes, and band 111 shows a frequency band of a signal used between remote bridges for long distance. Since lower frequencies have less attenuation in this way, a relatively low frequency band is used for long distances.

Band 112 is transmitting and receiving frequency band for short-range to be used between in tough ace unit within each node, the bandwidth of the video 1 channel (including audio) is 6MH _z, subjected to analog AM modulation on this signal 6MH provided a guard band of each 6MH _z relative _z, long-distance lines (band 111) to 10 channel, are assigned to 20 channels on the short range channel (band 112).

At this time, the communication within the node is completely independent,
The same channel can be assigned to each node, while the communication between nodes requires the assignment of a common channel throughout the system.

As described above, the present embodiment has the following effects.

(1) By combining an optical star coupler, a controller (personal computer class) and an interface, it becomes possible to construct a video interactive network system having a simple exchange function.

(2) N × N can be arbitrarily exchanged, but N × N is used because of the switching system based on the wavelength of the optical signal in addition to the frequency separation.
It is small and lightweight without requiring N circuit scale, and can handle a large capacity.

(3) Since the system is realized by the distributed control method that controls on a node-by-node basis, the system scale can be easily expanded or reduced, and at the same time, the increase in transmission capacity can be easily coped with by wavelength multiplexing.

(4) The system configuration becomes very simple by using the public telephone line only when the long distance transmission line is opened.

(5) Crosstalk of high-frequency signals can be reduced compared to the exchange transmission of mechanical relays, and a high-quality exchange transmission line can be realized.

[Effects of the Invention] As described above, according to the present invention, it is possible to independently perform communication between nodes having a plurality of terminals and communication between a plurality of terminals in a node. Also, there is an effect that transmission and reception can be performed with less attenuation.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of a communication system of the embodiment, FIG. 2 is a diagram showing a configuration of an optical star coupler node corresponding to each node of the embodiment, and FIG. 3 is a configuration of an interface unit of the embodiment. FIG. 4 is a flow chart showing the pre-processing of intra-node communication by the controller, FIG. 5 is a flow chart showing the pre-processing of communication by the interface unit of the embodiment, and FIGS. 6 (A) and 6 (B). Is a diagram showing a concrete example of an optical star coupler, FIG. 7 is a diagram showing an example of an optical demultiplexing circuit, FIG. 8 is a diagram showing a configuration of a remote bridge of an embodiment, and FIG. 9 is a controller of the embodiment. FIG. 10 is a flow chart showing the pre-processing of the intra-node communication and inter-node communication, and FIG. 10 is a diagram showing the frequency band used in this embodiment. In the figure, 11 ... Interface (I / F), 12 ... Terminal, 1
3 ... Controller, 10 ... Optical star coupler, 14 ... Remote bridge, 17 ... Communication line, 18 ... Control line, 21
...... Modulator, 22 …… CPU, 23 …… Multiplexer, 26 …… Splitter, 27 …… Variable tuner, 73,75 …… Lens, 74 …… Angle dispersive element, 76,77 …… Receiving light Element, 80,99 ... Electric-optical (E / O) converter, 82,90 ... Optical-electrical (O / E) converter, 83
...... Optical signal, 84 …… Optical demultiplexing circuit, 91 …… Demultiplexer, 92 ……
VFO, 93 …… Mixer, 94 …… Multiplexer, 95 …… Driver, 9
8 ... It is a receiver.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Genmei Miura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-58-120330 (JP, A) JP-A-59 -215135 (JP, A) International publication 86/5649 (WO, A)

Claims (1)

[Claims] 1. A communication system comprising a plurality of terminals, each of which is connected to a plurality of nodes, each of the plurality of nodes being connected via an optical cable, wherein the terminals convert transmission data into a signal of a first frequency. Modulated,
Outputting means for converting into an optical signal of a predetermined wavelength and outputting to the optical cable, inputting means for inputting an optical signal of a predetermined wavelength from the wavelength-multiplexed optical signal from the optical cable, and the predetermined inputting by the inputting means A conversion means for converting an optical signal of a wavelength into an electric signal; and a reception means for receiving an electric signal having a second frequency among the electric signals converted by the conversion means, wherein the node is connected to the optical cable. Means for multiplexing optical signals having a plurality of frequencies and a plurality of wavelengths output from a plurality of terminals, control means for instructing at least one of frequency tuning and wavelength selection at the transmitting side terminal and the receiving side terminal, A communication system comprising: a frequency conversion unit that converts the frequency of a signal transmitted from a node to another node.