Fiber inspection device and fiber inspection method

Abstract

A fiber inspection device 1 comprises: a switch control unit 11 that controls a connection state of an input / output port of a switch 100; a terminal control unit 12 that controls a terminal 200, inputs an optical signal from the terminal 200 to a fiber that is connected to the terminal 200, and measures the received light intensity of the optical signal received from the fiber; and an inspection unit 13 that classifies a state of the fiber on the basis of the received light intensity. The fiber inspection device 1 transmits / receives the optical signal by the terminal 200 while changing grouping of input / output ports that are loopback-connected and input / output ports that are internally unconnected, and specifies a connection relationship between the terminal 200 and the input / output ports on the basis of a result of reception of the optical signal by the terminal 200 in each trial.

Description

Fiber inspection device and fiber inspection method

[0001] This disclosure relates to a fiber inspection apparatus and a fiber inspection method.

[0002] In recent years, the introduction of optical switches has been progressing to increase bandwidth, reduce latency, and lower power consumption in data center networks. Optical switches can switch signals from terminals within the data center (top-of-rack switches and transceivers inserted into servers) without electrical conversion, and have the following characteristics: they are independent of signal format and rate, do not cause buffer delays that occur with conventional electrical switches (packet switches), and consume very little power.

[0003] Kazuya Anazawa, Takeru Inoue, Toru Mano, Hideki Nishizawa, Eiji Oki, "Efficient fiber-inspection and certification method for optical-circuit-switched datacenter networks," Journal of Optical Communications and Networking, August 2024, Vol. 16, No. 8, pp. 788 - 799Kazuya Anazawa, Takeru Inoue, Toru Mano, Wataru Ishida, Kazuaki Obana, Hideki Nishizawa, "Efficient Fiber-Inspection Method for Optical-Circuit Datacenter Networks," IEEE Globecom 2023

[0004] However, as mentioned above, optical switches only switch signals and cannot send or receive packets like conventional electrical switches, making it difficult to easily inspect the quality of the fiber connecting the terminal and the optical switch, as well as the wiring condition.

[0005] On the other hand, optical fibers are susceptible to damage during construction and can be miswired. In fact, a certain number of fibers with abnormal loss or miswired exist within data centers. This can lead to unexpected network outages or network failures.

[0006] Therefore, after the construction of the optical switch network, a mechanism is needed to correctly identify the quality and wiring condition of the fibers connecting the terminals and optical switches.

[0007] This disclosure is made in view of the above and aims to automatically and quickly identify the state of the optical fiber connecting the terminal and the optical switch.

[0008] A fiber inspection device according to one aspect of the present disclosure is a fiber inspection device for inspecting the state of a fiber connecting at least one terminal and at least one switch, comprising: a switch control unit that controls the connection state of the input / output ports of the switch; a terminal control unit that controls the terminal and inputs an optical signal from the terminal to a fiber connected to the terminal and measures the received intensity of the optical signal received from the fiber; and an inspection unit that classifies the state of the fiber based on the received intensity, and measures the received intensity at the terminal while changing the grouping of input / output ports that are loopback connected and input / output ports that are not internally connected, and identifies the connection relationship between the terminal and the input / output ports based on the received intensity at the terminal in each trial.

[0009] According to this disclosure, the status of the optical fiber connecting the terminal and the optical switch can be automatically and quickly identified.

[0010] Figure 1 shows an example of a network model targeted for inspection by the fiber inspection device. Figure 2 shows an example of the connection status between input / output ports of an optical switch. Figure 3 shows an example of a path for fiber inspection. Figure 4 shows an example of a path during operation. Figure 5 shows an example of the configuration of the fiber inspection device. Figure 6 is a flowchart showing an example of the processing flow of the fiber inspection device. Figure 7 is a flowchart showing an example of the processing flow for identifying the connection relationship between terminals and input / output ports. Figure 8 shows an example of a path for classifying suspected fibers. Figure 9 shows a network model assumed in the embodiment. Figure 10 shows all input / output ports of the optical switch connected via loopback. Figure 11 shows the input / output ports of the optical switch divided into two groups, with one of them connected via loopback. Figure 12 shows the input / output ports of the optical switch divided into two groups, with one of them connected via loopback. Figure 13 shows the input / output ports of the optical switch divided into two groups, with one of them connected via loopback. Figure 14 shows the input / output ports of the optical switch divided into two groups, with one of them connected via loopback. Figure 15 shows the input / output ports connected to each other to classify suspected fibers. Figure 16 shows the relationship between the number of fibers to be inspected and the inspection completion time for the proposed method and the naive method. Figure 17 shows the relationship between the time required for one inspection and the inspection completion time for the proposed method and the naive method. Figure 18 shows an example of the hardware configuration of the fiber inspection device.

[0011] [Network Model] Referring to Figure 1, the network model to be inspected by the fiber inspection device of this embodiment will be described. In this embodiment, the target of inspection is an optical switch network consisting of k N×N optical switches 100 and m terminals 200 connected to them. An N×N optical switch 100 (hereinafter referred to as optical switch 100) is an optical switch having N input ports (Rx) and N output ports (Tx). Each port of the optical switch 100 is configured as Tx / Rx and is connected to each terminal 200 by a 2-core pair fiber. The terminals 200 are, for example, SFP transceivers mounted on servers or ToR / Aggr switches. In data centers, transceivers of types such as DR (budget 3.0dB) and FR (budget 4.0-7.0dB) are commonly used.

[0012] Let Q = {1, ..., kN} represent the set of all input / output ports of k optical switches 100, and T = {1, ..., m} represent the set of terminals 200, where m ≤ kN. Let F be the set of two-core pairs of fiber connecting the terminals 200 and the optical switches 100. Each fiber f ∈ F consists of two links: an uplink from terminal 200 to optical switch 100 and a downlink from optical switch 100 to terminal 200. Let E be the set of links. Hereafter, terminal i ∈ T represents terminal 200 number i, and input / output port j ∈ Q represents input / output port number j.

[0013] A logical variable f indicates whether or not a fiber is connected between terminal i and input / output port j. ij Let's assume that terminal i and input / output port j are connected by fiber optic cable. ij = 1, f if not connected. ij = 0. g is a logical variable that indicates whether the fiber connected to terminal i is usable or not. i If the fiber is unavailable, then g i =1, g if usable i = 0. The purpose of the fiber inspection device is f ij ,g iis to correctly obtain. That is, the fiber inspection device obtains the connection relationship between the terminal i and the input / output port j and the quality of the fiber connected to the terminal i. The connection relationship between the terminal i and the input / output port j and the quality of the fiber connected to the terminal i are also referred to as the state of the fiber.

[0014] As shown in FIG. 2, the optical switch 100 can internally connect any input / output ports (referred to as terminal connection) and internally connect the Tx port and the Rx port of the same input / output port (referred to as loopback connection). It can also not internally connect the input / output ports (referred to as non-internal connection). The terminals 200 connected to each of the input / output ports connected by terminal connection can transmit and receive optical signals between the terminals 200. The terminal 200 connected to the input / output port connected by loopback connection can receive the optical signal it has sent. A set of input / output ports connected by loopback connection is represented as Q l and.

[0015] The internal connection of the optical switch 100 can be controlled by a protocol such as NETCONF or RESTCONF. The time required for control is at most about 1.0 second. It is assumed that the change of the internal connection of the optical switch 100 is always correctly controlled. Also, the statistical value of the insertion loss for each pair of input / output ports of the optical switch 100 is assumed to be known.

[0016] The inspection of the fiber is performed by the terminal 200 transmitting and receiving optical signals. The terminal 200 is equipped with a Digital Optical Monitoring (DOM) / Digital Diagnostic Monitoring (DDM) function and is assumed to be able to measure the intensity of the optical signal in the O band (1310 nm). The optical signal intensity can be measured regardless of the type and generation of the transceiver.

[0017] Terminal 200 and optical switch 100 are connected by a two-core pair of fixed fibers, one for transmission and one for reception, with each fiber labeled Tx / Rx. Therefore, the Tx ports of terminal 200 and optical switch 100 will not be connected to each other, nor will the Rx ports of terminal 200 and optical switch 100 be connected to each other. Both Tx / Rx ports of the input / output ports of optical switch 100 will be connected to the same terminal 200. Furthermore, with appropriate floor planning and fiber management, connections between optical switches and terminals can be avoided, and the input / output ports of optical switch 100 and terminals 200 will not be connected to each other.

[0018] These assumptions ensure that the optical signal for fiber inspection in this embodiment passes through at most one optical switch 100 and at most two fibers.

[0019] [Signal Propagation Model] A path q is created in which terminal 200 transmits and receives optical signals, as shown in Figure 3. Terminal 200 transmits an optical signal with transmission intensity P0, receives the reflected optical signal at the optical switch 100, and the received optical signal has a reception intensity P q Measure the set of optical switches 100 on path q. q , the set of links E q In this embodiment, |S q |=1,|E q |=2. Optical switch s∈S on path q. q The loss due to (known) is L s,q , link e∈E q The loss (unknown) is denoted as L(e). In Figure 3, the loss of uplink e is denoted as L(e), and the loss of downlink e' is denoted as L(e').

[0020] When an optical signal with transmission intensity P0 passes through path q and is received by terminal 200, the received light intensity P q It can be expressed by the following equation.

[0021]

[0022] From the above formula, the light received by path q is P q When this happens, each link e∈E q The loss value is L(e) = P0 - P q -Ls,q -L min It can be estimated that L min This is the minimum loss that each link will have. More precisely, L(e) = P0 - P q -L s,q -(|E q |-1)L min However, |E q Since |-1=1, L(e)=P0-P q -L s,q -L min That's what I decided.

[0023] Therefore, each link e∈E q The maximum loss L that can be taken e,q max This can be estimated as follows:

[0024]

[0025] Minimum loss L min Since it is not possible to estimate this precisely, a sufficiently small value is set. The accuracy of the inspection will improve if a value close to the actual value is set. At this point, the uplink and downlink loss values ​​cannot be determined, but no matter how large it is, the maximum value L e,q max It can be seen that it does not exceed. Note that the link is a multiple path (q1, q2, ..., q n When tested using ), the maximum loss L that the link can take is... e max It can be expressed by the following equation.

[0026]

[0027] As shown in Figure 4, any operational path q' must pass through the optical switch 100 once, through the uplink e and downlink e', and therefore must satisfy the following equation: P b This is the budget for the transceivers used in operation.

[0028]

[0029] In other words, for communication to always be possible between terminals 200, the maximum loss L of each link is required. e max L must satisfy the following equation. s maxThis is the maximum insertion loss of the optical switch 100.

[0030]

[0031] The right-hand side of the above equation is called the allowable loss Lok, and the maximum loss L that the link can take is called e max It detects fibers with a loss greater than or equal to the allowable loss Lok as abnormal fibers. As mentioned above, the maximum loss L e max P0 is the transmission intensity of the optical signal, and P0 is the reception intensity of the optical signal. q , insertion loss L of the optical switch s,q , and minimum loss L min If we know the transmission strength P0 and insertion loss L, we can estimate it. s,q , and minimum loss L min Since this is known, the light signal reception intensity P at terminal 200 is q If you measure the maximum loss L e max By estimating this, the quality of the fiber can be classified. The transmission intensity P0 of the optical signal may also be measured at terminal 200.

[0032] [Configuration of Fiber Inspection Device] An example of the configuration of the fiber inspection device 1 will be described with reference to Figure 5. The fiber inspection device 1 shown in Figure 5 comprises a switch control unit 11, a terminal control unit 12, an inspection unit 13, and a holding unit 14.

[0033] The switch control unit 11 controls the connection status of the input / output ports of the optical switch 100. For example, the switch control unit 11 can loopback, connect terminals, or leave any input / output port of the optical switch 100 unconnected.

[0034] The terminal control unit 12 controls each terminal 200 to input an optical signal from the terminal 200 into the fiber, receive an optical signal from the fiber, and measure the received light intensity of the optical signal.

[0035] The inspection unit 13 identifies the quality of the fiber and the connection relationship between the input / output ports of the optical switch 100 and the terminal 200 based on the received light intensity of the optical signal received by the terminal 200. Specifically, the inspection unit 13 sends an optical signal from each terminal 200 with all input / output ports connected in a loopback configuration, measures the received light intensity of the received optical signal, and extracts abnormal fibers. The inspection unit 13 changes the grouping of input / output ports connected in a loopback configuration and input / output ports that are not internally connected, sends an optical signal from each terminal 200, measures the received light intensity of the received optical signal, and identifies the connection relationship between the input / output ports and the terminal 200 based on the received light intensity at each terminal 200 in each trial. The inspection unit 13 connects a terminal 200 connected to a normal fiber and a terminal 200 connected to a suspected fiber suspected of being of degraded quality, sends an optical signal from each terminal 200, measures the received light intensity of the received optical signal, and inspects the quality of the suspected fiber.

[0036] The holding unit 14 holds information for each optical switch 100 and information for each terminal 200. For example, the holding unit 14 holds the insertion loss L for each input / output port. s,q Transceiver Budget P b , the assumed minimum loss L min It holds things like these.

[0037] [Processing of the Fiber Inspection Device] An example of the processing flow of the fiber inspection device 1 will be explained with reference to the flowchart in Figure 6. The processing in Figure 6 may be performed simultaneously for all optical switches 100 and all terminals 200, or it may be performed for each optical switch 100. When performing the processing for each optical switch 100, the terminals 200 that should be connected to the optical switch 100 to be tested are used.

[0038] In step S1, the fiber inspection device 1 loopback-connects all input and output ports of the optical switch 100, transmits optical signals from each terminal 200, receives the optical signals folded back by the optical switch 100, measures the received light intensity, and classifies the fibers connected to each terminal 200 based on the received light intensity.

[0039] When all input / output ports of the optical switch 100 are connected via loopback, optical signals from any terminal 200 will not be received by another terminal 200. Furthermore, optical signals from any terminal 200 will not pass through any fiber other than the fiber connected to that terminal 200. Since both the Tx / Rx ports of the input / output ports of the optical switch 100 are connected to the same terminal 200, optical signals from terminal i∈T pass through the fiber connected to terminal i∈T and arrive at the Rx side of input / output port j∈Q. The optical signals then arrive at the Tx side via the Rx side of input / output port j∈Q via the loopback connection, pass through the fiber connected to terminal i∈T, and are received by terminal i∈T.

[0040] Therefore, when all input / output ports of the optical switch 100 are connected via loopback, the received light intensity P of the optical signal received at any terminal i is... i P 2Lok =P0-L s,q If the value falls below -2Lok, the fiber connected to terminal i will have at least one of its uplink or downlink connections below the allowable loss Lok, and the fiber inspection device 1 will classify the fiber as an abnormal fiber that cannot be used in operation. Since abnormal fibers need to be replaced, there is no need to distinguish between quality degradation and failure, and there is no need to worry about the wiring condition.

[0041] The received light intensity P of the optical signal received by any terminal i. i P Lok =P0-L s,q -If the value exceeds Lok, neither the uplink nor the downlink of the fiber connected to terminal i will exceed the allowable loss Lok, so the fiber inspection device 1 classifies the fiber as a normal fiber.

[0042] The received light intensity P of the optical signal received by any terminal i. i P Lok Even in the following case, it cannot be said that at least one of the uplink or downlink of the fiber connected to terminal i falls below the allowable loss Lok, so the fiber inspection device 1 classifies the fiber as a suspected fiber. The suspected fiber will be classified as either a normal fiber or an abnormal fiber in step S3 described below.

[0043] A collection of terminals connected to a normal fiber T H A collection of terminals connected to the suspected fiber T Y , and a collection of terminals T connected to the abnormal fiber Z It can be expressed by the following equation.

[0044]

[0045] In step S1, only the abnormal fibers may be identified, and in step S2, the normal fibers and suspected fibers may be classified.

[0046] Terminal 200 connected to a fiber classified as abnormal in step S1 is excluded from inspection in step S2 and beyond.

[0047] Furthermore, since the loopback connection of the optical switch 100 and the measurement of the light reception intensity at each terminal 200 can be performed in a single step in step S1, the processing amount is O(1).

[0048] In step S2, the fiber inspection device 1 transmits and receives optical signals while changing the grouping of input / output ports that are loopback-connected and input / output ports that are not internally connected, and identifies the connection relationship between terminals and ports based on the optical signal reception results in each trial. For example, half of the input / output ports are set to be loopback-connected and the other half are set not to be internally connected, and optical signals are transmitted from each terminal 200. The optical switch 100 determines whether or not each terminal 200 has received the optical signal that has been looped back. A terminal 200 that has received an optical signal can be determined to be connected to one of the loopback-connected input / output ports and not to any input / output ports that are not internally connected, and a terminal 200 that has not received an optical signal can be determined to be not connected to any loopback-connected input / output ports and to be connected to one of the input / output ports that are not internally connected. By changing the group of input / output ports that are loopback-connected and the group of input / output ports that are not internally connected, and determining whether or not the optical signal that has been looped back by the optical switch 100 has been received, the input / output ports to which each terminal 200 is connected can be identified.

[0049] Q is a collection of loopback-connected input / output ports. lA collection of terminals T that are receiving optical signals. H ∪T Y The following proposition holds true for this:

[0050]

[0051] Assume that the negation of the above proposition is true. Terminal i ∈ T H ∪T Y The optical signal from terminal i∈T H ∪T Y The signal passes through the fiber connecting input / output port j ∈ Q and arrives at the Rx side of input / output port j. At this time, in order for the optical signal to be returned to terminal i, the Rx and Tx sides of input / output port j must be connected in a loopback manner, but input / output port j is set Q l Since this contradicts the fact that it is not included, the original proposition is correct.

[0052] In other words, if any terminal i is receiving its own optical signal, then terminal i ∈ T H ∪T Y It is impossible for it to be connected by fiber to an internally unconnected input / output port j that is not loopback-connected. It must be connected by fiber to one of the input / output ports that is loopback-connected.

[0053] By simultaneously testing different groups of input / output ports connected via loopback, the wiring configuration can be uniquely identified.

[0054] Referring to the flowchart in Figure 7, an example of the processing flow in step S2 will be explained. In the example in Figure 7, the input / output ports are classified into two groups, Xs and Ys, based on the state of the s-th bit (0 or 1) when the input / output port number is represented in binary. The s used for the first grouping is set to 1.

[0055] In step S21, the fiber inspection device 1 classifies input / output ports whose s-bit is 1 when their number is represented in binary into group Xs, and input / output ports whose s-bit is 0 into group Ys. In the initial grouping, input / output ports with a number where the first bit is 1 (i.e., odd-numbered ports) are classified into group Xs, and input / output ports with a number where the first bit is 0 (i.e., even-numbered ports) are classified into group Ys.

[0056] In step S22, the fiber inspection apparatus 1 controls the optical switch 100 so as to loop-back connect the input / output ports of group Xs and not to internally connect the input / output ports of group Ys.

[0057] In step S23, the fiber inspection apparatus 1 causes each terminal 200 to transmit an optical signal and measures the received light intensity of the optical signal. Based on the received light intensity measured here, normal fibers and suspected fibers may be classified.

[0058] In step S24, the fiber inspection apparatus 1 updates the connection relationship between the terminal 200 and the input / output port based on the presence or absence of reception of the optical signal at each terminal 200. For example, when s = 1, for the terminal i that received the optical signal in step S23, the logical variable f i1 ,f i3 ,f i5 ,... indicating the connection relationship between the terminal i and the input / output port of group Xs is set to 1, and the logical variable f i2 ,f i4 ,f i6 ,... indicating the connection relationship between the terminal i and the input / output port of group Ys is set to 0. Further, for the terminal j that did not receive the optical signal in step S23, the logical variable f j1 ,f j3 ,f j5 ,... indicating the connection relationship between the terminal j and the input / output port of group Xs may be set to 0. Note that the logical variable f ij that is already 0 is not updated to 1.

[0059] In step S25, the fiber inspection apparatus 1 controls the optical switch 100 to swap the connection states of group Xs and group Ys, not to internally connect the input / output ports of group Xs, and to loop-back connect the input / output ports of group Ys. Note that if the logical variable f j1 ,f j3 ,f j5 ,... indicating the connection relationship between the terminal j that did not receive the optical signal in step S24 and the input / output port of group Xs is set to 0, the processes of steps S25 to S27 may not be executed.

[0060] In step S26, the fiber inspection apparatus 1 causes each terminal 200 to transmit an optical signal and measures the received light intensity of the optical signal, as in step S23. Since the connection states of group Xs and group Ys are swapped, the terminals 200 that did not receive the optical signal in step S23 receive the optical signal in step S26.

[0061] In step S27, the fiber inspection apparatus 1 updates the connection relationship between the terminal 200 and the input / output port based on the presence or absence of reception of the optical signal at each terminal 200, as in step S24. For example, when s = 1, for the terminal i that received the optical signal in step S26, the logical variables f i1 ,f i3 ,f i5 ,... indicating the connection relationship between the terminal i and the input / output ports of group Xs are set to 0, and the logical variables f i2 ,f i4 ,f i6 ,... indicating the connection relationship between the terminal i and the input / output ports of group Ys are set to 1. Further, for the terminal j that did not receive the optical signal in step S26, the logical variables f j1 ,f j3 ,f j5 ,... indicating the connection relationship between the terminal j and the input / output ports of group Ys are set to 0.

[0062] The fiber inspection apparatus 1 increments s used for grouping by 1 and repeats the processing from step S21.

[0063] By executing the above processing, the connection relationship between terminal i and input / output port j can be specified.

[0064] In the processing of step S2, while incrementing s from 1 to log2|Q|, for each of group Xs and group Ys, the loop-back connection and the received light intensity at each terminal 200 are measured. The number of trials when both group Xs and group Ys are loop-back connected is 2log2|Q|. Also, the number of trials when only group Xs is loop-back connected is log2|Q|. In either case, the processing amount is O(log|Q|).

[0065] Returning to Figure 6, in step S3, the fiber inspection device 1 identifies the quality of all fibers classified as suspected fibers.

[0066] By the time of processing up to step S2, the terminal 200A connected to the normal fiber, the terminal 200B connected to the abnormal fiber, and the connection relationships between terminals 200A and 200B and the input / output ports are known. As shown in Figure 8, the fiber inspection device 1 sets the optical switch 100 to connect terminal 200A connected to the normal fiber and terminal 200B connected to the abnormal fiber, and causes terminal 200A to transmit an optical signal to terminal 200B and from terminal 200B to terminal 200A, and classifies the suspected fiber as either a normal fiber or an abnormal fiber based on the received signal strength of terminals 200A and 200B.

[0067] Light reception intensity P during inspection of a suspected fiber using a normal fiber q It can be expressed by the following equation.

[0068]

[0069] Here, L(e) is the loss of the normal fiber, and L(e') is the loss of the suspected fiber.

[0070] When the loss of the suspected fiber is less than or equal to the allowable loss Lok, that is, when the received signal strength P of either terminal 200A or 200B is less than or equal to the allowable loss Lok, q A suspected fiber is classified as an abnormal fiber when the following equation is satisfied.

[0071]

[0072] Since it is not possible to accurately determine the loss L(e) of a normal fiber, the minimum loss L of each fiber is... min Use L min A False Positive occurs when the discrepancy between and L(e) is large.

[0073] By connecting pairs of normal and suspected fibers, the light reception intensity at each terminal 200 can be measured simultaneously for multiple pairs. The process in step S3 can be performed in a constant number of trials if the number of suspected fibers is sufficiently small compared to the total number of fibers, so the processing time is effectively O(1).

[0074] [Example] An example of fiber inspection using the fiber inspection device 1 will be described with reference to Figures 9 to 15.

[0075] Figure 9 shows the network assumed in the embodiment. The optical switch 100 in Figure 9 has input / output ports 1 to 4, and terminal 200A (number 1) is connected to input / output port 1, terminal 200B (number 2) is connected to input / output port 2, terminal 200C (number 3) is connected to input / output port 4, and terminal 200D (number 4) is connected to input / output port 3. The fiber connected to terminal 200A has a loss near the allowable loss Lok and is detected as a suspected fiber, and the fiber connected to terminal 200B is faulty and is detected as an abnormal fiber. The fibers connected to terminals 200C and 200D are both normal fibers.

[0076] First, as shown in Figure 10, the fiber inspection device 1 loopback-connects all input and output ports of the optical switch 100, transmits optical signals from each terminal 200A to 200D, and measures the received light intensity of the optical signals received at each terminal 200A to 200D.

[0077] The light reception intensities P1 to P4 of terminals 200A to 200D are, respectively, P1 ≤ P Lok , P2 <P 2Lok , P3>P Lok , P4>P Lok The fiber inspection device 1 determined the terminal 200A based on the light reception intensity P1 to P4. Y , terminal 200B T Z , terminals 200C, 200D T H Classify into these categories.

[0078] Terminal 200B is T Z Since it was classified as such, it will be excluded from further processing. Fiber inspection device 1 is T Z For the fiber connected to terminal 200B, which is classified as such, we set g2=1.

[0079] Next, the fiber inspection device 1 identifies the connection relationships between terminals 200A, 200C, and 200D and the input / output ports.

[0080] The fiber inspection device 1 used s as the grouping parameter and classified the input / output ports into two groups, Xs={1,3} and Ys={2,4}.

[0081] As shown in Figure 11, the fiber inspection device 1 controlled the optical switch 100 to loopback the input / output ports of group Xs and to prevent the input / output ports of group Ys from being internally connected. Then, optical signals were transmitted from terminals 200A, 200C, and 200D, and the optical switch 100 checked whether or not it received the folded optical signals. In the example in Figure 11, terminals 200A and 200D received the folded optical signals.

[0082] Since terminals 200A and 200D have received optical signals, the fiber inspection device 1 sets a logical variable f that indicates the connection relationship between terminal 200A and the input / output ports of group Xs={1,3}. 11 ,f 13 And a logical variable f that indicates the connection relationship between terminal 200D and the input / output ports of group Xs={1,3}. 41 ,f 43 Let 1 be the logical variable f, which indicates the connection relationship between terminal 200A and the input / output ports of group Ys={2,4}. 12 ,f 14 And a logical variable f that indicates the connection relationship between terminal 200D and the input / output ports of group Ys={2,4}. 42 ,f 44 We set this to 0. Here, the logical variable f indicates the connection relationship between terminal 200C, which is not receiving an optical signal, and group Xs={1,3}. 31 ,f 33 You may set it to 0.

[0083] As shown in Figure 12, the fiber inspection device 1 controlled the optical switch 100 to swap the connection states of groups Xs and Ys, setting the input / output ports of group Xs to be disconnected internally and the input / output ports of group Ys to be loopback connected. Then, optical signals were transmitted from terminals 200A, 200C, and 200D, and the presence or absence of a folded optical signal was checked by the optical switch 100. In the example in Figure 12, terminal 200C received the folded optical signal.

[0084] Since terminal 200C has received an optical signal, the fiber inspection device 1 sets a logical variable f that indicates the connection relationship between terminal 200C and the input / output ports of group Ys={2,4}. 32 ,f 34 Let 1 be the logical variable f, which indicates the connection relationship between terminal 200C and the input / output ports of group Xs={1,3}. 31 ,f 33 We set it to 0.

[0085] Next, the fiber inspection device 1 used s for grouping as 2 and classified the input / output ports into two groups Xs={2,3} and Ys={1,4}.

[0086] As shown in Figure 13, the fiber inspection device 1 controlled the optical switch 100 to loopback the input / output ports of group Xs and to prevent the input / output ports of group Ys from being internally connected. Then, optical signals were transmitted from terminals 200A, 200C, and 200D, and the optical switch 100 checked for the presence or absence of folded optical signals. In the example in Figure 13, terminal 200D received the folded optical signal.

[0087] The fiber inspection device 1, upon receiving an optical signal from terminal 200D, sets a logical variable f that indicates the connection relationship between terminal 200D and the input / output ports of group Xs={2,3}. 42 ,f 43 Let f be 1, 42 Since the value of f is 0, 42 The value was left as =0. Furthermore, the fiber inspection device 1 uses a logical variable f that indicates the connection relationship between terminal 200D and the input / output ports of group Ys={1,4}. 41 ,f 44 We set it to 0.

[0088] At this stage, the logical variable f indicates the connection relationship between terminal 200D and each input / output port. 41 ,f 42 ,f 43 ,f 44 Among them, those with a value of 1 are f 43 With only that remaining, the connection between terminal 200D and input / output port 3 is confirmed.

[0089] As shown in Figure 14, the fiber inspection device 1 controlled the optical switch 100 to swap the connection states of groups Xs and Ys, setting the input / output ports of group Xs to be disconnected internally and the input / output ports of group Ys to be loopback connected. Then, optical signals were transmitted from terminals 200A, 200C, and 200D, and the presence or absence of folded optical signals was checked by the optical switch 100. In the example in Figure 14, terminals 200A and 200C received folded optical signals.

[0090] Since terminals 200A and 200C have received optical signals, the fiber inspection device 1 sets a logical variable f that indicates the connection relationship between terminal 200A and the input / output ports of group Ys={1,4}. 11 ,f 14 And a logical variable f that indicates the connection relationship between terminal 200C and the input / output ports of group Ys={1,4}. 31 ,f 34 Let f be 1, 14 and f 31 Since the value of f is 0, 14 =0,f 34 The value was left as =0. Furthermore, the fiber inspection device 1 uses a logical variable f that indicates the connection relationship between terminal 200A and the input / output ports of group Xs={2,3}. 12 ,f 13 And a logical variable f that indicates the connection relationship between terminal 200C and the input / output ports of group Xs={2,3}. 32 ,f 33 We set it to 0.

[0091] At this stage, the logical variable f indicates the connection relationship between terminal 200A and each input / output port. 11 ,f 12 ,f 13 ,f 14 Among them, those with a value of 1 are f 11 Since only this remains, the connection between terminal 200A and input / output port 1 is confirmed. Furthermore, the logical variable f indicates the connection relationship between terminal 200C and each input / output port. 31 ,f 32 ,f 33 ,f 34 Among them, those with a value of 1 are f 34 With only that remaining, the connection between terminal 200C and input / output port 4 is confirmed.

[0092] Through the above process, f 11 =1,f 34 =1,f 43 =1, meaning the connection relationship between terminals 200A, 200C, and 200D and the input / output ports has been determined.

[0093] Next, the fiber inspection device 1 identifies the quality of the suspected fiber.

[0094] As shown in Figure 15, the fiber inspection device 1 controls the optical switch 100 to connect terminal 1 and input / output port 3 to terminal 200A, which is connected to the suspected fiber, and terminal 200D (or terminal 200C), which is connected to the normal fiber, thereby causing optical signals to be transmitted from terminals 200A and 200D. The optical signal from terminal 200A is received by terminal 200D, and the optical signal from terminal 200D is received by terminal 200A.

[0095] The fiber inspection device 1 determines if the received light intensity P1 and P4 of the optical signals received at terminals 200A and 200D are both P Lok If the value is greater, the suspected fiber is classified as a normal fiber, and either the received light intensity P1 or P4 is P Lok If it falls below this value, the suspected fiber is classified as an abnormal fiber. In the example in Figure 15, the received light intensity P4 ≤ P of the optical signal received by terminal 200D. Lok Therefore, the suspected fiber connected to terminal 200A was classified as an abnormal fiber. In other words, terminal 200A was T Z It is classified as follows. Fiber inspection device 1 is T Z For the fiber connected to terminal 200A, which is classified as such, we set g1=1.

[0096] Through the above process, the fiber inspection device 1 is f 11 =1,f 34 =1,f 43 Output the result =1, g1=1, g2=1.

[0097] [Effectiveness of the Fiber Inspection Device] The proposed fiber inspection method was simulated for a network model assuming Google Jupiter. In Jupiter, there are 512 terminals in each Aggregation Block. Adding one Aggregation Block connects 512 new terminals to the optical switch network. Up to eight optical switches are mounted in dedicated racks. In Jupiter, there are up to 32 dedicated racks for optical switches. Each terminal on the Aggregation Block is fanouted equally to its respective dedicated optical switch rack.

[0098] Simulations were conducted by varying the number of optical switches (8) and the number of terminals connected to each optical switch (i.e., the number of test fibers) to 64, 128, 256, 512, and 1024. The number of quality abnormal uplinks and quality abnormal downlinks were set to the number of test fibers × 0.25. The insertion loss of the optical switches was set to [1.0, 2.0], and the standard deviation of the variation was set to 0.16. Transceiver Budget P b The DR was assumed to be 3dB. The fiber distance was assumed to be 0.5km, and the propagation loss coefficient was assumed to be 0.35dB / km. Fiber loss does not include patch panels or connectors. It was assumed that the optical switch could be controlled in a maximum of 1 second and the success or failure of signal transmission / reception could be confirmed in a maximum of 4 seconds, and the time required for one test was T. p The time interval was set to 5 seconds. The number of trials was set to 50.

[0099] Figure 16 shows the change in inspection completion time when simulating the proposed method and the naive method while varying the number of inspected fibers. The naive method inspects two fibers at a time, and suspected files are inspected in combination with normal fibers. The number of inspections is the number of inspected fibers (=kN) + ε, and the inspection completion time is (kN+ε)T p This is the result. ε is the number of suspected fibers.

[0100] When the number of fibers to be inspected was 512, the naive method took approximately 42 minutes to complete the inspection, while the proposed method completed it in approximately 1 minute and 35 seconds, which was about 26.9 times faster. When the number of fibers to be inspected was 1024, the naive method took approximately 1 hour and 25 minutes to complete the inspection, while the proposed method completed it in approximately 1 minute and 45 seconds, which was about 51.2 times faster.

[0101] Figure 17 shows the time T required for one test for the proposed method and the naive method. p This shows the change in inspection completion time when the time is varied from 5 to 30 seconds during simulation.

[0102] In all cases, the proposed method completed the inspection approximately 26.9 times faster than the naive method.

[0103] As described above, the fiber inspection device 1 includes a switch control unit 11 that controls the connection status of the input / output ports of the switch 100, a terminal control unit 12 that controls the terminal 200 and inputs an optical signal from the terminal 200 to the fiber connected to the terminal 200 and measures the received intensity of the optical signal received from the fiber, and an inspection unit 13 that classifies the state of the fiber based on the received intensity. The fiber inspection device 1 transmits and receives optical signals at the terminal 200 while changing the grouping of input / output ports that are loopback connected and input / output ports that are not internally connected, and identifies the connection relationship between the terminal 200 and the input / output ports based on the optical signal reception result at the terminal 200 in each trial. This makes it possible to automatically and quickly identify the state of the fiber connected to the terminal and the optical switch.

[0104] The fiber inspection device 1 divides the input / output ports into groups based on the value of each digit when the input / output port number is represented in binary, into groups of input / output ports that are loopback-connected and groups of input / output ports that are not internally connected. This makes it possible to identify the connection relationship between the terminal 200 and the input / output ports with a small number of trials.

[0105] The fiber inspection device 1 described above can use, for example, a general-purpose computer system as shown in Figure 18, which includes a central processing unit (CPU) 901, memory 902, storage 903, communication device 904, input device 905, and output device 906. In this computer system, the fiber inspection device 1 is realized when the CPU 901 executes a predetermined program loaded onto the memory 902. This program can be recorded on a computer-readable non-temporary recording medium such as a magnetic disk, optical disk, or semiconductor memory, or it can be distributed via a network.

[0106] 1 Fiber inspection device 11 Switch control unit 12 Terminal control unit 13 Inspection unit 14 Holding unit 100 Optical switch 200, 200A, 200B, 200C, 200D Terminal

Claims

1. A fiber inspection device for inspecting the state of a fiber connecting at least one terminal and at least one switch, comprising: a switch control unit that controls the connection state of the input / output ports of the switch; a terminal control unit that controls the terminal and inputs an optical signal from the terminal to a fiber connected to the terminal and measures the received intensity of the optical signal received from the fiber; and an inspection unit that classifies the state of the fiber based on the received intensity, wherein the terminal transmits and receives optical signals while changing the grouping of input / output ports that are loopback connected and input / output ports that are not internally connected, and identifies the connection relationship between the terminal and the input / output ports based on the optical signal reception result at the terminal in each trial.

2. A fiber inspection device according to claim 1, wherein all of the input / output ports are assigned input / output port numbers, and the input / output ports are divided into groups of loopback-connected input / output ports and groups of internally unconnected input / output ports according to the value of each digit when the input / output port number is represented in binary.

3. A fiber inspection apparatus according to claim 1, comprising: loopback connecting all input and output ports of the switch to measure the light intensity received at the terminal; classifying the fibers connected to the terminal into normal fibers, abnormal fibers, and suspected fibers based on the light intensity received; connecting a first terminal connected to normal fibers and a second terminal connected to suspected fibers via terminal-to-terminal connection in the switch; and classifying the suspected fibers into normal fibers or abnormal fibers based on the light intensity received between the first terminal and the second terminal.

4. A fiber inspection method using a fiber inspection device for inspecting the state of a fiber connecting at least one terminal and at least one switch, comprising: dividing the input / output ports of the switch into a group of input / output ports that are loopback connected and a group of input / output ports that are not internally connected; inputting an optical signal from the terminal to a fiber connected to the terminal; measuring the received intensity of the optical signal received from the fiber; transmitting and receiving optical signals at the terminal while changing the grouping of input / output ports that are loopback connected and input / output ports that are not internally connected; and identifying the connection relationship between the terminal and the input / output ports based on the optical signal reception results at the terminal in each trial.

Images