Electromagnetic wave detection device and driving method thereof

Abstract

An embodiment of the present invention relates to an electromagnetic wave detection device for detecting an electromagnetic wave, the electromagnetic wave detection device comprising: a light source; an electromagnetic wave probe for outputting light modulated to correspond to the electromagnetic wave; a polarization control unit for applying strain to an optical fiber, transmitting the light provided by the light source, and thereby controlling the polarization of the light provided to the electromagnetic wave probe; an optical power meter for measuring the power of the light generated in the electromagnetic wave probe; and a control unit for controlling the polarization control unit so that the power of the light generated in the electromagnetic wave probe converges at a target power provided by a user.

Description

Electromagnetic wave detection device and driving method thereof

[0001] The present disclosure generally relates to an electromagnetic wave detection device and a method of driving the same.

[0002] Recent remarkable social, economic, and informatization developments have led to rapid advancements in wireless communication technologies, such as mobile phones. This progress stems from the development of various high-frequency components and the reduction and miniaturization of systems. Beyond communications systems, advancements in the electromagnetic wave-based technology industry have led to the development of a variety of household, medical, and industrial devices. In particular, the development of high-speed digital equipment capable of processing large amounts of data is underway.

[0003] However, along with the advancement of technology, interest in electromagnetic interference between equipment and equipment and between equipment and the human body is increasing day by day, and in order to protect the human body from the harm of short-range electromagnetic waves, each country has set the maximum permissible exposure (MPE) of electric and magnetic fields or power density.

[0004] Electromagnetic waves are generated in the electromagnetic field region and are difficult to measure and calculate using any electronic device. The need to accurately measure electromagnetic waves is increasing day by day for resolving civil complaints and developing and verifying electronic communication systems.

[0005] Among the technologies for measuring electromagnetic waves, one that utilizes electro-optic crystals, whose refractive index changes in response to an electric field, is gaining traction. This technology measures electromagnetic waves based on the relationship between the polarization direction of the electromagnetic wave and the extraordinary refractive index (ne) and ordinary refractive index (no) axes of the electro-optic crystal.

[0006] The technology for measuring electromagnetic waves using electro-optical crystals measures electromagnetic waves by providing light from a light source to the electro-optical crystal via an optical cable. However, even slight movements of the optical cable can cause the polarization of the light reaching the electro-optical crystal to change, making it difficult to optimally control the polarization provided to the electro-optical crystal. Furthermore, the wavelength of the light provided by the light source and the optical properties associated with the electro-optical crystal can change (drift) depending on the temperature of the environment in which the electro-optical crystal is located, making it difficult to measure electromagnetic waves with the desired precision.

[0007] One of the challenges that this technology aims to address is to overcome the difficulties of the above-mentioned conventional technologies.

[0008] The present embodiment is an electromagnetic wave detection device for detecting electromagnetic waves, the electromagnetic wave detection device including: a light source; an electromagnetic wave probe for outputting light modulated to correspond to the electromagnetic wave; a polarization control unit for controlling polarization of light provided to the electromagnetic wave probe by applying strain to an optical fiber that transmits light provided by the light source; an optical power meter for measuring power of light formed in the electromagnetic wave probe; and a control unit for controlling the polarization control unit so that power of light formed in the electromagnetic wave probe converges to a target power provided by a user.

[0009] According to one aspect of the present embodiment, the polarization control unit includes one or more wave plate modules, wherein the wave plate modules include: a wave plate for applying strain to the optical fiber and a motor for pivoting the wave plate.

[0010] According to one aspect of the present embodiment, the wave plate is one of a 1 / 2 wavelength wave plate and a 1 / 4 wavelength wave plate.

[0011] According to one aspect of the present embodiment, the control unit pivots the wave plate in a first direction so as to reduce a difference between a target power provided by the user and the power of light formed from the electromagnetic wave probe.

[0012] According to one aspect of the present embodiment, the control unit pivots the wave plate further in the first direction when the difference between the target power provided by the user and the power of light formed from the electromagnetic wave probe decreases.

[0013] According to one aspect of the present embodiment, the control unit pivots the wave plate in a second direction opposite to the first direction when the difference between the target power provided by the user and the power of light formed from the electromagnetic wave probe increases by pivoting in the first direction.

[0014] According to one aspect of the present embodiment, the polarization control unit includes a plurality of wave plate modules, and the control unit sequentially controls the plurality of wave plate modules.

[0015] According to one aspect of the present embodiment, the target power provided by the user is 0.

[0016] According to one aspect of the present embodiment, the control unit further receives data from the user on one or more of the temperature of the light source, the wavelength of light provided by the light source, and the wavelength range of light provided by the light source, and controls the light source to provide light of a wavelength corresponding to the provided data.

[0017] According to one aspect of the present embodiment, the electromagnetic wave detection device further includes an optical circulator and an optical coupler, wherein the optical circulator provides light provided by the polarization control unit to the electro-optical probe, provides light formed in the electro-optical probe to the optical coupler, and the optical coupler outputs the light provided by the optical circulator to the optical power meter and the demodulator at a predetermined ratio.

[0018] The present embodiment relates to a driving method of an electromagnetic wave detection device that detects electromagnetic waves, the driving method comprising: a step of receiving a target power value from a user; a step of measuring the power value of light formed from an electromagnetic wave probe and comparing it with the target power value; and a step of pivoting a wave plate in a first direction when the power value of light formed from the electromagnetic wave probe is less than the target power value, and pivoting the wave plate in a second direction when the power value of light formed from the electromagnetic wave probe is greater than or equal to the target power value.

[0019] According to one aspect of the present embodiment, the electromagnetic wave detection device includes a plurality of wave plates and sequentially controls the plurality of wave plates one by one.

[0020] According to one aspect of the present embodiment, in the input receiving step, the number of repetitions is further input from the user, and control is performed by pivoting the number of repetitions for one of the wave plates,

[0021] According to one aspect of the present embodiment, in the input receiving step, one or more data of the temperature of the light source, the wavelength of light provided by the light source, and the wavelength range of light provided by the light source are further provided from the user.

[0022] According to one aspect of the present embodiment, at least one of the temperature of the light source provided by the user, the wavelength of the light provided by the light source, and the wavelength range of the light provided by the light source determines the operating point of the electromagnetic wave probe, and the controlling step is performed so that the electromagnetic wave probe does not deviate from the operating point.

[0023] According to this embodiment, a stable electromagnetic wave detection device is provided even in the presence of physical disturbances.

[0024] Fig. 1 is a schematic diagram schematically illustrating an electromagnetic wave detection device according to the present embodiment.

[0025] Figure 2 is a drawing for explaining the operating point of an electro-optical probe.

[0026] Figure 3 is a drawing illustrating an outline of a polarization control unit.

[0027] Fig. 4 is a drawing illustrating an outline of an electro-optical probe according to the present embodiment.

[0028] Figure 5 is a schematic cross-sectional view showing an enlarged portion of one end of an optical fiber.

[0029] Figure 6 is a schematic cross-sectional view of an optical fiber core and an electro-optic crystal to explain the behavior of light.

[0030] Figure 7 is a drawing for explaining the electro-optical characteristics of an electro-optical crystal.

[0031] Figure 8 is an exemplary flowchart of a method in which a control unit controls a polarization control unit.

[0032] Figure 9 is a drawing for explaining resonance characteristic control.

[0033] Fig. 10 is a drawing schematically explaining the operation of an electromagnetic wave detection device according to the present embodiment.

[0034] Hereinafter, the present embodiment will be described with reference to the attached drawings. An electromagnetic wave detection device (10) will be described with reference to FIG. 1. FIG. 1 is a schematic diagram schematically illustrating an electromagnetic wave detection device (10) according to the present embodiment. Referring to FIG. 1, the electromagnetic wave detection device (10) includes a light source (200), a polarization control unit (900) that changes the polarization of light provided from the light source, an electromagnetic wave probe (100) that outputs modulated light modulated to correspond to the detected electromagnetic wave, an optical power meter (700) that detects the modulated light and outputs it as a corresponding electrical signal, and a control unit (400) that controls the electromagnetic wave detection device.

[0035] A user provides input parameters via an input device (not shown). The input parameters may include a target power value of light formed by an electro-optical probe (100), an optical parameter for controlling light provided by a light source (200), and a polarization control parameter for controlling a polarization control unit (900). The optical parameter includes at least one of a wavelength, a wavelength range, a power, and a temperature of the light to be output by the light source (200). The polarization control parameter includes a parameter for controlling a strain provided to a wave plate (912).

[0036] The light source (200) outputs light of a wavelength corresponding to the light parameters provided by the user. In one embodiment, the light source (200) may be a laser light source, such as a laser diode, that outputs light of a predetermined wavelength. In one embodiment of the light source (200), a laser light source, such as a laser diode, may experience a wavelength drift due to temperature. Accordingly, the control unit (400) may control the temperature of the light source (200) to control the wavelength of the light output by the light source (200). The laser light source (200) may include a temperature control unit that stabilizes the wavelength of the light it outputs.

[0037] FIG. 2 is a drawing for explaining the operating point of the electro-optical probe (100). Referring to FIG. 2, the control unit (400) sets the operating point (bias point) of the electromagnetic wave detection device (10) from the optical parameters provided by the user, and controls the light source (200) so that the light source (200) outputs light of a desired wavelength. In another embodiment, the control unit (400) may set the point with the largest slope in the graph of the reflected light (R) against the wavelength of the input light as the operating point (bias point), as exemplified in FIG. 2. In another example, the control unit (400) may set the operating point (bias point) where the differential value in the graph of the reflected light (R) against the wavelength of the input light is within the desired range.

[0038] For example, the control unit (400) sets the wavelength of light provided by the light source (200) so that the electro-optical probe (100) operates at an operating point of 10% to 60% where the differential value of the reflected light (R) component becomes large and constant. The control unit (400) can control the temperature control unit of the light source (200) so that the light source (200) outputs light of a desired wavelength.

[0039] When an operating point (bias point) is set and an electromagnetic wave is provided to the electromagnetic wave detection probe (100), the light formed in the electromagnetic wave detection probe (100) includes a modulated light component formed by modulating the provided light due to a change in the refractive index (ne) of the electro-optic crystal (120) and a reflected light component formed by reflection from the electro-optic crystal. Since the operating point (bias point) of the electromagnetic wave detection probe (100) is set so that the modulated light changes significantly with respect to a change in the wavelength of the provided input light, detection can be easily performed.

[0040] FIG. 3 is a diagram illustrating an overview of a polarization control unit (900). Referring to FIG. 1 and FIG. 3, the polarization control unit (900) includes one or more wave plate modules (910) that control the polarization of light provided by a light source (200). Each wave plate module (910) includes a wave plate (912) wound with an optical fiber (110), a motor (914) that pivots the wave plate (912) around a pivot axis (A) according to a control signal provided by the control unit (400), and an interface to which the control signal output by the control unit (400) is provided.

[0041] An optical fiber (110) is wound around a wave plate (912). Since the optical fiber (110) has a radius of curvature and is wound around the wave plate (912), strain is formed on the outer and inner sides of the core (112, see FIG. 3) of the optical fiber (110) through which light is transmitted. This creates a difference in the optical length of the path along which light travels, and thus, by controlling the strain, the polarization of light provided to the electro-optical crystal (120, see FIG. 3) can be controlled.

[0042] In one embodiment, the wave plate (912) may be either a quarter wave plate capable of forming a phase difference corresponding to a quarter wavelength of light output by the light source (200), or a half wave plate capable of forming a phase difference corresponding to a half wavelength. In addition, the polarization control unit (900) may include a plurality of wave plates.

[0043] The control unit (400) controls the wave plate (912) so that the power value of light detected by the optical power meter (700) approaches the target power value specified by the user, and the details will be described later.

[0044] FIG. 4 is a drawing illustrating an outline of an electro-optical probe (100) according to the present embodiment. Referring to FIG. 4, the electro-optical probe (100) according to the present embodiment includes an electro-optical structure (160) including an optical fiber (110), an electro-optical crystal (120) positioned at one end of the optical fiber (110), a first reflector (130) positioned at a first surface of the electro-optical crystal and facing the one end of the core, and a second reflector (140) positioned at a second surface of the electro-optical crystal.

[0045] Fig. 5 is a schematic cross-sectional view showing an enlarged portion (110e) of an optical fiber (110). Referring to Figs. 4 and 5, the optical fiber (110) may include a core (112) having a first refractive index and a cladding (114) having a lower refractive index than the first refractive index, and light provided to the core propagates through total internal reflection (TIR).

[0046] In one embodiment, the core (112) is expanded at one end (110e) of the optical fiber (110) facing the electro-optical structure (160). In one embodiment, the core (112) may be expanded by performing a heat treatment.

[0047] Therefore, the diameter (Dex_core) of the core (112) at one end (110e) is larger than the diameter (Dcore) of the core (112) of the optical fiber (110). For example, the diameter (Dcore) of the core (112) of the optical fiber (110) may be approximately 10 μm, and the diameter (Dex_core) of the core (112) at one end (110e) may increase to approximately 30 μm. Therefore, the area facing the first reflector may increase nine times. In addition, since an optical pattern is formed in the vicinity of the optical fiber (110) similar to parallel light in free space, the optical coupling coefficient (C) between the optical fiber (110) and the optical crystal (120) may increase. However, as in an embodiment not shown, one end of the core may not be expanded.

[0048] The coupling coefficient value of the optical fiber (110) according to the prior art was only 0.2 to 0.3. However, according to the present embodiment, as the diameter of the core (112) is expanded at one end, a light pattern is formed in the vicinity of the optical fiber (110) similar to parallel light in free space, so that the coupling coefficient value can have a value of 0.3 to 0.9, and can be improved by up to three times or more depending on the embodiment.

[0049] The electro-optical structure (160) may include an electro-optical crystal (120) and a first reflector (130) and a second reflector (140). The electro-optical crystal (120) may be formed of a material having two refractive indices, an extraordinary refractive index (ne) and an ordinary refractive index (no), to cause birefringence. For example, the electro-optical crystal may be lithium tantalate (LT, LiTaO3: lithium tantalate) and lithium niobate (LN, LiNbO3: lithium niobate). As another example, the electro-optical crystal may be an electro-optical material having only an ordinary refractive index and no extraordinary refractive index, such as gallium arsenide (GA, GaAs: gallium arsenide), zinc telluride (ZT, ZnTe: zinc telluride), or cadmium telluride (CT, CdTe: cadminum telluride). As another example, the electro-optical crystal may be a material having multiple ideal refractive indices, such as DAST (4-N,N-dimethylamino-4-N-methyl-stilbazolium tosylate). In FIG. 1, the electro-optical crystal (120) is illustrated as a hexahedron with a thickness d, but in another example not shown, the electro-optical crystal (120) may be in the form of a wafer with a thickness d.

[0050] The first reflector (130) and the second reflector (140) can be formed by laminating two material layers having different refractive indices, and the thickness of the laminated material layers, the number of laminated layers, and the refractive indices of the laminated materials can be modified in various ways. For example, the first reflector (130) and the second reflector (140) can be formed by alternately laminating material layers having different refractive indices, such as zinc selenide (ZnSe) and magnesium fluoride (MgF2).

[0051] When the reflectivity of the first reflector (130) and the second reflector (140) is r, r2 can be in the range of 1% to 99% in terms of power. For example, the first reflector (130) and the second reflector (140) can be manufactured to have the same or different reflectivities, which serve as efficient resonators that allow the laser light to remain in the electro-optical crystal for a long time.

[0052] In one embodiment of the electro-optical structure (160), the electro-optical structure (160) may further include an optical adhesive (140) that bonds one end of the optical fiber (110) and the first reflector (130). The optical adhesive (140) has optically transparent properties with respect to light provided through the core (112).

[0053] Hereinafter, the operation of the electro-optical probe (100) according to the present embodiment will be described with reference to FIGS. 6 and 7. FIG. 6 is a schematic cross-sectional view of an optical fiber (110) core (112) and an electro-optical crystal (120) for explaining the behavior of light. Referring to FIG. 6, the size of the light transmitted through the core (112) is normalized to 1. The reflectivity and transmittance of the first reflector (130) are r1 and t1, respectively, and the reflectivity and transmittance of the second reflector (140) are r2 and t2, respectively. In addition, the extraordinary refractive index of the optical crystal (120) is ne, and the thickness of the optical crystal (120) is d.

[0054] The incident light provided may not be transmitted through the electro-optical crystal (120) but may be reflected from the first reflector (130). If the reflected light component at this time is R1, then R1 = r1. However, if the incident light is transmitted through the electro-optical crystal (120) and progresses as a component of t1, and if the component that is reflected from the second reflector (140) and then transmitted through the first reflector (130) again is R2, then R2 = Ct1 2 r2e iδcan be expressed as . δ is the phase difference according to the round-trip optical path in the electro-optic crystal (120), and δ = (2πned) / (λ). (ne: ideal refractive index of the electro-optic crystal, d: thickness of the electro-optic crystal, λ: wavelength of light)

[0055] Similarly, if we find the R3 component, R3 = (Ct1) 2 r2e iδ (-r1r2e iδ ) can be expressed as. The reflected light component for the incident light theoretically has an infinite geometric series of components, and all the infinite components are combined to form the reflected light component. Therefore, if the reflected light component is R, the reflected light component (R) can be expressed as in the following mathematical expression 1.

[0056]

[0057] Unlike free space, light emitted from an optical fiber (110) is spatially divergent. Considering the numerical aperture (NA) of the optical fiber (110), only a portion of the emitted light is recombined into the core (120), and the mode field diameter (MFD) of the core where the light of a typical optical fiber (110) is focused is only 10 μm. However, in the present embodiment, the cross-section of the core (110) is expanded at one end (110e) of the optical fiber (110). For example, if the diameter of the core increases by a factor of three due to the expansion, the numerical aperture decreases to approximately 1 / 9. Therefore, by expanding the diameter of the core at the end (110e) of the optical fiber (110), a light pattern near the optical fiber (110) is formed similar to parallel light in free space, thereby increasing the coupling coefficient (C), and improving the rate at which the emitted light is recombined into the core (120). According to this embodiment, the coupling coefficient value of the optical fiber (110) having a core with an extended end may have a value of 0.3 to 0.9.

[0058] Fig. 7 is a drawing for explaining the electro-optical characteristics of an electro-optical crystal (120). Referring to Fig. 7, as described above, the electro-optical crystal (120) has a birefringent characteristic in which the refractive index changes depending on the growth direction of the crystal. In addition, the electro-optical crystal (120) has a characteristic in which the refractive index of the crystal changes in proportion to an electric field applied in a specific direction.

[0059] For example, the refractive index of lithium tantalate (LT: LiTaO3) has a positive uniaxial structure in which one axis has a slightly larger refractive index than the other two axes in a three-dimensional coordinate system, as shown in Fig. 7(a). Fig. 7(a) is a refractive index distribution (index ellipsoid) when the largest refractive index (ne) is set in the z direction, and a cross-section including the z axis has independent refractive index distributions of ne and no, as shown in Fig. 7(b). For example, at a wavelength of 1550 nm, ne and no have values ​​of 2.1224 and 2.1186, respectively.

[0060] When an electric field Ez polarized in the same direction as the ideal refractive index ne is applied, the refractive index changes (Δnz(Ez)). The change in the refractive index changes the value of ne in Equation 1, and as a result, the incident light is modulated to correspond to an electromagnetic wave. Therefore, by demodulating the modulated light in an optical-electromagnetic manner, the characteristics of the electromagnetic wave applied to the optical crystal can be measured.

[0061] Referring again to FIG. 1, when the wavelength of light provided through the optical fiber (110) corresponds to the resonant wavelength, it resonates within the electro-optic crystal (120) by the first reflector (130) and the second reflector (140), and this is called Fabry-Perot resonance.

[0062] The electromagnetic wave detection device (10) includes an optical circulator (500) and an optical coupler (600). The optical circulator (500) provides light output from a polarization control unit (900) to an electromagnetic wave probe (100), and provides light including a modulated light component and a reflected light component formed in the electromagnetic wave probe (100) to the optical coupler (600).

[0063] The optical coupler (600) distributes the light output from the optical circulator (500) according to a preset ratio, providing some in one direction and providing the other in the other direction. As in the illustrated embodiment, the optical coupler (600) outputs the modulated light detected and output by the electromagnetic wave probe (100) to the demodulator (300) and the optical power meter (700), respectively.

[0064] The optical power meter (700) detects the modulated light formed in the electro-optical probe (100) through the optical coupler (600) and outputs it to the control unit (400). The demodulation unit (300) includes a conversion unit (310). In one embodiment, the conversion unit (310) includes a photoelectric conversion element such as a photodiode or an avalanche photodiode, and a transfer impedance amplifier that converts a photocurrent signal provided by the photoelectric conversion element into a voltage signal. Therefore, the demodulation unit (300) can form and output an electric signal corresponding to an electromagnetic wave detected by the electro-optical probe (100).

[0065] In an embodiment not shown, the signal formed in the demodulator may be provided to an analysis device. For example, the analysis device may be an analysis device such as a spectrum analyzer or an oscilloscope, and the properties of the electromagnetic waves converted into electrical signals can be analyzed.

[0066] The control unit (400) determines whether the electro-optical crystal (120) resonates from the modulated light and controls the polarization control unit (900) by determining whether the power of the modulated light corresponds to the target power value provided by the user as an input parameter.

[0067] Fig. 8 is an exemplary flowchart of a method in which a control unit (400) controls a polarization control unit (900). Referring to Figs. 1, 2, and 8, the control unit (400) obtains input parameters from a user (S100). The input parameters provided by the user include a target power value of light formed from an electro-optical probe, an optical parameter for controlling light provided by a light source (200), and a polarization control parameter for controlling the polarization control unit (900).

[0068] The optical parameters include at least one of the wavelength, wavelength range, power of the light, and temperature of the light source to be output by the light source (200). The polarization control parameters include parameters for controlling the strain provided to the optical fiber (110) as described above. The parameters for controlling the strain include the number of iterations for pivoting the wave plate (912) to control the strain in a unit period in which the control unit (400) controls one wave plate module (910). In one embodiment, when the polarization control unit (900) includes a plurality of wave plate modules, the user can specify the number of iterations for pivoting the wave plate (912) included in each module to control the strain using the polarization control parameters.

[0069] Among the two wave plate modules (910), one wave plate module (910) to be controlled is set (S200). The wave plate module (910) to be controlled at the time of initial operation may be set in advance, and as described later, when the number of control repetitions for the wave plate module (910) to be controlled is reached, the wave plate module (910) to be controlled is switched.

[0070] The control unit (400) compares the power value of the modulated light detected by the optical power meter (700) with the target power value specified by the user as an input parameter (S300). If the power value detected by the electro-optical probe (100) as a result of the comparison is greater than the target power value input as an input parameter, the control unit (400) provides a control signal to the motor (914) included in the wave plate module (910) as a control target to pivot the wave plate (912) around which the optical fiber (110) is wound in a first direction (S400b). It is determined whether the difference between the modulated light power value detected as a result of the pivot and the target power value decreases (S600b), and if the difference decreases, the control unit (400) controls the motor to pivot the wave plate (912) around which the optical fiber (110) is wound in the first direction, which is the same as the previous pivot direction (S400b).

[0071] On the other hand, if the difference between the modulated light power value detected as a result of pivoting and the power value of the desired modulated light does not decrease, the control unit (400) controls the motor to pivot the wave plate (912) around which the optical fiber (110) is wound in a second direction opposite to the previous pivot direction (S400a).

[0072] The user specifies the number of times the control unit pivots one wave plate module (910) as the number of repetitions. Therefore, after determining whether the number of repetitions has been reached (S500a, S500b), if the number of repetitions has been reached, the wave plate module (910) to be controlled is switched.

[0073] In the illustrated embodiment, after the initial operation, when the number of repetitions is reached, the wave plate module (910) to be controlled is switched to continuously control the wave plate (912) by comparing the power value of the detected modulated light with the target power value specified by the user. In the above-described process, the control unit (400) controls the motor (914) to pivot the wave plate (912), thereby controlling the strain provided to the optical fiber (110), and thereby controlling the polarization of the light provided to the electro-optic crystal (160) connected to the end of the optical fiber (110). In addition, even if there is a large external fluctuation, the advantage of being able to quickly converge the power value of the detected modulated light to the power value of the modulated light specified by the user is provided.

[0074] Fig. 9 is a diagram for explaining resonance characteristic control. In Fig. 9, when the polarization control unit (900) includes two λ / 4 wave plate modules (WP1, WP2), it is a diagram showing the change in reflectivity of reflected light according to their pivot angles. Referring to Figs. 1 and 9, it can be confirmed that the deviation of reflected light varies greatly, from 0% to 90%, depending on the change in the pivot angle of the electro-optic probe (100).

[0075] Since electro-optical probes utilize resonance characteristics, it is desirable for the resonance characteristics to be maximized at the resonance wavelength. Minimizing reflected light at the resonance wavelength maximizes the resonance characteristics, optimizing sensor performance. Therefore, the polarization control unit (900) is configured to maximize and maintain the resonance characteristics.

[0076] Fig. 10 is a drawing schematically explaining the operation of the electromagnetic wave detection device (10) according to the present embodiment. The curve shown in the dashed line in Fig. 10 illustrates a case where the polarization of light provided to the electro-optical crystal does not match. For example, the resonance characteristic shown in the solid line deteriorates as shown in the dotted line when the optical fiber (110) connected to the electro-optical probe from the optical circulator port is shaken. In this case, the same reflected light is maintained by temperature control. However, the slope becomes more gentle, resulting in deterioration of the modulation efficiency.

[0077] At this time, the polarization control unit can control the polarization of the light provided to the electro-optical crystal by performing the process illustrated in Fig. 8, thereby operating the sensor at the operating point where the slope shown by the solid line is the steepest in the state shown by the broken line. By controlling the rotation of the wave plate in the direction where the previously measured optical power value becomes smaller, the operating point can be maintained in a state where the slope is steep and the modulation performance is excellent.

[0078] For example, if the target optical power is set to the minimum value of 0, the control unit rotates all wave plates in the direction that maximizes the constant resonance characteristics. Separately, since the optical power can be maintained at a value corresponding to the operating point rather than the minimum value by controlling the temperature of the laser wavelength, the operating point with the maximum slope, shown by the solid line in Fig. 10, can be constantly maintained through polarization control by the wave plate and temperature control of the laser.

[0079] Therefore, the drift caused by polarization and ambient temperature changes during long-term operation of the sensor can be maintained as reflected light corresponding to a constant operating point through real-time polarization control and temperature control of the laser.

[0080]

[0081] While the present invention has been described with reference to the embodiments illustrated in the drawings to aid understanding, these are merely exemplary embodiments for practical purposes. Those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible. Therefore, the true technical protection scope of the present invention should be defined by the appended claims.

Claims

1. An electromagnetic wave detection device that detects electromagnetic waves, wherein the electromagnetic wave detection device: light source; An electromagnetic wave probe that outputs light modulated to correspond to the above electromagnetic waves; A polarization control unit that controls the polarization of light provided to the electromagnetic wave probe by applying strain to an optical fiber that transmits light provided by the light source; An optical power meter for measuring the power of light formed from the electromagnetic wave probe; An electromagnetic wave detection device including a control unit that controls the polarization control unit so that the power of light formed from the electromagnetic wave probe converges to a target power provided by a user.

2. In paragraph 1, The above polarization control unit, Comprising one or more wave plate modules, said wave plate modules comprising: A wave plate for applying strain to the optical fiber; and An electromagnetic wave detection device comprising a motor pivoting the above wave plate.

3. In paragraph 2, The above wave plate, An electromagnetic wave detection device, which is either a 1 / 2 wavelength wave plate or a 1 / 4 wavelength wave plate.

4. In paragraph 2, The above control unit, An electromagnetic wave detection device that pivots the wave plate in a first direction so as to reduce the difference between the target power provided by the user and the power of light formed from the electromagnetic wave probe.

5. In paragraph 2, The above control unit, Pivot in the first direction above An electromagnetic wave detection device that further pivots the wave plate in the first direction when the difference between the target power provided by the user and the power of light formed from the electromagnetic wave probe decreases.

6. In paragraph 5, The above control unit, Pivot in the first direction above An electromagnetic wave detection device that pivots the wave plate in a second direction opposite to the first direction when the difference between the target power provided by the user and the power of light formed from the electromagnetic wave probe increases.

7. In paragraph 2, The above polarization control unit, Contains multiple wave plate modules, The above control unit, An electromagnetic wave detection device that sequentially controls the above plurality of wave plate modules.

8. In paragraph 1, An electromagnetic wave detection device whose target power provided by the above user is 0.

9. In paragraph 1, The above control unit, Further receiving data on one or more of the temperature of the light source, the wavelength of light provided by the light source, and the wavelength range of light provided by the light source from the user; An electromagnetic wave detection device that controls the light source to provide light of a wavelength corresponding to the provided data.

10. In paragraph 1, The above electromagnetic wave detection device, It further includes an optical circulator and an optical coupler. The above optical circulator, The light provided by the above polarization control unit is provided to the electro-optical probe, and the light formed by the electro-optical probe is provided to the optical coupler. The above optical coupler, An electromagnetic wave detection device that outputs light provided by the optical circulator to the optical power meter and demodulator at a predetermined ratio.

11. A driving method of an electromagnetic wave detection device that detects electromagnetic waves, wherein the driving method is: A step of receiving a target power value from a user; A step of measuring the power value of light formed from an electromagnetic wave probe and comparing it with the target power value; A method for driving an electromagnetic wave detection device, comprising the steps of pivoting the wave plate in a first direction if the power value of light formed from the electromagnetic wave probe is less than the target power value, and pivoting the wave plate in a second direction if the power value of light formed from the electromagnetic wave probe is greater than or equal to the target power value.

12. In paragraph 11, The above electromagnetic wave detection device, Contains multiple wave plates, A driving method of an electromagnetic wave detection device that sequentially controls the above plurality of wave plates one by one.

13. In paragraph 12, At the above input receiving step, Get more repetitions input from the above user, After performing the control by pivoting the number of repetitions for each of the above wave plates, A driving method of an electromagnetic wave detection device that performs control by pivoting the number of repetitions for the other said wave plate.

14. In paragraph 11, At the above input receiving step, A method for driving an electromagnetic wave detection device, wherein the device further receives data on one or more of the temperature of a light source, the wavelength of light provided by the light source, and the wavelength range of light provided by the light source from the user.

15. In paragraph 11, One or more of the temperature of the light source provided by the user, the wavelength of the light provided by the light source, and the wavelength range of the light provided by the light source determine the operating point of the electromagnetic wave probe. A method for driving an electromagnetic wave detection device, wherein the controlling step is performed so that the electromagnetic wave probe does not deviate from the operating point.

Images