Optical fiber characteristic measurement apparatus and optical fiber characteristic measurement method

Abstract

Measure the Brillan gain spectrum at low cost. [Solution] The optical fiber characteristic measuring device 10 according to this disclosure measures the characteristics of the optical fiber 1 by a Brillouin optical correlation domain reflectometer. The optical fiber characteristic measuring device 10 comprises a local oscillator 122 that generates a sinusoidal electrical signal, a mixer 121 that receives the Brillouin gain spectrum generated by Brillouin scattering in the optical fiber 1 and the sinusoidal electrical signal generated by the local oscillator 122 as inputs and outputs a down-converted Brillouin gain spectrum, and a frequency analyzer 123 that measures the down-converted Brillouin gain spectrum.

Description

[Technical Field]

[0001] This disclosure relates to an optical fiber characteristic measurement apparatus and an optical fiber characteristic measurement method. [Background technology]

[0002] Conventionally, optical fiber characteristic measurement devices that measure the characteristics of optical fibers using the Brillouin Optical Correlation Domain Reflectometry (BOCDR) method are known. For example, Patent Document 1 discloses an optical fiber characteristic measurement device using the BOCDR method.

[0003] The BOCDR optical fiber characteristic measurement device measures scattered light due to Brillouin scattering and measures the Brillouin frequency shift (BFS), which is the peak frequency of the Brillouin gain spectrum (BGS) produced by Brillouin scattering. This allows for the measurement of temperature and strain at various points in the optical fiber. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6773091 [Overview of the project] [Problems that the invention aims to solve]

[0005] The Brillouin gain spectrum typically occurs in the frequency band of approximately 11 GHz. Therefore, measuring the Brillouin gain spectrum requires a frequency analyzer capable of measuring very high frequencies such as 11 GHz.

[0006] However, frequency analyzers capable of measuring high frequencies such as 11 GHz are generally expensive, making it difficult to measure the Brillouin gain spectrum at low cost.

[0007] Therefore, the purpose of this disclosure is to provide an optical fiber characteristic measurement device and an optical fiber characteristic measurement method that can measure the Brillian gain spectrum at low cost. [Means for solving the problem]

[0008] [1] An optical fiber characteristic measuring device for measuring the characteristics of an optical fiber by the Brillouin optical correlation region reflectometer method, A local oscillator that generates a sinusoidal electrical signal, A mixer receives the Brillouin gain spectrum generated by Brillouin scattering in the optical fiber and the sinusoidal electrical signal generated by the local oscillator, and outputs a down-converted Brillouin gain spectrum. A frequency analyzer for measuring the down-converted Brillan gain spectrum, An optical fiber characteristic measuring device equipped with the following features. Such optical fiber characteristic measurement devices make it possible to measure the Brillouin gain spectrum at low cost.

[0009] [2] In the optical fiber characteristic measuring apparatus described in [1] above, The frequency analyzer may also measure the Brillouin frequency shift, which is the peak frequency of the down-converted Brillouin gain spectrum. This allows for the measurement of the temperature and strain of the optical fiber.

[0010] [3] In the optical fiber characteristic measuring apparatus described in [1] or [2] above, The Brillouin frequency shift, which is the peak frequency of the down-converted Brillouin gain spectrum, may be a frequency of 10 MHz or higher and 2 GHz or lower. This makes it possible to make the frequency analyzer inexpensive.

[0011] [4] An optical fiber characteristic measurement method for measuring the characteristics of an optical fiber by a Brillouin optical correlation domain reflectometer method, inputting the Brillouin gain spectrum generated by Brillouin scattering in the optical fiber and the electrical signal of the sine wave generated by the local oscillator into a mixer, and outputting the down-converted Brillouin gain spectrum; measuring the down-converted Brillouin gain spectrum; An optical fiber characteristic measurement method comprising: According to such an optical fiber characteristic measurement method, it is possible to measure the Brillouin gain spectrum at low cost.

[0012] [5] In the optical fiber characteristic measurement method according to [4] above, the measuring step may measure the Brillouin frequency shift, which is the peak frequency of the down-converted Brillouin gain spectrum. Thereby, the temperature and strain of the optical fiber can be measured.

[0013] [6] In the optical fiber characteristic measurement method according to [4] or [5] above, the Brillouin frequency shift, which is the peak frequency of the down-converted Brillouin gain spectrum, may be a frequency of 10 MHz or more and 2 GHz or less. This makes it possible to make the frequency analyzer inexpensive.

Advantages of the Invention

[0014] According to the present disclosure, it is possible to provide an optical fiber characteristic measurement apparatus and an optical fiber characteristic measurement method capable of measuring the Brillouin gain spectrum at low cost.

Brief Description of the Drawings

[0015] [Figure 1] It is a diagram showing a schematic configuration of an optical fiber characteristic measuring apparatus according to an embodiment. [Figure 2] It is a conceptual diagram of a Brillouin gain spectrum. [Figure 3] It is a diagram showing a schematic configuration of an optical fiber characteristic measuring apparatus according to a comparative example.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0017] FIG. 1 is a diagram showing a schematic configuration of an optical fiber characteristic measuring apparatus 10 according to an embodiment. The optical fiber characteristic measuring apparatus 10 is an apparatus that measures the characteristics of an optical fiber 1 that is a measurement target by a Brillouin optical correlation domain reflectometer (BOCDR) method.

[0018] The optical fiber characteristic measuring apparatus 10 includes a laser light source 111, a laser light source driver 112, a first optical coupler 113, an optical switch 114, a delay fiber 115, a polarization scrambler 11⑥, a circulator 117, a second optical coupler 118, a photodiode 119, an RF (Radio Frequency) signal amplifier 120, a mixer 1②, a local oscillator (LO: Local Oscillator) 122, and a frequency analyzer 123.

[0019] The laser light source 111 outputs laser light. The laser light source 111 may be, for example, a laser diode. The laser light source 111 is capable of outputting frequency-modulated laser light. The laser light output from the laser light source 111 is frequency-modulated by the laser light source driver 112.

[0020] The laser light source 111 outputs the frequency-modulated laser light to the first optical coupler 113.

[0021] The laser light source driver 112 frequency modulates the laser light output by the laser light source 111 by supplying a sinusoidal signal to the laser light source 111. The laser light source driver 112 may be any circuit configuration capable of frequency modulating the laser light output by the laser light source 111.

[0022] The first optical coupler 113 splits the laser light supplied from the laser light source 111 into pump light and reference light. The first optical coupler 113 outputs the pump light to the optical switch 114. The first optical coupler 113 outputs the reference light to the second optical coupler 118.

[0023] The optical switch 114 chops the pump light supplied from the first optical coupler 113 to generate pulsed light. The optical switch 114 outputs the pulsed pump light to the delay fiber 115.

[0024] The delay fiber 115 delays the pump light supplied from the optical switch 114 and outputs it to the polarization scrambler 116.

[0025] The polarization scrambler 116 depolarizes the polarization state of the pump light supplied from the delay fiber 115 and outputs it to the circulator 117.

[0026] The circulator 117 emits the pump light supplied from the polarization scrambler 116 to the optical fiber 1, which is the object of measurement. When the pump light is emitted to the optical fiber 1, the optical fiber 1 generates Brillouin scattered light. The circulator 117 outputs the Brillouin scattered light incident from the optical fiber 1 to the second optical coupler 118.

[0027] The second optical coupler 118 combines the Brillouin scattered light supplied from the circulator 117 with the reference light supplied from the first optical coupler 113 and outputs it to the photodiode 119.

[0028] The photodiode 119 receives the combined light supplied from the second optical coupler 118 and performs heterodyne detection. The photodiode 119 converts the received light into an electrical signal and outputs it to the RF signal amplifier 120.

[0029] The RF signal amplifier 120 amplifies the electrical signal supplied from the photodiode 119 and outputs it to the mixer 121. The electrical signal supplied from the photodiode 119 to the RF signal amplifier 120 includes a Brillouin gain spectrum produced by Brillouin scattering. The Brillouin gain spectrum typically occurs in the frequency band of approximately 11 GHz.

[0030] Mixer 121 receives an electrical signal supplied from RF signal amplifier 120 and a sinusoidal electrical signal supplied from local oscillator 122. The electrical signal supplied from RF signal amplifier 120 includes the Brillouin gain spectrum generated by Brillouin scattering. The Brillouin gain spectrum typically occurs in the frequency band of approximately 11 GHz. In other words, mixer 121 receives the Brillouin gain spectrum generated by Brillouin scattering from RF signal amplifier 120, and a sinusoidal electrical signal from local oscillator 122.

[0031] The local oscillator 122 generates a sinusoidal electrical signal and supplies the sinusoidal electrical signal to the mixer 121. The local oscillator 122 may be any circuit configuration capable of generating a sinusoidal electrical signal. The frequency of the sinusoidal electrical signal generated by the local oscillator 122 may be, for example, around 10 GHz.

[0032] Mixer 121 receives an electrical signal containing the Brillian gain spectrum from RF signal amplifier 120 and a sine wave electrical signal from local oscillator 122, and outputs an electrical signal containing the down-converted Brillian gain spectrum. Here, the Brillian gain spectrum input from RF signal amplifier 120 is approximately 11 GHz. The frequency of the sine wave electrical signal input from local oscillator 122 is, for example, around 10 GHz. In this case, the frequency band of the down-converted Brillian gain spectrum output by mixer 121 is approximately several hundred MHz to 1 GHz.

[0033] The frequency analyzer 123 measures the electrical signal supplied from the mixer 121, which includes a down-converted Brillouin gain spectrum.

[0034] The frequency analyzer 123 measures the down-converted Brillouin gain spectrum and then measures the Brillouin frequency shift, which is the peak frequency of the down-converted Brillouin gain spectrum.

[0035] Since the Brillouin frequency shift is first-orderly dependent on the temperature and strain of the optical fiber 1 being measured, the frequency analyzer 123 can measure the temperature and strain of the optical fiber 1 by measuring the Brillouin frequency shift.

[0036] Figure 2 shows a conceptual diagram of the Brillian gain spectrum output by mixer 121 and the Brillian gain spectrum input to mixer 121.

[0037] The Brillian gain spectrum 201 shown on the left side of Figure 2 is the down-converted Brillian gain spectrum output by mixer 121. The Brillian gain spectrum 202 shown on the right side of Figure 2 is the Brillian gain spectrum input to mixer 121.

[0038] The Brillouin gain spectrum 202 is in a frequency band of about 11 GHz, similar to the Brillouin gain spectrum measured by a general BOCDR-type optical fiber characteristic measuring device. Therefore, f B0 which is the peak frequency of the Brillouin gain spectrum 202, is about 11 GHz.

[0039] The Brillouin gain spectrum 201 is the Brillouin gain spectrum 202 down-converted by the mixer 121 according to the frequency f LO of the sine-wave electrical signal output by the local oscillator 122. For example, when f LO is 10 GHz, the frequency band of the Brillouin gain spectrum 201 is a frequency band 10 GHz lower than that of the Brillouin gain spectrum 202.

[0040] When the frequency analyzer 123 measures the Brillouin gain spectrum 201 output by the mixer 121, it measures the Brillouin frequency shift f B which is the peak frequency of the Brillouin gain spectrum 201. In the example shown in FIG. 2, f B = f B0 - f1] LO For example, when f LO is 10 GHz, the frequency of the Brillouin shift frequency f B is about several 100 MHz to 1 GHz.

[0041] The frequency f LO of the sine-wave electrical signal output by the local oscillator 122 may be set to an arbitrary value. For example, it may be set so that the frequency of the Brillouin shift frequency f B is 10 MHz or more and 2 GHz or less. When the frequency band measured by the frequency analyzer 123 is, for example, a frequency of about 10 MHz or more and 2 GHz or less, the frequency analyzer 123 can be composed of an inexpensive frequency analyzer.

[0042] Also, when the frequency band of the Brillouin gain spectrum 202 is f1 to f2 as shown in FIG. 2, f1 - f LOf > 0 LO You may set this. This will allow f1-f LO By making the frequency negative, aliasing can be prevented.

[0043] Frequency analyzer 123 calculates the Brillouin frequency shift f B By measuring this, the temperature and strain of optical fiber 1 can be measured.

[0044] According to the optical fiber characteristic measurement device 10 of the above embodiment, it is possible to measure the Brillouin gain spectrum at low cost. More specifically, the optical fiber characteristic measurement device 10 is a device for measuring the characteristics of an optical fiber 1 by the Brillouin optical correlation domain reflectometer method, and comprises a local oscillator 122 that generates a sinusoidal electrical signal, a mixer 121, and a frequency analyzer 123. The mixer 121 receives the Brillouin gain spectrum generated by Brillouin scattering in the optical fiber 1 and the sinusoidal electrical signal generated by the local oscillator 122 as input, and the mixer 121 outputs a down-converted Brillouin gain spectrum. The frequency analyzer 123 then measures the Brillouin gain spectrum down-converted by the mixer 121. In this way, the frequency analyzer 123 measures the down-converted Brillouin gain spectrum. The frequency band of the down-converted Brillian gain spectrum is approximately several hundred MHz to 1 GHz, which is significantly lower than the frequency band of the Brillian gain spectrum before down-conversion, which is approximately 11 GHz. Therefore, in one embodiment of the optical fiber characteristic measurement device 10, the frequency analyzer 123 can be an inexpensive frequency analyzer. Consequently, according to one embodiment of the optical fiber characteristic measurement device 10, it is possible to measure the Brillian gain spectrum at low cost.

[0045] (Comparative example) Figure 3 shows a schematic configuration of the optical fiber characteristic measurement device 300 according to the comparative example. The optical fiber characteristic measurement device 300 according to the comparative example comprises a laser light source 111, a laser light source driver 112, a first optical coupler 113, an optical switch 114, a delay fiber 115, a polarization scrambler 116, a circulator 117, a second optical coupler 118, a photodiode 119, an RF signal amplifier 120, and a frequency analyzer 123.

[0046] The optical fiber characteristic measuring device 300 in the comparative example differs from the optical fiber characteristic measuring device 10 according to this embodiment shown in Figure 1 in that it does not include a mixer 121 and a local oscillator 122.

[0047] The optical fiber characteristic measuring device 300 in the comparative example does not have a mixer 121 and a local oscillator 122, so the frequency band of the Brillouin gain spectrum measured by the frequency analyzer 123 is about 11 GHz. In order to measure such high frequencies, the frequency analyzer 123 needs to be an expensive frequency analyzer. Also, frequency analyzers that can measure such high frequencies are generally large.

[0048] In contrast, the optical fiber characteristic measurement device 10 according to this embodiment, as shown in Figure 1, measures the Brillian gain spectrum downconverted by the mixer 121 using a frequency analyzer 123. Since the frequency band of the downconverted Brillian gain spectrum is approximately several hundred MHz to 1 GHz, with the configuration of the optical fiber characteristic measurement device 10 according to this embodiment, the downconverted Brillian gain spectrum can be measured using an inexpensive frequency analyzer 123. Furthermore, the frequency analyzer 123 can be miniaturized.

[0049] It will be apparent to those skilled in the art that this disclosure can be implemented in other predetermined forms besides the embodiments described above without deviating from its spirit or essential features. Therefore, the prior description is illustrative and not limiting. The scope of the disclosure is defined not by the prior description but by the added claims. Any modifications within their equivalent scope are incorporated therein.

[0050] For example, the arrangement and number of each component described above are not limited to those shown in the above description and drawings. The arrangement and number of each component may be configured arbitrarily, as long as it can achieve its function. [Explanation of symbols]

[0051] 1 Optical fiber 10 Optical fiber characteristic measurement device 111 Laser light 112 Laser light source driver 113 First Optical Coupler 114 Optical switch 115 Delay Fiber 116 Polarization Scrambler 117 Circulator 118. Second Optical Coupler 119 Photodiode 120 RF signal amplifier 121 Mixer 122 Local Oscillator (LO) 123 Frequency analyzer 300 Optical Fiber Characterization Measurement Device

Claims

1. An optical fiber characteristic measuring device for measuring the characteristics of an optical fiber using the Brillouin optical correlation region reflectometer method, A local oscillator that generates a sinusoidal electrical signal, A mixer receives the Brillouin gain spectrum generated by Brillouin scattering in the optical fiber and the sinusoidal electrical signal generated by the local oscillator, and outputs a down-converted Brillouin gain spectrum. A frequency analyzer for measuring the down-converted Brillan gain spectrum, An optical fiber characteristic measuring device equipped with the following features.

2. In the optical fiber characteristic measuring apparatus according to claim 1, The frequency analyzer is an optical fiber characteristic measuring device that measures the Brillouin frequency shift, which is the peak frequency of the down-converted Brillouin gain spectrum.

3. In the optical fiber characteristic measuring apparatus according to claim 2, The Brillouin frequency shift, which is the peak frequency of the down-converted Brillouin gain spectrum, is a frequency between 10 MHz and 2 GHz, in an optical fiber characteristic measuring device.

4. A method for measuring the characteristics of an optical fiber by measuring the characteristics of an optical fiber using a Brillouin optical correlation region reflectometer, The steps include inputting the Brillouin gain spectrum generated by Brillouin scattering in the optical fiber and the sinusoidal electrical signal generated by the local oscillator into a mixer and outputting the down-converted Brillouin gain spectrum, The steps include measuring the down-converted Brillan gain spectrum, A method for measuring the characteristics of optical fibers, including the above.

5. In the optical fiber characteristic measurement method described in claim 4, The optical fiber characteristic measurement method is a method in which the measurement step involves measuring the Brillouin frequency shift, which is the peak frequency of the down-converted Brillouin gain spectrum.

6. In the optical fiber characteristic measurement method described in claim 5, A method for measuring the characteristics of an optical fiber, wherein the Brillouin frequency shift, which is the peak frequency of the down-converted Brillouin gain spectrum, has a frequency of 10 MHz or higher and 2 GHz or lower.

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