Measurement system and method

Abstract

To shorten a time required for measuring a property of an optical fiber.SOLUTION: A measurement system comprises: an optical fiber which includes a plurality of segments sectioned in a longitudinal direction; a measurement device which transmits pulsed pump light to the optical fiber to measure a spectrum of Brillouin scattering light generated in the optical fiber; and a switch which is provided between the adjacent segments in the plurality of segments and optically connects or separates the adjacent segments. Measurement by the measurement device includes: selecting the segment optically connected to the measurement device in the plurality of segments by controlling the switch; and measuring the spectrum of the Brillouin scattering light generated in the selected segment.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a measurement system and a measurement method. [Background technology]

[0002] There is known a technique for measuring the characteristics of an optical fiber by transmitting pulsed pump light into the optical fiber and measuring the spectrum of Brillouin scattered light generated in response to the pump light within the optical fiber (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-159987 A Summary of the Invention [Problem to be solved by the invention]

[0004] The interval between the transmission of the pump light is set to be longer than the time it takes for the pump light to travel back and forth through the optical fiber. The longer the optical fiber, the longer the interval between the transmission of the pump light, and the longer the time required for measurement.

[0005] An object of the present invention is to reduce the time required to measure the characteristics of an optical fiber. [Means for solving the problem]

[0006] A measurement system according to one aspect includes an optical fiber including a plurality of segments partitioned in the longitudinal direction, a measurement device that sends pulsed pump light into the optical fiber and measures the spectrum of Brillouin scattered light generated within the optical fiber, and a switch provided between adjacent segments of the plurality of segments for optically connecting or disconnecting the adjacent segments, wherein measurement by the measurement device includes controlling the switch to select a segment from the plurality of segments that is to be optically connected to the measurement device, and measuring the spectrum of the Brillouin scattered light generated within the selected segment.

[0007] A measurement method according to one aspect includes transmitting pulsed pump light into an optical fiber and measuring the spectrum of Brillouin scattered light generated within the optical fiber, wherein the optical fiber includes a plurality of segments partitioned in the longitudinal direction, and a switch is provided between adjacent segments among the plurality of segments for optically connecting or disconnecting the adjacent segments, and the measuring includes controlling the switch to select a segment from the plurality of segments to be connected to a measurement device, and measuring the spectrum of the Brillouin scattered light generated within the selected segment. Effect of the Invention

[0008] According to the present invention, it is possible to reduce the time required to measure the characteristics of an optical fiber. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of a schematic configuration of a measurement system according to an embodiment. [Diagram 2] FIG. 11 is a diagram illustrating an example of settings by a control unit. [Diagram 3] 4 is a flowchart showing an example of a process (measurement method) executed in the measurement device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment will be described with reference to the drawings. The same elements are given the same reference numerals, and duplicated descriptions will be omitted as appropriate.

[0011] 1 is a diagram showing an example of a schematic configuration of a measurement system according to an embodiment. The measurement system 100 includes a fiber device 1 and a measurement device 2.

[0012] The fiber device 1 includes an optical fiber FUT, a switch SW (illustrated as switch SW12, etc.), and a terminator T. The characteristics of an arbitrary position in the longitudinal direction of the optical fiber FUT are measured by a measurement device 2. Examples of the characteristics are physical quantities such as strain and temperature. The characteristics of each of a plurality of positions in the longitudinal direction of the optical fiber FUT may be measured, in which case the characteristic distribution (strain distribution, etc.) in the longitudinal direction of the optical fiber FUT is measured.

[0013] Of the ends of the optical fiber FUT, an end optically connected to the measurement device 2 is referred to as a near end NE and illustrated. An end opposite to the near end NE is referred to as a far end FE and illustrated. The optical fiber FUT includes a plurality of segments FS partitioned in the longitudinal direction. Examples of the plurality of segments FS include segments FS1 to FS4.

[0014] Segment FS1 is the first segment optically connected to the measurement device 2. One end of segment FS1 (the end on the measurement device 2 side) constitutes the near end NE of the fiber FUT. Segment FS2 is the second segment located on the opposite side of segment FS1 from the measurement device 2 (the far end FE side). Segment FS3 is the third segment located on the opposite side of segment FS2 from segment FS1. Segment FS4 is the fourth segment located on the opposite side of segment FS3 from segment FS2. The end of segment FS4 on the opposite side to the measurement device 2 side constitutes the far end FE of the fiber FUT.

[0015] The switches SW are provided between adjacent segments FS. The number of switches SW provided is one less than the number of segments FS, i.e., three switches SW in this example. In order to distinguish between the switches SW, they are illustrated as switch SW12, switch SW23, and switch SW34. The switch SW12 is provided between segments FS1 and FS2. The switch SW23 is provided between segments FS2 and FS3. The switch SW34 is provided between segments FS3 and FS4.

[0016] The switch SW optically connects or disconnects adjacent segments FS on either side of the switch SW. In the example shown in FIG. 1, the switch SW optically terminates the segment FS on the side of the measuring device 2, thereby disconnecting adjacent segments FS. A terminator T is used for the termination. The terminator T is an optical terminator, and optically terminates a segment FS by being optically connected to the segment FS. The same number of terminators T as the number of segments FS, that is, four terminators T in this example, are provided. In order to distinguish each terminator T from the others, they are referred to as terminators T1 to T4 and illustrated.

[0017] The specific configuration of the switch SW is not particularly limited, and various known optical switches may be used. In the example shown in FIG. 1, the switch SW includes ports P1 to P3. The segment FS on the side of the measuring device 2 is optically connected to the port P1. The segment FS on the opposite side to the measuring device 2 is optically connected to the port P2. The terminator T is optically connected to the port P3. The switch SW switches between a state in which the port P1 and the port P2 are optically connected, and a state in which the port P1 and the port P3 are optically connected. The port P1 and the port P2 are optically connected to each other, thereby optically connecting adjacent segments FS. The port P1 and the port P3 are optically connected to each other, thereby optically connecting the segment FS on the side of the measuring device 2 to the terminator T.

[0018] The other end of the segment FS1 (the end opposite the near end NE) is optically connected to a port P1 of the switch SW12. One end of the segment FS2 is optically connected to a port P2 of the switch SW12. A terminator T1 is optically connected to a port P3 of the switch SW12.

[0019] The other end of the segment FS2 is optically connected to a port P1 of the switch SW23. One end of the segment FS3 is optically connected to a port P2 of the switch SW23. A terminator T2 is optically connected to a port P3 of the switch SW23.

[0020] The other end of the segment FS3 is optically connected to a port P1 of the switch SW34. One end of the segment FS4 is optically connected to a port P2 of the switch SW34. A terminator T3 is optically connected to a port P3 of the switch SW34. Furthermore, a terminator T4 is optically connected to the other end (far end FE) of the segment FS4.

[0021] The measurement device 2 will be described. The measurement device 2 measures the characteristics of the optical fiber FUT of the fiber device 1. In the following, a time gate BOCDR (Brillouin Optical Correlation Domain Reflectometry) method will be described as an example of a measurement method.

[0022] The measurement device 2 generates pump light and transmits (injects) it into the optical fiber FUT. The measurement device 2 includes a light source 21, a modulator 22, a coupler 23, a pulsing unit 24, a delay unit 25, a circulator 26, and a terminal 27 as elements related to the generation of pump light and the injection of the pump light into the optical fiber FUT.

[0023] The light source 21 outputs light. The light source 21 includes, for example, an LD (Laser Diode). The modulator 22 is an FM modulator that performs frequency modulation on the light output by the light source 21. The light after frequency modulation is referred to as modulated light L. FM This is referred to and illustrated.

[0024] The coupler 23 couples the modulated light L from the light source 21. FM One of the two split lights is then used as the modulated light L FM The other light is referred to as the reference light L REF The modulated light L FM The reference light L is sent to the pulsing unit 24. REF is sent to a mixer 28, which will be described later.

[0025] The pulsing unit 24 converts the modulated light L FM The pulser 24 includes, for example, a polarization-dependent semiconductor optical amplifier (also called a BOA). The pulsed modulated light L FM , the pump light L P This is referred to and illustrated.

[0026] The delay unit 25 delays the pump light L P The delayer 25 includes, for example, an optical fiber (delay optical fiber) having a length that provides a desired delay. By providing a delay, the zero-order correlation peak, whose position does not change even when the modulation frequency is swept, is positioned outside the optical fiber FUT.

[0027] The circulator 26 receives the pump light L P is guided to a terminal 27. A near end NE of the optical fiber FUT is optically connected to the terminal 27. The pump light LP is sent from the terminal 27 to the optical fiber FUT.

[0028] Pump light L sent from terminal 27 to the optical fiber FUT P The light that has returned to the terminal 27 is referred to as the return light L. S The return light L S includes Brillouin scattered light. The return light L S is sent via a circulator 26 to a mixer 28, which will be described later.

[0029] The measuring device 2 detects the return light LS The characteristics of the optical fiber FUT are measured based on the Brillouin scattered light contained in the optical fiber FUT. The measuring device 2 includes a mixer 28, a spectrum analyzer 29, and a calculating section 30 as elements related to the characteristic measurement.

[0030] The mixer 28 receives the reference light L from the coupler 23. REF and the return light L from the circulator 26 S The frequency-modulated reference light L is mixed with the reference light L and converted into an electrical signal (OE conversion). REF and return light L S The phase difference between the two is an integer multiple of 2π, and the phases of the two lights are aligned and reinforce each other. The return light L from the position (correlation peak position) in the optical fiber FUT according to the modulation frequency S The electrical signal is an RF signal in the GHz band.

[0031] The spectrum analyzer 29 analyzes the return light L based on the electrical signals selectively received by the mixer 28. S The spectrum of the Brillouin scattered light contained in the optical fiber FUT is measured. The spectrum analyzer 29 is an electrical spectrum analyzer (ESA). The electrical signal input to the spectrum analyzer 29 is selected in terms of time based on the above-mentioned correlation peak position, i.e., the propagation time (return time) of the return light LS from the measurement position in the optical fiber FUT. The spectrum of the Brillouin scattered light generated at the measurement position in the optical fiber FUT is measured. The spectrum of the Brillouin scattered light measured in this manner is called BGS (Brillouin Gain Spectrum). The spectrum of the Brillouin scattered light in this disclosure refers to this BGS.

[0032] The calculation unit 30 calculates the frequency shift amount of the peak frequency at which the intensity is maximum in the BGS. This frequency shift amount is called BFS (Brillouin Frequency Shift). The BFS is proportional to the physical quantity of the optical fiber FUT, i.e., the value of strain, temperature, etc. From the calculated BFS, the strain, temperature, etc. of the optical fiber FUT at the measurement position can be obtained. In this manner, the characteristics of the optical fiber FUT are measured.

[0033] To further explain the measurement device 2, the measurement device 2 includes a control unit 31. The control unit 31 controls each element of the measurement device 2 to thereby perform overall control of the measurement device 2. The control is performed using, for example, a control signal. Several examples of control will be described.

[0034] For example, the control unit 31 controls the modulator 22 to modulate the modulated light L FM The control unit 31 sets a modulation frequency. As described above, the measurement position in the optical fiber FUT changes depending on the modulation frequency. More specifically, the control unit 31 sweeps the modulation frequency. By sweeping the modulation frequency, the characteristics (distribution characteristics) of the optical fiber FUT are measured at each of a plurality of different positions in the longitudinal direction of the optical fiber FUT. The control unit 31 may set the sweep speed, sweep range, etc. of the modulation frequency by controlling the modulator 22.

[0035] The control unit 31 controls the pulsating unit 24 to generate the pump light L P The pulse interval of the pump light L P The modulation frequency is swept as described above, and the pump light L modulated with different modulation frequencies is sent to the optical fiber FUT at different intervals. P are sequentially sent to the optical fiber FUT at set pulse intervals. In addition, the control unit 31 controls the pulsing unit 24 to set the pulse intensity, pulse width, etc. of the pump light LP.

[0036] The control unit 31 controls the pump light L PThe transmission interval of the pump light L is set to be longer than the measurement waiting time. P is the time required for the pump light L to travel back and forth. P The reason for setting the transmission interval longer than the measurement waiting time is to prevent measurement errors due to crosstalk, etc., which may occur when Brillouin scattered light generated at different positions corresponding to different correlation peaks is received simultaneously.

[0037] In this embodiment, the control unit 31 controls the switches SW of the fiber device 1 to select, from among the multiple segments FS, a segment FS that is optically connected to the measurement device 2. For example, the control unit 31 transmits control signals to each of the switches SW12, SW23, and SW34. Each switch SW is individually controlled. The spectrum of the Brillouin scattered light generated in the selected segment FS is measured.

[0038] It should be noted that the above-mentioned measurement waiting time changes depending on the overall length of the selected segment FS (hereinafter also referred to as the "selected segment length"). The longer the selected segment length, the longer the measurement waiting time. The shorter the selected segment length, the shorter the measurement waiting time.

[0039] In one embodiment, the control unit 31 controls the pump light L P For example, the control unit 31 sets the transmission interval of the pump light L so that the transmission interval becomes shorter as the selected segment length becomes shorter. P The shorter the transmission interval, the shorter the time required to measure the distribution characteristics. Hereinafter, the time required to measure the distribution characteristics is also simply referred to as the "measurement time."

[0040] The control unit 31 may also set the sweep speed and sweep range of the modulation frequency according to the setting of the transmission interval. For example, the control unit 31 may increase the sweep speed or narrow the sweep range as the transmission interval becomes shorter. The measurement time can be shortened by increasing the sweep speed or narrowing the sweep range.

[0041] 2 is a diagram showing an example of settings by the control unit. When only the segment FS1 is selected, the control unit 31 controls the switch SW12 so that the segment FS1 and the terminator T1 are optically connected by the switch SW12. The switches SW23 and SW34 may be controlled arbitrarily. The pump light L P The transmission interval of the pump light L is set to the first transmission interval. The first transmission interval is the measurement waiting time corresponding to the segment FS1, i.e., P is set within a range not less than the time required to travel round trip through the segment FS (for example, as short as possible).

[0042] When the segments FS1 and FS2 are selected, the switch SW12 is controlled so that the segments FS1 and FS2 are optically connected. The switch SW23 is controlled so that the segment FS2 is optically connected to the terminator T2. The switch SW34 is controlled arbitrarily. P The transmission interval of the segment FS1 is set to the second transmission interval. The second transmission interval is set within a range not shorter than the measurement waiting time corresponding to the segment FS1 and the segment FS2.

[0043] When segments FS1 to FS3 are selected, switch SW12 is controlled so that segments FS1 and FS2 are optically connected. Switch SW23 is controlled so that segments FS2 and FS3 are optically connected. Switch SW34 is controlled so that segment FS3 is optically connected to terminator T3. Pump light L PThe transmission interval of the segment FS1 to the segment FS3 is set to the third transmission interval. The third transmission interval is set within a range not shorter than the measurement waiting time corresponding to the segment FS1 to the segment FS3.

[0044] When segments FS1 to FS4 are selected, switch SW12 is controlled so that segments FS1 and FS2 are optically connected. Switch SW23 is controlled so that segments FS2 and FS3 are optically connected. Switch SW34 is controlled so that segments FS3 and FS4 are optically connected. Pump light L P The transmission interval of segment FS1 to segment FS4 is set to a fourth transmission interval. The fourth transmission interval is set within a range not shorter than the measurement waiting time corresponding to segments FS1 to FS4.

[0045] Comparing the first to fourth transmission intervals, the third transmission interval is shorter than the fourth transmission interval. Therefore, by selecting only segments FS1 to FS3, the measurement time can be shortened compared to the case of selecting segments FS1 to FS4 (i.e., the entire optical fiber FUT). The second transmission interval is shorter than the third transmission interval. Therefore, by selecting only segments FS1 and FS2, the measurement time can be shortened compared to the case of selecting segments FS1 to FS3. The first transmission interval is shorter than the second transmission interval. Therefore, by selecting only segment FS1, the measurement time can be shortened compared to the case of selecting segments FS1 and FS2.

[0046] Returning to FIG. 1, the control unit 31 may display information on the operation of the measurement device 2 to the user or accept user operations by controlling an operation panel or display (not shown). The user operation may include input of information on the selection of the above-mentioned segment FS. For example, measurement position information is input. Examples of the measurement position information include information on the segment FS including the measurement position, position information in the optical fiber FUT (for example, the distance from the near end NE, etc.), etc. Information on a plurality of measurement positions (for example, the measurement range) may be input. The control unit 31 may select the segment FS as described above based on the input measurement position information. In addition, the control unit 31 causes the operation display unit to display the calculation result of the calculation unit 30, more specifically, the measurement result of the characteristics of the optical fiber FUT. The measurement result may be displayed together with the measurement position information. The above-mentioned operation panel or display may be provided in the measurement device 2, or may be provided in an external device communicably connected to the measurement device 2 via a network (not shown) or the like.

[0047] For example, the characteristics of the optical fiber FUT are measured in the above manner. Note that the configuration of the measurement device 2 shown in Fig. 1 is merely an example. For example, amplifiers, filters, etc. (not shown) may be provided between some of the elements. Also, various known configurations may be adopted.

[0048] FIG. 3 is a flowchart showing an example of a process (measurement method) executed in the measurement system 100, more specifically, in the measurement device 2.

[0049] In step S1, measurement position information is input. For example, the control unit 31 accepts the operation position information via the operation display unit described above. In the following, a case where the measurement position indicated in the measurement position information is included in the segment FS2 will be described as an example.

[0050] In step S2, the switches are controlled to select a segment. The control unit 31 controls the switch SW to select the segment FS corresponding to the measurement position information input in the previous step S1. In this example, the switch SW12 and the switch SW23 are controlled so that the switch SW12 optically connects the segment FS1 and the segment FS2, and the switch SW23 optically connects the segment FS2 and the terminator T2. The segments FS1 and FS2 are selected.

[0051] In step S3, the transmission interval of the pump light and the like are set. The control unit 31 sets the transmission interval corresponding to the segment FS selected in the previous step S2 to the pump light L P The second transmission interval is set as the transmission interval of the pump light L P The transmission interval of the modulation frequency is set. The sweep speed and sweep range of the modulation frequency are also set.

[0052] In step S4, the spectrum of the Brillouin scattered light is measured, and the characteristics of the optical fiber are measured. The modulator 22 sweeps the modulation frequency at the set sweep speed and sweep range. The pulsing unit 24 pulses the pump light L at the transmission interval set in the previous step S3. P The spectrum analyzer 29 transmits the return light L S The spectrum of the Brillouin scattered light contained in the optical fiber FUT is measured. The calculation unit 30 calculates the amount of shift in the peak frequency at each measurement position based on the spectrum of the Brillouin scattered light measured by the spectrum analyzer 29. In other words, the distribution characteristics of the optical fiber FUT are measured.

[0053] For example, the characteristics of the optical fiber FUT are measured in the above manner. Although not shown in FIG.

[0054] Although one embodiment of the disclosed technology has been described above, the disclosed technology is not limited to the above embodiment. For example, in the above embodiment, the time gate BOCDR method has been described as an example.P A variety of other techniques may be used, including transmitting a signal to an optical fiber FUT and measuring the Brillouin scattered light. An example of another technique is the Brillouin Optical Time Domain Reflectometry (BOTDR) technique.

[0055] In the above embodiment, an example has been described in which the optical fiber FUT includes four segments FS, ie, segments FS1 to FS4. However, the number of segments FS is not limited to four. The number of segments FS may be any integer equal to or greater than two.

[0056] In the above embodiment, an example has been described in which each of the multiple segments FS is terminated by a terminator T. However, the multiple segments FS do not have to be terminated, and in that case, the terminator T may not be required.

[0057] The techniques described above can be specified, for example, as follows. One of the techniques disclosed is a measurement system. As described with reference to Figs. 1 to 3, the measurement system 100 includes an optical fiber FUT, a measurement device 2, and a switch SW. The optical fiber FUT includes a plurality of segments FS partitioned in the longitudinal direction. The measurement device 2 transmits pulsed pump light L P to the optical fiber FUT, and measures the spectrum of the Brillouin scattered light generated in the optical fiber FUT. The switch SW is provided between adjacent segments FS of the multiple segments FS, and optically connects or disconnects the adjacent segments FS. Measurement by the measurement device 2 includes controlling the switch SW to select, from the multiple segments FS, a segment FS that is to be optically connected to the measurement device 2 (step S2), and measuring the spectrum of the Brillouin scattered light generated in the selected segment FS (step S4).

[0058] In the above-described measurement system 100, a segment FS optically connected to the measurement device 2 is selected, and the spectrum of the Brillouin scattered light generated within the selected segment FS is measured. By optically connecting only some of the segments FS to the measurement device 2, the length of the portion of the optical fiber FUT optically connected to the measurement device 2 can be made shorter than when all segments FS, i.e., the entire optical fiber FUT, are optically connected to the measurement device 2. Therefore, the time required to measure the characteristics of the optical fiber can be shortened.

[0059] The measurement device 2 measures the pump light L according to the total length of the selected segment FS (selected segment length). P In this case, the measurement device 2 may set the transmission interval so that the transmission interval becomes shorter as the selected segment length becomes shorter. P The shorter the transmission interval, the shorter the measurement time can be.

[0060] The switch SW may separate adjacent segments FS from each other by optically terminating the segment FS on the side of the measuring device 2. For example, the adjacent segments FS can be optically separated from each other in this manner.

[0061] The measurement method described with reference to FIG. 3 and the like is also one of the techniques disclosed. Pto the optical fiber FUT and measuring the spectrum of the Brillouin scattered light generated in the optical fiber FUT (step S4). The optical fiber FUT includes a plurality of segments FS partitioned in the longitudinal direction. Between adjacent segments FS of the plurality of segments FS, a switch SW is provided for optically connecting or disconnecting the adjacent segments FS. The measuring includes controlling the switch SW to select, from the plurality of segments FS, a segment FS to be optically connected to the measuring device 2 (step S2), and measuring the spectrum of the Brillouin scattered light generated in the selected segment FS (step S4). As explained above, this measuring method can also shorten the time required to measure the characteristics of an optical fiber. [Explanation of symbols]

[0062] 100 Measurement System 1 Fiber Device 2. Measuring Equipment 21 Light source 22 Modulator 23 Coupler 24 Pulse generator 25 Delay Unit 26 Circulator 27 Terminal 28 Mixer 29 Spectrum Analyzer 30 Calculation section 31 Control Unit FUT Fiber Optic FS Segment SW Switch

Claims

1. an optical fiber including a plurality of segments partitioned in a longitudinal direction; a measurement device that transmits pulsed pump light into the optical fiber and measures the spectrum of Brillouin scattered light generated within the optical fiber; a switch provided between adjacent segments among the plurality of segments, the switch optically connecting or disconnecting the adjacent segments; A measurement system comprising: The measurement by the measuring device includes: selecting a segment from the plurality of segments to be optically connected to the measurement device by controlling the switch; measuring a spectrum of the Brillouin scattered light generated within the selected segment; Including, the switch optically terminates the segment on the measuring device side to thereby separate the adjacent segments from each other; Measurement system.

2. the measurement device sets an interval for transmitting the pump light to the optical fiber in accordance with the total length of the selected segment. The measurement system of claim 1 .

3. the measurement device sets the delivery interval such that the delivery interval decreases as the overall length of the segment decreases. The measurement system of claim 2 .

4. 1. A measurement method comprising: transmitting pulsed pump light into an optical fiber; and measuring a spectrum of Brillouin scattered light generated in the optical fiber, The optical fiber includes a plurality of segments partitioned in a longitudinal direction, A switch is provided between adjacent segments among the plurality of segments to optically connect or disconnect the adjacent segments, The measuring step comprises: selecting a segment from the plurality of segments to be connected to a measurement device by controlling the switch; measuring a spectrum of the Brillouin scattered light generated within the selected segment; Including, the switch optically terminates the segment on the measuring device side to thereby separate the adjacent segments from each other; Measurement method.

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