JPH06224860A - Optical dispersion compensation method and optical dispersion compensator - Google Patents

Abstract

(57) [Summary] [Purpose] Compensate for group delay characteristics caused by the influence of optical fiber dispersion. [Structure] A ring-type optical resonator 4 having a delay optical path whose reciprocal of propagation delay time is Δf is used for an optical multiplex signal with a channel interval Δf. [Effect] Since the group delay characteristic of the ring type optical resonator has the period Δf, it is possible to collectively compensate the group delay characteristic of each channel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical fiber transmission, and particularly to long-distance transmission in which the influence of chromatic dispersion is remarkable, and
The present invention relates to an optical dispersion compensation method suitable for optical frequency (wavelength) multiplex transmission.

[0002]

2. Description of the Related Art Optical fiber transmission technology has enabled long-distance transmission exceeding 1000 km by utilizing an optical fiber amplifier. As a technical problem in long-distance transmission, there is a problem that the influence of chromatic dispersion of an optical fiber causes deterioration of transmission quality. As a method for solving the problem due to dispersion, a fiber having zero dispersion at the wavelength of transmission signal light has been developed.

On the other hand, in order to transmit a large amount of information, wavelength multiplex transmission and optical frequency multiplex transmission techniques have been advanced. In wavelength division multiplexing transmission, it is difficult to realize a fiber that makes the dispersion of all wavelengths zero, because the wavelengths for each channel are different.

There is a report of an optical element that can cancel the group delay characteristic due to the dispersion of an optical signal once affected by the dispersion of an optical fiber. The method using the ring type optical resonator shown in FIG. 2 is described in "EEE Photonics Technology Letters, Vol. 4, No. 8, p. 942, 199".
2 years (IEEE Photonics Technology Letters, Vol.4, No.
8, P.942, 1992) ". The optical transmission system of FIG. 2 is a system in which the optical signal from the optical transmitter 1 is transmitted through the optical fiber 3, passed through the optical dispersion compensator 4, and received by the optical receiver 6. The optical dispersion compensator 4 has a ring resonator structure including an optical coupler 41 with two inputs and two outputs and a delay optical path 42. The optical signal input to the optical dispersion compensator 4 is sent to the first input of the optical coupler 41. Optical coupler 4
The first output of 1 is connected to the delayed optical path 42 and the delayed optical path 4
The optical signal propagating through 2 is connected to the second input of the optical coupler 41. The optical signal from the second output of the optical coupler 41 becomes the output optical signal of the optical dispersion compensator 4.

The optical dispersion compensator 4 is a ring type optical resonator in which the optical signal propagating through the optical delay optical path 42 is input to the delay optical path 42 again through the optical coupler 41. A part of the optical signal input to the optical dispersion compensator 4 becomes a delayed optical signal that circulates in the optical delay optical path 42. Assuming that there is no optical signal loss in the ring resonator, the steady-state or time-averaged delayed optical signal intensity is proportional to the time (group delay time) the optical signal remains in the optical dispersion compensator 4. The delayed optical signal intensity and the group delay time change depending on the phase difference between the two optical signals input to the optical coupler 41. This phase difference causes the delay optical path 42
The frequency characteristic Tg (f) of the group delay time is 1 / Tr of 1 Tr as shown in FIG. Have a cycle. When the power coupling ratio is R and the power transmission coefficient of the ring portion is A, the group delay characteristic Tg (f) is expressed by the following equation.

[0006]

[Equation 1]

Chromatic dispersion is the amount of change in group delay time with respect to wavelength (optical frequency), and is a physical quantity proportional to the slope of FIG. The group delay characteristic of the optical dispersion compensator 4 is a group delay characteristic that cancels the influence of the chromatic dispersion corresponding to the slope d by selecting the wavelength like λ1 in FIG. When the optical frequency (wavelength) of the optical signal changes, the group delay characteristic for compensating for dispersion changes, so that the dispersion compensation characteristic deteriorates.

Further, the method using the Fabry-Perot type optical resonator shown in FIG. 3 is described in "I-E-E-Journal of Lightwave Technology Vol.
Issue, p. 649, 1990 (IEEE Journal of Lightwave
Technology Vol.8, No.5, P.649 1990) ”.

The optical dispersion compensator 4 shown in FIG. 3 comprises a reflected light separator 43 and a Fabry-Perot optical resonator 44. The input optical signal passes through the reflected light separator 43 and is input to the Fabry-Perot type optical resonator 44. The optical signal reflected from the Fabry-Perot type optical resonator 44 is separated by the reflected light separator 43 and output. The time required for the optical signal to make one round trip in the Fabry-Perot type optical resonator 44 is Tr, and it has a periodic group delay characteristic similar to that in FIG. When the amplitude reflectivity of the input / output end face of the Fabry-Perot type optical resonator 44 is r (power reflectivity is r ^ 2), and the intensity propagation constant of light that makes one round trip in the Fabry-Perot type optical resonator 44 is 1. The group delay characteristic of is expressed by the following equation.

[0010]

[Equation 2]

[0011]

Wavelength multiplex transmission and optical frequency multiplex transmission are promising for realizing large-capacity transmission. The reported optical fiber dispersion equalization technique is effective for signals of one wavelength, and it is necessary to perform fiber dispersion equalization for each channel in multiplex transmission. In the above-mentioned conventional method, there has been a problem that the scale is expanded due to the increase in the number of channels.

The periodic characteristic of the wavelength characteristic of the dispersion compensator changes depending on the propagation delay time Tr of the delay optical path.
In both the ring type optical resonator and the Fabry-Perot type optical resonator, since the optical path length of the optical resonator changes depending on the temperature, the group delay characteristic Tg
(F) is not stable. In the dispersion compensation method using an optical element, since the optical frequency (wavelength) dependency of the group delay time of the dispersion compensator is used, it is possible to match the wavelength at which the dispersion can be equalized with the wavelength of the signal being transmitted. is necessary. In the above-mentioned conventional method, there is no detailed description about the method of maintaining the state where the wavelengths match. In practical use, it is necessary to have a function of monitoring and controlling the coincidence of wavelengths.

An object of the present invention is to provide a plurality of optical frequencies (wavelengths).
It is possible to collectively compensate the influence of dispersion of multiplexed optical signals by one optical dispersion compensator.

Another object of the present invention is to stabilize the group delay characteristic of the optical dispersion compensator with respect to the optical frequency of the optical signal.

[0015]

In order to achieve the above object, an optical multiplex transmitter having a plurality of optical transmitters whose center optical frequencies (wavelengths) of optical outputs are set at intervals of Δf, and 2 inputs 2 are provided.
This can be realized by an optical dispersion compensator composed of an output optical coupler and a delay optical path whose propagation delay time substantially matches 1 / Δf.

Still another object can be realized by an optical dispersion compensator composed of a 2-input 2-output optical coupler, a delay optical path, an optical branching means, a photoelectric converting means, an optical path length changing means and an optical path length control circuit.

[0017]

The input and output of the optical dispersion compensator are connected to the first input and the first output of the optical coupler, respectively, and the delay optical path connects the second output and the second input of the optical coupler. In the optical dispersion compensator, the probability that the inputted optical multiplexed signal goes around the delay optical path changes depending on the optical frequency. This circulating probability is proportional to the group delay characteristic, and changes in a cycle of about Δf. Since the center optical frequency (wavelength) of the optical multiplex signal is set to the interval of Δf, the group delay characteristic of the optical dispersion compensator of the present invention has the same characteristic for each channel. Therefore, the optical dispersion compensator of the present invention is capable of compensating the group delay due to the dispersion received during the optical fiber transmission for all channels at once.

The optical branching means is arranged on the delay optical path and branches a part of the delayed optical signal propagating through the delay optical path. The branched delayed optical signal is input to the photoelectric conversion means, and is converted by the photoelectric conversion means into an electric signal indicating the delayed optical signal strength. The electric signal is input to the optical path length control circuit, and the optical path length control circuit controls the optical path length changing means arranged in all or part of the delay optical path. The group delay characteristic of the optical dispersion compensator according to the present invention is
It changes depending on the optical frequency and the optical path length of the delayed optical path, and is proportional to the intensity of the delayed optical signal. The intensity information of the delayed optical signal obtained by the optical branching unit and the photoelectric conversion unit is input to the optical path length control circuit and negatively fed back to the optical path length changing unit, whereby the intensity of the delayed optical signal can be stabilized. . As a result, the group delay characteristic is stabilized with respect to the optical frequency of the input optical signal, so that the delay due to the dispersion of the input optical signal can be stably compensated.

[0019]

1 shows the configuration of an embodiment of the present invention in an optical frequency multiplex transmission system. The optical multiplex transmission device 10 outputs an optical multiplex signal which is optical frequency multiplexed or wavelength multiplexed. The multiplexed optical signal is transmitted through one optical fiber 3 and input to the optical dispersion compensator 4. The output of the optical dispersion compensator 4 is input to the optical multiplex receiver 20 and received.

The optical multiplex transmitter 10 includes a plurality of optical transmitters 1.
And the optical multiplexing means 2. The optical transmitter 1 outputs an optical signal in which digital or analog information is modulated by intensity modulation, optical frequency modulation, optical phase modulation, or polarization modulation. The optical signals from the plurality of optical transmitters 1 are arranged such that their center optical frequencies are substantially equidistant Δf. The optical signals from the respective optical transmitters 1 are multiplexed by the optical multiplexing means 2 to become an optical multiplexed signal. The optical multiplexed signal output from the optical multiplexing means 2 is
The output of the optical multiplex transmission device 10 is input to the optical fiber 3.

The optical dispersion compensator 4 comprises a 2-input 2-output optical coupler 41 and a delay optical path 42 having a propagation delay time Tr. The input to the optical dispersion compensator 4 is the first of the optical coupler 41.
Entered in the input. The output from the optical dispersion compensator 4 is connected to the first output of the optical coupler 41. The second output and the second input of the optical coupler are connected by the delay optical path 42.
A part of the input optical multiplex signal is delayed by circulating around the delay optical path 42, and the group delay characteristic due to the dispersion received during the propagation of the optical fiber 3 is compensated. The optical multiplexed signal whose optical dispersion has been compensated is sent to the optical multiplex receiver 20.

The optical multiplex receiver 20 comprises an optical demultiplexer 5 and a plurality of optical receivers 6. Optical multiplex receiver 20
The optical multiplexed signal input to is input to the optical demultiplexer 5.
The optical multiplexed signal input to the optical demultiplexer 5 is demultiplexed into optical signals and distributed to the optical receiver 6. Each optical receiver 6 receives the distributed optical signal.

As described in the description of the prior art, the group delay characteristic Tg (f) changes depending on the propagation delay time Tr of the optical path 42. In the present invention, in order to collectively perform optical dispersion compensation on the optical multiplexed signals, the reciprocal of the propagation delay time 1 / T
r is substantially matched with the optical frequency interval Δf of the optical multiplexed signal. Here, “substantially coincident” means that Δf × (N−1) <N / Tr <Δf × (N + 1) (Equation 3) is satisfied, where N is the number of multiplexes. FIG. 5 shows the relationship between the group delay characteristic Tg (f) at Δf = 1 / Tr and the spectrum of the optical multiplex signal.
Shown in. However, the coupling coefficient r of the optical coupler 41 and the propagation delay time Tr of the delay optical path 42 are constant in the optical frequency range including all channels. Under this condition, the optical signals of all channels can be compensated by the optical dispersion compensator 4 with the same group delay characteristics. When the dispersion of the optical fiber 3 is large and the optical frequency (wavelength) range including all channels is smaller than the difference from the zero dispersion wavelength, the influence of dispersion on each channel is substantially constant.

By utilizing the periodicity of the group delay characteristic Tg (f) as in the present embodiment, the dispersion of a plurality of channels is compensated by one optical dispersion compensator 4 for each channel. It will be possible.

An optical star coupler or various optical multiplexers can be used as the optical combining means 2 in the present invention. Here, as the optical multiplexer, a Mach-Zehnder interference type wavelength multiplexer, a diffraction grating type wavelength multiplexer, or the like can be applied.

The optical dispersion compensator 4 in this embodiment is realized by a ring type optical resonator, but it can also be realized by a Mach-Zehnder type optical resonator.

In this embodiment, it is assumed that the dispersion of the optical fiber 3 is large, but the dispersion of the optical fiber 3 will be described with reference to the other three kinds of states.

First, the case where the channels are arranged such that the optical frequency (wavelength) at which the dispersion of the optical fiber 3 becomes zero is near the center will be described. In order to simplify the description, an embodiment will be described in which the number of channels N is 3, and the central channel has zero dispersion. FIG. 6 shows the group delay characteristic T in this embodiment.
The relationship between g (f) and the spectrum of the optical multiplex signal is shown. Generally, the number of channels N is applicable to a system having more channels. The channels at both ends receive positive dispersion and negative dispersion, respectively, and are input to the optical dispersion compensator 4.
It is assumed that the dispersion of the channels at both ends can be compensated at fa and fb, respectively. The period of the group delay characteristic of the dispersion compensator 4 is Δf +
Since it becomes fd / (N-1), the propagation delay time Tr is given by its reciprocal. Where fd is fa within one cycle
And fb '.

Next, an embodiment will be described in which the number of channels is large or the channel interval is large, so that the dispersion value is large but the dispersion values of the channels at both ends are different. Also in this embodiment, the above relation 1 / Tr = Δf + fd / (N-1) can be used. FIG. 7 shows the relationship between the group delay characteristic Tg (f) and the spectrum of the optical multiplex signal at this time.

Further, an embodiment taking into consideration the influence of the wavelength dependence of the coupling coefficient r will be described. When the coupling coefficient r changes substantially linearly with respect to the optical frequency, the peak height of the group delay characteristic Tg (f) changes as shown in FIG. Even under the condition that 1 / Tr = Δf where the channel interval and the period of the group delay characteristic match, the slope of the group delay characteristic at the optical frequency of each channel changes approximately linearly. The setting of the propagation delay time Tr can improve the dispersion compensation accuracy by considering the wavelength dependence of the coupling coefficient.

In these embodiments, the reciprocal 1 / Tr of the propagation delay time of the delay optical path 42 is defined as the optical frequency interval Δ of the optical multiplexed signal.
Since the period of the group delay characteristic of the optical dispersion compensator 4 can be made substantially equal to the period of the optical frequency interval by making it substantially equal to f,
Light dispersion can be compensated collectively. Further, by setting the propagation delay time Tr in consideration of the influence of dispersion and the optical frequency (wavelength) dependence of optical parameters, it is possible to apply to many types of optical multiplex transmission systems.

Group delay characteristic T that easily changes with temperature
g (f) needs to be stabilized corresponding to the optical frequency of the optical signal that compensates for dispersion. FIG. 9 shows a configuration of an embodiment capable of monitoring and stabilizing the desired group delay characteristic.
The optical dispersion compensator 4 of the present embodiment includes a ring type optical resonator portion including a 2-input 2-output optical coupler 41 and a delay optical path 42.
Optical branching means 51, photoelectric conversion means 52, optical path length control circuit 5
3. A part for stabilizing the group delay characteristic, which is composed of the optical path length changing means 54. The optical signal input to the optical dispersion compensator 4 is sent to the first input of the optical coupler 41.
The first output of the optical coupler 41 is connected to the delay optical path 42,
The optical signal propagating through the delay optical path 42 is connected to the second input of the optical coupler 41. The optical signal from the second output of the optical coupler 41 becomes the output optical signal of the optical dispersion compensator 4.

Next, a method of stabilizing the group delay characteristic will be described. The coupling coefficient r2 of the optical branching means 51 on the delay optical path 42 is smaller than the coupling coefficient r1 of the optical coupler 41. The intensity of the monitor light signal branched by the light branching unit 51 is converted into an electric signal by the photoelectric conversion unit 52. The electric signal is proportional to the intensity of the delayed optical signal and the group delay characteristic, and is input to the optical path length control circuit 53. The output of the optical path length control circuit 53 is input to the optical path length changing means 54, and the group delay characteristic can be adjusted by changing the propagation delay time Tr of the delay optical path 42. By monitoring the intensity information of the delayed optical signal and performing negative feedback to the optical path length of the delayed optical path 42, the average intensity of the delayed optical signal can be stabilized. Stabilizing the average intensity of the delayed optical signal stabilizes the average group delay time.

In this embodiment, the optical frequency (wavelength) of the optical signal
Since the average group delay time can be stabilized even when is changed, deterioration of the optical dispersion compensation characteristic can be suppressed.

The optical branching means 51 and the photoelectric converting means 52 used in this embodiment may be an optical coupler and a photodiode, respectively. However, it is also possible to utilize the light leakage of the optical waveguide as the light branching means.

The optical coupler 41 and the delay optical path 4 of this embodiment
2. Realizing the optical branching means 51 and the optical path length changing means 54 as an optical integrated circuit is effective in improving the stability and reliability of the characteristics. When integrating using a quartz waveguide, a method of controlling the waveguide temperature by a heater or a Peltier element is suitable for the optical path length changing means 54. Also,
By using a waveguide made of a ferroelectric material (such as lithium niobate), the optical path length changing means 54 can be controlled by an electric field. Further, by integrating the semiconductor waveguide, the optical path length changing means 54 can be controlled by injecting carriers. In the semiconductor waveguide, it is easy to integrate the photoelectric conversion means 52 and the optical amplification unit for compensating the propagation loss of the delay optical path 42.

The region for controlling the temperature is not limited to a part of the delay optical path 42, and the same effect can be obtained in the entire delay optical path 42 or the entire optical integrated circuit as shown in FIG.

The present invention can be applied to the single optical signal transmission system described in the prior art, and its configuration is shown in FIG.
Shown in 1.

The optical dispersion compensator 4 of the present invention comprises an optical receiver 2
Not only immediately before 0, it can be used by connecting to an optical repeater or an optical transmitter. FIG. 12 is a block diagram of an embodiment of the optical repeater transmission system. The optical signal from the optical transmitter 60 is transmitted to the optical receiver 62 while being relayed by the optical repeater 61 through the plurality of optical fibers 3.

FIG. 13 shows a block diagram of the optical transmitter 60.
The optical transmitter 60 comprises a plurality of optical transmitters 1, an optical multiplexer 2, and an optical dispersion compensator 4. Multiple optical transmitters 1
The optical signal output from the optical multiplexer is multiplexed by the optical multiplexing means 2 to become an optical multiplexed signal having a channel interval of Δf. The optical multiplexed signal is input to the optical dispersion compensator 4, and the influence of dispersion generated after transmission is compensated before transmission.

FIG. 14 shows a block diagram of the optical repeater 61.
The optical repeater 61 is composed of two optical amplifiers 63 and an optical dispersion compensator 4. The optical signal input to the optical repeater 61 is first amplified by the optical amplifier 63-1. The amplified optical signal is then input to the optical dispersion compensator 4 to become a dispersion-compensated optical signal. The dispersion compensated optical signal is
It is input to another optical amplifier 63-2, amplified to a predetermined output intensity, and output from the optical repeater 61.

FIG. 15 shows a block diagram of the optical receiver 62.
The optical receiving device 62 includes an optical amplifier 63, an optical dispersion compensator 4, an optical demultiplexer 5, and a plurality of optical receivers 6. The optical signal input to the optical receiver 62 is first amplified by the optical amplifier 63. The amplified optical signal is input to the optical dispersion compensator 4, and the dispersion is compensated for all channels collectively. The dispersion-compensated optical signal is input to the optical demultiplexer 5 and demultiplexed into optical signals of each channel. The demultiplexed optical signals are input to the optical receiver 6 and received.

Compensating for dispersion in the optical repeater 61 has the effect of suppressing the phenomenon in which frequency modulation generated during relay transmission is converted into amplitude modulation.

In the present embodiment, the number of optical amplifiers 63 used in the optical repeater 61 is not limited to two.

Such an optical repeater transmission system can also be applied to a system for transmitting one optical signal.

Although this embodiment has been described with reference to the embodiment using the ring type optical resonator, the same effect can be obtained even if the present invention is replaced with the Mach-Zehnder type optical resonator.

In the present embodiment, the optical multiplex receiver used in the optical multiplex transmission system has a structure including the optical demultiplexer 5, but the present invention uses an optical filter or an optical heterodyne receiver. As a result, the present invention can be applied to a system that is a receiving device that selectively receives a channel.

[0048]

As described above, according to the present invention, by making the reciprocal 1 / Tr of the propagation delay time of the delay optical path substantially coincide with the optical frequency interval Δf of the optical multiplexed signal, the influence of dispersion of the optical fiber is exerted. In addition, it has an effect of collectively compensating the group delay characteristics of the optical multiplexed signal.

Further, by stabilizing the intensity of the delayed optical signal propagating in the delayed optical path, it is possible to stabilize the group delay characteristic for the optical signal.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical multiplex transmission system according to the present invention.

FIG. 2 is a configuration diagram of an optical transmission system according to a conventional method.

FIG. 3 is a configuration diagram of an optical dispersion compensator according to a conventional method.

FIG. 4 is a group delay characteristic of the optical dispersion compensator.

FIG. 5 shows an optical multiplex signal spectrum and group delay characteristics 1 of an optical dispersion compensator.

FIG. 6 shows a group delay characteristic 2 of an optical multiplex signal spectrum and an optical dispersion compensator.

FIG. 7 shows an optical multiplex signal spectrum and a group delay characteristic 3 of an optical dispersion compensator.

FIG. 8 shows an optical multiplex signal spectrum and a group delay characteristic 4 of an optical dispersion compensator.

FIG. 9 is a configuration diagram of an optical dispersion compensator according to the present invention.

FIG. 10 is a block diagram of an optical dispersion compensator according to the present invention.

FIG. 11 is a configuration diagram of an optical transmission system according to the present invention.

FIG. 12 is a configuration diagram of an optical repeater transmission system according to the present invention.

FIG. 13 is a block diagram of an optical multiplex transmission apparatus according to the present invention.

FIG. 14 is a block diagram of an optical multiplex repeater according to the present invention.

FIG. 15 is a block diagram of an optical multiplex receiver according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical transmitter, 2 ... Optical multiplexing means, 3 ... Optical fiber, 4 ...
Optical dispersion compensator, 5 ... Optical demultiplexer, 6 ... Optical receiver, 10 ... Optical multiplex transmitter, 20 ... Optical multiplex receiver, 41 ... Optical coupler, 42 ... Delay optical path, 43 ... Reflected light separator, 44 Fabry-Perot type optical communication device, 51 ... Optical branching device, 52 ... Photoelectric converting device, 53 ... Optical path length control circuit, 54 ... Optical path length changing device, 60 ... Optical multiplex transmission device, 61 ... Optical multiplex repeater device, 6
2 ... Optical multiplex receiver, 63 ... Optical amplifier.

Claims (8)

[Claims] 1. An optical multiplex transmission apparatus which multiplexes output optical signals from a plurality of optical transmitters by an optical multiplexing means and outputs an optical multiplex signal having an optical frequency (wavelength) interval of Δf, and the optical multiplex transmission. An optical fiber that transmits the optical multiplex signal output from the device, and the optical multiplex signal that is transmitted is demultiplexed into each optical signal by an optical demultiplexer, and the demultiplexed optical signal is received by one or more optical signals. In an optical multiplex transmission system having a configuration including an optical multiplex receiving device for receiving by an optical multiplexer, the optical dispersion compensator includes a two-input and two-output optical coupler and a delay optical path whose propagation delay time is substantially equal to 1 / Δf. ,
The input and output of the optical dispersion compensator are respectively the first and the first of the optical coupler.
The delay optical path is connected to an input and a first output, and the delay optical path is connected to a second output and a second input of the optical coupler. An optical dispersion compensator for compensating the delay due to the dispersion received during the optical fiber transmission for all the channels at a time by outputting with a time delay for An optical dispersion compensating method, wherein the optical dispersion compensating method is arranged between fibers, between the optical fiber and the optical multiplex receiver, or in the middle of the optical fiber. 2. An optical dispersion compensator comprising a 2-input 2-output optical coupler, a delay optical path, an optical branching means, a photoelectric conversion means, an optical path length control circuit and an optical path length changing means, said optical dispersion compensator. Input and output are respectively connected to a first input and a first output of the optical coupler, the delay optical path is connected to a second output and a second input of the optical coupler, and the optical branching means is The delayed optical signal disposed on the delayed optical path branches a part of the delayed optical signal propagating through the delayed optical path, and the photoelectric conversion means receives the branched delayed optical signal and outputs an electric signal indicating the delayed optical signal intensity. The optical path length control circuit receives the electric signal and controls the optical path length changing means arranged in all or part of the delayed optical path, and a part of the input optical signal outputs the delayed optical path. The group delay characteristics caused by the delayed optical signal that circulates are And the delay optical signal intensity, which changes depending on the optical path length of the delay optical path and is proportional to the group delay characteristic, is formed by the optical branching means, the photoelectric conversion means, the optical path length control circuit, and the optical path length changing means. An optical dispersion compensator which is stabilized by a loop and compensates for a delay due to dispersion of an input optical signal by a stabilized group delay characteristic and outputs the optical signal. 3. The optical dispersion compensator according to claim 1,
An optical dispersion compensating method, wherein the optical coupler and the delay optical path are optical circuits integrated on the same glass or ferroelectric substrate. 4. The optical dispersion compensator according to claim 2,
The optical coupler, the delay delay optical path and the optical demultiplexing means,
An optical dispersion compensator, which is an optical circuit integrated on the same glass substrate, wherein the optical path length changing means is a heater or a Peltier element for changing the temperature of the whole or a part of the optical circuit. 5. The optical dispersion compensator according to claim 2,
The optical coupler, the delay delay optical path and the optical demultiplexing means,
An optical circuit integrated on the same ferroelectric substrate,
An optical dispersion compensator characterized in that the optical path length changing means is an optical element for changing the refractive index of all or part of the delay optical path by an electric field. 6. The optical dispersion compensator according to claim 2,
The optical coupler, the delay delay optical path and the optical demultiplexing means,
An optical circuit integrated on the same semiconductor substrate, wherein the optical path length changing means is an optical element for changing the refractive index of the whole or a part of the delay optical path by the injected carrier density. Compensator. 7. The optical dispersion compensator according to claim 6,
The optical coupler, the delay delay optical path and the optical demultiplexing means,
An optical circuit integrated on the same semiconductor substrate, wherein the whole or a part of the delay optical path amplifies an optical signal by injecting carriers, thereby branching by the optical branching means and propagation of the delay optical path. An optical dispersion compensator characterized by compensating for loss. 8. An optical amplification repeater comprising the optical dispersion compensator according to claim 2 and one or more optical amplifiers, wherein an input optical signal is input to the optical amplifier and at least one of the optical amplifiers is used. A light characterized by being amplified, inputting the amplified optical signal to the optical dispersion compensator, compensating for delay due to dispersion by the optical dispersion compensator, further amplifying by the remaining optical amplifier, and then outputting. Amplifying repeater.