Optical communication system

Abstract

This optical communication system is configured to comprise: a first optical fiber (3) that propagates communication light transmitted from a communication device (1) to an opposing device (2); a second optical fiber (5) that propagates communication light transmitted from the opposing device (2) to the communication device (1); a plurality of first bypass fibers (7-1)-(7-G) that bypass an optical amplifier (4) inserted into the first optical fiber (3); and a plurality of second bypass fibers (8-1)-(8-G) that bypass an optical amplifier (6) inserted into the second optical fiber (5). The optical communication system further comprises a sensor device (9) that transmits sensor light to either the first optical fiber (3) or the second optical fiber (5) and receives backscattered light having returned from either the first optical fiber (3) or the second optical fiber (5).

Description

Optical Communication Systems

[0001] The present disclosure relates to optical communication systems.

[0002] There is an optical communication system including a communication optical fiber that propagates communication light transmitted from a communication device to a remote device, and a communication optical fiber that propagates communication light transmitted from the remote device to the communication device. Since an optical amplifier is generally inserted into each optical fiber, the light transmission direction of each optical fiber is unidirectional. As an example of such an optical communication system, Patent Document 1 discloses an optical communication system in which, in addition to the optical fiber described above, a sensing optical fiber that transmits sensor light and backscattered light is wired between the communication device and the remote device. Since no optical amplifier is inserted into the sensing optical fiber, the light transmission direction of the sensing optical fiber is bidirectional. The optical communication system disclosed in Patent Document 1 includes a sensor device that transmits sensor light to the sensing optical fiber, receives backscattered light of the sensor light returned from the sensing optical fiber, and senses the communication optical fiber based on the backscattered light.

[0003] International Publication No. 2021-111699

[0004] In the optical communication system disclosed in Patent Document 1, in order for the sensor device to sense the communication optical fiber, a sensing optical fiber having the same length as the communication optical fiber must be installed. Therefore, the optical communication system has a problem in that the longer the distance between the communication device and the opposing device, the longer the cable length of the sensing optical fiber must be installed.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to obtain an optical communication system that can sense a communication optical fiber without wiring a sensing optical fiber connecting a communication device and an opposing device.

[0006] An optical communication system according to the present disclosure includes a first optical fiber for propagating communication light transmitted from a communication device to an opposing device, a second optical fiber for propagating communication light transmitted from the opposing device to the communication device, a plurality of first bypass fibers for bypassing an optical amplifier inserted in the first optical fiber, and a plurality of second bypass fibers for bypassing an optical amplifier inserted in the second optical fiber. The optical communication system also includes a sensor device for transmitting sensor light to either the first optical fiber or the second optical fiber and receiving backscattered light returned from either the first optical fiber or the second optical fiber.

[0007] According to the present disclosure, it is possible to sense an optical fiber for communication without wiring an optical fiber for sensing that connects a communication device and a counterpart device.

[0008] FIG. 1 is a configuration diagram showing an optical communication system according to a first embodiment. FIG. 2 is an explanatory diagram showing optical spectrum images of sensor light and backscattered light. FIG. 3 is a configuration diagram showing an optical communication system according to a second embodiment. FIG. 4 is an explanatory diagram showing wavelengths of communication light for N opposite devices 2-1 to 2-N. FIG. 5 is a configuration diagram showing an optical communication system according to a third embodiment. FIG. 6 is a configuration diagram showing an optical communication system according to a fourth embodiment. FIG. 7 is a configuration diagram showing an optical communication system according to a fifth embodiment. FIG. 8 is a configuration diagram showing an optical communication system according to a sixth embodiment. FIG. 9 is a configuration diagram showing an optical communication system according to a seventh embodiment. FIG. 10 is a configuration diagram showing a part of an optical communication system according to an eighth embodiment. FIG. 11 is a configuration diagram showing a part of an optical communication system according to a ninth embodiment. FIG. 11 is a configuration diagram showing a part of an optical communication system according to a tenth embodiment. FIG. 12 is a configuration diagram showing an optical communication system according to an eleventh embodiment. FIG. 13 is a configuration diagram showing another optical communication system according to the eleventh embodiment. FIG. 14 is a configuration diagram showing an optical communication system according to a twelfth embodiment.

[0009] In order to explain the present disclosure in more detail, embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0010] 1 is a configuration diagram showing an optical communication system according to embodiment 1. The optical communication system shown in Fig. 1 includes a communication device 1, an opposing device 2, a first optical fiber 3, an optical amplifier 4, a second optical fiber 5, an optical amplifier 6, a first bypass fiber 7, a second bypass fiber 8, and a sensor device 9.

[0011] The communication device 1 includes an optical transmitter that transmits communication light and an optical receiver that receives the communication light. The opposite device 2 is a communication device that transmits and receives communication light to and from the communication device 1. The opposite device 2 includes an optical receiver that receives the communication light transmitted from the communication device 1 and an optical transmitter that transmits the communication light to the communication device 1.

[0012] The first optical fiber 3 is realized by, for example, a single-mode fiber, a single-core core wire of a multimode fiber, or a multi-core core wire. One end of the first optical fiber 3 is connected to the communication device 1, and the other end of the first optical fiber 3 is connected to the opposing device 2. The first optical fiber 3 is an optical fiber for communication that propagates communication light transmitted from the communication device 1 to the opposing device 2. An optical amplifier 4 is inserted into the first optical fiber 3.

[0013] The optical amplifier 4 is realized by, for example, an erbium-doped fiber amplifier (EDFA) or a semiconductor optical amplifier (SOA). The optical amplifier 4 amplifies the communication light transmitted from the communication device 1 and outputs the amplified communication light to the opposing device 2.

[0014] The second optical fiber 5 is realized by, for example, a single-mode fiber, a single-core core wire of a multimode fiber, or a multi-core core wire. One end of the second optical fiber 5 is connected to the communication device 1, and the other end of the second optical fiber 5 is connected to the opposing device 2. The second optical fiber 5 is an optical fiber for communication that propagates communication light transmitted from the opposing device 2 to the communication device 1. An optical amplifier 6 is inserted in the second optical fiber 5.

[0015] The optical amplifier 6 is realized by, for example, an EDFA or an SOA. The optical amplifier 6 amplifies the communication light transmitted from the opposite device 2 and outputs the amplified communication light to the communication device 1.

[0016] Each of the first bypass fibers 7-1 to 7-G is realized by, for example, a single-mode fiber, a single-core core wire of a multimode fiber, or a multi-core core wire. G is an integer equal to or greater than 2. The first bypass fiber 7-g (g=1, . . . , G) is a fiber for bypassing the optical amplifier 4 inserted in the first optical fiber 3. Specifically, one end of the first bypass fiber 7-g is connected to the input side of the optical amplifier 4, and the other end of the first bypass fiber 7-g is connected to the output side of the optical amplifier 4.

[0017] Each of the second bypass fibers 8-1 to 8-G is realized by, for example, a single-mode fiber, a single-core core wire of a multimode fiber, or a multi-core core wire. The second bypass fiber 8-g is a fiber for bypassing the optical amplifier 6 inserted in the second optical fiber 5. Specifically, one end of the second bypass fiber 8-g is connected to the input side of the optical amplifier 6, and the other end of the second bypass fiber 8-g is connected to the output side of the optical amplifier 6.

[0018] The sensor device 9 includes an optical transmitter that transmits sensor light, an optical receiver that receives backscattered light of the sensor light, and a detection unit that senses either the first optical fiber 3 or the second optical fiber 5 based on the backscattered light. The sensor device 9 transmits sensor light to either the first optical fiber 3 or the second optical fiber 5, and receives backscattered light returned from either the first optical fiber 3 or the second optical fiber 5. The sensor device 9 senses either the first optical fiber 3 or the second optical fiber 5 based on the backscattered light.

[0019] Next, the operation of the optical communication system shown in Fig. 1 will be described. When communication device 1 transmits communication light to opposite device 2, communication device 1 sends the communication light to the first optical fiber 3. The communication light sent to the first optical fiber 3 is amplified by the optical amplifier 4, and the amplified communication light reaches the opposite device 2. As a result, the opposite device 2 receives the communication light transmitted from communication device 1.

[0020] When the opposite device 2 transmits communication light to the communication device 1, the opposite device 2 sends the communication light to the second optical fiber 5. The communication light sent to the second optical fiber 5 is amplified by the optical amplifier 6, and the amplified communication light reaches the communication device 1. In this way, the communication device 1 receives the communication light transmitted from the opposite device 2.

[0021] Each of the first optical fiber 3 and the second optical fiber 5 may change due to, for example, the surrounding environment or the passage of time, such as temperature change, vibration change, stress change, or optical loss change.

[0022] When sensing the first optical fiber 3, the sensor device 9 transmits sensor light to the first optical fiber 3. The sensor light transmitted to the first optical fiber 3 is scattered by the first optical fiber 3, and backscattered sensor light returns to the sensor device 9. The backscattered sensor light is scattered light according to changes in the first optical fiber 3. As shown in FIG. 2, the backscattered sensor light may be, for example, Rayleigh scattered light, Brillouin scattered light, or Raman scattered light. FIG. 2 is an explanatory diagram showing optical spectrum images of the sensor light and the backscattered light. In FIG. 2, the horizontal axis represents wavelength. FIG. 2 shows the optical spectra of the sensor light and the backscattered light.

[0023] Because the optical amplifier 4 inserted in the first optical fiber 3 has a unidirectional light transmission direction, the backscattered light of the sensor light cannot pass through the optical amplifier 4. However, because the optical communication system shown in FIG. 1 is provided with first bypass fibers 7-1 to 7-G for bypassing the optical amplifier 4, the backscattered light of the sensor light can return to the sensor device 9 via any of the first bypass fibers 7-1 to 7-G. The sensor device 9 receives the backscattered light returned from the first optical fiber 3 and senses the first optical fiber 3 based on the backscattered light. Sensing by the sensor device 9 itself is a known technique, and therefore a detailed description thereof will be omitted.

[0024] When sensing the second optical fiber 5, the sensor device 9 transmits sensor light to the second optical fiber 5. The sensor light transmitted to the second optical fiber 5 is scattered by the second optical fiber 5, and backscattered sensor light returns to the sensor device 9. The backscattered sensor light is scattered light according to changes in the second optical fiber 5. Because the optical amplifier 6 inserted in the second optical fiber 5 transmits light in only one direction, the sensor light cannot pass through the optical amplifier 6. However, because the optical communication system shown in FIG. 1 includes second bypass fibers 8-1 to 8-G for bypassing the optical amplifier 6, the sensor light can propagate to the opposing device 2 via any of the second bypass fibers 8-1 to 8-G. The sensor device 9 receives the backscattered light returned from the second optical fiber 5 and senses the second optical fiber 5 based on the backscattered light.

[0025] The optical communication system shown in FIG. 1 includes G first bypass fibers 7-1 to 7-G and G second bypass fibers 8-1 to 8-G. The first bypass fibers 7-1 to 7-G may be capable of transmitting sensor light having different wavelengths and of propagating backscattered light having different wavelengths. The second bypass fibers 8-1 to 8-G may be capable of transmitting sensor light having different wavelengths and of propagating backscattered light having different wavelengths. In this case, if the sensor device 9 transmits multiple sensor lights having different wavelengths to the first optical fiber 3 to detect multiple types of changes, any of the first bypass fibers 7-1 to 7-G can be configured to pass any of the sensor lights. Similarly, if the sensor device 9 transmits multiple sensor lights having different wavelengths to the second optical fiber 5 to detect multiple types of changes, any of the second bypass fibers 8-1 to 8-G can be configured to pass any of the sensor lights.

[0026] For example, the sensor light for detecting a change in temperature may be configured to pass through each of the first bypass fiber 7-1 and the second bypass fiber 8-1, and backscattered light of the sensor light may be configured to pass through each of the first bypass fiber 7-1 and the second bypass fiber 8-1. For example, the sensor light for detecting a change in vibration may be configured to pass through each of the first bypass fiber 7-G and the second bypass fiber 8-G, and backscattered light of the sensor light may be configured to pass through each of the first bypass fiber 7-G and the second bypass fiber 8-G.

[0027] In the above-described first embodiment, the optical communication system is configured to include a first optical fiber 3 that propagates communication light transmitted from the communication device 1 to the opposing device 2, a second optical fiber 5 that propagates communication light transmitted from the opposing device 2 to the communication device 1, a plurality of first bypass fibers 7-1 to 7-G that bypass the optical amplifier 4 inserted in the first optical fiber 3, and a plurality of second bypass fibers 8-1 to 8-G that bypass the optical amplifier 6 inserted in the second optical fiber 5. The optical communication system also includes a sensor device 9 that transmits sensor light to either the first optical fiber 3 or the second optical fiber 5 and receives backscattered light returned from either the first optical fiber 3 or the second optical fiber 5. Therefore, the optical communication system can sense the communication optical fiber without wiring a sensing optical fiber connecting the communication device 1 and the opposing device 2.

[0028] 1 , the sensor device 9 is disposed on the communication device 1 side. However, this is merely an example, and the sensor device 9 may be disposed on the opposite device 2 side. Even in this case, it is possible to sense the communication optical fiber without wiring a sensing optical fiber connecting the communication device 1 and the opposite device 2.

[0029] The optical communication system shown in Fig. 1 includes a first optical fiber 3, a second optical fiber 5, first bypass fibers 7-1 to 7-G, and second bypass fibers 8-1 to 8-G. The optical communication system shown in Fig. 1 also includes an optical communication system that includes the existing first optical fiber 3 and the existing second optical fiber 5, to which first bypass fibers 7-1 to 7-G, second bypass fibers 8-1 to 8-G, and a sensor device 9 are added.

[0030] Second Embodiment In a second embodiment, an optical communication system including N (N is an integer equal to or greater than 2) opposing devices 2 will be described.

[0031] 3 is a configuration diagram showing an optical communication system according to a second embodiment. In FIG. 3, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts, and detailed description thereof will be omitted. The optical communication system shown in FIG. 3 includes a communication device 1, opposing devices 2-1 to 2-N, a first optical fiber 3, first branched optical fibers 3-1 to 3-N, optical amplifiers 4-1 to 4-N, a second optical fiber 5, second branched optical fibers 5-1 to 5-N, optical amplifiers 6-1 to 6-N, first bypass fibers 7-1-1 to 7-N-G, second bypass fibers 8-1-1 to 8-N-G, a sensor device 9, and an optical route switching device 10.

[0032] Each of the opposite devices 2-1 to 2-N is a communication device having the same function as the opposite device 2 shown in Fig. 1. The first optical fiber 3 is branched into N optical fibers by the optical route switching device 10, and the branched first optical fibers 3-n (n = 1, ..., N) are connected to the opposite device 2-n. An optical amplifier 4-n is inserted into the branched first optical fiber 3-n. The optical amplifier 4-n is realized by, for example, an EDFA or an SOA. The optical amplifier 4-n amplifies the communication light output from the optical route switching device 10 and outputs the amplified communication light to the opposite device 2-n.

[0033] The second optical fiber 5 is branched into N optical fibers by the optical route switching device 10, and the branched second optical fiber 5-n is connected to the opposing device 2-n. An optical amplifier 6-n is inserted into the branched second optical fiber 5-n. The optical amplifier 6-n is realized by, for example, an EDFA or an SOA. The optical amplifier 6-n amplifies the communication light transmitted from the opposing device 2-n and outputs the amplified communication light to the optical route switching device 10.

[0034] Each of the first bypass fibers 7-1-1 to 7-N-G is realized by, for example, a single-mode fiber, a single-core core wire of a multimode fiber, or a multi-core core wire. The first bypass fibers 7-n-g (g = 1, ..., G) are fibers for bypassing the optical amplifier 4-n inserted in the first optical fiber 3-n. Specifically, one end of the first bypass fiber 7-n-g is connected to the input side of the optical amplifier 4-n, and the other end of the first bypass fiber 7-n-g is connected to the output side of the optical amplifier 4-n.

[0035] Each of the second bypass fibers 8-1-1 to 8-N-G is realized by, for example, a single-mode fiber, a single-core core wire of a multimode fiber, or a multi-core core wire. The second bypass fiber 8-n-g is a fiber for bypassing the optical amplifier 6-n inserted in the second optical fiber 5-n. Specifically, one end of the second bypass fiber 8-n-g is connected to the input side of the optical amplifier 6-n, and the other end of the second bypass fiber 8-n-g is connected to the output side of the optical amplifier 6-n.

[0036] The optical route switching device 10 is realized by, for example, a wavelength selective switch (WSS). The optical route switching device 10 outputs communication light transmitted from the communication device 1 to one of the N opposing devices 2-1 to 2-N via one of the branched first optical fibers 3-n among the branched first optical fibers 3-1 to 3-N. The optical route switching device 10 outputs communication light propagated from one of the opposing devices 2-n via the branched second optical fiber 5-n to the communication device 1.

[0037] Next, the operation of the optical communication system shown in Fig. 3 will be described. In the optical communication system shown in Fig. 3, the wavelengths of the communication light related to the N opposite devices 2-1 to 2-N are different from each other, as shown in Fig. 4. The wavelength of the communication light related to the opposite device 2-1 is, for example, λ １，１ ~λ １，Ｇ The wavelength of the communication light for the opposite device 2-(N-1) is, for example, λ Ｋ－１，１~λ Ｋ－１，Ｇ , the wavelength of the communication light related to the opposite device 2-N is, for example, λ Ｋ，１ ~λ Ｋ，Ｇ It should be noted that N may be equal to K, or N may not be equal to K. When N is not equal to K, for example, N<K. FIG. 4 is an explanatory diagram showing the wavelengths of communication light related to N opposing devices 2-1 to 2-N. In FIG. 4, the horizontal axis represents wavelength. In the example of FIG. 4, λ １，１ <...<λ Ｋ，Ｇ－１ <λ Ｋ，Ｇ 4 shows an example in which the communication light is a 128 Gbit / s (32 GBd DP-QPSK) signal with a 1-wavelength channel width of 50 GHz-grid. In the above example, when the communication device 1 transmits communication light to the opposite device 2-1, the communication device 1 transmits the communication light with a wavelength λ １，１ ~λ １，Ｇ to the optical route switching device 10 and transmits the communication light to the opposite device 2-(N-1), Ｋ－１，１ ~λ Ｋ－１，Ｇ When any one or more communication lights among the wavelengths λ Ｋ，１ ~λ Ｋ，Ｇ to the optical route switching device 10. When transmitting communication light to all of the N opposite devices 2-1 to 2-N, the communication device 1 outputs one or more communication light beams of wavelengths λ １，ｇ (g=1,...,G),...,λ Ｋ，ｇ The communication light including the communication light of the above is output to the optical route switching device 10.

[0038] When the optical route switching device 10 receives communication light from the communication device 1, it assigns a wavelength λ １，ｇ If the communication light of wavelength λ is included, １，ｇ By transmitting the communication light of wavelength λ １，ｇ The optical route switching device 10 outputs the communication light of wavelength λ to the opposite device 2-1. Ｋ－１，ｇ If the communication light of wavelength λ is included, Ｋ－１，ｇ By transmitting the communication light of wavelength λ to the first optical fiber 3-(N-1)-g after branching, Ｋ－１，ｇThe optical route switching device 10 outputs the communication light of wavelength λ to the opposite device 2-(N-1). Ｋ，ｇ If the communication light of wavelength λ is included, Ｋ，ｇ By transmitting the communication light of wavelength λ Ｋ，ｇ The communication light is output to the opposite device 2-N.

[0039] The opposite device 2-n (n=1, . . . , N) transmits a signal having a wavelength λ ｋ，ｇ By transmitting the communication light of wavelength λ to the second optical fiber 5-n-g after branching, ｋ，ｇ The optical route switching device 10 outputs communication light of wavelength λ from the opposite device 2-n. ｋ，ｇ When receiving communication light of wavelength λ ｋ，ｇ By transmitting the communication light of wavelength λ to the second optical fiber 5, ｋ，ｇ The optical route switching device 10 outputs communication light of wavelength λ to the communication device 1. For example, when receiving communication light from N opposite devices 2-1 to 2-N, the optical route switching device 10 outputs communication light of wavelength λ １，ｇ , ..., λ Ｋ，ｇ The communication light including the communication light of the first wavelength band is output to the second optical fiber 5 to be output to the communication device 1 .

[0040] 3, the wavelengths of the sensor light of the N opposing devices 2-1 to 2-N are different from each other. For example, the wavelength of the sensor light of the opposing device 2-1 is λ １，１ '~λ １，Ｇ ', the wavelength of the sensor light of the opposing device 2-(N-1) is, for example, λ Ｋ－１，１ '~λ Ｋ－１，Ｇ ', the wavelength of the sensor light of the opposite device 2-N is, for example, λ Ｋ，１ '~λ Ｋ，Ｇ For example, λ １，１ '<・・・<λ Ｋ，ｇ '<λ １，１ <...<λ Ｋ，ｇ , or λ １，１ <...<λ Ｋ，ｇ <λ １，１ '<・・・<λ Ｋ，ｇ ' is.

[0041] When sensing the first branched optical fiber 3-n (n=1, . . . , N), the sensor device 9 senses the wavelength λ ｋ，ｇ The sensor light of wavelength λ′ is transmitted to the first optical fiber 3. ｋ，ｇ The sensor light indicated by the arrows ' is sent by the optical route switching device 10 to the first branched optical fiber 3-n. The sensor light sent to the branched first optical fiber 3-n is scattered by the branched first optical fiber 3-n, and the backscattered light of the sensor light returns to the optical route switching device 10. The optical route switching device 10 outputs the backscattered light to the sensor device 9 by sending the backscattered light to the first optical fiber 3. Because the optical amplifier 4-n inserted in the branched first optical fiber 3-n has a unidirectional light transmission direction, the backscattered light of the sensor light cannot pass through the optical amplifier 4-n. However, because the optical communication system shown in FIG. 3 is provided with a first bypass fiber 7-n-g for bypassing the optical amplifier 4-n, the backscattered light of the sensor light can return to the sensor device 9 via the first bypass fiber 7-n-g. The sensor device 9 receives the backscattered light output from the optical route switching device 10, and senses the branched first optical fiber 3-n based on the backscattered light.

[0042] When sensing the second optical fiber 5-n after branching, the sensor device 9 senses the wavelength λ ｋ－ｇThe sensor light of the first optical fiber 5 is transmitted to the second optical fiber 5. The sensor light transmitted to the second optical fiber 5 is transmitted to the branched second optical fiber 5-n by the optical route switching device 10. The sensor light transmitted to the branched second optical fiber 5-n is scattered by the branched second optical fiber 5-n, and backscattered sensor light returns to the optical route switching device 10. The optical route switching device 10 outputs the backscattered light to the sensor device 9 by transmitting the backscattered light to the second optical fiber 5. Because the optical amplifier 6-n inserted in the branched second optical fiber 5-n has a unidirectional light transmission direction, the sensor light cannot pass through the optical amplifier 6-n. However, since the optical communication system shown in FIG. 3 is provided with a second bypass fiber 8-n-g for bypassing the optical amplifier 6-n, the sensor light can propagate to the opposing device 2-n via the second bypass fiber 8-n-g. The sensor device 9 receives the backscattered light output from the optical route switching device 10, and senses the second branched optical fiber 5-n based on the backscattered light.

[0043] In the second embodiment described above, the optical communication system is configured to include an optical route switching device 10 having N (N is an integer equal to or greater than 2) opposing devices 2, each of which branches a first optical fiber 3 and a second optical fiber 5 into N optical fibers, and which is connected to each opposing device 2-n via each of the branched first optical fibers 3-n and the branched second optical fibers 5-n. The optical communication system also includes a plurality of first bypass fibers 7-n-1 to 7-n-G as first bypass fibers 7-g that bypass optical amplifiers 4-n inserted in the branched first optical fibers 3-n, and a plurality of second bypass fibers 8-n-1 to 8-n-G as second bypass fibers 8-g that bypass optical amplifiers 6-n inserted in the branched second optical fibers 5-n. Therefore, even if the optical communication system has N opposing devices 2-1 to 2-N, it is possible to sense the communication optical fiber without wiring a sensing optical fiber connecting the communication device 1 and the opposing devices 2-1 to 2-N.

[0044] Third Embodiment In a third embodiment, an optical communication system including M (M is an integer of 2 or more) communication devices 1 will be described.

[0045] 5 is a configuration diagram showing an optical communication system according to a third embodiment. In FIG. 5, the same reference numerals as those in FIGS. 1 and 3 indicate the same or corresponding parts, and detailed description thereof will be omitted. The optical communication system shown in FIG. 5 includes communication devices 1-1 to 1-M, opposing devices 2-1 to 2-N, first optical fibers 3-1′ to 3-M′, first optical fibers 3-1 to 3-N after branching, optical amplifiers 4-1 to 4-N, second optical fibers 5-1′ to 5-M′, second optical fibers 5-1 to 5-N after branching, optical amplifiers 6-1 to 6-N, first bypass fibers 7-1-1 to 7-N-G, second bypass fibers 8-1-1 to 8-N-G, a sensor device 9, an optical route switching device 10, and an optical multiplexing / demultiplexing device 11.

[0046] Each of the communication devices 1-1 to 1-M has the same function as the communication device 1 shown in Fig. 1. The communication device 1-m (m = 1, ..., M) is connected to the optical multiplexing / demultiplexing device 11 via a first optical fiber 3-m'. The communication device 1-m is also connected to the optical multiplexing / demultiplexing device 11 via a second optical fiber 5-m'.

[0047] Each of the first optical fibers 3-1' to 3-M' is realized by, for example, a single-mode fiber, a single-core core wire of a multimode fiber, or a multi-core core wire. One end of the first optical fiber 3-m is connected to the communication device 1-m, and the other end of the first optical fiber 3-m is connected to the optical multiplexing / demultiplexing device 11.

[0048] Each of the second optical fibers 5-1' to 5-M' is realized by, for example, a single-mode fiber, a single-core core wire of a multimode fiber, or a multi-core core wire. One end of the second optical fiber 5-m is connected to the communication device 1-m, and the other end of the second optical fiber 5-m is connected to the optical multiplexing / demultiplexing device 11.

[0049] The optical multiplexing / demultiplexing device 11 is realized by, for example, a combination of a multiplexer and a demultiplexer, an arrayed waveguide grating (AWG), or a WSS. The optical multiplexing / demultiplexing device 11 multiplexes communication light transmitted from one or more communication devices 1-m among the M communication devices 1-1 to 1-M, and outputs the multiplexed communication light to the optical route switching device 10. The optical multiplexing / demultiplexing device 11 demultiplexes the communication light output from the optical route switching device 10, and outputs each demultiplexed communication light to one of the communication devices 1-m among the M communication devices 1-1 to 1-M.

[0050] 5, the wavelengths of the communication light of M communication devices 1-1 to 1-M associated with N opposite devices 2-1 to 2-N are different from each other. The wavelength of the communication light of communication device 1-m (m=1, . . . , M) associated with opposite device 2-n (n=1, . . . , N) is λ ｍ－ｋ，１ ~λ ｍ－ｋ，Ｇ Specifically, the wavelength of the communication light of the communication device 1-1 associated with the opposite device 2-1 is, for example, λ １－１，１ ~λ １－１，Ｇ The wavelength of the communication light of the communication device 1-M associated with the opposite device 2-N is, for example, λ Ｍ－Ｋ，１ ~λ Ｍ－Ｋ，Ｇ is.

[0051] When a communication device 1-m (m=1, . . . , M) transmits communication light to a corresponding device 2-n (n=1, . . . , N), the communication device 1-m transmits communication light of wavelength λ 1 through a first optical fiber 3-m′. ｍ－ｋ，ｇ The optical multiplexing / demultiplexing device 11 multiplexes the communication light transmitted from one or more communication devices 1-m among the M communication devices 1-1 to 1-M. The optical multiplexing / demultiplexing device 11 outputs the multiplexed communication light to the optical route switching device 10.

[0052] When the optical route switching device 10 receives the multiplexed communication light from the optical multiplexing / demultiplexing device 11, the optical route switching device 10 assigns a wavelength λ ｍ－ｋ，ｇ If the communication light of wavelength λ is included, ｍ－ｋ，ｇ By transmitting the communication light of wavelength λ to the first optical fiber 3-n after branching, ｍ－ｋ，ｇ The communication light is output to the opposite device 2-n.

[0053] The opposite device 2-n has a wavelength λ ｍ－ｋ，ｇ By transmitting the communication light of wavelength λ to the second optical fiber 5-n, ｍ－ｋ，ｇ The optical route switching device 10 transmits the communication light of wavelength λ 1 from the opposite device 2-n. ｍ－ｋ，ｇ When receiving communication light of wavelength λ ｍ－ｋ，ｇ The communication light is output to the optical multiplexer / demultiplexer 11.

[0054] The optical multiplexer / demultiplexer 11 receives the wavelength λ ｍ－ｋ，ｇ When receiving communication light of wavelength λ ｍ－ｋ，ｇ By transmitting the communication light of wavelength λ to the second optical fiber 5-m′, ｍ－ｋ，ｇ The communication light is output to the communication device 1-m.

[0055] 5, the wavelengths of the sensor light of M communication devices 1-1 to 1-M associated with N opposite devices 2-1 to 2-N are different from each other. The wavelength of the sensor light of communication device 1-m (m=1, . . . , M) associated with opposite device 2-n (n=1, . . . , N) is λ ｍ－ｋ，ｇ Specifically, the wavelength of the sensor light of the communication device 1-1 associated with the opposite device 2-1 is, for example, λ １－１，ｇ ', the wavelength of the sensor light of the communication device 1-M associated with the opposite device 2-N is, for example, λ Ｍ－Ｋ，ｇ ' is.

[0056] When sensing the first branched optical fiber 3-n (n=1, . . . , N), the sensor device 9 senses the wavelength λ ｍ－ｋ，ｇ The sensor light of wavelength λ′ is transmitted to the first optical fiber 3-m. ｍ－ｋ，ｇ The sensor light of wavelength λ ′ is output to the optical route switching device 10 via the optical multiplexing / demultiplexing device 11. ｍ－ｋ，ｇThe sensor light of the branched first optical fiber 3-m' is sent by the optical route switching device 10 to the branched first optical fiber 3-n. The sensor light sent to the branched first optical fiber 3-n is scattered by the branched first optical fiber 3-n, and backscattered light of the sensor light returns to the optical route switching device 10. The optical route switching device 10 outputs the backscattered light to the optical multiplexing / demultiplexing device 11. The optical multiplexing / demultiplexing device 11 outputs the backscattered light to the sensor device 9 by sending it to the first optical fiber 3-m'. The sensor device 9 receives the backscattered light output from the optical multiplexing / demultiplexing device 11, and senses the branched first optical fiber 3-n based on the backscattered light.

[0057] When sensing the second optical fiber 5-n after branching, the sensor device 9 senses the wavelength λ ｍ－ｋ，ｇ The sensor light having a wavelength λ 1 is transmitted to the second optical fiber 5-n. The sensor light transmitted to the second optical fiber 5-n is output to the optical route switching device 10 via the optical multiplexing / demultiplexing device 11, and is converted to a signal having a wavelength λ 1 . ｍ－ｋ，ｇ The sensor light of the first branch optical fiber 5-m' is sent by the optical route switching device 10 to the second branched optical fiber 5-n. The sensor light sent to the second branched optical fiber 5-n is scattered by the second branched optical fiber 5-n, and backscattered light of the sensor light returns to the optical route switching device 10. The optical route switching device 10 outputs the backscattered light to the optical multiplexing / demultiplexing device 11. The optical multiplexing / demultiplexing device 11 outputs the backscattered light to the sensor device 9 by sending it to the second optical fiber 5-m'. The sensor device 9 receives the backscattered light output from the optical multiplexing / demultiplexing device 11, and senses the second branched optical fiber 5-n based on the backscattered light.

[0058] In the above third embodiment, the optical communication system is configured to include M (M is an integer of 2 or more) communication devices, and an optical multiplexing / demultiplexing device 11 that multiplexes communication light transmitted from one or more communication devices 1-m among the M communication devices 1-1 to 1-M, outputs the multiplexed communication light to an optical route switching device 10, and demultiplexes the communication light output from the optical route switching device 10, and outputs each demultiplexed communication light to any one of the M communication devices 1-1 to 1-M. Therefore, even when the optical route switching device 10 includes M communication devices 1-1 to 1-M, it is possible for the optical route switching device 10 to sense the communication optical fiber without wiring a sensing optical fiber connecting the communication devices 1-1 to 1-M and the opposing devices 2-1 to 2-N.

[0059] Fourth Embodiment In a fourth embodiment, an optical communication system including P (P is an integer equal to or greater than 2) sensor devices 9-1 to 9-P will be described.

[0060] 6 is a configuration diagram showing an optical communication system according to a fourth embodiment. In FIG. 6, the same reference numerals as those in FIG. 1, FIG. 3, and FIG. 5 indicate the same or corresponding parts, and therefore detailed description thereof will be omitted. The optical communication system shown in FIG. 6 includes communication devices 1-1 to 1-M, opposing devices 2-1 to 2-N, first optical fibers 3-1′ to 3-M′, first optical fibers 3-1 to 3-N after branching, optical amplifiers 4-1 to 4-N, second optical fibers 5-1′ to 5-M′, second optical fibers 5-1 to 5-N after branching, optical amplifiers 6-1 to 6-N, first bypass fibers 7-1-1 to 7-N-G, second bypass fibers 8-1-1 to 8-N-G, sensor devices 9-1 to 9-P, an optical route switching device 10, and an optical multiplexing / demultiplexing device 11.

[0061] Each of the sensor devices 9-1 to 9-P has the same function as the sensor device 9 shown in Fig. 1. The sensor device 9-1 emits sensor light for detecting temperature changes, for example, the sensor device 9-2 emits sensor light for detecting vibration changes, and the sensor device 9-P emits sensor light for detecting stress changes. The wavelengths of these P sensor lights are different from each other.

[0062] Next, the operation of the optical communication system shown in Fig. 6 will be described. However, other than the sensor devices 9-1 to 9-P, the system is the same as the optical communication system shown in Fig. 5. Therefore, the operation of the sensor devices 9-1 to 9-P will be mainly described here.

[0063] When sensing the first optical fiber 3-n (n = 1, ..., N) after branching, one of the P sensor devices 9-1 to 9-P (p = 1, ..., P) transmits sensor light to the first optical fiber 3-m (m = 1, ..., M) to transmit the sensor light to the optical multiplexing and demultiplexing device 11. For example, when detecting a temperature change in the first optical fiber 3-n after branching, the sensor device 9-1 transmits the sensor light, and when detecting a vibration change in the first optical fiber 3-n after branching, the sensor device 9-2 transmits the sensor light. The optical multiplexing and demultiplexing device 11 outputs the sensor light transmitted from the sensor device 9-p to the optical route switching device 10 and outputs backscattered light of the sensor light output from the optical route switching device 10 to the sensor device 9-p. The sensor device 9-p receives the backscattered light output from the optical multiplexing / demultiplexing device 11, and senses the first branched optical fiber 3-n based on the backscattered light.

[0064] When sensing the branched second optical fiber 5-n, one of the P sensor devices 9-1 to 9-P, 9-p, transmits sensor light to the second optical fiber 5-m, thereby transmitting the sensor light to the optical multiplexing and demultiplexing device 11. For example, when detecting a temperature change in the branched second optical fiber 5-n, the sensor device 9-1 transmits the sensor light, and when detecting a vibration change in the branched second optical fiber 5-n, the sensor device 9-2 transmits the sensor light. The optical multiplexing and demultiplexing device 11 outputs the sensor light transmitted from the sensor device 9-p to the optical path switching device 10, and outputs backscattered light of the sensor light output from the optical path switching device 10 to the sensor device 9-p. The sensor device 9-p receives the backscattered light output from the optical multiplexing and demultiplexing device 11 and senses the branched second optical fiber 5-n based on the backscattered light.

[0065] In the above fourth embodiment, the optical communication system is configured so that there are P (P is an integer of 2 or more) sensor devices 9, and the optical multiplexing and demultiplexing device 11 outputs sensor light transmitted from each of the P sensor devices to the optical route switching device 10, and outputs backscattered light output from the optical route switching device 10 to the sensor device 9-p. Therefore, the optical communication system can sense the communication optical fiber without wiring sensing optical fibers connecting the communication devices 1-1 to 1-M and the opposing devices 2-1 to 2-N, and can detect multiple types of changes in the communication optical fiber.

[0066] Fifth Embodiment In the fifth embodiment, an optical communication system will be described in which an optical multiplexing / demultiplexing device 12 outputs, to a sensor device 9, backscattered light within a pass wavelength band among backscattered light output from an optical route switching device 10, and blocks backscattered light outside the pass wavelength band.

[0067] 7 is a configuration diagram showing an optical communication system according to a fifth embodiment. In FIG. 7, the same reference numerals as those in FIGS. 1, 3, 5, and 6 indicate the same or corresponding parts, and detailed description thereof will be omitted. The optical communication system shown in FIG. 7 includes communication devices 1-1 to 1-M, opposing devices 2-1 to 2-N, first optical fibers 3-1′ to 3-M′, first optical fibers 3-1 to 3-N after branching, optical amplifiers 4-1 to 4-N, second optical fibers 5-1′ to 5-M′, second optical fibers 5-1 to 5-N after branching, optical amplifiers 6-1 to 6-N, first bypass fibers 7-1-1 to 7-N-G, second bypass fibers 8-1-1 to 8-N-G, a sensor device 9, an optical route switching device 10, and an optical multiplexing / demultiplexing device 12.

[0068] The optical multiplexing / demultiplexing device 12 is realized by, for example, a combination of a multiplexer and a demultiplexer, an AWG, or a WSS. Similar to the optical multiplexing / demultiplexing device 11 shown in FIG. 5 , the optical multiplexing / demultiplexing device 12 multiplexes communication light transmitted from one or more communication devices 1-m among the M communication devices 1-1 to 1-M, and outputs the multiplexed communication light to the optical route switching device 10. The optical multiplexing / demultiplexing device 12 demultiplexes the communication light output from the optical route switching device 10, and outputs each demultiplexed communication light to one of the communication devices 1-m among the M communication devices 1-1 to 1-M. Unlike the optical multiplexing / demultiplexing device 11 shown in FIG. 5 , the optical multiplexing / demultiplexing device 12 outputs backscattered light within the pass wavelength band of the backscattered light output from the optical route switching device 10 to the sensor device 9, and blocks backscattered light outside the pass wavelength band.

[0069] In the optical communication system shown in Fig. 7, the optical multiplexing / demultiplexing device 12 is applied to the optical communication system shown in Fig. 5. However, this is merely an example, and the optical multiplexing / demultiplexing device 12 may also be applied to the optical communication system shown in Fig. 6.

[0070] Next, the operation of the optical communication system shown in Fig. 7 will be described. However, apart from the optical multiplexing / demultiplexing device 12, the optical communication system is the same as the optical communication system shown in Fig. 5. Therefore, only the operation of the optical multiplexing / demultiplexing device 12 will be described here.

[0071] When sensing the branched first optical fiber 3-n (n = 1, ..., N) or the branched second optical fiber 5-n, the optical multiplexing / demultiplexing device 12 acquires the backscattered light output from the optical route switching device 10. The optical multiplexing / demultiplexing device 12 is equipped with, for example, a bandpass filter having a desired pass wavelength band. Alternatively, the optical multiplexing / demultiplexing device 12 has wavelengths selected by a WSS to have the desired pass wavelength band. By providing the backscattered light to the bandpass filter or WSS, the optical multiplexing / demultiplexing device 12 outputs the backscattered light output from the optical route switching device 10 to the sensor device 9 if the backscattered light output from the optical route switching device 10 is backscattered light within the pass wavelength band. The optical multiplexing / demultiplexing device 12 blocks the backscattered light output from the optical route switching device 10 if the backscattered light is backscattered light outside the pass wavelength band.

[0072] In the above-described fifth embodiment, the optical communication system is configured so that the optical multiplexing / demultiplexing device 12 outputs, to the sensor device 9, backscattered light within the pass wavelength band, out of the backscattered light output from the optical route switching device 10, and blocks backscattered light outside the pass wavelength band. Therefore, the optical communication system can sense the communication optical fiber without wiring a sensing optical fiber connecting the communication devices 1-1 to 1-M and the opposing devices 2-1 to 2-N, and can prevent degradation of sensing accuracy due to noise, etc.

[0073] Sixth Embodiment In a sixth embodiment, an optical communication system will be described in which an optical multiplexing / demultiplexing device 11 includes a first optical multiplexing / demultiplexing device 11a and a second optical multiplexing / demultiplexing device 11b.

[0074] 8 is a configuration diagram showing an optical communication system according to a sixth embodiment. In FIG. 8, the same reference numerals as those in FIGS. 1, 3, and 5 to 7 indicate the same or corresponding parts, and detailed description thereof will be omitted. The optical communication system shown in FIG. 8 includes communication devices 1-1 to 1-M, opposing devices 2-1 to 2-N, first optical fibers 3-1′ to 3-M′, first optical fibers 3-1 to 3-N after branching, optical amplifiers 4-1 to 4-N, second optical fibers 5-1′ to 5-M′, second optical fibers 5-1 to 5-N after branching, optical amplifiers 6-1 to 6-N, first bypass fibers 7-1-1 to 7-N-G, second bypass fibers 8-1-1 to 8-N-G, sensor devices 9-1 to 9-P, an optical route switching device 10, a first optical multiplexer / demultiplexer 11a, and a second optical multiplexer / demultiplexer 11b.

[0075] The first optical multiplexer / demultiplexer 11a is realized by, for example, a combination of a multiplexer and a demultiplexer, an AWG, or a WSS. The first optical multiplexer / demultiplexer 11a multiplexes communication light transmitted from one or more communication devices 1-m among the M communication devices 1-1 to 1-M, and outputs the multiplexed communication light to the optical route switching device 10. The first optical multiplexer / demultiplexer 11a demultiplexes the communication light output from the optical route switching device 10, and outputs each demultiplexed communication light to one of the communication devices 1-m among the M communication devices 1-1 to 1-M.

[0076] The second optical multiplexer / demultiplexer 11b is realized by, for example, a combination of a multiplexer and a demultiplexer, an AWG, or a WSS. The second optical multiplexer / demultiplexer 11b outputs sensor light transmitted from one or more sensor devices 9-p (p=1, ..., P) among the P sensor devices 9-1 to 9-P to the optical route switching device 10. The second optical multiplexer / demultiplexer 11b outputs backscattered light of the sensor light transmitted from the optical route switching device 10 to the sensor device 9-n that transmitted the sensor light.

[0077] In the optical communication system shown in Fig. 8, the first optical multiplexer / demultiplexer 11a and the second optical multiplexer / demultiplexer 11b are applied to the optical multiplexer / demultiplexer 11 of the optical communication system shown in Fig. 6. However, this is merely an example, and the first optical multiplexer / demultiplexer 11a and the second optical multiplexer / demultiplexer 11b may also be applied to the optical multiplexer / demultiplexer 11 of the optical communication system shown in Fig. 5 or the optical multiplexer / demultiplexer 12 of the optical communication system shown in Fig. 7.

[0078] In the optical communication system shown in Fig. 8, the optical multiplexing / demultiplexing device 11 includes a first optical multiplexer / demultiplexer 11a for multiplexing / demultiplexing communication light and a second optical multiplexer / demultiplexer 11b for multiplexing sensor light and demultiplexing backscattered light, separately from the first optical multiplexer / demultiplexer 11a for multiplexing / demultiplexing communication light. As a result, the optical multiplexing / demultiplexing device 11 shown in Fig. 8 can reduce interference between the communication light and the sensor light or between the communication light and the backscattered light more than an optical multiplexer / demultiplexer that combines the functions of multiplexing / demultiplexing communication light and sensor light.

[0079] Seventh Embodiment In a seventh embodiment, an optical communication system including a selection device 13 that connects any one of P sensor devices 9-1 to 9-P (p=1, . . . , P) to an optical multiplexing / demultiplexing device 11 will be described.

[0080] 9 is a configuration diagram showing an optical communication system according to a seventh embodiment. In FIG. 9, the same reference numerals as those in FIGS. 1, 3, and 5 to 8 indicate the same or corresponding parts, and detailed description thereof will be omitted. The optical communication system shown in FIG. 9 includes communication devices 1-1 to 1-M, opposing devices 2-1 to 2-N, first optical fibers 3-1′ to 3-M′, first optical fibers 3-1 to 3-N after branching, optical amplifiers 4-1 to 4-N, second optical fibers 5-1′ to 5-M′, second optical fibers 5-1 to 5-N after branching, optical amplifiers 6-1 to 6-N, first bypass fibers 7-1-1 to 7-N-G, second bypass fibers 8-1-1 to 8-N-G, sensor devices 9-1 to 9-P, an optical route switching device 10, an optical multiplexing / demultiplexing device 11, a selection device 13, and an optical terminator 14.

[0081] The selection device 13 has a plurality of input / output ports, and the P sensor devices 9-1 to 9-P and the optical multiplexing / demultiplexing device 11 are each connected to a different input / output port. The selection device 13 connects any one of the sensor devices 9-p (p = 1, ..., P) among the P sensor devices 9-1 to 9-P to the optical multiplexing / demultiplexing device 11. Of the multiple input / output ports that the selection device 13 has, one input / output port (one end) is optically terminated by an optical terminator 14. The optical terminator 14 is a terminator that terminates one end of the selection device 13. In the optical communication system shown in FIG. 9 , the selection device 13 is provided outside the optical multiplexing / demultiplexing device 11. However, this is merely an example, and the selection device 13 may be provided inside the optical multiplexing / demultiplexing device 11, for example.

[0082] Next, the operation of the optical communication system shown in Fig. 9 will be described. However, apart from the selection device 13, the optical communication system is the same as the optical communication system shown in Fig. 6. Therefore, the operation of the selection device 13 will be mainly described here.

[0083] The selection device 13 connects any one of the sensor devices 9-p (p=1, ..., P) among the P sensor devices 9-1 to 9-P to the optical multiplexing and demultiplexing device 11. When the selection device 13 connects the sensor device 9-p (p=1, ..., P) to the optical multiplexing and demultiplexing device 11, the sensor light transmitted from the sensor device 9-p is output to the optical multiplexing and demultiplexing device 11 via the selection device 13. In addition, the backscattered light output from the optical multiplexing and demultiplexing device 11 is output to the sensor device 9-p via the selection device 13.

[0084] Of the multiple input / output ports that the selection device 13 has, one input / output port is optically terminated by the optical terminator 14. As a result, when the sensor device 9-p transmits sensor light, for example, in the case where the opposing device 2-n transmits sensor light, the sensor light transmitted from the opposing device 2-n is optically terminated, thereby making it possible to prevent multiple reflections of the sensor light.

[0085] In the seventh embodiment described above, the optical communication system is configured to include a selection device 13 that connects any one of the P sensor devices 9-1 to 9-P, 9-p, to the optical multiplexing / demultiplexing device 11. Therefore, the optical communication system can detect multiple types of changes in the communication optical fiber without wiring sensing optical fibers that connect the communication devices 1-1 to 1-M and the opposing devices 2-1 to 2-N.

[0086] Eighth Embodiment In the eighth embodiment, an optical communication system will be described in which a first bypass fiber 7-g (g=1, ..., G) is provided with a wavelength division multiplexing filter 7a or a wavelength division multiplexing coupler 7b as a connection component for the first optical fiber 3, and a second bypass fiber 8-g is provided with a wavelength division multiplexing filter 8a or a wavelength division multiplexing coupler 8b as a connection component for the second optical fiber 5.

[0087] Figure 10 is a configuration diagram showing a part of an optical communication system according to an eighth embodiment. In Figure 10, the same reference numerals as those in Figures 1, 3, and 5 to 9 indicate the same or corresponding parts, and detailed description thereof will be omitted. The first bypass fiber 7-g (g = 1, ..., G) includes a wavelength division multiplexing filter 7a or a wavelength division multiplexing coupler 7b as a connecting component to the first optical fiber 3. The second bypass fiber 8-g includes a wavelength division multiplexing filter 8a or a wavelength division multiplexing coupler 8b as a connecting component to the second optical fiber 5.

[0088] In the optical communication system shown in Fig. 10, wavelength division multiplexing filters 7a and 8a or wavelength division multiplexing couplers 7b and 8b are applied to the optical communication system shown in Fig. 1. However, this is merely an example, and the wavelength division multiplexing filters 7a and 8a or wavelength division multiplexing couplers 7b and 8b may also be applied to the optical communication systems shown in Fig. 3 and Figs. 5 to 9.

[0089] 10 , the first bypass fiber 7-g includes a wavelength division multiplexing filter 7a or a wavelength division multiplexing coupler 7b as a connection component for the first optical fiber 3, and the second bypass fiber 8-g includes a wavelength division multiplexing filter 8a or a wavelength division multiplexing coupler 8b as a connection component for the second optical fiber 5. The wavelength division multiplexing filters 7a, 8a and the wavelength division multiplexing couplers 7b, 8b are each passive components. Therefore, for example, even if supervisory control communication cannot be established between devices and the connection components for the first optical fiber 3 and the second optical fiber 5 cannot be actively controlled, or even if the optical amplifiers 4, 6 are powered off, sensing of the communication optical fiber is possible.

[0090] Ninth Embodiment In a ninth embodiment, an optical communication system will be described in which a first bypass fiber 7-g (g=1, . . . , G) includes a bidirectional optical amplifier 7c that does not include an optical isolator, and a second bypass fiber 8-g includes a bidirectional optical amplifier 8c that does not include an optical isolator.

[0091] Fig. 11 is a configuration diagram showing a part of an optical communication system according to a ninth embodiment. In Fig. 11, the same reference numerals as those in Figs. 1, 3, and 5 to 10 indicate the same or corresponding parts, and detailed description thereof will be omitted. The optical amplifier 7c is realized by, for example, a semiconductor optical amplifier (SOA). The optical amplifier 7c is inserted into a first bypass fiber 7-g (g = 1, ..., G). The optical amplifier 7c is a bidirectional optical amplifier that does not include an optical isolator, and amplifies both the sensor light and the backscattered light.

[0092] The optical amplifier 8c is realized by, for example, an SOA. The optical amplifier 8c is inserted into the second bypass fiber 8-g (g=1, ..., G). The optical amplifier 8c is a bidirectional optical amplifier that does not include an optical isolator, and amplifies both the sensor light and the backscattered light.

[0093] In the optical communication system shown in Fig. 11, the optical amplifier 7c and the optical amplifier 8c are each applied to the optical communication system shown in Fig. 1. However, this is merely an example, and the optical amplifier 7c and the optical amplifier 8c may each be applied to the optical communication system shown in Fig. 3 or any one of Figs. 5 to 10.

[0094] In the optical communication system shown in FIG. 11 , an optical amplifier 7c is inserted into the first bypass fiber 7-g, and therefore the sensor light and backscattered light carried by the first bypass fiber 7-g are each amplified. The optical amplifier 7c is a bidirectional optical amplifier, and therefore the sensor light and backscattered light can each pass through the optical amplifier 7c. Furthermore, an optical amplifier 8c is inserted into the second bypass fiber 8-g, and therefore the sensor light and backscattered light carried by the second bypass fiber 8-g are each amplified. The optical amplifier 8c is a bidirectional optical amplifier, and therefore the sensor light and backscattered light can each pass through the optical amplifier 8c. As a result, the optical communication system shown in FIG. 11 can improve the sensing accuracy of the sensor device 9 compared to the optical communication system shown in FIG. 1 .

[0095] Tenth Embodiment In a tenth embodiment, an optical communication system will be described in which a first bypass fiber 7-g (g=1, . . . , G) includes an optical bandpass filter 7d that passes the sensor light and the backward propagating light, and a second bypass fiber 8-g includes an optical bandpass filter 8d that passes the sensor light and the backward propagating light.

[0096] FIG. 12 is a configuration diagram showing a portion of an optical communication system according to a tenth embodiment. In FIG. 12, the same reference numerals as those in FIGS. 1, 3, and 5 to 11 indicate the same or corresponding parts, and detailed description thereof will be omitted. The optical bandpass filter 7d is realized, for example, by a dielectric multilayer film or a diffraction grating. The optical bandpass filter 7d is inserted in the first bypass fiber 7-g (g = 1, ..., G). The optical bandpass filter 7d passes the sensor light and backward propagating light and blocks noise and the like. The optical bandpass filter 8d is realized, for example, by a dielectric multilayer film or a diffraction grating. The optical bandpass filter 8d is inserted in the second bypass fiber 8-g (g = 1, ..., G). The optical bandpass filter 8d passes the sensor light and backward propagating light and blocks noise and the like.

[0097] In the optical communication system shown in Fig. 12, the optical bandpass filter 7d and the optical bandpass filter 8d are each applied to the optical communication system shown in Fig. 1. However, this is merely an example, and the optical bandpass filter 7d and the optical bandpass filter 8d may each be applied to the optical communication system shown in Fig. 3 or any one of Figs. 5 to 11.

[0098] In the optical communication system shown in Fig. 12, an optical bandpass filter 7d is inserted into the first bypass fiber 7-g, so that the sensor light and backscattered light carried by the first bypass fiber 7-g can pass through while blocking noise and the like. Furthermore, an optical bandpass filter 8d is inserted into the second bypass fiber 8-g, so that the sensor light and backscattered light carried by the second bypass fiber 8-g can pass through while blocking noise and the like. As a result, the optical communication system shown in Fig. 12 can improve the sensing accuracy of the sensor device 9 compared to the optical communication system shown in Fig. 1.

[0099] Eleventh Embodiment In an eleventh embodiment, an optical communication system in which a third optical fiber 15 is connected to an optical route switching device 10 will be described.

[0100] Fig. 13 is a configuration diagram showing an optical communication system according to an eleventh embodiment. In Fig. 13, the same reference numerals as those in Figs. 1, 3, and 5 to 12 indicate the same or corresponding parts, and detailed description thereof will be omitted. The third optical fiber 15 is realized by, for example, a single-mode fiber, a single-core core wire of a multimode fiber, or a multi-core core wire. The third optical fiber 15 is an optical fiber dedicated to a sensor, one end of which is connected to the optical route switching device 10.

[0101] In the optical communication system shown in Fig. 13, the third optical fiber 15 is applied to the optical communication system shown in Fig. 5. However, this is merely an example, and the third optical fiber 15 may be applied to the optical communication system shown in Fig. 3 or any one of Figs. 6 to 12.

[0102] 13, in addition to the branched first optical fibers 3-1 to 3-N and the branched second optical fibers 5-1 to 5-N, a third optical fiber 15 is connected to the optical route switching device 10. This makes it possible to sense not only the branched first optical fibers 3-1 to 3-N and the branched second optical fibers 5-1 to 5-N, but also the third optical fiber 15.

[0103] 14 is a configuration diagram showing another optical communication system according to the eleventh embodiment. As shown in FIG. 14, the third optical fiber 15 may be wound around a power cable to realize a current transformer (CT) that measures the current flowing through the power cable. In this case, sensing can be performed not only on the first branched optical fibers 3-1 to 3-N and the second branched optical fibers 5-1 to 5-N, but also on the third optical fiber 15.

[0104] Embodiment 12. In the first to eleventh embodiments, the optical communication system includes a plurality of first bypass fibers 7-g (g = 1, ..., G), 7-n-g that bypass the optical amplifiers 4, 4-n inserted in the first optical fibers 3, 3-n (n = 1, ..., N), and a plurality of second bypass fibers 8-g, 8-n-g that bypass the optical amplifiers 6, 6-n inserted in the second optical fibers 5, 5-n. In the twelfth embodiment, an optical communication system is described in which one or more communication light bypass fibers 21 are wired to the first optical fiber 3 (or the first optical fiber 3-n after branching) to connect a plurality of optical amplifiers 4 (or optical amplifiers 4-n) in parallel, and one or more communication light bypass fibers 22 are wired to the second optical fiber 5 (or the second optical fiber 5-n after branching) to connect a plurality of optical amplifiers 6 (or optical amplifiers 6-n) in parallel.

[0105] FIG. 15 is a configuration diagram showing an optical communication system according to a twelfth embodiment. In FIG. 15, the same reference numerals as those in FIGS. 1, 3, and 5 to 14 indicate the same or corresponding parts, and detailed description thereof will be omitted. In the optical communication system shown in FIG. 15, a bandpass filter 3a is inserted in series with an optical amplifier 4 (or optical amplifier 4-n), and a bandpass filter 5a is inserted in series with an optical amplifier 6 (or optical amplifier 6-n). Bandpass filters 23 having different pass wavelength bands are inserted in each of one or more communication light bypass fibers 21, and the pass wavelength bands of the respective bandpass filters 23 are different from the pass wavelength band of the bandpass filter 3a. Furthermore, bandpass filters 24 having different pass wavelength bands are inserted in each of one or more communication light bypass fibers 22, and the pass wavelength bands of the respective bandpass filters 24 are different from the pass wavelength band of the bandpass filter 5a. This allows the communication devices 1, 1-m (m=1, . . . , M) and the opposing devices 2, 2-n to transmit and receive a plurality of communication lights with different wavelengths.

[0106] In addition, the present disclosure allows for free combination of the respective embodiments, modification of any of the components of the respective embodiments, or omission of any of the components of the respective embodiments.

[0107] The present disclosure is suitable for optical communication systems.

[0108] 1 Communication device, 2, 2-1 to 2-N Opposite device, 3, 3-1' to 3-M' First optical fiber, 3-1 to 3-N First optical fiber after branching, 3a Bandpass filter, 4, 4-1 to 4-N Optical amplifier, 5, 5-1' to 5-M' Second optical fiber, 5-1 to 5-N Second optical fiber after branching, 5a Bandpass filter, 6, 6-1 to 6-N Optical amplifier, 7-1 to 7-G, 7-1-1 to 7-N-G First bypass fiber, 7a Wavelength division multiplexing filter, 7b Wavelength division multiplexing coupler, 7c Optical amplifier, 7d Optical bandpass filter, 8-1 to 8-G, 8-1-1 to 8-N-G Second bypass fiber, 8a Wavelength division multiplexing filter, 8b Wavelength division multiplexing coupler, 8c Optical amplifier, 8d Optical bandpass filter, 9, 9-1 to 9-P Sensor device, 10 optical path switching device, 11 optical multiplexer / demultiplexer, 11a first optical multiplexer / demultiplexer, 11b second optical multiplexer / demultiplexer, 12 optical multiplexer / demultiplexer, 13 selection device, 14 optical terminator, 15 third optical fiber, 21, 22 communication optical bypass fiber, 23, 24 bandpass filter.

Claims

1. A first optical fiber that propagates communication light transmitted from a communication device to a counter device, a second optical fiber that propagates communication light transmitted from the counter device to the communication device, a plurality of first bypass fibers that bypass an optical amplifier inserted in the first optical fiber, a plurality of second bypass fibers that bypass an optical amplifier inserted in the second optical fiber, and a sensor device that sends sensor light to either the first optical fiber or the second optical fiber and receives backscattered light that has returned from either the first optical fiber or the second optical fiber. An optical communication system comprising.

2. There are N (N is an integer of 2 or more) counter devices, an optical path switching device that branches each of the first optical fiber and the second optical fiber into N, and is connected to each counter device via the branched first optical fiber and the branched second optical fiber, respectively, and as the first bypass fiber, a plurality of first bypass fibers that bypass an optical amplifier inserted in each branched first optical fiber, and as the second bypass fiber, a plurality of second bypass fibers that bypass an optical amplifier inserted in each branched second optical fiber. The optical communication system according to claim 1, characterized in that it comprises.

3. There are M (M is an integer of 2 or more) communication devices, and among the M communication devices, multiplexes communication light transmitted from any one or more communication devices, outputs the multiplexed communication light to the optical path switching device, demultiplexes the communication light output from the optical path switching device, and outputs each demultiplexed communication light to any one of the M communication devices. The optical communication system according to claim 2, characterized in that it comprises an optical multiplexer / demultiplexer.

4. The optical multiplexer / demultiplexer sends the sensor light transmitted from the sensor device to either the branched first optical fiber or the branched second optical fiber via the optical path switching device, and outputs the backscattered light that has returned from either the branched first optical fiber or the branched second optical fiber to the sensor device. The optical communication system according to claim 3, characterized in that.

5. There are P (P is an integer of 2 or more) sensor devices, and the optical multiplexer / demultiplexer outputs the sensor light transmitted from each of the P sensor devices to the optical path switching device, and outputs the backscattered light output from the optical path switching device to the sensor device that is the transmission source of the sensor light. The optical communication system according to claim 3, characterized in that.

6. The optical multiplexer / demultiplexer outputs the backscattered light within the passing wavelength band among the backscattered light output from the optical path switching device to the sensor device, and blocks the backscattered light outside the passing wavelength band. The optical communication system according to claim 3, characterized in that.

7. Among the M communication devices, the optical multiplexer / demultiplexer multiplexes the communication light transmitted from any one or more of the communication devices, outputs the multiplexed communication light to the optical path switching device, demultiplexes the communication light output from the optical path switching device, and outputs each demultiplexed communication light to any one of the M communication devices. A first optical multiplexer / demultiplexer, and among the P sensor devices, outputs the sensor light transmitted from any one or more of the sensor devices to the optical path switching device, and outputs the backscattered light output from the optical path switching device to the sensor device that is the transmission source of the sensor light. The optical communication system according to claim 5, characterized in that it comprises a second optical multiplexer / demultiplexer.

8. The optical communication system according to claim 5, characterized in that it comprises a selection device for connecting any one of the P sensor devices to the optical multiplexer / demultiplexer.

9. The optical communication system according to claim 8, characterized in that one end of the selection device is optically terminated.

10. Each of the first optical fiber and the second optical fiber is any one of a single-mode fiber, a single-core core of a multi-mode fiber, or a multi-core core. The optical communication system according to claim 1, characterized in that.

11. The first bypass fiber is provided with a wavelength division multiplexing filter or a wavelength division multiplexing coupler as a connecting component for the first optical fiber, and the second bypass fiber is provided with a wavelength division multiplexing filter or a wavelength division multiplexing coupler as a connecting component for the second optical fiber. The optical communication system according to claim 1, characterized in that.

12. The optical communication system according to claim 1, wherein each of the first bypass fiber and the second bypass fiber includes a bidirectional optical amplifier that does not include an optical isolator.

13. The optical communication system according to claim 1, wherein each of the first bypass fiber and the second bypass fiber includes an optical bandpass filter that allows the sensor light and the backward-propagating light to pass therethrough.

14. The optical communication system according to claim 2, wherein a third optical fiber is connected to the optical path switching device in addition to the first optical fiber after branching and the optical fiber after branching.

15. The optical communication system according to claim 1, wherein a plurality of optical amplifiers inserted in the first optical fiber are connected in parallel, and a plurality of optical amplifiers inserted in the second optical fiber are connected in parallel.

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