Optical transmission control method, optical transmission control device, and optical transmission system

Abstract

An APN-G (110) is provided with: an optical signal transmission / reception unit (112) for transmitting and receiving an optical signal; an optical signal ADD / DROP function unit (113) for adding or extracting an optical signal of a specific wavelength to or from the optical signal received by the optical signal transmission / reception unit (112); a first turnback function unit (116) for folding back the optical signal processed by the optical signal ADD / DROP function unit (113) to the optical signal ADD / DROP function unit (113) and having the optical signal transmitted from the optical signal transmission / reception unit (112); an optical signal transmission / reception unit (115) for transmitting / receiving an optical signal; an optical signal multiplexing / demultiplexing function unit (114) for performing multiplexing or demultiplexing on the optical signal received by the optical signal transmission / reception unit (115); and a second turnback function unit (117) for turning back the optical signal processed by the optical signal multiplexing / demultiplexing function unit (114) to the optical signal multiplexing / demultiplexing function unit (114) and having the optical signal transmitted from the optical signal transmission / reception unit (115).

Description

Optical transmission device, optical transmission control device, and optical transmission system

[0001] The present disclosure relates to an optical transmission device, an optical transmission control device, and an optical transmission system.

[0002] Conventional optical transmission equipment for optical transport networks has been vertically integrated by a single vendor due to competition in transmission performance. However, in recent years, there has been a push toward open and disaggregated optical transmission equipment.

[0003] The IOWN (Innovative Optical and Wireless Network) Global Forum is an international organization working to realize the network concept proposed by Nippon Telegraph and Telephone Corporation. It is currently discussing the realization of a network and information processing infrastructure that includes terminals capable of providing high-speed, large-capacity communications and vast computing resources using innovative optical technologies.

[0004] One of the technologies to realize this IOWN is the All Photonics Network (APN) or Open-APN, which will enable end-to-end communication to be carried out entirely optically, without the use of electricity, thereby providing high-capacity, power-efficient, and low-latency transmission.

[0005] The IOWN Global Forum is working to redefine the functions of conventional core-metro equipment in order to realize Open-APN. Non-Patent Document 1, a technical document as of March 2023, describes the following definitions and compares functions with conventional optical transmission equipment.

[0006] APN-T is defined as an APN originating or terminating device, and corresponds to a transponder in comparison with conventional devices. Conventionally, transponders were mainly installed in the same optical transmission equipment as OXCs (Optical Cross Connects) or ROADMs (Reconfigurable Optical Add-Drop Multiplexers). However, there are use cases where APN-T is extracted as a device and installed on the user station side.

[0007] APN-G is defined as a device that acts as an optical gateway accommodating APN-T, and has Add, Drop, Mux, and Demux functions. It is equivalent to the conventional device (ROADM / OXC) without the WXC function, but newly defined are the functions of communicating with and controlling APN-T installed in user stations, and the turnback function of sending signals from APN-T to another APN-T connected to the same APN-G.

[0008] APN-I is defined as an interchange that connects APNs at the midpoint of the optical path of Open-APN. It is equivalent to a WXC that removes the OADM function from conventional equipment (ROADM or OXC). It is also defined as having a wavelength conversion function.

[0009] The APN-C is defined as a controller that controls and manages the above-mentioned APN-T to APN-I, and corresponds to the controller of the conventional device.

[0010] In conventional networks, the soundness of optical signals has been confirmed by monitoring the power of the optical signals or by monitoring the path normality using an OCS.

[0011] IOWN Global Forum, 'Open All-Phononic Network Functional Architecture', version 1.0, January 27, 2022

[0012] However, in recent years, optical signals have become increasingly multi-valued, and distortion occurring in the transmission path has a significant impact on performance. In addition, open systems have resulted in the mixing of equipment from many vendors between transmitters, transmission paths, and receivers, making it difficult to identify the cause of communication failures at the receiving end.

[0013] Therefore, one or more aspects of the present disclosure aim to make it possible to easily find a location where an optical signal becomes abnormal.

[0014] An optical transmission device according to one aspect of the present disclosure is characterized by comprising: a first optical signal transceiver that transmits and receives optical signals; an optical signal add / drop functional unit that adds or drops an optical signal of a specific wavelength to or from an optical signal received by the first optical signal transceiver; a first turn-back functional unit that returns the optical signal processed by the optical signal add / drop functional unit to the optical signal add / drop functional unit and transmits it from the first optical signal transceiver; a second optical signal transceiver that transmits and receives optical signals; an optical signal multiplexing / demultiplexing functional unit that multiplexes or demultiplexes the optical signal received by the second optical signal transceiver; and a second turn-back functional unit that returns the optical signal processed by the optical signal multiplexing / demultiplexing functional unit to the optical signal multiplexing / demultiplexing functional unit and transmits it from the second optical signal transceiver.

[0015] An optical transmission device according to one aspect of the present disclosure is characterized by comprising: a first optical signal transceiver that transmits and receives optical signals; a second optical signal transceiver that transmits and receives optical signals; an optical signal cross-connect function unit that switches optical signals received by the first optical signal transceiver and the second optical signal transceiver; and a turn-back function unit that turns an optical signal received by the first optical signal transceiver and processed by the optical signal cross-connect function unit back to the optical signal cross-connect function unit to transmit it from the first optical signal transceiver, and turns an optical signal received by the second optical signal transceiver and processed by the optical signal cross-connect function unit back to the optical signal cross-connect function unit to transmit it from the second optical signal transceiver.

[0016] An optical transmission control device according to one aspect of the present disclosure is an optical transmission control device that controls an optical path including a first optical terminal device, one or more first optical transmission devices having an ADD / DROP function for adding or dropping an optical signal of a specific wavelength to or from an optical signal and a multiplexing / demultiplexing function for multiplexing or demultiplexing an optical signal, one or more second optical transmission devices having a cross-connect function for switching an optical signal, and a second optical transmission terminal device, and a control unit that, when an optical signal transmitted from the first optical transmission terminal device cannot be restored by the second optical transmission terminal device, selects one device in turn from the one or more first optical transmission devices and the one or more second optical transmission devices via the communication unit, returns the optical signal toward the first optical transmission terminal device, and compares the bit error rate of the returned optical signal when it is received by the first optical transmission terminal device to identify a suspected cause of the inability to restore the optical signal.

[0017] An optical transmission system according to an aspect of the present disclosure is an optical transmission system including a first optical transmission terminal device, one or more first optical transmission devices, one or more second optical transmission devices, an optical path including the second optical transmission terminal device, and an optical transmission control device that controls the optical path, wherein each of the one or more first optical transmission devices includes a first optical signal transceiver that transmits and receives an optical signal, an optical signal ADD / DROP function unit that adds or drops an optical signal of a specific wavelength to or from an optical signal received by the first optical signal transceiver, and an optical signal ADD / DROP function unit that adds or drops an optical signal of a specific wavelength to or from an optical signal processed by the optical signal ADD / DROP function unit. a first turn-back function unit that turns back the optical signal to the ADD / DROP function unit and causes it to be transmitted from the first optical signal transmitting and receiving unit; a second optical signal transmitting and receiving unit that transmits and receives an optical signal; an optical signal multiplexing and demultiplexing function unit that performs multiplexing or demultiplexing on the optical signal received by the second optical signal transmitting and receiving unit; a second turn-back function unit that turns back the optical signal processed by the optical signal multiplexing and demultiplexing function unit to the optical signal multiplexing and demultiplexing function unit and causes it to be transmitted from the second optical signal transmitting and receiving unit; and a first communication unit that communicates via a network, an optical signal cross-connect function unit that switches optical signals received by the third optical signal transceiver unit and the fourth optical signal transceiver unit; an optical signal cross-connect function unit that switches optical signals received by the third optical signal transceiver unit and processed by the optical signal cross-connect function unit, returning the optical signal received by the third optical signal transceiver unit and processed by the optical signal cross-connect function unit to the optical signal cross-connect function unit and transmitting the optical signal from the third optical signal transceiver unit; and a second communication unit that communicates via the network, wherein the optical transmission control device has a third communication unit that communicates via the network with the first optical transmission terminal device, the one or more first optical transmission devices, the one or more second optical transmission devices, and the second optical transmission terminal device, and when an optical signal transmitted from the first optical transmission terminal device cannot be restored by the second optical transmission terminal device, selects one device in turn from the one or more first optical transmission devices and the one or more second optical transmission devices via the third communication unit,and a control unit that loops back the optical signal in the direction of the first optical terminal device and compares the bit error rate when the looped back optical signal is received by the first optical terminal device, thereby identifying a suspected location that is the cause of the inability to restore the optical signal.

[0018] According to one or more aspects of the present disclosure, it is possible to easily find a location where an optical signal becomes abnormal.

[0019] FIG. 1 is a block diagram schematically showing the configuration of an optical transmission system according to a first or second embodiment. FIG. 2 is a block diagram schematically showing the configuration of a main part of an APN-G. (A) and (B) are block diagrams showing an example of a hardware configuration. FIG. 3 is a block diagram schematically showing the configuration of a main part of an APN-I. FIG. 4 is a block diagram schematically showing the configuration of a main part of an APN-T in a first embodiment. FIG. 5 is a block diagram schematically showing the configuration of a main part of an APN-C. FIG. 6 is a block diagram schematically showing the configuration of a main part of an APN-T in a second embodiment.

[0020] 1 is a block diagram showing a schematic configuration of an optical transmission system 100 according to embodiment 1. The optical transmission system 100 includes APN-G 110A and 110B as optical transmission devices, APN-I 130A and 130B as optical transmission devices, APN-T 150A and 150B as optical transmission terminal devices, and APN-C 170 as an optical transmission control device.

[0021] The APN-Gs 110A and 110B are also referred to as first optical transmission devices, and the APN-Is 130A and 130B are also referred to as second optical transmission devices.

[0022] The APN-G 110A, 110B, the APN-I 130A, 130B, and the APN-T 150A, 150B perform optical transmission and are connected to the network 101 so as to be able to communicate with the APN-C 170.

[0023] APN-G110A and 110B are configured in the same manner, and therefore, when there is no need to distinguish between APN-G110A and 110B, they are referred to as APN-G110. APN-I130A and 130B are configured in the same manner, and therefore, when there is no need to distinguish between APN-I130A and 130B, they are referred to as APN-I130. APN-T150A and 150B are configured in the same manner, and therefore, when there is no need to distinguish between APN-T150A and 150B, they are referred to as APN-T150. Note that although two APN-G110 are provided in FIG. 1, it is sufficient that at least one APN-G110 is provided. Also, although two APN-I130 are provided in FIG. 1, it is sufficient that at least one APN-I130 is provided.

[0024] Fig. 2 is a block diagram showing a schematic configuration of the main components of the APN-G 110. Fig. 2 shows the main components of the APN-G 110 that are related to the first embodiment. As shown in Fig. 1, the APN-G 110 serves as a gateway when the APN-T 150 is the starting point or the ending point. As described above, the APN-G 110 has an Add function, a Drop function, a Mux function, and a Demux function.

[0025] The APN-G 110 includes an optical repeater unit 111, a communication unit 120, and a control unit 121. The optical repeater unit 111 includes an optical signal transmitting / receiving unit 112, an optical signal add / drop function unit 113, an optical signal multiplexing / demultiplexing function unit 114, an optical signal transmitting / receiving unit 115, a first turnback function unit 116, and a second turnback function unit 117.

[0026] The optical signal transmitting / receiving unit 112 transmits and receives optical signals to and from the APN-T 150. The optical signal transmitting / receiving unit 112 is, for example, an optical connector. The optical signal transmitting / receiving unit 112 is also referred to as a first optical signal transmitting / receiving unit. The optical signal add / drop function unit 113 has an add function and a drop function for adding and dropping optical signals of specific wavelengths to and from optical signals. The optical signal add / drop function unit 113 is, for example, an OADM (Optical Add Drop Multiplexer).

[0027] The optical signal multiplexing / demultiplexing function unit 114 has a Mux function and a Demux function for multiplexing and demultiplexing optical signals. The optical signal multiplexing / demultiplexing function unit 114 is, for example, an optical multiplexer / demultiplexer. The optical signal transmitting / receiving unit 115 transmits and receives optical signals to and from another device. As shown in FIG. 1, the other device here is the APN-I 130, but unlike in FIG. 1, it may also be another APN-G 110. The optical signal transmitting / receiving unit 115 is, for example, an optical connector. The optical signal transmitting / receiving unit 115 is also referred to as a second optical signal transmitting / receiving unit.

[0028] The first turnback function unit 116 turns back an optical signal from the APN-T 150 accommodated in the APN-G 110. Here, the first turnback function unit 116 turns back the optical signal processed by the optical signal ADD / DROP function unit 113 to the optical signal ADD / DROP function unit 113 and transmits it from the optical signal transmitting / receiving unit 112. The first turnback function unit 116 can realize the turnback function by, for example, setting some ports of a WSS (Wavelength Selective Switch) or MCS (MultiCast Switch) as ports dedicated to turnback and selecting those ports as the optical signal path.

[0029] The second turnback function unit 117 turns back an optical signal from another device, in other words, an optical signal on the transmission path side. Here, the second turnback function unit 117 turns back the optical signal processed by the optical signal multiplexing / demultiplexing function unit 114 to the optical signal multiplexing / demultiplexing function unit 114, and transmits it from the optical signal transmitting / receiving unit 115. The second turnback function unit 117 can also realize the turnback function by, for example, setting some ports of the WSS or MCS as ports dedicated to turnback and selecting those ports as the optical signal path.

[0030] The communication unit 120 communicates with the APN-C 170 via the network 101. The communication unit 120 is also referred to as a first communication unit. The control unit 121 communicates with the APN-C 170 via the communication unit 120, and controls the optical repeater unit 111 in accordance with instructions from the APN-C 170.

[0031] 3A, a part or all of the control unit 121 described above can be configured by a memory 10 and a processor 11 such as a CPU (Central Processing Unit) that executes a program stored in the memory 10. Such a program may be provided over a network or may be provided by being recorded on a recording medium. That is, such a program may be provided as a program product, for example.

[0032] 3B, a part or all of the control unit 121 may be configured by a processing circuit 12 such as a single circuit, a composite circuit, a processor operated by a program, a parallel processor operated by a program, an ASIC (Application Specific Integrated Circuit), or an FPGA (Field Programmable Gate Array). As described above, the control unit 121 may be realized by a processing circuit network. The communication unit 120 may be realized by a communication interface such as a NIC (Network Interface Card).

[0033] Fig. 4 is a block diagram showing a schematic configuration of the main components of the APN-I 130. Fig. 4 shows the main components of the APN-I 130 that are related to the first embodiment. The APN-I 130 includes an optical repeater unit 131, a communication unit 140, and a control unit 141. The optical repeater unit 131 includes an optical signal transmitting and receiving unit 132, an optical signal cross-connect function unit 133, a wavelength conversion function unit 134, an optical signal transmitting and receiving unit 135, and a turnback function unit 136.

[0034] The optical signal transmitting / receiving unit 132 transmits and receives optical signals to and from another device. The optical signal transmitting / receiving unit 132 is, for example, an optical connector. As shown in Fig. 1 , the other device here is the APN-I 130 or the APN-G 110. The optical signal transmitting / receiving unit 132 is also referred to as a first optical signal transmitting / receiving unit or a third optical signal transmitting / receiving unit.

[0035] The optical signal cross-connect function unit 133 switches the wavelength-multiplexed optical signals in units of wavelengths. The optical signal cross-connect function unit 133 is, for example, an OXC (Optical Cross Connect).

[0036] The wavelength conversion function unit 134 switches the wavelength of the optical signal between APNs. The wavelength conversion function unit 134 is a wavelength conversion device that uses a method using a nonlinear optical effect and a wavelength filter, or a method of converting an optical signal into an electrical signal and then converting the wavelength.

[0037] The optical signal transmitting / receiving unit 135 transmits and receives optical signals to and from another device. The optical signal transmitting / receiving unit 135 is, for example, an optical connector. As shown in FIG. 1 , the other device here is the APN-I 130 or the APN-G 110. The optical signal transmitting / receiving unit 135 is also referred to as a second optical signal transmitting / receiving unit or a fourth optical signal transmitting / receiving unit.

[0038] The turnback function unit 136 returns an optical signal from another device to the same one path. For example, the turnback function unit 136 returns an optical signal that has been received by the optical signal transmitting and receiving unit 132 and processed by the optical signal cross-connect function unit 133 to the optical signal cross-connect function unit 133 and causes it to be transmitted from the optical signal transmitting and receiving unit 132. The turnback function unit 136 also returns an optical signal that has been received by the optical signal transmitting and receiving unit 135 and processed by the optical signal cross-connect function unit 133 to the optical signal cross-connect function unit 133 and causes it to be transmitted from the optical signal transmitting and receiving unit 135. The turnback function unit 136 is also referred to as a third turnback function unit.

[0039] The communication unit 140 communicates with the APN-C 170 via the network 101. The communication unit 140 is also referred to as a second communication unit. The control unit 141 communicates with the APN-C 170 via the communication unit 140, and controls the optical repeater unit 131 in accordance with instructions from the APN-C 170.

[0040] 3A, a part or all of the control unit 141 described above can be configured by a memory 10 and a processor 11 such as a CPU that executes a program stored in the memory 10. Such a program may be provided over a network or may be provided by being recorded on a recording medium. That is, such a program may be provided as a program product, for example.

[0041] 3B, the control unit 141 may be partially or entirely configured by a processing circuit 12 such as a single circuit, a composite circuit, a processor operated by a program, a parallel processor operated by a program, an ASIC, or an FPGA. As described above, the control unit 141 may be realized by a processing circuit network. The communication unit 140 may be realized by a communication interface such as a NIC.

[0042] Fig. 5 is a block diagram showing a schematic configuration of the main parts of the APN-T 150 according to the first embodiment. Fig. 5 shows the main parts of the configuration of the APN-T 150 that are relevant to the first embodiment. The APN-T 150 includes an optical conversion unit 151, a communication unit 160, and a control unit 161. The optical conversion unit 151 includes a client accommodation unit 152, a digital signal processing unit 153, and an optical signal transmission / reception unit 154.

[0043] The APN-T 150 is a terminal device that serves as the start or end point of the APN, and exchanges optical signals with the APN-G 110 .

[0044] The client accommodation unit 152 connects to a user device 180, which is a terminal used by a user, via a communication unit 160.

[0045] The digital signal processing unit 153 processes digital signals exchanged with the user device 180. For example, the digital signal processing unit 153 performs error correction encoding and decoding processing, executes a function of monitoring the number of corrected bits, and performs digital signal processing based on a digital coherent transmission method.

[0046] The optical signal transmitting / receiving unit 154 transmits and receives optical signals to and from the APN-G 110. The optical signal transmitting / receiving unit 154 is, for example, an optical connector.

[0047] The communication unit 160 communicates with the APN-C 170 via the network 101. The control unit 161 communicates with the APN-C 170 via the communication unit 140, and controls the optical conversion unit 151 in accordance with instructions from the APN-C 170.

[0048] 3A, part or all of the client accommodation unit 152, digital signal processing unit 153, and control unit 161 described above can be configured by a memory 10 and a processor 11 such as a CPU that executes a program stored in the memory 10. Such a program may be provided over a network or may be provided by being recorded on a recording medium. That is, such a program may be provided as a program product, for example.

[0049] 3B, the client accommodating unit 152, the digital signal processing unit 153, and the control unit 161 may be partially or entirely configured by a processing circuit 12 such as a single circuit, a composite circuit, a processor operated by a program, a parallel processor operated by a program, an ASIC, or an FPGA. As described above, the client accommodating unit 152, the digital signal processing unit 153, and the control unit 161 may be realized by a processing circuit network. The communication unit 160 may be realized by a communication interface such as a NIC.

[0050] Fig. 6 is a block diagram showing a schematic configuration of the main components of the APN-C170. Fig. 6 shows the main components of the APN-C170 that are related to the first embodiment. For example, the APN-C170 controls an optical path that includes the APN-G110, the APN-I130, and the APN-T150. The APN-C170 includes a communication unit 171 and a control unit 172.

[0051] The communication unit 171 communicates with other devices via the network 101. The communication unit 171 is also referred to as a third communication unit. As shown in FIG. 1 , the other devices here are APN-G 110, APN-I 130, and APN-T 150.

[0052] The control unit 172 controls another device via the communication unit 171. For example, if an optical signal transmitted from the APN-T 150A as the first optical terminal device cannot be restored by the APN-T 150B as the second optical terminal device, the control unit 172 sequentially selects one device from the APN-G 110 as the first optical transmission device and the APN-I 130 as the second optical transmission device via the communication unit 171, returns the optical signal toward the APN-T 150A, and compares the bit error rate when the returned optical signal is received by the APN-T 150A to identify the suspected cause of the inability to restore the optical signal. Here, the first optical terminal device may be the APN-T 150B, and in this case, the second optical terminal device is the APN-T 150A.

[0053] 3A, a part or all of the control unit 172 described above can be configured by a memory 10 and a processor 11 such as a CPU that executes a program stored in the memory 10. Such a program may be provided over a network or may be provided by being recorded on a recording medium. That is, such a program may be provided as a program product, for example.

[0054] 3B, a part or all of the control unit 172 may be configured by a processing circuit 12 such as a single circuit, a composite circuit, a processor operated by a program, a parallel processor operated by a program, an ASIC, or an FPGA. As described above, the control unit 172 may be realized by a processing circuit network. The communication unit 171 may be realized by a communication interface such as a NIC.

[0055] Next, a description will be given of the operation of the optical transmission system 100 shown in Fig. 1. Here, it is assumed that an optical signal is transmitted from APN-T 150A as the start point to APN-T 150B as the end point.

[0056] APN-T150A is connected to APN-G110A, and is connected to APN-T150B via APN-I130A, APN-I130B, and APN-G110B. APN-T150A, APN-G110A, APN-I130A, APN-I130B, APN-G110B, and APN-T150B are connected to APN-C170 via network 101 and are controlled by APN-C170.

[0057] In the APN-C 170, the control unit 172 determines the properties of the optical signal, such as wavelength, bandwidth, and signal format, depending on the amount of data required by the user equipment 180 (see Figure 7) or the conditions of the transmission path, and controls the devices within the network 101.

[0058] Typically, in the APN-T 150A, the communication unit 160 first receives a signal from the user device 180, and the client accommodation unit 152 accommodates the signal as a client. Then, the digital signal processing unit 153 performs digital signal processing (e.g., error correction coding and modulation mapping) required for the digital coherent transmission method, and converts the signal into an optical signal. The optical signal transmitting / receiving unit 154 transmits the converted optical signal to the APN-G 110A.

[0059] In APN-G 110A, optical signal transmitting / receiving unit 112 receives the optical signal, and the optical signal passes through optical signal add / drop function unit 113 and is multiplexed in optical signal multiplexing / demultiplexing function unit 114. Then, optical signal transmitting / receiving unit 115 transmits the multiplexed optical signal to APN-I 130A.

[0060] In the APN-I 130A, the optical signal transmitting / receiving unit 132 receives the optical signal, the optical signal cross-connect function unit 133 switches the route to the APN-I 130B, and the optical signal transmitting / receiving unit 135 transmits the optical signal. Note that in the APN-I 130A, the wavelength conversion function unit 134 performs wavelength conversion as necessary.

[0061] Similarly, in APN-I 130B, the optical signal transmitting / receiving unit 132 receives the optical signal, the optical signal cross-connect function unit 133 switches the route to the APN-G 110B, and the optical signal transmitting / receiving unit 135 transmits the optical signal.

[0062] In APN-G 110B, optical signal transmitting / receiving unit 115 receives an optical signal, and optical signal multiplexing / demultiplexing function unit 114 demultiplexes the optical signal. The demultiplexed optical signal is provided from optical signal add / drop function unit 113 to optical signal transmitting / receiving unit 112, which then outputs the optical signal toward APN-T 150B.

[0063] In the APN-T 150B, the optical signal transmitting / receiving unit 154 receives the optical signal and converts the optical signal into an electrical signal, after which the digital signal processing unit 153 performs digital signal processing (e.g., signal equalization processing, demapping processing, error correction decoding processing, etc.) used in, for example, a digital coherent transmission system on the electrical signal, and then extracts the client signal. The extracted client signal is provided to the communication unit 160 via the client accommodating unit 152, and is sent to the user device 180 on the APN-T 150B side.

[0064] At this time, if the digital signal processing unit 153 of the APN-T 150B cannot restore the transmitted signal, it is necessary to analyze the cause of the problem. In such a case, for example, the control unit 161 of the APN-T 150B notifies the APN-C 170 via the communication unit 160 that the transmitted signal cannot be restored.

[0065] The control unit 172 of the APN-C 170 receives notification via the communication unit 171 that the signal cannot be restored at the APN-T 150B, and uses the optical signal multiplexing / demultiplexing function unit 114 of the APN-G 110B to turn back the optical signal for the APN-T 150B at the second turnback function unit 117, which is a turnback function unit on the transmission path side. As a result, the turned back optical signal is input to the optical signal transmitting / receiving unit 154 of the APN-T 150A.

[0066] In the APN-T 150A, the digital signal processing unit 153 receives the received optical signal, performs error correction decoding processing, and observes the BER (Bit Error Rate) before error correction using the decoding result (e.g., the number of corrected bits). The control unit 161 sends the BER observed in this way to the APN-C 170 via the communication unit 160.

[0067] The APN-C170 compares the expected value of reception performance (here, BER) that takes into account performance degradation due to transmission via the transmission paths between the APN-T150A, APN-G110B, and APN-T150A with the BER observed by the APN-T150A to evaluate the validity of the BER observed by the APN-T150A. Here, the control unit 172 may determine that the BER observed by the APN-T150A is valid if, for example, it is within a predetermined range with respect to the expected value.

[0068] If the reception performance (BER) is appropriate, the control unit 172 can identify that the suspected cause of the signal inability to be restored is between the APN-G 110B and the APN-T 150B. On the other hand, if the reception performance (BER) of the looped-back optical signal is inappropriate, the control unit 172 of the APN-C 170 enables the loop-back function at the APN-I 130B so that the signal is looped back at a position that is even shorter in distance. Here, the control unit 172 uses the optical signal cross-connect function unit 133 of the APN-I 130B to loop back the optical signal at the turnback function unit 136.

[0069] Then, as described above, the control unit 172 of the APN-C170 compares the expected value of the receiving performance (here, BER) that takes into account performance degradation due to the return transmission path with the BER before error correction calculated using the decoding result (e.g., the number of corrected bits) of the optical signal received by the APN-T150A, and evaluates the validity of the BER observed by the APN-T150A. At this time, as long as the setting allows reception by the APN-T150A, return may be performed either before or after wavelength conversion. Furthermore, a similar evaluation may be performed before and after wavelength conversion.

[0070] If the reception performance (BER) is appropriate, the control unit 172 can identify that the suspected cause of the signal not being able to be restored is between APN-I 130B and APN-G 110B. On the other hand, if the reception performance (BER) of the looped back optical signal is not appropriate, the control unit 172 of APN-C 170 enables the loopback function at APN-I 130A so that the loopback will be at a position that is even shorter in distance.

[0071] By repeating the above process until the suspected location that is the cause of the signal not being able to be restored is identified, the suspected location that is the cause of the signal not being able to be restored can be identified.

[0072] In the above example, control is performed to turn back in order starting from APN-G110B, which is closest to APN-T150B, which is the termination point, but conversely, control may be performed to turn back in order starting from APN-G110A, which is closest to APN-T150A. In other words, the order in which turnbacks are performed does not matter.

[0073] Furthermore, since the transmission distance doubles when a turnback is performed, when evaluating the identification of suspected locations, the properties of the optical signal may be changed to be lower than the data capacity required by the user device 180 in accordance with the transmission distance, such as by lowering the modulation multi-level level through control of the APN-C 170, and the evaluation may be performed.

[0074] As explained above, by sequentially folding back the transmission path and comparing the expected value of the receiving performance (here, BER) that takes into account the performance degradation due to the folded back transmission path with the BER before error correction that is calculated using the decoding result (e.g., the number of corrected bits) of the signal received by the APN-T150A, it becomes easy to identify the suspected part that is causing distortion in the optical signal sent from the APN-T150A. Furthermore, because the configuration is such that the transmission signal generated by the APN-T150A is received by the APN-T150A, it becomes possible to perform analysis that is separate from the interoperability that occurs between devices from different vendors.

[0075] Embodiment 2. In the first embodiment, the location where the transmission quality is degraded is estimated by monitoring the reception performance (BER), but there is a problem that it is difficult to estimate the cause of the degradation. In the second embodiment, such a problem is solved.

[0076] As shown in FIG. 1, the optical transmission system 200 according to the second embodiment includes APN-Gs 110A and 110B, APN-Is 130A and 130B, APN-Ts 250A and 250B, and an APN-C 270.

[0077] The APN-Gs 110A and 110B and APN-Is 130A and 130B of the optical transmission system 200 according to the second embodiment are similar to the APN-Gs 110A and 110B and APN-Is 130A and 130B of the optical transmission system 100 according to the first embodiment. In the second embodiment, the APN-Ts 250A and 250B are configured in the same manner, and therefore, when there is no need to particularly distinguish between the APN-Ts 250A and 250B, they will be referred to as APN-Ts 250.

[0078] Fig. 7 is a block diagram showing a schematic configuration of the main parts of the APN-T 250 according to the second embodiment. Fig. 7 shows the main parts of the configuration of the APN-T 250 that are relevant to the second embodiment. The APN-T 250 includes an optical conversion unit 251, a communication unit 160, and a control unit 261. The communication unit 160 of the APN-T 250 according to the second embodiment is the same as the communication unit 160 of the APN-T 250 according to the second embodiment.

[0079] The optical conversion unit 251 includes a client accommodation unit 152 , a digital signal processing unit 253 , an optical signal transmission / reception unit 154 , a data insertion unit 255 , and a data extraction unit 256 .

[0080] The client accommodation unit 152 and the optical signal transmission / reception unit 154 of the optical conversion unit 251 in the second embodiment are similar to the client accommodation unit 152 and the optical signal transmission / reception unit 154 of the optical conversion unit 151 in the first embodiment.

[0081] The digital signal processing unit 253 performs the same processing as the digital signal processing unit 153 of the first embodiment, as well as the following processing: When the digital signal processing unit 253 receives data of a known pattern for analysis from the data insertion unit 255, it provides the transmission data into which the data of the known pattern has been inserted to the optical signal transmitting / receiving unit 154, which outputs the data as an optical signal.

[0082] Furthermore, when the optical signal transmitting / receiving unit 154 receives an optical signal containing data of a known pattern, the digital signal processing unit 253 provides the data contained in the optical signal to the data extraction unit 256 .

[0083] The data insertion unit 255 provides data of a known pattern to the digital signal processing unit 253 in accordance with instructions from the APN-C 270. Here, the APN-C 270 instructs the digital signal processing unit 253 to insert a known pattern after estimating the location where transmission quality is degraded.

[0084] The data extraction unit 256 extracts data of a known pattern from the data received from the digital signal processing unit 253, and provides the extracted data to the control unit 261. The control unit 261 sends the extracted data to the APN-C 270 via the communication unit 160.

[0085] 6, the APN-C 270 in the second embodiment includes a communication unit 171 and a control unit 272. The communication unit 171 of the APN-C 270 in the second embodiment is similar to the communication unit 171 of the APN-C 170 in the first embodiment.

[0086] The control unit 272 controls another device via the communication unit 171. For example, by performing the same processing as in the first embodiment, the control unit 272 loops back the transmission path in order and compares the expected value of the reception performance (here, BER) taking into account performance degradation due to the looped back transmission path with the BER before error correction calculated using the decoding result (for example, the number of corrected bits) of the signal received by the APN-T 150A, thereby identifying a suspected portion that makes it impossible to decode the optical signal sent from the APN-T 150A.

[0087] After identifying the suspected location, the control unit 272 determines the cause of the degradation of the optical signal at the suspected location by comparing a first evaluation value obtained when the APN-T150A receives an optical signal of a known pattern that has been transmitted from the first optical transmission terminal device, APN-T150A, and returned along a first optical path that includes the suspected location, with a second evaluation value obtained when the APN-T150A receives an optical signal that has been transmitted from APN-T150A and returned along a second optical path that does not include the suspected location.

[0088] For example, the first evaluation value and the second evaluation value may be signal-to-noise ratios calculated using a known pattern. In this case, if the difference between the first evaluation value and the second evaluation value is greater than a threshold, the control unit 272 can determine that the cause of the degradation of the optical signal at the suspected location is an optical amplifier.

[0089] The first evaluation value and the second evaluation value may be frequency characteristics obtained by frequency analysis of a known pattern. In this case, if the difference between the first evaluation value and the second evaluation value is greater than a threshold, the control unit 272 can determine that the cause of the degradation of the optical signal at the suspected location is the optical filter.

[0090] Specifically, after identifying the suspected location, the control unit 272 loops back the transmission path so that the suspected location is included, and instructs the APN-T 250, which is the data transmission source, to transmit data of a known pattern via the communication unit 171. Thereafter, the control unit 272 receives the extracted data from the APN-T 250 that transmitted the data of the known pattern via the communication unit 171, calculates the SNR (Signal-to-Noise Ratio) characteristics by comparing the transmitted known pattern with the extracted known pattern, and calculates the frequency characteristics by frequency analysis of the extracted known pattern.

[0091] Furthermore, the control unit 272 loops back the transmission path just before the suspected location and instructs the APN-T 250, which is the data transmission source, to transmit data of the known pattern via the communication unit 171. Then, similar to the above, the control unit 272 receives the extracted data from the APN-T 250 that transmitted the data of the known pattern via the communication unit 171, calculates the SNR characteristics by comparing the transmitted known pattern with the extracted known pattern, and calculates the frequency characteristics by frequency analysis of the extracted known pattern.

[0092] From the above, the control unit 272 can compare the values ​​calculated before and after the suspected point that degrades transmission quality and analyze, for example, that if the SNR characteristics are significantly degraded, the influence of the optical amplifier in the transmission path is large, and if the frequency characteristics are significantly degraded, the influence of the band narrowing due to the optical filter is large.

[0093] As described above, according to the second embodiment, it is possible to analyze the factors that cause the degradation of transmission quality.

[0094] 100, 200 Optical transmission system, 110 APN-G, 111 Optical repeater unit, 112 Optical signal transmitting and receiving unit, 113 Optical signal ADD / DROP function unit, 114 Optical signal multiplexing / demultiplexing function unit, 115 Optical signal transmitting and receiving unit, 116 First turnback function unit, 117 Second turnback function unit, 120 Communication unit, 121 Control unit, 130 APN-I, 131 Optical repeater unit, 132 Optical signal transmitting and receiving unit, 133 Optical signal cross-connect function unit, 134 Wavelength conversion function unit, 135 Optical signal transmitting and receiving unit, 136 Turnback function unit, 140 Communication unit, 141 Control unit, 150 APN-T, 151 Optical conversion unit, 152 Client accommodation unit, 153 Digital signal processing unit, 154 Optical signal transmitting / receiving unit, 160 Communication unit, 161 Control unit, 170 APN-C, 171 Communication unit, 172 Control unit.

Claims

1. An optical transmission control method for controlling an optical path comprising a first optical transmission termination device, one or more first optical transmission devices having an ADD / DROP function for adding or extracting an optical signal of a specific wavelength to an optical signal and a multiple-to-multiply / multiply function for multiple-to-multiply or multiply the optical signal, one or more second optical transmission devices having a cross-connect function for switching the optical signal, and a second optical transmission termination device, If the optical signal transmitted from the first optical transmission termination device cannot be restored by the second optical transmission termination device, one device is sequentially selected from the one or more first optical transmission devices and the one or more second optical transmission devices to fold the optical signal back towards the first optical transmission termination device, and the bit error rate when the folded optical signal is received by the first optical transmission termination device is compared to identify the suspected location causing the inability to restore the optical signal. A method for controlling optical transmission characterized by the following.

2. A first optical transmission termination device, one or more first optical transmission devices having an ADD / DROP function for adding or extracting optical signals of a specific wavelength to an optical signal and a multiplication / demultiplication function for multiplication or demultiplication of optical signals, one or more second optical transmission devices having a cross-connect function for switching optical signals, and the second optical transmission termination device having a communication unit that communicates via a network, An optical transmission control device for controlling an optical path comprising the first optical transmission termination device, the one or more first optical transmission devices, the one or more second optical transmission devices, and the second optical transmission termination device, The system includes a control unit that, when an optical signal transmitted from the first optical transmission termination device cannot be restored by the second optical transmission termination device, sequentially selects one of the one or more first optical transmission devices and the one or more second optical transmission devices via the communication unit to fold the optical signal back towards the first optical transmission termination device, and identifies the suspected location of the cause of the inability to restore the optical signal by comparing the bit error rate when the folded optical signal is received by the first optical transmission termination device. An optical transmission control device characterized by the following.

3. An optical transmission control device for controlling an optical path comprising a first optical transmission termination device, one or more first optical transmission devices having an ADD / DROP function for adding or extracting optical signals of a specific wavelength to an optical signal and a multiple optical transmission device for multiple optical signals, one or more second optical transmission devices having a cross-connect function for switching optical signals, and a second optical transmission termination device, The first optical transmission termination device, the one or more first optical transmission devices, the one or more second optical transmission devices, and the second optical transmission termination device, and a communication unit that communicates via a network, The system includes a control unit that, when an optical signal transmitted from the first optical transmission termination device cannot be restored by the second optical transmission termination device, sequentially selects one of the one or more first optical transmission devices and the one or more second optical transmission devices via the communication unit to fold the optical signal back towards the first optical transmission termination device, and identifies the suspected location of the cause of the inability to restore the optical signal by comparing the bit error rate when the folded optical signal is received by the first optical transmission termination device. An optical transmission control device characterized by the following.

4. After identifying the suspected location, the control unit determines the factor causing the degradation of the optical signal at the suspected location by comparing a first evaluation value when the first optical transmission termination device receives an optical signal that has been folded back in a first optical path containing the suspected location, and a second evaluation value when the first optical transmission termination device receives an optical signal that has been folded back in a second optical path that does not contain the suspected location. The optical transmission control device according to claim 2 or 3, characterized by the above.

5. The first evaluation value and the second evaluation value are signal-to-noise ratios calculated using the known pattern, The control unit determines that the factor is an optical amplifier when the difference between the first evaluation value and the second evaluation value is greater than a threshold. The optical transmission control device according to claim 4, characterized by the above.

6. The first evaluation value and the second evaluation value are frequency characteristics obtained by frequency analysis of the known pattern. The control unit determines that the factor is an optical filter when the difference between the first evaluation value and the second evaluation value is greater than a threshold. The optical transmission control device according to claim 4, characterized by the above.

7. An optical path comprising a first optical transmission termination device, one or more first optical transmission devices, one or more second optical transmission devices, and a second optical transmission termination device, An optical transmission system comprising an optical transmission control device for controlling the optical path, Each of the one or more first optical transmission devices is: A first optical signal transmitting and receiving unit that transmits and receives optical signals, The optical signal ADD / DROP function unit adds or extracts an optical signal of a specific wavelength to the optical signal received by the first optical signal transmitting / receiving unit, A first turnback function unit that returns the optical signal processed by the optical signal ADD / DROP function unit back to the optical signal ADD / DROP function unit and transmits it from the first optical signal transmitting / receiving unit, A second optical signal transmitting and receiving unit that transmits and receives optical signals, An optical signal combining / decompression function unit performs combining or decompression on the optical signal received by the second optical signal transmitting / receiving unit, A second turnback function unit returns the optical signal processed by the optical signal multiplexing / demultiplexing function unit to the optical signal multiplexing / demultiplexing function unit and transmits it from the second optical signal transmitting / receiving unit, It comprises a first communication unit that communicates via a network, Each of the one or more second optical transmission devices is: A third optical signal transmitting and receiving unit that transmits and receives optical signals, A fourth optical signal transmitting and receiving unit that transmits and receives optical signals, An optical signal cross-connect function unit that performs switching of optical signals received by the third optical signal transmitting / receiving unit and the fourth optical signal transmitting / receiving unit, A third turnback function unit that receives an optical signal in the third optical signal transmitting / receiving unit and processes it in the optical signal cross-connect function unit, folds it back to the optical signal cross-connect function unit, and transmits it from the third optical signal transmitting / receiving unit, and a third turnback function unit that receives an optical signal in the fourth optical signal transmitting / receiving unit and processes it in the optical signal cross-connect function unit, folds it back to the optical signal cross-connect function unit, and transmits it from the fourth optical signal transmitting / receiving unit, It comprises a second communication unit that communicates via the aforementioned network, The optical transmission control device is The first optical transmission termination device, the one or more first optical transmission devices, the one or more second optical transmission devices, and the second optical transmission termination device, and a third communication unit that communicates via a network, The system includes a control unit that, when an optical signal transmitted from the first optical transmission termination device cannot be restored by the second optical transmission termination device, sequentially selects one of the one or more first optical transmission devices and the one or more second optical transmission devices via the third communication unit to fold the optical signal back towards the first optical transmission termination device, and identifies the suspected location of the cause of the inability to restore the optical signal by comparing the bit error rate when the folded optical signal is received by the first optical transmission termination device. An optical transmission system characterized by the following.