Current sensor and measurement device

Abstract

To provide a compact and highly reliable current sensor and a measurement device.SOLUTION: A current sensor according to an embodiment comprises first and second optical waveguides, and a polarizing rotator optically connected to the first and second optical waveguides.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to current sensors and measurement devices. [Background technology]

[0002] Current measurement devices are used to monitor and control a variety of facilities and equipment, including power facilities. Current transformers, which are made up of an iron core and windings and use the principle of electromagnetic induction, are limited in terms of insulation resistance and miniaturization, while optical current sensors can significantly reduce electrical insulation issues, especially in facilities that handle high voltages. They also do not suffer from the magnetic saturation that is a problem with current transformers, have good frequency characteristics even at high currents, and can measure from direct current to high frequencies. Optical current sensors mainly utilize the Faraday effect.

[0003] Although there are methods that achieve this by aligning the optical axes of bulk crystal blocks, mirrors, and lenses, and methods that use optical fibers as Faraday elements, the large size of all of these methods poses a challenge. Furthermore, attempts to achieve miniaturization require the optical axis adjustment between each optical component during the manufacturing process, which causes reflections due to gaps between components, making it impossible to transmit signals correctly. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-271292 [Non-patent literature]

[0005] [Non-Patent Document 1] T. IEE Japan, Vol. 114-B, No. 1, p.11-18 (1994) Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a small and highly reliable current sensor and measuring device. [Means for solving the problem]

[0007] According to an embodiment, there is provided a current sensor comprising a first optical waveguide, a second optical waveguide, and a polarization rotator optically connected to the first optical waveguide and the second optical waveguide. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating an example of the structure of a current sensor according to an embodiment. [Figure 2] 1 is a schematic diagram illustrating an example of the structure of a current sensor according to an embodiment. [Figure 3] 1 is a schematic diagram illustrating an example of the structure of a current sensor according to an embodiment. [Figure 4] FIG. 10 is a schematic diagram illustrating a modification of the current sensor according to the embodiment. [Figure 5] FIG. 10 is a schematic diagram illustrating a modification of the current sensor according to the embodiment. [Figure 6] FIG. 10 is a schematic diagram illustrating a modification of the current sensor according to the embodiment. [Figure 7] FIG. 10 is a schematic diagram illustrating a modification of the current sensor according to the embodiment. [Figure 8] FIG. 10 is a schematic diagram illustrating a modification of the current sensor according to the embodiment. [Figure 9] 1 is a schematic diagram illustrating a connection structure of a current sensor according to an embodiment. [Figure 10] FIG. 1 is a schematic diagram illustrating a measurement device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described with reference to the drawings. In the following description, components that perform the same or similar functions are designated by the same reference numerals throughout the drawings, and redundant description will be omitted. Each drawing is a schematic diagram for explaining and facilitating understanding of the embodiments, and the shapes, dimensions, ratios, etc. may differ from those of an actual device. However, these may be appropriately modified in design, taking into consideration the following description and known techniques.

[0010] In this invention, the polarization of light is measured as a method for detecting electric current. Electric current generates a magnetic field, and the generated magnetic field has the property of rotating the polarization plane of light. The electric current is detected by measuring this polarization. In this invention, the method for measuring polarization focuses on the change in light intensity before and after polarization.

[0011] (First embodiment) According to a first embodiment, there is provided a current sensor comprising a first optical waveguide, a second optical waveguide, and a polarization rotator optically connected to the first optical waveguide and the second optical waveguide.

[0012] The current sensor may have variations shown in FIGS. 2 and 3 depending on the arrangement of the optical waveguide, polarization rotator, and clad layer. The current sensor according to the embodiment will be described using side schematic diagrams of FIGS. 1, 2, and 3. FIG. 1 illustrates a temperature sensor in which a first optical waveguide (optical waveguide 4), a second optical waveguide (optical waveguide 5), and a polarization rotator are formed on a clad layer formed on a substrate. FIG. 2 illustrates a current sensor in which a polarization rotator is formed on a clad layer formed on a substrate, and the first optical waveguide and the second optical waveguide are embedded in the clad layer. FIG. 3 illustrates a current sensor in which a polarization rotator layer is formed on a substrate, and an optical waveguide is formed on the upper surface of the polarization rotator layer. While the current sensor illustrated in FIG. 1 will be used to describe the variations, the current sensors illustrated in FIGS. 2 and 3 can also be used. Any structure may be used as long as the first optical waveguide and polarization rotator, and the second optical waveguide and polarization rotator are optically connected.

[0013] The current sensor will be described in detail with reference to the drawings. In Fig. 1, a cladding layer 3, a first optical waveguide (optical waveguide 4), and a second optical waveguide (optical waveguide 5) are provided on the upper surface of a substrate 2. A polarization rotator 6 is provided on the cladding layer 3.

[0014] The substrate 2 supports the cladding layer, the optical waveguide, the polarization rotator, etc. The substrate 2 includes silicon. The substrate 2 is, for example, a silicon single crystal, and may be glass or a III-V group semiconductor.

[0015] The cladding layer 3 is deposited on the substrate 2 to a thickness of several μm. It is desirable that the cladding layer 3 does not absorb light and has a refractive index lower than that of the optical waveguides 4 and 5. The material of the cladding layer 3 is, for example, silicon oxide (SiO2). Due to the presence of the cladding layer 3, light travels through the optical waveguides 4 and 5 while undergoing total internal reflection.

[0016] The optical waveguides 4 and 5 propagate light incident from one end to the other end. The optical waveguides 4 and 5 are made of a material that does not absorb light and preferably has a higher refractive index than the cladding layer 3. The optical waveguides 4 and 5 are made of, for example, silicon, but may also be made of materials including SiN, SiON, SiOC, SiC, SiO2, and III-V semiconductors. The cladding layer 3, the optical waveguides 4, and 5 may be made of the same material as the cladding layer 3, as long as the refractive index of the optical waveguides 4 and 5 is different. The optical waveguide 5 may have a filter characteristic that allows only TE-polarized light to propagate as a polarization selection function. The optical waveguide 5 may also have a characteristic that allows only TM-polarized light (transverse magnetic wave) to propagate. Here, TM-polarized light refers to light polarized in a direction parallel to the substrate surface, and TE-polarized light refers to light polarized in a direction perpendicular to the substrate surface. Furthermore, even if the optical waveguide 5 does not have a filter characteristic, a polarizing filter can be installed at the end opposite to the end coupled to the polarization rotator 6. A polarizing filter is installed in the optical waveguide 4, the polarization rotator 6, and the optical waveguide 5.

[0017] One end of the polarization rotator 6 is optically coupled to the optical waveguide 4, and the other end is optically coupled to the optical waveguide 5. The polarization rotator 6 is preferably positioned so that the direction of light propagation is parallel to the magnetic field generated by the current to be measured, in order to enable accurate measurements by the current sensor 1. The polarization rotator 6 is, for example, YIG (yttrium iron gallium), but it may also be TGG (terbium gallium garnet), TSAG (terbium scandium aluminum garnet), or Bi:YIG or Ce:YIG, in which part of the yttrium in YIG is replaced with Bi or Ce.

[0018] The polarization rotator 6 is required to allow the light incident from the optical waveguide 4 to pass through the polarization rotator 6 and propagate smoothly to the optical waveguide 5. Therefore, it is desirable that the size of the polarization rotator 6 satisfies the single mode (single propagation form) condition for the wavelength of the light used, in other words, a size that does not cause the light to spread too much. The size of the polarization rotator 6 is changed depending on the refractive index of the material of the polarization rotator 6, the wavelength of the light used, the refractive index of surrounding components, etc.

[0019] Based on the above, the size of the polarization rotator 6 can be changed depending on the magnitude of the current to be measured. For example, if the surface area of ​​the top surface of the polarization rotator 6 is large, the distance affected by the magnetic field becomes longer, enabling highly sensitive current sensing. The polarization rotator 6 can be formed using various techniques, including attaching a separate crystal substrate, direct crystal growth, and forming a film by sputtering or the like followed by a recrystallization process.

[0020] A waveguide such as an optical fiber may be optically connected to the ends of the optical waveguides 4 and 5 opposite to the ends coupled to the polarization rotator 6. When an optical fiber is used, a single-mode fiber or a polarization-maintaining fiber may be used.

[0021] The operation of the current sensor 1 in FIG. 1 will be described. When TE-polarized light is input to the optical waveguide 4, it propagates to the polarization rotator 6. The polarization plane of the light input to the polarization rotator 6 rotates in proportion to the magnitude of the magnetic field generated within the polarization rotator 6 by the current to be measured. TM-polarized light, which is a portion of the light component with the rotated polarization plane, is absorbed or scattered and lost due to the filter characteristics of the optical waveguide 5. Only TE-polarized light is transmitted through the optical waveguide 5. In this way, the current sensor 1 according to this embodiment can compare or change the intensity of the light transmitted through the optical waveguide 4. The current can be detected by evaluating this change in light intensity.

[0022] The current sensor 1 according to the embodiment does not require components such as a coil, and the elements required for current detection are integrated on a substrate. This realizes a stable structure with no misalignment of the optical axis compared to a conventional structure assembled from optical components. Furthermore, it is possible to suppress reflections that occur on the surfaces of the optical components. This makes it possible to provide a small, highly reliable current sensor. Furthermore, it is possible to omit the process of aligning the optical axes of each component, thereby simplifying the manufacturing process.

[0023] (First Modification) FIG. 4( a) shows an example in which a first optical fiber (optical fiber 7) and a second optical fiber (optical fiber 8) are further added to the current sensor 1 according to the embodiment, and a first spot size converter (spot size converter 9) and a second spot size converter (spot size converter 10) are mounted on the substrate. FIG. 4( b) shows a top view of the current sensor 1 in FIG. 4( a), with each component perspectively shown so that the shapes of the optical waveguides 4 and 5 can be seen. As shown in FIG. 4( b), the ends of the optical waveguides 4 and 5 on the polarization rotator 6 side are tapered so that their widths narrow from the center of each of the optical waveguides 4 and 5 toward the end on the polarization rotator 6 side when viewed from the stacking direction of the current sensor 1. Hereinafter, the tapered end surfaces of the optical waveguides will be referred to as tapered surfaces.

[0024] The tapered surface gradually changes the cross-sectional area of ​​the optical waveguide as shown in Figure 4(b), allowing for conversion of the spot size and mode (propagation form) of light. This allows for smooth propagation with little optical loss due to reflection or scattering between the optical waveguide 4 and the polarization rotator 6, and between the polarization rotator 6 and the optical waveguide 5.

[0025] The optical fiber 7 is optically connected to a spot size converter 9 , and the optical fiber 8 is optically connected to a spot size converter 10 .

[0026] The spot size converters 9 and 10 may be made of the same material as the cladding layer 3, or may be made of a material with a high refractive index, such as polyimide or SiON film (silicon oxynitride film, silicon oxynitride film). If the spot size of the optical waveguide is smaller than the spot size of the optical fiber, sufficient optical coupling cannot be achieved, causing a decrease in transmission efficiency. Therefore, by installing a spot size converter between the optical fiber and the optical waveguide, transmission with less loss is possible. If the spot size of the optical waveguide is similar to or larger than the spot size of the optical fiber, a spot size converter may not be installed.

[0027] The operation of the current sensor 1 in Figure 2 will be described. Light passing through the optical fiber 7 is converted by the spot size converter 9 into a spot size that corresponds to the optical waveguide 4. The light refracted within the spot size converter 9 enters the optical waveguide 4 via the tapered surface and passes through the interior of the optical waveguide 4. The transmitted light then enters the polarization rotator 6 via the tapered surface, where its plane of polarization is rotated. The light emitted from the polarization rotator 6 passes through the interior of the optical waveguide 5 via the tapered surface of the optical waveguide 5. Due to the filter characteristics of the optical waveguide 5, only light with TE polarization enters the spot size converter 10 via the tapered surface and is propagated to the optical fiber 8. This configuration enables optical transmission with little loss.

[0028] (Second Modification) In FIG. 3, in the current sensor 1 according to the embodiment, a layer of a polarization rotator 6 is formed on a substrate 2, and an optical waveguide and a spot size converter are disposed above it.

[0029] The substrate 2 is a substrate on which the crystal layer of the polarization rotator 6 is formed. A material with a refractive index lower than that of the crystal of the polarization rotator 6 is desirable, such as a GGG (gadolinium gallium garnet) substrate or an SGGG (substituted-GGG) substrate.

[0030] The cladding layer 3 assists in light propagation to prevent light from diffusing. Specifically, when light emitted from the optical waveguide 4 enters the layer of the polarization rotator 6, it diffuses within the layer of the polarization rotator 6, preventing a decrease in the light intensity entering the optical waveguide 5. If the design is such that the light emitted from the optical waveguide 4 enters the layer of the polarization rotator 6 and then enters the optical waveguide 5 without a decrease in light intensity, the cladding layer 3 may be unnecessary.

[0031] A part of the cladding layer may be processed into, for example, a rib-type waveguide shape to prevent diffusion of light propagating through the layers of the polarization rotator 6. The waveguide shape is not limited to the rib type, and may be a high mesa type, a ridge type, a strip type, or the like.

[0032] The operation of the current sensor 1 in Figure 3 is the same as that in Figure 2, except that light that has passed through the optical waveguide 4 enters the layer of the polarization rotator 6 and then enters the optical waveguide 5 from the layer of the polarization rotator 6. Using a substrate on which such a crystal layer of the polarization rotator is formed has the advantage of eliminating the need for bonding the polarization rotator to the substrate or crystal growth as in the configuration shown in Figure 2.

[0033] (Third Modification) Fig. 4 shows a modified example of the current sensor according to the embodiment. In Fig. 4, a diffraction grating is added to the end of the optical waveguide on the side where the polarization rotator is optically connected, as a diffraction structure, and a reflective film is added to the upper surface of the polarization rotator, as a reflective structure. Fig. 4(a) is a side view of the current sensor. Fig. 4(b) is a top view of the current sensor, showing the appearance of the optical waveguide and the diffraction grating through the diffraction grating and the reflective film.

[0034] The first diffraction grating 12 and the second diffraction grating 13 have, for example, an uneven surface, and diverge from the end opposite the end optically connected to the optical waveguide 4 or the optical waveguide 5 toward the polarization rotator 6. This structure refracts light incident from the optical waveguide 4 or the polarization rotator 6. Specifically, the first diffraction grating 12 refracts light incident from the optical waveguide 4 toward the polarization rotator 6 or the reflective film 11. The second diffraction grating 13 refracts light in the polarization rotator 6 so that it enters the optical waveguide 5. This allows light to be incident at an acute angle to the surface of the polarization rotator 6, allowing the light to undergo repeated total reflections between the reflective film 11 and the inner surface of the polarization rotator 6. Therefore, since the light exits the optical waveguide 4 and passes through the polarization rotator 6 while repeatedly reflecting, the optical path until it enters the optical waveguide 5 can be secured longer than that of the current sensor shown in Figure 2. This allows even slight polarization due to a weak magnetic field to be detected. It is also possible to design the structure so that light emitted from first diffraction grating 12 is focused on second diffraction grating 13, thereby enabling low-noise sensing by reducing propagation loss. In this configuration, first diffraction grating 12 is designed to have polarization dependency, so there is no need to specify the polarization incident on optical fiber 7, and second diffraction grating 13 only needs to have the characteristic of receiving light with the same polarization as that transmitted by first diffraction grating 12. Although the explanation here is given using TE polarization, a configuration using only TM polarization is also acceptable.

[0035] The reflective film 11 serves to prevent light from the first diffraction grating 12 from diffusing outside the polarization rotator 6 and to allow the light to be incident on the second diffraction grating 13. The reflective film 11 is, for example, a single reflective film, but a multi-layer reflective film may also be used. If a sufficient difference in refractive index can be obtained to prevent light from diffusing from the polarization rotator 6 by changing the design of the first diffraction grating 12 or the second diffraction grating 13, the reflective film 11 may not be necessary.

[0036] The operation of the current sensor 1 in Figure 4 will be described. Light incident on the optical fiber 7 passes through the spot size converter 9 and enters the optical waveguide 4. The light propagating through the optical waveguide 4 is refracted by the first diffraction grating 12 and propagates to the polarization rotator 6. Some of the light is reflected by the reflective film 11 provided on the upper surface of the polarization rotator 6, reaches the second diffraction grating 13, where it is refracted, and then couples to the optical waveguide 5. This configuration increases the distance over which the light is affected by the magnetic field as it passes through the polarization rotator 6, enabling highly sensitive current sensing.

[0037] (Fourth Modification) FIG. 7 shows a modification of the current sensor 1 according to the embodiment, in which a reflecting mirror is provided at the end of the optical waveguide as a reflecting structure, and a reflecting film is provided on the upper surface of the polarization rotator.

[0038] The reflecting mirror 14 and the reflecting mirror 15 reflect the light incident from the optical waveguide 4 or the polarization rotator 6. The optical waveguide 4 and the reflecting mirror 14, the reflecting mirror 14 and the polarization rotator 6, the polarization rotator 6 and the reflecting mirror 15, and the reflecting mirror 15 and the optical waveguide 5 are optically connected. For example, the optical waveguide 4 is optically connected to the reflecting mirror 14, the polarization rotator 6, the reflecting mirror 15, and the optical waveguide 5 in this order. The reflecting mirror 14 and the reflecting mirror 15 may be arranged so that light propagates from the optical waveguide 4 to the polarization rotator 6 or from the polarization rotator 6 to the optical waveguide 5. In FIG. 7, for example, the ends of the optical waveguide 4 and the optical waveguide 5 are processed to install the reflecting mirror 14 and the reflecting mirror 15. This ensures a longer optical path from the optical waveguide 4 to the polarization rotator 6 to the optical waveguide 5 than the current sensor in FIG. 2. Furthermore, it is also possible to design the structure so that the light emitted from the reflecting mirror 14 is focused on the reflecting mirror 15, which enables low-noise sensing due to reduced propagation loss.

[0039] The operation of the current sensor 1 in Fig. 7 is the same as that in Fig. 4, except that the first diffraction grating 12 and the second diffraction grating 13 are replaced with reflecting mirrors 14 and 15. With this configuration, the distance over which light is affected by the magnetic field when passing through the polarization rotator 6 can be increased, enabling highly sensitive current sensing.

[0040] As a modification of the current sensor according to the embodiment, the optical waveguide before entering the polarization rotator may be branched, with only one of the optical waveguides passing through the polarization rotator. FIG. 8 is a top view of the current sensor 1 according to the embodiment. Light output from the spot size converter 9 is branched by the branching waveguide 16 into the optical waveguide 4 and the optical waveguide 17. The branching waveguide 16 is an element that splits the light intensity at a branching ratio of, for example, 1:1, and may be, for example, a Y-branching waveguide or an MMI (multimode interferometer) waveguide. The optical waveguide 4 passes through the polarization rotator 6 and reaches the spot size converter 10, while the optical waveguide 17 reaches the spot size converter 18 without passing through the polarization rotator 6. Let the optical output from the spot size converter 10 be output X and the optical output from the spot size converter 18 be output Y. Output X is affected by a magnetic field, but output Y is not, resulting in a difference between the outputs. Therefore, the current can be detected by evaluating the optical intensities of outputs X and Y. This configuration eliminates the need to measure the intensity of unpolarized control light beforehand, and allows for measurement of both polarized and control light simultaneously, enabling highly reliable measurements with minimal environmental influences such as temperature.

[0041] The arrangement of the optical fiber optically connected to the current sensor according to the embodiment can be on any surface of the current sensor, as long as the directions of the optical waveguides 4 and 5 within the current sensor can be arbitrarily bent and the optical waveguides 4 and 5 are optically connected to the polarization rotator. For example, they may be provided on opposing surfaces as shown in FIG. 9(a), or the optical waveguides 4 and 5 may be bent and provided on the same surface as shown in FIG. 9(b), or only the optical waveguide 4 may be bent and provided on an orthogonal surface as shown in FIG. 9(c). This allows any surface to be selected depending on the situation.

[0042] (Second embodiment) According to a second embodiment, there is provided a measurement device, which includes the current sensor according to the first embodiment.

[0043] 10 is a schematic diagram illustrating an example of a measurement device according to an embodiment. The measurement device 20 includes a driving device 21, a light source 22, a current sensor 1, a photodetector 23, and a receiving device 24. The driving device 21 and the light source 22, and the photodetector 23 and the receiving device 24 are electrically connected by, for example, electrical wiring. The light source 22 and the current sensor 1, and the photodetector 23 and the current sensor 1 are optically connected by optical fibers 7 and 8.

[0044] The driver 21 may include a driver circuit equipped with an APC (Automatic Power Control) function that keeps the output optical power constant. An example of the configuration of the driver circuit includes a semiconductor laser (LD) that generates light, a photodiode (PD) that monitors the power of the light output from the LD, a drive current supply circuit that supplies current to the LD, and a control circuit that adjusts the drive current to the LD based on feedback from the PD and controls the optical output to be constant.

[0045] The light source 22 can be changed appropriately depending on the materials of the substrate, optical waveguide, etc., and is, for example, a laser light source. The wavelength is preferably one that is less absorbed by the optical waveguide, for example, 1550 nm.

[0046] It is desirable that the current sensor 1 be positioned so that the propagation direction of light passing through it is parallel to the magnetic field generated by the current to be measured, which enables accurate sensing.

[0047] The optical receiver 23 converts the optical signal output from the current sensor 1 into an electrical signal, and includes, for example, a photodiode.

[0048] The receiving device 24 converts the electrical signal output from the photodetector 23 into, for example, a current value or a voltage value. Here, an example of conversion into a current value will be described.

[0049] Consider a wire through which a current i flows. The magnetic field H generated at a distance r from the wire is given by Ampere's law as follows:

number

number

[0050] When the input light is TE polarized light and a polarizing filter that transmits only TE polarized light is used, the input light intensity input to the current sensor 1 is I in The intensity of the received optical signal output from the current sensor 1 is expressed as I out , the efficiency with which light incident on the current sensor 1 is coupled to the polarization rotator 6 is defined as η in , the efficiency with which the light output from the polarizing filter is coupled to the light receiver 23 is defined as η out Then,

number

number

[0051] Data on the relationship between the current to be measured and polarization can be acquired in advance, and the current value can be measured by evaluating the degree of polarization from the light intensity obtained by the current sensor 1.

[0052] The measuring device 20 can measure the current flowing in an electric wire, wiring, or cable without contacting it, so it is desirable that the current to be measured flows through, for example, an electric wire, wiring, or cable.

[0053] The operation of the measuring device 20 will now be explained. Before measuring the current, the intensity of unpolarized light is measured in advance. This is called the reference light. Under the control of the driving device 21, the light source 22 emits light, which enters the current sensor 1 via the optical fiber 7. The light affected by the magnetic field due to the current to be measured is output from the current sensor 1 and enters the photodetector 23 via the optical fiber 8. The light input by the photodetector 23 is converted into an electrical signal, and the converted electrical signal is input to the receiving device 24. The amount of rotation of the light is evaluated from the intensity ratio between the reference light and the input light, and converted into a current value. This makes it possible to measure the current to be measured.

[0054] Although not shown, a light receiver may be further provided and positioned so that the light emitted from the light source 22 is input thereto. In this configuration, the current can be measured without measuring the intensity of the reference light in advance.

[0055] The measuring device according to the embodiment includes the current sensor according to the first embodiment and does not require a large signal processing unit, so that a small and highly reliable measuring device can be provided.

[0056] According to one or more of the embodiments and examples described above, a current sensor is provided. The current sensor according to the embodiment can provide a small-sized, highly reliable current sensor.

[0057] (Other embodiments) Although the present specification has described a method for measuring polarization that focuses on the change in light intensity before and after polarization, other methods of polarization measurement, such as using a polarimeter to measure the polarization itself and detect the current, are also possible. In this case, the polarimeter is installed instead of a component with a polarization selection function, such as a filter.

[0058] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0059] The following describes the invention in terms of embodiments.

[0060] <1> a first optical waveguide and a second optical waveguide; a polarization rotator optically connected to the first optical waveguide and the second optical waveguide; A current sensor comprising:

[0061] <2> When the current sensor is viewed in a stacking direction, the polarization rotator is located between the first optical waveguide and the second optical waveguide. <1> The current sensor according to claim 1.

[0062] <3> the first optical waveguide and the second optical waveguide are stacked on the polarization rotator; <1> or <2> The current sensor according to claim 1.

[0063] <4> the second optical waveguide has a polarization selection function; <1> from <3> 10. The current sensor according to claim 9, wherein:

[0064] <5> a first spot size converter provided at an end opposite to an end where the first optical waveguide and the polarization rotator are optically connected; a second spot size converter provided at an end opposite to an end where the second optical waveguide and the polarization rotator are optically connected; Further provided with <1> from <4> 10. The current sensor according to claim 9, wherein:

[0065] <6> the first optical waveguide and / or the second optical waveguide have a tapered structure; <1> from <5> 10. The current sensor according to claim 9, wherein:

[0066] <7> The polarization rotator has a reflective structure on at least a portion thereof. <1> from <6> 10. The current sensor according to claim 9, wherein:

[0067] <8> a diffractive structure is provided at an end where the first optical waveguide and / or the second optical waveguide and the polarization rotator are optically connected; <1> from <7> 10. The current sensor according to claim 9, wherein:

[0068] <9> a reflecting structure is provided at an end where the first optical waveguide and / or the second optical waveguide and the polarization rotator are optically connected; <1> from <8> 10. The current sensor according to claim 9, wherein:

[0069] <10> The first optical waveguide branches. <1> from <9> 10. The current sensor according to claim 9, wherein:

[0070] <11> A light source and The light output from the light source is input after propagating through a first optical fiber. <1> from <10> a current sensor according to any one of the preceding claims; a photodetector that receives the light output from the current sensor after propagating through a second optical fiber and converts the light into an electrical signal; a receiving device that receives the electrical signal and converts it into a current value; A measuring device comprising: [Explanation of symbols]

[0071] 1 Current Sensor 2 boards 3 Cladding layer 4, 5, 17 Optical waveguide 6 Polarization Rotator 7, 8 Optical Fiber 9, 10, 18 Spot Size Converter 11 Reflective film 12 First diffraction grating 13 Second diffraction grating 14, 15 Reflective mirror 16 Branching Waveguide 20 Measuring Equipment 21 Drive unit 22 Light source 23 Receiver 24 Receiving device

Claims

1. a first optical waveguide and a second optical waveguide; a polarization rotator optically connected to the first optical waveguide and the second optical waveguide; A current sensor comprising:

2. The current sensor according to claim 1 , wherein the polarization rotator is present between the first optical waveguide and the second optical waveguide when the current sensor is viewed in the stacking direction.

3. The current sensor according to claim 1 , wherein the first optical waveguide and the second optical waveguide are stacked on top of the polarization rotator.

4. The current sensor according to claim 1 , wherein the second optical waveguide has a polarization selection function.

5. a first spot size converter provided at an end opposite to an end where the first optical waveguide and the polarization rotator are optically connected; a second spot size converter provided at an end opposite to an end where the second optical waveguide and the polarization rotator are optically connected; Further provided with The current sensor according to claim 1 .

6. The current sensor according to claim 1 , wherein the first optical waveguide and / or the second optical waveguide have a tapered structure.

7. The current sensor of claim 1 , wherein at least a portion of the polarization rotator comprises a reflective structure.

8. 2. The current sensor according to claim 1, further comprising a diffractive structure at an end where the first optical waveguide and / or the second optical waveguide and the polarization rotator are optically connected.

9. 2. The current sensor according to claim 1, further comprising a reflecting structure at an end where the first optical waveguide and / or the second optical waveguide and the polarization rotator are optically connected.

10. The current sensor of claim 1 , wherein the first optical waveguide is bifurcated.

11. A light source and The current sensor according to claim 1 , wherein the light output from the light source is input after propagating through a first optical fiber; a photodetector that receives the light output from the current sensor after propagating through the second optical fiber and converts the light into an electrical signal; a receiving device that receives the electrical signal and converts it into a current value; A measuring device comprising:

Images