Sensor array

Abstract

To provide a sensor array capable of reducing optical crosstalk of a sensor array unlike conventional sensor arrays having disadvantage of large optical crosstalk in exchange for advantage of high pressure resistance obtainable without using a heavy pressure resistant container.SOLUTION: A sensor array provided herein employs wavelength division multiplexing transmission using a first spatial optical part comprising a multilayer film and a part for allowing light to propagate through a liquid provided around the multilayer film, and is configured to allow all light of different wavelengths to transmit through the multilayer film at least once.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a sensor array that uses a plurality of sensors that modulate the intensity and phase of light and transmits light by wavelength division multiplexing. [Background technology]

[0002] Conventionally, in a device that detects sound waves arriving from a specific direction using multiple interferometric optical fiber acoustic sensors as shown in Figure 1 of Patent Document 1, a technique such as wavelength division multiplexing is sometimes used to multiplex and transmit the signals detected by the multiple acoustic sensors to a demodulator. Optical components used for wavelength division multiplexing transmission include multiplexers / demultiplexers as shown in Figures 3 and 4 of Patent Document 2.

[0003] FIG. 3 shows an example of a conventional optical multiplexer / demultiplexer. Light of wavelength A and light of wavelength B output from a light source pass through an optical circulator 3 and an optical fiber 10, exit from a common port 11 of the optical multiplexer / demultiplexer 1, and enter a GI lens 15. The GI lens 15 is cylindrical, with a higher refractive index at its center than at its periphery. It converts the diverging light emitted from the common port 11 into a parallel beam. The parallel beam from the GI lens 15 enters a multilayer film 14, which transmits wavelength A light and reflects wavelength B light. The wavelength A light that passes through the multilayer film 14 is focused at a transmission port 12 by a GI lens 16, passes through optical fiber 20, and is sent to a sensing interferometer A. The wavelength B light that reflects from the multilayer film 14 is focused at a reflection port 13 by the GI lens 15, passes through optical fiber 30, and is sent to a sensing interferometer B. Sensing interferometers A and B are configured similarly to the sensing interferometer shown in FIG. 4 of Patent Document 2. The signal light and reference light reflected by the mirror of sensing interferometer A are emitted from transmission port 12, converted into parallel beams by GI lens 16, transmitted through multilayer film 14, focused at common port 11 by GI lens 15, and sent to the demodulation unit after passing through optical fiber 10 and optical circulator 3. The signal light and reference light reflected by the mirror of sensing interferometer B are emitted from reflection port 13, converted into parallel beams by GI lens 15, reflected by multilayer film 14, focused at common port 11 by GI lens 15, and sent to the demodulation unit after passing through optical fiber 10 and optical circulator 3. Hereinafter, the light that travels back and forth through the optical fiber coil of the sensing interferometer and is sent to the demodulation unit is referred to as signal light, and the light that is reflected by an Faraday Rotator Mirror (FRM) connected to the half mirror of the sensing interferometer without passing through the optical fiber coil and is sent to the demodulation unit is referred to as reference light.

[0004] Because the multiplexer / demultiplexer 1 is immersed in the liquid 2 and has no air chambers, it can operate without being crushed even when the ambient pressure increases. Therefore, high pressure resistance can be achieved without using a heavy pressure-resistant container. Here, the multilayer film 14 is made by layering films of dielectrics with different refractive indices, such as titanium oxide and quartz, on a glass substrate. By designing the thickness and number of layers of the multilayer film 14 according to the dielectrics, glass substrate, and refractive index of the liquid 2 used, it is possible to transmit specific wavelengths and reflect other wavelengths.

[0005] Figure 4 shows the wavelength characteristics of a conventional multiplexer / demultiplexer. The solid line in Figure 4 represents the transmittance between common port 11 and transmission port 12, and the dashed line in Figure 4 represents the reflectance between common port 11 and reflection port 13. Light source wavelength A is set to fall within the transmission band where transmittance is high between common port 11 and transmission port 12, and light source wavelength B is set to fall within the reflection band where reflectance is high between common port 11 and reflection port 13. In this way, the signals detected by sensing interferometer A and the signals detected by sensing interferometer B are multiplexed and transmitted from the light source to multiplexer / demultiplexer 1. The arrow between the transmittance and reflectance in Figure 4 indicates the magnitude of optical crosstalk at wavelength A. The shorter the arrow, the greater the optical crosstalk. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6627563 [Patent Document 2] Japanese Patent Publication No. 2023-28304 Summary of the Invention [Problem to be solved by the invention]

[0007] In the prior art, when the temperature or pressure applied to the multiplexer / demultiplexer 1 changes, the refractive indexes of the dielectric material of the multilayer film 14, the glass substrate, and the liquid 2 change. These changes in refractive index result in changes in the wavelength characteristics of reflection and transmission. One particularly significant change is an increase in the crosstalk of light leaking to the reflection port 13 when light in the transmission band propagates from the common port 11 to the transmission port 12. Another significant change is an increase in the crosstalk of light leaking to the common port 11 when light in the transmission band enters the reflection port 13 and diffuses into the liquid 2. When this crosstalk of light increases, a portion of the light of wavelength A travels back and forth through the sensing interferometer B and enters the reflection port 13 of the multiplexer / demultiplexer 1. This portion of the light then exits the common port 11 and overlaps with the signal light of wavelength A that traveled back and forth through the sensing interferometer A, resulting in optical crosstalk.

[0008] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a sensor array that can reduce optical crosstalk in a sensor array that has high pressure resistance without using a heavy pressure-resistant container but has large optical crosstalk. [Means for solving the problem]

[0009] The sensor array according to the present disclosure is a sensor array that transmits wavelength division multiplexing using a first spatial optical component having a multilayer film and a portion around the multilayer film through which light propagates through a liquid, and is configured so that all of the multiple light beams with different wavelengths pass through the multilayer film at least once. [Effects of the Invention]

[0010] According to the sensor array of the present disclosure, all of the multiple signal light beams with different wavelengths are configured to pass through the multilayer film at least once, and all of the multiple reference light beams are configured to pass through the multilayer film at least once, thereby reducing optical crosstalk. [Brief explanation of the drawings]

[0011] [Figure 1]FIG. 2 is a diagram showing a configuration of a sensor array according to the first embodiment. [Figure 2] FIG. 10 is a diagram showing a configuration of a sensor array according to a second embodiment. [Figure 3] FIG. 1 is a diagram illustrating a configuration of a conventional multiplexer / demultiplexer. [Figure 4] FIG. 10 is a diagram illustrating wavelength characteristics of a conventional multiplexer / demultiplexer. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to the embodiments described below. Also, the size relationships of the components in the drawings may differ from those in reality.

[0013] Embodiment 1 [Sensor array configuration] 1 is a diagram showing the configuration of a sensor array according to embodiment 1. The sensor array according to embodiment 1 includes an optical circulator 3, and a spatial optical component 100, a spatial optical component 300, a spatial optical component 400, a spatial optical component 600, a spatial optical component 700, and a spatial optical component 900.

[0014] The spatial optical component 100 includes a substrate 101, a GI lens 112, a GI lens 142, a multilayer film 113, a half mirror 102, a Faraday rotator 103, and a mirror 104. The spatial optical component 400 includes a substrate 401, a GI lens 412, a GI lens 442, a multilayer film 413, a half mirror 402, a Faraday rotator 403, and a mirror 404. The spatial optical component 700 includes a substrate 701, a GI lens 712, a GI lens 742, a multilayer film 713, a half mirror 702, a Faraday rotator 703, and a mirror 704. Note that hereinafter, an optical component having a multilayer film that has the function of splitting or superimposing light of different wavelengths, in which light is input from or output from an optical fiber, and in which the light propagates through a liquid, is referred to as a first spatial optical component. In this embodiment, the spatial optical component 100, the spatial optical component 400, and the spatial optical component 700 correspond to the first spatial optical component.

[0015] The spatial optical component 300 includes a substrate 301, a GI lens 312, a Faraday rotator 302, and a mirror 303. The spatial optical component 600 includes a substrate 601, a GI lens 612, a Faraday rotator 602, and a mirror 603. The spatial optical component 900 includes a substrate 901, a GI lens 912, a Faraday rotator 902, and a mirror 903. Note that, hereinafter, an optical component that does not include an optical component having a multilayer film that has the function of splitting or superimposing light of different wavelengths, and that inputs or outputs light from an optical fiber and has a portion where light propagates through a liquid is referred to as a second spatial optical component. In this embodiment, the spatial optical component 300, the spatial optical component 600, and the spatial optical component 900 correspond to the above-mentioned second spatial optical components.

[0016] The optical circulator 3 and the spatial optical component 100 are connected by an optical fiber 110. The spatial optical component 100 and the spatial optical component 300 are connected by an optical fiber 210, an optical fiber 310, and an optical fiber coil 200. The spatial optical component 100 and the spatial optical component 400 are connected by an optical fiber 410. The spatial optical component 400 and the spatial optical component 600 are connected by an optical fiber 510, an optical fiber 610, and an optical fiber coil 500. The spatial optical component 400 and the spatial optical component 700 are connected by an optical fiber 710. The spatial optical component 700 and the spatial optical component 900 are connected by an optical fiber 810, an optical fiber 910, and an optical fiber coil 800.

[0017] The system is configured so that light of wavelength A, light of wavelength B, and light of wavelength C output from the light source pass through optical circulator 3 and optical fiber 110, are emitted from common port 111 of spatial optical component 100, and are incident on GI lens 112. The light that has been converted into a parallel beam by GI lens 112 is incident on multilayer film 113. Multilayer film 113 is configured to transmit light of wavelength A and reflect light of wavelength B and light of wavelength C.

[0018] The light of wavelength A transmitted through the multilayer film 113 is configured to be incident on the half mirror 102. A portion of the light incident on the half mirror 102 is transmitted through the half mirror 102, and the remainder is reflected. The light transmitted through the half mirror 102 is transmitted through the Faraday rotator 103 and reflected by the mirror 104, returns to the optical circulator 3 along the same path, and is output to the demodulator as reference light of wavelength A. Meanwhile, the light reflected by the half mirror 102 is focused onto the optical fiber 210 by the GI lens 142, passes through the optical fiber coil 200 and the optical fiber 310, and is emitted from the port 311 of the spatial optical component 300, and is incident on the GI lens 312. The light converted into a parallel beam by the GI lens 312 is transmitted through the Faraday rotator 302 and reflected by the mirror 303, returns to the optical circulator 3 along the same path, and is output to the demodulator as signal light of wavelength A.

[0019] The light of wavelength B reflected by the multilayer film 113 is configured to be focused onto the reflection port 121 by the GI lens 112, pass through the optical fiber 410 to enter the spatial optical component 400, and be transmitted through the multilayer film 413. The light of wavelength C reflected by the multilayer film 113 is configured to be focused onto the reflection port 121 by the GI lens 112, pass through the optical fiber 410 to be reflected off the multilayer film 413 of the spatial optical component 400, pass through the optical fiber 710 to enter the spatial optical component 700, and be transmitted through the multilayer film 713.

[0020] The spatial optical component 400 and the spatial optical component 700 are configured similarly to the spatial optical component 100, except that the wavelength characteristics of the multilayer film 413 or the multilayer film 713 are different from those of the multilayer film 113. The spatial optical component 600 and the spatial optical component 900 are configured similarly to the spatial optical component 300. The spatial optical component 100, the spatial optical component 300, the spatial optical component 400, the spatial optical component 600, the spatial optical component 700, and the spatial optical component 900 are immersed in the liquid 2 and have no air chambers. The spatial optical component 100, the spatial optical component 400, and the spatial optical component 700 have portions around the multilayer film 113, the multilayer film 413, and the multilayer film 713 where light propagates through the liquid (for example, the portion between the GI lens 112 and the multilayer film 113, the portion between the GI lens 412 and the multilayer film 413, and the portion between the GI lens 712 and the multilayer film 713). Furthermore, the optical fiber coil 200, the optical fiber coil 500, and the optical fiber coil 800 are configured to expand and contract due to the sound pressure at the location where they are placed.

[0021] [Sensor array operation] The optical fiber coil 200 expands and contracts due to the sound pressure at the location where it is placed, and the phase of the light passing through the optical fiber coil 200 is phase-modulated by the sound pressure signal. By causing interference between the signal light that has traveled back and forth through the optical fiber coil 200 and the light reflected by the mirror 104, a change in the intensity of the light is generated due to the sound pressure signal, and the sound pressure signal is demodulated in the demodulation unit. The optical fiber coil 500 and the optical fiber coil 800 each expand and contract due to the sound pressure at the location where they are placed, and operate in the same manner as the optical fiber coil 200.

[0022] When the refractive index around the multilayer film changes, the reflectance in the transmission band increases, but the effect on the transmittance in the reflection band is small. This is because the refractive index ratio between the first layer of the multilayer film and the medium before it has a large effect on the reflectance but a small effect on the transmittance.

[0023] Most of the light of wavelength A entering the spatial optical component 100 from the optical circulator 3 is transmitted through the multilayer film 113, but a portion is reflected and enters the optical fiber 410, and is incident on the multilayer film 413 of the spatial optical component 400. Only a small amount of wavelength A can pass through the multilayer film 413, and most of it is reflected. The light of wavelength A reflected by the multilayer film 413 passes through the optical fiber 710, is also reflected by the multilayer film 713 of the spatial optical component 700, and is diffused into the liquid 2, and does not return to the demodulation section.

[0024] Most of the light of wavelength B that enters the spatial optical component 100 from the optical circulator 3 is reflected by the multilayer film 113 of the spatial optical component 100, passes through the optical fiber 410, and is transmitted through the multilayer film 413 of the spatial optical component 400, but a portion is reflected by the multilayer film 413, enters the optical fiber 710, and is incident on the multilayer film 713 of the spatial optical component 700. Only a small amount of light of wavelength B can pass through the multilayer film 713, so optical crosstalk does not become a problem. The light of wavelength B reflected by the multilayer film 413 passes through the optical fiber 710, is also reflected by the multilayer film 713 of the spatial optical component 700, and is diffused into the liquid 2, and does not return to the demodulation unit.

[0025] The signal light of wavelength A passes through the multilayer film twice, at multilayer film 113, and is reflected zero times by the multilayer film. The signal light of wavelength B passes through the multilayer film twice in total, at multilayer film 413, and is reflected twice in total, at multilayer film 113. The signal light of wavelength C passes through the multilayer film twice in total, at multilayer film 713, and is reflected four times in total, at multilayer film 113 and multilayer film 413.

[0026] The reference light of wavelength A passes through the multilayer film two times at multilayer film 113, and is reflected zero times at the multilayer film. The reference light of wavelength B passes through the multilayer film a total of two times at multilayer film 413, and is reflected twice at multilayer film 113. The reference light of wavelength C passes through the multilayer film a total of two times at multilayer film 713, and is reflected four times at multilayer film 113 and multilayer film 413.

[0027] [Effect of sensor array] When the temperatures of the multilayer film 113 and the liquid 2 change, light of wavelength A is reflected by the multilayer film 113, and even if it enters the multilayer film 413, it is attenuated when it passes through the multilayer film 413, so the light that enters the optical fiber coil 500 is suppressed. Light of wavelength A that leaks slightly into the optical fiber coil 500 is also attenuated when it passes through the multilayer film 413 after being reflected by the spatial optical component 600 and returning to the spatial optical component 400, so the light that proceeds to the demodulation unit is sufficiently suppressed. Light of wavelength A that reflects off the multilayer film 113 and the multilayer film 413 and enters the multilayer film 713 is attenuated when it passes through the multilayer film 713, so the light that enters the optical fiber coil 800 is suppressed. Light of wavelength A that leaks slightly into the optical fiber coil 800 is also attenuated when it passes through the multilayer film 713 after being reflected by the spatial optical component 900 and returning to the spatial optical component 700, so the light that proceeds to the demodulation unit is sufficiently suppressed. The light of wavelength A reflected in turn by multilayer film 113, multilayer film 413, and multilayer film 713 is radiated into liquid 2 and does not proceed to the demodulation unit. Therefore, the light of wavelength A proceeding to the demodulation unit attenuates all light except the signal light phase-modulated by optical fiber coil 200 and reflected by spatial optical component 300 and the reference light reflected by mirror 104 of spatial optical component 100, thereby suppressing optical crosstalk. Similarly, the light of wavelength B proceeding to the demodulation unit attenuates all light except the signal light phase-modulated by optical fiber coil 500 and reflected by spatial optical component 600 and the reference light reflected by mirror 404 of spatial optical component 400, thereby suppressing optical crosstalk. As described above, the sensor array according to embodiment 1 has the effect of suppressing optical crosstalk caused by the multilayer film immersed in liquid.

[0028] As described above, the sensor array according to embodiment 1 is a sensor array that transmits wavelength division multiplexing using a spatial optical component having a multilayer film and a portion around the multilayer film where light propagates through a liquid, and is configured so that all of the multiple signal light beams pass through the multilayer film at least once, and all of the multiple reference light beams pass through the multilayer film at least once.

[0029] The sensor array according to the first embodiment can reduce optical crosstalk.

[0030] Furthermore, in the first embodiment, since the number of times that light of each wavelength passes through the multilayer film is the same, the light loss associated with passing through the multilayer film is common, which has the effect of improving performance that is affected by the intensity of the signal light, such as the noise level after demodulation.

[0031] Embodiment 2 The second embodiment will be described below, but explanations of parts that overlap with those of the first embodiment will be omitted, and parts that are the same as or equivalent to those of the first embodiment will be given the same reference numerals.

[0032] [Sensor array configuration] 2 is a diagram showing the configuration of a sensor array according to embodiment 2. The sensor array according to embodiment 2 includes a spatial optical component 1100, a spatial optical component 1300, a spatial optical component 1400, a spatial optical component 1600, a spatial optical component 1700, and a spatial optical component 1900.

[0033] The spatial optical component 1100 includes a substrate 1101, a GI lens 1112, a GI lens 1122, a GI lens 1142, a multilayer film 1113, a half mirror 1102, a Faraday rotator 1103, and a mirror 1104. The spatial optical component 1400 includes a substrate 1401, a GI lens 1412, a GI lens 1422, a GI lens 1442, a multilayer film 1413, a multilayer film 1433, a half mirror 1402, a Faraday rotator 1403, and a mirror 1404. The spatial optical component 1700 includes a substrate 1701, a GI lens 1712, a GI lens 1722, a GI lens 1742, a multilayer film 1713, a multilayer film 1733, a half mirror 1702, a Faraday rotator 1703, and a mirror 1704. In the following description, the spatial optical component 1100, the spatial optical component 1400, and the spatial optical component 1700 correspond to the above-mentioned first spatial optical component.

[0034] The spatial optical component 1300 includes a substrate 1301, a GI lens 1312, a Faraday rotator 1302, and a mirror 1303. The spatial optical component 1600 includes a substrate 1601, a GI lens 1612, a Faraday rotator 1602, and a mirror 1603. The spatial optical component 1900 includes a substrate 1901, a GI lens 1912, a Faraday rotator 1902, and a mirror 1903. In the following description, the spatial optical component 1300, the spatial optical component 1600, and the spatial optical component 1900 correspond to the second spatial optical component.

[0035] The light source and the spatial optical component 1100 are connected by optical fiber 1110. The spatial optical component 1100 and the spatial optical component 1300 are connected by optical fiber 1210, optical fiber 1310, and optical fiber coil 1200. The spatial optical component 1100 and the spatial optical component 1400 are connected by optical fiber 1410 and optical fiber 1430. The spatial optical component 1400 and the spatial optical component 1600 are connected by optical fiber 1510, optical fiber 1610, and optical fiber coil 1500. The spatial optical component 1400 and the spatial optical component 1700 are connected by optical fiber 1710 and optical fiber 1730. The spatial optical component 1700 and the spatial optical component 1900 are connected by optical fiber 1810, optical fiber 1910, and optical fiber coil 1800. The spatial optical component 1700 and the demodulation unit are connected by optical fiber 1750.

[0036] The device is configured so that light of wavelength A, light of wavelength B, and light of wavelength C output from the light source pass through optical fiber 1110, are emitted from common port 1111 of spatial optical component 1100, and are incident on GI lens 1112. The light that has been converted into a parallel beam by GI lens 1112 is incident on multilayer film 1113. Multilayer film 1113 is configured to transmit light of wavelength A and reflect light of wavelength B and light of wavelength C.

[0037] The light of wavelength A that has passed through the multilayer film 1113 is configured to be incident on the half mirror 1102. A portion of the light that has passed through the half mirror 1102 is transmitted through the half mirror 1102, and the remainder is reflected. The light that has passed through the half mirror 1102 is configured to pass through the Faraday rotator 1103, be reflected by the mirror 1104, and return to the half mirror 1102. A portion of the reference light that has returned to the half mirror 1102 from the mirror 1104 is reflected by the half mirror 1102 and focused into the transmission port 1121 by the GI lens 1122, pass through the optical fiber 1430, be reflected by the multilayer film 1433 of the spatial optical component 1400, pass through the optical fiber 1730, be reflected by the multilayer film 1733 of the spatial optical component 1700, and pass through the optical fiber 1750 to be sent to the demodulation unit. The light reflected by the half mirror 1102 is focused onto the optical fiber 1210 by the GI lens 1142, passes through the optical fiber coil 1200 and the optical fiber 1310, is emitted from the port 1311 of the spatial optical component 1300, and is incident on the GI lens 1312. The light converted into a parallel beam by the GI lens 1312 passes through the Faraday rotator 1302 and is reflected by the mirror 1303, and returns to the half mirror 1102 along the same path. A portion of the signal light returning to the half mirror 1102 from the mirror 1303 passes through the half mirror 1102 and is focused onto the transmission port 1121 by the GI lens 1122, passes through the optical fiber 1430, is reflected by the multilayer film 1433 of the spatial optical component 1400, passes through the optical fiber 1730, is reflected by the multilayer film 1733 of the spatial optical component 1700, and passes through the optical fiber 1750 to be sent to the demodulation unit.

[0038] The light of wavelength B reflected by the multilayer film 1113 is configured to be focused onto the reflection port 1131 by the GI lens 1112, pass through the optical fiber 1410 to enter the spatial optical component 1400, and be transmitted through the multilayer film 1413. The light of wavelength C reflected by the multilayer film 1113 is configured to be focused onto the reflection port 1131 by the GI lens 1112, pass through the optical fiber 1410 to be reflected off the multilayer film 1413 of the spatial optical component 1400, pass through the optical fiber 1710 to enter the spatial optical component 1700, and be transmitted through the multilayer film 1713.

[0039] Spatial optical component 1400 and spatial optical component 1700 have the same configuration as spatial optical component 1100, except for the number of multilayer films or the wavelength characteristics of the multilayer films. Spatial optical component 1600 and spatial optical component 1900 have the same configuration as spatial optical component 1300. Spatial optical component 1100, spatial optical component 1300, spatial optical component 1400, spatial optical component 1600, spatial optical component 1700, and spatial optical component 1900 are immersed in liquid 2 and have a structure without air chambers. Spatial optical component 1100, spatial optical component 1400, and spatial optical component 1700 have portions around multilayer film 1113, multilayer film 1413, and multilayer film 1713 where light propagates through the liquid (e.g., the portion between GI lens 1112 and multilayer film 1113, the portion between GI lens 1412 and multilayer film 1413, and the portion between GI lens 1712 and multilayer film 1713). Furthermore, the optical fiber coil 1200, the optical fiber coil 1500, and the optical fiber coil 1800 are configured to expand and contract due to the sound pressure at the location where they are placed.

[0040] In the second embodiment, the multilayer film 1113, the multilayer film 1413, and the multilayer film 1713, which are multilayer films for branching light, and the multilayer film 1433 and the multilayer film 1733, which are multilayer films for overlapping light on the same optical path, are configured as separate bodies rather than being shared.

[0041] [Sensor array operation] Since the optical fiber coil 1200 expands and contracts due to the sound pressure at the location where it is placed, the phase of the light passing through it is phase-modulated by the sound pressure signal. By causing interference between the signal light that has traveled back and forth through the optical fiber coil 1200 and the reference light reflected by the mirror 1104, a change in the intensity of the light is generated due to the sound pressure signal, and the sound pressure signal is demodulated in the demodulation section. Both the optical fiber coil 1500 and the optical fiber coil 1800 expand and contract due to the sound pressure at the location where they are placed, and operate in the same way as the optical fiber coil 1200.

[0042] When the refractive index around the multilayer film changes, the reflectance in the transmission band increases, but the effect on the transmittance in the reflection band is small. This is because the refractive index ratio between the first layer of the multilayer film and the medium before it has a large effect on the reflectance but a small effect on the transmittance.

[0043] Most of the light of wavelength A entering the spatial optical component 1100 from the optical fiber 1110 is transmitted through the multilayer film 1113, but a portion is reflected and enters the optical fiber 1410, and is incident on the multilayer film 1413 of the spatial optical component 1400. Only a small amount of wavelength A can pass through the multilayer film 1413, and most of it is reflected. The light of wavelength A reflected by the multilayer film 1413 passes through the optical fiber 1710, is also reflected by the multilayer film 1713 of the spatial optical component 1700, and is diffused into the liquid 2, and therefore does not reach the demodulation unit.

[0044] Most of the light of wavelength B that enters the spatial optical component 1100 from the optical fiber 1110 is reflected by the multilayer film 1113 of the spatial optical component 1100, passes through the optical fiber 1410, and is transmitted through the multilayer film 1413 of the spatial optical component 1400, but a portion is reflected by the multilayer film 1413, enters the optical fiber 1710, and is incident on the multilayer film 1713 of the spatial optical component 1700. Only a small amount of wavelength B can pass through the multilayer film 1713, so optical crosstalk does not become a problem. The light of wavelength B reflected by the multilayer film 1413 passes through the optical fiber 1710, is also reflected by the multilayer film 1713 of the spatial optical component 1700, and is diffused into the liquid 2, and therefore does not reach the demodulation unit.

[0045] The signal light of wavelength A passes through the multilayer film once, at multilayer film 1113, and is reflected by the multilayer film a total of two times, at multilayer film 1433 and multilayer film 1733. The signal light of wavelength B passes through the multilayer film a total of two times, at multilayer film 1413 and multilayer film 1433, and is reflected by the multilayer film a total of two times, at multilayer film 1113 and multilayer film 1733. The signal light of wavelength C passes through the multilayer film a total of two times, at multilayer film 1713 and multilayer film 1733, and is reflected by the multilayer film a total of two times, at multilayer film 1113 and multilayer film 1413.

[0046] The reference light of wavelength A passes through the multilayer film once, at multilayer film 1113, and is reflected by the multilayer film a total of two times, at multilayer film 1433 and multilayer film 1733. The reference light of wavelength B passes through the multilayer film a total of two times, at multilayer film 1413 and multilayer film 1433, and is reflected by the multilayer film a total of two times, at multilayer film 1113 and multilayer film 1733. The reference light of wavelength C passes through the multilayer film a total of two times, at multilayer film 1713 and multilayer film 1733, and is reflected by the multilayer film a total of two times, at multilayer film 1113 and multilayer film 1413.

[0047] [Effect of sensor array] When the temperatures of the multilayer film 1113 and the liquid 2 change, light of wavelength A is reflected by the multilayer film 1113, and even if it enters the multilayer film 1413, it is attenuated as it passes through the multilayer film 1413, and the light that enters the optical fiber coil 1500 is suppressed. Light of wavelength A that leaks slightly into the optical fiber coil 1500 is also reflected by the spatial optical component 1600 and returns to the spatial optical component 1400, where it is further attenuated by the multilayer film 1433, and therefore the light that proceeds to the demodulation unit is sufficiently suppressed. Light of wavelength A that reflects off the multilayer film 1113 and the multilayer film 1413 and enters the multilayer film 1713 is attenuated as it passes through the multilayer film 1713, and therefore the light that enters the optical fiber coil 1800 is suppressed. Light of wavelength A that leaks slightly into the optical fiber coil 1800 is also reflected by the spatial optical component 1900 and returns to the spatial optical component 1700, where it is further attenuated by the multilayer film 1733, and therefore the light that proceeds to the demodulation unit is sufficiently suppressed. The light of wavelength A reflected in sequence by multilayer film 1113, multilayer film 1413, and multilayer film 1713 is radiated into liquid 2 and does not proceed to the demodulation unit. Therefore, the light of wavelength A proceeding to the demodulation unit is phase-modulated by optical fiber coil 1200 and attenuates all light except the signal light reflected by spatial optical component 1300 and the reference light reflected by mirror 1104 of spatial optical component 1100, thereby suppressing optical crosstalk. Similarly, the light of wavelength B proceeding to the demodulation unit is phase-modulated by optical fiber coil 1500 and attenuates all light except the signal light reflected by spatial optical component 1600 and the reference light reflected by mirror 1404 of spatial optical component 1400, thereby suppressing optical crosstalk. As described above, the sensor array according to the second embodiment has the effect of suppressing optical crosstalk due to changes in the reflectivity of the multilayer film immersed in liquid.

[0048] In the second embodiment, since there is little difference in the number of times each wavelength is reflected by the multilayer film, it is easier to align the intensity of the signal light sent to the demodulation unit, and it is also easier to align the intensity of the reference light sent to the demodulation unit, which has the effect of improving performance that is affected by the intensity of the signal light, such as the noise level after demodulation.

[0049] In the first and second embodiments, a configuration in which a multilayer film, a half mirror, a Faraday rotator, a mirror, etc. are arranged on a substrate has been described. However, other configurations are also possible, for example, in which a multilayer film and a half mirror are arranged on separate substrates and light is transmitted through an optical fiber.

[0050] Furthermore, in the spatial optical component 1100 at the first stage of the second embodiment, which does not require multiplexing, a multilayer film is not provided between the half mirror 1102 and the transmission port 1121, and in the spatial optical component 1700 at the final stage, which does not require branching, a multilayer film 1713 is provided between the common port 1711 and the half mirror 1702. However, a multilayer film may be provided in a location where no multiplexing or branching is required to suppress crosstalk, or a multilayer film may not be provided to suppress loss.

[0051] Furthermore, in the first embodiment, the multilayer film 113, the multilayer film 413, and the multilayer film 713 are connected in series. However, a configuration combining parallel and series connections can also be used using a multiplexer / demultiplexer.

[0052] In addition, in embodiment 2, a configuration has been described in which the multilayer film 1113, the multilayer film 1413, and the multilayer film 1713 on the splitting side are connected in series, and the multilayer film 1433 and the multilayer film 1733 on the multiplexing side are connected in series, but a structure combining parallel and series connections using a splitter or multiplexer is also possible.

[0053] Furthermore, in the first and second embodiments, an example has been described in which a multilayer film is used in which the transmission is a band-pass filter and the reflection is a band-stop filter. However, a configuration in which the transmission and reflection are reversed may be adopted in which a multilayer film is used in which the transmission is a band-stop filter and the reflection is a band-pass filter.

[0054] In addition, in the first and second embodiments, a sensor that demodulates signal light phase-modulated by an optical fiber coil by interfering with reference light is used as an example, but a sensor array can also be configured using a sensor that modulates the intensity of light.

[0055] Furthermore, in the first and second embodiments, an example of a sensor array that detects acoustic signals has been described, but the present invention may also be used in a sensor array that detects other signals such as magnetic, water pressure, and vibration signals.

[0056] Furthermore, in the first and second embodiments, examples have been shown in which only optical components that are immersed in liquid 2 and have a structure without an air chamber are configured, but the effect of reducing optical crosstalk of the present disclosure can also be obtained by using optical components with air chambers such as half mirrors and FRMs, which are optical components other than multilayer films for wavelength division multiplexing transmission. [Explanation of symbols]

[0057] 1 multiplexer / demultiplexer, 2 liquid, 3 optical circulator, 10 optical fiber, 11 common port, 12 transmission port, 13 reflection port, 14 multilayer film, 15 GI lens, 16 GI lens, 20 optical fiber, 30 optical fiber, 100 spatial optical component, 101 substrate, 102 half mirror, 103 Faraday rotator, 104 mirror, 110 optical fiber, 111 common port, 112 GI lens, 113 multilayer film, 121 reflection port, 142 GI lens, 200 optical fiber coil, 210 optical fiber, 300 spatial optical component, 301 substrate, 302 Faraday rotator, 303 mirror, 310 optical fiber, 311 port, 312 GI lens, 400 spatial optical component, 401 substrate, 402 half mirror, 403 Faraday rotator, 404 Mirror, 410 Optical fiber, 412 GI lens, 413 Multilayer film, 442 GI lens, 500 Optical fiber coil, 510 Optical fiber, 600 Spatial optical components, 601 Substrate, 602 Faraday rotator, 603 Mirror, 610 Optical fiber, 611 Port, 612 GI lens, 700 Spatial optical components, 701 Substrate, 702 Half mirror, 703 Faraday rotator, 704 Mirror, 710 Optical fiber, 712 GI lens, 713 Multilayer film, 742 GI lens, 800 Optical fiber coil, 810 Optical fiber, 900 Spatial optical components, 901 Substrate, 902 Faraday rotator, 903 Mirror, 910 Optical fiber, 911 Port, 912 GI lens, 1100 Spatial optical components, 1101 Substrate, 1102 Half mirror, 1103 Faraday rotator, 1104 Mirror, 1110 Optical fiber, 1111 Common port, 1112 GI lens, 1113 Multilayer film, 1121 Transmission port, 1122 GI lens, 1131 Reflection port, 1142 GI lens, 1200 Optical fiber coil, 1210 Optical fiber, 1300 Spatial optical component, 1301 Substrate, 1302 Faraday rotator, 1303 Mirror, 1310 Optical fiber, 1311 Port, 1312 GI lens, 1400 Spatial optical component, 1401 Substrate, 1402 Half mirror, 1403 Faraday rotator, 1404 Mirror, 1410 Optical fiber, 1412 GI lens, 1413 Multilayer film, 1422 GI lens, 1430Optical fiber, 1433 Multilayer film, 1442 GI lens, 1500 Optical fiber coil, 1510 Optical fiber, 1600 Spatial optical components, 1601 Substrate, 1602 Faraday rotator, 1603 Mirror, 1610 Optical fiber, 1611 Port, 1612 GI lens, 1700 Spatial optical components, 1701 Substrate, 1702 Half mirror, 1703 Faraday rotator, 1704 Mirror, 1710 Optical fiber, 1711 Common port, 1712 GI lens, 1713 Multilayer film, 1722 GI lens, 1730 Optical fiber, 1733 Multilayer film, 1742 GI lens, 1750 Optical fiber, 1800 Optical fiber coil, 1810 Optical fiber, 1900 Spatial optical components, 1901 Substrate, 1902 Faraday rotator, 1903 Mirror, 1910 fiber optic, 1911 port, 1912 GI lens.

Claims

1. A sensor array that performs wavelength division multiplexing transmission using a first spatial optical component having a multilayer film and a portion around the multilayer film where light propagates through a liquid, The multilayer film is configured so that all of the light beams having different wavelengths pass through the multilayer film at least once. Sensor array.

2. The multilayer film is configured so that the number of times that the light beams having different wavelengths are transmitted through the multilayer film is the same. The sensor array of claim 1 .

3. The first spatial optical component has the multilayer film for splitting the light and the multilayer film for superimposing the light on the same optical path, each of which is separate. The sensor array of claim 1 .

4. The light beams having different wavelengths are all reflected by the multilayer film the same number of times, or are all transmitted through the multilayer film the same number of times. The sensor array of claim 3 .

5. The multilayer film is configured so that the difference in the number of times that the light beams having three or more different wavelengths are reflected by the multilayer film is one or less, or the difference in the number of times that the light beams are transmitted by the multilayer film is one or less. The sensor array of claim 3 .

6. The optical fiber coil is provided to phase-modulate the phase of the light passing through it with a sound pressure signal. The sensor array according to any one of claims 1 to 5.

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