Measurement method by OTDR and terminal station apparatus

The present invention relates to a technique for measuring a loss distribution in the longitudinal direction of a transmission line in an optical transmission system using an OTDR (Optical Time Domain Reflectometry).

[0002] Conventional Technique As an optical fiber test technique, an optical pulse is incident on an optical fiber and the intensity of backscattered light is observed temporally, so that the distance distribution and obstacle points of the propagation loss of the optical fiber are observed. There is an OTDR (Optical Time Domain Reflectometry) that detects OTDR.

[0003] In a transmission system using an optical fiber, there are a relay system in which repeaters are installed at regular intervals on a transmission line connecting both ends of a station for communication, and a repeater on a transmission line connecting both ends of a station. There is a non-relay system that communicates without installing a repeater, but in the relay system, it is possible to configure a long-distance optical transmission system by performing optical amplification with EDF (Elbium-doped optical fiber) at each repeater. Is. In addition, in the relay system, it is possible to perform long-distance measurement across repeaters by using a C-OTDR that performs coherent detection.

[0004] On the other hand, although the non-relay system can configure an inexpensive system, it does not perform relay transmission, so that the distance that can be transmitted is limited even if Raman amplification is used, and the distance that signal light for OTDR can be transmitted. There are also restrictions on the measurable distance from the terminal station where the OTDR device is installed. Further, as one form of the non-relay system, a remote excitation system is used in which a remote amplifier using EDF is inserted on a transmission line at a predetermined distance from the terminal station to extend the transmittable distance. However, looking at this method from the perspective of measurement by OTDR, the wavelength in the 1550 nm band, which is generally used for OTDR light, has a large absorption loss due to EDF, so the loss distribution beyond EDF when viewed from the end station performing OTDR. Was difficult to measure. Even if the 1650 nm band, which is the band that transmits EDF, is used, the loss due to the optical fiber is large in the 1650 nm band, so that the S / N ratio becomes poor and it is difficult to measure the loss distribution over a long distance.

[0005] [Non-Patent Document 1] Huai H. Kee et al. Extended-range optical time domain-reflectometry system at 1.65 μm based on delayed Raman amplification, Optical Letters Vol.23, No.5 March 1, 1998, pp.249-351 [0006] [Non-Patent Document 2] E. Cotton et al. DYNAMIC RANGE INCREASE OF 1625 nm MONITORING SYSTEMS, International Wire & Cable Symposium Proceedings 1995, pp.654-661 [0007] [Invention Problem to be solved As described above, the non-relay optical transmission system has a problem that the loss distribution of the optical transmission line over a long distance cannot be measured by OTDR.

[0008] The present invention has been made in view of the above points, and an object of the present invention is to provide a technique for measuring a long-distance span by OTDR in an optical transmission system.

[Means for Solving the Problems] The present invention solves the above problems in an optical transmission system having a first terminal station and a second terminal station, and an OTDR device provided at the first terminal station. The OTDR signal light transmitted from the to the second terminal station is Raman amplified by using the main signal light in the optical transmission system as the excitation light.

[0010] According to the present invention, since the main signal light can be used as the excitation light for the signal light for OTDR, the signal light for OTDR is Raman-amplified without newly providing an excitation light source for the signal light for OTDR. This expands the dynamic range and enables measurement of long-distance spans of optical transmission lines.

[0011] As the main signal light used as the excitation light, the main signal light output from the first terminal station may be used, or the main signal light output from the second terminal station may be used. .. Further, bidirectional excitation can be performed using both main signal lights. Thereby, the effect of Raman amplification can be further enhanced.

[0012] Further, the effect of Raman amplification is further enhanced by Raman amplification of the main signal light used as the excitation light of the signal light for OTDR by using the excitation light used for Raman amplification of the main signal light. This makes it possible to measure long-distance spans. When the 1550 nm band is used as the wavelength band of the main signal light in the optical transmission system, effective Raman amplification can be realized by setting the wavelength band of the signal light for OTDR to the 1650 nm band. Further, by using the signal light for OTDR in the 1650 nm band, it is possible to measure the optical transmission line beyond the EDF even in the optical transmission system including the EDF.

[0013] Further, the present invention solves the above-mentioned problem by transmitting the signal light for OTDR transmitted from the OTDR device provided in the first terminal station toward the second terminal station as the main signal light in the optical transmission system. It can also be solved by Raman amplification or remote excitation amplification using the excitation light of. In this case, the same 1550 nm band as the main signal light is used as the wavelength band of the signal light for OTDR.

[0014] The terminal device constituting the optical transmission system includes a transmission device for transmitting the main signal light to the first optical transmission line and a receiving device for receiving the main signal light from the second optical transmission line. Then, a means for transmitting the main signal light output from the transmission device to the second optical transmission line is provided.

[0015] With such a configuration, the main signal light can be used as the excitation light of the OTDR signal light transmitted from the opposite end stations.

[0016] Further, by having a means for transmitting the light output from the Raman excitation light source of the main signal light provided on the receiving device side to the first optical transmission path, the light is output from the Raman excitation light source. The light can be used as the excitation light of the main signal light used as the excitation light of the signal light for OTDR.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiment of the present invention, Raman amplification or remote excitation amplification of the OTDR signal light is performed by using the main signal light of the 1550 nm band (C-band), the excitation light of the main signal light, or the like as the excitation light.

[0018] The measurement method in the present embodiment can be applied to the C-OTDR in the same manner as the OTDR which is not the C-OTDR. In the present specification, unless otherwise specified, the term OTDR is used as including C-OTDR.

First, the configuration of the optical transmission system according to the embodiment of the present invention will be described with reference to FIG.

The optical transmission system shown in FIG. 1 is a non-relay optical transmission system in which station A and station B 2 are stations at both ends. Focusing on the A direction in the figure, the main signal light is sent from the A station 1 to the B station 2, and the Raman excitation light or the remote excitation light is emitted from the opposite B station 2 in order to Raman-excit the main signal light. Be sent out. Station A 1 is equipped with an OTDR device 101 in order to measure the optical transmission line from station A 1 by OTDR. A remote amplifier using EDF3 and EDF4 is inserted between stations A and B to form a remote excitation optical amplification system, but the present invention also performs remote excitation optical amplification in a system with only Raman amplification without EDF3 inserted. It is applicable as well as the system.

[0021] Next, the device configuration in station A 1 will be described. As shown in FIG. 1, as a device for transmitting light to station B 2, a laser diode (LD102) which is a light source of a main signal, a wavelength division multiplexing device (WDM103) which wavelength-multiplexes light from LD102, and WDM103 It is equipped with an amplifier (AMP104) that amplifies the light of the light source, and a demultiplexing means 105 used for making a measurement by OTDR using the method of the present invention. Further, it includes an OTDR device 101 for performing measurement by OTDR, an optical filter 106, and a WDM coupler 107 for combining the OTDR signal light with other light and transmitting it to a transmission line in the A direction.

[0022] As a device for receiving the main signal light from the B station 2, the wavelengths of the combined demultiplexing means 108 used for the measurement by the OTDR using the method of the present invention and the light from the B station 2 are wavelengthed. It is equipped with a wavelength split multiplexing device (WDM109) for splitting and a photodiode (PD110) for receiving wavelength-split light. Further, it has Raman, a remote excitation light source 111 for Raman amplification or remote excitation amplification of the main signal light from station B 2, and a WDM coupler 112.

The device configuration of station B 2 is the same as that of station A 1, but station B 2 does not have an OTDR device in the form shown in FIG. That is, the B station 2 includes a laser diode (LD202), a wavelength division multiplexing device (WDM203), an amplifier (AMP204), and a demultiplexing means 205 as a device for transmitting light to the A station 1. Devices for receiving the main signal light from station A 1 include a demultiplexing means 208, a wavelength division multiplexing device (WDM209), and a photodiode (PD210). Further, it has Raman, a remote excitation light source 211 for Raman amplification or remote excitation amplification of the main signal light from station A 1, and a WDM coupler 212.

[0024] Each of the demultiplexing means shown in FIG. 1 is a means in which one or a plurality of optical switches, WDM couplers, optical fiber reconnecting means in a station, and the like are combined, and will be described below. It is configured according to the embodiment. Any of the demultiplexing means shown in FIG. 1 may not be necessary depending on the embodiment. Further, a device at an end station that constitutes an optical transmission system such as station A and station B is referred to as an end station device.

Next, a method of measurement by OTDR in an optical transmission system having the above configuration will be described with reference to the first to eighth embodiments. In the following description of each embodiment, the same reference numerals are given to the device portions having the same function. The first to eighth embodiments are examples of measuring the A line, and the ninth to fifteenth embodiments are examples of measuring the B line.

(First Embodiment) FIG. 2 is a diagram for explaining a method of measurement by OTDR in the first embodiment of the present invention. As shown in FIG. 2, the present embodiment does not include the demultiplexing means 105 and 108.

[0027] In the first embodiment shown in FIG. 2, light in the 1650 nm band (λb) is used as the OTDR signal light. The applicable wavelength range of the OTDR signal light is 1600 to 1700 nm. In addition, the C-band main signal light (λa: 1550 nm band signal) from station A 1 is used as excitation light, and the OTDR signal light (λb: 1650 nm band signal) from the OTDR device 101 is Raman amplified to achieve a dynamic range. To expand. That is, as shown in FIG. 3, since the light in the 1650 nm band can be Raman amplified by the light in the 1550 nm band, the light transmitted from the light source of the main signal can be used as the Raman excitation light of the OTDR signal light. The form in which the light in the 1450 nm band amplifies the light in the 1550 nm band in Raman in FIG. 3 will be described later.

[0028] As described above, by using the light in the 1650 nm band, which is a wavelength band capable of Raman amplification by the main signal light in the 1550 nm band, as the OTDR signal light, a light source for Raman excitation is newly provided for the OTDR signal light. It is possible to significantly extend the loss distribution measurement distance in the longitudinal direction by using the light source for the main signal. In addition, since light in the 1650 nm band is not easily absorbed by a system containing EDF, long-distance measurement is possible even with an optical transmission system containing EDF.

(Second Embodiment) FIG. 4 is a diagram for explaining a method of measurement by OTDR in the second embodiment of the present invention.

[0030] In the second embodiment, light in the same 1550 nm band (λa) as the main signal is used as the OTDR signal light, and the excitation transmitted from the Raman excitation light source 111 for Raman amplifying the signal light in the B direction. The OTDR signal light is Raman-amplified using light (λc: 1450 nm band signal) to extend the distance of OTDR measurement. In this embodiment, the applicable wavelength range of the OTDR signal light is 1500 to 1600 nm.

[0031] In the present embodiment, the demultiplexing means 105 and 108 shown in FIG. 1 function as the optical switches 12 and 13 shown in FIG. The optical switch 12 sends the main signal light (light output from the AMP 104) from the station A light source to the A line when not measuring by OTDR, and sends the main signal light from the station A light source when measuring by OTDR. It disconnects and instead sends the excitation light from the optical switch 13 toward the A line. This excitation light is combined with the OTDR signal light by the WDM coupler 107.

The optical switch 13 sends the excitation light from the Raman excitation light source 111 of station A toward the B line when not measuring by OTDR, and excites from the Raman excitation light source 111 when measuring by OTDR. Light is sent in the direction of the optical switch 12 instead of the B line.

[0033] According to the present embodiment, the same wavelength band as the main signal light (λa: 1550 nm band signal) is used as the OTDR signal light. Therefore, as shown in FIG. 3, for Raman amplification of the main signal light. The excitation light (λc: 1450 nm band signal) can be used as the excitation light of the OTDR signal light, and as a result of Raman amplification of the OTDR signal light, the loss distribution measurement distance in the longitudinal direction can be significantly extended.

(Third Embodiment) FIG. 5 is a diagram for explaining a method of measurement by OTDR in the third embodiment of the present invention.

[0035] In the third embodiment, light in the 1650 nm band (λb) is used as the OTDR signal light. The applicable wavelength range of the OTDR signal light is 1600 to 1700 nm. Then, the OTDR signal light (λb: 1650 nm) from the OTDR device 101 is Raman amplified using the main signal light (λa: 1550 nm band signal) from the station A light source. Further, the excitation light (λc: 1450 nm band signal) from the Raman excitation light source 111 is used to Raman amplify the main signal light (λa: 1550 nm band signal) used for amplifying the OTDR signal light. That is, the first-order Stokes wave of λc is used to excite λa, the original power of λa is used as the first Stokes wave, the power of λa excited by λc is used as the second Stokes wave, and λb is used. Excite. As a result, the OTDR signal light is amplified, the dynamic range is expanded, and the distance of the OTDR measurement is extended.

[0036] In the present embodiment, the demultiplexing means 105 on the A line side shown in FIG. 1 functions as the WDM coupler 14 shown in FIG. Further, the demultiplexing means 108 functions as an optical switch 13 shown in FIG.

[0037] The WDM coupler 14 combines the main signal light from the station A light source and the excitation light from the optical switch 13 and transmits them in the A direction. The optical switch 13 transmits the excitation light from the Raman excitation light source 111 of station A to the direction of the WDM coupler 14 instead of the B line at the time of measurement by OTDR.

[0038] According to the present embodiment, the main signal light (λa: 1550 nm band signal) is used as the excitation light of the OTDR signal light (λb: 1650 nm). Further, the excitation light originally used as the excitation light of the main signal in the B line (λc: 1450 nm band signal) is used as the excitation light of the main signal light in the A line to perform Raman amplification of the main signal light. Since the main signal light is used as the excitation light of the OTDR signal light, the loss distribution measurement distance in the longitudinal direction can be significantly extended. In addition, since 1650 nm is used as the OTDR signal light, long-distance surveys are possible even in systems that include EDF.

(Fourth Embodiment) FIG. 6 is a diagram for explaining a method of measurement by OTDR in the fourth embodiment of the present invention.

[0040] In the fourth embodiment, the 1650 nm band (λb) is used as the OTDR signal light. The applicable wavelength range of the OTDR signal light is 1600 to 1700 nm. Then, in addition to Raman amplification of the OTDR signal light from the OTDR device 101 using the main signal light from the station A light source (λa: 1550 nm band signal), the main signal light from the station B light source (λa: 1550 nm band) The OTDR signal light is Raman-amplified by using the signal) as the excitation light. That is, the main signal light in both directions is used as the bidirectional excitation light for Raman amplification.

[0041] In the fourth embodiment, the combined demultiplexing means 205 on the B line side in the B station 2 shown in FIG. 1 functions as the optical switch 16 shown in FIG. The optical switch 16 sends the main signal light (light output from the AMP 204) from the station B light source to the B line when not measuring by OTDR, and sends the main signal light from the light source of station B when measuring by OTDR. Switches to send to the WDM coupler 17 on the A line side.

Further, the demultiplexing means 208 on the A line side in the B station 2 functions as the WDM coupler 17 shown in FIG. The WDM coupler 17 transmits the main signal light from the B station light source transmitted from the optical switch 16 in the direction toward the A station 1 on the A line.

[0043] In the fourth embodiment, the loss distribution measurement in the longitudinal direction is performed by using the main signal light (λa: 1550 nm band signal) in both directions as the bidirectional excitation light for the OTDR signal light (λb: 1650 nm band signal). The distance can be greatly extended, and long-distance surveys will be possible. In addition, by using the 1650 nm band as the OTDR signal light, it is possible to perform measurements by OTDR even in a system that includes EDF.

(Fifth Embodiment) FIG. 7 is a diagram for explaining a method of measurement by OTDR in the fifth embodiment of the present invention.

[0045] In the fifth embodiment, light in the 1650 nm band (λb) is used as the OTDR signal light. The applicable wavelength range of the OTDR signal light is 1600 to 1700 nm. Then, the OTDR signal light (λb: 1650 nm) from the OTDR device 101 is Raman amplified using the main signal light (λa: 1550 nm band signal) from the station A light source. Furthermore, by Raman amplification of the main signal light used for amplification of the OTDR signal light using the excitation light (λc: 1450 nm band signal) from the Raman excitation light source 111 for Raman amplification of the signal light in the B direction. , OTDR signal Amplifies the light. In addition to this, the main signal light (λa: 1550 nm band signal) from the station B light source is also used as excitation light to Raman amplify the OTDR signal light.

[0046] In the present embodiment, the demultiplexing means 105 on the A line side shown in FIG. 1 functions as the WDM coupler 14 shown in FIG. 7. The WDM coupler 14 combines the main signal light from the station A light source and the excitation light from the optical switch 13 and transmits them in the A direction. Further, the optical switch 13 transmits the excitation light from the Raman excitation light source 111 of station A to the direction of the WDM coupler 14 instead of the B line at the time of measurement by OTDR.

Further, the combined demultiplexing means 205 on the B line side in the B station functions as the optical switch 16 shown in FIG. 7. This optical switch 16 sends the main signal light from the B station light source to the WDM coupler 17 on the A line side at the time of measurement by OTDR. Further, the demultiplexing means 208 on the A line side in station B functions as the WDM coupler 17 shown in FIG. The WDM coupler 17 transmits the main signal light from the B station light source switched by the optical switch 16 in the direction toward the A station on the A line.

[0048] According to the present embodiment, the main signal (λa: 1550 nm band signal) is used as the excitation light of the OTDR signal light (λb: 1650 nm) to Raman amplify the OTDR signal light. Further, since the excitation light used as the excitation light of the main signal in the B direction (λc: 1450 nm band signal) is used as the excitation light of the main signal light and the main signal light is Raman amplified, the OTDR signal light is further increased. It can be amplified. In addition to this, since the main signal light in the B direction (λa: 1550 nm band signal) is used as the excitation light for the OTDR signal light, the OTDR signal light can be further amplified, and the loss distribution measurement distance in the longitudinal direction is greatly extended. It becomes possible. In addition, since 1650 nm is used as the OTDR signal light, long-distance surveys are possible even with optical transmission systems that include EDF.

(6th Embodiment) FIG. 8 is a diagram for explaining a method of measurement by OTDR in the 6th embodiment of the present invention.

[0050] In the sixth embodiment, the 1650 nm band (λb) is used as the OTDR signal light. The applicable wavelength range of the OTDR signal light is 1600 to 1700 nm. Then, in addition to Raman amplification of the OTDR signal light from the OTDR device 101 using the main signal light from the station A light source (λa: 1550 nm band signal), the main signal light from the station B light source (λa: 1550 nm band) The OTDR signal light is Raman-amplified by using the signal) as the excitation light of the OTDR signal light. Furthermore, by using the Raman excitation light from the Raman excitation light source 211 of station B as the excitation light of the bidirectional main signal light (λa: 1550 nm band signal), the main signal light is Raman amplified and the OTDR signal light is generated. By further Raman amplification, the distance of measurement by OTDR is extended.

[0051] In the sixth embodiment, the demultiplexing means 205 on the B line side in the B station 2 functions as the optical switch 16 shown in FIG. This optical switch 16 switches so as to send the main signal light from the B station light source to the WDM coupler 17 on the A line side at the time of measurement by OTDR. Further, the demultiplexing means 208 on the A line side in station B 2 functions as the WDM coupler 17 shown in FIG. This WDM coupler 17 combines the main signal light from the B station light source transmitted from the optical switch 16 with the excitation light (λc: 1450 nm band signal) from the Raman excitation light source 211 in the B direction on the A line. Send out.

[0052] In the sixth embodiment, the main signal light in both directions is used as the bidirectional excitation light with respect to the OTDR signal light, and the excitation light (λc: 1450 nm band signal) from the Raman excitation light source 211 of station B is further used. By using it as the excitation light of the bidirectional main signal, the loss distribution measurement distance in the longitudinal direction in OTDR can be significantly extended, and long-distance investigation becomes possible. In addition, by using the 1650 nm band signal as the OTDR signal light, long-distance surveys will be possible even in systems that include EDF.

(7th Embodiment) FIG. 9 is a diagram for explaining a method of measurement by OTDR in the 7th embodiment of the present invention.

[0054] In the seventh embodiment, light in the 1650 nm band (λb) is used as the OTDR signal light. The applicable wavelength range of the OTDR signal light is 1600 to 1700 nm. Then, the OTDR signal light (λb: 1650 nm band signal) from the OTDR device 101 is Raman amplified using the main signal light (λa: 1550 nm band signal) from the station A light source. Further, Raman amplification of the main signal light used for amplification of the OTDR signal light is performed by using the excitation light (λc: 1450 nm band signal) from the Raman excitation light source 111 for Raman amplification of the main signal light in the B direction. Further amplifies the OTDR signal light. In addition to this, the main signal light (λa: 1550 nm band signal) from the station B light source is also used as the excitation light for the OTDR signal light, and the main signal excitation light (λc: 1450 nm) from the Raman excitation light source 211 of station B is also used. Band signal) is used for Raman excitation of the main signal.

[0055] In the present embodiment, the demultiplexing means 105 on the A line side of the A station 1 shown in FIG. 1 functions as the WDM coupler 14 shown in FIG. The WDM coupler 14 combines the main signal light from the station A light source and the excitation light (λc: 1450 nm band signal) from the optical switch 13 and transmits them in the A direction. Further, the demultiplexing means 108 functions as an optical switch 13, and this optical switch 13 sends the excitation light from the Raman excitation light source 111 of station A toward the WDM coupler 14 instead of the B line at the time of measurement by OTDR. To do.

Further, the combined demultiplexing means 205 on the B line side in the B station 2 functions as the optical switch 16 shown in FIG. This optical switch 16 sends the main signal light from the B station light source to the WDM coupler 17 on the A line side at the time of measurement by OTDR. Further, the demultiplexing means 208 on the A line side of the B station 2 functions as the WDM coupler 17 shown in FIG. 9, and the WDM coupler 17 receives the main signal light from the B station light source transmitted from the optical switch 16. It is combined with the main signal excitation light (λc: 1450 nm band signal) from the Raman excitation light source 211 of station B and transmitted in the B direction on the A line.

[0057] According to the present embodiment, the main signal (λa: 1550 nm band signal) is used as the bidirectional excitation light of the OTDR signal light (λb: 1650 nm) to amplify the OTDR signal light. In addition to this, the OTDR signal light is amplified by Raman amplification of the above main signal light with bidirectional excitation light for the main signal (λc: 1450 nm band signal), and the loss distribution measurement distance in the longitudinal direction is measured. It will be possible to extend it significantly. In addition, since 1650 nm is used as the OTDR signal light, long-distance surveys are possible even with optical transmission systems that include EDF.

(Eighth Embodiment) In each of the above embodiments, an example of measuring by OTDR from the A station side is shown, but in each embodiment, the B station side is also provided with the OTDR device, and the A station is provided. In addition to the OTDR from the side, the OTDR may be performed from the B station side. Taking the configuration of the fourth embodiment in which the Raman excitation of the OTDR signal light is performed by the bidirectional main signal light as an example, the configuration in which the OTDR is performed from both stations A and B is shown in FIG.

FIG. 11 is a diagram showing an effect when OTDR is performed from both stations. As shown in Fig. 11, even if the distance between the stations at both ends of the optical transmission line is long and the entire span of the optical transmission system cannot be measured by OTDR from only one side, the system including EDF can be performed by performing OTDR from both stations. Can also measure the entire span.

(9th Embodiment) FIG. 12 is a diagram for explaining a measurement method by OTDR in the 9th embodiment of the present invention. In the ninth to fifteenth embodiments, the B line is measured by providing the OTDR device 101 on the B line side.

[0061] In the ninth embodiment, light in the 1650 nm band (λb) is used as the OTDR signal light. The applicable wavelength range of the OTDR signal light is 1600 to 1700 nm. Then, the OTDR signal light (λb: 1650 nm) from the OTDR device 101 is Raman amplified using the main signal light (λa: 1550 nm band signal) from the station A light source.

[0062] In the present embodiment, the demultiplexing means 105 and 108 shown in FIG. 1 function as the optical switches 21 and 22 shown in FIG. The optical switch 21 transmits the main signal light from the A station light source to the A line when the measurement is not performed by the OTDR, and transmits the main signal light from the A station light source to the optical switch 22 when the measurement is performed by the OTDR. The optical switch 22 sends the excitation light from the Raman excitation light source 111 of station A to the B line when not measuring by OTDR, and sends the main signal light of station A from the optical switch 21 to the B line when measuring by OTDR. Send to.

[0063] According to the present embodiment, the same effect as that in the first embodiment can be obtained on the B line.

(10th Embodiment) FIG. 13 is a diagram for explaining a measurement method by OTDR in the 10th embodiment of the present invention.

[0065] In the tenth embodiment, light in the same 1550 nm band (λa) as the main signal is used as the OTDR signal light, and the excitation transmitted from the Raman excitation light source 111 for Raman amplification of the signal light in the B direction is used. The OTDR signal light is Raman amplified using light (λc: 1450 nm band) to extend the distance of the OTDR. In this embodiment, the applicable wavelength range of the OTDR signal light is 1500 to 1600 nm. In this embodiment, it is not necessary to provide the demultiplexing means.

[0066] According to the present embodiment, the same effect as that in the second embodiment can be obtained in the B line. (11th Embodiment) FIG. 14 is a diagram for explaining the measurement method by OTDR in the 11th embodiment of the present invention.

[0067] In the eleventh embodiment, light in the 1650 nm band (λb) is used as the OTDR signal light. The applicable wavelength range of the OTDR signal light is 1600 to 1700 nm. Then, the OTDR signal light (λb: 1650 nm band) from the OTDR device 101 is Raman amplified using the main signal light (λa: 1550 nm band signal) from the station A light source. Further, the excitation light (λc: 1450 nm band signal) from the Raman excitation light source 111 is used to Raman amplify the main signal light (λa: 1550 nm band signal) used for amplifying the OTDR signal light. That is, the primary Stokes wave of λc is used to excite λa, the original power of λa is used as the primary Stokes wave, the power of λa excited by λc is used as the secondary Stokes wave, and λb is excited. To do. As a result, the OTDR signal light is amplified, the dynamic range is expanded, and the distance of the OTDR measurement is extended.

[0068] In the present embodiment, the demultiplexing means 105 shown in FIG. 1 functions as the optical switch 21 shown in FIG. Further, the demultiplexing means 108 functions as the WDM coupler 23 shown in FIG.

[0069] The optical switch 21 transmits the main signal light from the station A light source to the direction of the WDM coupler 23 instead of the A line at the time of measurement by OTDR. The WDM coupler 23 combines the excitation light from the Raman excitation light source of station A with the main signal light and sends it in the A direction of the B line.

[0070] According to the present embodiment, the same effect as that in the third embodiment can be obtained in the B line. (12th Embodiment) FIG. 15 is a diagram for explaining a measurement method by OTDR in the 12th embodiment of the present invention.

[0071] In the eleventh embodiment, light in the 1650 nm band (λb) is used as the OTDR signal light. The applicable wavelength range of the OTDR signal light is 1600 to 1700 nm. Then, the OTDR signal light (λb: 1650 nm band) from the OTDR device 101 is Raman amplified using the main signal light (λa: 1550 nm band signal) from the station A light source. Furthermore, the OTDR signal light is Raman amplified by using the main signal from the B station light source as the excitation light. That is, the main signal light in both directions is used as the bidirectional excitation light for Raman amplification.

[0072] In the present embodiment, the demultiplexing means 105 shown in FIG. 1 functions as the optical switch 21 shown in FIG. Further, the demultiplexing means 108 functions as the WDM coupler 23 shown in FIG. The optical switch 21 sends the main signal light from the light source of station A to the direction of the WDM coupler 23 instead of the line A at the time of measurement by OTDR. The WDM coupler 23 transmits the main signal light in the A direction of the B line.

[0073] According to the present embodiment, the same effect as that in the fourth embodiment can be obtained in the B line.

(13th Embodiment) FIG. 16 is a diagram for explaining a measurement method by OTDR in the 13th embodiment of the present invention.

[0075] In the thirteenth embodiment, light in the 1650 nm band (λb) is used as the OTDR signal light. The applicable wavelength range of the OTDR signal light is 1600 to 1700 nm. Then, the OTDR signal light (λb: 1650 nm band) from the OTDR device 101 is Raman amplified using the main signal light (λa: 1550 nm band signal) from the station A light source. Further, the excitation light (λc: 1450 nm band signal) from the Raman excitation light source 111 is used to Raman amplify the main signal light (λa: 1550 nm band signal) used for amplifying the OTDR signal light. Furthermore, the OTDR signal light is Raman amplified by using the main signal from the B station light source as the excitation light. That is, the main signal light in both directions is used as bidirectional excitation light for Raman amplification, and the main signal used for amplification of OTDR signal light using the excitation light (λc: 1450 nm band signal) from the Raman excitation light source 111. Raman amplification of light (λa: 1550 nm band signal).

[0076] In the present embodiment, the demultiplexing means 105 shown in FIG. 1 functions as the optical switch 21 shown in FIG. Further, the demultiplexing means 108 functions as the WDM coupler 23 shown in FIG. The optical switch 21 sends the main signal light from the station A light source to the direction of the WDM coupler 23 instead of the A line when measuring by OTDR. The WDM coupler 23 combines the main signal light from the A station light source with the excitation light from the Raman excitation light source 111 and sends it in the A direction of the B line.

[0077] According to the present embodiment, the same effect as that of the fifth embodiment can be obtained on the B line.

(14th Embodiment) FIG. 17 is a diagram for explaining a measurement method by OTDR in the 14th embodiment of the present invention.

[0079] In the fourteenth embodiment, light in the 1650 nm band (λb) is used as the OTDR signal light. The applicable wavelength range of the OTDR signal light is 1600 to 1700 nm. Then, the OTDR signal light (λb: 1650 nm band) from the OTDR device 101 is Raman amplified using the main signal light (λa: 1550 nm band signal) from the station A light source. Furthermore, the OTDR signal light is Raman amplified by using the main signal from the B station light source as the excitation light. Further, the excitation light (λc: 1450 nm band signal) from the Raman excitation light source 211 is used from station B to Raman amplify the main signal light (λa: 1550 nm band signal) used for amplifying the OTDR signal light. That is, the main signal light in both directions is used as bidirectional excitation light for Raman amplification, and the excitation light (λc: 1450 nm band signal) from the Raman excitation light source 211 of station B is used for amplification of OTDR signal light. Raman amplification of the main signal light (λa: 1550 nm band signal).

[0080] In the present embodiment, the demultiplexing means 105 shown in FIG. 1 functions as the optical switch 21 shown in FIG. Further, the demultiplexing means 108 functions as the WDM coupler 23 shown in FIG. The functions of the optical switch 21 and the WDM coupler 23 are as described in the twelfth embodiment.

Further, the combined demultiplexing means 208 on the B line side in the B station functions as the optical switch 24 shown in FIG. This optical switch 24 sends the excitation light from the Raman excitation light source 211 of station B to the WDM coupler 25 on the B line side at the time of measurement by OTDR. Further, the demultiplexing means 205 on the B line side functions as the WDM coupler 25 shown in FIG. The WDM coupler 25 combines the Raman excitation light switched by the optical switch 24 with the main signal light from the B station light source and sends it in the direction toward the A station on the B line.

[0082] According to the present embodiment, the same effect as that in the sixth embodiment can be obtained in the B line.

(Fifteenth Embodiment) FIG. 18 is a diagram for explaining a measurement method by OTDR in the fifteenth embodiment of the present invention.

[0084] In the fifteenth embodiment, light in the 1650 nm band (λb) is used as the OTDR signal light. The applicable wavelength range of the OTDR signal light is 1600 to 1700 nm. Then, the OTDR signal light (λb: 1650 nm band) from the OTDR device 101 is Raman amplified using the main signal light (λa: 1550 nm band signal) from the station A light source. Further, the excitation light (λc: 1450 nm band signal) from the Raman excitation light source 111 of station A is used to Raman amplify the main signal light (λa: 1550 nm band signal) used for amplifying the OTDR signal light. Furthermore, the OTDR signal light is Raman amplified by using the main signal from the B station light source as the excitation light. Further, the excitation light (λc: 1450 nm band signal) from the Raman excitation light source 211 of station B is used to Raman amplify the main signal light (λa: 1550 nm band signal) used for amplifying the OTDR signal light. That is, the main signal light in both directions is used as the bidirectional excitation light for Raman amplification, and the excitation light (λc: 1450 nm band signal) from the Raman excitation light source of both stations A and B is used to amplify the OTDR signal light. Raman amplification of the main signal light (λa: 1550 nm band signal) used for this purpose.

[0085] In the present embodiment, the demultiplexing means 105 shown in FIG. 1 functions as the optical switch 21 shown in FIG. Further, the demultiplexing means 108 functions as the WDM coupler 23 shown in FIG. The functions of the optical switch 21 and the WDM coupler 23 are as described in the thirteenth embodiment.

[0086] Further, the combined demultiplexing means 208 on the B line side in the B station functions as the optical switch 24 shown in FIG. Further, the demultiplexing means 205 on the B line side functions as the WDM coupler 25 shown in FIG. The functions of the optical switch 24 and the WDM coupler 25 are as described in the 14th embodiment.

[0087] According to the present embodiment, the same effect as that in the seventh embodiment can be obtained in the B line.

(16th Embodiment) FIG. 19 is a diagram for explaining a measurement method by OTDR in the 16th embodiment of the present invention.

[0089] In the 16th embodiment, light in the same 1550 nm band (λa) as the main signal is used as the OTDR signal light, and is transmitted from the remote excitation light source 111 for remotely exciting and amplifying the signal light in the B direction. The OTDR signal light is remotely excited using the excitation light (λc: 1480 nm band) to extend the distance of the OTDR. In this embodiment, the applicable range of the OTDR signal light is 1500 to 1600 nm. Further, in the present embodiment, it is not necessary to provide the demultiplexing means.

[0090] The present invention is not limited to the above examples, and various modifications and applications can be made within the scope of the claims.

(Appendix 1) A method of performing measurement by OTDR in an optical transmission system having a first terminal station and a second terminal station, the second from the OTDR device provided in the first terminal station. A method characterized in that an OTDR signal light transmitted toward an end station is Raman-amplified using the main signal light in the optical transmission system as excitation light, and measurement is performed by the OTDR. (Appendix 2) The method according to Appendix 1 in which the OTDR signal light is Raman amplified using the main signal light output from the first terminal station.

(Appendix 3) The method according to Appendix 1 or 2, wherein the signal light for OTDR is Raman amplified by using the main signal light output from the second terminal station. (Appendix 4) Excitation of the signal light for OTDR using the excitation light output from the first terminal station for Raman amplification of the main signal light transmitted from the second terminal station to the first terminal station. The method according to any one of Supplementary note 1 to 3 for Raman amplification of the main signal light used as light. (Appendix 5) Excitation of the signal light for OTDR using the excitation light output from the second terminal station for Raman amplification of the main signal light transmitted from the first terminal station to the second terminal station. The method according to any one of Supplementary note 1 to 4, which amplifies the main signal light used as light by Raman amplification.

(Appendix 6) The wavelength band of the main signal light in the optical transmission system is the 1550 nm band, and the wavelength band of the signal light for OTDR is the 1650 nm band. Method. (Appendix 7) This is a method of measuring by OTDR in an optical transmission system having a first terminal station and a second terminal station, from the OTDR device provided in the first terminal station to the second terminal station. A method of Raman-amplifying OTDR signal light transmitted toward an OTDR using the excitation light of the main signal light in the optical transmission system, and performing measurement by OTDR.

(Appendix 8) The method according to Appendix 7, wherein the excitation light of the main signal light in the optical transmission system has a wavelength band of 1450 nm or 1480 nm, and the signal light for OTDR has a wavelength band of 1550 nm.

(Appendix 9) A method of performing measurement by OTDR in an optical transmission system having a first terminal station and a second terminal station, the second from the OTDR device provided in the first terminal station. The feature is that the signal light for OTDR transmitted to the terminal station is remotely excited and Raman amplified using the excitation light for remote excitation light amplification output from the first terminal station, and the measurement is performed by OTDR. How to.

(Appendix 10) The method according to Appendix 9, wherein the wavelength band of the main signal light and the wavelength band of the signal light for OTDR in the optical transmission system are the 1550 nm band.

(Appendix 11) A terminal device in an optical transmission system having a transmitting device for transmitting main signal light to a first optical transmission line and a receiving device for receiving main signal light from a second optical transmission line. The terminal device is provided with a means for transmitting the main signal light output from the transmission device to the second optical transmission line. (Appendix 12) The terminal device according to Appendix 11, wherein the transmitting means includes an optical switch provided on the transmitting device side and a coupler provided on the receiving device side.

(Appendix 13) An terminal device in an optical transmission system having a transmitting device that sends main signal light to a first optical transmission line and a receiving device that receives main signal light from a second optical transmission line. The terminal device is characterized by having a means for transmitting the light output from the Raman excitation light source of the main signal light provided on the receiving device side to the first optical transmission line.

(Appendix 14) The terminal device according to Appendix 13, wherein the transmitting means includes an optical switch provided on the receiving device side and a coupler provided on the transmitting device side.

(Appendix 15) A first terminal device having a transmitting device for transmitting the main signal light to the first optical transmission line and a receiving device for receiving the main signal light from the second optical transmission line, and a main unit. An optical transmission system having a second terminal device having a transmitting device for transmitting signal light to a second optical transmission line and a receiving device for receiving main signal light from the first optical transmission line. An optical transmission system characterized in that it is provided with a means for transmitting the main signal light output from the transmission device in the terminal device of 1 to the second optical transmission line.

(Appendix 16) The transmitting means includes an optical switch provided on the transmitting device side in the first terminal station device and a coupler provided on the receiving device side in the first terminal station device. The optical transmission system according to Appendix 15 having.

(Appendix 17) A first terminal device having a transmitting device for transmitting the main signal light to the first optical transmission line and a receiving device for receiving the main signal light from the second optical transmission line, and a main unit. An optical transmission system having a second terminal device having a transmitting device for transmitting signal light to a second optical transmission line and a receiving device for receiving main signal light from the first optical transmission line. An optical transmission system characterized in that it is provided with a means for transmitting the light output from the Raman excitation light source of the main signal provided on the receiving device side of the terminal device 1 to the first optical transmission line.

(Appendix 18) The transmitting means includes an optical switch provided on the receiving device side in the first terminal station device and a coupler provided on the transmitting device side in the first terminal station device. The optical transmission system according to Appendix 17 having.

[Effect of the Invention] According to the present invention, since the main signal light can be used as the excitation light of the signal light for OTDR, the signal for OTDR is not newly provided with the excitation light source for the signal light for OTDR. Raman amplification of light makes it possible to measure long-distance spans of non-relay optical transmission lines. Further, by using the excitation light for the main signal light as the excitation light for the main signal light used as the excitation light for the signal light for OTDR, the signal light for OTDR is further Raman-amplified, and the long-distance span of the optical transmission path is extended. Measurement becomes possible. Further, by the method of using the 1650 nm band as the signal light for OTDR and the method of using the excitation light of the 1480 nm band, it is possible to measure the optical transmission line beyond the EDF even in the optical transmission line system including the EDF.

BRIEF DESCRIPTION OF THE DRAWINGS [Fig. 1] Fig. 1 is a configuration diagram of an optical transmission system according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a method of measurement by OTDR in the first embodiment of the present invention.

FIG. 3 is a diagram for explaining Raman amplification of OTDR signal light.

FIG. 4 is a diagram for explaining a method of measurement by OTDR in the second embodiment of the present invention.

FIG. 5 is a diagram for explaining a method of measurement by OTDR in the third embodiment of the present invention.

FIG. 6 is a diagram for explaining a method of measurement by OTDR in the fourth embodiment of the present invention.

FIG. 7 is a diagram for explaining a method of measurement by OTDR in the fifth embodiment of the present invention.

FIG. 8 is a diagram for explaining a method of measurement by OTDR in the sixth embodiment of the present invention.

FIG. 9 is a diagram for explaining a method of measurement by OTDR in the seventh embodiment of the present invention.

FIG. 10 is a diagram for explaining a method of measurement by OTDR in the eighth embodiment of the present invention.

FIG. 11 is a diagram showing an effect when OTDR is performed from both stations.

FIG. 12 is a diagram for explaining a method of measurement by OTDR in the ninth embodiment of the present invention.

FIG. 13 is a diagram for explaining a method of measurement by OTDR in the tenth embodiment of the present invention.

FIG. 14 is a diagram for explaining a method of measurement by OTDR in the eleventh embodiment of the present invention.

FIG. 15 is a diagram for explaining a method of measurement by OTDR in the twelfth embodiment of the present invention.

FIG. 16 is a diagram for explaining a method of measurement by OTDR in the thirteenth embodiment of the present invention.

FIG. 17 is a diagram for explaining a method of measurement by OTDR in the 14th embodiment of the present invention.

FIG. 18 is a diagram for explaining a method of measurement by OTDR in the fifteenth embodiment of the present invention.

FIG. 19 is a diagram for explaining a method of measurement by OTDR in the 16th embodiment of the present invention.

[Description of Code] 1 A station 2 B station 101, 201 OTDR device (or C-OTDR device) 102, 202 LD103, 203, 109, 209 WDM104, 204 AMP105, 108, 205, 208 Combined demultiplexing means 110, 210 PD111, 211 Raman and remote excitation light sources 17, 14, 23, 25, 107, 207, 112, 212 WDM couplers 12, 13, 16, 21, 22, 24 Optical switches