Optical node, signal processing device, and optical communication system

Abstract

This optical communication device is connected to an optical path in an optical communication network and is provided with a controller. The controller generates an additional information signal that has a different carrier frequency from that of a main optical signal. The controller generates an output optical signal by superimposing the additional information signal onto the main optical signal, and outputs the output optical signal to the optical path. The additional information signal includes a time stamp that shows the timing at which the additional information signal is generated.

Description

[Technical Field]

[0001] The present disclosure relates to time stamping using optical signals in optical communication networks. [Background technology]

[0002] One known method for measuring signal transmission delay in a communication network is active measurement, which measures signal transmission delay by inserting probe packets into the communication network.

[0003] Non-Patent Document 1 proposes a "pass-type delay measurement method" in which a timestamp is assigned to a probe packet for each measurement point. FIG. 1 is a conceptual diagram for explaining the pass-type delay measurement method disclosed in Non-Patent Document 1. Probe transmitter A sends a probe packet (e.g., a UDP packet) toward probe receiver B. The communication path between probe transmitter A and probe receiver B is provided with timestamp units C-1, C-2, and C-3 and communication devices D-1 and D-2. Synchronized high-precision clocks are connected to the timestamp units C-1, C-2, and C-3, respectively, to provide highly accurate time information. Each of the timestamp units C-1, C-2, and C-3 assigns the time of passage of the probe packet as a timestamp to the end of the probe packet. The probe packet received by probe receiver B contains the timestamp assigned by each of the timestamp units C-1, C-2, and C-3. Based on the timestamps, it is possible to measure the delay time (the sum of processing delay, queuing delay, and serialization delay) occurring in each of the communication devices D-1 and D-2. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Nakagawa et al., "Development of a High-Precision Time Server," Information Processing, Vol. 49, No. 10, pp. 1184-1191, 2008. Summary of the Invention [Problem to be solved by the invention]

[0005] According to the delay measurement method described above, probe packets for delay measurement are transmitted separately from the main signal, and the overhead caused by the probe packets increases the transmission delay of the main signal and reduces the transmission capacity of the main signal.

[0006] An object of the present disclosure is to provide a technology that can suppress an increase in transmission delay of a main signal and a decrease in transmission capacity of the main signal when timestamps are used in a communication network. [Means for solving the problem]

[0007] The first aspect relates to an optical communication device connected to an optical path in an optical communication network. The optical communication device includes a controller. The controller generating an additional information signal having a carrier frequency different from that of the main optical signal; generating an output optical signal by superimposing the additional information signal on the main optical signal; Output optical signal to optical path It is configured as follows. The additional information signal includes a timestamp that reflects the timing at which the additional information signal is generated.

[0008] The second aspect relates to a signal processing device connected to an optical communication device via an optical path in an optical communication network. The optical communication device is configured to generate an additional information signal having a carrier frequency different from that of the main optical signal, generate an output optical signal by superimposing the additional information signal on the main optical signal, and output the output optical signal to an optical path. The additional information signal includes a timestamp that reflects the timing at which the additional information signal is generated. The signal processing device includes a controller. The controller receiving an output optical signal output from an optical communication device via an optical path; extracting an additional information signal from the received output optical signal; The timestamp included in the additional information signal and the arrival timestamp reflecting the timing at which the additional information signal arrived at the signal processing device are stored in a storage device. It is configured as follows.

[0009] The third aspect relates to an optical communication method by an optical communication device connected to an optical path in an optical communication network. The optical communication method is generating an additional information signal having a carrier frequency different from that of the main optical signal; generating an output optical signal by superimposing the additional information signal on the main optical signal; Outputting the output optical signal to the optical path. Includes. The additional information signal includes a timestamp that reflects the timing at which the additional information signal is generated.

[0010] A fourth aspect relates to a signal processing method by a signal processing device connected to an optical communication device via an optical path in an optical communication network. The optical communication device is configured to generate an additional information signal having a carrier frequency different from that of the main optical signal, generate an output optical signal by superimposing the additional information signal on the main optical signal, and output the output optical signal to an optical path. The additional information signal includes a timestamp that reflects the timing at which the additional information signal is generated. The signal processing method is receiving an output optical signal output from an optical communication device via an optical path; extracting an additional information signal from the received output optical signal; a process of storing a timestamp included in the additional information signal and an arrival timestamp reflecting the timing at which the additional information signal arrived at the signal processing device in a storage device; Includes. [Effects of the Invention]

[0011] According to the present disclosure, an additional information signal having a carrier frequency different from that of the optical main signal is superimposed on the optical main signal. The additional information signal includes a timestamp that reflects the timing at which the additional information signal is generated. The additional information signal including the timestamp is superimposed on the optical main signal and transmitted together with the optical main signal. A special signal dedicated to delay measurement is not transmitted separately from the optical main signal. Therefore, it is possible to suppress an increase in transmission delay of the optical main signal and a decrease in the transmission capacity of the optical main signal. By using such a timestamp, it is possible to measure delay time in an optical communication network, for example. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a conceptual diagram for explaining a delay measurement method in the prior art. [Figure 2] 1 is a block diagram schematically illustrating a configuration example of an optical communication system according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a block diagram illustrating an example of a configuration related to delay measurement according to an embodiment of the present disclosure. [Figure 4] FIG. 2 is a conceptual diagram illustrating a frame structure of an additional information signal according to an embodiment of the present disclosure. [Figure 5] FIG. 10 is a conceptual diagram illustrating an example of delay measurement result information according to an embodiment of the present disclosure. [Figure 6] 1 is a block diagram illustrating an example of a configuration related to delay measurement based on TDM according to an embodiment of the present disclosure. [Figure 7] FIG. 1 is a block diagram illustrating an example configuration of a user terminal related to delay measurement based on TDM according to an embodiment of the present disclosure. [Figure 8] FIG. 2 is a block diagram illustrating a first exemplary configuration of an optical node related to delay measurement based on TDM according to an embodiment of the present disclosure. [Figure 9] FIG. 10 is a block diagram illustrating a second exemplary configuration of an optical node related to delay measurement based on TDM according to an embodiment of the present disclosure. [Figure 10]1 is a block diagram showing an example configuration of a signal processing device related to delay measurement based on TDM according to an embodiment of the present disclosure. [Figure 11] 1 is a block diagram illustrating an example of a configuration related to FDM-based delay measurement according to an embodiment of the present disclosure. [Figure 12] FIG. 2 is a block diagram illustrating a first exemplary configuration of an optical node related to delay measurement based on FDM according to an embodiment of the present disclosure. [Figure 13] FIG. 10 is a block diagram illustrating a second exemplary configuration of an optical node related to delay measurement based on FDM according to an embodiment of the present disclosure. [Figure 14] 1 is a block diagram illustrating an example configuration of a signal processing device related to FDM-based delay measurement according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0013] Embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0014] 1. Optical communication systems 2 is a block diagram schematically illustrating an example of the configuration of an optical communication system 1 according to this embodiment. The optical communication system 1 includes a plurality of optical communication devices that perform optical communication. An optical communication network 5 is formed by connecting the plurality of optical communication devices via an optical path 2 (optical fiber). For example, the optical communication network 5 is an all-photonics network (APN) that, in principle, transmits / transfers signals as optical signals.

[0015] The optical communication device includes a user terminal 10 and an optical node 20. In the example shown in Fig. 2, the user terminal 10 and multiple optical nodes 20 (20-1, 20-2, 20-3, etc.) are connected in series via an optical path 2. The user terminal 10 is connected to an upper network via the multiple optical nodes 20.

[0016] The optical communication system 1 further includes a network management device 50 that manages the optical communication network 5. The network management device 50 is communicably connected to the user terminals 10 and each optical node 20, and manages the user terminals 10 and each optical node 20. The network management device 50 is installed, for example, in a telecommunications carrier's office.

[0017] Delay measurement in the optical communication network 5 according to this embodiment will be described below.

[0018] 2. Overview of Latency Measurement 3 is a block diagram schematically illustrating an example of a configuration related to delay measurement according to this embodiment. In addition to the above-described configuration, the optical communication system 1 further includes a signal processing device 30 for delay measurement in the optical communication network 5. The signal processing device 30 is included in, for example, a network management device 50. Alternatively, the signal processing device 30 may be provided separately from the network management device 50.

[0019] In the following, as an example, the components for delay measurement are considered to be a user terminal 10 (transmitting device), an optical node 20-1 (relay device), and a signal processing device 30 (receiving device). The same applies when the number of optical nodes 20 increases.

[0020] The user terminal 10 is connected to the optical node 20-1. The optical node 20-1 is connected to the signal processing device 30 via the optical node 20-2. The optical path 2A is an optical path between the user terminal 10 and the optical node 20-1. The optical path 2B is an optical path between the optical node 20-1 and the signal processing device 30 via the optical node 20-2. The optical path 2C is an optical path between the user terminal 10 and the signal processing device 30 via the optical nodes 20-1 and 20-2.

[0021] Synchronized high precision clocks 40-1, 40-2, and 40-3 are connected to the user terminal 10, the optical node 20-1, and the signal processing device 30, respectively. For example, each high precision clock 40 acquires time information from an NTP (Network Time Protocol) server. The user terminal 10, the optical node 20-1, and the signal processing device 30 acquire high precision time information from the high precision clocks 40-1, 40-2, and 40-3, respectively.

[0022] A user terminal 10 (transmitting device) transmits a main optical signal MS to the optical communication network 5. During delay measurement, the user terminal 10 generates a first additional information signal AS1 for delay measurement. The first additional information signal AS1 includes a first timestamp TS1 that reflects the timing at which the first additional information signal AS1 is generated. The first timestamp TS1 may be the exact timing at which the first additional information signal AS1 is generated, or may be close to the timing at which the first additional information signal AS1 is generated. The first timestamp TS1 is obtained based on time information obtained from a high-precision clock 40-1. The carrier frequency of the first additional information signal AS1 is different from the carrier frequency of the main optical signal MS. Typically, the carrier frequency of the first additional information signal AS1 is sufficiently lower than the carrier frequency of the main optical signal MS. For example, an auxiliary management and control channel (AMCC) is used for the first additional information signal AS1.

[0023] In this way, the user terminal 10 generates a first additional information signal AS1 that includes the first timestamp TS1 and has a carrier frequency different from that of the main optical signal MS. Furthermore, the user terminal 10 generates a first optical signal OS1 by superimposing the generated first additional information signal AS1 on the main optical signal MS (OS1 = MS + AS1). Then, the user terminal 10 outputs the first optical signal OS1 (output optical signal) in which the first additional information signal AS1 is superimposed on the main optical signal MS to the optical path 2A on the optical node 20-1 side.

[0024] The optical node 20-1 (repeater) receives a first optical signal OS1 input from the optical path 2A on the user terminal 10 side. In response to the first optical signal OS1 (input optical signal) including the first additional information signal AS1, the optical node 20-1 generates a second additional information signal AS2 for delay measurement. The second additional information signal AS2 includes a second timestamp TS2 reflecting the timing at which the second additional information signal AS2 is generated. The second timestamp TS2 may be the exact timing at which the second additional information signal AS2 is generated, or may be close to the timing at which the second additional information signal AS2 is generated. The second timestamp TS2 is obtained based on time information obtained from the high-precision clock 40-2. The carrier frequency of the second additional information signal AS2 is different from the carrier frequency of the main optical signal MS. Typically, the carrier frequency of the second additional information signal AS2 is sufficiently lower than the carrier frequency of the main optical signal MS. For example, AMCC is used for the second additional information signal AS2.

[0025] In this way, the optical node 20-1 generates a second additional information signal AS2 that includes the second timestamp TS2 and has a carrier frequency different from that of the main optical signal MS. Furthermore, the optical node 20-1 generates the second optical signal OS2 by superimposing the second additional information signal AS2 on the main optical signal MS of the first optical signal OS1 (OS2 = OS1 + AS2 = MS + AS1 + AS2). Here, time division multiplexing (TDM) or frequency division multiplexing (FDM) can be considered as a method for multiplexing the first additional information signal AS1 and the second additional information signal AS2. A method for multiplexing the first additional information signal AS1 and the second additional information signal AS2 based on TDM or FDM will be described in detail later. Then, the optical node 20-1 outputs the second optical signal OS2 (output optical signal) in which the first additional information signal AS1 and the second additional information signal AS2 are superimposed on the main optical signal MS to the optical path 2B on the signal processing device 30 side.

[0026] The optical node 20-2 receives the second optical signal OS2 from the optical node 20-1. The optical node 20-2 branches the received second optical signal OS2 and transfers it to the upper network and the signal processing device 30.

[0027] The signal processing device 30 (receiving device) receives the second optical signal OS2 via the optical path 2B. The second optical signal OS2 includes a first additional information signal AS1 and a second additional information signal AS2 superimposed on the main optical signal MS. The signal processing device 30 extracts (separates) the first additional information signal AS1 and the second additional information signal AS2 from the second optical signal OS2 by using a filter. Furthermore, the signal processing device 30 demodulates the first additional information signal AS1 to obtain a first timestamp TS1. Similarly, the signal processing device 30 demodulates the second additional information signal AS2 to obtain a second timestamp TS2.

[0028] Furthermore, the signal processing device 30 acquires a third timestamp TS3 (arrival timestamp) that reflects the timing at which the first additional information signal AS1 arrives at the signal processing device 30. Similarly, the signal processing device 30 acquires a fourth timestamp TS4 (arrival timestamp) that reflects the timing at which the second additional information signal AS2 arrives at the signal processing device 30. The third timestamp TS3 and the fourth timestamp TS4 are obtained based on time information acquired from the high-precision clock 40-3.

[0029] In this way, the signal processing device 30 acquires the first timestamp TS1, the second timestamp TS2, the third timestamp TS3, and the fourth timestamp TS4. Information about each timestamp TS is stored in the storage device of the signal processing device 30.

[0030] Furthermore, the signal processing device 30 calculates the delay time (signal transmission delay) in each of the optical paths 2A, 2B, and 2C based on the first timestamp TS1, the second timestamp TS2, the third timestamp TS3, and the fourth timestamp TS4. Specifically, the delay time in the optical path 2A between the user terminal 10 and the optical node 20-1 is given as "TS2-TS1." The delay time in the optical path 2B between the optical node 20-1 and the signal processing device 30 is given as "TS4-TS2." The delay time in the optical path 2C between the user terminal 10 and the signal processing device 30 is given as "TS3-TS1."

[0031] Figure 4 is a conceptual diagram showing the frame structure of the additional information signal AS. The frame of the additional information signal AS includes an additional information storage section and an ID storage section. The additional information storage section stores additional information such as a timestamp TS. The ID storage section stores identification information of the device that added the additional information (user terminal 10, optical node 20, etc.). When adding additional information, each device stores the additional information in the additional information storage section and stores its own identification information in the ID storage section.

[0032] FIG. 5 is a conceptual diagram showing an example of delay measurement result information indicating the results of delay measurement. The delay measurement result information indicates the correspondence between the identification information of a device and the additional information added by the device. Furthermore, the delay measurement result information indicates the correspondence between the optical path (section) and the delay time. The signal processing device 30 generates such delay measurement result information and stores it in a storage device. The delay measurement result information is sent to, for example, a network management device 50 and is used for network quality management by the network management device 50.

[0033] <Effects> As described above, according to this embodiment, an additional information signal AS having a carrier frequency different from that of the main optical signal MS is superimposed on the main optical signal MS. The additional information signal AS includes a timestamp TS that reflects the timing at which the additional information signal AS is generated. By using such a timestamp TS, it is possible to measure the delay time in the optical communication network 5.

[0034] The additional information signal AS including the timestamp TS is superimposed on the main optical signal MS and transmitted to the optical path 2 together with the main optical signal MS. Unlike the probe packet of the prior art, a special signal dedicated to delay measurement is not transmitted separately from the main optical signal MS. Therefore, it is possible to suppress an increase in the transmission delay of the main optical signal MS and a decrease in the transmission capacity of the main optical signal MS.

[0035] Furthermore, the timestamp TS can be added without photoelectric conversion of the optical main signal MS, which eliminates the processing delay associated with photoelectric conversion and the overhead associated with adding the timestamp TS.

[0036] The time stamp TS according to this embodiment can also be called an “optical time stamp.” According to this embodiment, by using the optical time stamp, it is possible to suppress an increase in the transmission delay of the optical main signal MS and a decrease in the transmission capacity of the optical main signal MS.

[0037] The delay measurements based on TDM and FDM according to this embodiment will be described in detail below.

[0038] 3. TDM-based delay measurement FIG. 6 is a block diagram schematically showing an example of a configuration related to delay measurement based on TDM according to this embodiment.

[0039] The user terminal 10 includes a controller 100. During delay measurement, the controller 100 generates a first additional information signal AS1. The first additional information signal AS1 includes a first timestamp TS1 that reflects the timing at which the first additional information signal AS1 is generated. The carrier frequency of the first additional information signal AS1, that is, a "first carrier frequency f1," is sufficiently lower than the carrier frequency of the main optical signal MS. The controller 100 generates a first optical signal OS1 by superimposing the first additional information signal AS1 on the main optical signal MS. Then, the controller 100 outputs the generated first optical signal OS1 to an optical path 2A on the optical node 20-1 side.

[0040] The optical node 20-1 includes a controller 200. The controller 200 receives a first optical signal OS1 (input optical signal) input from an optical path 2A on the user terminal 10 side. In response to the first optical signal, the controller 200 generates a second additional information signal AS2. The second additional information signal AS2 includes a second timestamp TS2 that reflects the timing at which the second additional information signal AS2 is generated. The carrier frequency of the second additional information signal AS2 is the same "first carrier frequency f1" as that of the first additional information signal AS1. The controller 200 generates the second optical signal OS2 by superimposing the second additional information signal AS2 on the main optical signal MS of the first optical signal OS1. At this time, as shown in FIG. 6, the controller 200 superimposes the second additional information signal AS2 on the main optical signal MS so that the second additional information signal AS2 does not overlap with the first additional information signal AS1. Then, the controller 200 outputs the generated second optical signal OS2 (output optical signal) to the optical path 2B on the signal processing device 30 side.

[0041] The signal processing device 30 includes a controller 300. The controller 300 receives a second optical signal OS2 (output optical signal) output from the optical node 20-1 via the optical path 2B. The controller 300 extracts (separates) a first additional information signal AS1 and a second additional information signal AS2 from the second optical signal OS2 by using a filter. Furthermore, the controller 300 acquires a first timestamp TS1 included in the first additional information signal AS1 and a second timestamp TS2 included in the second additional information signal AS2.

[0042] The controller 300 also acquires a third timestamp TS3 and a fourth timestamp TS4 (arrival timestamps) that reflect the timings at which the first additional information signal AS1 and the second additional information signal AS2 arrive at the controller 300. The controller 300 then calculates the delay times for each of the optical paths 2A, 2B, and 2C based on the first timestamp TS1, the second timestamp TS2, the third timestamp TS3, and the fourth timestamp TS4. The controller 300 stores information about each timestamp TS and delay measurement result information (see FIG. 5) that indicates information about the delay times for each optical path 2A.

[0043] 3-1. Example of user terminal configuration 7 is a block diagram showing an example configuration of a user terminal 10 related to delay measurement. The user terminal 10 includes an E / O converter and a controller 100. The E / O converter converts a main signal (electrical signal) into a main optical signal MS. The controller 100 receives the main optical signal MS output from the E / O converter.

[0044] The controller 100 includes an additional information signal superimposing unit 140. During delay measurement, the additional information signal superimposing unit 140 generates a first additional information signal AS1 and superimposes the first additional information signal AS1 on the main optical signal MS. More specifically, the additional information signal superimposing unit 140 includes a carrier generator 141, a timestamp acquiring unit 143, and an optical modulator 150.

[0045] Carrier wave generator 141 generates a carrier wave of a first carrier frequency f1. Time stamp acquisition unit 143 acquires time information from high precision clock 40-1 and acquires a first time stamp TS1. Time stamp acquisition unit 143 is realized by, for example, a processor.

[0046] The optical modulator 150 receives the main optical signal MS output from the E / O converter via the optical path 101. The optical modulator 150 also performs modulation based on a carrier wave with a first carrier frequency f1 and a first timestamp TS1 to generate a first additional information signal AS1. The optical modulator 150 then generates a first optical signal OS1 by superimposing the first additional information signal AS1 on the main optical signal MS. The optical modulator 150 then outputs the generated first optical signal OS1 to the optical path 105.

[0047] The additional information storage section of the frame of the first additional information signal AS1 (see FIG. 4) stores a first timestamp TS1. The ID storage section of the frame of the first additional information signal AS1 stores, for example, identification information of the optical modulator 150.

[0048] 3-2. Optical node configuration example 3-2-1. First configuration example 8 is a block diagram showing a first example of the configuration of an optical node 20-1 related to delay measurement based on TDM. The controller 200 of the optical node 20-1 includes an optical branching unit 210, a trigger generating unit 220, and an additional information signal superimposing unit 240.

[0049] A first optical signal OS1 is input to the optical branching device 210 via an optical path 201. The optical branching device 210 is connected to the trigger generating unit 220 via an optical path 202, and is also connected to the additional information signal superimposing unit 240 via an optical path 203. The optical branching device 210 branches the first optical signal OS1 (input optical signal) and transfers it to the trigger generating unit 220 and the additional information signal superimposing unit 240.

[0050] The trigger generation unit 220 generates a trigger for generating a second additional information signal AS2 during delay measurement. More specifically, the trigger generation unit 220 receives an input optical signal from the optical splitter 210. The trigger generation unit 220 determines whether the input optical signal includes the first additional information signal AS1. If the input optical signal includes the first additional information signal AS1, the trigger generation unit 220 determines that delay measurement is being performed and generates a trigger signal TR. The trigger generation unit 220 then outputs the trigger signal TR to the additional information signal superimposing unit 240.

[0051] For example, the trigger generation unit 220 includes an O / E converter 221, a low-pass filter 222, and a determination unit 223. An input optical signal is input to the O / E converter 221 via the optical path 202. The O / E converter 221 converts the input optical signal into an electrical signal. The electrical signal is input to the determination unit 223 via the low-pass filter 222. The low-pass filter 222 is configured to transmit signals in a frequency band not exceeding the vicinity of the first carrier frequency f1. The determination unit 223 receives the electrical signal output from the low-pass filter 222. The determination unit 223 determines whether or not a first additional information signal AS1 that is not noise is present based on the electrical signal. If the first additional information signal AS1 is present, the determination unit 223 determines that delay measurement is being performed and outputs a trigger signal TR to the additional information signal superimposition unit 240. The determination unit 223 is realized, for example, by a processor.

[0052] In this way, the trigger generation unit 220 autonomously detects that the input optical signal contains the first additional information signal AS1. In other words, the trigger generation unit 220 autonomously detects that delay measurement is being performed. Then, upon detecting the first additional information signal AS1, the trigger generation unit 220 autonomously issues a trigger signal TR. The above configuration example makes it possible to prevent erroneous triggers from being issued due to noise caused by disturbances such as environmental fluctuations within the optical communication network 5.

[0053] In response to the trigger signal TR, the additional information signal superimposing unit 240 generates a second additional information signal AS2 and superimposes the second additional information signal AS2 on the main optical signal MS of the first optical signal OS1. More specifically, the additional information signal superimposing unit 240 includes a carrier generator 241, a timestamp acquiring unit 243, a signal delay unit 245, and an optical modulator 250.

[0054] Carrier wave generator 241 generates a carrier wave of first carrier frequency f1. Time stamp acquisition unit 243 acquires time information from high precision clock 40-2 and acquires second time stamp TS2. Time stamp acquisition unit 243 is realized by, for example, a processor.

[0055] The first optical signal OS1 is input to the signal delay unit 245 via the optical path 203. The signal delay unit 245 delays the first optical signal OS1 by buffering the first optical signal OS1 for a certain period of time. The certain period of time is set to be slightly shorter than the time from when the first optical signal OS1 is transferred from the optical branching device 210 to the optical path 202 to when the second additional information signal AS2 is generated in response to the trigger signal TR. The signal delay unit 245 is realized by, for example, an optical fiber delay line.

[0056] The optical modulator 250 receives the first optical signal OS1 output from the signal delay unit 245. The optical modulator 250 also performs modulation based on a carrier wave having a first carrier frequency f1 and a second timestamp TS2 to generate a second additional information signal AS2. The optical modulator 250 then superimposes the second additional information signal AS2 onto the optical main signal MS of the first optical signal OS1 to generate a second optical signal OS2. Because a slight time difference is provided by the signal delay unit 245, the second additional information signal AS2 is superimposed onto the optical main signal MS immediately after the first additional information signal AS1 superimposed onto the optical main signal MS passes through the optical modulator 250 (see FIG. 6). That is, the second additional information signal AS2 is superimposed onto the optical main signal MS so as not to overlap with the first additional information signal AS1. The optical modulator 250 then outputs the generated second optical signal OS2 to the optical path 205.

[0057] The additional information storage section of the frame of the second additional information signal AS2 (see FIG. 4) stores a second timestamp TS2. The ID storage section of the frame of the second additional information signal AS2 stores, for example, identification information of the optical modulator 250.

[0058] 3-2-2. Second configuration example Fig. 9 is a block diagram showing a second configuration example of the optical node 20-1 related to delay measurement based on TDM. Descriptions that overlap with the first configuration example shown in Fig. 8 will be omitted as appropriate. In the second configuration example, the controller 200 of the optical node 20-1 includes a trigger receiving unit 230 and an additional information signal superimposing unit 240.

[0059] The trigger receiving unit 230 communicates with the network management device 50 and receives a trigger signal TR from the network management device 50. The trigger receiving unit 230 outputs the received trigger signal TR to the additional information signal superimposing unit 240.

[0060] The additional information signal superimposing unit 240 includes a carrier generator 241, a timestamp acquiring unit 243, and an optical modulator 250. The carrier generator 241 and the timestamp acquiring unit 243 are the same as those in the first configuration example shown in FIG. 8. The optical modulator 250 receives the first optical signal OS1 via the optical path 204. The optical modulator 250 superimposes the second additional information signal AS2 on the main optical signal MS of the first optical signal OS1 to generate a second optical signal OS2. The optical modulator 250 then outputs the generated second optical signal OS2 to the optical path 205.

[0061] The delay time between the network management device 50 and the controller 200 is known. The network management device 50 also knows a delay measurement schedule in which the user terminal 10 transmits the first additional information signal AS1. The network management device 50 determines the timing of sending the trigger signal TR based on the delay measurement schedule. More specifically, the network management device 50 transmits the trigger signal TR to the controller 200 at a timing such that the second additional information signal AS2 is superimposed on the first additional information signal AS1 immediately after the first additional information signal AS1 passes through the optical modulator 250. As a result, the second additional information signal AS2 is superimposed on the optical main signal MS immediately after the first additional information signal AS1 superimposed on the optical main signal MS passes through the optical modulator 250 (see FIG. 6). In other words, the second additional information signal AS2 is superimposed on the optical main signal MS so that the second additional information signal AS2 does not overlap with the first additional information signal AS1.

[0062] According to the second configuration example, it is possible to simplify the configuration of the controller 200 of the optical node 20-1. This allows for a reduction in the cost of the optical node 20-1. Furthermore, since the optical splitter 210 is not required, it is possible to avoid an increase in optical insertion loss. This is advantageous for extending the transmission distance, etc.

[0063] 3-3. Example of signal processing device configuration 10 is a block diagram showing an example of the configuration of a signal processing device 30 related to delay measurement based on TDM. The controller 300 of the signal processing device 30 includes an O / E converter 310, a separator 320, an additional information processor 340, and a storage device 350.

[0064] The second optical signal OS2 output from the optical node 20-1 is input to the O / E converter 310. The O / E converter 310 converts the input second optical signal OS2 into an electrical signal and outputs the electrical signal to the demultiplexer 320.

[0065] The demultiplexer 320 receives an electrical signal corresponding to the second optical signal OS2 and demultiplexes the electrical signal corresponding to the second optical signal OS2 into a first additional information signal AS1 (electrical signal), a second additional information signal AS2 (electrical signal), and a main signal.

[0066] More specifically, the demultiplexer 320 includes a branching unit 321, a low-pass filter 330, and a high-pass filter 333. The branching unit 321 branches the electrical signal corresponding to the second optical signal OS2 and transfers the branched signal to the low-pass filter 330 and the high-pass filter 333. The low-pass filter 330 is configured to transmit signals in a frequency band not exceeding the first carrier frequency f1. The low-pass filter 330 extracts a first additional information signal AS1 (electrical signal) and a second additional information signal AS2 (electrical signal) from the electrical signal corresponding to the second optical signal OS2. The extracted first additional information signal AS1 and second additional information signal AS2 are output to the additional information processing unit 340. Meanwhile, the high-pass filter 333 has a cutoff frequency band from frequency 0 to the first carrier frequency f1. The high-pass filter 333 extracts a main signal (electrical signal) from the electrical signal corresponding to the second optical signal OS2. The extracted main signal is transferred to a main signal receiving unit (not shown).

[0067] The additional information processing unit 340 demodulates the first additional information signal AS1 to obtain a first timestamp TS1. Similarly, the additional information processing unit 340 demodulates the second additional information signal AS2 to obtain a second timestamp TS2. The additional information processing unit 340 also obtains a third timestamp TS3 (arrival timestamp) that reflects the timing at which the first additional information signal AS1 arrives. Similarly, the additional information processing unit 340 obtains a fourth timestamp TS4 (arrival timestamp) that reflects the timing at which the second additional information signal AS2 arrives. The third timestamp TS3 and the fourth timestamp TS4 are obtained based on time information obtained from the high-precision clock 40-3.

[0068] In this way, the additional information processing unit 340 acquires the first timestamp TS1, the second timestamp TS2, the third timestamp TS3, and the fourth timestamp TS4. Furthermore, the additional information processing unit 340 calculates the delay time for each of the optical paths 2A, 2B, and 2C based on the first timestamp TS1, the second timestamp TS2, the third timestamp TS3, and the fourth timestamp TS4. The additional information processing unit 340 then stores in the storage device 350 delay measurement result information (see FIG. 5) indicating information on each timestamp TS and information on the delay time for each optical path 2A.

[0069] The additional information processing unit 340 is realized by, for example, a processor. Examples of the storage device 350 include a volatile memory, a non-volatile memory, a hard disk drive (HDD), and a solid state drive (SDD).

[0070] The delay measurement result information stored in the storage device 350 may be sent to the network management device 50. For example, the network management device 50 performs network quality management based on the delay measurement result information.

[0071] Effects As described above, according to this embodiment, an additional information signal AS having a carrier frequency different from that of the main optical signal MS is superimposed on the main optical signal MS. The additional information signal AS includes a timestamp TS that reflects the timing at which the additional information signal AS is generated. By using such a timestamp TS, it is possible to measure the delay time in the optical communication network 5.

[0072] The additional information signal AS including the timestamp TS is superimposed on the optical main signal MS and transmitted together with the optical main signal MS. Unlike the probe packet of the prior art, a special signal dedicated to delay measurement is not transmitted separately from the optical main signal MS. Therefore, it is possible to suppress an increase in the transmission delay of the optical main signal MS and a decrease in the transmission capacity of the optical main signal MS.

[0073] Furthermore, the timestamp TS can be added without photoelectric conversion of the optical main signal MS, which eliminates the processing delay associated with photoelectric conversion and the overhead associated with adding the timestamp TS.

[0074] Furthermore, the first additional information signal AS1 and the second additional information signal AS2, which have the same first carrier frequency f1, are time-division multiplexed to avoid signal interference, allowing the signal processing device 30 to reliably demodulate the first timestamp TS1 and the second timestamp TS2 from the first additional information signal AS1 and the second additional information signal AS2, respectively.

[0075] Furthermore, since there is no need to generate different carrier frequencies, there is no need to prepare multiple types of carrier generators. This simplifies the configuration of the optical node 20. Furthermore, the configuration of the demultiplexer 320 of the signal processing device 30 is also simplified. These factors contribute to reducing the cost of each device.

[0076] 4. FDM-based delay measurement 11 is a block diagram showing an example of a configuration related to delay measurement based on FDM according to this embodiment. Descriptions that overlap with the above-mentioned case of TDM will be omitted where appropriate.

[0077] The user terminal 10 includes a controller 100. The controller 100 is similar to that in the TDM case described above.

[0078] The optical node 20-1 includes a controller 200. The controller 200 receives a first optical signal OS1 (input optical signal) input from an optical path 2A on the user terminal 10 side. In response to the first optical signal OS1, the controller 200 generates a second additional information signal AS2. The carrier frequency of the second additional information signal AS2 is a "second carrier frequency f2" different from the first carrier frequency f1 of the first additional information signal AS1. The controller 200 generates the second optical signal OS2 by superimposing the second additional information signal AS2 on the main optical signal MS of the first optical signal OS1. At this time, as shown in FIG. 11, the controller 200 may superimpose the second additional information signal AS2 on the main optical signal MS so that the second additional information signal AS2 and the first additional information signal AS1 at least partially overlap. The controller 200 then outputs the generated second optical signal OS2 (output optical signal) to an optical path 2B on the signal processing device 30 side.

[0079] 12 is a block diagram showing a first example configuration of an optical node 20-1 related to delay measurement based on FDM. The controller 200 of the optical node 20-1 includes an optical branching unit 210, a trigger generating unit 220, and an additional information signal superimposing unit 240. The optical branching unit 210 and the trigger generating unit 220 are the same as those in the TDM case shown in FIG.

[0080] The additional information signal superimposing unit 240 includes a carrier generator 242, a timestamp acquiring unit 243, a signal delay unit 246, and an optical modulator 250. The carrier generator 242 generates a carrier wave having a second carrier frequency f2. The signal delay unit 246 delays the first optical signal OS1 by buffering the first optical signal OS1 for a certain period of time. The certain period of time is set to be approximately the same as the time from when the first optical signal OS1 is transferred from the optical branching unit 210 to the optical path 202 to when the second additional information signal AS2 is generated in response to the trigger signal TR. Therefore, the second additional information signal AS2 is superimposed on the main optical signal MS at approximately the same timing as when the first additional information signal AS1 superimposed on the main optical signal MS passes through the optical modulator 250 (see FIG. 11). That is, the second additional information signal AS2 is superimposed on the main optical signal MS so that the second additional information signal AS2 and the first additional information signal AS1 at least partially overlap.

[0081] 13 is a block diagram showing a second example configuration of the optical node 20-1 related to delay measurement based on FDM. The controller 200 of the optical node 20-1 includes a trigger receiving unit 230 and an additional information signal superimposing unit 240. The trigger receiving unit 230 is the same as in the TDM case shown in FIG.

[0082] The additional information signal superimposing unit 240 includes a carrier generator 242, a timestamp acquiring unit 243, and an optical modulator 250. The carrier generator 242 generates a carrier wave of a second carrier frequency f2. The rest is the same as in the TDM case shown in FIG.

[0083] The delay time between the network management device 50 and the controller 200 is known. The network management device 50 also knows a delay measurement schedule in which the user terminal 10 transmits the first additional information signal AS1. The network management device 50 determines the timing of sending the trigger signal TR based on the delay measurement schedule. More specifically, the network management device 50 transmits the trigger signal TR to the controller 200 at a timing such that the second additional information signal AS2 is superimposed on the first additional information signal AS1 at the same time that the first additional information signal AS1 passes through the optical modulator 250. As a result, the second additional information signal AS2 is superimposed on the optical main signal MS at the same time that the first additional information signal AS1 superimposed on the optical main signal MS passes through the optical modulator 250 (see FIG. 11). That is, the second additional information signal AS2 is superimposed on the optical main signal MS so that the second additional information signal AS2 and the first additional information signal AS1 at least partially overlap.

[0084] 14 is a block diagram showing an example of the configuration of a signal processing device 30 related to delay measurement based on FDM. The controller 300 of the signal processing device 30 includes an O / E converter 310, a separator 320, an additional information processor 340, and a storage device 350. The O / E converter 310, the additional information processor 340, and the storage device 350 are the same as those in the TDM case shown in FIG.

[0085] The separator 320 includes a splitter 322, a first band-pass filter 331, a second band-pass filter 332, and a high-pass filter 333. The splitter 322 splits an electrical signal corresponding to the second optical signal OS2 and transfers it to the first band-pass filter 331, the second band-pass filter 332, and the high-pass filter 333. The first band-pass filter 331 is configured to transmit signals in a frequency band near the first carrier frequency f1. The first band-pass filter 331 extracts a first additional information signal AS1 (electrical signal) from the electrical signal corresponding to the second optical signal OS2. On the other hand, the second band-pass filter 332 is configured to transmit signals in a frequency band near the second carrier frequency f2. The second band-pass filter 332 extracts a second additional information signal AS2 (electrical signal) from the electrical signal corresponding to the second optical signal OS2. The extracted first additional information signal AS1 and second additional information signal AS2 are output to the additional information processing unit 340.

[0086] In this way, the first additional information signal AS1 having the first carrier frequency f1 and the second additional information signal AS2 having the second carrier frequency f2 are frequency-division multiplexed to avoid signal interference, and the signal processing device 30 can reliably demodulate the first timestamp TS1 and the second timestamp TS2 from the first additional information signal AS1 and the second additional information signal AS2, respectively. [Explanation of symbols]

[0087] 1...optical communication system, 2...optical path, 5...optical communication network, 10...user terminal, 20...optical node, 30...signal processing device, 40...high-precision clock, 50...network management device, 100...controller, 101, 105...optical path, 140...additional information signal superimposing unit, 141...carrier generator, 143...timestamp acquisition unit, 150...optical modulator, 200...controller, 201, 202, 203, 204, 205...optical path, 210...optical splitter, 220...trigger generation unit, 221...O / E converter, 222...low-pass filter, 223...determination unit, 230...trigger receiving unit, 240...additional information signal superimposing unit, 241, 242...carrier generator, 243...timestamp acquisition unit 245, 246...signal delay unit, 250...optical modulator, 300...controller, 310...O / E converter, 320...separator, 321, 322...brancher, 330...low-pass filter, 331...first band-pass filter, 332...second band-pass filter, 333...high-pass filter, 340...additional information processing unit, 350...storage device, f1...first carrier frequency, f2...second carrier frequency, AS...additional information signal, AS1...first additional information signal, AS2...second additional information signal, MS...main optical signal, OS1...first optical signal, OS2...second optical signal, TR...trigger signal, TS...timestamp, TS1...first timestamp, TS2...second timestamp

Claims

1. An optical node provided on an optical path between a transmitting device and a receiving device in an optical communication network, the transmitting device generates a first additional information signal having a carrier frequency different from that of the main optical signal, generates a first output optical signal by superimposing the first additional information signal on the main optical signal, and outputs the first output optical signal to the optical path; the first additional information signal includes a first timestamp that reflects the timing at which the first additional information signal is generated; the optical node comprises a controller; The controller receiving an input optical signal input from the optical path on the transmitting device side, the input optical signal being the main optical signal on which the first additional information signal is superimposed; generating a second additional information signal having a carrier frequency different from that of the main optical signal; superimposing the second additional information signal on the main optical signal of the input optical signal to generate a second output optical signal in which the first additional information signal and the second additional information signal are superimposed on the main optical signal; The second output optical signal is output to the optical path on the receiving device side. It is configured as follows: The second additional information signal includes a second timestamp that reflects the timing at which the second additional information signal is generated. Optical node.

2. 2. The optical node of claim 1, the carrier frequency of the first additional information signal and the carrier frequency of the second additional information signal are the same; The controller is configured to superimpose the second additional information signal onto the main optical signal such that the second additional information signal does not overlap with the first additional information signal. Optical node.

3. 2. The optical node of claim 1, the carrier frequency of the first additional information signal is a first carrier frequency; The carrier frequency of the second additional information signal is a second carrier frequency different from the first carrier frequency. Optical node.

4. 4. An optical node according to claim 1, wherein: The controller further comprises: determining whether the input optical signal includes the first additional information signal; generating a trigger signal when the input optical signal includes the first additional information signal; generating the second additional information signal in response to the trigger signal; It was configured as Optical node.

5. 4. An optical node according to claim 1, wherein: The controller further comprises: receiving a trigger signal from a network management device that controls the optical node; generating the second additional information signal in response to the trigger signal; It was configured as Optical node.

6. A signal processing device for delay measurement in an optical communication network formed by a plurality of optical communication devices, the plurality of optical communication devices, a transmitting device; an optical node provided on an optical path between the transmitting device and the signal processing device in the optical communication network; Including, The transmitting device generating a first additional information signal having a carrier frequency different from that of the main optical signal; generating a first output optical signal by superimposing the first additional information signal on the main optical signal; outputting the first output optical signal to the optical path; It is configured as follows: the first additional information signal includes a first timestamp that reflects the timing at which the first additional information signal is generated; The optical node comprises: receiving an input optical signal input from the optical path on the transmitting device side, the input optical signal being the main optical signal on which the first additional information signal is superimposed; generating a second additional information signal having a carrier frequency different from that of the main optical signal; superimposing the second additional information signal on the main optical signal of the input optical signal to generate a second output optical signal in which the first additional information signal and the second additional information signal are superimposed on the main optical signal; The second output optical signal is output to the optical path on the signal processing device side. It is configured as follows: the second additional information signal includes a second timestamp that reflects the timing at which the second additional information signal is generated; the signal processing device comprises a controller; The controller receiving the second output optical signal output from the optical node via the optical path; extracting the first additional information signal and the second additional information signal from the received second output optical signal; The first timestamp included in the first additional information signal, the second timestamp included in the second additional information signal, a third timestamp reflecting the timing at which the first additional information signal arrived at the signal processing device, and a fourth timestamp reflecting the timing at which the second additional information signal arrived at the signal processing device are stored in a storage device. It was configured as Signal processing device.

7. a plurality of optical communication devices forming an optical communication network; the plurality of optical communication devices, a transmitting device; an optical node provided on an optical path between the transmitting device and the signal processing device in the optical communication network; Including, The transmitting device generating a first additional information signal having a carrier frequency different from that of the main optical signal; generating a first output optical signal by superimposing the first additional information signal on the main optical signal; outputting the first output optical signal to the optical path; It is configured as follows: the first additional information signal includes a first timestamp that reflects the timing at which the first additional information signal is generated; The optical node comprises: receiving an input optical signal input from the optical path on the transmitting device side, the input optical signal being the main optical signal on which the first additional information signal is superimposed; generating a second additional information signal having a carrier frequency different from that of the main optical signal; superimposing the second additional information signal on the main optical signal of the input optical signal to generate a second output optical signal in which the first additional information signal and the second additional information signal are superimposed on the main optical signal; The second output optical signal is output to the optical path on the signal processing device side. It is configured as follows: The second additional information signal includes a second timestamp that reflects the timing at which the second additional information signal is generated. Optical communication system.

8. 8. The optical communication system according to claim 7, The signal processing device includes: receiving the second output optical signal output from the optical node via the optical path; extracting the first additional information signal and the second additional information signal from the received second output optical signal; The first timestamp included in the first additional information signal, the second timestamp included in the second additional information signal, a third timestamp reflecting the timing at which the first additional information signal arrived at the signal processing device, and a fourth timestamp reflecting the timing at which the second additional information signal arrived at the signal processing device are stored in a storage device. It was configured as Optical communication system.

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