Optical fiber characteristic measurement device

Abstract

To provide an optical fiber characteristic measurement device capable of improving measurement accuracy.SOLUTION: An optical fiber characteristic measurement device 10 according to the present disclosure measures characteristics of an optical fiber. The optical fiber characteristic measurement device 10 includes a laser light source module 11 for outputting frequency-modulated laser light. The laser light source module 11 includes: a laser light source 110 for outputting laser light; a laser light source driver 111 for modulating a frequency of the laser light outputted by the laser light source 110; and an optical amplifier 116 for adjusting amplitude of the frequency-modulated laser light outputted by the laser light source 110 so as to cancel an amplitude modulation occurring in the frequency-modulated laser light outputted by the laser light source 110.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an optical fiber characteristic measuring device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, as an optical fiber characteristic measuring device, an optical fiber characteristic measuring device that measures the characteristics of an optical fiber by a Brillouin Optical Correlation Domain Reflectometry (BOCDR) method is known.

[0003] An optical fiber characteristic measuring device using the BOCDR method can measure the temperature and strain at each position of an optical fiber by measuring the scattered light due to Brillouin scattering and measuring the Brillouin Frequency Shift (BFS).

[0004] For example, Patent Document 1 discloses an optical fiber characteristics measuring device that is a BOCDR type optical fiber characteristics measuring device that can reduce the time required to measure the characteristics of an optical fiber. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6773091 Summary of the Invention [Problem to be solved by the invention]

[0006] An optical fiber characteristic measuring device normally irradiates a frequency-modulated laser beam into the optical fiber to be measured.

[0007] When a laser beam is frequency modulated, the laser beam is also subjected to unintended amplitude modulation as a result. This amplitude modulation becomes noise, which is an obstacle to improving the measurement accuracy of optical fiber characteristic measuring devices.

[0008] Therefore, an object of the present disclosure is to provide an optical fiber characteristic measuring device capable of improving measurement accuracy. [Means for solving the problem]

[0009] An optical fiber characteristic measuring device according to some embodiments is an optical fiber characteristic measuring device for measuring characteristics of an optical fiber, and includes a laser light source module that outputs a frequency-modulated laser light, the laser light source module including a laser light source that outputs a laser light, a laser light source driver that frequency-modulates the laser light output by the laser light source, and an optical amplifier that adjusts the amplitude of the frequency-modulated laser light output by the laser light source so as to cancel the amplitude modulation generated in the frequency-modulated laser light output by the laser light source. Such an optical fiber characteristic measuring device can improve measurement accuracy.

[0010] In an optical fiber characteristic measuring device according to an embodiment, the laser light source module may further include a signal generator that generates a first sine wave used when the laser light source driver frequency-modulates the laser light output from the laser light source and a second sine wave having a frequency equal to that of the first sine wave, a phase shifter that delays the phase of the second sine wave in accordance with the frequency of the first sine wave, and an optical amplifier driver that drives the optical amplifier with the second sine wave delayed by the phase shifter to adjust the amplitude of the frequency-modulated laser light output from the laser light source. This allows the optical fiber characteristic measuring device to accurately cancel amplitude modulation that occurs unintentionally during frequency modulation.

[0011] In one embodiment of the optical fiber characteristic measuring device, the laser light source module may further include a variable amplifier that amplifies an amplitude of the second sine wave according to an amplitude of the first sine wave and outputs the amplified amplitude to the phase shifter, whereby the optical fiber characteristic measuring device can accurately cancel amplitude modulation that occurs unintentionally during frequency modulation.

[0012] In an optical fiber characteristic measuring device according to an embodiment, the laser light source module may further include a first signal generator that generates a first sine wave used when the laser light source driver frequency-modulates the laser light output from the laser light source, a second signal generator that generates a second sine wave having a frequency equal to that of the first sine wave and delayed according to the frequency of the first sine wave, and an optical amplifier driver that drives the optical amplifier with the second sine wave to adjust the amplitude of the frequency-modulated laser light output from the laser light source. This allows the optical fiber characteristic measuring device to accurately cancel amplitude modulation that occurs unintentionally during frequency modulation.

[0013] In one embodiment, the amplitude of the second sine wave generated by the second signal generator may be amplified according to the amplitude of the first sine wave, thereby enabling the optical fiber characteristic measurement device to accurately cancel amplitude modulation that occurs unintentionally during frequency modulation.

[0014] In one embodiment, the optical fiber characteristic measuring device measures the characteristics of the optical fiber by a Brillouin optical correlation domain reflectometer method, and the optical fiber characteristic measuring device may include a first optical coupler that splits the frequency-modulated laser light into pump light and reference light, and a second optical coupler that combines the reference light and scattered light from the optical fiber to be measured, which is generated when the pump light is input into the optical fiber.

[0015] In one embodiment, the optical fiber characteristic measuring device measures the characteristics of the optical fiber by a Brillouin optical correlation domain analysis method, and the optical fiber characteristic measuring device may include a first optical coupler that splits the frequency-modulated laser light into pump light and probe light, and a circulator that extracts the probe light and scattered light from the optical fiber that is a measurement target when the pump light is incident on the optical fiber. Effect of the Invention

[0016] According to the present disclosure, it is possible to provide an optical fiber characteristic measuring device capable of improving measurement accuracy. [Brief description of the drawings]

[0017] [Figure 1] 1 is a diagram showing a schematic configuration of an optical fiber characteristic measuring device according to an embodiment; [Diagram 2] FIG. 13 is a diagram showing a schematic configuration of an optical fiber characteristic measuring device according to a modified example. [Diagram 3] FIG. 1 is a diagram showing a schematic configuration of an optical fiber characteristic measuring device according to a comparative example. [Figure 4] FIG. 1 is a diagram showing a schematic configuration of an optical fiber characteristic measuring device according to a BOCDA method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0019] 1 is a diagram showing a schematic configuration of an optical fiber characteristic measuring apparatus 10 according to one embodiment. The optical fiber characteristic measuring apparatus 10 is an apparatus that measures the characteristics of an optical fiber 1 to be measured by a Brillouin optical correlation domain reflectometer (BOCDR) method.

[0020] The optical fiber characteristic measuring device 10 includes a laser light source module 11, a first optical coupler 12, an optical switch 13, a delay fiber 14, a polarization scrambler 15, a circulator 16, a scattered light amplifier 17, a second optical coupler 18, a photodiode 19, an RF (Radio Frequency) signal amplifier 20, and a frequency analyzer 21.

[0021] The laser light source module 11 outputs a frequency-modulated laser light to the first optical coupler 12 .

[0022] The laser light source module 11 includes a laser light source 110, a laser light source driver 111, a signal generator 112, a variable amplifier 113, a phase shifter 114, an optical amplifier driver 115, and an optical amplifier .

[0023] The laser light source 110 outputs a laser beam to the optical amplifier 116. The laser light source 110 may be, for example, a laser diode. The laser light source 110 is capable of outputting a frequency-modulated laser beam. The laser light output by the laser light source 110 is frequency-modulated by a laser light source driver 111.

[0024] The laser light source driver 111 frequency-modulates the laser light output by the laser light source 110. The laser light source driver 111 can frequency-modulate the laser light output by the laser light source 110 by controlling the current flowing through the laser light source 110.

[0025] The laser light source driver 111 uses a sine wave supplied from a signal generator 112 to frequency-modulate the laser light output from the laser light source 110 .

[0026] The laser light source driver 111 may be a circuit of any configuration capable of frequency-modulating the laser light output by the laser light source 110 .

[0027] The signal generator 112 outputs a first sine wave and a second sine wave having the same frequency and synchronized phases. The signal generator 112 outputs the first sine wave to the laser light source driver 111. The signal generator 112 outputs the second sine wave to the variable amplifier 113.

[0028] The signal generator 112 may be any configuration of signal generator capable of outputting two sine waves.

[0029] Variable amplifier 113 amplifies the amplitude of the second sine wave supplied from signal generator 112 in accordance with the amplitude of the first sine wave, and outputs the amplified amplitude to phase shifter 114. When the amplitude of the first sine wave is large, variable amplifier 113 amplifies the amplitude of the second sine wave by a large amount, and when the amplitude of the first sine wave is small, variable amplifier 113 amplifies the amplitude of the second sine wave by a small amount.

[0030] The variable amplifier 113 may be a variable amplifier of any configuration capable of amplifying the amplitude of the second sine wave.

[0031] Phase shifter 114 delays the phase of the second sine wave supplied from variable amplifier 113 in accordance with the frequency of the first sine wave, and outputs the delayed phase to optical amplifier driver 115. Phase shifter 114 delays the phase of the second sine wave by a large amount when the frequency of the first sine wave is high, and delays the phase of the second sine wave by a small amount when the frequency of the first sine wave is low.

[0032] Phase shifter 114 may be any configuration of phase shifter capable of delaying the phase of the second sine wave.

[0033] The optical amplifier driver 115 drives the optical amplifier 116 with the second sine wave delayed by the phase shifter 114 to adjust the amplitude of the frequency-modulated laser light output from the laser light source 110 to the optical amplifier 116 .

[0034] The optical amplifier driver 115 may be a circuit of any configuration capable of adjusting the amplitude of the laser light supplied to the optical amplifier 116 .

[0035] The optical amplifier 116 adjusts the amplitude of the frequency-modulated laser light output by the laser light source 110 so as to cancel the amplitude modulation occurring in the frequency-modulated laser light output by the laser light source 110 .

[0036] Here, a description will be given of the frequency-modulated laser light outputted from the laser light source 110. The laser light outputted from the laser light source 110 is frequency-modulated by the laser light source driver 111, but during the frequency modulation, unintended amplitude modulation also occurs as a result.

[0037] Since this amplitude modulation is unintentional, it is desirable to cancel it. If this amplitude modulation is canceled, the laser light output from the laser light source module 11 will be a laser light that has only been frequency modulated and not amplitude modulated.

[0038] The optical amplifier 116 is driven by the optical amplifier driver 115 to adjust the amplitude of the frequency-modulated laser light output by the laser light source 110 so as to cancel the amplitude modulation that occurs in the frequency-modulated laser light output by the laser light source 110.

[0039] At this time, the phase shifter 114 delays the phase of the second sine wave by a predetermined phase from the phase of the first sine wave so as to cancel the amplitude modulation occurring in the frequency-modulated laser light output by the laser light source 110. As a result, the amplitude of the frequency-modulated laser light output by the laser light source 110 can be amplitude-modulated with a phase delayed by a predetermined phase from the phase of the first sine wave, so that the laser light source module 11 can cancel the amplitude modulation occurring unintentionally in the laser light. The predetermined phase depends on the frequency of the first sine wave. Therefore, the laser light source module 11 may hold a table in which the frequency of the first sine wave is associated with the predetermined phase. The table may be a table created based on the actual measurement result of the phase that can cancel the amplitude modulation. The laser light source module 11 may delay the phase of the second sine wave by a predetermined phase from the phase of the first sine wave based on the table.

[0040] The frequency-modulated laser light output by the laser light source 110 is frequency-modulated with a delay from the phase of the first sine wave by a predetermined amount, and this predetermined amount is larger as the frequency of the first sine wave is higher. Therefore, the phase shifter 114 delays the phase of the second sine wave by a larger amount as the frequency of the first sine wave is higher. The relationship between the frequency of the first sine wave and the predetermined amount may be measured in advance by actual measurement. The phase shifter 114 delays the phase of the second sine wave according to the frequency of the first sine wave based on the actual measurement value measured in advance.

[0041] The optical amplifier 116 outputs the frequency-modulated laser light to the first optical coupler 12. The laser light output from the optical amplifier 116 is a laser light in which the amplitude modulation has been cancelled and only the frequency modulation has been performed.

[0042] The first optical coupler 12 splits the laser light supplied from the laser light source module 11 into pump light and reference light. The first optical coupler 12 outputs the pump light to the optical switch 13. The first optical coupler 12 outputs the reference light to the second optical coupler 18.

[0043] The optical switch 13 chops the pump light supplied from the first optical coupler 12 to generate pulsed light. The optical switch 13 outputs the pulsed pump light to a delay fiber .

[0044] The delay fiber 14 delays the pulsed light supplied from the optical switch 13 and outputs it to the polarization scrambler 15 .

[0045] The polarization scrambler 15 changes the polarization state of the pulsed light supplied from the delay fiber 14 to unpolarized light and outputs it to the circulator 16 .

[0046] The circulator 16 inputs the pulsed light supplied from the polarization scrambler 15 into the optical fiber 1 to be measured. When the pulsed light is input into the optical fiber 1, the optical fiber 1 generates Brillouin scattered light. The circulator 16 outputs the Brillouin scattered light input from the optical fiber 1 to the scattered light amplifier 17.

[0047] The scattered light amplifier 17 amplifies the Brillouin scattered light supplied from the circulator 16 and outputs the amplified light to a second optical coupler 18. The scattered light amplifier 17 may be, for example, an Erbium Doped Fiber Amplifier (EDFA).

[0048] The second optical coupler 18 combines the Brillouin scattered light supplied from the scattered light amplifier 17 with the reference light supplied from the first optical coupler 12 , and outputs the combined light to the photodiode 19 .

[0049] The photodiode 19 receives the combined light supplied from the second optical coupler 18 and performs heterodyne detection. The photodiode 19 converts the received light into an electrical signal and outputs it to the RF signal amplifier 20.

[0050] The RF signal amplifier 20 amplifies the electrical signal supplied from the photodiode 19 and outputs it to a frequency analyzer 21 .

[0051] The frequency analyzer 21 performs frequency analysis on the electrical signal supplied from the RF signal amplifier 20, that is, the electrical signal corresponding to the light multiplexed by the second optical coupler 18.

[0052] The electrical signal supplied to the frequency analyzer 21 from the RF signal amplifier 20 includes a Brillouin gain spectrum due to Brillouin scattered light. The Brillouin gain spectrum includes a frequency component of approximately 11 GHz.

[0053] The frequency analyzer 21 measures the Brillouin frequency shift, which is the amount of shift of the peak of the Brillouin gain spectrum.

[0054] Since the Brillouin frequency shift depends linearly on the temperature and strain of the optical fiber 1, the frequency analyzer 21 can measure the temperature and strain of the optical fiber 1 by measuring the Brillouin frequency shift.

[0055] Moreover, which position of the optical fiber 1 the characteristics are measured at depends on the frequency of the first sine wave generated by the signal generator 112. Therefore, the optical fiber characteristic measuring device 10 can sweep the measurement position of the optical fiber 1 by sweeping the frequency of the first sine wave generated by the signal generator 112. Therefore, the optical fiber characteristic measuring device 10 can measure the temperature and strain at each position of the optical fiber 1 by sweeping the frequency of the first sine wave. In other words, the optical fiber characteristic measuring device 10 can measure the distribution of temperature and strain in the optical fiber 1 by sweeping the frequency of the first sine wave.

[0056] Furthermore, the spatial resolution when measuring the characteristics of the optical fiber 1 depends on the amplitude of the first sine wave generated by the signal generator 112. Therefore, the optical fiber characteristic measuring device 10 can adjust the spatial resolution when measuring the characteristics of the optical fiber 1 by adjusting the amplitude of the first sine wave generated by the signal generator 112.

[0057] According to the optical fiber characteristic measuring device 10 of the embodiment as described above, it is possible to improve the measurement accuracy. More specifically, the laser light source module 11 includes a laser light source 110 that outputs a laser beam, a laser light source driver 111 that frequency-modulates the laser beam output by the laser light source 110, and an optical amplifier 116 that adjusts the amplitude of the frequency-modulated laser beam output by the laser light source 110 so as to cancel the amplitude modulation that occurs in the frequency-modulated laser beam output by the laser light source 110. In this way, the laser light source module 11 can cancel the amplitude modulation that is unintentionally generated when the laser light source driver 111 frequency-modulates the laser beam by the optical amplifier 116 adjusting the amplitude. As a result, the laser beam output by the laser light source module 11 is a laser beam that is only frequency-modulated and not amplitude-modulated. Therefore, the optical fiber characteristic measuring device 10 of the embodiment can input the laser beam that is only frequency-modulated into the optical fiber 1 to be measured, and can improve the measurement accuracy of measuring the Brillouin frequency shift.

[0058] (Modification) 2 is a diagram showing a schematic configuration of an optical fiber characteristic measuring apparatus 10a according to a modified example The optical fiber characteristic measuring apparatus 10a according to the modified example will be described with reference to FIG.

[0059] The optical fiber characteristic measuring device 10a of the modified example includes a laser light source module 11a, a first optical coupler 12, an optical switch 13, a delay fiber 14, a polarization scrambler 15, a circulator 16, a scattered light amplifier 17, a second optical coupler 18, a photodiode 19, an RF signal amplifier 20, and a frequency analyzer 21.

[0060] A laser light source module 11a of an optical fiber characteristic measuring apparatus 10a according to the modified example includes a laser light source 110, a laser light source driver 111, an optical amplifier driver 115, an optical amplifier 116, a first signal generator 117, and a second signal generator 118.

[0061] The optical fiber characteristic measuring apparatus 10a according to the modified example differs from the optical fiber characteristic measuring apparatus 10 shown in Fig. 1 in that the laser light source module 11a includes two signal generators, a first signal generator 117 and a second signal generator 118. The laser light source module 11 of the optical fiber characteristic measuring apparatus 10 shown in Fig. 1 includes only one signal generator 112.

[0062] Regarding the optical fiber characteristic measuring apparatus 10a relating to the modified example, the differences from the optical fiber characteristic measuring apparatus 10 shown in FIG. 1 will be mainly described, and descriptions of the points in common or similar to the optical fiber characteristic measuring apparatus 10 shown in FIG. 1 will be omitted as appropriate.

[0063] The first signal generator 117 outputs a first sine wave to the laser light source driver 111. The laser light source driver 111 uses the first sine wave supplied from the first signal generator 117 to frequency-modulate the laser light output by the laser light source 110.

[0064] The second signal generator 118 outputs a second sine wave to the optical amplifier driver 115. The frequency of the second sine wave is equal to the frequency of the first sine wave.

[0065] The second signal generator 118 delays the phase of the second sine wave in accordance with the frequency of the first sine wave. When the frequency of the first sine wave is high, the second signal generator 118 delays the phase of the second sine wave by a large amount, and when the frequency of the first sine wave is low, the second signal generator 118 delays the phase of the second sine wave by a small amount.

[0066] The second signal generator 118 amplifies the amplitude of the second sine wave in accordance with the amplitude of the first sine wave. When the amplitude of the first sine wave is large, the second signal generator 118 amplifies the amplitude of the second sine wave by a large amount, and when the amplitude of the first sine wave is small, the second signal generator 118 amplifies the amplitude of the second sine wave by a small amount.

[0067] The optical amplifier driver 115 drives the optical amplifier 116 with a second sine wave supplied from a second signal generator 118 to adjust the amplitude of the frequency-modulated laser light output from the laser light source 110 to the optical amplifier 116 .

[0068] The optical amplifier 116 adjusts the amplitude of the frequency-modulated laser light output by the laser light source 110 so as to cancel the amplitude modulation occurring in the frequency-modulated laser light output by the laser light source 110 .

[0069] In the optical fiber characteristic measuring device 10a according to the modified example, the laser light source module 11a can cancel the amplitude modulation that is unintentionally generated when the laser light source driver 111 frequency-modulates the laser light by adjusting the amplitude with the optical amplifier 116. Therefore, the optical fiber characteristic measuring device 10a according to the modified example can also input the laser light that is only frequency-modulated into the optical fiber 1 to be measured, thereby improving the measurement accuracy of measuring the Brillouin frequency shift.

[0070] (Comparative Example) 3 is a diagram showing a schematic configuration of an optical fiber characteristic measuring apparatus 200 according to a comparative example. The optical fiber characteristic measuring apparatus 200 according to the comparative example will be described with reference to FIG.

[0071] The laser light source module 210 of the optical fiber characteristic measuring apparatus 200 according to the comparative example includes a laser light source 110, a laser light source driver 111, and a signal generator 112.

[0072] That is, the laser light source module 210 of the optical fiber characteristic measuring apparatus 200 according to the comparative example is significantly different from the laser light source module 11 of the optical fiber characteristic measuring apparatus 10 shown in FIG.

[0073] In the laser light source module 210 of the optical fiber characteristic measuring device 200 of the comparative example, the laser light output by the laser light source 110 is frequency modulated by the laser light source driver 111, and the frequency-modulated laser light is output as is to the first optical coupler 12.

[0074] Therefore, the laser light that has also been unintentionally amplitude modulated during frequency modulation is output as is to the first optical coupler 12. Since this amplitude modulation becomes noise, the measurement accuracy of the optical fiber characteristic measuring device 200 according to the comparative example deteriorates by the amount of noise caused by the amplitude modulation.

[0075] It is obvious to those skilled in the art that the present disclosure can be realized in other specific forms other than the above-described embodiments without departing from the spirit or essential characteristics thereof. Therefore, the above description is illustrative and not limiting. The scope of the disclosure is defined by the appended claims, not by the above description. Any modifications within the scope of the equivalents of all modifications are included therein.

[0076] For example, the arrangement and number of each component described above are not limited to the above description and the contents illustrated in the drawings. The arrangement and number of each component may be arbitrarily configured as long as the function can be realized.

[0077] For example, the optical fiber characteristic measuring device 10 and the optical fiber characteristic measuring device 10a have been described as measuring the characteristics of the optical fiber by the BOCDR method, but the optical fiber characteristic measuring device 10 and the optical fiber characteristic measuring device 10a may also measure the characteristics of the optical fiber by the Brillouin Optical Correlation Domain Analysis (BOCDA) method.

[0078] FIG. 4 shows an example of a schematic configuration of an optical fiber characteristic measuring device 30 in the case of the BOCDA method. The optical fiber characteristic measuring device 30 includes a laser light source module 11, a first optical coupler 31, an SSB modulator 32, a delay fiber 33, an isolator 34, an optical switch 35, an optical amplifier 36, a circulator 37, a photodiode 38, an LIA 39, and a personal computer (PC) 40. The laser light source module 11 is the same as the laser light source module 11 shown in FIG. 1. The optical fiber characteristic measuring device 30 shown in FIG. 4 may include the laser light source module 11a shown in FIG. 2 instead of the laser light source module 11. The first optical coupler 31 splits the laser light supplied from the laser light source module 11 into pump light and probe light. The circulator 37 extracts scattered light from the optical fiber 1 generated when the pump light is incident on the optical fiber 1 to be measured, and the probe light.

[0079] In addition, for example, the optical fiber characteristic measuring device 10 and the optical fiber characteristic measuring device 10a have been described as measuring the characteristics of an optical fiber by the BOCDR method, but the optical fiber characteristic measuring device 10 and the optical fiber characteristic measuring device 10a may measure the characteristics of an optical fiber by the optical correlation domain reflectometry (OCDR) method that measures Rayleigh scattering. When measuring the characteristics of an optical fiber by the OCDR method, an acousto-optic modulator may be inserted on the reference light or pump light side to perform heterodyne measurement.

[0080] For example, in the above-mentioned embodiment, the optical fiber characteristic measuring device 10 and the optical fiber characteristic measuring device 10a have been described as performing heterodyne detection, but the optical fiber characteristic measuring device 10 and the optical fiber characteristic measuring device 10a may perform homodyne detection. When performing homodyne detection, the optical fiber characteristic measuring device 10 and the optical fiber characteristic measuring device 10a may include an SSB (Single Side-Band) modulator between the first optical coupler 12 and the second optical coupler 18. Alternatively, the optical fiber characteristic measuring device 10 and the optical fiber characteristic measuring device 10a may include an SSB modulator between the first optical coupler 12 and the optical switch 13.

[0081] For example, in the above-mentioned embodiment, the optical fiber characteristic measuring device 10 and the optical fiber characteristic measuring device 10a are described as measuring the Brillouin frequency shift, but the present invention is not limited to this. The optical fiber characteristic measuring device 10 and the optical fiber characteristic measuring device 10a may detect a double wave component having a frequency twice the modulation frequency of the modulated light contained in the intensity component of each frequency of the Brillouin gain spectrum, and measure the characteristics of the optical fiber 1 based on the detected double wave component. In this case, the optical fiber characteristic measuring device 10 and the optical fiber characteristic measuring device 10a may perform heterodyne detection or homodyne detection.

[0082] For example, the amount of amplification of the variable amplifier 113 of the optical fiber characteristic measuring apparatus 10 shown in Fig. 1 may be manually adjustable. Also, the amount of phase delay applied by the phase shifter 114 of the optical fiber characteristic measuring apparatus 10 shown in Fig. 1 may be manually adjustable. [Explanation of symbols]

[0083] 1. Optical fiber 10, 10a Optical fiber characteristic measuring device 11, 11a Laser light source module 12 First optical coupler 13 Optical Switch 14 Delay Fiber 15 Polarization Scrambler 16 Circulator 17 Scattering Light Amplifier 18 Second optical coupler 19 Photodiode 20 RF Signal Amplifier 21 Frequency Analyzer 30 Optical fiber characteristic measuring device 31 First optical coupler 32 SSB Modulator 33 Delay Fiber 34 Isolator 35 Optical Switch 36 Optical Amplifier 37 Circulator 38 Photodiode 39 LIA 40 PC 110 Laser light source 111 Laser light source driver 112 Signal Generator 113 Variable Amplifier 114 Phase Shifter 115 Optical Amplifier Driver 116 Optical Amplifier 117 First Signal Generator 118 Second signal generator 200 Optical fiber characteristic measuring device 210 Laser Source Module

Claims

1. An optical fiber characteristic measuring device for measuring characteristics of an optical fiber, comprising: a laser light source module that outputs a frequency-modulated laser light; The laser light source module includes: A laser light source that outputs laser light; a laser light source driver that frequency-modulates the laser light output from the laser light source; an optical amplifier that adjusts the amplitude of the frequency-modulated laser light output from the laser light source so as to cancel the amplitude modulation generated in the frequency-modulated laser light output from the laser light source; An optical fiber characteristic measuring device comprising:

2. 2. The optical fiber characteristic measuring apparatus according to claim 1, The laser light source module includes: a signal generator that generates a first sine wave used when the laser light source driver frequency-modulates the laser light output from the laser light source, and a second sine wave having the same frequency as the first sine wave; a phase shifter that delays a phase of the second sine wave in accordance with a frequency of the first sine wave; an optical amplifier driver that drives the optical amplifier with the second sine wave delayed by the phase shifter to adjust the amplitude of the frequency-modulated laser light output from the laser light source; The optical fiber characteristic measuring device further comprises:

3. 3. The optical fiber characteristic measuring apparatus according to claim 2, the laser light source module further comprises a variable amplifier that amplifies the amplitude of the second sine wave in accordance with the amplitude of the first sine wave and outputs the amplified second sine wave to the phase shifter.

4. 2. The optical fiber characteristic measuring apparatus according to claim 1, The laser light source module includes: a first signal generator that generates a first sine wave used when the laser light source driver frequency-modulates the laser light output from the laser light source; a second signal generator for generating a second sine wave having a frequency equal to that of the first sine wave and delayed in accordance with the frequency of the first sine wave; an optical amplifier driver that drives the optical amplifier with the second sine wave to adjust the amplitude of the frequency-modulated laser light output from the laser light source; The optical fiber characteristic measuring device further comprises:

5. 5. The optical fiber characteristic measuring apparatus according to claim 4, an amplitude of the second sine wave generated by the second signal generator being amplified according to the amplitude of the first sine wave;

6. 2. The optical fiber characteristic measuring apparatus according to claim 1, the optical fiber characteristic measuring device measures the characteristics of the optical fiber by a Brillouin optical correlation domain reflectometer method; The optical fiber characteristic measuring device comprises: a first optical coupler that splits the frequency-modulated laser light into a pump light and a reference light; a second optical coupler that combines the reference light with scattered light from an optical fiber that is a measurement target when the pump light is incident on the optical fiber; An optical fiber characteristic measuring device comprising:

7. 2. The optical fiber characteristic measuring apparatus according to claim 1, the optical fiber characteristic measuring device measures the characteristics of the optical fiber by a Brillouin optical correlation domain analysis method; The optical fiber characteristic measuring device comprises: a first optical coupler that splits the frequency-modulated laser light into a pump light and a probe light; a circulator for extracting scattered light from an optical fiber to be measured, the scattered light being generated when the pump light is incident on the optical fiber, and the probe light; An optical fiber characteristic measuring device comprising:

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