JP4890354B2 - Optical pulse measuring instrument - Google Patents

Description

  The present invention relates to an optical pulse measuring instrument used for measuring an optical fiber for an optical communication network.

FIG. 8 is a diagram for explaining an optical fiber measurement method that has been conventionally performed.
As shown in FIG. 8, an optical fiber 40 makes a station side terminal device (Optical Line Terminal, hereinafter abbreviated as OLT) 41 and a subscriber side terminal device (Optical Network Unit, hereinafter abbreviated as ONU) 42. In an optical communication network in which the two are connected, an optical coupler 44 is provided in the optical fiber 40 in the facility building 43 on the station side, the optical fiber 40 is branched by the optical coupler 44, and an optical pulse measuring instrument (Optical Time Domain Reflectometer) is connected. Hereafter, abbreviated as OTDR.) 45 is connected, thereby realizing optical pulse measurement using OTDR45.
When measuring the target optical fiber 40, the operator uses the optical power meter 46 to confirm that there is no communication light from the ONU 42, and then performs optical pulse measurement using the OTDR 45. It was. In such a method, if the measurement pulse light is incident from the OTDR 45 by mistake during communication, the communication between the OLT 41 and the ONU 42 is affected, and a bit error occurs. There was a possibility that would become a disconnected state.

  Further, as shown in FIG. 9, in an optical communication network of a PON system in which an optical splitter 53 is provided in an optical fiber 40 and the OLT 41 and a plurality of ONUs 51 and 52 are connected by the optical splitter 53, the user home 54 side When performing measurement using the OTDR55, first, the ONU 52 was removed, then it was confirmed that there was no communication light from the OLT 41 with the optical power meter 56, and then optical pulse measurement was performed using the OTDR55. . Even in such a method, if pulse light is accidentally incident from the OTDR 55 during communication, the communication between the OLT 41 and the ONU 51 is affected, and a bit error occurs. In the worst case, the communication is cut off. There was a fear.

  Furthermore, a system that combines an OTDR and an optical power meter in an equipment building using an optical switch has been proposed (Patent Document 1), but even in such a system, a pulse from the OTDR is erroneously transmitted during communication. When light is incident, in the worst case, there is a possibility that communication is cut off.

JP 2002-328070 A

  As a common problem of the optical communication networks shown in FIGS. 8 and 9, it is necessary to prepare optical power meters 46 and 56 in addition to the OTDRs 45 and 55 in order to confirm the communication light from the OLT 41 and the ONUs 42, 51 and 52. there were. In addition, the trouble of switching between the optical power meters 46 and 56 and the OTDRs 45 and 55 is troublesome in the measurement. In particular, in the equipment building 43, there are a large number of optical fibers. There was also a danger of turning on the light. Furthermore, since it is necessary to measure with the optical power meters 46 and 56 before the measurement with the OTDRs 45 and 55, it takes time. In addition, in order to automate the above procedure, an optical switch for switching between the OTDRs 45 and 55 and the optical power meters 46 and 56 is required.

In the optical communication network shown in FIG. 9, a large optical loss due to bending occurs in the optical fiber between the optical splitter 53 and the ONU 52, and the optical power meter 56 detects the light reception level of the communication light from the OLT 41. It may not be done. In such a case, it is determined that there is no communication light from the OLT 41, and the measurement by the OTDR 55 is started. However, during the measurement by the OTDR 55, there is no light loss due to bending due to some time signature. Then, the pulsed light from the OTDR 55 may affect the communication between the OLT 41 and the ONU 51.
Similarly, even when the OLT 41 stops emitting light and the optical power meter 56 does not detect the light reception level of the communication light from the OLT 41, the measurement by the OTDR 55 is started, but the measurement is performed by the OTDR 55. If the communication light from the OLT 41 suddenly recovers during the operation, the pulse light from the OTDR 55 may affect the communication between the OLT 41 and the ONU 51.

  The present invention has been made in view of the above problems, and an object thereof is to provide an optical pulse measuring device capable of performing measurement with simple labor and configuration without affecting communication.

An optical pulse measuring instrument according to the first invention for solving the above-mentioned problems is as follows.
A branching means for branching the connection from the optical fiber to be measured;
A pulsed light source connected to one side of the branching unit and emitting measurement pulse light to the optical fiber via the branching unit;
A light receiving portion connected to the other branched side of the branching means, and receiving light from the optical fiber through the branching means;
An averaging unit that performs an averaging process of the received light levels of light received by the light receiving unit;
A control unit for controlling the pulse light source and the averaging unit,
The control unit is
A first step of performing addition averaging processing on the light receiving level of the light from the optical fiber received by the light receiving unit for a predetermined period of time before emitting pulsed light from the pulse light source; ,
If the light receiving level averaged and averaged in the first step exceeds a predetermined threshold, it is determined that the optical fiber is in communication, and emission of pulsed light from the pulsed light source is prohibited, A second step of ending the measurement with the pulsed light;
When the light reception level averaged in the first step is equal to or less than a predetermined threshold value, it is determined that the optical fiber is not communicating, starts emitting pulsed light from the pulse light source, and the pulse In the optical pulse measuring device that performs the third step of performing the measurement by light,
The control unit measures in advance a peak value of a noise level of the optical pulse measuring device itself and sets it as the predetermined threshold value .

An optical pulse measuring instrument according to a second invention for solving the above-mentioned problems is as follows.
A branching means for branching the connection from the optical fiber to be measured;
A pulsed light source connected to one side of the branching unit and emitting measurement pulse light to the optical fiber via the branching unit;
A light receiving portion connected to the other branched side of the branching means, and receiving light from the optical fiber through the branching means;
An averaging unit that performs an averaging process of the received light levels of light received by the light receiving unit;
A control unit for controlling the pulse light source and the averaging unit,
The control unit is
A first step of performing addition averaging processing on the light receiving level of the light from the optical fiber received by the light receiving unit for a predetermined period of time in a state where no pulsed light is emitted from the pulse light source. When,
If the light receiving level averaged and averaged in the first step exceeds a predetermined threshold, it is determined that the optical fiber is in communication, and emission of pulsed light from the pulsed light source is prohibited, A second step of ending the measurement with the pulsed light;
If the light receiving level averaged in the first step is equal to or lower than a predetermined threshold, it is determined that the optical fiber is not communicating, and emission of pulsed light from the pulsed light source is started, A third step of performing measurement with pulsed light and integrating the number of times or time of measurement with the pulsed light;
When the accumulated number or time does not exceed a predetermined number or time, a fourth step of stopping the emission of pulsed light from the pulse light source and returning to the first step ;
When the accumulated number of times or time exceeds a predetermined number of times or time, the measurement by the pulsed light is terminated, and the fifth step of displaying the result of the measurement is performed ,
In the optical pulse measuring instrument that repeats the first step, the second step, the third step, and the fourth step until the accumulated number of times or time exceeds a predetermined number of times or time ,
The control unit measures in advance a peak value of a noise level of the optical pulse measuring device itself and sets it as the predetermined threshold value .

An optical pulse measuring device according to a third invention for solving the above-mentioned problems is as follows.
A dummy fiber of a predetermined length to which an optical fiber to be measured is connected;
Branching means for branching the connection from the dummy fiber;
A pulse light source that is connected to one side of the branching unit and emits pulsed light for measurement to the optical fiber and the dummy fiber through the branching unit;
A light receiving unit connected to the other branched side of the branching unit, and receiving light from the optical fiber and the dummy fiber through the branching unit;
An averaging unit that performs an averaging process of the received light levels of light received by the light receiving unit;
A control unit for controlling the pulse light source and the averaging unit,
The control unit is
The pulse light source emits pulsed light, and the light receiving level of the optical fiber and the dummy fiber received by the light receiving unit for a predetermined fixed time is added and averaged by the averaging unit. 1 process,
When the portion corresponding to the dummy fiber out of the light reception levels averaged and averaged in the first step exceeds a predetermined threshold width range, it is determined that the optical fiber is communicating, and the pulse A second step of stopping the emission of the pulsed light from the light source and ending the measurement with the pulsed light;
If the portion corresponding to the dummy fiber in the received light level averaged in the first step is within a predetermined threshold width, it is determined that the optical fiber is not communicating, and the pulse light source emission to continue the pulse light, and executes the third step to continue carrying out the measurement by the pulsed light.

An optical pulse measuring device according to a fourth invention for solving the above-mentioned problems is as follows.
In the optical pulse measuring instrument according to any one of the first to third inventions,
An optical filter that transmits only the wavelength of the pulsed light of the pulsed light source and blocks other wavelengths is provided between the optical pulse measuring instrument and the optical fiber.

  According to the first invention, before the normal measurement of the optical pulse measuring device, the light receiving level of the light from the measurement target fiber is confirmed by the light receiving unit to determine whether the measurement target fiber is in communication, When the measurement target fiber is communicating, emission of pulsed light from the pulse light source is prohibited, so that the communication of the measurement target fiber can be prevented from being affected. Therefore, it is not necessary to prepare an optical power meter separately as in the prior art, and there is no need to switch to an optical power meter. As a result, it is possible to save labor during measurement and to perform measurement that has occurred at the time of switching. Connection errors of the target fiber can also be prevented. In addition, since it can be determined whether or not the measurement target fiber is communicating in a predetermined time (for example, about 1 second), it is necessary for the determination compared with the conventional case where switching to the optical power meter is required. Time can be significantly reduced. Furthermore, in order to automate the determination, it has been necessary to prepare an optical switch or the like in the past, but switching to an optical power meter itself is no longer necessary, so it is not necessary to prepare an optical switch or the like. The determination can be automated with a lot of effort and configuration.

  According to the second invention, the emission of the pulsed light from the pulsed light source is stopped every predetermined time and the light receiving level of the light from the measurement target fiber is confirmed by the light receiving unit. Even if there is no communication light, when the communication light is confirmed, the emission of the pulse light from the pulse light source can be stopped immediately, preventing the communication of the measurement target fiber from being affected. Can do.

  According to the third invention, since the light receiving level of the light from the dummy fiber is confirmed by the light receiving unit during the normal measurement of the optical pulse measuring device, it is initially assumed that there is no communication light in the measurement target fiber. However, when the communication light is confirmed during the measurement, the emission of the pulse light from the pulse light source can be stopped immediately, and the communication of the measurement target fiber can be prevented from being affected.

  According to the fourth invention, since the optical pulse measuring instrument is provided with the optical filter that transmits only the wavelength of the pulsed light of the pulsed light source, it can be determined whether communication is performed at the corresponding wavelength in the measurement target fiber, Further, it is possible to display a correct measurement waveform by blocking the incidence of wavelength components other than the corresponding wavelength to the optical pulse measuring instrument. Furthermore, since it is not necessary to know in advance what wavelength the corresponding fiber to be measured is communicating with, the operator can use the optical pulse measuring instrument with more peace of mind.

  An embodiment of an optical pulse measuring device (OTDR) according to the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram showing an example of an OTDR embodiment according to the present invention.
As shown in FIG. 1, the OTDR 1 of this embodiment is connected to the measurement target fiber 2 and is connected to a coupler 3 (branching means) that branches the connection from the measurement target fiber 2 and one side of the coupler 3 that is branched. The pulse light source 4 that emits the measurement pulse light to the measurement target fiber 2 via the coupler 3 and the other branched side of the coupler 3 are connected to each other from the measurement target fiber 2 via the coupler 3. A light receiving unit 5 that receives light, an averaging unit 6 that performs addition averaging processing of light reception levels of light received by the light receiving unit 5, a display unit 7 that displays a processing result in the averaging unit 6, and a pulse light source 4 and a control unit 8 for controlling the averaging unit 6.

  In the OTDR 1 of this embodiment, during normal measurement of the measurement target fiber 2, the light receiving unit 5 measures the reflected light (backscattered light) in the measurement target fiber 2 generated by the pulsed light emitted from the pulse light source 4. The display unit 7 displays the measurement waveform and performs OTDR measurement.

  The OTDR 1 of this embodiment shown in FIG. 1 has a configuration that is directly connected to the measurement target fiber 2, but as shown in FIG. 8 described above, the light between the OLT 41 and the ONU 42 via the coupler 44. It is good also as a structure inserted in a communication network.

  In the OTDR 1 of the present embodiment, pulse light is originally emitted from the pulse light source 4 and the reflected light (backscattered light) in the measurement target fiber 2 is measured by the light receiving unit 5, and pulse light is emitted from the pulse light source 4. Instead, the light receiving unit 5 measures the received light level. Then, the result of processing the received light level at the light receiving unit 5 by the averaging unit 6 is displayed on the display unit 7 as shown by solid lines in FIGS. 2A is a graph when there is no communication light, and FIG. 2B is a graph when there is communication light. In the graphs of FIGS. 2A and 2B, the vertical axis represents the light reception level and the horizontal axis represents the distance.

  When there is no communication light in the measurement target fiber 2, the light receiving unit 5 does not receive the communication light, and as shown by the solid line in FIG. The noise level (specifically, various noise levels possessed by the light receiving unit 5, the averaging unit 6, etc.) is displayed. On the other hand, when the measurement target fiber 2 has communication light, the light receiving unit 5 receives the communication light, and the display unit 7 displays the light reception level of the communication light as shown by the solid line in FIG. It will be.

  As can be seen from FIGS. 2A and 2B, there is a clear difference between the light reception level (noise level) when there is no communication light and the light reception level when there is communication light. Then, the peak value of the noise level of the OTDR 1 itself is set in advance as a threshold value (dotted line in FIGS. 2A and 2B), and the received light level displayed on the display unit 7 is set with reference to the threshold value. By determining the height, it is possible to determine whether the measurement target fiber 2 is communicating before emitting pulsed light from the pulsed light source 4.

  The peak of the noise level in OTDR1 may be measured at the factory at the time of shipment and set in advance because there is an individual difference in OTDR1, but since the operating environment temperature and usage frequency are also different, when OTDR1 is turned on, It is desirable to automatically measure the noise level peak inside the OTDR 1 and determine and set a threshold each time.

Therefore, in the OTDR 1 of the present embodiment, the following procedure is performed by the control unit 8.
(1) First, before emitting pulse light from the pulse light source 4, the light from the measurement target fiber 2 is received by the light receiving unit 5 for a certain period of time, and the measurement is performed. Are averaged by the averaging unit 6. In addition, as a fixed time, about 1 second is suitable, for example (1st process).
(2) The light reception level averaged and averaged by the averaging unit 6 is displayed on the display unit 7, and the level of the light reception level is determined based on a preset threshold value.
(3) If the light reception level exceeds a preset threshold value, it is determined that the measurement target fiber 2 is in communication, “in communication” is displayed on the display unit 7, and the pulse light from the pulse light source 4 is displayed. And the measurement by OTDR1 is terminated (second step).
(4) On the other hand, if the light reception level is equal to or lower than a preset threshold value, it is determined that the measurement target fiber 2 is not communicating, emits pulsed light from the pulsed light source 4, and performs measurement by OTDR1 (third) Process).

  As described above, by performing the above procedure before performing the measurement by OTDR1, if the received light level exceeds a certain threshold value, it is displayed on the display unit 7 as “in communication” and the measurement by OTDR1 is prohibited. It is possible to prevent communication from being affected. On the other hand, before the measurement by OTDR1, if the light reception level is below a certain threshold value, pulse light can be emitted from the pulse light source 4 and the measurement by OTDR1 can be performed. There is no need to prepare and reconnect. Furthermore, when the power of the OTDR 1 is turned on, the noise level peak inside the OTDR 1 is automatically measured and the threshold value is obtained each time, so that it can be used without being influenced by the use environment temperature or the use frequency.

FIG. 3 is a flowchart showing another example of the OTDR embodiment according to the present invention.
In this embodiment, the configuration of the OTDR itself may be the same as that of the OTDR 1 shown in FIG. Therefore, here, the procedure performed by the control unit 8 will be described with reference to the flowchart of FIG. 3 with reference to the OTDR 1 shown in FIG.

  First, the number of measurements or measurement time of OTDR measurement is reset (step S1).

  Next, also in the present embodiment, as in the first embodiment, before the pulse light source 4 emits the pulsed light, the light from the measurement target fiber 2 is received by the light receiving unit 5 for a certain period of time, and the measurement is performed. I do. Then, the light receiving level for a certain time is subjected to an addition averaging process by the averaging unit 6 (step S2; first step). In addition, as a fixed time, about 1 second is suitable, for example.

  Next, the light reception level averaged and averaged by the averaging unit 6 is displayed on the display unit 7, and it is determined whether or not the light reception level exceeds a preset threshold value (step S3). If the light reception level exceeds the preset threshold value, the process proceeds to step S7, and if the light reception level is equal to or less than the preset threshold value, the process proceeds to step S4. In addition, as a threshold value, the peak value of a noise level is suitable.

  If the light reception level exceeds a preset threshold value, it is determined that the measurement target fiber 2 is communicating, and “displaying communication” is displayed on the display unit 7, and the pulsed light from the pulse light source 4 is emitted. It prohibits and complete | finishes a series of procedures (step S7; 2nd process).

  If the received light level is equal to or lower than a preset threshold value, it is determined that the measurement target fiber 2 is not communicating, emits pulsed light from the pulse light source 4, and measures the measurement target fiber 2 using the OTDR1 (step S4). A third step).

  When the measurement by OTDR1 is completed, the number of measurements or measurement time of OTDR measurement is integrated, and it is determined whether or not the integrated number of measurements or measurement time exceeds a predetermined number of times or a predetermined time (steps S5 and S6). If the number of measurements or the measurement time does not exceed the specified number of times or the specified time, the process proceeds to step S8, and if it exceeds, the process proceeds to step S9. For example, about 10 times is preferable as the specified number of times, and about 10 seconds is preferable as the specified time.

  If the number of measurements or the measurement time does not exceed the specified number of times or the specified time, the emission of pulsed light from the pulse light source 4 is stopped (step S8; fourth step), and the process returns to step S2. Then, except when the light reception level exceeds the threshold (step S3), steps S2 to S6 and step S8 are repeated until the specified number of times or the specified time is exceeded, and the measurement by OTDR1 is performed for the specified number of times or the specified time. Will do.

  On the other hand, when the number of measurements or the measurement time exceeds the specified number of times or the specified time, the display unit 7 displays the measurement waveform by OTDR1, and the series of procedures is terminated (step S9; fifth step).

  In the first embodiment described above, the light reception level is only checked once before the measurement by OTDR1, but in this embodiment, the measurement by OTDR1 is repeated a plurality of times and the light reception level is confirmed during the repetition. Therefore, even if the status of the measurement target fiber 2 changes and communication is in progress, it is detected that “communication is in progress” and the emission of pulsed light from the OTDR 1 is immediately stopped for communication with other users. It is possible to prevent the influence. For example, when the measurement target fiber 2 that is initially determined to be in a disconnected state due to bending loss returns to a normal state due to relaxation of bending loss, it is detected that “communication” is performed by the above procedure, and from the OTDR 1 The emission of the pulsed light is immediately stopped to prevent other users' communications from being affected.

FIG. 4 is a block diagram showing another example of the embodiment of the OTDR according to the present invention.
As shown in FIG. 4, the OTDR 10 of this embodiment includes a dummy fiber 11 having a predetermined length connected to the measurement target fiber 2, a coupler 3 that branches the dummy fiber 11, a pulse light source 4 connected to the coupler 3, and The light receiving unit 5, the averaging unit 6, the display unit 7, and the control unit 8 are included. That is, the OTDR 10 of the present embodiment has a configuration in which the dummy fiber 11 is inserted between the measurement target fiber 2 and the coupler 3, and the other configurations are the same as the OTDR 1 shown in FIG. Therefore, here, the same components as those in OTDR1 shown in FIG.

  As the dummy fiber 11, its characteristics (particularly loss characteristics) are known, and it is desirable to use a long one to some extent. This is because it is easy to set a threshold width in the measurement described later by using a loss characteristic known, and by using a somewhat long one, noise due to communication light appearing in that portion is reduced. This is because it can be clearly confirmed. The length of the dummy fiber 11 is preferably long, but considering the loss of the dummy fiber 11, it is desirable that the length of the light received from the measurement target fiber 2 can be confirmed.

  Note that the OTDR 10 of this embodiment shown in FIG. 4 is also configured to be directly connected to the measurement target fiber 2, but as shown in FIG. 8 described above, the light between the OLT 41 and the ONU 42 via the coupler 44. It is good also as a structure inserted in a communication network.

  Unlike the first and second embodiments described above, the OTDR 10 of this embodiment checks whether or not the measurement target fiber 2 is in a communication state during measurement by the OTDR 10, and the display unit 7 uses pulse light. The measured waveform is displayed as shown by the solid lines in FIGS. 5A is a graph when there is no communication light, and FIG. 5B is a graph when there is communication light. In the graphs of FIGS. 5A and 5B, the vertical axis represents the light reception level and the horizontal axis represents the distance.

  When there is no communication light in the measurement target fiber 2, as shown by the solid line in FIG. 5A, the communication light from the measurement target fiber 2 does not appear as noise in the section of the dummy fiber 11 in the apparatus. The measurement waveform is observed in a state where the is not superimposed. On the other hand, when the measurement target fiber 2 has communication light, as shown by the solid line in FIG. 5B, the communication light from the measurement target fiber 2 becomes noise in the section of the dummy fiber 11 in the apparatus. The measurement waveform is observed with this noise superimposed.

  As can be seen from FIGS. 5A and 5B, when there is no communication light, no noise is superimposed on the measurement waveform in the dummy fiber 11, and when there is communication light, the noise is added to the measurement waveform in the dummy fiber 11. Therefore, based on the peak value of the amplitude of the noise to be superimposed, the upper threshold value and the lower threshold value are set in advance (see dotted lines in FIGS. 5A and 5B). At the time of measurement, the OTDR 10 determines whether the measured waveform of the dummy fiber 11 displayed on the display unit 7 is within the threshold width based on the upper threshold and the lower threshold range (threshold width). During the measurement, it can be determined whether the measurement target fiber 2 is communicating.

  In this embodiment, it is necessary to consider the loss of the dummy fiber 11 itself for the upper threshold and the lower threshold. Therefore, as observed in FIG. 5A, the upper threshold and the lower threshold need to be changed according to the distance in the same manner as the change in the light receiving level of the dummy fiber 11 when there is no communication light. Even if the threshold width is constant, the upper threshold and the lower threshold are monotonously decreased with the same inclination as the change in the light receiving level of the dummy fiber 11 as the distance increases.

  In addition, the threshold width may be measured at the factory at the time of shipment and set in advance because there is an individual difference in OTDR10. However, since the operating environment temperature and frequency of use differ, the threshold width is automatically set when the OTDR10 is turned on. It is desirable to obtain and set the threshold width.

Therefore, in the OTDR 10 of the present embodiment, the following procedure is performed by the control unit 8.
(1) First, pulse light is emitted from the pulse light source 4, and at that time, light from the measurement target fiber 2 and the dummy fiber 11 is received by the light receiving unit 5 for a certain period of time, and the measurement is performed. Then, the light receiving level for a certain time is subjected to an addition averaging process by the averaging unit 6 (first step).
(2) The received light level averaged and averaged by the averaging unit 6 is displayed on the display unit 7 and it is determined whether or not there is a measurement waveform in the dummy fiber 11 within a preset threshold width.
(3) If the measurement waveform in the dummy fiber 11 exceeds the preset threshold range, it is determined that the measurement target fiber 2 is communicating, and “in communication” is displayed on the display unit 7. Then, the emission of the pulsed light from the pulsed light source 4 is immediately stopped, and the measurement by the OTDR 10 is finished (second step).
(4) On the other hand, if the measurement waveform in the dummy fiber 11 is within a preset threshold width range, it is determined that the measurement target fiber 2 is not communicating, and pulse light from the pulse light source 4 is continued. Measurement is continued (third step).

  As described above, in the OTDR 10, by performing the above procedure, even if the measurement by the OTDR 10 is started and the pulsed light is emitted, if the measurement waveform of the dummy fiber 11 exceeds the preset threshold width range. Since it is displayed on the display unit 7 as “in communication” and the measurement by the OTDR 10 is interrupted, it is possible to prevent the communication from being erroneously affected.

  In the first embodiment described above, the light reception level is checked only once before the measurement by OTDR1, but in this embodiment, the light reception level of the measurement waveform of the dummy fiber 11 is confirmed at the time of emitting the pulsed light. Thus, whether or not the measurement target fiber 2 is communicating is determined, so even if the status of the measurement target fiber 2 changes and changes during communication, it is immediately detected that the measurement target fiber 2 is communicating, and the OTDR 10 It is possible to stop the emission of the pulsed light from the mobile phone and to prevent other users' communications from being affected. For example, when there is a loss variation in the measurement target fiber 2, more specifically, even when the measurement target fiber 2 that is initially determined to be in a disconnected state due to bending loss returns to a normal state due to relaxation of the bending loss. By the above procedure, it is immediately detected that “communication is in progress”, and emission of pulsed light from the OTDR 10 is stopped to prevent other users from being affected.

FIG. 6 is a block diagram showing another example of the embodiment of the OTDR according to the present invention.
In this embodiment, the OTDR 1 shown in FIG. 1 of the first embodiment or the OTDR 10 shown in FIG. 4 of the third embodiment is connected to the optical communication network. In addition, although the overlapping description is abbreviate | omitted about OTDR1 and OTDR10 here, the wavelength of the pulsed light light-emitted from the pulse light source 4 is demonstrated as lambda1 for convenience.

  As shown in FIG. 6, in this embodiment, a coupler 24 is inserted into the optical communication network between the OLT 21 and the ONU 22 connected by the optical fiber 20, and a specific wavelength λ <b> 1 is added to a portion branched by the coupler 24. This is a configuration in which OTDR1 (or OTDR10) is connected through an optical filter 25 that only transmits light. That is, the optical filter 25 is inserted between the optical fiber 20 to be measured and the OTDR1 (or OTDR10), and a specific wavelength λ1 is provided between the optical fiber 20 to be measured and the OTDR1 (or OTDR10). Only the light of is transmitted and received. The OLT 21, the coupler 24, the optical filter 25, and OTDR 1 (or OTDR 10) are accommodated in the equipment building 23.

  When a WDM (Wavelength Division Multiplexing) system is applied to the optical communication network shown in FIG. 6, since the WDM system uses a plurality of communication wavelengths, the communication wavelength used in the WDM system is OTDR1 ( Or, it does not necessarily match the wavelength of the pulsed light emitted from the pulse light source 4 of OTDR10) (it does not necessarily interfere). Accordingly, the optical filter 25 that transmits a specific wavelength band (wavelength λ1) and blocks other wavelengths is inserted into the connection portion of the OTDR1 (or OTDR10) to the optical fiber 20 side, thereby allowing the first to first embodiments. Using the procedure shown in FIG. 3, it is possible to confirm whether or not the optical fiber 20 is communicating at the wavelength λ1 of the pulsed light. In addition, this optical filter 25 can also prevent the incidence of light other than the wavelength λ1 to enter the OTDR1 (or OTDR10), and display a correct measurement waveform without knowing in advance which communication wavelength the user is using. can do.

FIG. 7 is a block diagram showing another example of the embodiment of the OTDR according to the present invention.
In this embodiment, the OTDR 1 shown in FIG. 1 of the first embodiment or the OTDR 10 shown in FIG. 4 of the third embodiment is connected to a PON optical communication network. In this case as well, the overlapping description of OTDR1 and OTDR10 is omitted, and the wavelength of the pulsed light emitted from the pulsed light source 4 is also defined as λ1 for convenience. Further, the same components as those shown in FIG. 6 are denoted by the same reference numerals, and redundant description thereof is also omitted.

  As shown in FIG. 7, this embodiment is for a PON optical communication network in which an optical splitter 32 is provided in an optical fiber 20 and an OLT 21 and an ONU 31 are connected by the optical splitter 32. In the user home 33 where the optical fiber 20 is branched by 32, OTDR1 (or OTDR10) is connected through an optical filter 34 that transmits only a specific wavelength λ1. That is, the optical filter 34 is inserted between the optical fiber 20 to be measured and OTDR1 (or OTDR10), and a specific wavelength λ1 is provided between the optical fiber 20 to be measured and OTDR1 (or OTDR10). Only the light of is transmitted and received.

  In the PON optical communication network shown in FIG. 7, as in the fourth embodiment, when the WDM system is applied, since the WDM system uses a plurality of communication wavelengths, the communication wavelengths used in the WDM system are different. , The wavelength of the pulsed light emitted from the pulse light source 4 of OTDR1 (or OTDR10) does not necessarily match (not necessarily interfere). Therefore, by inserting an optical filter 34 that transmits a specific wavelength band (wavelength λ1) and blocks other wavelengths into the connection portion of the OTDR1 (or OTDR10) to the optical fiber 20 side, Using the procedure shown in FIG. 3, it is possible to confirm whether or not the optical fiber 20 is communicating at the wavelength λ1 of the pulsed light. In addition, the optical filter 34 can also prevent incidence of light having a wavelength other than the wavelength λ1 to OTDR1 (or OTDR10), and display a correct measurement waveform.

  The optical pulse measuring device according to the present invention is suitable for measuring an optical fiber that is already laid and used as a communication network.

It is a block diagram which shows an example of embodiment of the optical pulse measuring device which concerns on this invention. The measurement result in the optical pulse measuring device shown in FIG. 1 is shown, (a) is a graph when there is no communication light, (b) is a graph when there is communication light. It is a flowchart explaining the other control procedure used with the optical pulse measuring device shown in FIG. It is a block diagram which shows another example of embodiment of the optical pulse measuring device which concerns on this invention. FIGS. 4A and 4B show measurement results in the optical pulse measuring device shown in FIG. 4. FIG. 4A is a graph when there is no communication light, and FIG. 4B is a graph when there is communication light. It is a block diagram which shows another example of embodiment of the optical pulse measuring device which concerns on this invention. It is a block diagram which shows another example of embodiment of the optical pulse measuring device which concerns on this invention. It is a figure explaining the measuring method of the optical fiber implemented conventionally. It is a figure explaining the measuring method of the optical fiber implemented conventionally in the PON system optical communication network.

Explanation of symbols

1, 10 Optical pulse measuring instrument (OTDR)
2 Measurement object fiber 3 Coupler 4 Pulsed light source 5 Light receiving unit 6 Averaging unit 7 Display unit 8 Control unit 11 Dummy fiber 25, 34 Optical filter

Claims (4)

A branching means for branching the connection from the optical fiber to be measured;
A pulsed light source connected to one side of the branching unit and emitting measurement pulse light to the optical fiber via the branching unit;
A light receiving portion connected to the other branched side of the branching means, and receiving light from the optical fiber through the branching means;
An averaging unit that performs an averaging process of the received light levels of light received by the light receiving unit;
A control unit for controlling the pulse light source and the averaging unit,
The control unit is
A first step of performing addition averaging processing on the light receiving level of the light from the optical fiber received by the light receiving unit for a predetermined period of time before emitting pulsed light from the pulse light source; ,
If the light receiving level averaged and averaged in the first step exceeds a predetermined threshold, it is determined that the optical fiber is in communication, and emission of pulsed light from the pulsed light source is prohibited, A second step of ending the measurement with the pulsed light;
When the light reception level averaged in the first step is equal to or less than a predetermined threshold value, it is determined that the optical fiber is not communicating, starts emitting pulsed light from the pulse light source, and the pulse In the optical pulse measuring device that performs the third step of performing the measurement by light,
The said control part measures the peak value of the noise level which the said optical pulse measuring device itself has beforehand, and sets it as the said predetermined threshold value, The optical pulse measuring device characterized by the above-mentioned . A branching means for branching the connection from the optical fiber to be measured;
A pulsed light source connected to one side of the branching unit and emitting measurement pulse light to the optical fiber via the branching unit;
A light receiving portion connected to the other branched side of the branching means, and receiving light from the optical fiber through the branching means;
An averaging unit that performs an averaging process of the received light levels of light received by the light receiving unit;
A control unit for controlling the pulse light source and the averaging unit,
The control unit is
A first step of performing addition averaging processing on the light receiving level of the light from the optical fiber received by the light receiving unit for a predetermined period of time in a state where no pulsed light is emitted from the pulse light source. When,
If the light receiving level averaged and averaged in the first step exceeds a predetermined threshold, it is determined that the optical fiber is in communication, and emission of pulsed light from the pulsed light source is prohibited, A second step of ending the measurement with the pulsed light;
If the light receiving level averaged in the first step is equal to or lower than a predetermined threshold, it is determined that the optical fiber is not communicating, and emission of pulsed light from the pulsed light source is started, A third step of performing measurement with pulsed light and integrating the number of times or time of measurement with the pulsed light;
When the accumulated number or time does not exceed a predetermined number or time, a fourth step of stopping the emission of pulsed light from the pulse light source and returning to the first step ;
When the accumulated number of times or time exceeds a predetermined number of times or time, the measurement by the pulsed light is terminated, and the fifth step of displaying the result of the measurement is performed ,
In the optical pulse measuring instrument that repeats the first step, the second step, the third step, and the fourth step until the accumulated number of times or time exceeds a predetermined number of times or time ,
The said control part measures the peak value of the noise level which the said optical pulse measuring device itself has beforehand, and sets it as the said predetermined threshold value, The optical pulse measuring device characterized by the above-mentioned . A dummy fiber of a predetermined length to which an optical fiber to be measured is connected;
Branching means for branching the connection from the dummy fiber;
A pulse light source that is connected to one side of the branching unit and emits pulsed light for measurement to the optical fiber and the dummy fiber through the branching unit;
A light receiving unit connected to the other branched side of the branching unit, and receiving light from the optical fiber and the dummy fiber through the branching unit;
An averaging unit that performs an averaging process of the received light levels of light received by the light receiving unit;
A control unit for controlling the pulse light source and the averaging unit,
The control unit is
The pulse light source emits pulsed light, and the light receiving level of the optical fiber and the dummy fiber received by the light receiving unit for a predetermined fixed time is added and averaged by the averaging unit. 1 process,
When the portion corresponding to the dummy fiber out of the light reception levels averaged and averaged in the first step exceeds a predetermined threshold width range, it is determined that the optical fiber is communicating, and the pulse A second step of stopping the emission of the pulsed light from the light source and ending the measurement with the pulsed light;
If the portion corresponding to the dummy fiber in the received light level averaged in the first step is within a predetermined threshold width, it is determined that the optical fiber is not communicating, and the pulse light source the continued emission of pulsed light, an optical pulse measuring instrument and to execute a third step of subsequently performing the measurement by the pulsed light. In the optical pulse measuring device according to any one of claims 1 to 3,
An optical pulse measuring device, wherein an optical filter that transmits only the wavelength of the pulsed light from the pulse light source and blocks other wavelengths is provided between the optical pulse measuring device and the optical fiber.

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