JPH05344067A - Monitor method for optical relay system and loopback circuit and transmission reception circuit - Google Patents

Abstract

PURPOSE:To provide an optical loopback system in which a complicated circuit is avoided and the operating system is monitored very simply. CONSTITUTION:Outputs or inputs of incoming and outgoing repeater circuits in all or designated number of optical repeaters 16a-16n are connected through a proper loss to form monitor loopback circuits Aa-An in which part of signals on incoming and outgoing optical fiber transmission lines 12a-12n are looped back at all times in the optical repeaters 16a-16n, a monitor signal is sent from incoming outgoing transmission terminal stations 23a, 23b to the optical fiber transmission lines 12a-12n and plural monitor signals looped back via the loopback circuits Aa-An of all or predetermined number of the optical repeaters 16a-16n are received by the reception terminal stations 24a, 24b to detect separately the signals for each optical repeater thereby monitoring the state of the transmission line up to each of the optical repeaters 16a-16n.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long distance relay system using an optical amplifier such as an optical submarine cable system, and a method for monitoring a repeater and a line section which are indispensable for maintenance and operation thereof. The present invention relates to an optical circuit device used directly.

[0002]

2. Description of the Related Art FIG. 11 shows a conventional monitoring loopback circuit of a relay system. 1, 2 are optical shutters, 3 are control command receiving circuits, 4 are measuring circuits, 5 are response signal transmitting circuits, 6-9
Is an optical branch circuit, 10 and 11 are regenerative repeater circuits, and 12 and 13
Is an upstream optical fiber transmission line and a downstream optical fiber transmission line, respectively.

In a conventional relay system, a regenerative relay system is used in which an optical digital signal is converted into an electric signal by each relay and reproduced. In the example of FIG. 11, the monitoring loopback circuits 14 and 15 provided in each repeater α are opened for a predetermined one in response to a command from the terminal station, so that the optical signal regenerated by the repeater α is transmitted downstream. Fiber transmission line 1
Turn back to 3. By receiving this signal at the receiving end station, the transmission characteristic from the transmitting end station to the receiving end station via the predetermined repeater α is measured. By sequentially operating the monitoring loopback circuits 14 and 15, the monitoring operation can be performed over the entire system.

Since this monitoring system folds back the main line signal, it is used not in operation but in non-operational state such as construction or failure. On the other hand, during operation, the operation status and the code error rate of the light source of each repeater α are measured in each repeater α, and the result is superimposed and transmitted on the main line signal to acquire maintenance data, It is used for predicting failures and for planned repairs.

In a system using an optical amplifier, unlike a regenerative repeater system, all optical signals are directly amplified and relayed through a repeater. Therefore, a monitoring system different from the regenerative relay system can be introduced. It is naturally possible to use the above-mentioned optical folding circuit in a repeater using optical amplification.

[0006]

However, as shown in FIG. 11, the conventional optical folding method is for remotely controlling the optical shutters 1 and 2 for opening and closing the monitoring folding circuits 14 and 15 and the remote shutters from the terminal station. Since the control command receiving circuit 3 is required, the circuit becomes inevitable. In particular, in an optical amplifier repeater in which the repeater circuit is greatly simplified compared to the regenerative repeater system, the conventional monitoring circuit is large in scale, which poses a problem from the viewpoint of system economy and high reliability.

In view of the above, the present invention focuses on the characteristics of the optical amplification system, avoids the circuit complexity of the conventional optical folding system, and is an extremely simple optical repeater system that enables system monitoring during operation. A monitoring method, a loopback circuit, and a transmission / reception circuit are provided.

[0008]

The above-mentioned problems can be solved by adopting the novel characteristic construction method and means listed in the following by the present invention. That is, the first feature of the method of the present invention is configured by inserting a plurality of optical repeaters each including an upstream and downstream repeater circuit using an optical amplifier into an upstream and downstream optical fiber transmission line. In the optical repeater system,
All the repeaters of the repeater system, or the respective outputs or inputs of the upstream and downstream repeater circuits in the specified repeater are connected to each other via a moderate loss, and the upstream and downstream transmission fibers are connected. A part of the above signal constitutes a monitoring loopback circuit that is always looped back within each repeater, sending monitoring signals from the upstream and downstream transmission terminal stations to the optical fiber transmission line, and all or predetermined The state of the transmission path to each repeater is monitored by receiving a plurality of monitor signals that are returned via the monitor return circuit of the repeater at the receiving terminal station, separating and detecting for each repeater. It is a method of monitoring an optical repeater system.

The second feature of the method of the present invention is that in the first feature of the method, when the number of repeaters per fiber of the optical repeater system is N, the loss of the loopback circuit of each repeater is 10
This is a monitoring method for an optical repeater system in which the amount of loss is made larger than the loss amount determined by adding 15 dB to LOG (N) dB.

A third feature of the method of the present invention is the method according to the first feature, wherein an M-sequence pseudo-random signal whose repetition period is longer than the round trip delay time of the optical transmission system is transmitted and received from the terminal station as a supervisory signal. This is a monitoring method of an optical repeater system in which a terminal repeats a correlation detection with a transmission supervisory signal to separate and detect signals returned by a predetermined repeater from a plurality of simultaneously received return signals.

A fourth feature of the method of the present invention is that, in the first feature of the method, a reference signal of a sine wave whose frequency is swept in time or a signal similar thereto is transmitted from a terminal station as a monitoring signal and received. At the terminal station, the beats of the supervisory signal and the reference signal returned from a plurality of repeaters are obtained, and the fact that the beat frequency differs depending on the round-trip delay time with each repeater is used to make a predetermined repeat from the return signals. It is a method of monitoring an optical repeater system that separates and detects signals that are returned by a container.

A fifth feature of the method of the present invention is that in the first feature of the method, a pulse having a pulse width narrower than the repeater interval is transmitted from the terminal station as a monitoring signal, and the receiving terminal station communicates with each repeater. This is a monitoring method for an optical repeater system in which a monitoring signal folded back due to a difference in round-trip delay time is temporally separated and detected.

A sixth feature of the method of the present invention is the method according to the fourth or fifth feature, wherein the supervisory signal is pre-modulated by a carrier having a speed sufficiently lower than that of the mains transmission signal, and the mains transmission is carried out by a carrier containing the supervisory signal spectrum. This is a monitoring method for an optical repeater system in which a monitoring signal is transmitted by amplitude-modulating the signal.

The first feature of the circuit of the present invention is that it has an up and down 1
In an optical repeater composed of one set of upstream and downstream optical amplifiers inserted in a pair of optical fiber transmission lines, an upstream and downstream main line transmission signal in which a supervisory signal is superposed on the one set of upstream and downstream optical fiber transmission lines is used. By abutting optical couplers that branch and couple in attenuating manner, the upstream and downstream optical fiber transmission lines intervene over each other, and the upstream and downstream folded signals are converted into the respective downstream downstream and upstream main transmission signals. It is a monitoring loopback circuit of an optical repeater system that can be freely superimposed and fed back.

The second feature of the circuit of the present invention is that a sine wave oscillator that creates a carrier wave, a pseudo-random signal generator that generates an M-sequence PN signal, and a phase that converts the carrier wave into a phase-modulated signal with the PN signal. A modulation circuit, a transmission light source that transmits a communication signal as a main line transmission signal, an optical amplitude modulator that amplitude-modulates the main line transmission signal with the phase modulation signal, and sends a monitoring signal to an upstream optical fiber transmission line, and the upstream A photodetector for converting the returned optical signal groups respectively fed back through the downstream optical fiber transmission lines by the monitoring and folding circuit groups interposed in parallel and in multiple stages between the optical fiber transmission line and the downstream optical fiber transmission line, and the PN. Monitoring and transmitting / receiving of an optical repeater system comprising a variable delay circuit for delaying a signal by a predetermined amount and a correlation detection circuit for synchronizing the folded electric signal with the delayed PN signal. It is a circuit.

A third feature of the circuit of the present invention is that a sweeping oscillator generates a sine wave whose frequency is swept in time or a reference signal corresponding to the sine wave, a transmission light source which emits a communication signal as a main line transmission signal, and the main line. An optical amplitude modulator that performs optical amplitude modulation of a transmission signal with the reference signal and sends a monitoring signal to an upstream optical fiber transmission line, and a parallel multistage interposition between the upstream optical fiber transmission line and the downstream optical fiber transmission line. And a photodetector for converting the returned optical signals, which are respectively fed back through the downstream optical fiber transmission line by the monitoring and returning circuit group, into an electric signal, and a multiplication circuit for multiplying the returned electric signal by the reference signal to generate a beat frequency. And a variable bandpass circuit that tunes the beat frequency and extracts the folded electric signal. That.

A fourth characteristic of the circuit of the present invention is that a pulse signal shorter than a signal propagation time between a sine wave oscillator for generating a carrier wave and an optical repeater of a repeater system has a longer cycle than the round trip delay time of the whole repeater system. A pulse generation circuit for generating, a gate circuit for converting the carrier wave into a pulse modulation signal by the pulse signal, a transmission light source for emitting a communication signal as a main line transmission signal, and an amplitude of the main line transmission signal for the pulse modulation signal. An optical amplitude modulator that modulates and sends a supervisory signal to the upstream optical fiber transmission line, and the downlink optical signal by a monitoring loopback circuit group that is interleaved in parallel and in multiples between the upstream optical fiber transmission line and the downstream optical fiber transmission line. A photodetector that converts the returned optical signals that have been respectively returned through the fiber transmission path into an electrical signal, and a miscellaneous signal of the returned electrical signal. A bandpass filter for removing a monitoring transceiver circuit of the optical relay system comprising a oscilloscope displays and outputs folding electric signal the extracted.

The fifth feature of the circuit of the present invention is that it has an up and down 1
In an optical repeater consisting of one set of upstream and downstream optical amplifiers inserted in a pair of optical fiber transmission lines, an attenuator is interposed in the middle and the upstream and downstream one set of optical fiber transmission lines respectively goes up and down. The main-line transmission signal obtained by modulating and superimposing the above-mentioned monitoring signal is attenuatingly branched, and by connecting the optical couplers that are coupled to each other, the pair of the upstream and downstream optical fiber transmission lines intervenes over each other, and the upstream and downstream folds are returned. It is a monitoring loopback circuit of an optical repeater system in which each signal can be downlinked and superimposed and fed back to an upstream main line transmission signal.

The sixth feature of the circuit of the present invention is that it has an up and down 1
In an optical repeater consisting of a pair of upstream and downstream optical amplifiers inserted in a pair of optical fiber transmission lines, an optical coupler is interposed in the middle so that the passing optical signals can be attenuated, and the upstream and downstream optical pairs Between the above-mentioned one set of optical fiber transmission lines by contacting the optical couplers for branching and coupling the main-line transmission signal and the backscattered light, which are obtained by modulating and superimposing the upstream and downstream supervisory signals on the fiber transmission lines, respectively. It is a monitoring loopback circuit of an optical repeater system, which is interleaved with each other and is capable of superposing and returning an upstream and downstream return signal and a backscattered light to the reverse downstream and upstream main line transmission signals, respectively.

[0020]

Since the present invention has taken the above-mentioned methods and means, the conventional open / close control of the monitoring loopback circuit from the landing station is abolished, and the continuous conduction is monitored through a predetermined optical loss in the repeater. Install a loopback circuit. This eliminates the reception control circuit and the optical shutter, and simplifies the circuit. The predetermined optical loss is attenuated to the extent that the plurality of folded signals do not affect the main line transmission signal.

The receiving terminal station receives a plurality of supervisory signals which are returned from each relay at the same time, and uses various methods of utilizing the difference in propagation time transmitted from the transmitting terminal station to the receiving terminal station via the repeater. , Separates and detects a return signal from a predetermined repeater.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Circuit example 1) A first circuit example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram of an optical repeater system including the monitoring loopback circuit. In the figure, 12a to 12n and 13a
13a to 13n are optical fiber transmission lines constituting upstream and downstream lines, 16a to 16n are repeaters, and 17a to 18n.
Are upstream and downstream optical amplifiers respectively incorporated in the repeaters 16a to 16n, and 19a to 20n are optical amplifiers 17a to 18n.
Optical couplers 21a to 22n, which are respectively installed at the outputs of n for branching and coupling optical signals, 21a to 22n are optical attenuators for giving a predetermined optical loss, and Aa to An are monitoring loop circuits.

As the constitution of the repeaters 16a to 16n, 16n
However, all the repeaters 16a to 16n have the same configuration. Reference numerals 23a and 23b denote transmission terminal stations which are respectively connected to upstream and downstream optical fiber transmission lines and which superimpose a supervisory signal on a communication signal and transmit the signal.
b receives the communication signal returned from each of the repeaters 16a to 16n, and outputs the monitoring signal from each of the repeaters 16a to 16n.
It is a receiving terminal station for separating and detecting each.

(Method Example 1) A case where the first method example of the present invention is applied to the first circuit example will be described. In FIG. 1, the supervisory signal is superimposed on the communication signal by performing amplitude modulation with a small modulation factor, and is transmitted to the optical fiber transmission line 12a. The communication signals are optical amplifiers 17a to 17n of the repeaters 16a to 16n.
Is amplified and relayed by each relay device 16a ...
16n, the optical couplers 19a to 19n branch the optical couplers 20a to 22n, and the optical coupler 20a passes through the optical attenuators 22a to 22n.
~ 20n are coupled to the outputs of the downstream repeaters 16a-16n circuits. The optical couplers 20a to 20n and the optical attenuator 21a are also used for the signal transmitted from the downlink transmission terminal station 23b.
.About.21n, and the optical couplers 19a to 19n return the signals to the upstream optical fiber transmission lines 12a to 12n.

Therefore, for example, in the downlink, each time the communication signal L'is relayed by the repeaters 16a to 16n, the communication signals La to Ln returned from the uplink are added. The downlink spectrum is composed of a downlink communication signal L'and a plurality of folded uplink communication signals La to Ln as illustrated in FIG. For the sake of explanation, the folded communication signals La to Ln are arranged on the wavelength axis in FIG. 2, but actually have the same wavelength. The folded back communication signals La to Ln need to be sufficiently attenuated so as not to adversely affect the downlink communication signal L'as shown in FIG. That is, the installation of the always-on monitoring loopback circuits Aa to An and the design of their attenuation amount are important points of the present invention.

FIG. 3 shows the measurement result of the deterioration of the communication signal with respect to the amount of attenuation. As is clear from this result, considering 300 relays, it is necessary to suppress the power of the return communication signal per location to 40 dB or less with respect to the communication signal power. Since the return signals La to Ln are added one after another, this attenuation amount can be relaxed when the number of relays is small. Since the cumulative effect of 25 dB is obtained with the number of relays of 300 units from FIG. 3,
An arbitrary number of relays is set to 15 dB per unit, and a value obtained by adding 10 LOG (N) dB to the number of relays is set to the minimum required attenuation amount. With such a design, it is possible to avoid deterioration of the characteristics of the communication signal due to the installation of the monitoring loop-back circuits Aa to An that are always in the conductive state.

In FIG. 1, a receiving terminal station receives 300 return communication signals at the same time, for example, in a 300 relay system. Therefore, it is important to separate the return communication signal at the receiving terminal station. The structure of the supervisory signal and the separating means in the receiving circuit will be described below.

Circuit Example 2 A second circuit example of the present invention will be described in detail with reference to the drawings. FIG. 4 is a block diagram of an example of the monitoring transmitting / receiving circuit. In the figure, B is a monitoring transmission / reception circuit of this circuit example, 25 is a sine wave oscillator that is slower than a communication signal, 26 is a pseudo random signal generator that operates at a slower speed than the sine wave oscillator 25, 27
Is a phase modulation circuit, 28 is a transmission light source for transmitting a communication signal,
Reference numeral 29 is an optical amplitude modulator, Aa to An are a plurality of monitoring folding circuits of the first circuit example, 30 is a photodetector of the receiving circuit, 31 is a correlation detecting circuit, and 32 is a variable delay circuit.

(Method Example 2) A case where the second method example of the present invention is applied to the second circuit example will be described. Sine wave oscillator 25
The carrier wave created in step M is a pseudo random signal generator M
The phase is modulated by the series PN signal. This modulated signal amplitude-modulates the main line signal from the transmission light source 28 by the optical amplitude modulator 29. On the other hand, the signals returned by the monitoring return circuits Aa to An are converted into electric signals by the photodetector 30 and then applied to the correlation detection circuit 31.
On the other hand, the PN signal is given a predetermined delay by the variable delay circuit 32 and guided to the correlation detection circuit 31. Since the time required for the return of each of the repeaters 16a to 16n is different,
By adjusting the delay amount, the predetermined relays 16a to 16a-1
The correlation with the return communication signals La to Ln from 6n is obtained.

By changing the delay amount, the correlation with the return signals of the other repeaters 16a to 16n can be obtained. Thereby, the round trip gain (loss) to each of the repeaters 16a to 16n can be measured. An example of the measurement result by this method example is shown in FIG. However, it depends on the following measurement conditions. Carrier frequency: 4.5 MHz PN bit rate: 100 kps Correlation detection circuit 31: Phase adjuster Average value: 10 times (14 sec) 2250 km system (33 km interval) PN = 17

Circuit Example 3 A third circuit example of the present invention will be described in detail with reference to the drawings. FIG. 6 is a block diagram of an example of the monitoring transmitting / receiving circuit. In the figure, C is a monitoring transmission / reception circuit of this circuit example, 33 is a sweep oscillator, 34 is a multiplication circuit, and 35 is a variable band filter. The same elements as those in the second circuit example of FIG. 4 are designated by the same reference numerals.

(Method Example 3) A case where the third method example of the present invention is applied to the third circuit example will be described. Now, the sweep oscillator 33 sweeps the frequency at a constant speed, and the optical amplitude modulator 29 amplitude-modulates the frequency to superimpose it on the communication signal from the transmission light source 28 for transmission. A plurality of folded communication signals La to
After Ln is converted into an electric signal, it is multiplied by the output of the sweep oscillator 33 by the multiplication circuit 34 to generate a difference (beat) frequency. Since this difference frequency is determined by the product of the sweep speed of the sweep oscillator 33 and the round-trip delay time from the repeaters 16a to 16n, its value is different for each folded repeater 16a to 16n. Therefore, by tuning the variable band filter 35 to a predetermined frequency, the desired repeater 16a can be obtained.
The return communication signals La to Ln from ˜16n can be detected.

Circuit Example 4 A fourth circuit example of the present invention will be described in detail with reference to the drawings. FIG. 7 is a block diagram of an example of the monitoring transmitting / receiving circuit. In the figure, D is a monitoring transmission / reception circuit of this circuit example, 36 is a pulse generation circuit that oscillates a pulse that is shorter than the signal propagation time between the optical repeaters 16a to 16n of the relay system at a period that is longer than the round-trip delay time of the entire system, 37 Is a gate circuit, 38
Is a bandpass filter tuned to the sine wave oscillator circuit 25, 39
Is an oscilloscope. The same elements as those in the second embodiment circuit example of FIG. 4 are designated by the same reference numerals.

(Method Example 4) A case where the fourth method example of the present invention is applied to the fourth circuit example will be described. Sine wave oscillator 25
The carrier wave from is modulated in amplitude by the gate circuit 37 by the pulse signal from the pulse generation circuit 36, then amplitude-modulated by the optical amplitude modulator 29, and transmitted to the main line. The plurality of folded communication signals La to Ln are converted into electric signals, and then the bandpass filter 38 removes noise. Since the round-trip propagation times of the respective return communication signals La to Ln are different, pulse signals are displayed in time series for each of the repeaters 16a to 16n.

As described above, in each of the repeaters 16a to 16n, the monitoring loopback circuits Aa to A which are always in the conductive state.
It is possible to sequentially find the round-trip gain (loss) to each of the repeaters 16a to 16n by installing n and separating and detecting by the monitoring transmission / reception circuits B, C, and D.

FIG. 8 is a system monitoring diagram of second to fifth method examples according to the second to fifth circuit examples of the present invention. In this example, up to the repeater 16d shows a predetermined gain, but the repeater 16d
It can be inferred that the gain is reduced at e, and that deterioration is occurring between the repeaters 16d to 16e. In the above description, an example is described in which the optical signal monitoring loopback circuits Aa to An are installed between the outputs of the upstream and downstream repeaters 16a to 16n, but the same effect is not obtained even when they are installed between the inputs. It's clear. Further, it is also possible to provide monitoring folding circuits Aa to An between the input and the output.

Furthermore, an example has been described in which the monitoring loop-back circuits Aa to An are installed in all the repeaters 16a to 16n.
The same effect can be obtained when the devices are installed intermittently or when they are installed alternately up and down. In this case, the monitoring loopback circuit Aa
Needless to say, the loss of An is moderated according to the ratio of intermittent installation. Also, the monitoring loopback circuits Aa to A
Although an example in which a uniform loss is given to n has been described, it is possible to provide a difference in the loss for each section including a plurality of repeaters within the range in which the above-mentioned minimum required loss is satisfied.

Circuit Example 6 Next, a sixth circuit example of the present invention will be described with reference to the drawings. FIG. 9 is a block diagram of an example of this monitoring loopback circuit. In the figure, A'is a monitoring loopback circuit of this circuit example, 12 and 13 are upstream and downstream optical fiber transmission lines, 16 is a repeater, 17 and 18 are optical amplifiers, and 19 and 20 are optical couplers.

Since the specification of the present monitoring loopback circuit example is such a concrete embodiment, since the monitoring loopback circuits Aa-An in the first circuit example of FIG. 1 provide signal attenuation, the optical attenuators 21a-22n are provided. Optical coupler 1
By increasing the branching ratio of 9 and 20, the loss at the time of branching and coupling is increased to give a predetermined loss.

Circuit Example 7 Next, a seventh circuit example of the present invention will be described with reference to the drawings. FIG. 10 is a block diagram of an example of the monitoring loopback circuit. In the figure, A ″ is a monitoring loopback circuit of this circuit example, 12 and 13 are upstream and downstream optical fiber transmission lines, 16 is a repeater, 17 and 18 are optical amplifiers, 19, 20, 40 and 4
1 is an optical coupler. The main monitoring loopback circuit A ″ is a branching / coupling optical coupler 19 which is a combination of a transfer circuit for transferring the upstream main line transmission signal L1 and the backscattered light L2 from the upstream optical fiber transmission line 12 to the downstream optical fiber transmission line 13 or vice versa. ，
20 and intermediate interposition optical couplers 40 and 41.

The specification of the present monitoring loopback circuit example is such a specific embodiment that the upstream main line transmission signal L1 is branched and passes through the a → d of the coupling optical coupler 19 and the intermediate intermediate optical coupling coupler d → The feedback main line signal L1 ′, which is attenuated as necessary, is merged and superimposed on the downstream main line transmission signal L3 from the upstream monitoring loop circuit that branches via a and goes through c → b of the coupling optical coupler 20.

On the other hand, the backscattered light L2 having a loss ratio of, for example, about 20 dB with respect to the upstream main line transmission signal L1 is branched and passes through b → c of the coupling optical coupler 19 and a → b of the intermediate intermediary optical coupler 40 on the way. Branch through the intermediate optical coupler b → a,
The feedback backscattered light L2 ', which is attenuated as desired, is merged and superimposed on the downstream main line transmission signal L3 from the upstream orientation folding circuit passing through c → b of the coupling optical coupler 20.

At this time, the attenuation factors of the branching / coupling optical couplers 19 and 20 are set to, for example, 10 dB, and the intermediate interposition optical couplers 40 and 4 are used.
The feedback main line transmission signal L with the attenuation factor of 1 set to, for example, 30 dB
1'and the returned backscattered light L2 'are both 40d
Designed to decay to B.

[0044]

As described above, the present invention has an extremely simple structure as compared with the prior art and can monitor the occurrence state of system deterioration during operation, so that an economical and highly reliable monitoring system is provided. Can be realized.

[Brief description of drawings]

FIG. 1 is an optical repeater system diagram according to a first circuit example of the present invention.

FIG. 2 is a spectrum diagram of a signal on a line according to the above.

FIG. 3 is a measurement result diagram of the amount of attenuation and the deterioration of a communication signal due to the above.

FIG. 4 is a configuration diagram of a monitoring transmission / reception circuit of a second circuit example of the present invention.

[Fig. 5] Round-trip gain (loss) to each repeater according to the same as above.
FIG.

FIG. 6 is a configuration diagram of a monitoring transmission / reception circuit of a third circuit example of the present invention.

FIG. 7 is a configuration diagram of a supervisory transmission circuit of a fourth circuit example of the present invention.

FIG. 8 is a system monitoring diagram of an example of a monitoring loopback circuit of second to fifth circuit examples of the present invention.

FIG. 9 is a configuration diagram of a monitoring loopback circuit of a sixth circuit example of the present invention.

FIG. 10 is a configuration diagram of a monitoring loopback circuit of a seventh circuit example of the present invention.

FIG. 11 is a configuration diagram showing a monitoring loopback circuit in a relay device of a conventional relay system.

[Explanation of symbols]

Aa to An, A ', A ", 14, 15 ... Monitoring return circuit B, C, D, 24a, 24b ... Monitoring transmission / reception circuit α, 16, 16a to 16n ... Repeater 1, 2 ... Optical shutter 3 ... Control command Reception circuit 4 ... Measurement circuit 5 ... Response signal transmission circuit 6-9 ... Optical branch circuit 10, 11 ... Regeneration relay circuit 12, 12a-12n ... Upstream optical fiber transmission line 13, 13a-13n ... Downstream optical fiber transmission line 17, 18, 17a to 18n ... Optical amplifier 19, 20, 19a to 20n, 40, 41 ... Optical coupler 21a to 22n ... Optical attenuator 23a, 23b ... Transmitting terminal station L ', La to Ln ... Pass signal L1 ... Upstream main line transmission Signal L1 '... Return main line transmission signal L2 ... Backscattered light L2' ... Return backscattered light L3 ... Downstream main line transmission signal 25 ... Sine wave oscillator 26 ... Pseudo-random signal generator 27 ... Phase modulation circuit 8 ... Transmission light source 29 ... Optical amplitude modulator 30 ... Photodetector 31 ... Correlation detection circuit 32 ... Variable delay circuit 33 ... Sweep oscillator 34 ... Multiplication circuit 35 ... Variable band filter 36 ... Pulse generation circuit 37 ... Gate circuit 38 ... Band filter 39 ... Oscilloscope

Continuation of front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location H04B 17/02 D 7170-5K (72) Inventor Hiroharu Wakabayashi 2-3-2 Nishishinjuku, Shinjuku-ku, Tokyo International Telegraph and Telephone Corporation

Claims (12)

[Claims] 1. An optical repeater system using an optical amplifier, wherein a plurality of optical repeaters each consisting of a set of repeater circuits for upstream and downstream are inserted into one set of optical fiber transmission lines for upstream and downstream. All the repeaters, or the respective outputs or inputs of the upstream and downstream repeater circuits in the designated repeater are mutually connected through a moderate loss, and the upstream and downstream optical fiber transmission A part of the signal on the road constitutes a monitoring loopback circuit that is always looped back within each repeater, and sends the monitoring signal to the optical fiber transmission line from the upstream and downstream transmission terminal stations, and all or predetermined The receiving terminal station receives a plurality of supervisory signals that are returned through the supervisory loopback circuit of the repeater, and separates and detects each repeater to monitor the state of the transmission path to each repeater. Special Monitoring method for an optical repeater system that. 2. When the number of repeaters per fiber of the optical repeater system is N, the loss of the loopback circuit of each repeater is preferably larger than the loss amount determined by adding 15 dB to 10 LOG (N) dB. The method for monitoring an optical repeater system according to claim 1. 3. An M-sequence pseudo-random signal whose repetition period is longer than the round-trip delay time of an optical transmission system is transmitted from a terminal station as a monitoring signal, and the receiving terminal station performs correlation detection with the transmission monitoring signal, thereby simultaneously The method for monitoring an optical repeater system according to claim 1, wherein a signal returned by a predetermined repeater is separated and detected from a plurality of received return signals. 4. A sine wave whose frequency is swept in time or a reference signal of a signal similar thereto is transmitted from a terminal station as a monitoring signal, and at the receiving terminal station, a monitoring signal returned from a plurality of repeaters and the above-mentioned. The beat of the reference signal is obtained, and the fact that the beat frequency differs depending on the round-trip delay time with each repeater is used to separate and detect the signal folded by a predetermined repeater from a plurality of folded signals. The method for monitoring the optical repeater system according to claim 1. 5. A pulse having a pulse width narrower than a repeater interval is transmitted from a terminal station as a monitoring signal, and the receiving terminal station temporally separates the returning monitoring signal due to a difference in round-trip delay time with each relay. The optical relay system monitoring method according to claim 1, further comprising: 6. The supervisory signal is pre-modulated by a carrier wave that is sufficiently slower than the main line transmission signal, and the supervisory signal is transmitted by amplitude-modulating the main line transmission signal by a carrier wave containing the supervisory signal spectrum. Item 6. A method for monitoring an optical repeater system according to Item 4 or 5. 7. An optical repeater comprising an up-link and down-link pair of optical amplifiers inserted in an up-link and down-link pair of optical fiber transmission lines, wherein a supervisory signal is superimposed on the up-link and down-link pair of optical fiber transmission lines. The upstream and downstream main line transmission signals are attenuatably branched and attenuated by optical couplers that are coupled to each other, so that the upstream and downstream return signals are interleaved between the pair of upstream and downstream optical fiber transmission lines. A supervisory loopback circuit for an optical repeater system, which is capable of superimposing feedback on reverse downlink and uplink main line transmission signals. 8. A sine wave oscillator for generating a carrier wave, a pseudo-random signal generator for generating an M-sequence PN signal, a phase modulation circuit for converting the carrier wave into a phase modulation signal with the PN signal, and a communication signal for the main line. A transmission light source that transmits as a transmission signal, an optical amplitude modulator that performs amplitude modulation on the main line transmission signal with the phase modulation signal and sends a monitoring signal to an upstream optical fiber transmission line, the upstream optical fiber transmission line and the downlink A photodetector for converting the returned optical signal groups respectively fed back through the downlink optical fiber transmission line by a monitoring and folding circuit group interposed in parallel multistages between the optical fiber transmission lines and the PN signal to a predetermined delay. A monitor transmission / reception of an optical repeater system comprising a variable delay circuit and a correlation detection circuit for synchronizing the folded electric signal with the delayed PN signal. Circuit. 9. A swept oscillator that generates a reference signal of a sine wave whose frequency is swept in time or a signal equivalent thereto, a transmission light source that emits a communication signal as a main line transmission signal, and the reference signal for the main line transmission signal. An optical amplitude modulator that performs optical amplitude modulation with and sends a monitoring signal to the upstream optical fiber transmission line,
A photodetector for converting the folded optical signals respectively fed back through the downlink optical fiber transmission line by the monitoring folding circuit group interposed in parallel multistage between the upstream optical fiber transmission line and the downstream optical fiber transmission line, and ,
An optical repeater system comprising: a multiplication circuit that multiplies the folding electric signal by the reference signal to generate a beat frequency; and a variable bandpass circuit that tunes to the beat frequency and extracts the folding electric signal. Supervisory transceiver circuit. 10. A sine wave oscillator for generating a carrier wave, and a pulse generation circuit for generating a pulse signal shorter than a signal propagation time between optical repeaters of a repeater system at a longer cycle by a round trip delay time of the whole repeater system, A gate circuit that changes the amplitude of the carrier wave into a pulse-modulated signal by the pulse signal, a transmission light source that emits a communication signal as a main-line transmission signal, and an amplitude modulation of the main-line transmission signal by the pulse-modulated signal to raise a monitoring signal. The optical amplitude modulator for sending to the optical fiber transmission line, and the feedback loop circuit group interposing in parallel and in multiple stages between the upstream optical fiber transmission line and the downstream optical fiber transmission line, are respectively fed back through the downstream optical fiber transmission line. Photodetector for converting a folded optical signal into an electric signal, and a bandpass filter for removing noise of the folded electric signal Monitoring transceiver circuit of the optical relay system is characterized in that a oscilloscope displays and outputs folding electric signal the extracted. 11. An optical repeater consisting of an upstream and a downstream optical amplifier inserted in an upstream and a downstream optical fiber transmission line, wherein an optical attenuator is provided in the middle and said upstream and downstream one set. By connecting optical couplers for attenuating and branching main line transmission signals, which are respectively modulated and superposed with upstream and downstream supervisory signals, to the optical fiber transmission lines of A supervisory loopback circuit for an optical repeater system, characterized in that an interleaved upstream and downstream loopback signal can be superimposed and fed back to a reverse downlink and upstream mainline transmission signal. 12. An optical repeater comprising an upstream and downstream optical amplifier set inserted into an upstream and downstream optical fiber transmission line, and an optical coupler is interposed between the optical couplers so that the passing optical signals can be attenuated. In addition, by ascending and descending the main transmission signal and the backscattered light obtained by modulating and superimposing the upstream and downstream supervisory signals respectively on the pair of upstream and downstream optical fiber transmission lines, the upstream and downstream are coupled by abutting optical couplers,
An optical repeater system characterized by interposing a pair of optical fiber transmission lines in a downward direction, and allowing an upturned signal and a backscattered light of the upward direction to be superimposed and fed back to reverse downward and upstream main line transmission signals. Monitoring loopback circuit.