JP5889123B2 - Optical sensor system - Google Patents

Description

  The present invention relates to an optical sensor system that uses at least two optical electric field sensors to measure the phase of at least two measurement points of electromagnetic waves propagating in space and obtains a phase difference between the measurement points.

  A plurality of receiving antennas corresponding to each frequency band of electromagnetic waves and a plurality of receiving antennas are connected, and a voltage induced in the receiving antennas by an electric field is applied to a modulation electrode corresponding to each of the receiving antennas. A sensor head configured to change the intensity or phase of the transmitted light depending on the light source, a light source for entering the sensor head through the optical fiber, and light detection for detecting the light emitted from the sensor head through the optical fiber The phase of the voltage applied to the modulation electrode is synchronized with the phase of the optical modulation wave that is modulated by the voltage and transmitted through the optical path between the modulation electrodes. A phase matching type optical electric field sensor in which a mutual interval and a length of an optical path between modulation electrodes are set is disclosed (see Patent Document 1).

In this phase-matching optical electric field sensor, the condition that the phase of the voltage induced by the receiving antenna and applied to the modulation electrode of the sensor head is synchronized with the phase of the optical modulation wave transmitted through the optical waveguide between the modulation electrodes. Is represented by the formula: d = (L / n) + (λ / n) · [(δφ ₂ −δφ ₁ ) + m]. Note that L is the distance between adjacent receiving antennas, and d is the length of the optical path between the centers of adjacent modulation electrodes. n is the average refractive index of the optical path, and λ is the wavelength of the electromagnetic wave to be measured. δφ ₁ and δφ ₂ are connected between the receiving antenna and the modulation electrode, and are respective delay amounts due to the delay elements in the order in which the optical modulation waves travel, and m is a positive integer including zero. In a phase-matching optical electric field sensor, the degree of modulation is increased by synchronizing the phase of the voltage applied to each modulation electrode and the phase of the guided light under each modulation electrode, enabling high-sensitivity reception. Become.

JP 11-352165 A

  By the way, in order to obtain the radiation characteristics of electromagnetic waves in space and improve the radiation characteristics, the phase difference between these measurement points may be obtained while measuring the phases of electromagnetic waves at at least two measurement points in space. As an example of the measurement of the phase of the electromagnetic wave at each measurement point, an optical electric field sensor is used, the phase of the electromagnetic wave at each measurement point is measured by the optical electric field sensor, and the phase difference between these measurement points is obtained from the measured phase. . As a specific example, similar to the optical electric field sensor disclosed in Patent Document 1, the intensity of the light is modulated in accordance with the electric field intensity of the electromagnetic wave received by the antenna in the optical electric field sensor, and the modulated light obtained by modulating the input light is modulated. The light is emitted from the optical electric field sensor to the O / E converter, and the O / E converter converts the modulated light into an electric signal, and outputs the converted electric signal to the network analyzer. The network analyzer obtains the phase of the electromagnetic wave at each measurement point from the electrical signal output from the O / E converter, and obtains the phase difference between the measurement points from the obtained phase.

  In phase measurement using an optical electric field sensor, the optical electric field sensor and the O / E converter are connected via an optical fiber having a predetermined length. Here, when the phase of an electromagnetic wave propagating in space is measured using one optical electric field sensor, the optical path length changes depending on the temperature environment at the time of phase measurement, and thereby the propagation time of the modulated light propagating through the optical fiber. Since it changes, the phase of the measured electromagnetic wave fluctuates (shifts) and the measurement accuracy of the phase varies, and the accurate phase may not be measured. For example, when the frequency of the electromagnetic wave to be measured is 0.531 (GHz), the temperature fluctuation width during phase measurement is 60 (° C.), and the length of the optical fiber is 200 (m), the phase of the measured electromagnetic wave is 367 (°) fluctuates (displaces). Therefore, it is difficult to ensure the reliability of the measured phase, and the measured phase cannot be adopted as it is.

  An object of the present invention is to provide an optical sensor system capable of measuring the phase of an electromagnetic wave propagating through space at each measurement point with high reliability and improving the measurement accuracy of the phase difference of the electromagnetic wave between the measurement points. Is to provide.

An optical sensor system according to the present invention uses at least two optical electric field sensors to measure a phase difference between at least two measurement points of an electromagnetic wave propagating in space while obtaining the phase difference between the measurement points. Among the field sensors, second to second phase data emitted from the second to n-th optical electric field sensors for the length (L1) of the first optical fiber that transmits the phase data emitted from the first optical electric field sensor. path difference of the length of the n optical fibers (L2) (ΔL) (L1 -L2) is, plus 2m capable of measuring the phase accurately to changes in the temperature environment at the time of measurement of the phase and minus 2m The length (L2) of the second to nth optical fibers is adjusted with respect to the length (L1) of the first optical fiber so as to be within an appropriate range of at least one of the path difference (ΔL). ) Is calculated by the formula: ΔL ≦ ΔPh / (0.0576 × Frq × ΔT) (ΔL = path difference [m], ΔPh = difference in phase shift [deg], Frq = frequency of electromagnetic wave [GHz] ], ΔT = temperature fluctuation width during measurement [° C.], 0.0576 = phase coefficient [deg / GHz · ° C. · m]) .

  As an example of the optical sensor system of the present invention, when measuring the phase of electromagnetic waves in the optical sensor system, the temperature fluctuation width (ΔT) in the first to nth optical fibers is the same, and the electromagnetic waves sensed in these optical electric field sensors are the same. The frequency (Frq) is the same.

  As another example of the optical sensor system of the present invention, when measuring the phase of electromagnetic waves in the optical sensor system, the phase measurement points by the first to nth optical electric field sensors are close to each other.

  As another example of the optical sensor system of the present invention, the optical sensor system receives a predetermined electromagnetic wave, modulates the intensity of the input light according to the electric field intensity of the electromagnetic wave, and outputs the modulated light obtained by modulating the input light. At least two optical electric field sensors, optical light sources for optical modulators connected to the optical electric field sensors via optical fibers having a predetermined length and emitting the input light to the optical electric field sensors, and predetermined lengths to the optical electric field sensors. And an O / E converter that converts the modulated light emitted from the optical electric field sensors into an electrical signal, and the lengths of the first to nth optical fibers are the first to the first optical fibers. This is the length of the optical fiber connecting the output side of the nth optical electric field sensor and the input side of the O / E converter.

  As another example of the optical sensor system of the present invention, an optical modulator includes a substrate made of a material having an electro-optic effect, an optical waveguide formed on the substrate, and an antenna installed in the vicinity of the optical waveguide. The optical waveguide includes an input optical waveguide extending to the light incident side, two phase shift waveguides extending bifurcated from the input optical waveguide, and extending to the light output side, the phase shift optical waveguides being The phase shift optical waveguide is formed by extending the antenna in parallel with the phase shift waveguide and extending the electric field strength of the electric signal to the phase shift waveguide independently. To change the refractive index.

  As another example of the optical sensor system of the present invention, an optical modulator includes a substrate made of a material having an electro-optic effect, an optical waveguide formed on the substrate, and an optical waveguide installed on the substrate and propagating through the optical waveguide. A light reflecting portion for reflecting light and an antenna installed in the vicinity of the optical waveguide, the optical waveguide extending to the input side of the light, and branching from the input / output optical waveguide And two phase shift waveguides reaching the light reflecting portion, and the antenna extends in the extending direction in parallel with the phase shift waveguides, and the electric field strength of the electric signal is independent of the phase shift waveguides. To change the refractive index of the phase shift optical waveguide.

  According to the optical sensor system of the present invention, since the phase difference between the measurement points is obtained while measuring the phase at each measurement point of the electromagnetic wave propagating through the space using the optical electric field sensor, one optical electric field sensor is obtained. The length of the optical fiber that extends from each optical electric field sensor and transmits phase data varies depending on the temperature environment at the time of measurement. Even if variation (deviation) occurs in the measured phase, the phase deviation measured by the second to nth optical electric field sensors is approximate to the phase deviation measured by the first optical electric field sensor. The phase of the electromagnetic wave propagating through the space can be measured with high reliability using each optical electric field sensor. When the optical sensor system obtains the phase difference of the electromagnetic waves between the respective measurement points, the second to nth photoelectric sensors with respect to the length (L1) of the first optical fiber that transmits the phase data emitted from the first optical electric field sensor. The length of the first optical fiber so that the path difference (ΔL) (L1−L2) of the length (L2) of the second to nth optical fibers that transmit the phase data emitted from the field sensor is within an appropriate range. Since the length (L2) of the second to n-th optical fibers is adjusted with respect to the length (L1), the phases measured by the respective optical electric field sensors are not greatly deviated, and the optical electric field sensors are substantially accurate. Therefore, the measurement accuracy of the phase difference between the measurement points can be improved.

In the optical sensor system, the length of the optical fiber extending from each optical electric field sensor varies depending on the temperature environment at the time of phase measurement, and the length of each optical fiber is not the same, but the length of the first optical fiber ( The first to nth optical fibers so that the path difference (ΔL) of the length (L2) of the second to nth optical fibers with respect to L1) is within an appropriate range of at least one of plus 2 m and minus 2 m. since the length of (L1, L2) is adjusted, the phase path difference of the optical fiber ([Delta] L) is Ri least one of the proper range near the plus 2m and minus 2m, where each optical electric field sensor was measured Are not greatly deviated from each other, and a substantially accurate phase is measured by these optical electric field sensors, and the measurement accuracy of the phase difference between the measurement points can be improved.

In the optical sensor system, the path difference (ΔL) is calculated by the formula: ΔL ≦ ΔPh / (0.0576 × Frq × ΔT), and the phase value (phase) measured by each optical electric field sensor is obtained by using the formula. The difference (ΔPh) in the phase shift amount with respect to the shift amount ) can be set in an allowable range, and the length of each optical fiber can be obtained based on the allowable range. When obtained, the length of each optical fiber can be adjusted so that the path difference (ΔL) of each optical fiber is within an appropriate range. The optical sensor system uses the above-described formula, so that the path difference (ΔL) of each optical fiber is within an appropriate range with respect to the length (L1) of the first optical fiber. Since the length (L2) can be adjusted, the phase measured by each optical electric field sensor is not greatly deviated, and a substantially accurate phase is measured by these optical electric field sensors, and the phase difference between each measurement point is measured. Measurement accuracy can be improved.

At the time of measuring the phase difference in the optical sensor system, the temperature fluctuation width (ΔT) in the first to nth optical fibers is the same, and the frequency (Frq) of the electromagnetic wave measured in these optical electric field sensors is the same. In the formula: ΔL ≦ ΔPh / (0.0576 × Frq × ΔT), the temperature fluctuation range (ΔT) and the frequency (Frq) are constants, and the difference in phase shift (ΔPh) measured by each optical electric field sensor By using as a variable, the difference (ΔPh) in the deviation amount can be freely set within an allowable range, and the length of each optical fiber can be obtained based on the allowable range, and between the measurement points. When obtaining the phase difference of the electromagnetic waves, the length of each optical fiber can be adjusted so that the path difference (ΔL) of each optical fiber is within an appropriate range. The optical sensor system uses the above-described formula, so that the path difference (ΔL) of each optical fiber is within an appropriate range with respect to the length (L1) of the first optical fiber. Since the length (L2) can be adjusted, the phase measured by each optical electric field sensor is not greatly deviated, and a substantially accurate phase is measured by these optical electric field sensors, and the phase difference between each measurement point is measured. Measurement accuracy can be improved.

At the time of measuring the phase difference in the optical sensor system, the optical sensor system in which the phase measurement points by the first to n-th optical electric field sensors are close to each other, the phase measurement point by each optical electric field sensor is close, If the temperature fluctuation ranges (ΔT) in the first to nth optical fibers are substantially the same, and the frequency (Frq) of the electromagnetic wave to be measured is the same, in the formula: ΔL ≦ ΔPh / (0.0576 × Frq × ΔT), becomes the range of the temperature variation ([Delta] T) and frequency (Frq) is constant, that the value of the phase of the optical electric field sensor was measured difference in the amount of phase shift with respect to (the amount of phase shift) (.DELTA.PH) as a variable, the phase can be freely set the difference in the displacement amount (.DELTA.PH) the permissible range, it is possible to determine the length of each optical fiber on the basis of the allowable range, the phase difference of electromagnetic waves between the measuring points When obtaining, as the path difference between the optical fiber ([Delta] L) is within the proper range, it is possible to adjust the length of each optical fiber. In the optical sensor system, the length (L2) of the second to nth optical fibers is set to the length (L1) of the first optical fiber so that the path difference (ΔL) of each optical fiber is within an appropriate range. Because it can be adjusted, the phase measured by each optical electric field sensor is not greatly deviated, and the optical electric field sensor measures a substantially accurate phase and improves the measurement accuracy of the phase difference between each measurement point. Can do.

  At least two optical electric field sensors for outputting modulated light obtained by modulating input light, a light source for an optical modulator connected to the optical electric field sensors via an optical fiber having a predetermined length, and an optical fiber having a predetermined length for the optical electric field sensors The first to nth optical fibers have a length connecting the output side of the first to nth optical electric field sensors and the input side of the O / E converter. The optical sensor system that is the length of the fiber is the length of the optical fiber that connects the output side of the first optical electric field sensor and the input side of the O / E converter when obtaining the phase difference of the electromagnetic waves between the measurement points. The lengths of the optical fibers connecting the output side of the second to nth optical electric field sensors and the input side of the O / E converter with respect to the length (L1) of the first optical fiber that is The path difference (ΔL) (L1−L2) of the optical fiber length (L2) is within an appropriate range. The lengths (L2) of the second to nth optical fibers are adjusted with respect to the length (L1) of the first optical fiber so that the phase measured by each optical electric field sensor is greatly deviated. In other words, the optical electric field sensor measures a substantially accurate phase, and the measurement accuracy of the phase difference between the measurement points can be improved.

  An optical sensor system includes a substrate, an optical waveguide formed on the substrate, and an antenna installed on the substrate, and the antenna independently applies the electric field strength of the electric signal to the phase shift waveguide. Since the refractive index of the phase shift optical waveguide is changed by the electric field strength applied from and the intensity of the input light passing through the phase shift optical waveguide is modulated, the measurement sensitivity of the electromagnetic wave propagating through the space can be increased, and from the outside Without supplying power, the phase of the electromagnetic wave can be measured only by the power of the received electromagnetic wave. By using an optical modulator, the optical sensor system can increase the measurement efficiency of electromagnetic waves and reliably measure the phase of electromagnetic waves, as well as the path difference (ΔL) of each optical fiber ( Since the length (L2) of the second to n-th optical fibers is adjusted with respect to the length (L1) of the first optical fiber so that L1-L2) is within the appropriate range, each optical electric field sensor However, the measured phase does not deviate greatly, and a substantially accurate phase is measured by these optical electric field sensors, and the measurement accuracy of the phase difference between the measurement points can be improved.

  An optical modulator includes a substrate, an optical waveguide formed on the substrate, a light reflecting unit that is installed on the substrate and reflects light propagating through the optical waveguide, and an antenna installed on the substrate, and the antenna is an electric field of an electric signal. The optical sensor system that applies the intensity to these phase shift waveguides independently changes the refractive index of the phase shift optical waveguide according to the electric field intensity applied from the antenna, and modulates the intensity of the input light passing through the phase shift optical waveguide. Therefore, the measurement sensitivity of the electromagnetic wave propagating through the space can be increased, and the phase of the electromagnetic wave can be measured only by the power of the received electromagnetic wave without supplying power from the outside. By using an optical modulator, the optical sensor system can increase the measurement efficiency of electromagnetic waves and reliably measure the phase of electromagnetic waves, as well as the path difference (ΔL) of each optical fiber ( Since the length (L2) of the second to n-th optical fibers is adjusted with respect to the length (L1) of the first optical fiber so that L1-L2) is within the appropriate range, each optical electric field sensor However, the measured phase does not deviate greatly, and a substantially accurate phase is measured by these optical electric field sensors, and the measurement accuracy of the phase difference between the measurement points can be improved.

The block diagram of the optical sensor system shown as an example. The block diagram which shows an example of the optical electric field sensor used for an optical sensor system. The block diagram of the optical modulator of the optical electric field sensor of FIG. FIG. 4 is an end view taken along line 4-4 of FIG. 3. The figure which shows the path | route difference of the optical fiber in an optical sensor system. It illustrates an example of the difference equation and the deviation amount and phase shift amount of the phase calculated by the expression for calculating the difference between the deviation amount and phase shift amount of the phase. The figure which shows an example which calculates the length and path | route difference of an optical fiber, and the length and path | route difference of an optical fiber calculated by the formula. The block diagram of the optical sensor system shown as another example. The block diagram which shows an example of the optical electric field sensor used for an optical sensor system. The block diagram of the optical modulator of the optical electric field sensor of FIG. The figure which shows the path | route difference of the optical fiber in an optical sensor system.

The details of the optical sensor system according to the present invention will be described with reference to the accompanying drawings such as FIG. 1 which is a configuration diagram of the optical sensor system 10A shown as an example. 2 is a configuration diagram illustrating an example of the optical electric field sensors 12A and 12B used in the optical sensor system 10A, and FIG. 3 is a configuration diagram of the optical modulator 25 of the optical electric field sensors 12A and 12B in FIG. is there. 4 is an end view taken along line 4-4 of FIG. 3, and FIG. 5 is a diagram illustrating a path difference ΔL of the optical fibers (L1, L2) in the optical sensor system 10A. 6, the difference between the amount of phase shift (Ph) and the deviation amount of formula and the phase calculated by the expression for calculating the difference (.DELTA.PH) of the amount of phase shift (Ph) and the phase shift amount of (.DELTA.PH) FIG. 7 is a diagram illustrating an example, and FIG. 7 illustrates an expression for calculating the length (L) and path difference (ΔL) of the optical fiber, and the length (L) and path difference (ΔL) of the optical fiber calculated by the expression. It is a figure which shows an example. 3 and 4, the extending direction (the propagation direction of light (laser light)) is indicated by an arrow A (only in FIG. 3), the width direction is indicated by an arrow B, and the thickness direction is indicated by an arrow C (only in FIG. 4).

10 A of optical sensor systems measure the phase in the two measurement points (1st measurement point K1 and 2nd measurement point K2) (refer FIG. 5) of the electromagnetic waves which propagate through space, and the electromagnetic waves between these measurement points K1 and K2 Find the difference in phase shift . In FIG. 1, the two first and second optical electric field sensors 12A and 12B are shown. However, the number of the optical electric field sensors is not limited to two, and the optical sensor system 10A (the optical sensor system 10B is the same). In some cases, the phase difference of the electromagnetic wave between the measurement points may be obtained while measuring the phase of the electromagnetic wave at each measurement point using three or more optical electric field sensors (first to nth optical electric field sensors). .

  When using three optical electric field sensors (first to third optical electric field sensors 12A to 12C), the phases at three measurement points (first to third measurement points) of electromagnetic waves propagating in space are measured, Obtain the phase difference of electromagnetic waves between measurement points. When using four optical electric field sensors (first to fourth optical electric field sensors), the phase at four measurement points (first to fourth measurement points 12A to 12D) of electromagnetic waves propagating in space is measured. The phase difference of the electromagnetic wave between these measurement points is obtained.

  The optical sensor system 10A is composed of a transmission / reception device 11, a first optical electric field sensor 12A, and a second optical electric field sensor 12B. As shown in FIG. 1, the transmission / reception device 11 includes an optical transmission unit 13 and an optical reception unit 14. The optical transmitter 13 includes an optical modulator light source 15, a polarization beam combiner 16, and an optical coupler 17 (optical distributor). In the optical transmitter 13, the light source 15 for the optical modulator and the polarization combiner 16 are connected via the polarization maintaining optical fiber 34, and the polarization combiner 16 and the optical coupler 17 are connected via the single mode optical fiber 18. It is connected.

  The light source for optical modulator 15 has a first light source for light modulator 19A that emits a first laser beam (first input light) having a predetermined polarization plane, and a polarization plane that is 90 ° different from that of the first laser beam. The second light source 19B for the optical modulator that emits the second laser light (second input light) is formed. The polarization beam combiner 16 combines the laser beams emitted (supplied) from the first light source for optical modulator 19A and the second light source for light modulator 19B into a combined laser beam whose polarization planes are orthogonal to each other. The optical coupler 17 distributes the combined laser light combined by the polarization beam combiner 16 into two, emits one combined laser light to the first optical electric field sensor 12A, and outputs the other combined laser light to the second photoelectric light. The light is emitted to the field sensor 12B.

  The first light source for optical modulator 19A is a laser light source that emits (supply) semiconductor laser light to the polarization beam combiner 16 (first and second optical electric field sensors 12A and 12B), and the second light source for optical modulator 19B is The laser light source emits (supplies) semiconductor laser light to the polarization beam combiner 16 (first and second optical electric field sensors 12A and 12B). The semiconductor laser beams emitted from the light sources 19A and 19B have a wavelength of 1.55 μm and an electric energy of 50 mW.

  Note that the laser light emitted from the light sources 19A and 19B may have a wavelength in the range of 1.26 to 1.68 μm, and may have an electric energy in the range of 1 to 100 mW. When the wavelength of the laser light exceeds 1.68 μm, unnecessary noise is generated in the optical fiber, and a loss occurs in the laser light emitted from the light sources 19A and 19B. When the power amount of the laser light exceeds 100 mW, laser light having an unnecessary power amount is supplied to the first and second optical electric field sensors 12A and 12B. As a result, the power consumption of the optical sensor system 10A is reduced. It cannot be reduced.

  The optical receiver 14 includes a first O / E converter 20A, a second O / E converter 20B, a first amplifier 21A, and a second amplifier 21B. In the optical receiver 14, the O / E converters 20A and 20B and the amplifiers 21A and 21B are electrically connected via a feeder line 22 (coaxial cable). The O / E converters 20A and 20B are connected to the first and second optical electric field sensors 12A and 12B (the output optical waveguide 27d of the optical modulator 25) via the single mode optical fiber 18.

  The first and second O / E converters 20A and 20B receive the modulated light from the first and second optical electric field sensors 12A and 12B (optical modulator 25), convert the modulated light into an electrical signal, and then Electric signals are output to the amplifiers 21A and 21B. The amplifiers 21A and 21B are electrically connected to the network analyzer 23 via a feeder line 22 (coaxial cable). The network analyzer 23 analyzes the phase of the electromagnetic waves from the electrical signals output from the first and second O / E converters 20A and 20B and amplified through the amplifiers 21A and 21B, and the phase difference of the electromagnetic waves between the measurement points. Ask for.

  As shown in FIG. 2, the first and second optical electric field sensors 12 </ b> A and 12 </ b> B include a housing 24, and an optical modulator 25 (transmission type) installed inside the housing 24 via a predetermined fixing means. Made from. The transmissive optical modulator 25 receives an electromagnetic wave propagating in space by an antenna 29 described later, and the intensity of laser light (input light) incident from the optical coupler 17 is determined according to the electric field strength of the electromagnetic wave received by the antenna 29. The modulated light obtained by modulating and modulating the laser light is emitted to the first and second O / E converters 20A and 20B.

The optical modulator 25 is made of a single crystal substrate 26 made of an X-cut lithium niobate (LiNbO ₃ ) crystal (material), which is a crystal substrate having an electro-optic effect, and Ti diffusion on the upper surface side of the substrate 26. The Mach-Zehnder type optical waveguide 27, the buffer layer 28 formed on the upper surface side of the substrate 26, and the antenna 29 formed on the buffer layer 28 are formed.

  The Mach-Zehnder type optical waveguide 27 includes one input optical waveguide 27a extending to the incident side of the laser light (input light), and two phase shift waveguides 27b and 27c extending branched from the input optical waveguide 27a. The output optical waveguide 27d is connected to the phase shift optical waveguides 27b and 27c and extends to the laser beam emission side.

  The input optical waveguide 27 a is connected to the optical coupler 17 (polarization combiner 16) via the single mode optical fiber 18, and the output optical waveguide 27 d is connected to the O / E converter via the single mode optical fiber 18. 20A and 20B. The input optical waveguide 27a, the phase shift optical waveguides 27b and 27c, and the output optical waveguide 27d have the same width dimension W in the direction intersecting the extending direction. The phase shift optical waveguides 27b and 27c have the same length in the extending direction.

  The width dimension W of these optical waveguides 27a to 27d is in the range of 5 to 10 μm. The length dimension in the extending direction of each of the phase shift optical waveguides 27b and 27c is in the range of 10 to 30 mm. The center portions of the phase shift optical waveguides 27b and 27c are spaced apart by a predetermined dimension in the width direction and extend in parallel to each other. The distance between the optical waveguides 27b and 27c in the central portion is in the range of 20 to 50 μm. There are no particular limitations on the width dimension W of the optical waveguides 27a to 27d, the length dimension of each of the phase shift optical waveguides 27b and 27c, and the separation dimension of the optical waveguides 27b and 27c in the central portion, and these dimensions are arbitrarily set. be able to.

The buffer layer 28 is provided for the purpose of preventing a part of the laser light propagating through the optical waveguide 27 from being absorbed by the antennas 29. The buffer layer 28 is made of SiO ₂ and has a thickness dimension of about 200 nm. The antennas 29 are arranged in the extending direction so that one of them is located on the input optical waveguide 27a side and the other is located on the output optical waveguide 27d side. These antennas 29 are Cr and Au films formed by sputtering or the like. These antennas 29 receive electromagnetic waves (radio waves) propagating through space and induce an electric signal proportional to the electric field strength of the received electromagnetic waves. The frequency band of electromagnetic waves that can be received by the antenna 29 is not particularly limited.

  The antenna 29 located on the output optical waveguide 27d side has an extending portion 29a disposed between the phase shift optical waveguides 27b and 27c. The extending portion 29a extends in the extending direction in parallel with the central portions of the optical waveguides 27b and 27c. The length dimension of the extending portion 29a of the antenna 29 in the extending direction is 5 mm.

  The antenna 29 positioned on the input optical waveguide 27a side has extending portions 29b and 29c disposed on both sides of the extending portion 29a of the antenna 29 with the phase shift optical waveguides 27b and 27c interposed therebetween. The extending portions 29b and 29c extend in the extending direction in parallel with the central portions of the optical waveguides 27b and 27c. The length dimension of the extending portions 29b and 29c of the antenna 29 in the extending direction is 5 mm.

  Note that there is no particular limitation on the length in the extending direction of the extending portions 29a, 29b, and 29c of the antenna, and the length can be arbitrarily set according to the electric field strength of the electromagnetic wave to be sensed. For example, when the length dimension of the extending portions 29a, 29b, and 29c when the electric field intensity of the electromagnetic wave to be sensed is set to a predetermined value is set as the reference length, as the electric field intensity of the electromagnetic wave to be sensed increases from the predetermined value, The length dimensions of the stretched portions 29a, 29b, and 29c are made shorter than the reference length.

  In this optical sensor system 10A, as shown in FIG. 5, each measurement point (first measurement point K1 and second measurement point K2) of electromagnetic waves propagating in space using the first and second optical electric field sensors 12A and 12B. In the case of obtaining the phase difference between the measurement points K1 and K2 while measuring the phase at (2), the second relative to the length L1 of the first optical fiber 30 that transmits the phase data emitted from the first optical electric field sensor 12A. The path difference (ΔL) (L1−L2) of the length L2 of the second optical fiber 31 that transmits the phase data emitted from the optical electric field sensor 12B is accurate with respect to the change of the temperature environment during the phase measurement. Within an appropriate range that can be measured (the path difference (ΔL) of the length (L2) of the second optical fiber 31 with respect to the length (L1) of the first optical fiber 30 is small between positive and negative The length (L2) of the second optical fiber 31 is adjusted with respect to the length (L1) of the first optical fiber 30 so as to be within at least one appropriate range.

  Specifically, the path difference (ΔL) (L1−L2) is calculated by the formula: ΔL ≦ ΔPh / (0.0576 × Frq × ΔT), and the path difference (ΔL) calculated by the formula is used. The length (L1) of the first optical fiber 30 and the length (L2) of the second optical fiber 31 are required.

In the above equation, ΔL is a path difference [m], and ΔPh is a phase shift difference [deg]. Frq is the frequency [GHz] of the electromagnetic wave, ΔT is the temperature fluctuation range [° C.] at the time of phase measurement, and 0.0576 is the phase coefficient [deg / GHz · ° C. · m]. The length of the first optical fiber 30 is the length of the optical fiber 18 that connects the output side of the first optical electric field sensor 12A and the input side of the first O / E converter 20A, and the second optical fiber 31. Is the length of the optical fiber 18 that connects the output side of the second optical electric field sensor 12B and the input side of the second O / E converter 20B.

In the optical sensor system 10A (including the optical sensor system 10B), three or more optical electric field sensors (first to nth optical electric field sensors) are used, and each measurement point (first to nth) of electromagnetic waves propagating in space is used. In the case of obtaining the phase difference between the measurement points while measuring the phase at the measurement point), the second to second lengths (L1) of the first optical fiber transmitting the phase data emitted from the first optical electric field sensor. The path difference (ΔL) (L1−L2) of the length (L2) of the second to nth optical fibers that transmit the phase data emitted from the nth optical electric field sensor is a change in temperature environment at the time of measuring the phase difference. On the other hand, within an appropriate range in which the phase difference can be accurately measured (the path difference (ΔL) of the length (L2) of the second to nth optical fibers with respect to the length (L1) of the first optical fiber is plus 2 m. And minus 2m The length (L2) of the second to nth optical fibers is adjusted with respect to the length (L1) of the first optical fiber so as to be within at least one appropriate range.

  Also in this case, the path difference (ΔL) (L1−L2) is calculated by the above formula, and the length (L1) of the first optical fiber and the length (L2) of the second to nth optical fibers are obtained. . The lengths of the second to nth optical fibers are the lengths of the optical fibers connecting the output sides of the second to nth optical electric field sensors and the input sides of the second to nth O / E converters.

As shown in FIG. 6, the phase shift amount (Ph) can be calculated by equation (1): and the phase shift amount difference (ΔPh) can be calculated by equation (2): . Further, the length (L) of the optical fiber with respect to the phase shift amount (Ph) can be calculated by the equation (3): as shown in FIG. 7, and the path with respect to the phase shift amount difference (ΔPh). The difference (ΔL) can be calculated by equation (4):

For example, in FIG. 6, the frequency (Frq) is 0.531 [GHz], the temperature fluctuation range (ΔT) is 60 [° C.], the length (L) of the optical fiber is 200 [m], and the phase coefficient is 0.0576. In this case, the phase shift amount (Ph) = 367.0 (°) is calculated by the equation (1), the frequency (Frq) is 0.531 [GHz], and the temperature fluctuation range (ΔT) is 60 [° C.]. When the optical fiber length (L) is 201 [m] and the phase coefficient is 0.0576, the phase shift amount (Ph) = 368.0 [°] is calculated. Further, the difference in phase shift amount (ΔPh) = about ± 1.9 [°] is calculated by the equation (2).

Further, when the frequency (Frq) is 0.531 [GHz], the temperature fluctuation range (ΔT) is 50 [° C.], the length (L) of the optical fiber is 150 [m], and the phase coefficient is 0.0576, The phase shift amount (Ph) = 229.4 (°) is calculated by the equation (1), the frequency (Frq) is 0.531 [GHz], the temperature fluctuation range (ΔT) is 50 [° C.], and the optical fiber When the length (L) is 152 [m] and the phase coefficient is 0.0576, the phase shift amount (Ph) = 232.5 [°] is calculated. Further, the difference in phase shift amount (ΔPh) = about ± 3.1 [°] is calculated by the equation (2).

  In FIG. 7, the phase shift amount (Ph) is 367.0 (°), the frequency (Frq) is 0.531 [GHz], the temperature fluctuation range (ΔT) is 60 [° C.], and the phase coefficient is 0.0576. In some cases, the length (L) of the optical fiber is calculated by Equation (3) = 200 [m], the phase shift amount (Ph) is 368.9 (°), and the frequency (Frq) is 0.531 [GHz]. When the temperature fluctuation range (ΔT) is 60 [° C.] and the phase coefficient is 0.0576, the length (L) of the optical fiber = 201 [m] is calculated. Furthermore, the path difference (ΔL) = about ± 1 [m] is calculated by the equation (4).

  When the phase shift amount (Ph) is 229.4 (°), the frequency (Frq) is 0.531 [GHz], the temperature fluctuation range (ΔT) is 50 [° C.], and the phase coefficient is 0.0576. , The length (L) of the optical fiber is calculated by Equation (3) = 150 [m], the phase shift amount (Ph) is 232.5 (°), the frequency (Frq) is 0.531 [GHz], When the temperature fluctuation range (ΔT) is 50 [° C.] and the phase coefficient is 0.0576, the length (L) of the optical fiber = 152 [m] is calculated. Further, the path difference (ΔL) = about ± 2 [m] is calculated by the equation (4).

By using these formulas (1) to (4), the length (L1) of the first optical fiber and the length of the second optical fiber are set so that the phase shift amount (Ph) is within the appropriate range. (L2) and the length (L1) of the first optical fiber and the second light so that the path difference (ΔL) falls within an appropriate range of at least one of plus 2 m and minus 2 m. The fiber length (L2) can be determined.

  The procedure for measuring the phase and phase difference in the optical sensor system 10A will be described as follows. It is assumed that the switch of the optical sensor system 10A is turned on and laser light is emitted from each of the light sources 19A and 19B. Further, when measuring the phase or phase difference in the optical sensor system 10A, the phase measurement points K1, K2 by the first optical electric field sensor 12A and the second optical electric field sensor 12B are close to each other. Accordingly, the first optical electric field sensor 12A and the second optical electric field sensor 12B are arranged close to each other.

  At the time of measuring the phase or phase difference in the optical sensor system 10A, the temperature fluctuation width (ΔT) in the first optical fiber 30 and the second optical fiber 31 is the same, and the frequency of the electromagnetic wave measured in the optical electric field sensors 12A and 12B. (Frq) is the same. When an electromagnetic wave is transmitted from another antenna (not shown), the electromagnetic wave is received by the optical sensor system 10A (antenna 29 of the first and second optical electric field sensors 12A and 12B).

  The first and second light sources 19A and 19B for the optical modulator emit laser light having a wavelength of 1.55 μm and an electric energy of 50 mW. The laser light enters the polarization beam combiner 16 from the light sources 19A and 19B through the polarization maintaining optical fiber 34, and is combined by the polarization beam combiner 16 into a combined laser beam whose polarization planes are orthogonal to each other. The combined laser light enters the optical coupler 17 through the optical fiber 18, is divided into two by the optical coupler, and then enters the optical modulator 26 of the first and second optical electric field sensors 12 </ b> A and 12 </ b> B.

  In the optical modulator 25, as indicated by an arrow X1 in FIG. 3, the combined laser light emitted from the optical coupler 17 (polarization combiner 16) enters the waveguide 27a from the entrance of the input optical waveguide 27a, and the phase After being divided (divided) by the shift waveguides 27b and 27c and entering the waveguides 27b and 27c, they are coupled (combined) again at the output optical waveguide 27d and emitted from the output optical waveguide 27d as indicated by an arrow X2. To do.

  In the optical modulator 25, when a voltage is applied to the antenna 29 (between the extended portion 29a of the antenna and the extended portions 29b and 29c) by the electric field strength (high-frequency signal) of the electromagnetic wave received by the antenna 29, FIG. Electric fields opposite to each other in the Z-axis direction indicated by the arrow Z are applied to the phase shift optical waveguides 27b and 27c (see FIG. 4).

  By applying an electric field in the opposite direction to the phase shift optical waveguides 27b and 27c, the directions of refractive index change due to the electro-optic effect in the optical waveguides 27b and 27c are opposite to each other and propagate through the phase shift waveguides 27b and 27c. Phase shifts in opposite directions occur in the laser light (one of the combined laser lights). As a result, the laser beams interfere with each other when coupled in the output optical waveguide 27d, and the intensity of the laser light is modulated to become modulated light.

  The modulated light modulated by the optical modulator 25 is emitted from the output optical waveguide 27d, enters the first O / E converter 20A through the optical fiber 18 (optical fiber 30), and the optical fiber 18 (optical fiber 31). ) And enters the second O / E converter 20B. These O / E converters 20A and 20B generate an electric signal obtained by converting the modulated light, and output the electric signal to the amplifiers 21A and 21B. The amplifiers 21A and 21B amplify the electrical signals output from the O / E converters 20A and 20B, and output the amplified electrical signals to the network analyzer 23.

  The network analyzer 23 receives the measurement points K1 received by the antennas 29 of the first and second optical electric field sensors 12A and 12B based on the electrical signals output from the amplifiers 21A and 21B (O / E converters 20A and 20B). The phase of the electromagnetic wave at K2 is measured, the phase difference of the electromagnetic wave between the measurement points K1 and K2 is obtained, and the measured phase and the obtained phase difference are stored in a memory and output from a display or a printer. The network analyzer 23 can also measure the amplitude of the electromagnetic waves at each of the measurement points K1 and K2, and can also output them from a display or a printer while storing the measured amplitudes.

  The optical sensor system 10A obtains the phase difference between the measurement points K1, K2 while measuring the phase at each measurement point K1, K2 of the electromagnetic wave propagating through the space using the optical electric field sensors 12A, 12B. Compared with the case of measuring the phase of electromagnetic waves using two optical electric field sensors, the lengths L1 and L2 of the optical fibers 30 and 31 extending from the respective optical electric field sensors 12A and 12B and transmitting phase data are measured. Even if there is a variation (deviation) in the phase measured by each of the optical electric field sensors 12A and 12B due to change depending on the temperature environment, the second optical electric field with respect to the phase deviation amount measured by the first optical electric field sensor 12A. It can be easily proved that the phase shift amount measured by the sensor 12B is approximate, and the electromagnetic wave propagating in the space using each of the optical electric field sensors 12A and 12B. It can be measured phase with high reliability.

  When the optical sensor system 10A obtains the phase difference of the electromagnetic waves between the measurement points K1 and K2, the optical sensor system 10A corresponds to the length (L1) of the first optical fiber 30 that transmits the phase data emitted from the first optical electric field sensor 12A. ΔL ≦ ΔPh / so that the path difference (ΔL) (L1−L2) of the length (L2) of the second optical fiber 31 that transmits the phase data emitted from the second optical electric field sensor 12B is within an appropriate range. Since the length (L2) of the second optical fiber 31 is adjusted with respect to the length (L1) of the first optical fiber 30 using (0.0576 × Frq × ΔT), each optical electric field sensor 12A , 12B are not greatly deviated from each other, and a substantially accurate phase is measured by the optical electric field sensors 12A, 12B, and the measurement accuracy of the phase difference between the measurement points K1, K2 can be improved.

  The optical sensor system 10A changes the refractive index of the phase shift optical waveguides 27b and 27c according to the electric field strength applied from the antenna 29 of the optical modulator 25, and inputs light (synthetic laser light) passing through the phase shift optical waveguides 27b and 27c. Therefore, the measurement sensitivity of the electromagnetic wave propagating through the space can be increased, and the phase of the electromagnetic wave can be measured only by the power of the received electromagnetic wave without supplying power from the outside.

  The optical sensor system 10A can increase the measurement efficiency of electromagnetic waves by using the optical modulator 25, and the path difference (ΔL) (L1-L2) between the optical fibers 30 and 31 is within an appropriate range. Thus, since the length (L2) of the second optical fiber 31 is adjusted with respect to the length (L1) of the first optical fiber 30, the measurement points K1, K2 are measured by the optical electric field sensors 12A, 12B. It is possible to reliably improve the measurement accuracy of the phase difference between them.

  FIG. 8 is a configuration diagram of an optical sensor system 10B shown as another example, and FIG. 9 is a configuration diagram showing an example of optical electric field sensors 12A and 12B used in the optical sensor system 10B. FIG. 10 is a configuration diagram of the optical modulator 25 of the optical electric field sensors 12A and 12B of FIG. 9, and FIG. 11 is a diagram showing a path difference ΔL of the optical fibers (L1, L2) in the optical sensor system 10B. In FIG. 9, the extending direction (the propagation direction of light (laser light)) is indicated by an arrow A, and the width direction is indicated by an arrow B. Similar to the system 10A, the optical sensor system 10B measures the phases of the electromagnetic waves propagating in space at two measurement points (first measurement point K1 and second measurement point K2) (see FIG. 11), and these measurement points K1. , K2 is obtained.

  The optical sensor system 10B is formed of a transmission / reception device 11, a first optical electric field sensor 12A, and a second optical electric field sensor 12B. As shown in FIG. 8, the transmission / reception device 11 is formed of an optical transmitter 13, an optical receiver 14, and optical circulators 32A and 32B. The optical transmitter 13 includes an optical modulator light source 15, a polarization beam combiner 16, and an optical coupler 17 (optical distributor). The light source for optical modulator 15 and the polarization combiner 16 are connected via a polarization maintaining optical fiber 34, and the polarization combiner 16 and the optical coupler 17 are connected via a single mode optical fiber 18.

  The light source for optical modulator 15 emits a first light source for optical modulator 19A that emits a first laser beam having a predetermined polarization plane, and a second laser beam that has a polarization plane that is 90 ° different from that of the first laser beam. And the second light source 19B for the optical modulator. The first light source for optical modulator 19A, the second light source for optical modulator 19B, the polarization beam combiner 16, and the optical coupler are the same as those of the system 10A of FIG. The optical coupler 17 is connected to the optical circulators 32A and 32B via the single mode optical fiber 18, and emits one combined laser light combined by the polarization beam combiner 16 to the optical circulator 32A and the other combined. Laser light is emitted to the optical circulator 32B.

  The optical circulators 32A and 32B emit the combined laser beam only in one direction. The optical circulator 32 </ b> A is connected to the first optical electric field sensor 12 </ b> A (the input optical waveguide 27 a and the output optical waveguide 27 d of the optical modulator 25) via the single mode optical fiber 18 and via the single mode optical fiber 18. It is connected to the first O / E converter 20A. The optical circulator 32B is connected to the second optical electric field sensor 12B (the input optical waveguide 27a and the output optical waveguide 27d of the optical modulator 25) via the single mode optical fiber 18, and via the single mode optical fiber 18. It is connected to the second O / E converter 20B.

  The optical receiver 14 includes a first O / E converter 20A, a second O / E converter 20B, a first amplifier 21A, and a second amplifier 21B. In the optical receiver 14, the O / E converters 20A and 20B and the amplifiers 21A and 21B are electrically connected via a feeder line 22 (coaxial cable). The amplifiers 21A and 21B are electrically connected to the network analyzer 23 via a feeder line 22 (coaxial cable). The first and second O / E converters 20A and 20B, the amplifiers 21A and 21B, and the network analyzer 23 are the same as those of the system 10A of FIG.

  As shown in FIG. 9, the first and second optical electric field sensors 12 </ b> A and 12 </ b> B include a housing 24 and an optical modulator 25 (reflection type) installed inside the housing 24 via a predetermined fixing means. Made from. The reflection type optical modulator 25 receives an electromagnetic wave propagating in space by an antenna 29 described later, and changes the intensity of the laser light (input light) incident from the optical circulators 32A and 32B to the electric field strength of the electromagnetic wave received by the antenna 29. The modulated light modulated according to the laser light is emitted to the optical circulators 32A and 32B (first and second O / E converters 20A and 20B).

8 includes a single crystal substrate 26 made of an X-cut lithium niobate (LiNbO ₃ ) crystal (material), which is a crystal substrate having an electro-optic effect. A Mach-Zehnder type optical waveguide 27 made by Ti diffusion on the upper surface side of the substrate 26, a buffer layer 28 formed on the upper surface side of the substrate 27, an antenna 29 formed on the buffer layer 28, It is formed from a light reflecting portion 33 installed at the other end of the substrate 26.

  The Mach-Zehnder type optical waveguide 27 includes one input / output optical waveguide 27a extending to the laser light (input light) incident side, and two phase shift waveguides 27b extending bifurcated from the input / output optical waveguide 27a. 27c. The input / output optical waveguide 27a and the phase shift optical waveguides 27b and 27c have the same width dimension W in the direction intersecting the extending direction. The phase shift optical waveguides 27b and 27c have the same length in the extending direction.

  The width dimension W of these optical waveguides 27a to 27c is in the range of 5 to 10 μm. The length dimension in the extending direction of each of the phase shift optical waveguides 27b and 27c is in the range of 10 to 30 mm. The center portions of the phase shift optical waveguides 27b and 27c are spaced apart by a predetermined dimension in the width direction and extend in parallel to each other. The distance between the optical waveguides 27b and 27c in the central portion is in the range of 20 to 50 μm.

The buffer layer 28 is made of SiO ₂ and has a thickness dimension of about 200 nm (with reference to FIG. 4). The antennas 29 are arranged in the extending direction so that one of them is located on the input / output optical waveguide 27a side and the other is located on the opposite side of the input / output optical waveguide 27a. These antennas 29 are Cr and Au films formed by sputtering or the like.

  The antenna 29 positioned on the opposite side of the input / output optical waveguide 27a has an extended portion 29a disposed between the phase shift optical waveguides 27b and 27c, and the antenna 29 positioned on the input / output optical waveguide 27a side Extending portions 29b and 29c are disposed on both sides of the extending portion 29a of the antenna 29 with the shift optical waveguides 27b and 27c interposed therebetween. The extending portions 29a, 29b, and 29c extend in the extending direction in parallel with the central portions of the optical waveguides 27b and 27c. The length dimension of the extending portions 29a, 29b, 29c of the antenna 29 in the extending direction is 5 mm.

  The light reflecting portion 33 is installed at the other end of the substrate 26 opposite to the one end from which the input optical waveguide 27a extends. The light reflecting section 33 reflects the modulated light that has entered the input / output optical waveguide 27a and propagated to the phase shift optical waveguides 27b and 27c, and propagates the modulated light from the phase shift optical waveguides 27b and 27c to the input / output optical waveguide 27a. .

  In this optical sensor system 10B, as shown in FIG. 11, each measurement point (first measurement point K1 and second measurement point K2) of electromagnetic waves propagating in space using the first and second optical electric field sensors 12A and 12B. In the case of obtaining the phase difference between the measurement points K1 and K2 while measuring the phase at (2), the second relative to the length L1 of the first optical fiber 30 that transmits the phase data emitted from the first optical electric field sensor 12A. The path difference (ΔL) (L1−L2) of the length L2 of the second optical fiber 31 that transmits the phase data emitted from the optical electric field sensor 12B is accurate with respect to the change of the temperature environment during the phase measurement. Within an appropriate range that can be measured (the path difference (ΔL) of the length (L2) of the second optical fiber 31 with respect to the length (L1) of the first optical fiber 30 is small between plus and minus The length (L2) of the second optical fiber 31 is adjusted with respect to the length (L1) of the first optical fiber 30 so as to be within at least one appropriate range.

  In the optical sensor system 10B, the path difference (ΔL) (L1−L2) is calculated by the formula: ΔL ≦ ΔPh / (0.0576 × Frq × ΔT), and the path difference (ΔL) calculated by the formula is used. In addition, the length (L1) of the first optical fiber 30 and the length (L2) of the second optical fiber 31 are required. The length of the first optical fiber 30 is the length of the optical fiber 18 that connects the output side of the first optical electric field sensor 12A and the input side of the first O / E converter 20A, and the length of the second optical fiber 31. This is the length of the optical fiber 18 that connects the output side of the second optical electric field sensor 12B and the input side of the second O / E converter 20B.

The phase shift amount (Ph) can be calculated by the equation (1): shown in FIG. 6, and the phase shift amount difference (ΔPh) can be calculated by the equation (2): shown in FIG. it can. Further, the length (L) of the optical fiber with respect to the phase shift amount (Ph) can be calculated by the equation (3) shown in FIG. 7, and the path difference (ΔL) with respect to the phase shift amount difference (ΔPh). ) Can be calculated by equation (4): shown in FIG. By using these formulas (1) to (4), the length (L1) of the first optical fiber and the length of the second optical fiber are set so that the phase shift amount (Ph) is within the appropriate range. (L2) and the length (L1) of the first optical fiber and the second light so that the path difference (ΔL) falls within an appropriate range of at least one of plus 2 m and minus 2 m. The fiber length (L2) can be determined.

  The procedure for measuring the phase and phase difference in the optical sensor system 10B will be described as follows. At the time of measuring the phase and phase difference in the optical sensor system 10B, the phase measurement points K1, K2 by the first optical electric field sensor 12A and the second optical electric field sensor 12B are close to each other. Accordingly, the first optical electric field sensor 12A and the second optical electric field sensor 12B are arranged close to each other.

  At the time of measuring the phase or phase difference in the optical sensor system 10B, the temperature fluctuation width (ΔT) in the first optical fiber 30 and the second optical fiber 31 is the same, and the frequency of the electromagnetic wave measured in the optical electric field sensors 12A and 12B. (Frq) is the same. When an electromagnetic wave is transmitted from another antenna, the electromagnetic wave is received by the optical sensor system 10B (antenna 29 of the first and second optical electric field sensors 12A and 12B).

  The first and second light sources 19A and 19B for the optical modulator emit laser light having a wavelength of 1.55 μm and an electric energy of 50 mW. The laser light enters the polarization beam combiner 16 from the light sources 19A and 19B through the polarization maintaining optical fiber 34, and is combined by the polarization beam combiner 16 into a combined laser beam whose polarization planes are orthogonal to each other. The combined laser light enters the optical coupler 17 through the optical fiber 18 and is divided into two by the optical coupler, and then enters the optical circulators 32A and 32B. The optical circulators 32A and 32B cause the combined laser light to enter the optical modulator 25 of the first and second optical electric field sensors 12A and 12B.

  In the reflection type optical modulator 25, as indicated by an arrow X1 in FIG. 9, the combined laser light emitted from the optical circulators 32A and 32B (polarization synthesizer 16) is a waveguide from the input / output port of the input / output optical waveguide 27a. 27a enters the waveguides 27b and 27c after being divided into two (demultiplexed) by the phase shift waveguides 27b and 27c. Thereafter, the modulated light modulated from the combined laser light is reflected by the light reflecting portion 33 and emitted from the input / output port of the input / output optical waveguide 27a to the optical fiber 18 (optical circulators 32A and 32B) as indicated by an arrow X2. The

  In the optical modulator 25, when a voltage is applied to the antenna 29 (between the extended portion 29 a of the antenna and the extended portions 29 b and 29 c) by the electric field strength (high frequency signal) of the electromagnetic wave received by the antenna 29, the directions are opposite to each other. Is applied to the phase shift optical waveguides 27b and 27c (in FIG. 4). By applying an electric field in the opposite direction to the phase shift optical waveguides 27b and 27c, the directions of refractive index change due to the electro-optic effect in the optical waveguides 27b and 27c are opposite to each other and propagate through the phase shift waveguides 27b and 27c. Phase shifts in opposite directions occur in the laser light (one of the combined laser lights). As a result, the laser beams reflected by the reflector 33 interfere with each other when coupled in the input / output optical waveguide 27a, and the intensity of the laser beams is modulated to become modulated light.

  The modulated light modulated by the optical modulator 25 is emitted from the input / output optical waveguide 27a, enters the first O / E converter 20A from the optical circulator 32A through the optical fiber 18 (optical fiber 30), and the optical fiber. 18 enters the second O / E converter 20B from the optical circulator 32B through 18 (optical fiber 31). These O / E converters 20A and 20B generate an electric signal obtained by converting the modulated light, and output the electric signal to the amplifiers 21A and 21B. The amplifiers 21A and 21B amplify the electrical signals output from the O / E converters 20A and 20B, and output the amplified electrical signals to the network analyzer 23.

  The network analyzer 23 receives the measurement points K1 received by the antennas 29 of the first and second optical electric field sensors 12A and 12B based on the electrical signals output from the amplifiers 21A and 21B (O / E converters 20A and 20B). The phase of the electromagnetic wave at K2 is measured, the phase difference of the electromagnetic wave between the measurement points K1 and K2 is obtained, and the measured phase and the obtained phase difference are stored in a memory and output from a display or a printer.

  The optical sensor system 10B uses the optical electric field sensors 12A and 12B to determine the phase difference between the measurement points K1 and K2 while measuring the phase of the electromagnetic waves propagating in the space at the measurement points K1 and K2. Compared with the case of measuring the phase of electromagnetic waves using two optical electric field sensors, the lengths L1 and L2 of the optical fibers 30 and 31 extending from the respective optical electric field sensors 12A and 12B and transmitting phase data are measured. Even if there is a variation (deviation) in the phase measured by each of the optical electric field sensors 12A and 12B due to change depending on the temperature environment, the second optical electric field with respect to the phase deviation amount measured by the first optical electric field sensor 12A. It can be easily proved that the phase shift amount measured by the sensor 12B is approximate, and the electromagnetic wave propagating in the space using each of the optical electric field sensors 12A and 12B. It can be measured phase with high reliability.

  When the optical sensor system 10B obtains the phase difference of the electromagnetic waves between the measurement points K1 and K2, the optical sensor system 10B corresponds to the length (L1) of the first optical fiber 30 that transmits the phase data emitted from the first optical electric field sensor 12A. ΔL ≦ ΔPh / so that the path difference (ΔL) (L1−L2) of the length (L2) of the second optical fiber 31 that transmits the phase data emitted from the second optical electric field sensor 12B is within an appropriate range. Since the length (L2) of the second optical fiber 31 is adjusted with respect to the length (L1) of the first optical fiber 30 using (0.0576 × Frq × ΔT), each optical electric field sensor 12A , 12B are not greatly deviated from each other, and a substantially accurate phase is measured by the optical electric field sensors 12A, 12B, and the measurement accuracy of the phase difference between the measurement points K1, K2 can be improved.

  The optical sensor system 10B changes the refractive index of the phase shift optical waveguides 27b and 27c according to the electric field strength of the electric signal received by the antenna 29 of the reflective optical modulator 25, and the input light passes through the phase shift optical waveguides 27b and 27c. Since the intensity of (synthetic laser light) is modulated, the measurement sensitivity of electromagnetic waves propagating in space can be increased, and the phase of the electromagnetic waves is measured only by the power of the received electromagnetic waves without supplying power from the outside. be able to.

  The optical sensor system 10B can increase the electromagnetic wave measurement efficiency by using the reflective optical modulator 25, and the path difference (ΔL) (L1-L2) between the optical fibers 30 and 31 is within an appropriate range. Since the length (L2) of the second optical fiber 31 is adjusted with respect to the length (L1) of the first optical fiber 30, the measurement points K1 are measured by the optical electric field sensors 12A and 12B. , K2 can reliably improve the measurement accuracy of the phase difference.

DESCRIPTION OF SYMBOLS 10A Optical sensor system 10B Optical sensor system 11 Transceiver 12A 1st optical electric field sensor 12B 2nd optical electric field sensor 13 Optical transmission part 14 Optical receiving part 15 Light source for optical modulators 16 Polarization combiner 17 Optical coupler 18 Single mode optical fiber 19A First light source for optical modulator 19B Second light source for optical modulator 20A First O / E converter 20B Second O / E converter 21A First amplifier 21B Second amplifier 24 Housing antenna 25 Optical modulator 26 Single crystal substrate (substrate)
27 Mach-Zehnder type optical waveguide (optical waveguide)
27a Input optical waveguide (input / output optical waveguide)
27b Phase shift optical waveguide 27c Phase shift optical waveguide 27d Output optical waveguide 28 Buffer layer 29 Antenna 29a Extension part 29b Extension part 29c Extension part 30 First optical fiber 31 Second optical fiber 32A Optical circulator 32B Optical circulator 33 Optical reflector 34 Polarization Wave holding optical fiber K1 First measurement point K2 Second measurement point

Claims (6)

In the case where the phase difference between at least two measurement points is obtained while measuring the phase at least two measurement points of the electromagnetic wave propagating in the space using at least two optical electric field sensors, the first optical electric field of these optical electric field sensors The length (L2) of the second to n-th optical fibers transmitting the phase data emitted from the second to n-th optical electric field sensors with respect to the length (L1) of the first optical fiber transmitting the phase data emitted from the sensor path difference) (ΔL) (L1-L2 ) is, the phase of one of the plus 2m and minus 2m capable of measuring accurately at least one of relative change in temperature environment during measurement of the phase The length (L2) of the second to nth optical fibers is adjusted with respect to the length (L1) of the first optical fiber so as to be within an appropriate range, and the path difference (ΔL) is expressed by the formula: ΔL ≦ Calculated by Ph / (0.0576 × Frq × ΔT) (ΔL = path difference [m], ΔPh = phase shift difference [deg], Frq = electromagnetic wave frequency [GHz], ΔT = measurement time Temperature fluctuation range [° C.], 0.0576 = phase coefficient [deg / GHz · ° C. · m])) . When measuring the phase of the electromagnetic wave in the optical sensor system, the temperature fluctuation width (ΔT) in the first to nth optical fibers is the same, and the frequency (Frq) of the electromagnetic wave sensed in the optical electric field sensor is the same. light sensor system according to claim 1 is. 3. The optical sensor system according to claim 1, wherein at the time of measuring the phase of the electromagnetic wave in the optical sensor system, phase measurement points by the first to n-th optical electric field sensors are close to each other . The optical sensor system receives predetermined electromagnetic waves, modulates the intensity of input light according to the electric field intensity of the electromagnetic waves, and outputs the modulated light obtained by modulating the input light; and Connected to the optical electric field sensor via an optical fiber having a predetermined length, and connected to the optical electric field sensor via an optical fiber having a predetermined length, and a light source for an optical modulator that emits the input light. An O / E converter that converts the modulated light emitted from the optical electric field sensors into an electric signal, and the length of the first to nth optical fibers is the output side of the first to nth optical electric field sensors. the O / E converter optical sensor system according to claim 3 or to the claims 1 to length of the optical fiber connecting the input side of the. The optical modulator includes a substrate made of a material having an electro-optic effect, an optical waveguide formed on the substrate, and an antenna installed in the vicinity of the optical waveguide, and the optical waveguide is configured to receive light. An input optical waveguide extending to the side, two phase shift waveguides extending bifurcated from the input optical waveguide, and an output optical waveguide extending to the light output side and connected to the phase shift optical waveguide The antenna extends in the extension direction in parallel with the phase shift waveguides, and the electric field strength of the electric signal is independently applied to the phase shift waveguides to thereby adjust the refractive index of the phase shift optical waveguides. light sensor system according to any one of claims 4 to claims 1 vary. The optical modulator is a substrate made of a material having an electro-optic effect, an optical waveguide formed on the substrate, and a light reflecting portion that is installed on the substrate and reflects light propagating through the optical waveguide. And an antenna installed in the vicinity of the optical waveguide, the optical waveguide extending to the input side of the light, the input / output optical waveguide extending in a bifurcated manner from the input / output optical waveguide, and extending to the light reflecting portion And the antenna extends in the extension direction in parallel with the phase shift waveguides and applies the electric field strength of the electric signal to the phase shift waveguides independently. light sensor system according to any claims 1 to 4 to change the refractive index of the phase shift optical waveguides by.

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