JP2858593B2 - Breakpoint locating method and breakpoint locating device for optical repeater transmission system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of locating a break point of a transmission line (optical fiber) in an optical repeater transmission system using a non-regenerative repeater (1R repeater) having an optical amplification function. And a break point locating device.

[0002]

2. Description of the Related Art When light propagates in an optical fiber, backscattered light having the same frequency as the light is generated and propagates in the opposite direction. When pulsed light is input to a broken optical fiber,
Since the backscattered light having the same frequency as the pulsed light continues to be generated until the pulsed light reaches the breaking point, by measuring the duration of the backscattered light emitted from the input end face of the pulsed light, the breaking point is measured. Can be determined.

FIG. 6 is a block diagram showing a configuration example of a conventional break point locating device in an optical repeater transmission system having a 1R repeater. Here, two terminal stations 61, 6
Between the two terminals, a line transmitting signal light from one terminal station 61 to the other terminal station 62 will be referred to as an up line 71, and a line transmitting signal light in the opposite direction will be referred to as a down line 72. Further, a method of locating a break point performed by the terminal station 61 will be described as an example.

[0006] A plurality of repeaters 65 are provided between the terminal stations 61 and 62. Each repeater 65 has optical amplifiers 66 and 67 for compensating the attenuation of the signal light in the respective transmission directions. Incidentally, each of the optical amplifiers 66 and 67 usually has an isolator for preventing oscillation, but this isolator limits the propagation of light to only one direction. Therefore, in order to locate a break point by backscattered light in an optical repeater transmission system having such a 1R repeater, it is necessary to secure a transmission path for this backscattered light. It is also necessary to compensate for the attenuation of the backscattered light.

The break point locating circuit 68 responds to such a demand, and the break point locating circuit 6 corresponding to the up line 71 is provided.
8, the upstream side 71 and the downstream line 7 are connected via an optical switch 69 which is opened and closed by remote control at the output side of the optical amplifier 66.
2 and the backscattered light generated on the upstream line from the optical amplifier 66 on the terminal station 62 side to the optical amplifier 67 on the downstream line 72.
This is a configuration in which the light is incident on. This backscattered light is transmitted to the terminal station 61 via each repeater. Also, the downlink 7
The same applies to the two corresponding break point locating circuits 68.

A procedure for locating the break point 73 when a break occurs in the uplink line 71 between the n- _th repeater 65 _n and the (n + 1) -th repeater 65 _{n + 1} will be described below. . (1) The optical switch 69 of the break point locating circuit 68 on the terminal station 62 side of the n-th stage repeater 65 _n is closed by remote control. (2) The optical amplifier operating point control light (laser light) 81 is input from the terminal station 62 to the downlink 72, and each optical amplifier 67 on the downlink 72 is operated in the saturation region. Thereby, the intensity of the spontaneous emission light, which is one of the causes of the deterioration of the positioning accuracy, is reduced. (3) In the light source 63 for exploring the break point of the terminal station 61, the frequency f ₀
Giving short frequency shift in the laser beam of, as shown in FIG. 7, for generating light to be only the frequency f ₁ briefly. This light is divided into two, and one of them is incident on the up line 71 as the search light 82. The other light enters the backscattered light measurement circuit 64 as local light 83. (4) The search light 82 is transmitted from the _n-th repeater 65 _n to the uplink 7
1, the n-th stage repeater 65 _n and the breaking point 73
Back scattered light 84 generated on the up line 71 between
The light enters the down line 72 via the break point locating circuit 68. When the search light 82 having the frequency f ₀ is constantly incident on this section, the frequency of the backscattered light 84 also becomes f
It becomes ₀ . Here, when the search light 82 of the frequency f ₁ is incident on the uplink 71 from the repeater 65 _n for a short time, the backscatter of the frequency f ₁ is continued until the search light 82 reaches the break point 73. Light 84 is generated. (5) The n-th stage repeater 65 _n and the breaking point 7
The backscattered light 84 having the frequency f ₁ generated on the upstream line 71 between the terminal 3 and the terminal 3 is amplified by the optical amplifier 67 of the repeater 65 _n and reaches the terminal station 61 via the downstream line 72. Here, V is the speed of light in the optical fiber, L is the distance between the repeater 65 _n of the n-th stage and the break point 73, and T is the duration of the backscattered light 84 at the frequency f ₁ detected by the terminal station 61. Then, since L = 2VT, the duration T of the backscattered light 84 having the frequency f ₁ is obtained.
Is measured, the break point 73 can be located. (6) In the backscattered light measuring circuit 64 of the terminal station 61, the frequency f
_One backscattered light 84 is heterodyne-detected using the local light 83 having a frequency f ₀ , and a beat signal having a frequency | f ₀ −f ₁ | is generated. Beat signal, as shown in FIG. 8, the amplitude is changed according to the duration of the backscattered light 84 of frequency f _1. The beat signal is transmitted from the downlink 72 to the terminal 61.
It occurs only when the back-scattered light 84 of frequency f ₁ is incident on. That is, it is possible to measure the duration T of the backscattered light 84 of frequency f ₁ by the duration of the beat signal. Therefore, a constant 2V is applied to the duration of the beat signal.
, The n-th stage repeater 65 _n and the breaking point 7
3 is calculated, and the break point 73 can be located.

[0007]

As described above, in the conventional break point locating device, for example, the backscattered light 84 generated on the up line 71 is transmitted using the down line 72 and the up line 7 is transmitted.
1 in order to reduce the intensity of spontaneous emission light of the optical amplifier 67 on the downlink 72, the optical amplifier operating point control light 81 is transmitted from the opposing terminal 62 to the downlink 72. And each optical amplifier 67 is operated in the saturation region.

However, when a break occurs in the optical fiber, both the upstream line 71 and the downstream line 72 may be broken. In this case, the transmission of the optical amplifier operating point control light 81 emitted from the terminal station 62 is performed. Becomes impossible. Therefore, it is inevitable that spontaneous emission light increases from the downlink 72 to the terminal station 61 and the breakpoint location accuracy deteriorates (IEICE technical report OCS89-6).
1, p.47).

The present invention provides a method and an apparatus for locating a breakpoint in an optical repeater transmission system capable of locating the breakpoint with high accuracy even when the breakpoint is present on both the uplink and the downlink. The purpose is to do.

[0010]

According to a first aspect of the present invention, there is provided a method for locating a break point, comprising: transmitting a search light having a binary frequency via an uplink including an optical amplifier of a repeater, and responding to the search light. A part of the backscattered light generated in the above manner is taken out and incident on the downlink as the forward propagating light, and the backscattered light is transmitted through the downlink including the optical amplifier of the repeater, and one of the search lights Measure the duration of the backscattered light having the frequency of, in the break point locating method of the optical repeater transmission system for locating the break point of the uplink, a part of the probe light propagating forward in the uplink. It is taken out and enters the downlink as its forward propagating light, performs optical amplifier control on the downlink of the repeater, takes in the search light and the backscattered light from the downlink, and uses the search light to Scattered light It performed Rodain detection, and measuring the duration of the backscattered light having one of the frequency of the probe light.

The method of locating a break point according to claim 2, wherein the search light having a binary frequency is transmitted through an uplink including an optical amplifier of a repeater, and the search light propagates forward in the uplink. A part of the light is extracted and incident on the downlink as its forward propagating light, the optical amplifier is controlled on the downlink of the repeater, and a part of the search light propagating in the uplink in the forward direction is extracted. Incident on the downlink as its backward propagating light, and transmits backscattered light generated in response to the search light incident on the downlink in the reverse direction via the downlink including the optical amplifier of the repeater. Capturing the search light and the backscattered light from the downlink, performing heterodyne detection of the backscattered light with the search light, and measuring the duration of the backscattered light having one frequency of the search light. Break of the down line And performing orientation.

According to a third aspect of the present invention, there is provided a break point locating apparatus including a repeater including an optical amplifier for amplifying and emitting an incident signal light, and an uplink and a downlink for transmitting the signal light via the repeater. And generating a search light having a binary frequency,
A light source for rupture point detection emitted to the up line and a part of backscattered light generated according to the search light are taken out, and the first
A first optical circuit that is made to enter the downlink as the forward propagating light through the optical switch, and of the backscattered light that is incident through the first optical circuit and the downlink,
A break point locating device for an optical repeater transmission system, comprising: a duration of backscattered light having one frequency of the exploration light, and a backscattered light measuring circuit for locating the break point of the uplink. A part of the search light propagating in the line in the forward direction is taken out, and is incident on the downlink as the forward propagation light through the second optical switch, and the optical amplifier on the downlink of the repeater is controlled. 2 optical circuits, and optical switch control means for opening and closing the first optical switch and the second optical switch, wherein the backscattered light measurement circuit is configured to transmit the search light and the backscattered light from the downlink. And the heterodyne detection of the backscattered light is performed by the search light, and the duration of the backscattered light having one frequency of the search light is measured.

According to a fourth aspect of the present invention, there is provided a break point locating apparatus including a repeater including an optical amplifier for amplifying and emitting an incident signal light, and an uplink and a downlink for transmitting the signal light via the repeater. In an optical repeater transmission system having
A search light having a frequency of a value is generated, and a light source for break point detection emitted to the uplink and a part of the search light propagating in the uplink in the forward direction are taken out, and are extracted via the first optical switch. A first optical circuit that controls the optical amplifier on the downlink of the repeater by injecting it into the downlink as its forward propagating light, and extracts a part of the search light propagating in the forward direction of the uplink. A second optical circuit for entering the downstream line as the backward propagating light through a second optical switch, an optical switch control means for opening and closing the first optical switch and the second optical switch, The search light and the backscattered light generated according to the search light are taken in from the line, heterodyne detection of the backscattered light is performed by the search light, and the backscattered light having one frequency of the search light is detected. Measure the duration Characterized by comprising a rear scattered light measurement circuit for performing break orientation of said downlink channel.

According to a fifth aspect of the present invention, there is provided a break point detecting light source used in the break point locating device, a laser light source capable of varying the frequency of output light in accordance with a frequency control signal, and a pulse having a predetermined length. Pulse generating means for transmitting the frequency control signal to the laser light source to generate continuous search light having a binary frequency corresponding to the pulse.

The backscattered light measuring circuit used in the break point locating device according to claim 6 captures the search light and the backscattered light, performs heterodyne detection of the backscattered light with the search light, and detects a back light of a predetermined frequency. The backscattered light measuring circuit used in the break point locating device according to claim 3 or 4, which measures the duration of the scattered light, wherein the polarization plane of the backscattered light and the search light is rotated according to a control signal. Branching means for splitting the signal light into two light components of each polarization component, and the control for detecting the light intensity of the signal light split for each polarization component and setting the amount of rotation of the polarization plane for equalizing each light intensity A polarization plane control means for outputting a signal, a polarization diver for taking in the signal light branched for each polarization component, performing heterodyne detection of the backscattered light with the search light, and adding and outputting a detection signal. Characterized by comprising a cytidine detecting means.

[0016]

The break point locating method and the break point locating apparatus according to the first and third aspects are capable of causing a part of the search light propagating in the up line to enter the down line together with the backscattered light. Part of the light can be used as operating point control light for an optical amplifier on the downlink. Therefore, even if a break occurs in both the upstream line and the downstream line, the optical amplifier of each repeater on the downstream line that propagates backscattered light can operate in the saturation region, thereby avoiding a decrease in the break point locating accuracy. can do.

According to a second aspect of the present invention, there is provided a break point locating method and a break point locating apparatus, in which a part of an exploration light propagating in an up line is incident on a down line in a forward direction and a backward direction, and the down line is transmitted. Backscattered light corresponding to the search light propagating in the backward direction is propagated together with the search light propagating in the forward direction. Therefore, a part of the search light can be used as operating point control light of the optical amplifier on the downlink, and the break point of the downlink can be located.

According to the fifth aspect of the present invention, the light source for detecting a break point can generate continuous search light having a binary frequency corresponding to a pulse having a predetermined length. The backscattered light measuring circuit according to claim 6, wherein the polarization planes of the backscattered light and the search light are rotated to make the light intensities of the signal lights branched for each polarization component equal to each other, and a polarization diversity detection means. By performing the heterodyne detection processing respectively, it is possible to efficiently detect even if the polarization plane of the backscattered light and the search light is in an arbitrary state.

[0019]

FIG. 1 is a block diagram showing the configuration of an embodiment of a break point locating device according to a third aspect of the present invention. The feature of the present embodiment lies in the configuration of the break point locating circuit 10, and the other configuration is the same as that of the conventional break point locating apparatus shown in FIG.

In FIG. 1, a break point locating circuit 10 is composed of optical couplers 11, 12, and 13 and two optical switches 14 that are linked. The optical coupler 11 has an uplink 71
Is extracted from the optical amplifier 66 in accordance with the search light 82 and the backscattered light 84 generated in the uplink on the terminal station 62 side. Two optical switches 14
Controls the passage of the search light 82 and the backscattered light 84 extracted by the optical coupler 11. The optical coupler 12 couples the search light 82 and the backscattered light 84 that have passed through the optical switch 14. The optical coupler 13 causes the coupled search light 82 and backscattered light 84 to enter the downlink 72 as its forward propagating light.

The conventional break point locating circuit 68 has a configuration in which only the backscattered light 84 is incident on the down line 72.
The optical coupler 11, the optical switch 14, and the optical coupler 13 correspond thereto. In this embodiment, the first
The optical circuit and the second optical circuit are connected to optical couplers 11, 12, 1
This is an example realized by a break point locating circuit 10 composed of the optical switch 3 and an optical switch 14.

In the break point locating device using such a break point locating circuit 10, the n-th repeaters 65 _n and n + 1
A procedure for locating the break point 73 when a break occurs in the up line 71 with the repeater 65 _{n + 1} of the stage will be described. (1) The optical switch 14 of the break point locating circuit 10 on the repeater 65 _{n + 1} side of the repeater 65 _n of the n-th stage is closed by remote control. (2) In the light source 63 for exploring the breaking point of the terminal station 61, the frequency f ₀
A short-time frequency shift is given to the laser light, and light having a frequency f ₁ is generated for a short time as shown in FIG. (3) When the search light 82 arriving at the _n-th repeater 65 _n is emitted to the up line 71, the n-th repeater 65 _n (more precisely, the optical coupler 11 of the break point locating circuit 10) Breaking point 73
Back scattered light 84 generated on the up line 71 between
The light enters the down line 72 via the break point locating circuit 10. Similarly, when the search light 82 having the frequency f ₁ is incident on the uplink 71 from the repeater 65 _n for a short time, the frequency f ₁ is maintained until the search light 82 reaches the break point 73.
_One backscattered light 84 is generated.

(4) In the break point locating circuit 10, the search light 82
Is input to the downlink 72, and each optical amplifier 67 on the downlink 72 is operated in the saturation region. Thereby, the intensity of the spontaneous emission light, which is one of the causes of the deterioration of the positioning accuracy, is reduced. Note that the folded search light 82 is used as local light when the backscattered light 84 is heterodyne-detected by the backscattered light measurement circuit 64. (5) The n-th stage repeater 65 _n and the breaking point 7
Backscattered light 84 of a frequency f ₁ generated on the uplink 71 between 3 is amplified by the optical amplifier 67 in the repeater 65 _n, so it reaches the terminal station 61 via the downlink 72, similarly By measuring the duration T of the backscattered light 84 at the frequency f ₁ , the break point 73 can be located. (6) In the backscattered light measuring circuit 64 of the terminal station 61, the frequency f
_One backscattered light 84 is heterodyne-detected using the search light 82 having the frequency f ₀ to generate a beat signal having a frequency | f ₀ −f ₁ |. Accordingly, similarly, the duration T of the backscattered light 84 having the frequency f ₁ is determined by the duration of the beat signal.
Can be measured, the distance L between the _n- th stage repeater 65 _n and the break point 73 is calculated, and the break point 73 can be located.

FIG. 2 is a block diagram showing an embodiment of the break point locating device according to the present invention. The feature of the present embodiment lies in the configuration of a break point locating circuit 20 which enables the break point 74 of the downlink 72 to be located from the terminal station 61 side. Since it is the same as the orientation device, the same reference numerals are given and the description is omitted.

In FIG. 1, the break point locating circuit 20 is a circuit shown in FIG.
Is configured such that the break point locating circuit 10 of the embodiment shown in FIG. 1 is connected upside down with respect to the up line 71 and the down line 72, and the optical couplers 21, 22, 23 and the
It is composed of two optical switches 24. Optical coupler 21
Extracts the search light 82 propagating in the forward direction on the uplink 71. The optical coupler 22 splits the search light 82 extracted by the optical coupler 11 into two and outputs it. Two optical switches 14
Controls the passage of the search light 82 branched into two. The optical coupler 23 causes one of the search lights 82 to enter the downlink 72 as its backward propagating light, and causes the other search light 82 to enter the downlink 72 as its forward propagating light.

In this embodiment, the first optical circuit and the second optical circuit according to claim 4 are connected to optical couplers 21, 22, 23.
This is an example realized by a break point locating circuit 20 constituted by the optical switch 24 and the optical switch 24. In the break point locating device using such a break point locating circuit 20, when a break occurs in the downlink 72 between the n-th stage repeater _65n and the (n + 1) th stage repeater _{65n + 1.} The procedure for locating the break point 74 from the terminal station 61 side will be described. (1) The optical switch 24 of the break point locating circuit 20 on the repeater 65 _{n + 1} side of the repeater 65 _n of the n-th stage is closed by remote control. (2) In the light source 63 for exploring the breaking point of the terminal station 61, the frequency f ₀
A short-time frequency shift is given to the laser light, and light having a frequency f ₁ is generated for a short time as shown in FIG. (3) When the search light 82 that has reached the _n- th stage repeater 65 _n is emitted to the downlink 72 via the break point locating circuit 20, the n-th stage repeater 65 _n (exactly, the break point Orientation circuit 20
The backscattered light 84 generated on the downlink 72 between the optical coupler 23) and the breaking point 74 propagates in the downlink 72 in the forward direction. Similarly, when the search light 82 having the frequency f ₁ is incident on the downlink 72 from the repeater 65 _n for a short time,
Until this probe light 82 reaches the break point 74, the backscattered light 84 of frequency f ₁ is generated.

(4) In the break point locating circuit 10, the search light 82
Is input in the forward direction of the downlink 72, and the downlink 7
2 is operated in the saturation region. Thereby, the intensity of the spontaneous emission light, which is one of the causes of the deterioration of the positioning accuracy, is reduced. Note that the folded search light 82 is used as local light when the backscattered light 84 is heterodyne-detected by the backscattered light measurement circuit 64. (5) The n-th stage repeater 65 _n and the breaking point 7
The backscattered light 84 of a frequency f ₁ generated on the downlink 72 between the 4, is amplified by the optical amplifier 67 in the repeater 65 _n, so it reaches the terminal station 61 via the downlink 72, similarly By measuring the duration T of the backscattered light 84 at the frequency f ₁ , the break point 74 can be located. (6) In the backscattered light measuring circuit 64 of the terminal station 61, the frequency f
_One backscattered light 84 is heterodyne-detected using the search light 82 having the frequency f ₀ to generate a beat signal having a frequency | f ₀ −f ₁ |. Accordingly, similarly, the duration T of the backscattered light 84 having the frequency f ₁ is determined by the duration of the beat signal.
Can be measured, the distance L between the _n- th stage repeater 65 _n and the break point 74 is calculated, and the break point 74 can be located.

FIG. 3 is a block diagram showing the configuration of an embodiment of a light source for detecting a break point used in the break point locating apparatus according to the present invention. In the figure, a break point detecting light source includes a distributed feedback semiconductor laser (DFB-LD) 31 capable of changing the frequency of output light according to a frequency control signal;
A pulse generator 32 for generating a pulse signal of a predetermined length and transmitting the pulse signal to the DFB-LD 31 as a frequency control signal;

The DFB-LD 31 performs frequency modulation by a pulse signal output from the pulse generator 32, generates a search light with a frequency f _{0 when} no pulse signal is input, and searches for a frequency f ₁ when a pulse signal is input. Generates light.
Therefore, it is possible to continuously generate search light having a binary frequency according to the pulse signal. FIG. 4 is a block diagram showing the configuration of an embodiment of the backscattered light measuring circuit used in the break point locating device of the present invention.

In the figure, a backscattered light measuring circuit uses a probe light incident from the down-link as local light, and performs a heterodyne detection of simultaneously incident backscattered light, and outputs from the receiver 41. Analog-to-digital converter (A
/ D) 42 and a computer 43 for processing digital signals.

The beat signal obtained by the heterodyne detection in the receiver 41 is converted into a digital signal,
, And calculating the duration of the beat signal, the break point can be located based on a predetermined calculation method. FIG. 5 is a block diagram showing an embodiment of a receiver used in the backscattered light measuring circuit according to the present invention.

Note that the planes of polarization of the backscattered light and the search light that enter the receiver do not always match. On the other hand, the frequency f ₀
When the performing heterodyne detection of the backscattered light of the frequency f ₁ with a probe light receiving efficiency to be detected each light in a state where the polarization is matched exploration light and backscattered light is deteriorated. This embodiment is characterized in that even if the respective polarization planes of the backscattered light and the search light are respectively incident on the receiver at arbitrary angles, the polarization planes are adjusted and used for heterodyne detection.

In the figure, the frequency f incident on the receiver
The backscattered light of ₁ and the search light of the frequency f ₀ are amplified by the optical amplifier 51. The amplified backscattered light and search light are incident on a polarized light demultiplexer (PBS) 53 by rotating the plane of polarization by a polarization controller 52, and are split into two lights of each polarization component. The light of each polarization component is P
IN photodiodes are incident on the _{(PIN-PD) 54 1,} 54 2 is converted into an electric signal. Although the DC component of the output current of each PIN photodiode is proportional to the intensity of the incident light, the intensity of the search light is sufficiently larger than the intensity of the backscattered light, so that the output current of each PIN photodiode is The DC component is proportional to the search light intensity.

The comparator 55 compares the DC components of the output currents of the PIN photodiodes, and performs feedback control of the polarization plane rotated by the polarization controller 52 so that they become equal. Therefore, the intensity of the search light incident on the _two PIN photodiodes 54 ₁ and 54 ₂ can be made equal. Each PIN photodiode 54
_1, 54 ₂ of the output signal, only the beat signal of a frequency | F ₀ -f ₁ │ arising respectively band pass filter (BPF) 56 _1, 56 ₂ via the back-scattered light by probe light are filtered, orientation precision A noise component that causes deterioration is reduced. Each beat signal is respectively supplied to an envelope detection circuit 57
_1, 57 ₂ is inputted is demodulated, the demodulated signal is output are added are inputted to the adder circuit 58.

As described above, by adopting a polarization diversity configuration in which the intensity of the search light incident on the _two PIN photodiodes 54 ₁ and 542 is equalized and the detection processing is performed, the polarization plane of the backscattered light and the search light is obtained. Are mismatched,
Heterodyne detection of backscattered light can be performed efficiently.

[0036]

As described above, according to the present invention, in an optical repeater transmission system having a 1R repeater, even if a break occurs in both the uplink and the downlink, the processing from one of the terminal stations provides high accuracy. The break point can be located.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a break point locating device according to claim 3;

FIG. 2 is a block diagram showing an embodiment configuration of a break point locating device according to a fourth embodiment.

FIG. 3 is a block diagram showing an embodiment configuration of a light source for rupture point detection used in the rupture point locating apparatus of the present invention.

FIG. 4 is a block diagram showing an embodiment of a backscattered light measuring circuit used in the break point locating apparatus of the present invention.

FIG. 5 is a block diagram showing an embodiment of a receiver used in the backscattered light measuring circuit of the present invention.

FIG. 6 is a block diagram showing a configuration example of a conventional break point locating device in an optical repeater transmission system having a 1R repeater.

FIG. 7 is a diagram showing a time change of the frequency of the search light.

FIG. 8 is a diagram showing a temporal change in the amplitude of a beat signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Break point locating circuit 11, 12, 13 Optical coupler 14 Optical switch 20 Break point locating circuit 21, 22, 23 Optical coupler 24 Optical switch 31 Distributed feedback semiconductor laser (DFB-LD) 32 Pulse generator 41 Receiver 42 Analog・ Digital converter (A / D) 43 Computer 51 Optical amplifier 52 Polarization controller 53 Polarized light splitter (PBS) 54 PIN photodiode (PIN-PD) 55 Comparator 56 Bandpass filter (BPF) 57 Envelope detection Circuit 58 Addition circuit 61, 62 Terminal station 63 Light source for break point detection 64 Backscattered light measurement circuit 65 Repeater 66, 67 Optical amplifier 68 Break point locating circuit 69 Optical switch 71 Up line 72 Down line 73, 74 Break point 81 Light Amplifier operating point control light 82 Exploration light 83 Local light 84 Backscattered light

Continuation of the front page (51) Int.Cl. ⁶ identification symbol FI H04B 17/02 G02B 6/00 A (56) References JP-A-3-9625 (JP, A) JP-A-2-2228 (JP, A JP-A-64-75932 (JP, A) JP-A-64-46627 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04B 10/08-10/24

Claims (6)

(57) [Claims] An exploration light having a binary frequency is transmitted through an upstream line including an optical amplifier of a repeater, a part of backscattered light generated according to the exploration light is extracted, and the extracted back light is transmitted to a downstream line. Incident as forward propagating light, transmitting the backscattered light through a downlink including the optical amplifier of the repeater, measuring the duration of the backscattered light having one frequency of the search light, In the breakpoint locating method of the optical repeater transmission system for performing the breakpoint locating of the line, a part of the search light propagating in the forward direction in the up line is taken out and is incident on the down line as the forward propagating light, Control the optical amplifier on the downlink of the repeater, take in the search light and the backscattered light from the downlink, perform heterodyne detection of the backscattered light with the search light, and change one frequency of the search light. Have And measuring a duration of the backscattered light. 2. A search light having a binary frequency is transmitted through an upstream line including an optical amplifier of a repeater, and a part of the search light propagating in the forward line in the forward direction is taken out to a downstream line. It enters as the forward propagating light, performs optical amplifier control on the downlink of the repeater, extracts a part of the search light propagating in the uplink in the forward direction, and extracts the backward propagating light in the downlink. And transmitted through a downlink including an optical amplifier of the repeater, the backscattered light generated in response to the search light incident on the downlink in the opposite direction, and the search light and the Introducing backscattered light, performing heterodyne detection of the backscattered light with the search light, measuring the duration of the backscattered light having one frequency of the search light, and locating the break point of the downlink. Optical relay characterized by The method of locating the break point of the transmission system. 3. A repeater including an optical amplifier for optically amplifying and emitting an incident signal light, an uplink and a downlink for transmitting the signal light via the repeater, and a search light having a binary frequency. And a part of the backscattered light generated in response to the search light and a part of the backscattered light emitted according to the search light are extracted and forward-propagated to the downlink via a first optical switch. A first optical circuit for entering as light,
A backscattered light measurement circuit that measures the duration of the backscattered light having one frequency of the search light out of the backscattered light emitted from the downlink and performs break point localization of the uplink. In the break point locating device of the optical repeater transmission system, a part of the search light propagating in the up line in the forward direction is taken out, and made incident on the down line as the forward propagation light through the second optical switch. A second optical circuit for controlling an optical amplifier on the downlink of the repeater; and an optical switch control means for opening and closing the first optical switch and the second optical switch; ,
Incorporating the search light and the backscattered light from the downlink, performing heterodyne detection of the backscattered light with the search light, and measuring the duration of the backscattered light having one frequency of the search light. An apparatus for locating a break point in an optical repeater transmission system. 4. An optical repeater transmission system comprising: a repeater including an optical amplifier that amplifies and emits an incident signal light, and an uplink and a downlink that transmits the signal light via the repeater. A search light having a binary frequency is generated, and a light source for break point detection emitted to the uplink and a part of the search light propagating in the uplink in the forward direction are taken out, and are extracted through a first optical switch. A first optical circuit that controls the optical amplifier on the downlink of the repeater by causing the light to enter the downlink as its forward propagating light, and extracts a part of the search light propagating in the forward direction of the uplink. A second optical circuit that causes the light to enter the downstream line as the backward propagating light via a second optical switch, an optical switch control unit that opens and closes the first optical switch and the second optical switch, From the downlink, The search light and the back scattered light generated in response to the search light are taken in, the heterodyne detection of the back scattered light is performed by the search light, and the duration of the back scattered light having one frequency of the search light is determined. A backscattering light measuring circuit for measuring and measuring a break point of the downlink line. 5. A laser light source capable of changing the frequency of output light in accordance with a frequency control signal, and a pulse of a predetermined length is generated.
4. A pulse generating means for transmitting the pulse as the frequency control signal to the laser light source, and generating a continuous search light having a binary frequency corresponding to the pulse. Item 6. A light source for detecting a break point used in the break point locating apparatus according to Item 4. 6. A search light and a backscattered light are taken in, and heterodyne detection of the backscattered light is performed by the search light.
The backscattering light measuring circuit used in the break point locating device according to claim 3 or 4, wherein the duration of the backscattering light having a predetermined frequency is measured. A branching unit that splits the signal light of each polarization component into two after rotating the wavefront, and a polarization plane rotation amount that detects the light intensity of the signal light branched for each polarization component and equalizes each light intensity The polarization plane control means for outputting the control signal and setting the signal light branched for each polarization component, respectively, performs heterodyne detection of the backscattered light by the search light, and adds the detection signals. A backscattered light measuring circuit, comprising: a polarization diversity detecting means for outputting.