JPH0828685B2 - Optical repeat transmission method and optical repeat transmission apparatus - 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 repeater transmission method for carrying out repeater transmission of optical signals as they are, and an optical repeater transmission apparatus used therefor.

[0002]

2. Description of the Related Art As an optical repeater transmission system, as shown in FIG. 9, an optical regenerative repeater 91 for performing optical-electrical conversion / electrical-optical conversion for regenerative repeating is connected in multiple stages. The structure of the optical regenerator 91 is 3R as shown in FIG.
Function (equalization amplification; Reshaping, timing extraction, Retiming, identification reproduction; Regenerat
ing). The basic operation of this regenerator is to convert an optical signal transmitted through the optical fiber 1a into an electric signal in the optical-electrical (OE) conversion circuit 1001 and to an appropriate level in the equalization amplification circuit 1002. The timing circuit 1004 amplifies and extracts a timing signal having a frequency synchronized with the data rate of the transmission line from the equalized waveform after the amplification, and the identification circuit 1003 discriminates the equalized waveform using the timing signal. Then, the electric-optical (EO) conversion circuit 1005 regenerates the optical pulse, and the regenerated optical signal is sent to the optical fiber transmission line 1b at the next stage. However, FIG.
Since the optical regenerative repeater as shown in FIG. 1 performs the regenerative repeating processing of the signal in the electric circuit, it is not possible to realize an ultra high-speed transmission system of several tens of gigabits per second in terms of realization of the electric circuit. Is difficult from.

For this reason, an optical circuit for overcoming the processing speed limit and the response speed limit occurring in the electric signal processing system of the optical regenerator by using the optical signal processing and having the 3R function and realizing the high speed signal processing is provided. An all-optical regenerative repeater has been proposed (JP-A-1-241232).

Further, as a method for simultaneously performing waveform shaping and amplification of an optical signal as it is, in Japanese Laid-Open Patent Publication No. 2-36581, as shown in FIG. 11, a received signal whose waveform has been previously shaped by an electric circuit is used. (FIG. 11a), waveform shaping of the input optical signal (FIG. 11b) to the semiconductor laser amplifier having waveform deterioration by superimposing on the drive current of the semiconductor laser optical amplifier,
There has been proposed an optical waveform shaping device that amplifies and sends out a good waveform (FIG. 11c) to an optical fiber transmission line.

Further, as a system for carrying out relay transmission as it is, as shown in FIG. 9, a 1R (R: Reshapin) using an optical amplifier 92 between optical regenerators 91b and 91c is used.
g) There is an optical repeater transmission system. This is a method in which the power level of the signal light is compensated by the amount of transmission loss in the optical fiber transmission line, the power level of the signal light is raised to a certain level, and the signal light is sent to the next stage optical fiber transmission line. In addition, by performing frequency modulation on the semiconductor laser of the optical terminal station, dispersion pre-equalization (preliminarily equalizing the waveform deterioration of the optical signal due to wavelength dispersion occurring in the optical fiber) is performed on the transmission signal light, and A distributed pre-equalization method called the pre-chirp method, which reduces the power penalty and expands the repeater interval between optical regenerators, was introduced by N. HENMI et al.
Ional Conference on Optica
l Fiber Communication) technical digest PD8 (Post Deadline Paper. # 8).

[0006]

However, in the all-optical 3R optical regenerative repeater in which the optical regenerative repeater is all-optical, the electrical circuit is replaced with an optical circuit in order to overcome the limit of the operating speed of the electrical circuit. Although it enables high-speed operation by implementing signal processing by means of optical signal processing, the influence of waveform deterioration due to chromatic dispersion on the optical fiber transmission line has not been removed, and therefore the transmission distance limit is limited by the chromatic dispersion limit. There is.

Further, in the method of performing waveform shaping using a semiconductor laser amplifier, although the waveform shaping and amplification of an input optical signal in which waveform degradation has occurred are simultaneously performed and sent to the optical fiber transmission line of the next stage, As a characteristic, there is a correlation between the gain and the wavelength, the wavelength at which the maximum gain is obtained is limited, and the optimum condition cannot always be obtained for the optical signal wavelength of the transmission line. Further, although the waveform shaping is performed on the input optical signal as in the all-optical 3R regenerative repeater described above,
Since the influence of waveform deterioration caused by chromatic dispersion on the optical fiber transmission line has not been eliminated, the problem that the transmission distance limit is limited by the chromatic dispersion limit cannot be solved yet.

Further, in the 1R optical repeater transmission system using the optical amplifier, the signal light power level is amplified, but like the above-mentioned two systems, the influence of waveform deterioration due to chromatic dispersion received on the optical fiber transmission line is eliminated. There is a problem that the transmission distance limit is limited by the chromatic dispersion limit because it is not hidden. Further, in the pre-chirp method in which the influence of chromatic dispersion is compensated in advance and signal light is transmitted, the chromatic dispersion value that can be actually compensated is limited. Therefore, the maximum transmission distance is 1R optical repeater using an optical amplifier in the middle. Even if it were, there was a problem that it was limited to the optical fiber transmission distance corresponding to the maximum chromatic dispersion compensation value.

[0009]

According to a first aspect of the present invention, there is provided an optical repeater transmission method in which the phase of the signal light is synchronized with the phase of the envelope signal of the intensity-modulated signal light transmitted in a dispersion medium. It is characterized in that the change point of the electric signal obtained by optoelectric conversion of the signal light is detected, and then frequency division is performed by ½ to perform predetermined optical phase modulation for relay transmission.

An optical repeater transmission device according to the first aspect of the present invention comprises an optical amplifier for optically amplifying signal light propagating through an optical fiber transmission line, an optical amplifier drive current circuit for supplying a drive current to the optical amplifier, An optical branching circuit for branching a part of the output light of the optical amplifier, and a signal light connected to the first output end of the optical branching circuit for phase modulation to input the signal light to a subsequent optical fiber transmission line. An optical phase modulator for outputting to, a light receiving circuit connected to the second output end of the optical branching circuit to convert the input signal light into an electric signal, and detecting a waveform change point of the output signal of the light receiving circuit. A change point detection circuit, a 1/2 frequency divider circuit that receives the output signal of the change point detection circuit and generates a 1/2 frequency division signal, and equalizes the output signals of the 1/2 frequency division circuit. An equalization circuit that makes the envelope waveform of the optical signal almost
An optical phase modulator drive circuit for converting the output signal of the equalization circuit into a predetermined voltage amplitude and driving the optical phase modulator is provided.

In the optical repeater transmission method of the second aspect of the present invention, the signal light is optically transferred to the phase of the signal light in synchronization with the phase of the envelope signal of the intensity-modulated signal light transmitted in the dispersion medium. After detecting the change point of the electrical signal converted into electricity, 1/2
The optical phase modulation is stopped by detecting the presence / absence of signal light transmitted through the dispersion medium while performing predetermined optical phase modulation with a pulse signal obtained by frequency division and performing relay transmission. To do.

An optical repeater transmission apparatus of the second invention comprises a first optical branching circuit for branching a signal light propagating through an optical fiber transmission line and a first output end of the first optical branching circuit. An optical amplifier that optically amplifies the signal light that is connected and input, an optical amplifier drive current circuit that supplies a drive current to the optical amplifier, and a second optical branch circuit that branches a part of the output light of the optical amplifier. An optical phase modulator that is connected to the first output terminal of the second optical branching circuit, performs phase modulation on the input signal light, and outputs the signal light to an optical fiber transmission line in a subsequent stage; First light receiving circuit connected to the second output terminal of the optical branching circuit to convert the input signal light into an electric signal, and change point detection for detecting a waveform change point of the output signal of the first light receiving circuit Circuit and the output signal of the change point detection circuit
A 1/2 frequency dividing circuit for generating a signal of 1/2 frequency division;
An equalization circuit that equalizes the output signal of the divide-by-2 circuit into an envelope waveform of an optical signal, and an optical phase that converts the output signal of the equalization circuit into a predetermined voltage amplitude and drives the optical phase modulator. A modulator driving circuit, a second light receiving circuit that is connected to the second output end of the first optical branching circuit and converts the input signal light into an electric signal, and an output signal of the second light receiving circuit. And an input optical comparison circuit for comparing with a predetermined reference voltage and outputting an input optical abnormal signal to the optical phase modulator driving circuit and stopping the optical phase modulation driving signal when the voltage is less than or equal to the reference voltage. .

According to a third aspect of the optical repeater transmission method of the present invention, the signal light is transmitted to the phase of the signal light in synchronization with the phase of the envelope signal of the intensity-modulated signal light transmitted through the dispersion medium. After detecting the change point of the electrical signal converted into electricity, 1/2
A predetermined optical phase modulation is performed with a pulse signal obtained by frequency division, and the optical level of the optical phase-modulated signal light to be output to the dispersion medium in the subsequent stage is maintained at a constant level for relay transmission.

An optical repeater transmission device according to a third aspect of the present invention includes a first optical branching circuit for branching a signal light propagating through an optical fiber transmission line and a first output end of the first optical branching circuit. An optical amplifier that optically amplifies the signal light that is connected and input, an optical amplifier drive current circuit that supplies a drive current to the optical amplifier, and a second optical branch circuit that branches a part of the output light of the optical amplifier. An optical phase modulator that is connected to the first output terminal of the second optical branching circuit and outputs a signal light by performing phase modulation on the input signal light, and a second optical branching circuit of the second optical branching circuit. A first light receiving circuit connected to the output end of the optical signal for converting the input signal light into an electric signal, a change point detection circuit for detecting a waveform change point of the output signal of the first light receiving circuit, and the change point detection A 1/2 divider circuit that receives the output signal of the circuit and generates a 1/2 divided signal An equalizer circuit that equalizes the output signal of the 1/2 frequency divider circuit to form an envelope waveform of an optical signal, and converts the output signal of the equalizer circuit to a predetermined voltage amplitude to drive the optical phase modulator. An optical phase modulator driving circuit, a second light receiving circuit which is connected to the second output end of the first optical branching circuit and converts the input signal light into an electric signal, and the second light receiving circuit An input optical comparison circuit that compares an output signal with a predetermined reference voltage and outputs an input optical abnormality signal to the optical phase modulator drive circuit to stop the optical phase modulation drive signal when the reference voltage is lower than the reference voltage; A third optical branching circuit that inputs the output signal light of the modulator, branches a part of it, and outputs one to the optical fiber transmission line in the subsequent stage, and an input that is connected to the other output end of the third optical branching circuit A third light receiving circuit for converting the generated signal light into an electric signal, and the third light receiving circuit. DC signal which outputs the output signal so that it is always the same by inputting the output signal of the peak value detection circuit for detecting the peak value and the output signal of the peak value detection circuit and comparing it with a predetermined reference voltage An amplifier and an optical amplifier gain control for inputting the output signal of the DC amplifier and the output signal from the input optical comparison circuit to control the optical amplifier drive circuit to make the output level of the output signal light of the optical phase modulator constant. And a circuit.

In the optical repeater transmission method of the fourth aspect of the present invention, the signal light is transmitted to the phase of the signal light in synchronization with the phase of the envelope signal of the intensity-modulated signal light transmitted in the dispersion medium. After detecting the change point of the electrical signal converted into electricity, 1/2
A predetermined optical phase modulation is performed by a pulse signal obtained by frequency division, and at least an abnormal state of signal light interruption of the input signal light and the optical phase-modulated output light is detected and displayed.

An optical repeating transmission apparatus according to a fourth aspect of the present invention includes a first optical branching circuit for branching a signal light propagated through an optical fiber transmission line and a first output end of the first optical branching circuit. An optical amplifier that optically amplifies the signal light that is connected and input, an optical amplifier drive current circuit that supplies a drive current to the optical amplifier, and a second optical branch circuit that branches a part of the output light of the optical amplifier. An optical phase modulator that is connected to the first output terminal of the second optical branching circuit and outputs a signal light by performing phase modulation on the input signal light, and a second optical branching circuit of the second optical branching circuit. A first light receiving circuit connected to the output end of the optical signal for converting the input signal light into an electric signal, a change point detection circuit for detecting a waveform change point of the output signal of the first light receiving circuit, and the change point detection A 1/2 divider circuit that receives the output signal of the circuit and generates a 1/2 divided signal An equalizer circuit that equalizes the output signal of the 1/2 frequency divider circuit to form an envelope waveform of an optical signal, and converts the output signal of the equalizer circuit to a predetermined voltage amplitude to drive the optical phase modulator. An optical phase modulator driving circuit, a second light receiving circuit which is connected to the second output end of the first optical branching circuit and converts the input signal light into an electric signal, and the second light receiving circuit An input optical comparison circuit that compares an output signal with a predetermined reference voltage and outputs an input optical abnormality signal to the optical phase modulator drive circuit to stop the optical phase modulation drive signal when the reference voltage is lower than the reference voltage; A third optical branching circuit that inputs the output signal light of the modulator, branches a part of it, and outputs one to the optical fiber transmission line in the subsequent stage, and an input that is connected to the other output end of the third optical branching circuit A third light receiving circuit for converting the generated signal light into an electric signal, and the third light receiving circuit. Output signal of the first peak value detection circuit for detecting the peak value and the output signal of the first peak value detection circuit for comparison with a predetermined reference voltage so that they are always the same. A DC amplifier that outputs an output signal, and an output signal of the DC amplifier and an output signal from the input optical comparison circuit are input to control the optical amplifier drive circuit to keep the output level of the output signal light of the optical phase modulator constant. And an input disconnection display circuit for inputting an abnormal input signal from the input optical comparison circuit and outputting an input disconnection alarm display signal, and an output signal for the first peak value detection circuit. A second peak value for detecting a peak value by inputting an output disconnection display circuit that outputs an output disconnection alarm display signal when compared with a predetermined reference voltage and is equal to or less than the reference voltage, and an output signal of the 1/2 frequency divider circuit Detection times And a phase modulation control abnormality display circuit that compares the output signal voltage of the second peak value detection circuit with a predetermined reference voltage and outputs a phase modulation signal alarm display signal when the voltage is equal to or lower than the reference voltage. Is characterized by.

[0017]

In the present invention, not only the amplitude of the signal light is amplified by the optical amplifier, but also the deterioration of the waveform of the optical signal caused by the chromatic dispersion of the optical transmission line is directly modulated by the phase modulation to the signal light in advance. Pre-equalization 1 by applying equalization with light
R multi-stage relay becomes possible.

Further, since the phase modulation operation is stopped when the input optical signal to the optical repeater transmission apparatus of the present invention is cut off,
It is possible to secure reliability as a relay transmission device without causing malfunction noise in the relay system in the next stage.

Further, since the state of the optical power level of the output signal is monitored and the gain of the optical amplifier is controlled, the optical output power level from the optical repeater transmission apparatus of the present invention can be always kept constant. In addition, when the optical input is cut off or the optical output is cut off due to the inside of the relay transmission device, the injection of the drive current to the optical amplifier is stopped, so that the optical amplifier is not damaged and further unnecessary from the relay transmission device. It is possible to prevent output of noise, and it is possible to avoid abnormal operation of the optical repeater transmission system.

Furthermore, the in-service monitor can be realized in the 1R optical repeater transmission apparatus by detecting and displaying the abnormal state such as the optical input interruption and the optical output interruption.
Fault management of the entire optical transmission system can be easily performed.

[0021]

1 is a block diagram of an embodiment of an optical repeater transmission method and an optical repeater transmission apparatus of the first invention.

In FIG. 1, the wavelength 1.5 transmitted through the optical fiber 101a, which is a 1.55 μm zero-dispersion optical fiber.
NRZ with 7 μm and intensity modulation signal speed of 10 Gbit / sec
The (non-return to zero) modulated optical signal is
By dispersion pre-equalization at the transmitting end, a pulse waveform almost equal to the optical pulse waveform at the transmitting end as shown in FIGS. 2A and 4A is input to the optical amplifier 102 at an optical power level of −18 dBm, Optically amplified to an optical power level of 10 dBm. Here, the optical amplifier 102 is an erbium-doped optical fiber amplifier excited by a light source having a wavelength of 1.48 μm. A drive current is injected from the optical amplifier drive circuit 103 into this light source.

Most of the output light from the optical amplifier 102 is the optical fiber 101b, the optical branching device 104, and the optical fiber 1.
It is input to the optical phase modulator 105 via 01c, but a part (about 1/100) of it is split by the optical splitter 104,
The light receiving circuit 106 converts the optical signal into an electric signal. This received signal is, as shown in FIG.
After passing through the stage, noise components are superimposed on the received signal itself due to the effect of noise accumulation in the optical amplifier. Therefore, when the optical phase modulator 105 is driven by directly using this received signal (FIG. 5a), desired phase modulation characteristics cannot be obtained. Therefore, in the present invention, the optical phase modulator drive signal is generated by the following method. That is,
The received signal converted into an electric signal in the light receiving circuit 106 of FIG. 1 (FIG. 5a) is input to the change point detection circuit 107. The change point detection circuit 107 detects a change point of the input pulse signal (FIG. 5a) and outputs a change point detection signal as shown in FIG. 5b. As a method of generating the change point detection signal (FIG. 5b), there is a full-wave rectification circuit using a differentiating circuit, a differential detection method using an exclusive OR circuit, or the like. In the 1/2 frequency divider circuit 108, the change point detection circuit 10
The rising portion of the input pulse signal from FIG. 7 (FIG. 5b) is used as a trigger signal to generate a 1/2 frequency-divided signal (FIG. 5).
c). This 1/2 frequency-divided signal (FIG. 5c) has a waveform obtained by reproducing a received signal sequence having good S / N. 1/2 divider circuit 1
The output signal of No. 08 is input to the equalization circuit 109, and waveform equalization is performed so as to have an NRZ signal waveform almost equal to the input optical signal waveform to the optical phase modulator 105. The NRZ signal is converted into an NRZ signal having a predetermined output voltage peak value by the optical phase modulator driving circuit 110 and applied to the optical phase modulator 105. Since a half-wave voltage of about 5V is used here, the peak-to-peak value is about 2π / 5 (r
2) to give a phase shift of (ad: radian).
As shown in (b), the peak-to-peak value is about 2.
It outputs the 0V NRZ signal. With this drive signal, the optical signal input to the optical phase modulator 105 undergoes phase modulation as shown in FIG. 2C with a peak-to-peak value of 2π / 5 (rad), and as a result, FIG. ), The carrier frequency of the 10 Gbit / s optical signal is modulated, and is shifted from the carrier center frequency to the higher side at the rising edge of the optical pulse. Here, the phase modulation given to the optical signal corresponds to the wavelength dispersion of 1000 ps / nm, and the average wavelength dispersion value at the wavelength of 1.57 μm is about 3 p.
Pre-equalized transmission of about 300 km is performed as s / nm · km. In the conventional method, the transmission distance is about 100 km, but by using the optical repeater transmission method and the optical repeater transmission apparatus of the present invention, the transmission distance limit caused by the influence of the chromatic dispersion of the transmission line is improved by about 3 times. Will be done.

The optical power level sent to the optical fiber 101e is about 5 dBm due to the insertion loss of the optical phase modulator 105 and the like. In addition, optical fiber 300km
Since the transmission loss is about 70 to 80 dB, the optical repeater with pre-equalization in the next stage (optical repeater transmission device according to the present invention)
, And a repeater consisting of three to four optical amplifiers is installed for relay transmission. Since an input optical signal to the optical repeater with pre-equalization (optical repeater transmission apparatus according to the present invention) in the next stage has a waveform substantially similar to the optical signal waveform shown in FIG. With the method and device configuration, it is possible to perform relay transmission with optical signals as they are. This situation will be described with reference to the configuration diagram of the optical repeater transmission system of FIG. 3 and the response waveform of each part of FIG. In FIG. 3, in response to the input optical signal (FIG. 4a) to the optical repeater transmission apparatus 301a of the present invention, the optical repeater transmission apparatus 301
In a, desired optical phase modulation is performed. The response waveform at the point in FIG. 3B (FIG. 4B) is not affected by the chromatic dispersion because it is before the transmission though the phase modulation is applied.
The response waveform is the same as that of the input optical signal at point (a).
The optical signal waveform of FIG. 4 (b) is affected by chromatic dispersion in the optical fiber transmission line to cause pulse compression or waveform broadening of pulse spread, and becomes a waveform as shown in FIG. 4 (c) (pulse compression in FIG. 4c). Is shown). However, at the input point (FIG. 3d) of the optical repeater transmission apparatus 301b of the present invention in the next stage, the optical input signal waveform becomes equivalent to that at the transmission end (point in FIG. 3b) as shown in FIG. 4 (d).

FIG. 6 is a block diagram of an embodiment of an optical repeater transmission method and an optical repeater transmission apparatus of the second invention.

In this embodiment, the wavelength 1.5 transmitted through the optical fiber 601a which is a 1.55 μm zero dispersion optical fiber is used.
NRZ with 7 μm and intensity modulation signal speed of 10 Gbit / s
The optical amplification of the modulated optical signal by the optical amplifier 602, the phase modulation of the output light by the optical phase modulator 605, and the dispersion pre-equalization are performed exactly as in the first embodiment of the present invention. However, the difference is that the drive signal applied to the optical phase modulator 605 is controlled.

In this embodiment, the output signal from the optical phase modulator drive circuit 610 which is the drive signal for the optical phase modulator 605 is not always generated, but the disconnection of the input optical signal to the optical amplifier 602 is detected. And the optical phase modulator drive circuit 610
It has a function of stopping the generation of the output signal from. That is, the input signal from the optical fiber 601a is branched by the optical branching device 611, one is input to the optical amplifier 602 via the optical fiber 601g, and the other is input to the light receiving circuit 612 via the optical fiber 601f. The input signal converted from the optical signal to the electric signal in the light receiving circuit 612 is input to the input optical comparison circuit 613. In this input light comparison circuit 613, the signal voltage input from the light receiving circuit 612,
The voltage is compared with a voltage corresponding to a preset optical input interruption, and when the voltage is equal to or less than the set value, the optical phase modulator drive circuit 610
In response, the drive signal stop control signal 614 is output to stop the drive signal to the optical phase modulator 605. Therefore, even when the optical input signal from the optical fiber 601a is disconnected, it is possible to prevent the output of the intensity modulation signal due to the failure of the optical phase modulator 605 or the output of the optical signal in which the erroneous phase modulation occurs. It is possible to prevent malfunction of the entire optical repeater transmission system.

FIG. 7 is a block diagram of an embodiment of an optical repeater transmission method and an optical repeater transmission apparatus of the third invention.

In this embodiment, the wavelength 1.5 transmitted through the optical fiber 701a, which is a 1.55 μm zero-dispersion optical fiber, is used.
NRZ with 7 μm and intensity modulation signal speed of 10 Gbit / s
Regarding the optical amplification of the modulated optical signal by the optical amplifier 702, the phase modulation of the output light by the optical phase modulator 705 to perform dispersion pre-equalization, and the detection of disconnection of the input signal, Is exactly the same as the embodiment of the present invention, except that the power level of the output optical signal to the optical fiber 701e is kept constant and the disconnection of the output optical signal is detected.

In this embodiment, the output optical signal of the optical phase modulator 705 is passed through the optical fiber 701h and the optical branching device 715.
, And one of them is input to the light receiving circuit 716 through the optical fiber 701i at a ratio of about 1/100.
Therefore, most of the output optical signal from the optical phase modulator 705 is the optical fiber 70 which is the optical fiber transmission line to the next stage.
1e. The output optical signal branched and input to the light receiving circuit 716 is converted into an electric signal and then input to the peak value detection circuit 719 to perform peak value detection. The DC amplifier 718 compares the input signal voltage from the peak value detection circuit 719 with a voltage value corresponding to the optical signal power level that is preset and should be stably sent to the optical fiber 701e as an optical repeater transmission device, and always compares The control voltage signal is output to the optical amplifier gain control circuit 717 so as to be equal. In the optical amplifier gain control circuit 717, the DC amplifier 7
Optical amplifier drive circuit 703 based on input signal from 18
Is controlled to change the injection current to the optical amplifier 702 to make the gain of the optical amplifier 702 variable. In the optical amplifier gain control circuit 717, the DC amplifier 71
When the input voltage from 8 reaches a set value by constantly comparing it with a voltage value which is set in advance and is equal to the state in which the optical signal output to the optical fiber 701e is cut off, or when the optical signal from the input optical comparison circuit 713 When the control signal indicating the disconnection of the input signal is input, the gain increasing operation of the optical amplifier drive circuit 703 is stopped. Therefore, it is possible to prevent the destruction of the optical amplifier 702 without injecting an excessive current into the 1.48 μm pumped laser diode built in the optical amplifier 702. Further, in the normal operation state, even if the input optical signal power level from the optical fiber 701a or the output optical signal power level to the optical fiber 701e changes due to temperature change in the optical amplifier 702 and the optical phase modulator 705, With the gain control function provided in the optical repeater transmission apparatus of the present invention, an optical signal of a constant level is always output to the optical fiber 701e, and the operational stability of the optical repeater transmission system can be ensured.

FIG. 8 is a block diagram of an embodiment of the optical repeater transmission method and the optical repeater transmission apparatus of the fourth invention.

In this embodiment, the wavelength 1.5 transmitted through the optical fiber 801a which is a 1.55 μm zero dispersion optical fiber is used.
NRZ with 7 μm and intensity modulation signal speed of 10 Gbit / s
The modulated optical signal is optically amplified by the optical amplifier 802, the output light is phase-modulated by the optical phase modulator 805 to be subjected to dispersion pre-equalization, and further the input / output signal disconnection detection and the output optical signal power level. Is held exactly the same as the third embodiment of the present invention, but the fourth invention is different in that an abnormal operation state display function is added to enable fault management. .

In the embodiment shown in FIG. 8, the 1/2 divider circuit 808 is used.
Of the output signal is detected by the peak value detection circuit 820, the output signal voltage of the peak value detection circuit 820 is compared with a predetermined reference voltage, and the phase modulation signal alarm display signal is output when the output voltage is below the reference voltage. It has a phase modulation control abnormality display circuit 821. Therefore, the input optical signal from the optical fiber 801a is cut off, or the optical amplifier 8
Even when the drive signal to the optical phase modulator 805 is cut off due to the output break of the optical amplifier 801b due to the failure of 02,
The abnormal state can be monitored by the phase modulation control abnormality display circuit 821. Also, the input disconnection display circuit 82
Also in the output disconnection display circuit 3, each abnormal state is displayed by the signal voltage from the input light comparison circuit 813 and the peak value detection circuit 819. By taking the above configuration,
Faults can be monitored as in the conventional optical repeater, and faults can be managed in an in-service state by using the output signals of the respective display circuits.

Although the NRZ code has been used as the transmission path code in the above description, the present invention can be similarly applied to the RZ (return to zero) code.

[0035]

As described above, according to the present invention, not only the optical signal level of an NRZ-modulated optical signal can be relayed and transmitted as an optical signal, but also 1R optical relay transmission including dispersion pre-equalization is possible. Therefore, it becomes possible to perform distributed pre-equalization 1R multi-stage relay with the optical signal as it is, and thus the relay transmission by the all-optical 3R repeater or the 3R repeater requiring optical-electrical conversion, which is generally complicated in function and configuration, is transmitted. It becomes unnecessary depending on the distance, and the number of 3R repeaters can be reduced even if the transmission distance is long.

Further, when the input optical signal to the optical repeater transmission apparatus of the present invention is cut off, a measure is taken so as not to perform phase modulation on the optical output from the optical repeater transmission apparatus. It is possible to secure reliability as a relay transmission device without causing malfunction noise to the system.

Further, since the state of the optical power level of the output signal can be monitored and the gain of the optical amplifier can be controlled, the optical output power level from the optical repeater transmission apparatus of the present invention can always be kept constant. In addition, when the optical input is cut off or the optical output is cut off due to the inside of the relay transmission device, the injection of the drive current to the optical amplifier is stopped, so that the optical amplifier is not damaged and further unnecessary from the relay transmission device. It is possible to prevent output of noise, and it is possible to avoid abnormal operation of the optical repeater transmission system.

Further, according to the optical repeater transmission apparatus of the present invention, it is possible to display an abnormal state such as a light input break or a light output break. Therefore, 1 in-service monitor
This can also be realized in an R optical repeater transmission device, and fault management of the entire optical transmission system can be easily performed.

[Brief description of drawings]

FIG. 1 is a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the functions of the first, second, third, and fourth inventions.

FIG. 3 is a diagram for explaining the functions of the first, second, third, and fourth inventions.

FIG. 4 is a diagram for explaining the operation of the first, second, third, and fourth inventions.

FIG. 5 is a diagram for explaining the operation of the first, second, third, and fourth inventions.

FIG. 6 is a second embodiment of the present invention.

FIG. 7 is a third embodiment of the present invention.

FIG. 8 is a fourth embodiment of the present invention.

FIG. 9 is a diagram used for explaining a conventional example.

FIG. 10 is a diagram used for explaining a conventional example.

FIG. 11 is a diagram used for explaining a conventional example.

[Explanation of symbols]

101a, 101b, 101c, 101d, 101e,
1a, 1b, 1c, 601a, 601b, 601c, 6
01d, 601e, 601f, 601g, 701a, 7
01b, 701c, 701d, 701e, 701f, 7
01g, 701h, 701i, 801a, 801b, 8
01c, 801d, 801e, 801f, 801g, 8
01h, 801i Optical fiber 102,602,702,802,92 Optical amplifier 103,603,703,803 Optical amplifier drive circuit 104,604,611,704,711,715,8
04, 811, 815 Optical branching device 105, 605, 705, 805 Optical phase modulation circuit 106, 606, 612, 706, 712, 716, 8
06,812,816 Light receiving circuit 107,607,707,807 Change point detecting circuit 108,608,708,808 1/2 frequency dividing circuit 109,609,709,809 Equalizing circuit 110,610,710,810 Optical phase Modulator drive circuit 301a, 301b Optical regenerative repeater transmission device 613, 713, 813 Input optical comparison circuit 614, 714, 720, 814 Signal line 717, 817 Optical amplifier gain control circuit 718, 818 DC amplifier 719, 819, 820 Peak value detection circuit 821 Optical phase modulator abnormality display circuit 822 Output disconnection display circuit 823 Input disconnection display circuit 91a, 91b, 91c Optical regenerator 1001 O / E conversion circuit 1002 Equalization amplification circuit 1004 Timing extraction circuit 1003 Discrimination circuit 1005 E / O conversion circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H04B 10/16 10/18

Claims (8)

[Claims] 1. A change point detection of an electric signal obtained by optoelectrically converting the signal light into the phase of the signal light in synchronization with the phase of the envelope signal of the intensity-modulated signal light transmitted through a dispersion medium. An optical repeater transmission method characterized by performing predetermined optical phase modulation with a pulse signal obtained by performing 1/2 division after performing the repeater transmission. 2. An optical amplifier for optically amplifying a signal light propagating through an optical fiber transmission line, an optical amplifier drive current circuit for supplying a drive current to the optical amplifier, and a part of output light of the optical amplifier. An optical branching circuit for branching, an optical phase modulator that outputs a signal light to a subsequent optical fiber transmission line by performing phase modulation on the input signal light connected to the first output end of the optical branching circuit, A light receiving circuit connected to the second output terminal of the optical branching circuit to convert the input signal light into an electric signal, a change point detecting circuit for detecting a waveform change point of the output signal of the light receiving circuit, and the change point detection Input the output signal of the circuit 1
A 1/2 frequency dividing circuit for generating a signal of 1/2 frequency division;
An equalization circuit that equalizes the output signal of the divide-by-2 circuit into an envelope waveform of an optical signal, and an optical phase that converts the output signal of the equalization circuit into a predetermined voltage amplitude and drives the optical phase modulator. An optical repeater transmission device comprising a modulator driving circuit. 3. A change point detection of an electric signal obtained by optoelectrically converting the signal light into the phase of the signal light in synchronization with the phase of the envelope signal of the intensity-modulated signal light transmitted through the dispersion medium. After performing the frequency division, the optical signal is subjected to predetermined optical phase modulation with a pulse signal obtained and then relay transmission is performed, and the presence or absence of signal light transmitted through the dispersion medium is detected to perform the optical phase modulation. An optical repeater transmission method characterized by stopping. 4. A first optical branching circuit for branching the signal light propagating through an optical fiber transmission line, and an optical amplifier for amplifying the signal light input to the first output end of the first optical branching circuit. Of the optical amplifier, an optical amplifier drive current circuit for supplying a drive current to the optical amplifier, a second optical branch circuit for branching a part of the output light of the optical amplifier, and a second optical branch circuit An optical phase modulator that is connected to the first output end and performs phase modulation on the input signal light to output the signal light to an optical fiber transmission line in a subsequent stage, and a second output end of the second optical branch circuit. Connected to the first light receiving circuit for converting the input signal light into an electric signal, a change point detecting circuit for detecting a waveform change point of the output signal of the first light receiving circuit, and an output of the change point detecting circuit Input signal and generate 1/2 frequency signal 1/2
A frequency dividing circuit, an equalizing circuit that equalizes the output signal of the 1/2 frequency dividing circuit to form an envelope waveform of an optical signal, and an output signal of the equalizing circuit that converts the output signal into a predetermined voltage amplitude An optical phase modulator driving circuit for driving the phase modulator, a second light receiving circuit connected to the second output end of the first optical branching circuit to convert the input signal light into an electric signal, An input optical comparison circuit that compares the output signal of the second light receiving circuit with a predetermined reference voltage and outputs an input optical abnormality signal to the optical phase modulator drive circuit and stops the optical phase modulation drive signal when the output voltage is less than the reference voltage. An optical repeater transmission device comprising: 5. A change point detection of an electric signal obtained by optoelectrically converting the signal light into the phase of the signal light in synchronization with the phase of the envelope signal of the intensity-modulated signal light transmitted through the dispersion medium. After carrying out the frequency division, a predetermined optical phase modulation is performed with a pulse signal obtained by dividing the frequency by 1/2 and the level of the optical phase-modulated signal light to be output to the dispersion medium in the subsequent stage is maintained at a constant level and relayed and transmitted. A characteristic optical repeater transmission method. 6. A first optical branching circuit for branching the signal light propagating through an optical fiber transmission line, and an optical amplifier for amplifying the signal light input to the first output end of the first optical branching circuit. Of the optical amplifier, an optical amplifier drive current circuit for supplying a drive current to the optical amplifier, a second optical branch circuit for branching a part of the output light of the optical amplifier, and a second optical branch circuit An optical phase modulator that is connected to the first output terminal and outputs a signal light by performing phase modulation on the input signal light, and a signal that is input and connected to the second output terminal of the second optical branch circuit. A first light receiving circuit that converts light into an electric signal, a change point detection circuit that detects a waveform change point of the output signal of the first light receiving circuit, and an output signal of the change point detection circuit are input to 1 / Two
A 1/2 divider circuit for generating a divided signal, an equalizer circuit for equalizing the output signal of the 1/2 divider circuit into an envelope waveform of an optical signal, and an output signal of the equalizer circuit To an optical phase modulator driving circuit for converting the signal into a predetermined voltage amplitude and driving the optical phase modulator, and converting the signal light input by being connected to the second output end of the first optical branch circuit into an electric signal. The second light receiving circuit, which compares the output signal of the second light receiving circuit with a predetermined reference voltage, and outputs an input optical abnormality signal to the optical phase modulator driving circuit when the reference voltage is lower than this reference voltage. An input optical comparison circuit for stopping the modulation drive signal, a third optical branching circuit for inputting the output signal light of the optical phase modulator and branching a part of the output signal light and outputting one to the optical fiber transmission line in the subsequent stage, Connects to the other output end of the third optical branch circuit and converts the input signal light into an electrical signal A third light receiving circuit, a peak value detecting circuit for inputting an output signal of the third light receiving circuit to detect a peak value, and an output signal of the peak value detecting circuit for comparison with a predetermined reference voltage. The output of the optical phase modulator by inputting the output signal of the direct current amplifier and the output signal of the direct current amplifier and the output signal from the input optical comparison circuit and controlling the optical amplifier drive circuit An optical repeater transmission apparatus comprising: an optical amplifier gain control circuit that keeps an output level of signal light constant. 7. A change point detection of an electric signal obtained by optoelectrically converting the signal light into the phase of the signal light in synchronization with the phase of the envelope signal of the intensity-modulated signal light transmitted through the dispersion medium. Performs predetermined optical phase modulation with a pulse signal obtained by performing 1/2 frequency division, and at least detects / displays an abnormal state of signal light interruption of the input signal light and the optical phase-modulated output light. An optical repeater transmission method characterized by the above. 8. A first optical branching circuit for branching the signal light propagating through an optical fiber transmission line, and an optical amplifier for amplifying the signal light input to the first output end of the first optical branching circuit. Of the optical amplifier, an optical amplifier drive current circuit for supplying a drive current to the optical amplifier, a second optical branch circuit for branching a part of the output light of the optical amplifier, and a second optical branch circuit An optical phase modulator that is connected to the first output terminal and outputs a signal light by performing phase modulation on the input signal light, and a signal that is input and connected to the second output terminal of the second optical branch circuit. A first light receiving circuit that converts light into an electric signal, a change point detection circuit that detects a waveform change point of the output signal of the first light receiving circuit, and an output signal of the change point detection circuit are input to 1 / Two
A 1/2 divider circuit for generating a divided signal, an equalizer circuit for equalizing the output signal of the 1/2 divider circuit into an envelope waveform of an optical signal, and an output signal of the equalizer circuit To an optical phase modulator driving circuit for converting the signal into a predetermined voltage amplitude and driving the optical phase modulator, and converting the signal light input by being connected to the second output end of the first optical branch circuit into an electric signal. The second light receiving circuit, which compares the output signal of the second light receiving circuit with a predetermined reference voltage, and outputs an input optical abnormality signal to the optical phase modulator driving circuit when the reference voltage is lower than this reference voltage. An input optical comparison circuit for stopping the modulation drive signal, a third optical branching circuit for inputting the output signal light of the optical phase modulator and branching a part of the output signal light and outputting one to the optical fiber transmission line in the subsequent stage, Connects to the other output end of the third optical branch circuit and converts the input signal light into an electrical signal A third light receiving circuit, a first peak value detection circuit for inputting an output signal of the third light receiving circuit to detect a peak value, and an output signal of the first peak value detection circuit for inputting a predetermined value. A DC amplifier that outputs an output signal so as to be always the same by comparing with a reference voltage, and an output signal of the DC amplifier and an output signal from the input optical comparison circuit are input to control the optical amplifier drive circuit and An optical amplifier gain control circuit for making the output level of the output signal light of the optical phase modulator constant, an input disconnection display circuit for inputting an input abnormal signal from the input optical comparison circuit and outputting an input disconnection alarm display signal, and An output disconnection display circuit which inputs the output signal of the first peak value detection circuit, compares it with a predetermined reference voltage, and outputs an output disconnection alarm display signal when the output voltage is below the reference voltage, and the output signal of the 1/2 frequency divider circuit. Enter The second peak value detection circuit for detecting the peak value and the output signal voltage of the second peak value detection circuit and a predetermined reference voltage are compared and a phase modulation signal alarm display signal is output when the voltage is less than the reference voltage. An optical repeater transmission device comprising: a phase modulation control abnormality display circuit for outputting.