Bidirectional optical amplifier, bidirectional optical amplification device, and bidirectional optical amplification method

Abstract

According to the present invention, to implement a bidirectional optical amplifier that consumes less power and is capable of amplifying light in two directions, the bidirectional optical amplifier includes: a first input-output port; a second input-output port; a first optical amplifier for amplifying light in a first direction that propagates through a first optical path connecting the first input-output port to the second input-output port; a second optical amplifier for amplifying light in a second direction that propagates through a second optical path connecting the first input-output port to the second input-output port and being different from the first optical path, the second optical amplifier being disposed in parallel with the first optical amplifier; an optical path configuration unit that configures at least one of the first optical path and the second optical path; and an excitation light supply unit that supplies excitation light to one of the first optical amplifier and the second optical amplifier.

Description

[Technical field]

[0001] The present invention relates to a bidirectional optical amplifier and a bidirectional optical amplification method. [Background technology]

[0002] General optical amplifiers, such as optical fiber amplifiers, can only amplify light in a single direction. For this reason, bidirectional optical amplifiers that combine multiple optical amplifiers have been proposed to amplify light transmitted in both directions through a single core of an optical fiber. For example, Patent Documents 1-3 describe bidirectional optical amplifiers that use optical circulators. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 183455 [Patent Document 2] Special Publication No. 2013-513984 [Patent Document 3] JP 2003-338793 A Summary of the Invention [Problem to be solved by the invention]

[0004] The optical amplifiers described in Patent Documents 1-3 all have the function of amplifying bidirectional optical signals by operating two optical amplifiers simultaneously. However, in the optical amplifiers described in Patent Documents 1-3, two optical amplifiers are always in operation. That is, even when the transmission direction of an optical signal is switched over time to perform bidirectional transmission, the optical amplifier in the direction in which the optical signal is not transmitted is in operation. For this reason, the bidirectional optical amplifiers described in Patent Documents 1-3 have the problem that they consume large power when the transmission direction of an optical signal is switched over time to perform bidirectional transmission. (Objective of the Invention) An object of the present invention is to provide a technique for realizing a bidirectional optical amplifier that consumes little power and is capable of amplifying light in both directions when bidirectional transmission is performed by switching the transmission direction of an optical signal over time. [Means for solving the problem]

[0005] The bidirectional optical amplifier of the present invention comprises: a first input / output port and a second input / output port; a first optical amplifying means for amplifying light in a first direction propagating through a first optical path connecting the first input / output port and the second input / output port; a second optical amplifying means that amplifies light in a second direction propagating through a second optical path that is an optical path connecting the first input / output port and the second input / output port and is different from the first optical path, and is further disposed in parallel with the first optical amplifying means; an optical path configuration means for configuring at least one of the first optical path and the second optical path; a pumping light supplying means for supplying pumping light to either the first optical amplifying means or the second optical amplifying means; Equipped with.

[0006] The bidirectional optical amplification method of the present invention comprises the steps of: A first optical amplifying means and a second optical amplifying means are arranged in parallel, amplifying light in a first direction propagating through a first optical path connecting a first input / output port and a second input / output port by the first optical amplifier; amplifying, by the second optical amplifier, light in a second direction propagating along a second optical path that is an optical path connecting the first input / output port and the second input / output port and is different from the first optical path; configures at least one of the first optical path and the second optical path; supplying pump light to either the first optical amplifying means or the second optical amplifying means; Bidirectional optical amplification method. Effect of the Invention

[0007] The present invention provides a bidirectional optical amplifier that consumes little power and is capable of amplifying light in both directions when bidirectional transmission is performed by switching the transmission direction of an optical signal over time. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a configuration example of a bidirectional optical amplifier according to a first embodiment; [Diagram 2] FIG. 2 is a block diagram showing a first modified example of the bidirectional optical amplifier of the first embodiment. [Diagram 3] FIG. 2 is a block diagram showing a second modified example of the bidirectional optical amplifier of the first embodiment. [Figure 4] FIG. 11 is a block diagram showing a configuration example of a bidirectional optical amplifier according to a second embodiment. [Diagram 5] FIG. 13 is a block diagram showing a modification of the bidirectional optical amplifier of the second embodiment. [Figure 6] FIG. 13 is a block diagram showing a configuration example of a bidirectional optical amplifier according to a third embodiment. [Figure 7] FIG. 13 is a block diagram showing a configuration example of a bidirectional optical amplifier according to a fourth embodiment. [Figure 8] FIG. 13 is a block diagram showing a configuration example of a bidirectional optical amplifier according to a fifth embodiment. [Figure 9] FIG. 13 is a block diagram showing a configuration example of a bidirectional optical amplifier according to a sixth embodiment. [Figure 10] FIG. 13 is a block diagram showing a modified example of a bidirectional optical amplifier according to the sixth embodiment. [Figure 11] FIG. 13 is a block diagram showing a configuration example of a bidirectional optical amplifier according to a seventh embodiment. [Figure 12] FIG. 13 is a block diagram showing a configuration example of a bidirectional optical amplifier included in a bidirectional optical amplifying device according to a seventh embodiment. [Figure 13] FIG. 13 is a block diagram showing a configuration example of a bidirectional optical amplifier according to an eighth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The embodiments of the present invention will be described below. The arrows in each drawing are provided as examples to explain the direction of signals in the embodiments, and do not limit the direction. Elements already mentioned in each drawing are given the same names and reference symbols, and duplicated descriptions in each embodiment will be omitted.

[0010] (First embodiment) 1 is a block diagram showing an example of the configuration of a bidirectional optical amplifier 100 according to a first embodiment of the present invention. The bidirectional optical amplifier 100 includes input / output ports 101 and 102, optical path configuration units 111 and 112, optical amplifiers 121 and 122, and a pumping light supply unit 131.

[0011] The input / output ports 101 and 102 are input / output interfaces between the light passing through the bidirectional optical amplifier 100 and an external optical fiber. The input / output ports 101 and 102 are connection points with a single core fiber (SCF) by, for example, an optical connector or fusion (splicing). In the following embodiments, the direction from the input / output port 101 to the input / output port 102 is described as a first direction, and the direction from the input / output port 102 to the input / output port 101 is described as a second direction. For example, light input to the input / output port 101 and output from the input / output port 102 is "first direction light", and light traveling in the opposite direction to the first direction light is "second direction light".

[0012] The optical path configuration units 111 and 112 configure at least one of a first optical path and a second optical path. That is, the optical path configuration units 111 and 112 connect the input / output ports 101 and 102 by at least one of a first optical path via an optical amplifier 121 and a second optical path via an optical amplifier 122.

[0013] The optical amplifiers 121 and 122 are optical fiber amplifiers. The optical amplifier 121 amplifies light in a first direction, and the optical amplifier 122 amplifies light in a second direction. The optical amplifiers 121 and 122 are arranged in parallel between the input / output ports 101 and 102. That is, the optical amplifier 121 amplifies light in a first direction propagating through a first optical path. Here, the first optical path connects the input / output port 101 and the input / output port 102. The optical amplifier 122 is arranged in parallel with the optical amplifier 121, and amplifies light in a second direction propagating through a second optical path that is different from the first optical path.

[0014] The pumping light supplying unit 131 includes a pumping light source including, for example, a 980 nm band laser diode. The pumping light supplying unit 131 supplies pumping light to either the optical amplifier 121 or the optical amplifier 122. The pumping light supplying unit 131 may include a first pumping light source that supplies pumping light to the optical amplifier 121 and a second pumping light source that supplies pumping light to the optical amplifier 122, and may operate only the pumping light source connected to the optical amplifier to be operated. Alternatively, the pumping light supplying unit 131 may include one pumping light source and a 1×2 optical switch that switches the output destination of the pumping light output by the pumping light source to either the optical amplifier 121 or the optical amplifier 122, and may control the optical switch so that the pumping light is supplied only to the optical amplifier to be operated.

[0015] When the first light or the second light needs to be amplified in the bidirectional optical amplifier 100, the pumping light supplying unit 131 supplies pumping light to the optical amplifier 121 or 122 so that the input light is amplified. The pumping light supplying unit 131 may supply pumping light to the optical amplifier 121 for a predefined period and supply pumping light to the optical amplifier 122 outside the period. Here, the period is a period during which the first light is input to the bidirectional optical amplifier 100. Alternatively, the pumping light supplying unit 131 may switch the optical amplifier that supplies the pumping light at a predetermined time. In this case, the time is a time when the light input to the bidirectional optical amplifier 100 is switched between the first light and the second light. The period or the time when the optical amplifier that supplies the pumping light is switched may be held as data by the pumping light supplying unit. Furthermore, the pumping light supplying unit 131 may set the period or the time according to information acquired by the pumping light supplying unit 131 from the outside. Since a general configuration for supplying pumping light generated by a pumping light source to an optical fiber amplifier is well known, a detailed description thereof will be omitted.

[0016] The above-described bidirectional optical amplifier 100 has the advantage of being able to amplify light in both directions while consuming less power when the transmission direction of an optical signal is switched over time to perform bidirectional transmission. This is because the pumping light supplying unit 131 supplies pumping light to either the optical amplifier 121 or the optical amplifier 122, thereby reducing the power of the pumping light supplied to the optical amplifier that does not require the amplification function.

[0017] (Another representation of the bidirectional optical amplifier 100) The bidirectional optical amplifier 100 of the first embodiment can also be described as follows. That is, the bidirectional optical amplifier (100) includes a first input / output port (101), a second input / output port (102), a first optical amplifying means (121), a second optical amplifying means (122), an optical path configuring means (111, 112), and a pumping light supplying means (131). Here, the reference numerals in FIG. 1 are written in parentheses.

[0018] The first optical amplifying means amplifies light in a first direction propagating through the first optical path. The first optical path is an optical path connecting the first input / output port and the second input / output port. The second optical amplifying means amplifies light in a second direction propagating through the second optical path, and is further arranged in parallel with the first optical amplifying means. The second optical path is an optical path connecting the first input / output port and the second input / output port, and is an optical path different from the first optical path. The optical path configuring means configures at least one of the first optical path and the second optical path. The pumping light supplying means supplies pumping light to either the first optical amplifying means or the second optical amplifying means.

[0019] In the bidirectional optical amplifier having such a configuration, pump light is supplied to either the first optical amplifying means or the second optical amplifying means. Therefore, the bidirectional optical amplifier 100 of the first embodiment can realize a bidirectional optical amplifier that consumes little power and can amplify light in both directions when bidirectional transmission is performed by switching the transmission direction of the optical signal over time.

[0020] (First Modification of the First Embodiment) 2 is a block diagram showing a configuration example of the bidirectional optical amplifier 100 A. The bidirectional optical amplifier 100 A is a first modified example of the bidirectional optical amplifier 100.

[0021] The bidirectional optical amplifier 100A differs from the bidirectional optical amplifier 100 in that it includes optical attenuators 141 and 142. The optical attenuator 141 reduces the power of light in the first direction input to the optical amplifier 121. The optical attenuator 142 reduces the power of light in the second direction input to the optical amplifier 122. The pumping light supplying unit 131 reduces the attenuation of the optical attenuator 141 when pumping light is supplied to the optical amplifier 121, and increases the attenuation of the optical attenuator 141 when pumping light is not supplied to the optical amplifier 121. In addition, the pumping light supplying unit 131 reduces the attenuation of the optical attenuator 142 when pumping light is supplied to the optical amplifier 122, and increases the attenuation of the optical attenuator 142 when pumping light is not supplied to the optical amplifier 122. This control can reduce adverse effects on the optical amplifier 122 caused by reflected light at the input side of the optical amplifier 121 entering the output side of the optical amplifier 122 via the optical path configuration unit 111. Moreover, adverse effects on the optical amplifier 121 caused by reflected light on the input side of the optical amplifier 122 entering the output side of the optical amplifier 121 via the optical path configuration section 112 can also be reduced.

[0022] A variable optical attenuator or an optical shutter can be used as the optical attenuators 141 and 142. The variable optical attenuator increases or decreases the amount of attenuation of the light input to the optical amplifiers 121 and 122 in response to an instruction from the pumping light supply unit 131. The optical shutter connects or blocks the optical path on the input side of the optical amplifiers 121 or 122 in response to an instruction from the pumping light supply unit 131. The variable optical attenuator and the optical shutter are one form of optical attenuation means. The power of the reflected light generated in these optical amplifiers can be reduced by the variable optical attenuator increasing the amount of attenuation or the optical shutter blocking the optical path.

[0023] (Second Modification of the First Embodiment) 3 is a block diagram showing a configuration example of a bidirectional optical amplifier 100B, which is a second modified example of the bidirectional optical amplifier 100.

[0024] The bidirectional optical amplifier 100B differs from the bidirectional optical amplifier 100 in that it includes optical monitoring units 151 and 152. The optical monitoring unit 151 monitors the light in the first direction and outputs information indicating the state of the light in the first direction to the pumping light supplying unit 131. The optical monitoring unit 152 monitors the light in the second direction and outputs information indicating the state of the light in the second direction to the pumping light supplying unit 131. The pumping light supplying unit 131 acquires this information from the optical monitoring units 151 and 152. Then, the pumping light supplying unit 131 determines to which of the optical amplifier 121 and the optical amplifier 122 the pumping light is to be supplied based on the acquired information. The optical monitoring units 151 and 152 are a form of optical monitoring means. The optical monitoring means outputs information indicating whether the light in the first direction and the light in the second direction are in a predetermined state to the pumping light supplying means.

[0025] For example, the light monitoring unit 151 outputs information indicating whether or not light in the first direction is present to the pumping light supplying unit 131. The light monitoring unit 152 outputs information indicating whether or not light in the second direction is present to the pumping light supplying unit 131. The pumping light supplying unit 131 acquires this information from the light monitoring units 151 and 152. Then, the pumping light supplying unit 131 supplies pumping light only to the optical amplifier 121 when only light in the first direction is present, and supplies pumping light only to the optical amplifier 122 when only light in the second direction is present.

[0026] In the bidirectional optical amplifier 100B having such a configuration, pump light is supplied only to the optical amplifiers in which the transmitted light exists. Therefore, even if the time when the first direction light and the second direction light are transmitted is unknown, the bidirectional optical amplifier 100B can detect the presence of the first direction light and the second direction light by itself. The bidirectional optical amplifier 100B further has the effect of controlling the supply of pump light to the optical amplifiers 121 and 122 so that the transmitted light is amplified.

[0027] The optical monitoring units 151 and 152 may include an optical coupler and a photoelectric conversion element. For example, the optical coupler included in the optical monitoring unit 151 branches the light in the first direction input to the optical amplifier 121 and inputs it to the photoelectric conversion element. The optical monitoring unit 151 monitors whether the power of the light in the first direction is equal to or greater than a predetermined threshold according to the output of the photoelectric conversion element, and outputs the monitoring result to the pumping light supplying unit 131. Similarly, the optical monitoring unit 152 monitors the power of the light in the second direction, and outputs the monitoring result to the pumping light supplying unit 131. Then, the pumping light supplying unit 131 supplies pumping light to either the optical amplifier 121 or the optical amplifier 122 so that only the light in the direction whose power first becomes equal to or greater than the threshold is amplified. Also, the pumping light supplying unit 131 may stop supplying pumping light when the power of the light in the direction in which the pumping light is supplied becomes less than a predetermined threshold.

[0028] When the powers of the first direction light and the second direction light simultaneously exceed a predetermined threshold, the operation of the pumping light supplying unit 131 may be determined according to the requirements of the system through which these lights are transmitted. For example, the pumping light supplying unit 131 may supply pumping light only to an optical amplifier that amplifies the light from which the predetermined information is first detected among the first direction light and the second direction light. Alternatively, when the optical powers of the first direction light and the second direction light are equal to or greater than a predetermined threshold at the same time, the pumping light supplying unit 131 may not supply pumping light to either of the optical amplifiers 121 and 122. When the powers of the first direction light and the second direction light simultaneously are less than the predetermined threshold, the pumping light supplying unit 131 does not supply pumping light to either of the optical amplifiers 121 and 122.

[0029] The light monitoring units 151 and 152 may determine the presence or absence of light in the first direction or light in the second direction based on information other than the power of light. For example, if the light in the first direction contains a predetermined preamble, the light monitoring unit 151 may determine that the first light is being transmitted. The preamble is, for example, a change in the power of the light in the first direction according to a specific pattern. Here, the specific pattern is added at the time of transmission or during transmission of the light in the first direction. The light monitoring unit 152 may also monitor the preamble of the light in the second direction in a similar manner.

[0030] Moreover, the configurations of the bidirectional optical amplifiers 100, 100A, and 100B described above are not mutually exclusive. For example, a configuration of a bidirectional optical amplifier including both the optical attenuators 141 and 142 and the optical monitors 151 and 152 is also permitted. Here, the optical attenuator 141 may be disposed between the input side of the optical amplifier 121 and the optical monitor 151, and the optical attenuator 142 may be disposed between the input side of the optical amplifier 122 and the optical monitor 152. With this configuration, the optical monitors 151 and 152 can monitor the light in the first direction and the light in the second direction regardless of the operating states of the optical attenuators 141 and 142.

[0031] Second embodiment 4 is a block diagram showing a configuration example of a bidirectional optical amplifier 200 according to a second embodiment of the present invention. The bidirectional optical amplifier 200 is configured by using optical circulators 113 and 114, respectively, to replace the optical path configuration units 111 and 112 of the bidirectional optical amplifier 100 described in FIG. 1. The optical circulators 113 and 114 include ports 1 to 3, and connect only the directions from port 1 to port 2, from port 2 to port 3, and from port 3 to port 1 with low loss. By using the optical circulators 113 and 114, a first optical path passing through the optical amplifier 121 and a second optical path passing through the optical amplifier 122 are configured between the input / output port 101 and the input / output port 102.

[0032] (Modification of the second embodiment) 5 is a block diagram showing a configuration example of the bidirectional optical amplifier 200A. In the bidirectional optical amplifier 200A, the optical circulator 113 and the optical circulator 114 of the bidirectional optical amplifier 100A described in FIG. 4 are replaced with the optical switch 115 and the optical switch 116, respectively. The optical switches 115 and 116 are 1×2 optical switches, and connect only between the port 1 and the port 2, or between the port 1 and the port 3 with low loss. The pumping light supply unit 131 controls the optical switches 115 and 116 so that the first optical path or the second optical path is configured. That is, by using the optical switches 115 and 116, either the first optical path passing through the optical amplifier 121 or the second optical path passing through the optical amplifier 122 is configured between the input / output port 101 and the input / output port 102.

[0033] The bidirectional optical amplifiers 200 and 200A having these configurations consume little power and can amplify light in both directions when bidirectional transmission is performed by switching the transmission direction of an optical signal over time, similar to the bidirectional optical amplifier 100. The bidirectional optical amplifiers 200 and 200A may further include the optical attenuators 141 and 142 described in FIG. 2 and the optical monitors 151 and 152 described in FIG. 3.

[0034] (Third embodiment) In the following embodiments, a case will be described in which the optical circulators 113 and 114 described in Fig. 4 are used as the optical path configuration units 111 and 112 included in the bidirectional optical amplifier 100 in Fig. 1. However, the following description of the embodiments is not intended to limit the specific configurations of the optical path configuration units 111 and 112.

[0035] Fig. 6 is a block diagram showing a configuration example of a bidirectional optical amplifier 300 according to a third embodiment of the present invention. Compared with the bidirectional optical amplifier 100 of Fig. 1, the bidirectional optical amplifier 300 includes pumping light sources 161 and 162, optical multiplexers 163 and 164, FIFOs 171 and 172, and a two-core EDF 170. The bidirectional optical amplifier 300 may also include optical filters 165 and 166. The optical filters 165 and 166 are optical filters that block ASE (Amplified Spontaneous Emission) output from the two-core EDF 170 in a first direction and a second direction, respectively.

[0036] A FIFO (Fan-In / Fan-Out) is an interface between an optical fiber having a single core (Single Core Fiber, SCF) and a multi-core fiber (Multi Core Fiber, MCF). The FIFO connects multiple SCF cores to one or multiple MCF cores for each core. In FIG. 6, the FIFO 171 connects the SCF core connected to the optical multiplexer 163 to one end of one of the two cores of the two-core EDF 170. The FIFO 171 also connects the SCF core connected to the optical filter 166 to the other end of the two cores of the two-core EDF 170. The FIFO 172 connects the SCF core connected to the optical multiplexer 164 to the other end of one of the two cores of the two-core EDF 170. Furthermore, the FIFO 172 connects the core of the SCF connected to the optical filter 165 to the other end of the other of the two cores of the two-core EDF 170 .

[0037] The two-core EDF 170 is an optical amplification medium composed of an MCF including two cores (first core and second core) in one EDF (Erbium-Doped Fiber). The pumping light source 161 is a light source that generates pumping light for pumping the first core of the two-core EDF 170, and the pumping light source 162 is a light source that generates pumping light for pumping the second core of the two-core EDF 170. The pumping light sources 161 and 162 may each include a laser diode with a wavelength of 980 nm. The pumping light sources 161 and 162 operate to supply pumping light to one of the two cores of the two-core EDF.

[0038] The optical multiplexers 163 and 164 are wavelength multiplexing devices that multiplex the pump light with the first direction light and the second direction light, respectively. The pump light generated by the pump light source 161 or 162 is coupled to the first core and the second core of the two-core EDF 170 by the optical multiplexers 163 or 164, respectively.

[0039] 6, light in a first direction travels to the input / output port 102 via the input / output port 101, the optical circulator 113, the optical multiplexer 163, the FIFO 171, the first core of the two-core EDF 170, the FIFO 172, the optical filter 165, and the optical circulator 114. Light in a second direction travels to the input / output port 101 via the input / output port 102, the optical circulator 114, the optical multiplexer 164, the FIFO 172, the second core of the two-core EDF 170, the FIFO 171, the optical filter 166, and the optical circulator 113.

[0040] The optical multiplexers 163 and 164, the FIFOs 171 and 172, and the two-core EDF 170 included in the bidirectional optical amplifier 300 function as the optical amplifiers 121 and 122 of the bidirectional optical amplifier 100 of Fig. 1 described above. The pumping light sources 161 and 162 include the function of the pumping light supplying unit 131 of the bidirectional optical amplifier 100. The procedure of the pumping light supplying unit 131 described in the first embodiment can be applied to switching the supply destination of the pumping light by the pumping light sources 161 and 162.

[0041] In the bidirectional optical amplifier 300 having such a configuration, the pumping light sources 161 and 162 generate pumping light so that the pumping light is supplied to either the first core or the second core of the two-core EDF 170. Therefore, when the bidirectional optical amplifier 300 performs bidirectional transmission by switching the transmission direction of the optical signal over time, the power consumption is small and bidirectional light amplification is possible. Furthermore, by using the two-core EDF, the bidirectional optical amplifier 300 can configure the EDFs of the optical amplifiers 121 and 122 of the bidirectional optical amplifier 100 with a single EDF. Therefore, the bidirectional optical amplifier 300 has a further effect of being miniaturized compared to the bidirectional optical amplifier 100.

[0042] (Fourth embodiment) 7 is a block diagram showing a configuration example of a bidirectional optical amplifier 400 according to a fourth embodiment of the present invention. The bidirectional optical amplifier 400 is different in that it includes an excitation light source 167 and an optical switch 168 instead of the excitation light sources 161 and 162 included in the bidirectional optical amplifier 300. The excitation light source 167 is a light source that generates a single excitation light, and the optical switch 168 outputs the excitation light generated by the excitation light source 167 to the optical multiplexer 163 or the optical multiplexer 164. When the two-core EDF 170 amplifies light in the first direction, the optical switch 168 switches the optical path of the excitation light so that the excitation light is output to the optical multiplexer 163. When the two-core EDF 170 amplifies light in the second direction, the optical switch 168 switches the optical path of the excitation light so that the excitation light is output to the optical multiplexer 164. The procedure for determining whether to switch the optical path of the excitation light by the optical switch 168 can be the same as that described in the first embodiment.

[0043] The bidirectional optical amplifier 400 having such a configuration has the effect of reducing the number of pump light sources in addition to the effect of the bidirectional optical amplifier 300.

[0044] Fifth embodiment 8 is a block diagram showing a configuration example of a bidirectional optical amplifier 500 according to a fifth embodiment of the present invention. The bidirectional optical amplifier 500 is different in that it includes a pumping light source 173 and an optical coupler 174 instead of the pumping light sources 161 and 162 and the optical multiplexers 163 and 164 included in the bidirectional optical amplifier 300. The pumping light source 173 is a light source that generates a single pumping light. The optical coupler 174 injects the pumping light generated by the pumping light source 167 into the cladding region of the two-core EDF 170. The FIFOs 171 and 172, the two-core EDF 170, and the optical coupler 174 function as the optical amplifiers 121 and 122 of the bidirectional optical amplifier 100 in FIG. 1. The pumping light source 173 functions as the pumping light supply unit 131 of the bidirectional optical amplifier 100.

[0045] In the bidirectional optical amplifier 500, only the power of the pump light for the light in the direction to be amplified needs to be supplied to the cladding region of the two-core EDF 170. Therefore, similar to the bidirectional optical amplifiers described in the first to fourth embodiments, the bidirectional optical amplifier 500 consumes little power and can amplify light in both directions when the transmission direction of the optical signal is switched over time to perform bidirectional transmission. Furthermore, the bidirectional optical amplifier 500 uses a technique called "cladding pumping" in which pump light is injected into the cladding region. In cladding pumping, a relatively inexpensive multimode laser can be used as a pumping light source, so that the cost of the bidirectional optical amplifier 500 can be reduced.

[0046] Sixth embodiment In the following embodiment, a bidirectional optical amplifier applicable to an optical transmission system using an MCF as an optical transmission line (hereinafter, referred to as an "MCF transmission system") will be described. When performing long-distance transmission using an MCF, crosstalk of optical signals may occur between adjacent cores. The crosstalk occurring between the cores of an MCF is relatively large between cores in which optical signals propagate in the same direction. It is also known that the crosstalk between cores in which optical signals propagate in opposite directions is smaller than the crosstalk between cores in which optical signals propagate in the same direction. Therefore, in order to reduce the crosstalk between cores in which optical signals propagate in the same direction, in an MCF transmission system performing bidirectional transmission, the directions of optical signals may be made opposite to each other between adjacent cores, and the directions of the optical signals may be reversed for a predetermined period or time. In this way, by making the transmission directions of optical signals opposite between adjacent cores in an MCF, bidirectional transmission can be realized while suppressing crosstalk.

[0047] In such an MCF transmission system that performs bidirectional transmission by time division for each core, the direction of an optical signal propagating through one core at a given time is only one direction. Therefore, an optical fiber amplifier that amplifies an optical signal propagating through the core does not need to have a function to amplify optical signals in both directions at the same time, but only needs to have an amplification function for the direction of the optical signal propagating through the core at that time. The bidirectional optical amplifiers exemplified in Figs. 1 to 8 in the first to fifth embodiments can be applied to such an MCF transmission system.

[0048] 9 is a block diagram showing a configuration example of a bidirectional optical amplifier 600 according to a sixth embodiment of the present invention. The bidirectional optical amplifier 600 includes two bidirectional optical amplifiers 601 and 602, MCFs 611 and 612, and FIFOs 613 and 614. The bidirectional optical amplifiers 601 and 602 are arranged in parallel between the FIFOs 613 and 614.

[0049] Both MCFs 611 and 612 are MCFs with two cores. Light transmitted through each core of MCF 611 is transmitted bidirectionally in a time-division manner and in opposite directions. Similarly, light transmitted through each core of MCF 612 is transmitted bidirectionally in a time-division manner and in opposite directions. FIFOs 613 and 614 are FIFOs capable of connecting a two-core MCF and two SCFs. FIFO 613 connects two cores (core 1 and core 2) of MCF 611 to one ends of bidirectional optical amplifiers 601 and 602, respectively. FIFO 614 connects two cores (core 1 and core 2) of MCF 612 to the SCFs at the other ends of bidirectional optical amplifiers 601 and 602, respectively.

[0050] The bidirectional optical amplifiers 601 and 602 each have the configuration of any one of the bidirectional optical amplifiers described in Figures 1 to 8. Therefore, a description of the configuration of the bidirectional optical amplifiers 601 and 602 will be omitted. The SCF side of the FIFO 613 is connected to the input / output port 101 of the SCF provided in each of the bidirectional optical amplifiers 601 and 602, and the SCF side of the FIFO 614 is connected to the input / output port 102 of the SCF provided in each of the bidirectional optical amplifiers 601 and 602.

[0051] The bidirectional optical amplifiers 601 and 602 included in the bidirectional optical amplifier 600 provide the effects of the bidirectional optical amplifiers described in the embodiments of Figs. 1 to 8, so the bidirectional optical amplifier 600 can also enjoy the effects of these optical amplifiers. Furthermore, the bidirectional optical amplifier 600 can amplify the light propagating through each core in an MCF transmission system with low power consumption while suppressing crosstalk between the cores. This is because, in each of the MCFs 611 and 612, the light transmitted through the two cores is bidirectionally transmitted in a time-division manner and in opposite directions to each other, and pump light is supplied to the optical amplifiers only when the light is transmitted.

[0052] (Modification of the sixth embodiment) 10 is a block diagram showing a configuration example of a bidirectional optical amplifier 600 A. The bidirectional optical amplifier 600 A is a modified example of the bidirectional optical amplifier 600 described in FIG.

[0053] The bidirectional optical amplifying device 600 includes N bidirectional optical amplifiers 601-60N, MCFs 611A and 612A, and FIFOs 613A and 614A. The bidirectional optical amplifiers 601-60N are arranged in parallel between the FIFOs 613A and 614A, where N is an integer equal to or greater than 2. The bidirectional optical amplifying device 600A is obtained by expanding the number of parallel bidirectional optical amplifiers 601 and 602 included in the bidirectional optical amplifying device 600 from 2 to N.

[0054] The MCFs 611A and 612A are both N-core MCFs having N cores, and the FIFOs 613A and 614A are FIFOs capable of connecting the N-core MCFs and N SCFs. The FIFO 613A connects the N cores (core 1 to core N) of the MCF 611A to the SCFs at one end of the bidirectional optical amplifiers 601-60N. The FIFO 614A connects the N cores (core 1 to core N) of the MCF 612A to the SCFs at the other end of the bidirectional optical amplifiers 601-60N. Each of the bidirectional optical amplifiers 601-60N has any of the configurations of the bidirectional optical amplifiers described in the first to fifth embodiments. With this configuration, the core 1 of the MCF 611A is connected to the core 1 of the MCF 612A via the bidirectional optical amplifier 601. Similarly, cores 2 to N of the MCF 611A are connected to cores 2 to N of the MCF 612A via bidirectional optical amplifiers 602 to 60N, respectively.

[0055] The bidirectional optical amplifier 600A having such a configuration can independently amplify the light propagating through each core in an MCF transmission system using an N-core MCF. The bidirectional optical amplifiers 601-60N included in the bidirectional optical amplifier 600A provide the respective effects of the bidirectional optical amplifiers described in the first to fifth embodiments. Therefore, the bidirectional optical amplifier 600A can also enjoy the effects of these optical amplifiers, just like the bidirectional optical amplifier 600.

[0056] Seventh embodiment 11 is a block diagram showing a configuration example of a bidirectional optical amplifier 700 according to a seventh embodiment of the present invention. The bidirectional optical amplifier 700 includes a bidirectional optical amplifier 701, MCFs 711 and 712, and FIFOs 713 and 714. The bidirectional optical amplifier 701 is arranged in parallel between the FIFOs 713 and 714. The bidirectional optical amplifier 701 will be described later.

[0057] The light transmitted through each core of the MCF 711 is transmitted bidirectionally in a time-division manner and in opposite directions. Similarly, the light transmitted through each core of the MCF 712 is transmitted bidirectionally in a time-division manner and in opposite directions. The FIFOs 713 and 714 are FIFOs that can connect a two-core MCF and two SCFs. The FIFO 713 connects the two cores (core 1 and core 2) of the MCF 711 to one end of the bidirectional optical amplifier 701. The FIFO 714 connects the two cores (core 1 and core 2) of the MCF 712 to the other end of the bidirectional optical amplifier 701.

[0058] 12 is a block diagram showing a configuration example of the bidirectional optical amplifier 701. The bidirectional optical amplifier 701 amplifies light propagating between the core 1 of the MCF 711 and the core 1 of the MCF 712, and light propagating between the core 2 of the MCF 711 and the core 2 of the MCF 712.

[0059] The core 1 and the core 2 of the MCF 711 are connected to the input / output ports 771 and 773, respectively, via the FIFO 713. The core 1 and the core 2 of the MCF 712 are connected to the input / output ports 772 and 774, respectively, via the FIFO 714. The optical circulators 721 and 723 and the FIFO 731 are connected so as to guide each of the two first-direction lights (i.e., lights traveling from left to right in FIG. 12) traveling from the FIFO 713 to the FIFO 714 to different cores of the two-core EDF 761. The optical coupler 743 injects the pumping light generated by the pumping light source 741 into the cladding region of the two-core EDF 761. This amplifies the first-direction light. The optical circulators 722 and 724 and the FIFO 732 are connected so as to output the two first-direction lights amplified in the respective cores of the two-core EDF 761 to the FIFO 714.

[0060] The optical circulators 722 and 724 and the FIFO 734 are connected so as to guide each of the two second-direction light beams traveling from the FIFO 714 to the FIFO 713 to each core of the two-core EDF 762. The optical coupler 744 injects the pumping light generated by the pumping light source 742 into the cladding region of the two-core EDF 762. This amplifies the second-direction light beam. The optical circulators 721 and 723 and the FIFO 733 are connected so that the two second-direction light beams amplified in each core of the two-core EDF 762 are output to the FIFO 713. The optical filters 751-754 are wavelength filters that remove ASE generated in the two-core EDFs 761 and 762, and are provided as necessary.

[0061] The input / output ports 771 and 773 function as the input / output port 101 of the bidirectional optical amplifier 100 of Fig. 1. The input / output ports 772 and 774 function as the input / output port 102 of the bidirectional optical amplifier 100. The FIFOs 731-734, the 2-core EDFs 761 and 762, and the optical couplers 743 and 744 function as the optical amplifiers 121 and 122 of the bidirectional optical amplifier 100. The pumping light sources 741 and 742 function as the pumping light supply unit 131 of the bidirectional optical amplifier 100. That is, the pumping light sources 741 and 742 supply pumping light to either one of the 2-core EDFs 761 and 762. This makes it possible to reduce the power of the pumping light supplied to the 2-core EDF in the direction in which light is not input.

[0062] Referring to FIG. 12, the two-core EDF 761 amplifies only the light in the first direction, and the two-core EDF 762 amplifies only the light in the second direction. Pumping light is injected from the input side of the light to be amplified in the two-core EDFs 761 and 762. That is, both the two-core EDFs 761 and 762 always amplify light by forward pumping. In contrast, for example, the two-core EDF 170 illustrated in FIG. 8 uses forward pumping for light in the first direction from FIFO171 to FIFO172, and uses backward pumping for light in the second direction from FIFO172 to FIFO171. In the bidirectional optical amplifier 701, the two-core EDFs 761 and 762 always amplify light in the same direction, so that there is an effect that the difference in the amplification characteristics of the EDFs is unlikely to occur for each direction of the light to be amplified. The two-core EDFs 761 and 762 may be used in backward pumping. Generally, the length of the two-core EDF 761 and the two-core EDF 762 is sufficiently shorter than the length of the transmission line of the MCF transmission system, so that the effect of crosstalk in each of the two-core EDF 761 and the two-core EDF 762 can be ignored.

[0063] The bidirectional optical amplifier 701 and the bidirectional optical amplifier device 700 including the same have the advantage that the two-core EDFs 761 and 762 amplify light in the same pumping direction, so that the difference in amplification characteristics for each light direction is unlikely to occur. In addition, similar to the bidirectional optical amplifier 500, the bidirectional optical amplifier 701 and the bidirectional optical amplifier device 700 can be reduced in cost by cladding pumping. Also, similar to the bidirectional optical amplifier device 600, the bidirectional optical amplifier device 700 can amplify the light propagating through each core with low power consumption while suppressing crosstalk in an MCF transmission system that performs bidirectional transmission by switching the transmission direction of the optical signal for each core in time. This is because, in each of the MCFs 711 and 712, the light transmitted through the two cores is bidirectionally transmitted in a time-division manner and in opposite directions to each other, and pumping light is supplied to the optical amplifier only when the light is transmitted.

[0064] Eighth embodiment Fig. 13 is a block diagram showing a configuration example of a bidirectional optical amplifier 800 according to an eighth embodiment of the present invention. The bidirectional optical amplifier 800 has a function in which N bidirectional optical amplifiers 300 described in Fig. 6 are arranged in parallel. N is an integer equal to or greater than 2. That is, the FIFO 831 connects core 1 to core N of the N-core MCF 811 to N SCFs of N optical circulators 841-84N, respectively. Also, the FIFO 834 connects core 1 to core N of the N-core MCF 812 to N SCFs of N optical circulators 851-85N, respectively.

[0065] The 2N-core EDF 820 is a multi-core fiber EDF having 2N cores. The 2N-core EDF 820 has the same function as N parallel connections of the 2-core EDF 170 of the bidirectional optical amplifier 300. The FIFO 832 connects the 2N cores connected to the optical circulators 841-84N by the SCFs to one end of each of the cores of the 2N-core EDF 820. The FIFO 833 connects the 2N cores connected to the optical circulators 851-85N by the SCFs to the other end of each of the cores of the 2N-core EDF 820.

[0066] That is, core 1 of the N-core MCF 811 is connected to core 1 of the N-core MCF 812 via optical circulator 841, the first core of the 2N-core EDF, and optical circulator 851. Cores 2 to N of the N-core MCF 811 are similarly connected to cores 2 to N of the N-core MCF 812 via optical circulators 842-84N, the second to Nth cores of the 2N-core EDF, and optical circulators 852-85N, respectively.

[0067] The basic configuration and operation of the bidirectional optical amplifier using an optical circulator and a multi-core EDF are similar to those of the bidirectional optical amplifier 300, so detailed description of the bidirectional optical amplifying device 800 will be omitted. In addition, in order to pump the 2N-core EDF 820, N sets of configurations similar to the pumping light source 161 and optical multiplexer 163 of the bidirectional optical amplifier 300 are provided between the optical circulators 841-84N and the FIFO 832 in the first direction. In addition, N sets of configurations similar to the pumping light source 162 and optical multiplexer 164 are provided between the optical circulators 851-85N and the FIFO 833 in the second direction. However, in FIG. 13, the pumping light sources and optical multiplexers are omitted.

[0068] The bidirectional optical amplifier 800 configured in this manner has a configuration in which N bidirectional optical amplifiers 300 are arranged in parallel. Therefore, the bidirectional optical amplifier 800 can enjoy the effects of the bidirectional optical amplifier 300. The bidirectional optical amplifier 800 is connected to N-core MCFs 811 and 812, and can amplify light transmitted by an MCF transmission system using the N-core MCF. Furthermore, by using the 2N-core EDF 820, the EDF can be made smaller in size compared to a configuration in which N 2-core EDFs are arranged in parallel.

[0069] The embodiments of the present invention can be described as follows, but are not limited to these.

[0070] (Appendix 1) a first input / output port and a second input / output port; a first optical amplifying means for amplifying light in a first direction propagating through a first optical path connecting the first input / output port and the second input / output port; a second optical amplifying means that amplifies light in a second direction propagating through a second optical path that is an optical path connecting the first input / output port and the second input / output port and is different from the first optical path, and is further disposed in parallel with the first optical amplifying means; an optical path configuration means for configuring at least one of the first optical path and the second optical path; a pumping light supplying means for supplying pumping light to either the first optical amplifying means or the second optical amplifying means; A bidirectional optical amplifier comprising:

[0071] (Appendix 2) The optical path configuration means includes: a first optical circulator that outputs the first direction light input to the first input / output port to the first optical amplifying means and outputs the second direction light output from the second optical amplifying means to the first input / output port; a second optical circulator that outputs the second direction light input to the second input / output port to the second optical amplifying means and outputs the first direction light output from the first optical amplifying means to the second input / output port; 2. A bidirectional optical amplifier according to claim 1, comprising:

[0072] (Appendix 3) The optical path configuration means includes: a first optical switch that outputs the first direction light input to the first input / output port to the first optical amplifying means, or outputs the second direction light output from the second optical amplifying means to the first input / output port; a second optical switch that outputs the second direction light input to the second input / output port to the second optical amplifying means, or outputs the first direction light output from the first optical amplifying means to the second input / output port; 2. A bidirectional optical amplifier according to claim 1, comprising:

[0073] (Appendix 4) 4. A bidirectional optical amplifier according to claim 1, wherein the pumping light supplying means supplies the pumping light generated by a single pumping light source to either the first optical amplifying means or the second optical amplifying means.

[0074] (Appendix 5) 5. The bidirectional optical amplifier according to claim 1, wherein the first optical amplifying means and the second optical amplifying means each include an optical attenuator that reduces a power of the input light in the first direction and a power of the input light in the second direction, respectively, when the pump light is not supplied.

[0075] (Appendix 6) a light monitoring means for outputting information indicating whether the first direction light and the second direction light are in a predetermined state to the pumping light supplying means, The pumping light supply means includes: supplying the pumping light only to the first optical amplifying means when only the light in the first direction is in the predetermined state; supplying the pumping light only to the second optical amplifying means when only the light in the second direction is in the predetermined state; 6. A bidirectional optical amplifier according to any one of claims 1 to 5.

[0076] (Appendix 7) a first FIFO; a second FIFO; and A multi-core EDF including a first core and a second core, the first optical amplifying means and the second optical amplifying means respectively use the first core and the second core of the multi-core EDF as an optical amplifying medium; One end and the other end of the multi-core EDF are connected to the optical path configuration means via the first FIFO and the second FIFO, respectively. 7. A bidirectional optical amplifier according to any one of claims 1 to 6.

[0077] (Appendix 8) 8. A bidirectional optical amplifier according to claim 7, wherein the pumping light supplying means supplies the pumping light to a cladding of the multi-core EDF.

[0078] (Appendix 9) A multi-core EDF with 2N cores, N sets of optical amplifiers according to appendix 7 or 8, N is an integer equal to or greater than 2, The first FIFO and the second FIFO are arranged such that the multi-core EDF having the 2N cores functions as the first and second optical amplifying means of each of the N optical amplifiers. Bidirectional optical amplifier.

[0079] (Appendix 10) A third FIFO, a fourth FIFO, N bidirectional optical amplifiers according to any one of claims 1 to 8, N is an integer equal to or greater than 2, the N bidirectional optical amplifiers are arranged in parallel between one end of the third FIFO and one end of the fourth FIFO; the other end of the third FIFO and the other end of the fourth FIFO are connected to a first multi-core fiber and a second multi-core fiber, respectively; Bidirectional optical amplifier.

[0080] (Appendix 11) the first optical amplifying means comprises a third FIFO, a fourth FIFO and a first two-core EDF; the second optical amplifying means comprises a fifth FIFO, a sixth FIFO and a second two-core EDF; one end and the other end of the first two-core EDF are connected to the third FIFO and the fourth FIFO, respectively; one end and the other end of the second two-core EDF are connected to the fifth FIFO and the sixth FIFO, respectively; the third and fourth FIFOs are arranged to configure the first optical path; The fifth and sixth FIFOs are arranged to configure the second optical path. 7. A bidirectional optical amplifier according to any one of claims 1 to 6.

[0081] (Appendix 12) A first optical amplifying means and a second optical amplifying means are arranged in parallel, amplifying light in a first direction propagating through a first optical path connecting a first input / output port and a second input / output port by the first optical amplifier; amplifying, by the second optical amplifier, light in a second direction propagating through a second optical path that is an optical path connecting the first input / output port and the second input / output port and is different from the first optical path; configures at least one of the first optical path and the second optical path; supplying pump light to either the first optical amplifying means or the second optical amplifying means; Bidirectional optical amplification method.

[0082] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above-mentioned embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0083] For example, the function of the pumping light supplying unit 131 may be programmed. The bidirectional optical amplifier of each embodiment may realize some or all of the functions of the pumping light supplying unit 131 by executing the program by a computer. The computer is, for example, a logic device, a central processing unit, or a digital signal processing device. The program may also be recorded on a computer-readable, fixed, non-transitory recording medium. The recording medium is, for example, a flexible disk, a fixed magnetic disk, or a non-volatile semiconductor memory. The program may also be distributed via a network.

[0084] Furthermore, the configurations described in the respective embodiments are not necessarily mutually exclusive. The actions and effects of the present invention may be achieved by a configuration that combines all or part of the above-described embodiments. [Explanation of symbols]

[0085] 100, 100A, 100B Bidirectional Optical Amplifier 101, 102 Input / Output Ports 111, 112 Optical path configuration section 113, 114 Optical circulator 115, 116, 168 Optical switches 121, 122 Optical amplifier 131 Excitation light supply unit 141, 142 Light attenuating section 151, 152 Optical monitoring section 161, 162, 167 Excitation light source 163, 164 Optical multiplexer 165, 166 Optical filters 171, 172 FIFO 173 Excitation Light Source 174 Optical Coupler 200, 200A, 300, 400, 500 Bidirectional Optical Amplifier 600, 600A Bidirectional Optical Amplifier 601-60N Bidirectional Optical Amplifier 611, 611A, 612, 612A MCF 613, 614, 613A, 614A FIFO 700 Bidirectional Optical Amplifier 701 Bidirectional Optical Amplifier 711, 712 MCF 721-724 Optical Circulator 731-734 FIFO 741, 742 Excitation light source 743, 744 Optical Coupler 751-754 Optical Filter 761, 762 2-core EDF 771-774 I / O ports 800 Bidirectional Optical Amplifier 811, 812 N-core MCF 831-834 FIFO 841-84N, 851-85N Optical Circulator

Claims

1. a first input / output port, a second input / output port, first optical amplification means for amplifying light in a first direction propagating through a first optical path connecting the first input / output port and the second input / output port; second optical amplification means for amplifying light in a second direction propagating through a second optical path that is an optical path connecting the first input / output port and the second input / output port and is different from the first optical path, and further arranged in parallel with the first optical amplification means; optical path configuration means for constituting at least one of the first optical path and the second optical path; excitation light supply means for supplying excitation light to either the first optical amplification means or the second optical amplification means; optical monitoring means for monitoring the power of the light in the first direction and the power of the light in the second direction; comprising the excitation light supply means supplies the excitation light to only one of the first optical amplification means and the second optical amplification means such that only the light in the direction in which the power first becomes equal to or greater than a threshold value among the power of the light in the first direction and the power of the light in the second direction is amplified; a bidirectional optical amplifier.

2. the optical path configuration means a first optical circulator that outputs the light in the first direction input to the first input / output port to the first optical amplification means and outputs the light in the second direction output from the second optical amplification means to the first input / output port; a second optical circulator that outputs the light in the second direction input to the second input / output port to the second optical amplification means and outputs the light in the first direction output from the first optical amplification means to the second input / output port; The bidirectional optical amplifier according to claim 1, comprising.

3. the optical path configuration means a first optical switch that outputs the light in the first direction input to the first input / output port to the first optical amplification means or outputs the light in the second direction output from the second optical amplification means to the first input / output port; a second optical switch that outputs the light in the second direction input to the second input / output port to the second optical amplification means or outputs the light in the first direction output from the first optical amplification means to the second input / output port; The bidirectional optical amplifier according to claim 1, comprising.

4. The excitation light supply means supplies the excitation light generated by a single excitation light source to either the first optical amplification means or the second optical amplification means, the bidirectional optical amplifier according to any one of claims 1 to 3.

5. The first optical amplification means and the second optical amplification means each include optical attenuation means for reducing the power of the light in the first direction input thereto and the power of the light in the second direction input thereto, respectively, when the excitation light is not supplied, the bidirectional optical amplifier according to any one of claims 1 to 4.

6. A first FIFO, A second FIFO, A multi-core EDF including a first core and a second core, The first optical amplification means and the second optical amplification means each use the first core and the second core of the multi-core EDF as an optical amplification medium, One end and the other end of the multi-core EDF are each connected to the optical path configuration means via the first FIFO and the second FIFO, The bidirectional optical amplifier according to any one of claims 1 to 5.

7. The excitation light supply means supplies the excitation light to the cladding of the multi-core EDF, the bidirectional optical amplifier according to claim 6.

8. A multi-core EDF including 2N cores, N sets of optical amplifiers according to claim 6 or 7, N is an integer of 2 or more, The first FIFO and the second FIFO are arranged such that the multi-core EDF including the 2N cores functions as the first and second optical amplification means of each of the N sets of optical amplifiers, Bidirectional optical amplification device.

9. The first optical amplification means and the second optical amplification means are arranged in parallel, Amplify the light in the first direction propagating through a first optical path connecting the first input / output port and the second input / output port by the first optical amplification means, Amplify the light in the second direction propagating through a second optical path that is an optical path connecting the first input / output port and the second input / output port and is different from the first optical path by the second optical amplification means, Constitute at least one of the first optical path and the second optical path, Supply excitation light to either the first optical amplification means or the second optical amplification means, Of the power of the light in the first direction and the power of the light in the second direction, only the light in the direction in which the power first becomes equal to or greater than the threshold value is amplified, and the excitation light is supplied only to either one of the first optical amplification means and the second optical amplification means. Bidirectional optical amplification method.

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