Optical track monitoring system, optical track monitoring device, and optical track monitoring method

Abstract

The present disclosure is an optical line monitoring system characterized by comprising: a plurality of optical couplers that each combine light from a first terminal and test light from a third terminal, output the resulting light to an optical line from a second terminal, and split back scattering light which is from the optical line and is to be inputted to the second terminal to the third terminal; 1×N (N is a positive integer) fiber selectors for switching and connecting the third terminal of one of the plurality of optical couplers to a switching source terminal; an optical time domain reflectometer (OTDR) that is connected to the switching source terminal of the 1×N fiber selectors, sends out test light to the third terminal of the optical coupler through the 1×N fiber selectors, and detects back scattering light from the third terminal of the optical coupler; a status analysis unit that extracts temporal change regarding back scattering light intensity and the distance from OTDR, and determines that abnormality has occurred in the optical line when the temporal change exceeds prescribed magnitude; and a fault location estimation unit that determines, as a fault location, a location where the temporal change exceeds the prescribed magnitude, or a location where the distance differential of the temporal change exhibits a peak.

Description

Technical Field

[0001] Relates to a system, apparatus, and method for monitoring an optical line.

Background Art

[0002] It is possible to connect to the Internet from terminals such as computers and smartphones and acquire a lot of information such as text, images, and videos. Optical communication technology supports connections to a lot of information. By installing communication equipment at both ends of the section and connecting them with an optical fiber in the access section from the premises to the user and the relay section from the premises to the premises, high-speed and large-capacity data transmission is realized.

[0003] As a means for checking the soundness of an optical line, distance loss measurement by the OTDR (Optical Time Domain Reflectometry) method, which is an optical evaluation method (for example, see Patent Document 1), is common. The OTDR method is a method of measuring the distance loss of an optical fiber by injecting pulsed light into the optical fiber in an optical cable and detecting the light intensity of the backscattered light propagating in the opposite direction to the pulsed light in the longitudinal direction of the optical fiber.

[0004] The OTDR method conducts a test when a new optical cable is laid and checks the soundness of the optical line before the installation of the upper-side communication equipment and the lower-side communication equipment, so that rapid line opening is possible when a user wishes to use the service. It is also an effective means for quickly checking the soundness of the optical line even after the line is opened, such as during a disaster. In that case, an in-service test can be carried out without affecting the communication service by using pulsed light of a wavelength different from that of the communication equipment (for example, see Patent Document 2).

[0005] This is a method of checking the soundness of the optical line by testing each time when the installer of the upper-side communication equipment and the lower-side communication equipment and the installer of the optical cable are the same and it is known that the communication service is normal. The occurrence of an abnormality in the communication service is confirmed by the presence or absence of transmission and reception of optical signals of the upper-side communication equipment and the lower-side communication equipment (for example, see Patent Document 3). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2008-304289 [Patent Document 2] Japanese Patent Publication No. 2003-222573 [Patent Document 3] Japanese Patent Publication No. 2012-205290 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, under normal circumstances, if the installers of the upper and lower communication equipment and the fiber optic cable installation manager are different people, the fiber optic cable installation manager will not know when a communication service anomaly occurs. If the installers of the upper and lower communication equipment detect an anomaly and then contact the fiber optic cable installation manager, there will be a time lag between the occurrence of the anomaly and the testing, which will not lead to a rapid recovery. Also, because the restoration of fiber optic lines that are in use during a communication service anomaly is a high priority, it is desirable to know the status of data communication.

[0008] Therefore, this disclosure aims to provide optical line monitoring technology that verifies the integrity of communication services by continuously monitoring optical fibers. [Means for solving the problem]

[0009] To achieve the above objective, we decided to continuously monitor the optical lines using an OTDR (Optical Time Domain Reflectometer).

[0010] Specifically, this disclosure is: Multiple optical couplers combine the light from the first terminal and the test light from the third terminal and output it to an optical line from the second terminal, and branch the backscattered light from the optical line input to the second terminal to the third terminal. A 1×N (where N is a positive integer) fiber selector that switches the third terminal of any of the above multiple optical couplers to the switching source terminal, An OTDR (Optical Time Domain Reflectometer) is connected to the switching source terminal of the 1×N fiber selector, sends test light to the third terminal of the optical coupler via the 1×N fiber selector, and detects backscattered light from the third terminal of the optical coupler. A state analysis unit extracts the time change of distance from the OTDR and backscattered light intensity, and determines that an abnormality has occurred in the optical path when the time change exceeds a predetermined magnitude. A fault location estimation unit determines a fault location as a position where the aforementioned time change exceeds a predetermined magnitude, or determines a fault location as a position where the distance derivative of the aforementioned time change is at its peak. A light line monitoring system characterized by comprising That is the case.

[0011] Specifically, this disclosure is: Multiple optical couplers that combine light from terminal 1 and test light from terminal 3 and output it to an optical line from terminal 2, branch the backscattered light from the optical line input to terminal 2 to terminal 3, and branch a portion of the light from terminal 1 to terminal 4, A 1×2N (where N is a positive integer) fiber selector that switches and connects either the third or fourth terminal of any of the multiple optical couplers to the source terminal, A 1x2 optical branching circuit is provided, in which the 1-side terminal is connected to the switching source terminal of the 1x2N fiber selector, An OTDR (Optical Time Domain Reflectometer) is connected to one of the two terminals of the 1x2 optical branch circuit, sends test light to the third terminal of the optical coupler via the 1x2N fiber selector, and detects the backscattered light from the third terminal of the optical coupler. A state analysis unit extracts the time change of distance from the OTDR and backscattered light intensity, and determines that an abnormality has occurred in the optical path when the time change exceeds a predetermined magnitude. A fault location estimation unit determines a fault location as a position where the aforementioned time change exceeds a predetermined magnitude, or determines a fault location as a position where the distance derivative of the aforementioned time change is at its peak. A light receiving circuit that converts light from the other terminal of the 1x2 optical branching circuit into an electrical signal, A communication status analysis unit determines that communication is in standby mode if the time-averaged signal intensity of the electrical signal from the light receiving circuit is within a predetermined range, and determines that communication is in progress if it exceeds the predetermined range. A light line monitoring system characterized by comprising That is the case.

[0012] Specifically, this disclosure is: Multiple optical couplers that combine light from terminal 1 and test light from terminal 3 and output it to an optical line from terminal 2, branch the backscattered light from the optical line input to terminal 2 to terminal 3, and branch a portion of the light from terminal 1 to terminal 4, A 2×2N (where N is a positive integer) fiber selector that interlocks the third and fourth terminals of any of the plurality of optical couplers to switch and connect them to a first source terminal and a second source terminal, respectively, An OTDR (Optical Time Domain Reflectometer) is connected to the first switching source terminal of the 2x2N fiber selector, sends test light to the third terminal of the optical coupler via the 2x2N fiber selector, and detects backscattered light from the third terminal of the optical coupler. A state analysis unit extracts the time change of distance from the OTDR and backscattered light intensity, and determines that an abnormality has occurred in the optical path when the time change exceeds a predetermined magnitude. A fault location estimation unit determines a fault location as a position where the aforementioned time change exceeds a predetermined magnitude, or determines a fault location as a position where the distance derivative of the aforementioned time change is at its peak. A light receiving circuit connected to the second switching source terminal of the 2x2N fiber selector, which converts light from the fourth terminal of the optical coupler via the 2x2N fiber selector into an electrical signal, A communication state analysis unit that determines that it is in a communication standby state if the time-average value of the signal intensity of the electrical signal from the light receiving circuit is within a predetermined range, and determines that it is in a communication state if it exceeds the predetermined range; An optical line monitoring system characterized by comprising is.

[0013] Specifically, the present disclosure A state analysis unit that transmits test light to an optical line, extracts the temporal change of the distance-backscattered light intensity from an OTDR (Optical Time Domain Reflectometer) that detects the backscattered light from the optical line, and determines that an abnormality has occurred in the optical line when the temporal change exceeds a predetermined magnitude; A fault position estimation unit that determines the position where the temporal change exceeds a predetermined magnitude as the fault position, or determines the position where the distance derivative of the temporal change is the peak as the fault position; An optical line monitoring device characterized by comprising is.

[0014] Specifically, the present disclosure A communication state analysis unit that determines that it is in a communication standby state if the time-average value of the signal intensity of the electrical signal from a light receiving circuit that converts light into an electrical signal is within a predetermined range, and determines that it is in a communication state if it exceeds the predetermined range, is further characterized by comprising.

[0015] Specifically, the present disclosure A first step of outputting test light to an optical line; A second step of detecting the backscattered light from the optical line and measuring the distance-backscattered light intensity; A third step of extracting the temporal change of the measured distance-backscattered light intensity and determining that an abnormality has occurred in the optical line when the temporal change exceeds a predetermined magnitude; A fourth step of determining the position where the temporal change exceeds a predetermined magnitude as the fault position, or determining the position where the distance derivative of the temporal change is the peak as the fault position; An optical line monitoring method characterized by comprising is.

[0016] Specifically, this disclosure is: A program for a computer to implement the optical line monitoring device described above. That is the case. [Effects of the Invention]

[0017] According to this disclosure, it is possible to provide optical line monitoring technology that verifies the health of communication services by continuously monitoring optical fibers. [Brief explanation of the drawing]

[0018] [Figure 1] The configuration of the optical line monitoring system disclosed herein is shown. [Figure 2] This disclosure demonstrates the operation of the optical line monitoring system. [Figure 3] This disclosure demonstrates the operation of the optical line monitoring system. [Figure 4] The configuration of the optical line monitoring system disclosed herein is shown. [Figure 5] This disclosure demonstrates the operation of the optical line monitoring system. [Figure 6] This disclosure demonstrates the operation of the optical line monitoring system. [Figure 7] This disclosure demonstrates the operation of the optical line monitoring system. [Modes for carrying out the invention]

[0019] Embodiments of this disclosure will be described in detail below with reference to the drawings. However, this disclosure is not limited to the embodiments shown below. These examples are illustrative, and this disclosure can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. In this specification and in the drawings, components with the same reference numerals refer to the same components.

[0020] (Embodiment 1) Figure 1 shows the configuration of the optical line monitoring system disclosed herein. The optical line 11 includes section A optical line 11-1 between the upper communication equipment 12 and the optical coupler 14, section B optical line 11-2 between the optical coupler 14 and the test light blocking filter 114, and section D optical line 11-3 between the optical coupler 14 and the 1×N (N is a positive integer, the same applies hereinafter) fiber selector 15-1. The optical coupler 14 has a first terminal (circled number "1" in Figure 1), a second terminal (circled number "2" in Figure 1), and a third terminal (circled number "3" in Figure 1). The optical coupler 14 merges the light from the upper communication equipment 12 input from the first terminal and the test light input from the third terminal and outputs it to section B optical line 11-2 from the second terminal, and branches the backscattered light from section B optical line 11-2 input to the second terminal to the third terminal.

[0021] To monitor multiple B-section optical lines 11-2 with a common OTDR (Optical Time Domain Reflectometer) 17, a 1×N fiber selector 15-1 is placed between the OTDR 17 and multiple optical couplers 14. The 1×N fiber selector 15-1 switches the connection between the OTDR 17 and the third terminal of one of the multiple optical couplers 14 via the D-section optical line 11-3.

[0022] OTDR17 is connected to the switching source terminal (the number "1" in parentheses in Figure 1) of the 1×N fiber selector 15-1. It receives pulsed test light from the third terminal of the optical coupler 14 via the 1×N fiber selector 15-1 and sends it out from the second terminal to the B section optical line 11-2. The backscattered light due to Rayleigh scattering generated in the B section optical line 11-2 propagates through the D section optical line 11-3 via the second and third terminals of the optical coupler 14. OTDR17 detects the backscattered light via the 1×N fiber selector 15-1. OTDR17 sends out pulsed light and measures the distance-backscattered light intensity, which is the backscattered light intensity as a function of distance to the B section optical line 11-2, each time it detects backscattered light. OTDR17 and its peripheral equipment are included in the optical test module 16.

[0023] OTDR17 uses test light of a different wavelength than the light used by the upper communication device 12 to constantly monitor the B section optical line 11-2. A test light blocking filter 114 is placed in the B section optical line 11-2 to block the test light so that it does not enter the lower communication device 13. Preferably, the test light blocking filter 114 is placed directly in front of the lower communication device 13.

[0024] The state analysis unit 19 extracts the time variation of distance-backscattered light intensity measured by the OTDR 17. If the extracted time variation does not exceed a predetermined magnitude, it determines that the light path is normal. If it exceeds the predetermined magnitude, it determines that an abnormality has occurred in the light path. The determination result is displayed on the result display unit 112.

[0025] The fault location estimation unit 110 determines a fault location when the time change extracted by the state analysis unit 19 exceeds a predetermined magnitude, or when the distance derivative of the time change reaches a peak. The fault location estimation unit 110 may operate when the state analysis unit 19 determines an abnormality in the optical line, or it may operate at all times. The state analysis unit 19 and the fault location estimation unit 110 are included in the optical line monitoring device 20.

[0026] The optical line monitoring method of the present disclosure comprises: a first step in which the OTDR17 outputs test light to the B section optical line 11-2; a second step in which the OTDR17 detects backscattered light from the B section optical line 11-2; a third step in which the state analysis unit 19 extracts the time change of distance-backscattered light intensity measured by the OTDR17 and determines that an abnormality has occurred in the B section optical line 11-2 when the time change exceeds a predetermined magnitude; and a fourth step in which the fault location estimation unit 110 determines the location where the time change extracted by the state analysis unit 19 exceeds a predetermined magnitude as the fault location, or determines the location where the distance derivative of the time change is at its peak as the fault location.

[0027] In the first step, OTDR17 outputs pulsed test light to section B optical line 11-2. Rayleigh scattering occurs within the optical fiber due to the test light, and the backscattered light that returns in the original direction propagates within the optical fiber.

[0028] In the second step, OTDR17 detects backscattered light from section B optical line 11-2, measures the distance-backscattered light intensity, and outputs the result.

[0029] The operation in the third step is shown in Figure 2. All waveforms of backscattered light intensity in Figure 2 are illustrative. In Figure 2, 21 is the distance-backscattered light intensity measurement result at time T0, 22 is the distance-backscattered light intensity measurement result at time T1, 23 is the distance-backscattered light intensity measurement result at time T2, 24 is the distance-backscattered light intensity measurement result at time T3, 25 is the difference in light intensity between the distance-backscattered light intensity measurement results at time T0 and time T1, 26 is the difference in light intensity between the distance-backscattered light intensity measurement results at time T1 and time T2, 27 is the difference in light intensity between the distance-backscattered light intensity measurement results at time T2 and time T3, 28 is the difference in light intensity between the distance-backscattered light intensity measurement results at time T0 and time T1 (after averaging), 29 is the difference in light intensity between the distance-backscattered light intensity measurement results at time T1 and time T2 (after averaging), 210 is the difference in light intensity between the distance-backscattered light intensity measurement results at time T2 and time T3 (after averaging), and 211 is the threshold.

[0030] The distance-backscattered light intensity measurement result 21 from OTDR17 at time T0 represents the backscattered light intensity due to Rayleigh scattering (e.g., logarithmic scale) as a function of the distance from the start to the end of the optical line under monitoring. The distance-backscattered light intensity measurement results 22, 23, and 24 show the waveforms at times T1, T2, and T3, respectively. Time T0 to time T3 is a pre-set time interval, and although Figure 2 shows up to time T3 as an example, waveforms are acquired at constant time intervals while the optical line under monitoring is being monitored.

[0031] Next, the state analysis unit 19 extracts the light intensity difference, which is the time change of two distance-backscattered light intensities acquired consecutively. For example, the time change of distance-backscattered light intensity measurement result 21 and distance-backscattered light intensity measurement result 22 appears as the light intensity difference 25 between time T0 and time T1. When the optical line is normal (time T0 to time T2), the waveform fluctuation in the time direction of the light intensity difference is caused by minute changes in the laser center frequency of the test light and the optical line under monitoring. The cause of waveform fluctuation is the same for light intensity differences 25, 26, and 27. When an abnormality occurs in the optical line (time T3), the backscattered light intensity beyond the fault location decreases (distance-backscattered light intensity measurement result 24). At this time, the light intensity difference 27 is the time change of the backscattered light intensity during the abnormal time (time T3) and the normal time (time T2), so the value of the light intensity difference changes at the fault location. The state analysis unit 19 determines that an abnormality has occurred in the optical path when the difference in light intensity exceeds a predetermined value (threshold).

[0032] As shown in Figure 2, light intensity differences 25, 26, and 27 contain waveform fluctuations. To suppress these waveform fluctuations, averaging may be performed in the distance direction of the optical line. In Figure 2, the averaging of light intensity differences 28, 29, and 210 is achieved by extracting L light intensity difference values ​​(P) from the beginning in the distance direction for an optical line of total length Lm. Here, P is a subscript that distinguishes the L light intensity difference values ​​(P).

number

[0033] The state analysis unit 19 may determine that an abnormality has occurred in the optical line if the value of the difference in light intensity after averaging exceeds a preset threshold 211. The 1×N fiber selector 15-1 sequentially switches the connected optical coupler 14 to monitor multiple optical lines.

[0034] The operation in the fourth step is shown in Figure 3. In Figure 3, 210 is the difference in light intensity after averaging, 31 is the derivative, and 32 is the peak position of the derivative. The fault location estimation unit 110 determines a fault location to be a position where the difference in light intensity, which is the time change of distance-backscattered light intensity, exceeds a predetermined magnitude (threshold 211), or determines a fault location to be the position where the distance derivative of the light intensity difference is at its peak.

[0035] When the distance derivative of the light intensity difference determines the peak position as the fault location, the derivative 31 obtained by the distance derivative of the light intensity difference 210 after averaging in Figure 3 is calculated. Discrete distance derivative of the light intensity difference (P) after averaging

number

[0036] As described above, the optical line monitoring system, optical line monitoring device, and optical line monitoring method of this disclosure make it possible to confirm the integrity of communication services by continuously monitoring optical fibers.

[0037] (Embodiment 2) Figure 4 shows the configuration of the optical line monitoring system of the present disclosure. The optical line 11 includes section A optical line 11-1 between the upper communication equipment 12 and the optical coupler 14, section B optical line 11-2 between the optical coupler 14 and the test light blocking filter 114, section D optical line 11-3 between the optical coupler 14 and the 1×2N fiber selector 15-2, and section C optical line 11-4 between the optical coupler 14 and the 1×2N fiber selector 15-2. The optical coupler 14 has a first terminal (circled number "1" in Figure 4), a second terminal (circled number "2" in Figure 4), a third terminal (circled number "3" in Figure 4), and a fourth terminal (circled number "4" in Figure 4). The optical coupler 14 combines the light from the upper communication device 12 input from the first terminal and the test light input from the third terminal and outputs it to the B section optical line 11-2 from the second terminal, branches the backscattered light from the B section optical line 11-2 input to the second terminal to the third terminal, and branches a portion of the light from the upper communication device 12 input from the first terminal to the fourth terminal.

[0038] A 1×2N fiber selector 15-2 is provided to monitor multiple B-section optical lines 11-2. The 1×2N fiber selector 15-2 switches and connects either the third or fourth terminal of one of the multiple optical couplers 14 to the switching source terminal of the 1×2N fiber selector 15-2 (the number in parentheses "1" in Figure 4) via the D-section optical line 11-3 or the C-section optical line 11-4. When operating the OTDR 17, the 1×2N fiber selector 15-2 connects its switching source terminal to the third terminal of one of the multiple optical couplers 14, and when operating the light receiving circuit 113, it connects its switching source terminal to the fourth terminal of the same optical coupler 14.

[0039] The 1x2 optical branching circuit 18 has a single terminal and two double terminals. It branches the light from the single terminal to the two double terminals and merges the light from the two double terminals back into the single terminal. The single terminal is connected to the switching source terminal of the 1x2N fiber selector 15-2. An OTDR 17 is connected to one of the double terminals, and a light receiving circuit 113 is connected to the other double terminal. The OTDR 17 emits pulsed test light through one of the double terminals of the 1x2 optical branching circuit 18 and detects the backscattered light.

[0040] The operation of the OTDR17, state analysis unit 19, and fault location estimation unit 110 is the same as in Embodiment 1. First, the OTDR17 operates by connecting to the third terminal of one of the multiple optical couplers 14. Next, when the state analysis unit 19 determines that an abnormality has occurred in the optical line, the 1×2N fiber selector 15-2 connects its switching source terminal to the fourth terminal of the same optical coupler 14.

[0041] The light receiving circuit 113 converts light from the upper communication device 12 into an electrical signal via the other terminal of the 1x2 optical branching circuit 18. The 1x2 optical branching circuit 18, OTDR 17, and light receiving circuit 113 are included in the optical test module 16.

[0042] The communication status analysis unit 111 determines that communication is in standby mode if the time-averaged signal intensity of the electrical signal from the light receiving circuit 113 is within a predetermined range, and determines that communication is in progress if it exceeds the predetermined range. The operation of the communication status analysis unit 111 is shown in Figure 5. In Figure 5, 42 is the electrical signal from the light receiving circuit 113 indicating periodic digital data, 43 is the absolute value of the average of that electrical signal, 44 is the electrical signal from the light receiving circuit 113 indicating random digital data, 45 is the absolute value of the average of that electrical signal, 46 is the range of change, and 47 is the absolute value of the average of the electrical signal at time T3.

[0043] When no data is being transferred between the upper communication device 12 and the lower communication device 13 (communication standby), the electrical signal from the light receiving circuit 113 becomes periodic digital data as shown in 42, and the absolute value of the average of the electrical signals remains constant over time as shown in 43.

[0044] On the other hand, when data is being transferred between the upper communication device 12 and the lower communication device 13 (communication in progress), the electrical signal from the light receiving circuit 113 becomes random digital data indicating the communication status, as shown in 44, and the absolute value of the average value of the electrical signal changes over time, as shown in 45. If the range of change is within a predetermined range 46, it is determined that communication is in standby mode, and if it exceeds the predetermined range 46, it is determined that communication is in progress. For example, the absolute value of the average value of the electrical signal at time T3, 47, exceeds the predetermined range 46, so it is determined that communication is in progress. The 1×2N fiber selector 15-2 sequentially switches the connected optical coupler 14 to monitor multiple optical lines.

[0045] Figure 6 shows an example of the display on the results display unit 112. In Figure 6, when the state of the optical line under monitoring is normal (time T0 to time T2), "Normal," which means the normal state determined by the state analysis unit 19, is displayed in the "Monitoring Status" column. When an abnormality occurs in the optical line under monitoring (time T3), "Abnormal," which means the abnormal state determined by the state analysis unit 19, is displayed in the "Monitoring Status" column, the "Distance L (km)" of the fault location determined by the fault location estimation unit 110 is displayed in the "Estimated Fault Location" column, and "Communicating" determined by the communication status analysis unit 111 is displayed in the "Communication Status During Fault" column.

[0046] In Figure 4, a 1x2 optical switch may be used instead of the 1x2 optical branching circuit 18. The 1x2 optical branching circuit switches the connection between the 1-side terminal and one of the two 2-side terminals. Using a 1x2 optical switch eliminates optical branching loss. When operating the OTDR 17, the 1x2N fiber selector 15-2 connects its switching source terminal to the third terminal of one of the multiple optical couplers 14, and in conjunction connects the 2-side of the 1x2 optical switch to the OTDR 17. When the state analysis unit 19 determines that an abnormality has occurred in the optical line, the 1x2N fiber selector 15-2 connects its switching source terminal to the fourth terminal of the same optical coupler 14, and in conjunction switches the 2-side of the 1x2 optical switch to the light receiving circuit 113. After switching to the light receiving circuit 113, the communication state analysis unit 111 starts operating.

[0047] The communication status analysis unit 111 may display the determination result on the result display unit 112 when the status analysis unit 19 determines that an abnormality has occurred in the optical line, or it may display the determination result at all times. The status analysis unit 19, the fault location estimation unit 110, and the communication status analysis unit 111 are included in the optical line monitoring device 20.

[0048] As described above, the optical line monitoring system, optical line monitoring device, and optical line monitoring method of this disclosure allow for the confirmation of the integrity of communication services through continuous monitoring of optical fibers. Furthermore, it is possible to confirm whether the upper communication equipment 12 is in communication or on standby when an abnormality occurs.

[0049] (Embodiment 3) Figure 7 shows the configuration of the optical line monitoring system of the present disclosure. The difference from Embodiment 2 is that a 2x2N fiber selector 15-3 is provided instead of the 1x2N fiber selector 15-2 of Embodiment 2. The 2x2N fiber selector 15-3 switches the third terminal of any of the multiple optical couplers 14 to the first switching source terminal (the number in parentheses "1" in Figure 7), and switches the fourth terminal of any of the multiple optical couplers 14 to the second switching source terminal (the number in parentheses "2" in Figure 7). The 2x2N fiber selector 15-3 operates in conjunction with the multiple optical couplers 14 to connect to the third and fourth terminals of the same optical coupler 14.

[0050] The arrangement of the 2x2N fiber selector 15-3 eliminates the need for the 1x2 optical branching circuit 18 in Embodiment 2. The elimination of the 1x2 optical branching circuit 18 eliminates the optical branching loss associated with it. The OTDR 17 is connected to the first switching source terminal of the 2x2N fiber selector 15-3, and the light receiving circuit 113 is connected to the second switching source terminal of the 2x2N fiber selector 15-3. The OTDR 17 is switched to the third terminal of one of the multiple optical couplers 14 via the 2x2N fiber selector 15-3, and the light receiving circuit 113 is switched to the fourth terminal of the same optical coupler 14 via the 2x2N fiber selector 15-3.

[0051] The operation of OTDR17, state analysis unit 19, fault location estimation unit 110, light receiving circuit 113, and communication state analysis unit 111 is the same as in Embodiment 1 or 2.

[0052] The 2x2N fiber selector 15-3 monitors multiple optical lines by sequentially switching the connected optical couplers 14. The 2x2N fiber selector 15-3 may also be composed of two 1x2N fiber selectors. In this case as well, the two 1x2N fiber selectors operate in conjunction so that they are connected to the third and fourth terminals of the same optical coupler 14 from among the multiple optical couplers 14.

[0053] As described above, the optical line monitoring system, optical line monitoring device, and optical line monitoring method of this disclosure allow for the confirmation of the integrity of communication services through continuous monitoring of optical fibers. Furthermore, it is possible to confirm whether the upper communication equipment 12 is in communication or on standby when an abnormality occurs.

[0054] The optical line monitoring device disclosed herein can also be implemented using a computer and a program. The program to be executed by the computer can be recorded on a recording medium or provided via a communication network. [Industrial applicability]

[0055] This disclosure can be applied to the information and communications industry. [Explanation of symbols]

[0056] 11: Optical line 11-1: Section A Light Path 11-2: Section B Light Path 11-3: Section D Light Path 11-4: Section C Light Path 12: Upper communication equipment 13: Lower communication equipment 14: Optical coupler 15-1:1×N Fiber Selector 15-2:1×2N Fiber Selector 15-3: 2×2N Fiber Selector 16: Optical test module 17:OTDR 18:1 x 2 Optical Splitter Circuit 19: State Analysis Unit 20: Optical track monitoring device 110: Fault location estimation unit 111: Communication Status Analysis Unit 112:Result display section 113: Light receiving circuit 114: Test light blocking filter

Claims

1. Multiple optical couplers that combine light from the first terminal and test light from the third terminal and output it to an optical line from the second terminal, branch the backscattered light from the optical line input to the second terminal to the third terminal, and branch a portion of the light from the first terminal to the fourth terminal, A 1x2N (where N is a positive integer) fiber selector that switches and connects either the third or fourth terminal of any of the plurality of optical couplers to the source terminal, A 1x2 optical branching circuit is provided, in which the 1-side terminal is connected to the switching source terminal of the 1x2N fiber selector, An Optical Time Domain Reflectometer (OTDR) is connected to one of the two terminals of the 1x2 optical branching circuit, sends test light to the third terminal of the optical coupler via the 1x2N fiber selector, and detects the backscattered light from the third terminal of the optical coupler. A state analysis unit extracts the time change of distance from the OTDR and backscattered light intensity, and determines that an abnormality has occurred in the optical path when the time change exceeds a predetermined magnitude. A fault location estimation unit determines a fault location as a position where the aforementioned time change exceeds a predetermined magnitude, or determines a fault location as a position where the distance derivative of the aforementioned time change is at its peak. A light receiving circuit that converts light from the other terminal of the 1x2 optical branching circuit into an electrical signal, A communication status analysis unit determines that communication is in standby mode if the time-averaged signal intensity of the electrical signal from the light receiving circuit is within a predetermined range, and determines that communication is in progress if it exceeds the predetermined range. A light line monitoring system characterized by comprising the following features.

2. Multiple optical couplers that combine light from the first terminal and test light from the third terminal and output it to an optical line from the second terminal, branch the backscattered light from the optical line input to the second terminal to the third terminal, and branch a portion of the light from the first terminal to the fourth terminal, A 2x2N (where N is a positive integer) fiber selector that interlocks the third and fourth terminals of any of the plurality of optical couplers to switch and connect them to a first source terminal and a second source terminal, respectively, An Optical Time Domain Reflectometer (OTDR) is connected to the first switching source terminal of the 2x2N fiber selector, sends test light to the third terminal of the optical coupler via the 2x2N fiber selector, and detects backscattered light from the third terminal of the optical coupler. A state analysis unit extracts the time change of distance from the OTDR and backscattered light intensity, and determines that an abnormality has occurred in the optical path when the time change exceeds a predetermined magnitude. A fault location estimation unit determines a fault location as a position where the aforementioned time change exceeds a predetermined magnitude, or determines a fault location as a position where the distance derivative of the aforementioned time change is at its peak. A light receiving circuit connected to the second switching source terminal of the 2x2N fiber selector, which converts light from the fourth terminal of the optical coupler via the 2x2N fiber selector into an electrical signal, A communication status analysis unit determines that communication is in standby mode if the time-averaged signal intensity of the electrical signal from the light receiving circuit is within a predetermined range, and determines that communication is in progress if it exceeds the predetermined range. A light line monitoring system characterized by comprising the following features.

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