Optical fiber characteristic measurement system and humidity measurement method

Abstract

Humidity is measured based on the Brillouin frequency shift. [Solution] The optical fiber characteristic measurement systems 1, 2, and 3 according to this disclosure include a first optical fiber 21, a second optical fiber 22 having different refractive index characteristics from the first optical fiber 21, and an optical fiber characteristic measurement device 10 capable of measuring a first Brillouin frequency shift, which is the Brillouin frequency shift of Brillouin scattered light from the first optical fiber 21, and a second Brillouin frequency shift, which is the Brillouin frequency shift of Brillouin scattered light from the second optical fiber 22. The optical fiber characteristic measurement device 10 measures the humidity at a predetermined location based on the first Brillouin frequency shift and the second Brillouin frequency shift.

Description

Technical Field

[0001] The present disclosure relates to an optical fiber characteristic measurement system and a humidity measurement method.

Background Art

[0002] Conventionally, as an optical fiber characteristic measurement device, an optical fiber characteristic measurement 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 measurement device using the BOCDR method can measure the temperature at each position of an optical fiber by measuring scattered light due to Brillouin scattering and measuring the Brillouin frequency shift (BFS).

[0004] For example, Patent Document 1 discloses an optical fiber characteristic measurement device using the BOCDR method that can shorten the time required for measuring the characteristics of an optical fiber.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Patent Document 1 discloses measuring the Brillouin frequency shift and converting the measured amount of Brillouin frequency shift into temperature. However, Patent Document 1 cannot measure humidity based on the Brillouin frequency shift.

[0007] Therefore, the object of this disclosure is to provide an optical fiber characteristic measurement system and a humidity measurement method that enable the measurement of humidity based on the Brillouin frequency shift. [Means for solving the problem]

[0008] Some embodiments of optical fiber characteristic measurement systems include a first optical fiber, a second optical fiber having different refractive index characteristics from the first optical fiber, and an optical fiber characteristic measurement device capable of measuring a first Brillouin frequency shift, which is the Brillouin frequency shift of Brillouin scattered light from the first optical fiber, and a second Brillouin frequency shift, which is the Brillouin frequency shift of Brillouin scattered light from the second optical fiber, wherein the optical fiber characteristic measurement device measures the humidity at a predetermined location based on the first Brillouin frequency shift and the second Brillouin frequency shift. With such an optical fiber characteristic measurement system, it is possible to measure humidity based on the Brillouin frequency shift.

[0009] In an optical fiber characteristic measurement system according to one embodiment, the optical fiber characteristic measurement device may measure the humidity at the predetermined location by solving a system of equations consisting of a first relational expression, which is the relationship between the first Brillouin frequency shift and temperature and humidity, and a second relational expression, which is the relationship between the second Brillouin frequency shift and temperature and humidity. This makes it possible to easily calculate the humidity by solving the system of equations consisting of the first relational expression and the second relational expression.

[0010] In an optical fiber characteristic measurement system according to one embodiment, the first optical fiber may have a greater change in refractive index when it absorbs moisture than the second optical fiber. This makes it possible to measure the Brillouin frequency shift using two optical fibers with different changes in refractive index when they absorb moisture.

[0011] In an optical fiber characteristic measurement system according to one embodiment, the optical fiber characteristic measurement device may control the predetermined position by adjusting the modulation frequency of the light emitted from the first optical fiber and the modulation frequency of the light emitted from the second optical fiber. This makes it possible to continuously change the predetermined position for measuring humidity.

[0012] In one embodiment of the optical fiber characteristic measurement system, the system may further include a switch that can switch whether the optical fiber characteristic measurement device is connected to the first optical fiber or the second optical fiber. This allows the system to sequentially measure the first Brillouin frequency shift and the second Brillouin frequency shift by switching the connection destination of the optical fiber characteristic measurement device when the first Brillouin frequency shift and the second Brillouin frequency shift are of similar frequencies.

[0013] In one embodiment of the optical fiber characteristic measurement system, the optical fiber characteristic measurement device may measure the first Brillouin frequency shift when the switch is connected to the first optical fiber, and measure the second Brillouin frequency shift when the switch is connected to the second optical fiber. This allows the connection destination of the optical fiber characteristic measurement device to be switched, and the first Brillouin frequency shift and the second Brillouin frequency shift to be measured sequentially.

[0014] In one embodiment of the optical fiber characteristic measurement system, the optical fiber characteristic measurement device may further include an optical coupler that splits the pump light emitted from the optical fiber characteristic measurement device and emits it to the first optical fiber and the second optical fiber. This makes it possible to measure the first Brillouin frequency shift and the second Brillouin frequency shift simultaneously.

[0015] In one embodiment of the optical fiber characteristic measurement system, the optical fiber characteristic measurement device may simultaneously measure the first Brillouin frequency shift and the second Brillouin frequency shift. This can shorten the measurement time.

[0016] In one embodiment of the optical fiber characteristic measurement system, the optical fiber characteristic measurement device comprises a first optical fiber characteristic measurement device and a second optical fiber characteristic measurement device, wherein the first optical fiber characteristic measurement device is connected to the first optical fiber and measures the first Brillouin frequency shift, and the second optical fiber characteristic measurement device is connected to the second optical fiber and measures the second Brillouin frequency shift. This allows for measurement by changing the device configuration of the first optical fiber characteristic measurement device and the device configuration of the second optical fiber characteristic measurement device when the first Brillouin frequency shift and the second Brillouin frequency shift are significantly different.

[0017] A humidity measurement method according to several embodiments is a humidity measurement method in an optical fiber characteristic measurement system comprising a first optical fiber, a second optical fiber having different refractive index characteristics from the first optical fiber, and an optical fiber characteristic measurement device, the method comprising the steps of: measuring a first Brillouin frequency shift, which is the Brillouin frequency shift of Brillouin scattered light from the first optical fiber, using the optical fiber characteristic measurement device; measuring a second Brillouin frequency shift, which is the Brillouin frequency shift of Brillouin scattered light from the second optical fiber; and measuring the humidity at a predetermined location based on the first Brillouin frequency shift and the second Brillouin frequency shift. With such a humidity measurement method, it is possible to measure humidity based on the Brillouin frequency shift. [Effects of the Invention]

[0018] This disclosure provides an optical fiber characteristic measurement system and a humidity measurement method that enable the measurement of humidity based on the Brillouin frequency shift.

Brief Description of the Drawings

[0019] [Figure 1] It is a diagram showing a schematic configuration of an optical fiber characteristic measurement system according to the first embodiment. [Figure 2] It is a diagram showing a schematic configuration of the optical fiber characteristic measurement device of FIG. 1. [Figure 3] It is a diagram showing a state in which the Brillouin frequency shift is measured in the optical fiber characteristic measurement system according to the first embodiment. [Figure 4] It is a diagram showing a schematic configuration of an optical fiber characteristic measurement system according to the second embodiment. [Figure 5] It is a diagram showing a state in which the Brillouin frequency shift is measured in the optical fiber characteristic measurement system according to the second embodiment. [Figure 6] It is a diagram showing a schematic configuration of an optical fiber characteristic measurement system according to the third embodiment. [Figure 7] It is a diagram showing a state in which the Brillouin frequency shift is measured in the optical fiber characteristic measurement system according to the third embodiment.

Modes for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0021] (First Embodiment) FIG. 1 is a diagram showing a schematic configuration of an optical fiber characteristic measurement system 1 according to the first embodiment. The optical fiber characteristic measurement system 1 includes an optical fiber characteristic measurement device 10, a first optical fiber 21, a second optical fiber 22, and a switch 30.

[0022] The optical fiber characteristic measurement device 10 can be connected to the first optical fiber 21 or the second optical fiber 22 via the switch 30.

[0023] The optical fiber characteristic measurement device 10 is a device capable of measuring Brillouin scattered light from an optical fiber. Brillouin scattered light includes the Brillouin gain spectrum. The Brillouin gain spectrum includes frequency components around 11 GHz. The optical fiber characteristic measurement device 10 can measure the Brillouin frequency shift, which is the amount of peak shift in the Brillouin gain spectrum.

[0024] The optical fiber characteristic measuring device 10 may be, for example, a device that measures the characteristics of the first optical fiber 21 or the second optical fiber 22 to be measured using a Brillouin optical correlation region reflectometer (BOCDR) method.

[0025] The first optical fiber 21 is an optical fiber that can be used as a sensor for measuring humidity. The first optical fiber 21 can also be used as a sensor for measuring temperature. The first optical fiber 21 may be attached to or embedded in the object to be measured for humidity measurement. The object to be measured may be, for example, a building, road, bridge, dam, tunnel, aircraft, etc.

[0026] The second optical fiber 22 is an optical fiber that can be used as a sensor for measuring humidity. The second optical fiber 22 can also be used as a sensor for measuring temperature. The second optical fiber 22 may be attached to or embedded in the object to be measured, alongside the first optical fiber.

[0027] The first optical fiber 21 and the second optical fiber 22 have different refractive index characteristics. For example, the first optical fiber 21 may be an optical fiber whose refractive index changes more significantly when it absorbs moisture than that of the second optical fiber 22.

[0028] The first optical fiber 21 may be, for example, an optical fiber made of PMMA (acrylic resin). Optical fibers made of PMMA are hygroscopic, and therefore the refractive index changes significantly when they absorb moisture.

[0029] The second optical fiber 22 may be, for example, a glass optical fiber commonly used for communications. Glass optical fibers commonly used for communications have almost no hygroscopic properties, so the change in refractive index when they absorb moisture is small.

[0030] The switch 30 can switch whether the optical fiber characteristic measuring device 10 is connected to the first optical fiber 21 or the second optical fiber 22. The switch 30 may be any configuration switch that can switch whether the optical fiber characteristic measuring device 10 is connected to the first optical fiber 21 or the second optical fiber 22.

[0031] Figure 2 shows a schematic configuration of the optical fiber characteristic measurement device 10. In this embodiment, the case in which the optical fiber characteristic measurement device 10 measures the characteristics of the first optical fiber 21 or the second optical fiber 22 using the BOCDR method will be described as an example.

[0032] The optical fiber characteristic measuring device 10 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 scattered light amplifier 118, a second optical coupler 119, a photodiode 120, an RF (Radio Frequency) signal amplifier 121, and a frequency analyzer 122.

[0033] 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 by the laser light source 111 is frequency-modulated by the laser light source driver 112.

[0034] The laser light source 111 outputs frequency-modulated laser light to the first optical coupler 113.

[0035] 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.

[0036] 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 119.

[0037] 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.

[0038] The delay fiber 115 delays the pump light supplied from the optical switch 114 and outputs it to the polarization scrambler 116.

[0039] 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.

[0040] The circulator 117 emits the pump light supplied from the polarization scrambler 116 to either the first optical fiber 21 or the second optical fiber 22 via the switch 30. When the pump light is emitted to the first optical fiber 21, the first optical fiber 21 generates Brillouin scattered light. The circulator 117 outputs the Brillouin scattered light incident from the first optical fiber 21 to the scattered light amplifier 118. When the pump light is emitted to the second optical fiber 22, the second optical fiber 22 generates Brillouin scattered light. The circulator 117 outputs the Brillouin scattered light incident from the second optical fiber 22 to the scattered light amplifier 118.

[0041] The scattered light amplifier 118 amplifies the Brillouin scattered light supplied from the circulator 117 and outputs it to the second optical coupler 119. The scattered light amplifier 118 may be, for example, an erbium-doped fiber amplifier (EDFA).

[0042] The second optical coupler 119 combines the Brillouin scattered light supplied from the scattered light amplifier 118 with the reference light supplied from the first optical coupler 113 and outputs it to the photodiode 120.

[0043] The photodiode 120 receives the combined light supplied from the second optical coupler 119 and performs heterodyne detection. The photodiode 120 converts the received light into an electrical signal and outputs it to the RF signal amplifier 121.

[0044] The RF signal amplifier 121 amplifies the electrical signal supplied from the photodiode 120 and outputs it to the frequency analyzer 122.

[0045] The frequency analyzer 122 performs frequency analysis on the electrical signal supplied from the RF signal amplifier 121, that is, the electrical signal corresponding to the light combined by the second optical coupler 119.

[0046] The electrical signal supplied to the frequency analyzer 122 from the RF signal amplifier 121 includes a Brillouin gain spectrum due to Brillouin scattering. The Brillouin gain spectrum includes frequency components around 11 GHz.

[0047] The frequency analyzer 122 measures the Brillouin frequency shift, which is the amount of peak shift in the Brillouin gain spectrum. The Brillouin frequency shift is first dependent on the temperature and humidity of the first optical fiber 21 or the second optical fiber 22.

[0048] The optical fiber characteristic measuring device 10 measures the Brillouin frequency shift of the Brillouin scattered light from the first optical fiber 21 while connected to the first optical fiber 21 by the switch 30. Hereafter, the Brillouin frequency shift of the Brillouin scattered light from the first optical fiber 21 may be referred to as the "first Brillouin frequency shift".

[0049] Furthermore, the optical fiber characteristic measuring device 10 measures the Brillouin frequency shift of the Brillouin scattered light from the second optical fiber 22 while connected to the second optical fiber 22 by the switch 30. Hereafter, the Brillouin frequency shift of the Brillouin scattered light from the second optical fiber 22 may be referred to as the "second Brillouin frequency shift".

[0050] Figure 3 shows an example of measuring the first Brillouin frequency shift BFS1 and the second Brillouin frequency shift BFS2 in the optical fiber characteristic measurement system 1 according to the first embodiment. In the example shown in Figure 3, the first Brillouin frequency shift BFS1 measured using the first optical fiber 21 and the second Brillouin frequency shift BFS2 measured using the second optical fiber 22 are at similar frequencies. However, by switching the switch 30, the optical fiber characteristic measurement device 10 can sequentially measure the first Brillouin frequency shift BFS1 and the second Brillouin frequency shift BFS2.

[0051] The optical fiber characteristic measuring device 10 measures a first Brillouin frequency shift and a second Brillouin frequency shift, and based on the measured first Brillouin frequency shift and second Brillouin frequency shift, it can measure the humidity at a predetermined location.

[0052] First, we will explain how to control the designated location for measuring humidity.

[0053] The optical fiber characteristic measuring device 10 can control a predetermined position by adjusting the modulation frequency of the light emitted from the first optical fiber 21 and the modulation frequency of the light emitted from the second optical fiber 22. The optical fiber characteristic measuring device 10 adjusts the modulation frequency of the light emitted from the first optical fiber 21 and the second optical fiber 22 by changing the frequency of the sinusoidal signal supplied by the laser light source driver 112 to the laser light source 111.

[0054] The predetermined position z for measuring humidity is expressed, for example, by the following equations (1) and (2). The predetermined position z is the position reached by a distance z from one end of the first optical fiber 21 on the switch 30 side to the other end of the first optical fiber 21. Alternatively, the predetermined position z is the position reached by a distance z from one end of the second optical fiber 22 on the switch 30 side to the other end of the second optical fiber 22.

number

number

[0055] The optical fiber characteristic measuring device 10 can continuously change the predetermined position z, which is the target of humidity measurement, by adjusting the modulation frequency.

[0056] In equation (2) above, v g The value of differs between the first optical fiber 21 and the second optical fiber 22. Therefore, the optical fiber characteristic measuring device 10 adjusts the modulation frequency when measuring the first Brillouin frequency shift using the first optical fiber 21 and when measuring the second Brillouin frequency shift using the second optical fiber 22, so that the predetermined position is approximately the same.

[0057] Next, we will explain how the optical fiber characteristic measuring device 10 measures humidity based on the measured first Brillouin frequency shift and second Brillouin frequency shift.

[0058] Since the first Brillouin frequency shift is linearly dependent on the temperature and humidity of the first optical fiber 21, it can be expressed as a first relational equation, which is a relationship between the first Brillouin frequency shift and temperature and humidity, for example, as shown in equation (3) below. BFS1 = a1*T + b1*H (3) However, BFS1 is the first Brillouin frequency shift, a1 is a temperature-dependent parameter of the first optical fiber 21, T is the temperature, and b1 is a humidity-dependent parameter of the first optical fiber 21, H is the humidity.

[0059] Since the second Brillouin frequency shift is linearly dependent on the temperature and humidity of the second optical fiber 22, it can be expressed as a second relational equation, which is the relationship between the second Brillouin frequency shift and temperature and humidity, for example, as shown in equation (4) below. BFS2 = a2*T + b2*H (4) However, BFS2 is the second Brillouin frequency shift, a2 is a temperature-dependent parameter of the second optical fiber 22, T is the temperature, and b2 is a humidity-dependent parameter of the second optical fiber 22, H is the humidity.

[0060] In equation (3) above, a1 and b1 are parameters that depend on the characteristics of the first optical fiber 21, and in equation (4) above, a2 and b2 are parameters that depend on the characteristics of the second optical fiber 22.

[0061] For example, if the refractive index of the first optical fiber 21 changes significantly when it absorbs moisture, then b1 in equation (3) above will be a large value. Also, for example, if the refractive index of the second optical fiber 22 hardly changes even when it absorbs moisture, then b2 in equation (4) above will be a value close to zero.

[0062] Since the first optical fiber 21 and the second optical fiber 22 are installed side by side in almost the same location, in equations (3) and (4) above, the temperature T is the same and the humidity H is the same.

[0063] Therefore, the optical fiber characteristic measuring device 10 can calculate the temperature and humidity at a predetermined location by solving the simultaneous equations of the first relation shown in equation (3) and the second relation shown in equation (4) above. In other words, the optical fiber characteristic measuring device 10 can measure the humidity at a predetermined location by solving the simultaneous equations of the first relation and the second relation.

[0064] (Second Embodiment) Figure 4 shows a schematic configuration of the optical fiber characteristic measurement system 2 according to the second embodiment. The optical fiber characteristic measurement system 2 comprises an optical fiber characteristic measurement device 10, a first optical fiber 21, a second optical fiber 22, and an optical coupler 40.

[0065] Regarding the optical fiber characteristic measurement system 2 according to the second embodiment, we will mainly explain the differences from the optical fiber characteristic measurement system 1 according to the first embodiment, and will omit explanations of points that are common or similar to the optical fiber characteristic measurement system 1 according to the first embodiment as appropriate.

[0066] The optical fiber characteristic measurement system 2 according to the second embodiment differs from the optical fiber characteristic measurement system 1 according to the first embodiment in that it includes an optical coupler 40 instead of a switch 30.

[0067] The optical coupler 40 splits the pump light emitted by the optical fiber characteristic measuring device 10 and emits it to the first optical fiber 21 and the second optical fiber 22.

[0068] In the optical fiber characteristic measurement system 2 according to the second embodiment, the optical fiber characteristic measurement device 10 simultaneously emits pump light to the first optical fiber 21 and the second optical fiber 22 via the optical coupler 40. The optical fiber characteristic measurement device 10 can simultaneously measure the first Brillouin frequency shift of the first optical fiber 21 and the second Brillouin frequency shift of the second optical fiber 22.

[0069] Figure 5 shows an example of the measurement of the first Brillouin frequency shift BFS1 and the second Brillouin frequency shift BFS2 in the optical fiber characteristic measurement system 2 according to the second embodiment. In the example shown in Figure 5, the first Brillouin frequency shift BFS1 measured using the first optical fiber 21 and the second Brillouin frequency shift BFS2 measured using the second optical fiber 22 have similar wavelength bandwidths but are at sufficiently far apart frequencies. In such a case, the two waveforms can be separated, so the optical fiber characteristic measurement device 10 can measure the first Brillouin frequency shift BFS1 and the second Brillouin frequency shift BFS2 simultaneously.

[0070] In the optical fiber characteristic measurement system 2 according to the second embodiment, the optical fiber characteristic measurement device 10 can measure the humidity at a predetermined location based on the measured first Brillouin frequency shift and second Brillouin frequency shift, similar to the optical fiber characteristic measurement system 1 according to the first embodiment.

[0071] (Third embodiment) Figure 6 shows a schematic configuration of the optical fiber characteristic measurement system 3 according to the third embodiment. The optical fiber characteristic measurement system 3 comprises an optical fiber characteristic measurement device 10-1, an optical fiber characteristic measurement device 10-2, a first optical fiber 21, and a second optical fiber 22.

[0072] Regarding the optical fiber characteristic measurement system 3 according to the third embodiment, we will mainly explain the differences from the optical fiber characteristic measurement system 1 according to the first embodiment, and will omit explanations of points that are common or similar to the optical fiber characteristic measurement system 1 according to the first embodiment as appropriate.

[0073] The optical fiber characteristic measurement system 3 according to the third embodiment differs from the optical fiber characteristic measurement system 1 according to the first embodiment mainly in that it includes two optical fiber characteristic measurement devices 10-1 and 10-2, and does not include a switch 30.

[0074] The optical fiber characteristic measuring device 10-1 (corresponding to the "first optical fiber characteristic measuring device" in the claims) is connected to the first optical fiber 21. The optical fiber characteristic measuring device 10-1 measures the first Brillouin frequency shift of the first optical fiber 21.

[0075] The optical fiber characteristic measuring device 10-2 (corresponding to the "second optical fiber characteristic measuring device" in the claims) is connected to the second optical fiber 22. The optical fiber characteristic measuring device 10-2 measures the second Brillouin frequency shift of the second optical fiber 22.

[0076] Figure 7 shows an example of measuring the first Brillouin frequency shift BFS1 and the second Brillouin frequency shift BFS2 in the optical fiber characteristic measurement system 3 according to the third embodiment. In the example shown in Figure 7, the first Brillouin frequency shift BFS1 measured using the first optical fiber 21 and the second Brillouin frequency shift BFS2 measured using the second optical fiber 22 are at significantly different frequencies and their wavelength bands do not overlap. When the first Brillouin frequency shift and the second Brillouin frequency shift are so far apart, it may be necessary to change the configuration of the optical fiber characteristic measurement device 10-1 and the optical fiber characteristic measurement device 10-2. However, by using two optical fiber characteristic measurement devices 10-1 and 10-2, the configuration can be easily changed.

[0077] In the optical fiber characteristic measurement system 3 according to the third embodiment, the optical fiber characteristic measurement device 10-1 can measure the humidity at a predetermined location based on a first Brillouin frequency shift measured by the optical fiber characteristic measurement device 10-1 and a second Brillouin frequency shift measured by the optical fiber characteristic measurement device 10-2. In this case, the optical fiber characteristic measurement device 10-1 may acquire information on the second Brillouin frequency shift from the optical fiber characteristic measurement device 10-2, which is connected to it in a communicationable manner.

[0078] Alternatively, the optical fiber characteristic measuring device 10-2 may acquire information on the first Brillouin frequency shift from the optical fiber characteristic measuring device 10-1, and measure the humidity at a predetermined location based on the first Brillouin frequency shift measured by the optical fiber characteristic measuring device 10-1 and the second Brillouin frequency shift measured by the optical fiber characteristic measuring device 10-2.

[0079] According to the optical fiber characteristic measurement systems 1 to 3 of the first to third embodiments described above, it is possible to measure humidity based on the Brillouin frequency shift. More specifically, the optical fiber characteristic measurement systems 1 to 3 include a first optical fiber 21, a second optical fiber 22 having different refractive index characteristics from the first optical fiber 21, and an optical fiber characteristic measurement device 10 capable of measuring a first Brillouin frequency shift, which is the Brillouin frequency shift of the Brillouin scattered light from the first optical fiber 21, and a second Brillouin frequency shift, which is the Brillouin frequency shift of the Brillouin scattered light from the second optical fiber 22. The optical fiber characteristic measurement device 10 then measures the humidity at a predetermined location based on the first Brillouin frequency shift and the second Brillouin frequency shift. In this way, by measuring the first Brillouin frequency shift and the second Brillouin frequency shift using the first optical fiber 21 and the second optical fiber 22 having different refractive index characteristics, the optical fiber characteristic measurement systems 1 to 3 of the first to third embodiments can measure humidity based on the first Brillouin frequency shift and the second Brillouin frequency shift.

[0080] It will be obvious to those skilled in the art that this disclosure can be implemented in other predetermined forms other than 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.

[0081] 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.

[0082] For example, the optical fiber characteristic measuring device 10 has been described as measuring the first Brillouin frequency shift of the first optical fiber 21 and the second Brillouin frequency shift of the second optical fiber 22 using the BOCDR method, but it is not limited to this. The optical fiber characteristic measuring device 10 may, for example, measure the first Brillouin frequency shift of the first optical fiber 21 and the second Brillouin frequency shift of the second optical fiber 22 using the Brillouin Optical Correlation Domain Analysis (BOCDA) method.

[0083] Some embodiments of the present disclosure are described below. However, it should be noted that the embodiments of the present disclosure are not limited to these. [Note 1] The first optical fiber and A second optical fiber having different refractive index characteristics from the first optical fiber, An optical fiber characteristic measuring device capable of measuring a first Brillouin frequency shift, which is the Brillouin frequency shift of Brillouin scattered light from the first optical fiber, and a second Brillouin frequency shift, which is the Brillouin frequency shift of Brillouin scattered light from the second optical fiber, A fiber optic characteristic measurement system comprising, The optical fiber characteristic measuring device is an optical fiber characteristic measuring system that measures the humidity at a predetermined location based on the first Brillouin frequency shift and the second Brillouin frequency shift. [Note 2] In the optical fiber characteristic measurement system described in Appendix 1, The optical fiber characteristic measuring device is an optical fiber characteristic measuring system that measures the humidity at a predetermined location by solving a system of equations consisting of a first relational equation which is the relationship between the first Brillouin frequency shift and temperature and humidity, and a second relational equation which is the relationship between the second Brillouin frequency shift and temperature and humidity. [Note 3] In the optical fiber characteristic measurement system described in Appendix 1 or 2, An optical fiber characteristic measurement system wherein the first optical fiber exhibits a greater change in refractive index when it absorbs moisture than the second optical fiber. [Note 4] In the optical fiber characteristic measurement system described in any one of the appendices 1 to 3, The optical fiber characteristic measuring device is an optical fiber characteristic measuring system that controls the predetermined position by adjusting the modulation frequency of the light emitted from the first optical fiber and the modulation frequency of the light emitted from the second optical fiber. [Note 5] In the optical fiber characteristic measurement system described in any one of the appendices 1 to 4, An optical fiber characteristic measurement system further comprising a switch that can switch whether the optical fiber characteristic measurement device is connected to the first optical fiber or the second optical fiber. [Note 6] In the optical fiber characteristic measurement system described in any one of the appendices 1 to 5, The optical fiber characteristic measuring apparatus is, With the switch connected to the optical fiber characteristic measuring device and the first optical fiber, the first Brillouin frequency shift is measured. An optical fiber characteristic measurement system that measures the second Brillouin frequency shift while the switch is connected to the optical fiber characteristic measurement device and the second optical fiber. [Note 7] In the optical fiber characteristic measurement system described in any one of the appendices 1 to 6, An optical fiber characteristic measurement system further comprising optical couplers that dewaverate the pump light emitted by the optical fiber characteristic measurement device and emit it to the first optical fiber and the second optical fiber. [Note 8] In the optical fiber characteristic measurement system described in any one of the appendices 1 to 7, The optical fiber characteristic measurement device is an optical fiber characteristic measurement system that simultaneously measures the first Brillouin frequency shift and the second Brillouin frequency shift. [Note 9] In the optical fiber characteristic measurement system described in any one of the appendices 1 to 8, The optical fiber characteristic measuring apparatus comprises a first optical fiber characteristic measuring apparatus and a second optical fiber characteristic measuring apparatus. The first optical fiber characteristic measuring device is connected to the first optical fiber and measures the first Brillouin frequency shift. The second optical fiber characteristic measuring device is connected to the second optical fiber and measures the second Brillouin frequency shift, and is an optical fiber characteristic measuring system. [Note 10] A method for measuring humidity in an optical fiber characteristic measurement system comprising a first optical fiber, a second optical fiber having different refractive index characteristics from the first optical fiber, and an optical fiber characteristic measurement device, Using the aforementioned optical fiber characteristic measuring device, The steps include measuring a first Brillouin frequency shift, which is the Brillouin frequency shift of the Brillouin scattered light from the first optical fiber, The steps include measuring a second Brillouin frequency shift, which is the Brillouin frequency shift of the Brillouin scattered light from the second optical fiber, A step of measuring the humidity at a predetermined location based on the first Brillouin frequency shift and the second Brillouin frequency shift, A method for measuring humidity, including the following. [Explanation of symbols]

[0084] 1, 2, 3 Optical Fiber Characterization System 10 Optical fiber characteristic measurement device 21 The first optical fiber 22 The second optical fiber 30 switches 40 Optical couplers 111 Laser light 112 Laser light source driver 113 First Optical Coupler 114 Optical switch 115 Delay Fiber 116 Polarization Scrambler 117 Circulator 118 Scattered Light Amplifier 119. Second Optical Coupler 120 Photodiodes 121 RF signal amplifier 122 Frequency analyzer

Claims

1. The first optical fiber and A second optical fiber having different refractive index characteristics from the first optical fiber, An optical fiber characteristic measuring device capable of measuring a first Brillouin frequency shift, which is the Brillouin frequency shift of Brillouin scattered light from the first optical fiber, and a second Brillouin frequency shift, which is the Brillouin frequency shift of Brillouin scattered light from the second optical fiber, A fiber optic characteristic measurement system comprising, The optical fiber characteristic measuring device is an optical fiber characteristic measuring system that measures the humidity at a predetermined location based on the first Brillouin frequency shift and the second Brillouin frequency shift.

2. In the optical fiber characteristic measurement system according to claim 1, The optical fiber characteristic measuring device is an optical fiber characteristic measuring system that measures the humidity at a predetermined location by solving a system of equations consisting of a first relational equation which is the relationship between the first Brillouin frequency shift and temperature and humidity, and a second relational equation which is the relationship between the second Brillouin frequency shift and temperature and humidity.

3. In the optical fiber characteristic measurement system according to claim 1, An optical fiber characteristic measurement system wherein the first optical fiber exhibits a greater change in refractive index when it absorbs moisture than the second optical fiber.

4. In the optical fiber characteristic measurement system according to claim 1, The optical fiber characteristic measuring device is an optical fiber characteristic measuring system that controls the predetermined position by adjusting the modulation frequency of the light emitted from the first optical fiber and the modulation frequency of the light emitted from the second optical fiber.

5. In the optical fiber characteristic measurement system according to claim 1, An optical fiber characteristic measurement system further comprising a switch that can switch whether the optical fiber characteristic measurement device is connected to the first optical fiber or the second optical fiber.

6. In the optical fiber characteristic measurement system according to claim 5, The optical fiber characteristic measuring apparatus is, With the switch connected to the optical fiber characteristic measuring device and the first optical fiber, the first Brillouin frequency shift is measured. An optical fiber characteristic measurement system that measures the second Brillouin frequency shift while the switch is connected to the optical fiber characteristic measurement device and the second optical fiber.

7. In the optical fiber characteristic measurement system according to claim 1, An optical fiber characteristic measurement system further comprising optical couplers that dewaverate the pump light emitted by the optical fiber characteristic measurement device and emit it to the first optical fiber and the second optical fiber.

8. In the optical fiber characteristic measurement system according to claim 7, The optical fiber characteristic measurement device is an optical fiber characteristic measurement system that simultaneously measures the first Brillouin frequency shift and the second Brillouin frequency shift.

9. In the optical fiber characteristic measurement system according to claim 1, The optical fiber characteristic measuring apparatus comprises a first optical fiber characteristic measuring apparatus and a second optical fiber characteristic measuring apparatus. The first optical fiber characteristic measuring device is connected to the first optical fiber and measures the first Brillouin frequency shift. The second optical fiber characteristic measuring device is connected to the second optical fiber and measures the second Brillouin frequency shift, and is an optical fiber characteristic measuring system.

10. A method for measuring humidity in an optical fiber characteristic measurement system comprising a first optical fiber, a second optical fiber having different refractive index characteristics from the first optical fiber, and an optical fiber characteristic measurement device, Using the aforementioned optical fiber characteristic measuring device, The steps include measuring a first Brillouin frequency shift, which is the Brillouin frequency shift of the Brillouin scattered light from the first optical fiber, The steps include measuring a second Brillouin frequency shift, which is the Brillouin frequency shift of the Brillouin scattered light from the second optical fiber, A step of measuring the humidity at a predetermined location based on the first Brillouin frequency shift and the second Brillouin frequency shift, A method for measuring humidity, including the following.

Images