Optical fiber characteristic measuring device

Abstract

Provided is an optical fiber characteristic measurement device capable of improving measurement accuracy. This optical fiber characteristic measurement device (10) measures the characteristics of an optical fiber. An optical fiber characteristic measurement device (10) is provided with a laser light source module (11) that outputs frequency-modulated laser light. A laser light source module (11) is provided with: a laser light source (110) that outputs laser light; a laser light source driver (111) that modulates the frequency of the laser light output by the laser light source (110); and an optical amplifier (116) that adjusts the amplitude of the frequency-modulated laser light output by the laser light source (110) so as to cancel amplitude modulation generated by the frequency-modulated laser light output by the laser light source (110).

Description

Technical Field

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

[0002] Currently, as an optical fiber characteristic measuring device, there is known an optical fiber characteristic measuring device that measures the optical fiber characteristics by a Brillouin Optical Correlation Domain Reflectometry (BOCDR) method.

[0003] The BOCDR optical fiber characteristic measuring apparatus measures scattered light due to Brillouin scattering and measures the Brillouin frequency shift (BFS), thereby being able to measure the temperature and strain at various positions of the optical fiber.

[0004] For example, as a BOCDR-based optical fiber characteristic measurement device, Patent Document 1 discloses an optical fiber characteristic measurement device that can shorten the time required for measuring optical fiber characteristics.

[0005] Patent Document 1: Japanese Patent No. 6773091

[0006] An optical fiber characteristic measuring apparatus generally allows frequency-modulated laser light to be emitted into an optical fiber to be measured.

[0007] If the laser light is frequency modulated, the laser light is also amplitude modulated unexpectedly as a result. This amplitude modulation becomes noise and becomes an obstacle to improving the measurement accuracy of the optical fiber characteristic measurement device. Summary of the invention

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

[0009] Several embodiments of the optical fiber characteristic measuring device are optical fiber characteristic measuring devices for measuring the characteristics of an optical fiber, and include a laser source module for outputting a frequency-modulated laser, wherein the laser source module includes: a laser source for outputting laser light; a laser source driver for frequency-modulating the laser light outputted by the laser source; and an optical amplifier for adjusting the amplitude of the frequency-modulated laser light outputted by the laser source in a manner that eliminates the amplitude modulation generated by the frequency-modulated laser light outputted by the laser source. According to such an optical fiber characteristic measuring device, the measurement accuracy can be improved.

[0010] In one embodiment of the optical fiber characteristic measuring device, the laser source module may further include: a signal generator that generates a first sine wave used when the laser source driver performs frequency modulation on the laser output from the laser source, and a second sine wave having a frequency equal to 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 using the second sine wave delayed by the phase shifter to adjust the amplitude of the frequency-modulated laser output from the laser source. Thus, the optical fiber characteristic measuring device can eliminate amplitude modulation that is accidentally generated during frequency modulation with good accuracy.

[0011] In one embodiment of the optical fiber characteristic measuring device, the laser source module may further include 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 amplitude to the phase shifter. Thus, the optical fiber characteristic measuring device can eliminate the amplitude modulation that is accidentally generated during frequency modulation with good accuracy.

[0012] Based on the optical fiber characteristic measuring device involved in one embodiment, the laser source module can be formed so that the laser source module further includes: a first signal generator that generates a first sine wave used when the laser source driver performs frequency modulation on the laser output by the laser source; a second signal generator that generates a second sine wave whose frequency is equal to that of the first sine wave and is delayed by 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 laser output by the laser source after frequency modulation. In this way, the optical fiber characteristic measuring device can eliminate the amplitude modulation accidentally generated during frequency modulation with good accuracy.

[0013] In one embodiment of the optical fiber characteristic measuring device, the amplitude of the second sine wave generated by the second signal generator may be amplified in accordance with the amplitude of the first sine wave. Thus, the optical fiber characteristic measuring device can eliminate amplitude modulation accidentally generated during frequency modulation with good accuracy.

[0014] Based on an optical fiber characteristic measuring device involved in one embodiment, it can be formed that the optical fiber characteristic measuring device measures the characteristics of the optical fiber by using a Brillouin light correlation area reflectometer method, and the optical fiber characteristic measuring device comprises: a first optical coupler, which branches the frequency-modulated laser into pump light and reference light; and a second optical coupler, which combines the scattered light from the optical fiber and the reference light generated by the pump light being emitted into the optical fiber as a measurement object.

[0015] Based on an optical fiber characteristic measuring device involved in one embodiment, it can be formed that the optical fiber characteristic measuring device measures the characteristics of the optical fiber by using the Brillouin light correlation region analysis method, and the optical fiber characteristic measuring device has: a first optical coupler, which branches the frequency-modulated laser into pump light and probe light; and a circulator, which extracts the scattered light from the optical fiber and the probe light generated by injecting the pump light into the optical fiber as a measurement object.

[0016] Effects of the Invention

[0017] 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

[0018] Figure 1 It is a diagram showing a schematic configuration of an optical fiber characteristics measuring device according to one embodiment.

[0019] Figure 2 It is a diagram showing a schematic configuration of an optical fiber characteristics measuring device according to a modified example.

[0020] Figure 3 It is a diagram showing a schematic structure of an optical fiber characteristic measuring device according to a comparative example.

[0021] Figure 4 This is a diagram showing a schematic configuration of a BOCDA-based optical fiber characteristic measuring device. DETAILED DESCRIPTION

[0022] Hereinafter, one embodiment of the present disclosure will be described with reference to the drawings.

[0023] Figure 1 1 is a diagram showing a schematic configuration of an optical fiber characteristic measurement device 10 according to one embodiment. The optical fiber characteristic measurement device 10 is a device for measuring the characteristics of an optical fiber 1 as a measurement target by using a Brillouin optical correlation region reflectometer (BOCDR) method.

[0024] The optical fiber characteristic measuring device 10 has a laser 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.

[0025] The laser source module 11 outputs the frequency-modulated laser light to the first optical coupler 12 .

[0026] The laser source module 11 includes a laser source 110 , a laser source driver 111 , a signal generator 112 , a variable amplifier 113 , a phase shifter 114 , an optical amplifier driver 115 , and an optical amplifier 116 .

[0027] The laser source 110 outputs laser light to the optical amplifier 116 . The laser source 110 may be, for example, a laser diode. The laser source 110 can output frequency-modulated laser light. The laser light output by the laser source 110 is frequency-modulated by a laser source driver 111 .

[0028] The laser source driver 111 frequency-modulates the laser light outputted from the laser source 110 . The laser source driver 111 can frequency-modulate the laser light outputted from the laser source 110 by controlling the current flowing through the laser source 110 .

[0029] The laser source driver 111 frequency-modulates the laser light output from the laser source 110 using the sine wave supplied from the signal generator 112 .

[0030] The laser source driver 111 may be a circuit of any structure capable of frequency modulating the laser light outputted from the laser source 110 .

[0031] The signal generator 112 outputs a first sine wave and a second sine wave having equal frequencies and synchronized phases. The signal generator 112 outputs the first sine wave to the laser source driver 111. The signal generator 112 outputs the second sine wave to the variable amplifier 113.

[0032] The signal generator 112 may be a signal generator of any structure capable of outputting two sine waves.

[0033] The variable amplifier 113 amplifies the amplitude of the second sine wave supplied from the signal generator 112 according to the amplitude of the first sine wave, and outputs it to the phase shifter 114. When the amplitude of the first sine wave is large, the variable amplifier 113 greatly amplifies the amplitude of the second sine wave, and when the amplitude of the first sine wave is small, the variable amplifier 113 slightly amplifies the amplitude of the second sine wave.

[0034] The variable amplifier 113 may be a variable amplifier of any structure that can amplify the amplitude of the second sine wave.

[0035] The phase shifter 114 delays the phase of the second sine wave supplied from the variable amplifier 113 according to the frequency of the first sine wave, and outputs the delay to the optical amplifier driver 115. When the frequency of the first sine wave is high, the phase shifter 114 greatly delays the phase of the second sine wave, and when the frequency of the first sine wave is low, the phase shifter 114 slightly delays the phase of the second sine wave.

[0036] The phase shifter 114 may be a phase shifter of any structure that can delay the phase of the second sinusoidal wave.

[0037] The optical amplifier driver 115 drives the optical amplifier 116 using the second sine wave delayed by the phase shifter 114 , and the laser source 110 adjusts the amplitude of the frequency-modulated laser light output to the optical amplifier 116 .

[0038] The optical amplifier driver 115 may be a circuit of any structure capable of adjusting the amplitude of the laser light supplied to the optical amplifier 116 .

[0039] The optical amplifier 116 adjusts the amplitude of the frequency-modulated laser light outputted from the laser source 110 so as to cancel the amplitude modulation generated in the frequency-modulated laser light outputted from the laser source 110 .

[0040] Here, the frequency-modulated laser light outputted from the laser light source 110 will be described. The laser light outputted from the laser light source 110 is frequency-modulated by the laser light source driver 111, but the frequency modulation results in an unexpected amplitude modulation.

[0041] This amplitude modulation is unexpectedly generated, so it is preferable to eliminate it. If this amplitude modulation is eliminated, the laser light output by the laser light source module 11 becomes laser light that is only frequency modulated and not amplitude modulated.

[0042] The optical amplifier 116 is driven by the optical amplifier driver 115 to adjust the amplitude of the frequency-modulated laser light outputted from the laser light source 110 so as to cancel the amplitude modulation generated in the frequency-modulated laser light outputted from the laser light source 110 .

[0043] At this time, in order to eliminate the amplitude modulation generated in the frequency-modulated laser output by the laser source 110, the phase shifter 114 makes the phase of the second sine wave lag by a specified phase compared with the phase of the first sine wave. Thus, the amplitude of the frequency-modulated laser output by the laser source 110 can be amplitude-modulated at a phase that lags by a specified phase compared with the phase of the first sine wave, so the laser source module 11 can eliminate the amplitude modulation accidentally generated in the laser. The specified phase depends on the frequency of the first sine wave. Therefore, the laser source module 11 can retain a table that associates the frequency of the first sine wave with the specified phase. The table can be a table created based on the actual measurement results of the phase that can eliminate the amplitude modulation. Based on the table, the laser source module 11 can make the phase of the second sine wave lag by a specified phase compared with the phase of the first sine wave.

[0044] The frequency modulated laser light output by the laser source 110 is frequency modulated so that the phase of the first sine wave is delayed by a predetermined amount. The greater the frequency of the first sine wave, the greater the predetermined amount. Therefore, the greater the frequency of the first sine wave, the greater the phase delay of the second sine wave by the phase shifter 114. The relationship between the frequency of the first sine wave and the predetermined amount can 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 determined in advance.

[0045] The optical amplifier 116 outputs the frequency-modulated laser light to the first optical coupler 12. The laser light outputted from the optical amplifier 116 is a laser light in which amplitude modulation is eliminated and only frequency modulation is performed.

[0046] The first optical coupler 12 splits the laser light supplied from the laser 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.

[0047] The optical switch 13 chops the pump light supplied from the first optical coupler 12 to generate pulse light. The optical switch 13 outputs the pump light, which has been converted into pulse light, to the delay fiber 14 .

[0048] The delay fiber 14 delays the pulse light supplied from the optical switch 13 and outputs the delayed pulse light to the polarization scrambler 15 .

[0049] The polarization scrambler 15 changes the polarization state of the pulse light supplied from the delay fiber 14 to non-polarized state and outputs the pulse light to the circulator 16 .

[0050] The circulator 16 allows the pulse light supplied from the polarization scrambler 15 to enter the optical fiber 1 to be measured. When the pulse light enters the optical fiber 1, Brillouin scattered light is generated in the optical fiber 1. The circulator 16 outputs the Brillouin scattered light entered from the optical fiber 1 to the scattered light amplifier 17.

[0051] The scattered light amplifier 17 amplifies the Brillouin scattered light supplied from the circulator 16 and outputs the amplified light to the second optical coupler 18. The scattered light amplifier 17 may be, for example, an erbium doped fiber amplifier (EDFA: Erbium Doped Fiber Amplifier).

[0052] The second optical coupler 18 multiplexes the Brillouin scattered light supplied from the scattered light amplifier 17 and the reference light supplied from the first optical coupler 12 , and outputs the multiplexed light to the photodiode 19 .

[0053] The photodiode 19 receives the multiplexed light supplied from the second optical coupler 18 and performs heterodyne detection. The photodiode 19 converts the received light into an electric signal and outputs the electric signal to the RF signal amplifier 20.

[0054] The RF signal amplifier 20 amplifies the electric signal supplied from the photodiode 19 and outputs the amplified electric signal to the frequency analyzer 21 .

[0055] 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 .

[0056] The electric signal supplied from the RF signal amplifier 20 to the frequency analyzer 21 includes a Brillouin gain spectrum based on the Brillouin scattered light. The Brillouin gain spectrum includes a frequency component of approximately 11 GHz.

[0057] The frequency analyzer 21 measures the Brillouin frequency shift which is the shift amount of the peak of the Brillouin gain spectrum.

[0058] The Brillouin frequency shift depends on the temperature and strain of the optical fiber 1 in a first order, so the frequency analyzer 21 can measure the temperature and strain of the optical fiber 1 by measuring the Brillouin frequency shift.

[0059] In addition, which position of the optical fiber 1 is to be measured for characteristics depends on the frequency of the first sine wave generated by the signal generator 112. Therefore, the optical fiber characteristic measurement device 10 can scan the measurement position of the optical fiber 1 by scanning the frequency of the first sine wave generated by the signal generator 112. Therefore, the optical fiber characteristic measurement device 10 can measure the temperature and strain of each position of the optical fiber 1 by scanning the frequency of the first sine wave. That is, the optical fiber characteristic measurement device 10 can measure the distribution of the temperature and strain of the optical fiber 1 by measuring the position with the frequency of the first sine wave.

[0060] 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 measurement 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.

[0061] According to the optical fiber characteristic measuring device 10 involved in the above embodiment, the measurement accuracy can be improved. More specifically, the laser source module 11 includes: a laser source 110, which outputs laser light; a laser source driver 111, which frequency-modulates the laser light output by the laser source 110; and an optical amplifier 116, which adjusts the amplitude of the frequency-modulated laser light output by the laser source 110 in a manner that eliminates the amplitude modulation generated in the frequency-modulated laser light output by the laser source 110. Thus, the laser source module 11 can eliminate the amplitude modulation accidentally generated when the laser source driver 111 frequency-modulates the laser light by adjusting the amplitude through the optical amplifier 116. As a result, the laser light output by the laser source module 11 becomes a laser light that is only frequency-modulated but not amplitude-modulated. Therefore, the optical fiber characteristic measuring device 10 involved in one embodiment can make the laser light that is only frequency-modulated be emitted to the optical fiber 1 as the measurement object, and can improve the measurement accuracy of measuring the Brillouin frequency shift.

[0062] (Variation Example)

[0063] Figure 2 FIG. 1 is a diagram showing a schematic configuration of an optical fiber characteristic measuring device 10a according to a modified example. Figure 2 An optical fiber characteristics measuring device 10a according to a modified example will be described.

[0064] The optical fiber characteristic measuring device 10a involved in the modified example has a laser 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.

[0065] The laser source module 11 a of the optical fiber characteristics measurement device 10 a according to the modification includes a laser source 110 , a laser source driver 111 , an optical amplifier driver 115 , an optical amplifier 116 , a first signal generator 117 , and a second signal generator 118 .

[0066] The optical fiber characteristic measuring device 10a according to the modified example is different from the optical fiber characteristic measuring device 10a in that the laser source module 11a includes a first signal generator 117 and a second signal generator 118 as two signal generators. Figure 1 The optical fiber characteristic measuring device 10 shown is different. Figure 1 The laser source module 11 of the optical fiber characteristic measurement device 10 shown has only one signal generator 112 .

[0067] Regarding the optical fiber characteristic measuring device 10a according to the modified example, the main Figure 1 The optical fiber characteristic measuring device 10 shown in FIG. Figure 1Description of common or similar aspects of the optical fiber characteristic measuring device 10 shown will be appropriately omitted.

[0068] The first signal generator 117 outputs the first sine wave to the laser source driver 111 . The laser source driver 111 frequency-modulates the laser light output from the laser source 110 using the first sine wave supplied from the first signal generator 117 .

[0069] The second signal generator 118 outputs the second sinusoidal wave to the optical amplifier driver 115. The frequency of the second sinusoidal wave is equal to the frequency of the first sinusoidal wave.

[0070] The second signal generator 118 delays the phase of the second sine wave according to the frequency of the first sine wave. When the frequency of the first sine wave is high, the second signal generator 118 greatly delays the phase of the second sine wave, and when the frequency of the first sine wave is low, the second signal generator 118 slightly delays the phase of the second sine wave.

[0071] The second signal generator 118 amplifies the amplitude of the second sine wave according to the amplitude of the first sine wave. When the amplitude of the first sine wave is large, the second signal generator 118 greatly amplifies the amplitude of the second sine wave, and when the amplitude of the first sine wave is small, the second signal generator 118 slightly amplifies the amplitude of the second sine wave.

[0072] The optical amplifier driver 115 drives the optical amplifier 116 with the second sine wave supplied from the second signal generator 118 , and adjusts the amplitude of the frequency-modulated laser light outputted from the laser light source 110 to the optical amplifier 116 .

[0073] The optical amplifier 116 adjusts the amplitude of the frequency-modulated laser light outputted from the laser light source 110 so as to cancel the amplitude modulation generated in the frequency-modulated laser light outputted from the laser light source 110 .

[0074] Regarding the optical fiber characteristic measuring device 10a according to the modification, the laser source module 11a can also eliminate the amplitude modulation accidentally generated when the laser source driver 111 performs frequency modulation on the laser light by adjusting the amplitude through the optical amplifier 116. Therefore, the optical fiber characteristic measuring device 10a according to the modification can also allow only the frequency modulated laser light to be emitted to the optical fiber 1 as the measurement object, and can improve the measurement accuracy of the Brillouin frequency shift.

[0075] (Comparative Example)

[0076] Figure 3 2 is a diagram showing a schematic structure of an optical fiber characteristic measuring device 200 according to a comparative example. Figure 3 An optical fiber characteristic measuring device 200 according to a comparative example will be described.

[0077] The laser source module 210 of the optical fiber characteristics measurement device 200 according to the comparative example includes a laser source 110 , a laser source driver 111 , and a signal generator 112 .

[0078] That is, the laser source module 210 of the optical fiber characteristic measuring device 200 according to the comparative example does not have the optical amplifier 116. Figure 1 The laser source module 11 of the optical fiber characteristic measuring device 10 shown is greatly different.

[0079] In the laser source module 210 of the optical fiber characteristics measuring apparatus 200 according to the comparative example, the laser light outputted from the laser source 110 is frequency-modulated by the laser source driver 111 , and the frequency-modulated laser light is directly outputted to the first optical coupler 12 .

[0080] Therefore, laser light that is also amplitude modulated unexpectedly during frequency modulation is directly output to the first optical coupler 12. This amplitude modulation becomes noise, so the measurement accuracy of the optical fiber characteristic measurement apparatus 200 according to the comparative example deteriorates by the noise caused by the amplitude modulation.

[0081] It is obvious to those skilled in the art that the present disclosure can be implemented in other prescribed ways other than the above-mentioned embodiments without departing from its spirit or its essential characteristics. Therefore, the previous description is illustrative and is not limited thereto. The scope of the disclosure is not defined by the previous description, but by the appended claims. Several changes in all changes that are within their equivalent scope are included therein.

[0082] For example, the arrangement and number of the above-mentioned components are not limited to those shown in the above description and the drawings, and the arrangement and number of the above-mentioned components can be arbitrarily configured as long as the functions thereof can be achieved.

[0083] For example, the optical fiber characteristic measuring device 10 and the optical fiber characteristic measuring device 10a are 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 can also measure the characteristics of the optical fiber by the Brillouin Optical Correlation Domain Analysis (BOCDA) method.

[0084] exist Figure 4FIG. 1 shows an example of a schematic structure 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 source module 11, a first optical coupler 31, an SSB modulator 32, a delayed optical 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 source module 11 and Figure 1 The laser source modules 11 shown are identical. Figure 4 The optical fiber characteristic measuring device 30 shown in the figure may replace the laser source module 11 with Figure 2 The first optical coupler 31 splits the laser light supplied from the laser source module 11 into pump light and probe light. The circulator 37 extracts scattered light from the optical fiber 1 and the probe light generated by injecting the pump light into the optical fiber 1 to be measured.

[0085] In addition, for example, the optical fiber characteristic measurement device 10 and the optical fiber characteristic measurement device 10a have been described as measuring the characteristics of the optical fiber by the BOCDR method, but the optical fiber characteristic measurement device 10 and the optical fiber characteristic measurement device 10a may also measure the characteristics of the optical fiber by the optical correlation region reflectometry (OCDR) method for measuring Rayleigh scattering. When measuring the characteristics of the optical fiber by the OCDR method, an acousto-optic modulator may be placed on the reference light or pump light side to perform heterodyne measurement.

[0086] For example, in the above-mentioned embodiment, it is described that the optical fiber characteristic measurement device 10 and the optical fiber characteristic measurement device 10a perform heterodyne detection, but the optical fiber characteristic measurement device 10 and the optical fiber characteristic measurement device 10a may also perform mean square error detection. In the case of performing mean square error detection, the optical fiber characteristic measurement device 10 and the optical fiber characteristic measurement device 10a may have an SSB (Single Side-Band) modulator between the first optical coupler 12 and the second optical coupler 18. Alternatively, the optical fiber characteristic measurement device 10 and the optical fiber characteristic measurement device 10a may have an SSB modulator between the first optical coupler 12 and the optical switch 13.

[0087] 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 thereto. The optical fiber characteristic measuring device 10 and the optical fiber characteristic measuring device 10a can detect the double wave component of the frequency twice the modulation frequency of the modulated light included 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. At this time, the optical fiber characteristic measuring device 10 and the optical fiber characteristic measuring device 10a can perform heterodyne detection or mean square error detection.

[0088] For example, you can manually adjust Figure 1 The amplification of the variable amplifier 113 of the optical fiber characteristic measuring device 10 shown in FIG. Figure 1 The phase shifter 114 of the optical fiber characteristic measuring apparatus 10 shown in the figure delays the phase by an amount.

[0089] Description of the label

[0090] 1 Fiber Optic

[0091] 10.10a Optical fiber characteristic measurement device

[0092] 11. 11a Laser source module

[0093] 12 No. 1 Photocoupler

[0094] 13 Optical switch

[0095] 14 Lag Fiber

[0096] 15 Polarization Scrambler

[0097] 16 Circulator

[0098] 17 Scattered light amplifier

[0099] 18 2nd photocoupler

[0100] 19 Photodiode

[0101] 20RF signal amplifier

[0102] 21Frequency Analyzer

[0103] 30Fiber characteristics measurement device

[0104] 31 No. 1 Photocoupler

[0105] 32 SSB modulator

[0106] 33 Delayed Fiber

[0107] 34 Isolator

[0108] 35 Optical switch

[0109] 36 Optical Amplifier

[0110] 37 Circulator

[0111] 38 Photodiode

[0112] 39LIA

[0113] 40PC

[0114] 110 laser source

[0115] 111 Laser Source Driver

[0116] 112 Signal Generator

[0117] 113 variable amplifier

[0118] 114 Phase Shifter

[0119] 115 Optical Amplifier Driver

[0120] 116 optical amplifier

[0121] 117 No.1 signal generator

[0122] 118 2nd signal generator

[0123] 200 optical fiber characteristics measurement device

[0124] 210 laser source module

Claims

1. An optical fiber characteristic measuring device for measuring the characteristics of an optical fiber, wherein: The optical fiber characteristic measuring device comprises a laser source module for outputting frequency-modulated laser light. The laser source module has: a laser source, which outputs laser light; A laser source driver, which performs frequency modulation on the laser output by the laser source; as well as An optical amplifier adjusts the amplitude of the frequency-modulated laser light outputted from the laser source in such a manner as to cancel the amplitude modulation generated by the frequency-modulated laser light outputted from the laser source.

2. The optical fiber characteristic measuring device according to claim 1, wherein: The laser source module also has: a signal generator for generating a first sine wave used when the laser source driver performs frequency modulation on the laser light outputted by the laser 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; as well as An optical amplifier driver drives the optical amplifier using the second sine wave delayed by the phase shifter, and adjusts the amplitude of the frequency-modulated laser light output from the laser light source.

3. The optical fiber characteristic measuring device according to claim 2, wherein: The laser source module further includes a variable amplifier that amplifies the amplitude of the second sine wave according to the amplitude of the first sine wave and outputs the amplified amplitude to the phase shifter.

4. The optical fiber characteristic measuring device according to claim 1, wherein: The laser source module also has: a first signal generator for generating a first sine wave used when the laser source driver performs frequency modulation on the laser light outputted by the laser source; a second signal generator for generating a second sine wave having a frequency equal to that of the first sine wave and delayed by a frequency corresponding to that of the first sine wave; as well as An optical amplifier driver drives the optical amplifier using the second sine wave to adjust the amplitude of the frequency-modulated laser light output from the laser light source.

5. The optical fiber characteristic measuring device according to claim 4, wherein: The amplitude of the second sine wave generated by the second signal generator is amplified according to the amplitude of the first sine wave.

6. The optical fiber characteristic measuring device according to claim 1, wherein: The optical fiber characteristic measuring device measures the characteristics of the optical fiber by using a Brillouin light correlation area reflectometer method. The optical fiber characteristic measuring device comprises: a first optical coupler that branches the frequency-modulated laser light into a pump light and a reference light; and The second optical coupler combines the scattered light from the optical fiber generated when the pump light is injected into the optical fiber to be measured with the reference light.

7. The optical fiber characteristic measuring device according to claim 1, wherein: The optical fiber characteristic measuring device measures the characteristics of the optical fiber by means of a Brillouin light correlation region analysis method. The optical fiber characteristic measuring device comprises: a first optical coupler that branches the frequency-modulated laser light into pump light and probe light; and A circulator extracts scattered light from the optical fiber and the probe light generated when the pump light is injected into the optical fiber to be measured.

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