Optical transmission system, optical receiving device, and delay measurement method

Abstract

Provided is an optical transmission system comprising: an optical sending device; an optical receiving device; a communication device which is an object of delay measurement; and a transmission device that transmits signals between the optical receiving device and the communication device. The optical sending device includes a main signal transfer unit that sends out a main signal. The transmission device transmits, to the optical receiving device, the following: a first main signal which was sent from the optical sending device and was passed through the communication device; and a second main signal which was sent from the optical sending device and was not passed through the communication device. The optical receiving device includes a reception processing unit that uses the first main signal and the second main signal to measure a delay that has occurred at the communication device.　

Description

[Technical Field]

[0001] The present invention relates to an optical transmission system, an optical receiving device, and a delay measurement method. [Background technology]

[0002] Conventionally, a method using probe packets has been proposed as one method for measuring delay in a network (see, for example, Non-Patent Document 1). The method shown in Non-Patent Document 1 proposes a "pass-through method" for delay measurement in which a timestamp is assigned to a probe packet at each measurement point in the network where the delay is to be measured.

[0003] 9 is a diagram for explaining the method described in Non-Patent Document 1. As shown in Fig. 9, the delay measurement method described in Non-Patent Document 1 uses a system including, for example, a probe transmitter 1, multiple clock generators 2-1 to 2-3, multiple timestamp assigners 3-1 to 3-3, multiple communication devices 4-1 to 4-2, and a probe receiver 5. The probe transmitter 1 sends out probe packets (UDP (User Datagram Protocol) packets) to the probe receiver 5.

[0004] The probe packets sent from the probe transmitter 1 pass through the timestamp assigner 3-1, communication device 4-2, timestamp assigner 3-2, communication device 4-2, and timestamp assigner 3-3 in that order before being received by the probe receiver. The timestamp assigners 3-1 to 3-3 assign time information to the end of the probe packets. For example, the timestamp assigners 3-1 to 3-3 assign time information at the time the probe packet was input to the end of the probe packet. The timestamp assigners 3-1 to 3-3 are connected to clock generators 2-1 to 2-3, which are synchronized with each other, and accurate time information is provided to the timestamp assigners 3-1 to 3-3.

[0005] Through the above processing, the time information assigned by each of the time stamp assigning units 3-1 to 3-3 is included in the probe packets received by the probe receiving unit 5. By using each piece of time information, the probe receiving unit 5 can measure the delay (for example, the sum of processing delay, queuing delay, and serialization delay) that occurs in each of the communication devices 4-1 and 4-2. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Machizawa et al., "Development of a Pass-Through High-Precision UDP Time Stamper," Transactions of the Institute of Electronics, Information and Communication Engineers, Vol. B, 2005 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the conventional delay measurement method described above increases the delay of the main signal because probe packets for delay measurement are inserted. Furthermore, the clocks provided to the timestamp assigning units 3-1 to 3-3 must be synchronized with high precision, which complicates network management. Therefore, a method is needed to measure delay in a simple manner while suppressing the delay of the main signal.

[0008] In view of the above circumstances, an object of the present invention is to provide a technique that can measure delay in a simple manner while suppressing delay in a main signal. [Means for solving the problem]

[0009] One aspect of the present invention is an optical transmission system comprising an optical transmitting device, an optical receiving device, a communication device to be measured for delay, and a transmission device that transmits signals between the optical receiving device and the communication device, wherein the optical transmitting device comprises a main signal transfer unit that transmits a main signal, the transmission device transmits to the optical receiving device a first main signal that is transmitted from the optical transmitting device and passes through the communication device, and a second main signal that is transmitted from the optical transmitting device and does not pass through the communication device, and the optical receiving device comprises a receiving processing unit that measures a delay generated in the communication device using the first main signal and the second main signal transmitted from the transmission device.

[0010] One aspect of the present invention is an optical receiving device in an optical transmission system including an optical transmitting device, an optical receiving device, a communication device to be measured for delay, and a transmission device that transmits signals between the optical receiving device and the communication device, the optical receiving device including a receiving processing unit that measures delay generated in the communication device using a first main signal sent from the optical transmitting device and transmitted at least via the communication device, and a second main signal sent from the optical transmitting device and transmitted without passing through the communication device.

[0011] One aspect of the present invention is a delay measurement method in an optical transmission system including an optical transmitting device, an optical receiving device, a communication device to be measured for delay, and a transmission device that transmits signals between the optical receiving device and the communication device, in which the optical transmitting device transmits a main signal, and the transmission device transmits to the optical receiving device a first main signal that is transmitted from the optical transmitting device and passes through the communication device, and a second main signal that is transmitted from the optical transmitting device and does not pass through the communication device, and the optical receiving device measures the delay generated in the communication device using the first main signal and the second main signal transmitted from the transmission device. [Effects of the Invention]

[0012] According to the present invention, it is possible to measure the delay in a simple manner while suppressing the delay of the main signal. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram illustrating a system configuration of an optical transmission system according to a first embodiment. [Figure 2] FIG. 3 is a sequence diagram showing a processing flow of the optical transmission system according to the first embodiment. [Figure 3] FIG. 10 is a diagram illustrating a system configuration of an optical transmission system according to a second embodiment. [Figure 4] FIG. 10 is a sequence diagram showing a processing flow of the optical transmission system according to the second embodiment. [Figure 5] FIG. 10 is a diagram illustrating a system configuration of an optical transmission system according to a third embodiment. [Figure 6] 10 is a diagram illustrating a configuration of a communication device to be subjected to delay measurement when an optical receiving device is implemented as software that runs on a processor. FIG. [Figure 7] FIG. 10 is a diagram illustrating a system configuration of an optical transmission system according to a fourth embodiment. [Figure 8] FIG. 10 is a sequence diagram showing a processing flow of an optical transmission system according to the fourth embodiment. [Figure 9] FIG. 1 is a diagram for explaining the method described in Non-Patent Document 1. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (overview) First, an outline of the present invention will be described. The optical transmission system of the present invention includes an optical transmitting device, an optical transmission device, a delay measurement target communication device, and an optical receiving device. Here, the delay measurement target communication device is, for example, a relay device such as a switch or a router. The optical transmitting device transmits a main signal to the optical receiving device via one or more lines. For example, when the optical transmitting device transmits a main signal to the optical receiving device via one line, the optical transmission device branches the main signal and forwards it to the delay measurement target communication device and the optical receiving device. When the optical transmitting device transmits a main signal to the optical receiving device via multiple lines, the optical transmission device forwards the main signal sent from one line to the delay measurement target communication device and forwards the main signal sent from another line to the optical receiving device.

[0015] The main signal transferred to the communication device under test for delay measurement undergoes address table lookup and serialization processing for transfer in the communication device under test, and is then transferred back to the optical transmission device. The optical transmission device transfers the main signal transferred from the communication device under test to the optical receiving device. The optical receiving device calculates the difference (t2 - t1) between the reception time t1 of the optical signal transferred without passing through the communication device under test for delay measurement and the reception time t2 of the optical signal transferred via the communication device under test for delay measurement. This difference represents the total value of the processing delay, queuing delay, and serialization delay in the communication device under test for delay measurement.

[0016] Measuring delay as described above does not cause an increase in the delay of the main signal as in the prior art. Furthermore, since delay measurement is also performed inside the optical receiving device, there is no need to synchronize multiple clocks. As a result, it is possible to measure delay in a simple manner while suppressing the delay of the main signal. Hereinafter, several embodiments for realizing the above method will be described.

[0017] (First embodiment) 1 is a diagram showing the system configuration of an optical transmission system 100 according to the first embodiment. The optical transmission system 100 includes an optical transmitting device 10, an optical transmitting device 20, a delay measurement target communication device 30, and an optical receiving device 40. The optical transmitting device 10 and the optical transmitting device 20, the optical transmitting device 20 and the delay measurement target communication device 30, and the optical transmitting device 20 and the optical receiving device 40 are connected via optical transmission paths.

[0018] When the optical transmitting device 10 receives a main signal from an adjacent network or device such as a server, it transmits the received main signal to the optical transmission device 20 via lines 51 and 52 as optical transmission paths. In the first embodiment, an optical main signal is input to the optical transmitting device 10. The lines 51 and 52 may be physically provided in the same fiber, or may be provided in separate, independent fibers. When the lines 51 and 52 are physically provided in the same fiber, a method of wavelength-multiplexing the main signal transmitted from the optical transmitting device 10 at different wavelengths and transmitting it can be considered. In the first embodiment, an example will be described in which the lines 51 and 52 are physically provided in the same fiber. Similarly, it is assumed that the lines connecting the optical transmission device 20 and the optical receiving device 40 are physically provided in the same fiber.

[0019] The optical transmission device 20 transmits the main signal sent from the optical sending device 10 to the delay measurement target communication device 30 and the optical receiving device 40, respectively. The optical transmission device 20 transmits the main signal received via a line 51 to the delay measurement target communication device 30. The optical transmission device 20 transmits the main signal received via a line 52 to the optical receiving device 40. In the first embodiment, the main signal transmitted by the optical sending device 10 via the line 51 is referred to as the first main signal, and the main signal transmitted by the optical sending device 10 via the line 52 is referred to as the second main signal. The optical transmission device 20 is a device capable of adding and dropping optical signals, such as a reconfigurable optical add / drop multiplexer (ROADM).

[0020] The delay measurement target communication device 30 is a device whose delay is to be measured. Here, the delay to be measured is a delay caused by processing performed within the device, such as a processing delay, a queuing delay, and a serialization delay. Note that the delay to be measured is not limited to these, and includes any delay caused by processing performed within the device. The delay measurement target communication device 30 transmits the main signal transmitted from the optical transmission device 20 back to the optical transmission device 20. At this time, the processing delay, queuing delay, and serialization delay occur in the delay measurement target communication device described above.

[0021] The optical receiving device 40 measures the processing delay in the delay measurement target communication device 30 using multiple main signals transmitted from the optical transmission device 20. For example, the optical receiving device 40 measures the processing delay in the delay measurement target communication device 30 by calculating the difference between the reception time of the first main signal and the reception time of the second main signal.

[0022] Next, the specific configurations of the functional parts of the optical transmitting device 10 and the optical receiving device 40 will be described. The optical transmitting device 10 includes a first main signal transfer unit 11 and a second main signal transfer unit 12. The first main signal transfer unit 11 transmits a first main signal to the optical transmission device 20. The first main signal transfer unit 11 includes a main signal receiving unit 111, a branching unit 112, and a transmission unit 113.

[0023] The main signal receiving unit 111 receives a main signal from an adjacent network or a device such as a server. The branching unit 112 is, for example, a splitter. The main signal received by the main signal receiving unit 111 is branched by the branching unit 112 to the sending unit 113 and the second main signal transferring unit 12.

[0024] The sending unit 113 sends the input main signal to the line 51. In the first embodiment, the main signal sent from the sending unit 113 is a first main signal. Before sending the first main signal, the sending unit 113 notifies the second main signal transfer unit 12 of the transmission timing of the first main signal.

[0025] The second main signal transfer unit 12 sends the main signal branched by the branch unit 112 to the line 52 at the send timing notified by the send unit 113, i.e., at the same timing as the transmission timing of the first main signal. In the first embodiment, the main signal sent from the second main signal transfer unit 12 is the second main signal. Note that the second main signal transfer unit 12 converts the wavelength of the second main signal to a wavelength different from the wavelength of the first main signal and sends it to the line 52. This makes it possible to send the second main signal without affecting the first main signal.

[0026] As described above, the optical transmitter 10 in the first embodiment transmits main signals of the same data from different lines.

[0027] The optical receiving device 40 includes a main signal transfer unit 41 and a reception processing unit 42. The main signal transfer unit 41 transmits a first main signal to another network or device. The main signal transfer unit 41 includes a main signal receiving unit 411 and a transmission unit 412.

[0028] The main signal receiving unit 411 receives the first main signal. The main signal receiving unit 411 records the time when the first main signal is received as first reception time information. The main signal receiving unit 411 outputs the first main signal and the first reception time information to the reception processing unit 42. Note that a splitter may be used to output the signal from the main signal receiving unit 411 to the reception processing unit 42. The main signal receiving unit 411 outputs the received first main signal to the transmission unit 412.

[0029] The sending unit 412 sends the first main signal output from the main signal receiving unit 411 to another network or device.

[0030] The reception processing unit 42 processes the main signal received by the optical receiving device 40. The reception processing unit 42 includes an optical signal receiving unit 421, a collating unit 422, and a delay measuring unit 423. The optical signal receiving unit 421 receives the second main signal transmitted from the optical transmission device 20. The optical signal receiving unit 421 records the time at which the second main signal is received as second reception time information. The optical signal receiving unit 421 outputs the second main signal and the second reception time information to the collating unit 422.

[0031] The comparison unit 422 uses the first main signal output from the main signal transfer unit 41 and the second main signal output from the optical signal receiving unit 421 to compare whether the first main signal and the second main signal received by the optical receiving device 40 are main signals of the same data.

[0032] If the first main signal and the second main signal received by the optical receiving device 40 are main signals of the same data, the matching unit 422 outputs the first reception time information of the first main signal and the second reception time information of the second main signal, which are main signals of the same data, to the delay measurement unit 423. On the other hand, if the first main signal and the second main signal received by the optical receiving device 40 are not main signals of the same data, the matching unit 422 performs matching again with another main signal after a predetermined period has elapsed.

[0033] The reason why the matching unit 422 performs matching again after a predetermined period of time has elapsed is that there is a possibility that the main signal has not been received by the optical receiving device 40 due to the influence of delays or transmission delays caused by the communication device 30 under delay measurement. Therefore, after a predetermined period of time has elapsed, there is a high possibility that a main signal that matches the main signal that has already been received will be obtained.

[0034] The delay measurement unit 423 measures the delay occurring in the delay measurement target communication device 30, using the first reception time information and second reception time information output from the comparison unit 422. Specifically, the delay measurement unit 423 calculates the delay time occurring in the delay measurement target communication device 30 by subtracting the time indicated by the first reception time information from the time indicated by the second reception time information.

[0035] The delay time information calculated by the delay measurement unit 423 may be output to another device via a network, or may be output to a display device if the optical receiving device 40 is equipped with one.

[0036] FIG. 2 is a sequence diagram showing the flow of processing in the optical transmission system 100 in the first embodiment. The main signal receiving unit 111 receives a main signal (optical signal) from the outside (step S101). The main signal receiving unit 111 outputs the received main signal to the branching unit 112. The main signal output from the main signal receiving unit 111 is branched by the branching unit 112 (step S102) and input to the sending unit 113 and the second main signal transfer unit 12.

[0037] When the main signal is input, the transmission unit 113 notifies the second main signal transfer unit 12 of the timing of transmitting the main signal (step S103). This allows the second main signal transfer unit 12 to transmit the main signal at the same timing as the first main signal transfer unit 11. The first main signal transfer unit 11 and the second main signal transfer unit 12 transmit the main signal at the same timing (step S104). Specifically, the first main signal transfer unit 11 transmits the main signal, which is the first main signal, via the line 51. The second main signal transfer unit 12 transmits the main signal, which is the second main signal, via the line 52 at the timing notified by the first main signal transfer unit 11.

[0038] The first main signal and the second main signal transmitted from the optical transmitting device 10 are received by the optical transmission device 20. The optical transmission device 20 forwards the received first main signal and the second main signal (step S105). Specifically, the optical transmission device 20 transmits the first main signal received via the line 51 to the optical transmission device 20. The optical transmission device 20 transmits the second main signal received via the line 52 to the optical receiving device 40.

[0039] The optical signal receiving unit 421 of the optical receiving device 40 receives the second main signal transmitted from the optical transmission device 20. The optical signal receiving unit 421 records the time at which the second main signal is received as second reception time information (step S106). The optical signal receiving unit 421 outputs the second main signal and the second reception time information to the collating unit 422.

[0040] The delay measurement target communication device 30 receives the first main signal transmitted from the optical transmission device 20. The delay measurement target communication device 30 transmits the received first main signal again to the optical receiving device 40 (step S107). The optical transmission device 20 transmits the first main signal transmitted from the delay measurement target communication device 30 to the optical receiving device 40 (step S108).

[0041] The main signal receiving unit 411 of the optical receiving device 40 receives the first main signal transmitted from the optical transmission device 20. The main signal receiving unit 411 records the time at which the first main signal is received as first reception time information (step S109). The main signal receiving unit 411 outputs the first main signal and the first reception time information to the collating unit 422. Furthermore, the main signal receiving unit 411 outputs the first main signal to the sending unit 412. The first main signal output to the sending unit 412 is sent to the outside.

[0042] The collating unit 422 uses the first main signal output from the main signal transfer unit 41 and the second main signal output from the optical signal receiving unit 421 to determine whether the first main signal and the second main signal received by the optical receiving device 40 are main signals of the same data (step S110). Specifically, the collating unit 422 performs photoelectric conversion on the first main signal and the second main signal and compares them. If the first main signal and the second main signal after photoelectric conversion are the same, the collating unit 422 determines that the first main signal and the second main signal after photoelectric conversion are main signals that were sent at the same time. On the other hand, if the first main signal and the second main signal after photoelectric conversion are different, the collating unit 422 determines that the first main signal and the second main signal after photoelectric conversion are not main signals that were sent at the same time.

[0043] Here, it is assumed that the first and second main signals after photoelectric conversion match. The collation unit 422 outputs the first reception time information of the first main signal and the second reception time information of the second main signal that match to the delay measurement unit 423. The delay measurement unit 423 measures the delay occurring in the delay measurement target communication device 30 using the first reception time information and second reception time information output from the collation unit 422 (step S111). Specifically, the delay measurement unit 423 calculates the delay time occurring in the delay measurement target communication device 30 by subtracting the time indicated by the first reception time information from the time indicated by the second reception time information.

[0044] In the optical transmission system 100 configured as described above, the optical transmitting device 10 transmits a main signal, and the optical transmitting device 20 transmits the main signal transmitted from the optical transmitting device 10 to the communication device 30 under test for delay measurement. The optical transmitting device 10 then transmits the main signal obtained by transmitting the main signal transmitted from the optical transmitting device 10 to the communication device 30 under test for delay measurement, together with the main signal transmitted from the optical transmitting device 10, to the optical receiving device 40. The optical receiving device then measures the delay occurring in the communication device 30 under test for delay measurement using the multiple main signals transmitted from the optical transmitting device 20. This allows the optical transmitting device 10 to simply transmit the main signal, eliminating the need to insert probe packets as in the prior art. Therefore, this does not increase the delay of the main signal as in the prior art. Furthermore, since the delay measurement is also performed within the optical receiving device 40, there is no need to synchronize multiple clocks. This makes it possible to measure delay in a simple manner while suppressing the delay of the main signal.

[0045] Furthermore, in the optical transmission system 100, the optical transmitting device 10 transmits a first main signal and a second main signal of the same data from different lines in order to measure the delay at the optical receiving device 40. The first main signal is received by the optical receiving device 40 via the delay measurement target communication device 30, and the second main signal is received by the optical receiving device 40 without passing through the delay measurement target communication device 30. Therefore, the optical receiving device 40 can calculate the delay time by taking into account at least the delay occurring in the delay measurement target communication device 30 by calculating the difference between the reception time of the first main signal and the reception time of the second main signal.

[0046] A modification of the optical transmission system 100 in the first embodiment will be described below. In cases where wavelength conversion is performed when dropping and adding signals from the optical transmission device 20 to the delay measurement target communication device 30, or when separate physical ports are provided for the first main signal transfer unit 11 and the second main signal transfer unit 12 in the optical sending device 10, and where signal collisions do not occur on the lines 51 and 52, the optical sending device 10 may be configured to transmit the first main signal and the second main signal at the same wavelength. In this case, separate physical ports are provided for the main signal transfer unit 41 and the reception processing unit 42 in the optical receiving device 40 as well. With this configuration, although the number of required physical ports increases, it is possible to suppress an increase in the transmission band.

[0047] (Second embodiment) In the first embodiment, a configuration in which a first main signal and a second main signal are transmitted from two lines in an optical transmitting device is described. In the second embodiment, a configuration in which a main signal is transmitted from one line in an optical transmitting device and the main signal is branched in an optical transmission device is described.

[0048] 3 is a diagram illustrating a system configuration of an optical transmission system 100a according to the second embodiment. The optical transmission system 100a includes an optical transmitting device 10a, an optical transmitting device 20a, a delay measurement target communication device 30, and an optical receiving device 40. The optical transmitting device 10a and the optical transmitting device 20a, the optical transmitting device 20a and the delay measurement target communication device 30, and the optical transmitting device 20a and the optical receiving device 40 are connected via optical transmission paths.

[0049] The optical transmission system 100a in the second embodiment differs from the optical transmission system 100 in the first embodiment in the configurations of the optical sending device 10a and the optical transmission device 20a. Therefore, the differences from the first embodiment will be described below.

[0050] When the optical transmitting device 10a receives a main signal from a device such as an adjacent network or a server, the optical transmitting device 10a transmits the received main signal to the optical transmitting device 20a via a line 51 serving as an optical transmission path. In the second embodiment, the main signal of an optical signal is input to the optical transmitting device 10a.

[0051] The optical transmission device 20a branches the main signal sent from the optical sending device 10a and transmits the branched main signal to the delay measurement target communication device 30 and the optical receiving device 40, respectively. For this purpose, the optical transmission device 20a includes a branching unit 21. The branching unit 21 outputs the main signal sent from the optical sending device 10a to the delay measurement target communication device 30 and the optical receiving device 40. In the second embodiment, of the main signals branched by the branching unit 21, the main signal transmitted to the delay measurement target communication device 30 is referred to as a first main signal, and the main signal transmitted to the optical receiving device 40 without being transmitted to the delay measurement target communication device 30 is referred to as a second main signal.

[0052] Next, a specific configuration of the functional units of the optical transmitter 10a will be described. The optical transmitting device 10a includes a main signal transfer unit 11a. The main signal transfer unit 11a transmits a main signal to the optical transmission device 20a. The main signal transfer unit 11a includes a main signal receiving unit 111 and a transmission unit 113a. As described above, the optical transmitting device 10a in the second embodiment does not include a branching unit 112 that branches the main signal.

[0053] The sending unit 113 a sends the main signal output from the main signal receiving unit 111 to the line 51 .

[0054] Fig. 4 is a sequence diagram showing the flow of processing in the optical transmission system 100a in the second embodiment. In Fig. 4, the same processes as those in Fig. 2 are denoted by the same reference numerals as those in Fig. 2, and the description thereof will be omitted. In step S101, when the main signal is output from the main signal receiving unit 111 to the sending unit 113a, the sending unit 113a sends the main signal via the line 51 (step S201).

[0055] The main signal transmitted from the optical transmitting device 10a is received by the optical transmission device 20a. The main signal received by the optical transmission device 20a is branched by the branching unit 21 (step S202). The optical transmission device 20a transmits the main signal branched by the branching unit 21 as a first main signal to the delay measurement target communication device 30. Furthermore, the optical transmission device 20a transmits the main signal branched by the branching unit 21 as a second main signal to the optical receiving device 40 (step S203). Thereafter, the processes from step S106 to step S111 are executed.

[0056] According to the optical transmission system 100a configured as above, it is possible to obtain the same effects as those of the first embodiment.

[0057] When the optical transmitter 10 transmits the first and second main signals over different lines as in the first embodiment, any discrepancy in the transmission timing of the first and second main signals may affect delay measurement. In contrast, in the optical transmission system 100a, the optical transmitter 10a does not transmit main signals over multiple lines. This eliminates the need for the optical transmitter 10a to synchronize the transmission timing of the first and second main signals. As a result, the delay time can be calculated more accurately.

[0058] (Third embodiment) In the first and second embodiments, a configuration for measuring delay in one communication device to be subjected to delay measurement is described. In the third embodiment, a configuration for measuring delay in a plurality of communication devices to be subjected to delay measurement will be described.

[0059] 5 is a diagram showing the system configuration of an optical transmission system 100b according to the third embodiment. The optical transmission system 100b includes an optical sending device 10, multiple optical transmission devices 20-1 to 20-n (n is an integer equal to or greater than 3), and multiple delay measurement target communication devices 30-1 to 30-n. In the optical transmission system 100b, an optical receiving device 40 is provided inside some of the delay measurement target communication devices 30. This makes it possible to measure delays occurring in each delay measurement target communication device 30.

[0060] The optical sending device 10, the optical transmission device 20-1, and the delay measurement target communication device 30-1 shown in FIG. 5 have the same configurations as the devices with the same names in the first embodiment.

[0061] The second embodiment differs from the first embodiment in that the delay measurement target communication devices 30-(n-1) to 30-n each include an optical receiving device 40-(n-1) to 40-n, that the optical transmission device 20-(n-1) includes a branching unit 21 as in the second embodiment, and that the first main signal and the second main signal transmitted from the optical transmission device 20-(n-1) are input to the delay measurement target communication device 30-n. When the delay measurement target communication devices 30-(n-1) to 30-n each include an optical receiving device 40-(n-1) to 40-n, it is desirable to implement them as hardware in the delay measurement target communication devices 30-(n-1) to 30-n to ensure accuracy.

[0062] The optical receiving devices 40-(n-1) to 40-n have the same configuration as the devices with the same names in the first and second embodiments.

[0063] With the above configuration, the optical receiving device 40-(n-1) in the delay measurement target communication device 30-(n-1) can measure the delay that occurs in the preceding delay measurement target communication device 30 (delay measurement target communication device 30-1 in FIG. 5). The optical receiving device 40-n in the delay measurement target communication device 30-n) can measure the total delay that occurs in the delay measurement target communication devices 30-1 to 30-(n-1).

[0064] The process of the optical transmission system 100b in the third embodiment follows the following flow. The optical transmitting device 10 transmits a first main signal to the optical transmission device 20-1 via the line 51. The optical transmitting device 10 transmits a second main signal to the optical transmission device 20-1 via the line 52 at the same timing as the transmission of the first main signal.

[0065] The optical transmission device 20-1 transmits the first main signal received via the line 51 to the delay measurement target communication device 30-1. The optical transmission device 20-1 transmits the second main signal received via the line 52 to the optical transmission device 20-(n-1). The delay measurement target communication device 30-1 transmits the first main signal transmitted from the optical transmission device 20-1 again to the optical transmission device 20-1. The optical transmission device 20-1 transmits the first main signal transmitted from the delay measurement target communication device 30-1 to the optical transmission device 20-(n-1).

[0066] The optical transmission device 20-(n-1) transmits the first main signal transmitted from the optical transmission device 20-1 to the delay measurement target communication device 30-(n-1). Furthermore, the optical transmission device 20-(n-1) branches the second main signal transmitted from the optical transmission device 20-1 using the branching unit 21. The optical transmission device 20-(n-1) transmits the second main signal branched by the branching unit 21 to the delay measurement target communication device 30-(n-1) and the optical transmission device 20-n.

[0067] The delay measurement target communication device 30-(n-1) transmits the first main signal transmitted from the optical transmission device 20-(n-1) again to the optical transmission device 20-(n-1). The optical transmission device 20-(n-1) transmits the first main signal transmitted from the delay measurement target communication device 30-(n-1) to the optical transmission device 20-n.

[0068] Furthermore, the optical receiving device 40-(n-1) of the delay measurement target communication device 30-(n-1) measures the delay occurring in the delay measurement target communication device 30-1 using the input first main signal and second main signal.

[0069] The optical transmission device 20-n transmits the first main signal transmitted from the optical transmission device 20-(n-1) to the delay measurement target communication device 30-n. Furthermore, the optical transmission device 20-n transmits the second main signal transmitted from the optical transmission device 20-(n-1) to the delay measurement target communication device 30-n.

[0070] The delay measurement target communication device 30-n transmits the first main signal transmitted from the optical transmission device 20-n again to the optical transmission device 20-n. The optical transmission device 20-n transmits the first main signal transmitted from the delay measurement target communication device 30-n to the outside.

[0071] Furthermore, the optical receiving device 40-n of the delay measurement target communication device 30-n measures the delay occurring from the delay measurement target communication device 30-1 to the delay measurement target communication device 30-(n-1) using the input first main signal and second main signal.

[0072] The optical transmission system 100b configured as above can be applied even when there are multiple communication devices that are targets for delay measurement.

[0073] A modification of the optical transmission system 100b in the third embodiment will be described below. In cases where wavelength conversion is performed when dropping and adding signals from the optical transmission device 20 to the delay measurement target communication device 30, or when separate physical ports are provided for the first main signal transfer unit 11 and the second main signal transfer unit 12 in the optical sending device 10, and where signal collisions do not occur on the lines 51 and 52, the optical sending device 10 may be configured to transmit the first main signal and the second main signal at the same wavelength. In this case, separate physical ports are provided for the main signal transfer unit 41 and the reception processing unit 42 in the optical receiving device 40 as well. With this configuration, although the number of required physical ports increases, it is possible to suppress an increase in the transmission band.

[0074] In the above embodiment, an example has been shown in which the optical receiving devices 40-(n-1) to 40-n are implemented as hardware components in the delay measurement target communications devices 30-(n-1) to 30-n. The optical receiving devices 40-(n-1) to 40-n may also be implemented as software running on a processor such as a CPU (Central Processing Unit). The configuration in this case is shown in FIG. 6. FIG. 6 is a diagram showing the configuration of the delay measurement target communications devices 30-(n-1) to 30-n when the optical receiving devices are implemented as software running on a processor. The delay measurement target communications devices 30-(n-1) to 30-n include a signal receiving unit 31 and optical receiving devices 40-(n-1) to 40-n.

[0075] The signal receiving unit 31 receives a main signal transmitted from the optical transmission devices 20-(n-1) to 20-n. The signal receiving unit 31 outputs the received main signal to the optical receiving devices 40-(n-1) to 40-n. The signal receiving unit 31 is, for example, a network interface card (NIC). The signal receiving unit 31 includes an internal buffer 32. The internal buffer 32 holds a first main signal (a main signal transmitted through the communication device 30 that is the target of delay measurement).

[0076] When the signal receiving unit 31 receives a second main signal (a main signal that does not pass through the delay measurement target communication device 30), it notifies the optical receiving devices 40-(n-1) to 40-n of the reception of the main signal with the highest priority by issuing an interrupt or the like. Then, the reception processing unit 42 in the optical receiving devices 40-(n-1) to 40-n records the time of receiving the notification as reception time t1. Meanwhile, the first main signal (a main signal that passes through the delay measurement target communication device 30) is held in the internal buffer 32 in the signal receiving unit 31. The optical receiving devices 40-(n-1) to 40-n record the time of receiving the first main signal from the internal buffer 32 as reception time t2. The reception processing unit 42 calculates the delay time using the reception time t1 and the reception time t2. The delay time includes a queuing delay in the internal buffer 32.

[0077] In the above embodiment, the optical transmission device 10 in the first embodiment has been described as an example of the optical transmission device 10. In the third embodiment, the optical transmission device 10a in the second embodiment may be used as the optical transmission device 10. In this configuration, the optical transmission device 20-1 has the same configuration as the optical transmission device 20a in the second embodiment.

[0078] (Fourth embodiment) In the first to third embodiments, the configurations in which the main signal input to the optical transmitting device is an optical signal are shown. In the fourth embodiment, a configuration in which the main signal input to the optical transmitting device is an electrical signal will be described.

[0079] 7 is a diagram illustrating a system configuration of an optical transmission system 100c according to the fourth embodiment. The optical transmission system 100c includes an optical transmitting device 10c, an optical transmitting device 20, a delay measurement target communication device 30, and an optical receiving device 40c. The optical transmitting device 10c and the optical transmitting device 20, the optical transmitting device 20 and the delay measurement target communication device 30, and the optical transmitting device 20 and the optical receiving device 40c are connected via optical transmission paths.

[0080] An optical transmission system 100c in the fourth embodiment differs from the optical transmission system 100 in the first embodiment in the configurations of an optical transmitter 10c and an optical receiver 40c. Therefore, the differences from the first embodiment will be described below.

[0081] When the optical transmitting device 10c receives a main signal from an adjacent network or device such as a server, it transmits the received main signal to the optical transmission device 20 via lines 51 and 52, which serve as optical transmission paths. In the fourth embodiment, an electrical main signal is input to the optical transmitting device 10c. The lines 51 and 52 may be physically provided within the same fiber, or may be provided within separate, independent fibers. When the lines 51 and 52 are physically provided within the same fiber, a method of wavelength-multiplexing the main signal transmitted from the optical transmitting device 10 and transmitting it at different wavelengths is considered. In the fourth embodiment, a case where the lines 51 and 52 are physically provided within the same fiber will be described as an example.

[0082] The optical receiving device 40c measures the processing delay in the delay measurement target communication device 30 using multiple main signals transmitted from the optical transmission device 20. For example, the optical receiving device 40c measures the processing delay in the delay measurement target communication device 30 by calculating the difference between the reception time of the first main signal and the reception time of the second main signal. The optical receiving device 40c in the fourth embodiment converts the received optical signals, the first main signal and the second main signal, into electrical signals and compares the first main signal with the second main signal.

[0083] Next, the specific configurations of the functional units of the optical transmitting device 10c and the optical receiving device 40c will be described. The optical transmitting device 10c includes a first main signal transfer unit 11c and a second main signal transfer unit 12c. The first main signal transfer unit 11c transmits a first main signal to the optical transmission device 20. The first main signal transfer unit 11c includes a main signal receiving unit 111c, a buffer 114, an E / O conversion unit 115, a branching unit 112, and a transmission unit 113.

[0084] The main signal receiver 111c receives an electrical main signal from an adjacent network or a device such as a server. The main signal receiver 111c stores the main signal in a buffer 114. The main signal receiver 111c notifies the second main signal transfer unit 12c of the timing of sending the main signal when the main signal is stored in the buffer 114. This allows the optical receiving device 40c to measure delay times, including queuing delays in the buffer 114 and electrical-to-optical conversion delays in the E / O converter 115, within the first main signal transfer unit 11c. If the main signal is a packet, the main signal receiver 111c assigns a Virtual Local Area Network (VLAN) tag to the packet for matching purposes in the optical receiving device 40c. The VLAN tag maintains its uniqueness by counting up the tag or calculating a hash value of the packet each time a combination of the first and second main signals is transmitted.

[0085] In addition, when it is desired to measure the delay occurring in the communication device 30 to be measured without including the queuing delay of the buffer 114 inside the first main signal transfer unit 11c and the electrical-to-optical conversion delay in the E / O conversion unit 115, the sending unit 113 may notify the second main signal transfer unit 12c of the transmission timing of the first main signal before transmitting the first main signal, as in the first embodiment.

[0086] The buffer 114 is a storage unit that holds the main signals for electrical processing. The buffer 114 stores one or more main signals.

[0087] The E / O conversion unit 115 converts the main electrical signal held in the buffer 114 into an optical signal by electro-optic conversion.

[0088] The optical receiving device 40c includes a main signal transfer unit 41 and a reception processing unit 42c. The reception processing unit 42c processes the main signal received by the optical receiving device 40c. The reception processing unit 42c includes an optical signal receiving unit 421, an O / E conversion unit 424, a matching unit 422c, and a delay measurement unit 423.

[0089] The O / E conversion unit 424 performs optical-electrical conversion on the first main signal of the optical signal output from the main signal transfer unit 41 and the second main signal of the optical signal output from the optical signal receiving unit 421, converting them into electrical signals.

[0090] The collating unit 422c uses the first and second main signals converted into electrical signals to check whether the first and second main signals received by the optical receiving device 40c are main signals with the same data.

[0091] Fig. 8 is a sequence diagram showing the flow of processing in the optical transmission system 100c in the fourth embodiment. In Fig. 8, the same processes as those in Fig. 2 are denoted by the same reference numerals as those in Fig. 2, and the description thereof will be omitted. The main signal receiving unit 111c receives a main signal (electrical signal) from the outside (step S301). The main signal receiving unit 111c stores the received main signal in the buffer 114. At this time, the main signal receiving unit 111c notifies the second main signal transfer unit 12c of the timing of sending the main signal (step S302).

[0092] The E / O conversion unit 115 reads out the main signal stored in the buffer 114 and performs electrical-to-optical conversion (step S303). As a result, the main signal is converted into an optical signal. The E / O conversion unit 115 outputs the main signal after electrical-to-optical conversion to the branching unit 112. The main signal output from the E / O conversion unit 115 is branched by the branching unit 112 (step S304) and input to the sending unit 113 and the second main signal transfer unit 12c.

[0093] Thereafter, the processes from step S104 to step S109 are executed. The O / E converter 424 performs optical-electrical conversion on the first main signal output from the main signal transfer unit 41 and the second main signal received by the optical signal receiver 421 (step S305). As a result, the first main signal and the second main signal are converted into electrical signals. The O / E converter 424 outputs the optical-electrically converted first main signal and second main signal to the matching unit 422c.

[0094] The matching unit 422c uses the first and second main signals after photoelectric conversion output from the main signal transfer unit 41 to check whether the first and second main signals received by the optical receiving device 40c are main signals with the same data (step S306). Specifically, the matching unit 422c compares the VLAN tags attached to the first and second main signals. If the VLAN tags attached to the first and second main signals match, the matching unit 422c determines that the first and second main signals after photoelectric conversion are main signals sent at the same time. On the other hand, if the VLAN tags attached to the first and second main signals do not match, the matching unit 422c determines that the first and second main signals after photoelectric conversion are not main signals sent at the same time.

[0095] Here, it is assumed that the first and second main signals after photoelectric conversion match. The collation unit 422 outputs the first reception time information of the first main signal and the second reception time information of the second main signal that match to the delay measurement unit 423. The delay measurement unit 423 measures the delay occurring in the delay measurement target communication device 30 using the first reception time information and second reception time information output from the collation unit 422 (step S307). Specifically, the delay measurement unit 423 calculates the delay time occurring in the delay measurement target communication device 30 by subtracting the time indicated by the first reception time information from the time indicated by the second reception time information.

[0096] According to the optical transmission system 100c configured as above, it is possible to obtain the same effects as those of the first embodiment.

[0097] Furthermore, in the optical transmission system 100c, even if the main signal is an electrical signal, it is possible to measure the delay occurring in the delay measurement target communication device 30.

[0098] A modification of the optical transmission system 100c in the fourth embodiment will be described below. When wavelength conversion is performed when dropping and adding signals from the optical transmission device 20 to the delay measurement target communication device 30, or when separate physical ports are provided for the first main signal transfer unit 11c and the second main signal transfer unit 12c in the optical sending device 10c, and when signal collisions do not occur on the lines 51 and 52, the optical sending device 10c may be configured to transmit the first main signal and the second main signal at the same wavelength. In this case, separate physical ports are provided for the main signal transfer unit 41 and the reception processing unit 42c in the optical receiving device 40c as well. With this configuration, although the number of required physical ports increases, it is possible to suppress an increase in the transmission band.

[0099] In the above embodiment, a configuration in which the main signal input to the optical transmitting device in the configuration of the first embodiment is an electrical signal has been described. The configuration in which the main signal is an electrical signal as in the fourth embodiment can also be applied to the second and third embodiments. Hereinafter, a configuration in which the main signal input to the optical transmitting device in the second embodiment is an electrical signal will be described.

[0100] In the second embodiment, a case where a main signal input to an optical transmitter 10a is an electrical signal will be described. A main signal transfer unit 11a of the optical transmitter 10a includes a buffer 114 and an E / O converter 115 between a main signal receiver 111 and a transmitter 113a.

[0101] The main signal receiving unit 111 receives an electrical main signal from an adjacent network or a device such as a server. The main signal receiving unit 111 stores the main signal in a buffer 114. The E / O converting unit 115 converts the electrical main signal stored in the buffer 114 from electrical to optical to an optical signal. The sending unit 113a sends the main signal converted into an optical signal by the E / O converting unit 115 to the line 51.

[0102] The optical receiving device 40 has the same configuration as the optical receiving device 40c in the fourth embodiment.

[0103] Some of the functional units of the optical transmitter 10, optical transmission device 20, delay measurement target communication device 30, and optical receiver 40 in the above-described embodiments may be implemented by a computer. In this case, a program for implementing these functions may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed. Note that the term "computer system" herein includes hardware such as an OS and peripheral devices. Furthermore, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into a computer system. Furthermore, the term "computer-readable recording medium" may also include devices that dynamically store programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or telephone lines, or devices that store programs for a fixed period of time, such as volatile memory within a computer system serving as a server or client. The program may be designed to implement some of the above-described functions, or may be capable of implementing the above-described functions in combination with a program already stored in the computer system, or may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0104] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention. [Industrial Applicability]

[0105] The present invention can be applied to a technique for measuring delay in an optical transmission system. [Explanation of symbols]

[0106] 10, 10a, 10c...optical transmitting device, 11...first main signal transfer unit, 11a...main signal transfer unit, 12, 12c...second main signal transfer unit, 20, 20-1 to 20-n, 20a...optical transmission device, 21...branching unit, 30, 30-1 to 30-n...delay measurement target communication device, 40, 40-1 to 40-n, 40c...optical receiving device, 41...main signal transfer unit, 42, 42c...reception processing unit, 111...main signal receiving unit, 112...branching unit, 113, 113a...transmission unit, 114...buffer, 115...E / O conversion unit, 411...main signal receiving unit, 412...transmission unit, 421...optical signal receiving unit, 422...collation unit, 423...delay measurement unit, 424...O / E conversion section

Claims

1. An optical transmission system comprising an optical transmitting device, an optical receiving device, a communication device to be measured for delay, and a transmission device for transmitting signals between the optical receiving device and the communication device, The optical transmitter comprises: a main signal transfer unit that transmits a main signal; the transmission device transmits to the optical receiving device a first main signal that is sent from the optical transmitting device and passes through the communication device, and a second main signal that is sent from the optical transmitting device and does not pass through the communication device; The optical receiving device a reception processing unit that measures a delay occurring in the communication device using the first main signal and the second main signal transmitted from the transmission device; Equipped with The receiving processing unit measures a delay caused by the communication device performing predetermined signal processing on the main signal sent from the optical transmitting device and transmitted by the transmission device, and then transmitting the processed main signal to the transmission device as the first main signal.

2. the main signal transfer unit included in the optical transmission device is composed of a first main signal transfer unit and a second main signal transfer unit, the first main signal transfer unit branches the main signal, outputs the branched main signal to the second main signal transfer unit, and then sends out the main signal; the second main signal transfer unit transmits the main signal in accordance with the transmission timing of the first main signal transfer unit; the transmission device transmits the first main signal, which is the main signal sent from the first main signal transfer unit, to the communication device, and transmits the second main signal, which is the main signal sent from the second main signal transfer unit, to the optical receiving device; 2. The optical transmission system according to claim 1.

3. the transmission device includes a branching unit that branches the main signal sent from the optical transmitting device, and transmits the main signal branched by the branching unit to the communication device and the optical receiving device as the first main signal and the second main signal.

2. The optical transmission system according to claim 1.

4. The number of the transmission device, the communication device, and the optical receiving device is n (n is an integer of 3 or more), each of the (n-1)th to nth transmission devices is provided with the optical receiving device; the (n-1)th transmission device includes a branching unit that branches a main signal transmitted from a preceding transmission device, and transmits to the connected communication device the first main signal, which is a main signal transmitted via at least one communication device, and the second main signal, which is a main signal branched by the branching unit and transmitted without via a communication device; the n-th transmission device transmits the first main signal and the second main signal to a communication device connected thereto; 4. The optical transmission system according to claim 1.

5. the reception processing unit of the optical receiving device converts the first main signal and the second main signal into electrical signals, compares the identification information provided by the optical transmitting device or the electrical signals, and if the identification information or the electrical signals match, determines that the first main signal and the second main signal are main signals of the same data, and measures a delay occurring in the communication device using the first main signal and the second main signal of the same data.

5. An optical transmission system according to claim 1.

6. the reception processing unit of the optical receiving device measures the delay occurring in the communication device by calculating a difference between a reception time of the first main signal and a reception time of the second main signal.

6. An optical transmission system according to claim 1.

7. An optical receiving device in an optical transmission system including an optical transmitting device, an optical receiving device, a communication device to be measured for delay, and a transmission device that transmits signals between the optical receiving device and the communication device, a reception processing unit that measures a delay occurring in the communication device using a first main signal that is sent from the optical transmitting device and transmitted at least via the communication device, and a second main signal that is sent from the optical transmitting device and transmitted without passing through the communication device; Equipped with The receiving processing unit is an optical receiving device that measures the delay caused by the communication device performing predetermined signal processing on a main signal sent from the optical transmitting device and transmitted by the transmission device, and then transmitting the processed main signal to the transmission device as the first main signal.

8. A delay measurement method in an optical transmission system including an optical transmitting device, an optical receiving device, a communication device to be subjected to delay measurement, and a transmission device that transmits signals between the optical receiving device and the communication device, comprising: The optical transmitter transmits a main signal, the transmission device transmits to the optical receiving device a first main signal that is sent from the optical transmitting device and passes through the communication device, and a second main signal that is sent from the optical transmitting device and does not pass through the communication device; the optical receiving device measures a delay occurring in the communication device using the first main signal and the second main signal transmitted from the transmission device; the optical receiving device measures a delay caused by the communication device performing predetermined signal processing on the main signal transmitted from the optical transmitting device and transmitted by the transmission device, and then transmitting the processed main signal to the transmission device as the first main signal; Latency measurement method.

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