JP3055518B2 - Optical transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission device used for transmitting an optical signal.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. 4-286433 discloses a demodulation circuit for demodulating an optical signal, a signal comparison circuit for comparing an input signal of a signal amplification circuit for amplifying the optical signal with a demodulation signal of the demodulation circuit. An optical transmission device that includes a signal transmission / reception unit that transmits and receives an optical signal and that controls the gain of the signal amplification circuit based on the comparison result of the signal comparison circuit is disclosed.

[0003]

By the way, in the conventional optical transmission device, the gain control of the signal amplifying circuit is uniformly performed without considering the frequency characteristics of the signal transmitting / receiving section. Therefore, the conventional optical transmission device has a problem that an optical signal in a certain frequency band is amplified to an appropriate level, but an optical signal in a certain frequency band is not amplified to an appropriate level. Further, in an optical transmission apparatus having a multi-stage connection configuration in which an optical signal to be multiplexed is input for each stage, the optical signal to be multiplexed has a different frequency characteristic from the optical signal input from the previous stage. was there. This is because the conventional optical transmission apparatus does not have a circuit configuration in which the frequency characteristics of the multiplexed optical signal are identified and corrected so as to improve the frequency characteristics. In short, in the conventional optical transmission device, the multi-stage configuration has a problem that the frequency characteristics are poor and, consequently, the optical transmission over a wide band cannot be performed. The present invention has been made under such a background, and an object of the present invention is to provide an optical transmission device that can improve frequency characteristics and can perform wideband optical transmission.

[0004]

According to a first aspect of the present invention, there is provided a multiplexing means for multiplexing an optical signal and a multiplexed optical signal, a frequency identification means for identifying a frequency of the multiplexed optical signal, An output unit that outputs an output signal of the multiplexing unit, a band-pass filter to which the output signal is input, and a pass frequency band that changes in accordance with the identification result of the frequency identification unit, and the band-pass filter. Level correcting means for correcting the level of the multiplexed optical signal to a predetermined value based on the level of the passed signal, and outputting the corrected multiplexed optical signal to the multiplexing means. Features. The invention according to claim 2 is
2. The optical transmission apparatus according to claim 1, wherein the level correction unit is configured to detect a level of the passing signal, and a gain thereof is controlled based on a detection result of the level detection unit, and the multiplexed light is controlled. Amplifying means for correcting the signal level to a predetermined value and outputting the corrected multiplexed signal to the multiplexing means. According to a third aspect of the present invention, in the optical transmission device according to the first or second aspect, the multiplexing unit, the frequency identification unit, the output unit, the bandpass filter, and the level correction unit are provided in one stage. Are characterized in that they are configured in multiple stages.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of an optical transmission device according to an embodiment of the present invention. The optical transmission device shown in this figure has a multi-stage configuration including multiplexing units 11 to 14. The multiplexing unit 11 multiplexes the optical signal So1 and the multiplexed optical signal Sp1, and outputs the multiplexed signal as an optical signal So2. The multiplexing unit 11 has the configuration shown in FIG.

That is, in the multiplexing unit 11 shown in FIG. 2, reference numeral 2 denotes a frequency identification circuit for identifying the frequency of the multiplexed optical signal Sp1 (see FIG. 1), and outputs the identified frequency to the variable BPF 7 as a frequency identification signal. I do. Further, the frequency identification circuit 2 outputs the multiplexed optical signal Sp1 to the variable AMP (amplifier) 3. The variable AMP 3 has its gain controlled by a gain signal input from a level detector 8 described below, and amplifies the multiplexed optical signal Sp1 to a predetermined level based on the gain.

Reference numeral 4 denotes a multiplexing unit for multiplexing (multiplexing) the multiplexed optical signal Sp1 and the optical signal So1 amplified by the variable AMP3. 5 is an optical signal S corresponding to the output signal of the multiplexing unit 4
It is an LD (laser diode) that emits o2. 6 is
Built-in PD that emits an optical signal according to the output signal of the multiplexing unit 4
(Photodiode). The variable BPF 7 has its frequency pass band controlled by the frequency identification signal input from the frequency identification circuit 2, and outputs a signal of the frequency pass band among the signals input from the built-in PD 6 to the level detector 8. The level detector 8 detects the level of the output signal of the variable BPF 7 and outputs the detection result to the variable AMP 3 as a gain signal. That is, the variable AMP3
Functions to correct the level of the optical signal So2 so that the frequency component of the multiplexed optical signal Sp1 becomes a predetermined level.

The multiplexing units 12 to 14 shown in FIG.
(See FIG. 2). That is, the multiplexing unit 12 multiplexes the optical signal So2 and the multiplexed optical signal Sp2 and outputs the multiplexed optical signal So3, and the multiplexing unit 13 outputs the optical signal So2.
3 and the multiplexed optical signal Sp3 are multiplexed to output an optical signal So4. Similarly, the multiplexing unit 14 multiplexes the optical signal So4 and the multiplexed optical signal Sp4 and outputs an optical signal So5.

In the above configuration, the multiplexing unit 11 shown in FIG.
When the optical signal So1 and the multiplexed optical signal Sp1 are input to
The optical signal So1 shown in FIG. 2 is input to the multiplexing unit 4 and the multiplexed optical signal Sp1 is input to the frequency identification circuit 2. Thus, after identifying the frequency of the multiplexed optical signal Sp1, the frequency identification circuit 2 outputs the identification result to the variable BPF 7 and outputs the multiplexed optical signal Sp1 to the variable AMP3. Now, from the level detector 8, the gain signal is
It is assumed that it is output to P3.

Thus, the multiplexed optical signal Sp1 is amplified to a predetermined level by the variable AMP 3 and then input to the multiplexing unit 4. In the multiplexing unit 4, the optical signal So1 and the multiplexed optical signal Sp1 amplified by the variable AMP3 are output.
Are multiplexed (multiplexed), and the output signal of the multiplexing unit 4 is LD
5 is input. As a result, the optical signal So2 corresponding to the output signal is output from the LD 5, and the internal P
From D6, an optical signal corresponding to the output signal is changed to a variable BPF.
7 is input.

Thus, in the variable BPF 7, only the signal of the frequency band corresponding to the frequency identification signal input from the frequency identification circuit 2 among the optical signals output from the built-in PD 6 is passed. That is, the signal output from the variable BPF 7 is a signal of the frequency band component of the multiplexed optical signal Sp1 of the optical signal So2. The level of the output signal of the variable BPF 7 is detected by the level detector 8, and the gain signal is output from the level detector 8 to the variable AMP 3.

As a result, the gain of the variable AMP 3 is controlled, and in the variable AMP 3, the level of the multiplexed optical signal Sp 1 input from the frequency discriminating circuit 2 is corrected to a predetermined level. Then, in the multiplexing unit 4, the multiplexed optical signal Sp1 and the optical signal So1 whose levels have been corrected are multiplexed (multiplexed). For this reason, the output signal of the multiplexing unit 4 is a signal with improved frequency characteristics. Therefore, LD
The optical signal So2 output from 5 is also a signal with improved frequency characteristics. Similarly, in the multiplexing unit 12 shown in FIG. 1, the optical signal So2 and the multiplexed optical signal Sp2 are multiplexed, and the multiplexing unit 12 outputs the optical signal So3. The optical signal So3 is obtained by level-correcting the component of the multiplexed optical signal Sp2 in the same manner as the optical signal So2 described above. Further, similarly, the multiplexed optical signal Sp3 and the optical signal So3 are multiplexed in the multiplexing unit 13, and the optical signal So4 and the multiplexed optical signal Sp4 are multiplexed in the multiplexing unit 14.

As described above, in the optical transmission apparatus according to the above-described embodiment, the frequency characteristic of the multiplexed optical signal Sp1 is taken into consideration, and the multiplexed optical signal S
The level of the component of p1 is corrected, and as a result, the optical signal S
The frequency characteristics of o2 are improved. Similarly, in the optical transmission device according to the above-described embodiment, the optical signal S2 is considered in consideration of the frequency characteristics of the multiplexed optical signals Sp2 to Sp4.
The components of the multiplexed optical signals Sp2 to Sp4 among o2 to So5 are level corrected. That is, in the optical transmission device according to the above-described embodiment, the frequency characteristics can be improved, and the optical transmission over a wide band can be performed.

[0014]

As described above, according to the first and second aspects of the present invention, the component of the multiplexed optical signal in the output signal is level-corrected in consideration of the frequency characteristics of the multiplexed optical signal. Therefore, it is possible to improve the frequency characteristics, and thus, it is possible to obtain the effect that optical transmission over a wide band can be performed. Further, according to the third aspect of the present invention, even in a multi-stage configuration, the frequency characteristics can be improved, and the effect that broadband optical transmission can be performed can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an optical transmission device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a multiplexing unit 11 shown in FIG.

[Explanation of symbols]

 11 to 14 multiplexing unit 2 frequency discrimination circuit 3 variable AMP 4 multiplexing unit 5 LD 6 built-in PD 7 variable BPF 8 level detector

Claims (3)

(57) [Claims] A multiplexing means for multiplexing an optical signal and a multiplexed optical signal; a frequency identification means for identifying a frequency of the multiplexed optical signal; and an output means for outputting an output signal of the multiplexing means. A band-pass filter to which the output signal is input and whose passing frequency band changes in accordance with the identification result of the frequency identification means; and the multiplexing based on the level of the passing signal passing through the band-pass filter. An optical transmission apparatus, comprising: level correcting means for correcting the level of an optical signal to a predetermined value and outputting the corrected multiplexed optical signal to the multiplexing means. 2. The level correction means includes: a level detection means for detecting a level of the passing signal; a gain of which is controlled based on a detection result of the level detection means; 2. The optical transmission apparatus according to claim 1, further comprising an amplification unit that level-corrects the signal and outputs the corrected multiplexed signal to the multiplexing unit. 3. The multiplexing means, the frequency identification means,
The optical transmission device according to claim 1, wherein the output unit, the bandpass filter, and the level correction unit are configured as one stage and configured in multiple stages.