JP2013032968A - Optical fiber type voltage sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber type voltage sensor capable of using one light source for a plurality of kinds of uses.SOLUTION: An optical fiber type voltage sensor 10 includes an optical fiber 12 having a measuring optical fiber part 12b, and light emitted from a light source 11 is branched into the optical fiber 12 and the measuring optical fiber part 12b. The measuring optical fiber part 12b is provided with a Pockels effect member 21 of which a refractive index changes according to a voltage of a circuit 15 to be measured and a first FBG 22. The optical fiber 12 is provided with a second FBG 23 formed to have the same Bragg wavelength λ as the first FBG 22. Light of wavelength λ reflected by the second FBG 23 and light of wavelength λ of which propagation velocity is changed by the Pockels effect member 21 and which is reflected by the first FBG 22 out of the light emitted from light source 11 are combined, and interference phenomenon occurs.

Description

  The present invention relates to a configuration of an optical fiber voltage sensor that measures a voltage using an optical fiber.

  In recent years, an optical fiber type voltage sensor using an electro-optic effect called Pockels effect or Kerr effect is used as a sensor for measuring voltage. The Pockels effect is a phenomenon in which when a voltage is applied to a substance and an electric field is applied, the refractive index of the substance changes in proportion to the strength of the electric field. On the other hand, in the Kerr effect, the refractive index of a substance changes in proportion to the square of the electric field strength.

  For example, Patent Document 1 discloses an optical fiber voltage sensor that measures a voltage to be measured using a Pockels material having a Pockels effect. According to this, the input and output optical fibers are connected to one end side of the rod lens via the rutile plate which is a birefringent material. Further, a Pockels material, a 1/8 wavelength plate, and a reflector are provided on the other end side of the rod lens, and a voltage to be measured is applied to the Pockels material. The light incident on the input optical fiber is converted into linearly polarized light when passing through the rutile plate, and passes through the Pockels material and the 1/8 wavelength plate. The light is then reflected off the reflector, passes again through the 1/8 wavelength plate and Pockels material, and reaches the rutile plate.

  At this time, since the refractive index of the Pockels material changes according to the voltage to be measured, a phase change corresponding to the voltage to be measured occurs in the light passing through the Pockels material. In addition, when a phase difference of ¼ wavelength is given when passing through the ８ wavelength plate twice, the light reflected by the reflection plate and reaching the rutile plate is converted into elliptically polarized light. As described above, the elliptically polarized light in a state in which the phase change corresponding to the voltage to be measured is separated into ordinary light and extraordinary light when passing through the rutile plate again, and the extraordinary light is guided to the output optical fiber. The intensity change of the abnormal light corresponds to the phase change corresponding to the voltage to be measured. That is, the voltage to be measured is obtained by measuring the intensity of abnormal light propagating through the output optical fiber.

Japanese Patent Laid-Open No. 62-198769

  Usually, an optical fiber can transmit light of a plurality of wavelengths simultaneously. In addition, the optical fiber can be applied as a sensor for measuring physical quantities other than voltage, such as strain, vibration, or temperature of an object to be measured. Due to these characteristics, in recent years, it has attracted attention to construct a sensor network in which various sensors, vehicle control devices, and the like are connected via an optical fiber in a vehicle such as an electric vehicle (EV) or a hybrid vehicle (HV). ing. If light of multiple wavelengths is incident on an optical fiber and each wavelength is distributed to voltage measurements at multiple locations, physical quantity measurements other than voltage, or information transmission other than measured physical quantities, a single optical fiber is installed in the vehicle A sensor network can be constructed just by doing.

  However, in the optical fiber type voltage sensor described in Patent Document 1, a semiconductor laser having a narrow wavelength band of emitted light is used as a light source, and only one voltage applied to one Pockels material is measured by one light source. It has a configuration. Therefore, this optical fiber type voltage sensor does not have a means for selecting the wavelength of light used for voltage measurement, and even if a light source that emits light of multiple wavelengths is used, each wavelength is allocated to different applications. Is impossible. That is, in the optical fiber type voltage sensor described in Patent Document 1, one light source cannot be used for a plurality of types of applications, and when applying to a sensor network as described above, a plurality of units according to the number of uses. However, it has a problem of requiring a light source.

  The present invention has been made to solve such problems, and an object of the present invention is to provide an optical fiber voltage sensor that realizes use of one light source for a plurality of types of applications.

  An optical fiber type voltage sensor according to the present invention is a sensor for measuring a voltage of a circuit under test, and includes an optical fiber and an electro-optic effect member whose refractive index changes according to the voltage. A measurement optical fiber portion that is branched from the fiber and connected to the electro-optic effect member, and the measurement optical fiber portion has a first downstream side of the electro-optic effect member in a direction in which incident light propagates. An FBG is provided.

  First, FBG (Fiber Bragg Grating) is a diffraction grating in which the refractive index of the core of the optical fiber is changed by a predetermined length period (grating period) along the axial direction. On the other hand, it has a characteristic of reflecting light having a predetermined wavelength (Bragg wavelength) corresponding to the grating period and transmitting the remaining light.

  When light is incident on the optical fiber, the incident light is also branched to the measurement optical fiber part side and propagates through the optical fiber and the measurement optical fiber part, respectively. The light propagating in the measurement optical fiber part is guided to the electro-optic effect member to which the voltage of the circuit to be measured is applied, propagates through the electro-optic effect member, and enters the first FBG. Since the refractive index of the electro-optic effect member changes according to the applied voltage, the propagation speed of light inside thereof also changes according to the voltage. Of the light whose propagation speed has changed in this way, the light with the Bragg wavelength is reflected by the first FBG, and travels back through the measurement optical fiber portion and is returned into the optical fiber.

  The reflected light from the first FBG returned into the optical fiber is combined with light of the same wavelength propagating through the optical fiber, and an optical interference phenomenon occurs. Here, since the propagation speed of the reflected light from the first FBG changes according to the voltage of the circuit under measurement when passing through the electro-optic effect member, the intensity of the light combined and interfered in the optical fiber Also depends on the voltage. That is, by measuring the intensity of the light propagating through the optical fiber and the light combined with the reflected light from the first FBG, that is, the intensity of the Bragg wavelength light reflected by the first FBG, A voltage is required.

  In addition, as described above, the FBG has a characteristic of reflecting light with a Bragg wavelength and transmitting light with the remaining wavelengths. In other words, if a device that emits broadband light having a bandwidth wider than the bandwidth of the reflection spectrum of the first FBG is used as a light source for entering light into the optical fiber, only Bragg wavelength light is used for voltage measurement, and the rest Can be used for other purposes. Therefore, in the optical fiber type voltage sensor, one light source can be used for a plurality of types of applications.

  The optical fiber may be provided with a second FBG that reflects light having the same wavelength as the first FBG on the upstream side of the electro-optic effect member in the direction in which the incident light propagates. In this case, the reflected light from the first FBG and the reflected light from the second FBG are combined in the optical fiber and travel backward in the optical fiber. That is, the voltage of the circuit under test is obtained by measuring the intensity of this light that goes backward.

  According to the present invention, in an optical fiber voltage sensor, light emitted from one light source can be used for a plurality of types of applications.

It is the schematic which shows the structure of the optical fiber type voltage sensor which concerns on Embodiment 1 of this invention. 2 is a schematic diagram illustrating a configuration of an FBG in the optical fiber type voltage sensor according to Embodiment 1. FIG. It is the schematic which shows the structure of the optical fiber type voltage sensor which concerns on Embodiment 2 of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 schematically shows a configuration of an optical fiber type voltage sensor 10 according to the first embodiment.
The optical fiber type voltage sensor 10 includes an optical fiber 12 having a light source 11 connected to one end. The optical fiber 12 has a measuring optical fiber portion 12b branched from the branching portion 12a. The light emitted from the light source 11 propagates in the optical fiber 12 in the direction indicated by the arrow A, and is branched by the branching portion 12a as indicated by the arrow B and propagates in the measurement optical fiber portion 12b.

  A circulator 13 is provided between the light source 11 and the branching portion 12a, and a measuring machine 14 is connected to the circulator 13 via a branching optical fiber 12c. The circulator 13 allows the light incident on the optical fiber 12 from the light source 11 to pass in the direction indicated by the arrow A, and reflects the reflected light reflected from the first FBG 22 and the second FBG 23 described later toward the light source 11. As shown by an arrow C, it is an optical component that leads to the measuring instrument 14. In addition, as the measuring device 14, for example, a device that measures the amount of photons (photon amount) proportional to the intensity of light using a photodiode or the like is used.

  A Pockels effect member 21 as an electro-optic effect member whose refractive index changes according to the applied voltage of the circuit 15 to be measured is provided in the middle of the measurement optical fiber portion 12b, and the measurement optical fiber portion 12b. Light propagating through the inside can pass through the Pockels effect member 21. The Pockels effect member 21 is a member made of an isotropic crystal having piezoelectricity, and a pair of electrodes 21a and 21b for applying a voltage of the circuit 15 to be measured are provided on both sides thereof. Further, on the downstream side of the Pockels effect member 21 in the light propagation direction indicated by the arrow B, a first FBG 22 that reflects light of a predetermined wavelength called Bragg wavelength among the light that has passed through the Pockels effect member 21 is: It is connected to the Pockels effect member 21. The measurement optical fiber portion 12b in the first embodiment is cut downstream of the first FBG 22 in the light propagation direction indicated by the arrow B.

  On the other hand, in the optical fiber 12, the light having the Bragg wavelength is reflected on the downstream side of the branching portion 12a in the light propagation direction indicated by the arrow A out of the light propagating in the optical fiber 12 through the branching portion 12a. A second FBG 23 is formed. As will be described below, the Bragg wavelength of the FBG is a value determined according to a length period called a grating period, and the first FBG 22 and the second FBG 23 are provided so that the Bragg wavelengths are the same wavelength. ing.

  Next, the configuration of the measurement optical fiber portion 12b and the first FBG 22 will be described with reference to FIG. Since these configurations and the configurations of the optical fiber 12 and the second FBG 23 are common, the components on the optical fiber 12 side are indicated by parenthesized symbols in FIG. The measurement optical fiber portion 12b includes a core 24a through which incident light L1 which is light branched by the branch portion 12a (see FIG. 1) propagates, and a clad 24b that covers the outer periphery of the core 24a. The first FBG 22 is a diffraction grating in which the refractive index of the core 24a is changed by a predetermined length period (grating period) Λ along the axial direction. For example, the first FBG 22 is formed by irradiating the core 24a with ultraviolet rays or the like. . As described above, the Bragg wavelength λ of the first FBG 22 is a value determined according to the grating period Λ, and the first FBG 22 reflects light having the Bragg wavelength λ as reflected light L2 with respect to the incident light L1. The remaining wavelengths of light are transmitted as transmitted light L3.

  Returning to FIG. 1, the light source 11 is a device that emits broadband light including light of a plurality of wavelengths and including the reflection spectra of the first FBG 22 and the second FBG 23 in the bandwidth, such as an LED that emits white light. Is used as the light source 11. Note that the white light emitted from the light source 11 refers to light having a spectrum in which ultraviolet light (invisible), light having a wavelength corresponding to purple to red (visible), and infrared light (invisible) are continuously connected. That is, the light that is incident from the light source 11 and propagates through the optical fiber 12 and the measurement optical fiber portion 12b is not limited to colorless light, but includes light of various colors according to the spectrum bandwidth. obtain.

Next, a method for measuring the voltage of the circuit under test 15 using the optical fiber type voltage sensor 10 according to the first embodiment of the present invention will be described.
As shown in FIG. 1, the voltage of the circuit under test 15 is first applied between the electrodes 21a and 21b provided on both sides of the Pockels effect member 21, and then the light emitted from the light source 11 The light enters the fiber 12. When the voltage of the circuit under test 15 is applied between the electrode 21a and the electrode 21b and an electric field is applied to the Pockels effect member 21, the refractive index of the Pockels effect member 21 changes according to the voltage. The light incident on the optical fiber 12 passes through the circulator 13 and then is branched at the branching portion 12a and propagates in the optical fiber 12 (see arrow A) and in the measurement optical fiber portion 12b (see arrow B). .

  The light branched to the optical fiber 12 side in the branch part 12a is incident on the second FBG 23. The second FBG 23 reflects the light having the Bragg wavelength λ and transmits the light having the remaining wavelength, and the reflected light having the Bragg wavelength λ travels backward in the optical fiber 12 as indicated by an arrow D2. On the other hand, the light branched to the measurement optical fiber part 12 b side in the branch part 12 a passes through the Pockels effect member 21 and enters the first FBG 22. Here, since the refractive index of the Pockels effect member 21 changes in accordance with the voltage of the circuit 15 to be measured applied between the electrodes 21a and 21b, the propagation speed of light in the Pockels effect member 21 is also high. Varies with voltage. Of the light having passed through the Pockels effect member 21 with the propagation speed changed in this way, the light having the Bragg wavelength λ is reflected by the first FBG 22 and travels backward in the measurement optical fiber portion 12b as indicated by an arrow D1.

  The reflected light that is reflected by the first FBG 22 and travels backward in the measurement optical fiber portion 12b returns to the optical fiber 12 through the branching portion 12a and travels backward. Further, in the optical fiber 12, the reflected light reflected by the second FBG 23 is reversed. When these retrograde lights are combined at the branching portion 12a, a light interference phenomenon occurs. Here, since the propagation speed of the reflected light from the first FBG 22 changes according to the voltage of the circuit under test 15 when passing through the Pockels effect member 21, the light that is combined and interfered in the optical fiber 12. The intensity also depends on this voltage. The light that interferes in this manner travels backward in the optical fiber 12 to reach the circulator 13 and is guided to the measuring instrument 14 via the branching optical fiber 12c. The measuring device 14 measures the photon amount of the received light, that is, the photon amount of the light having the Bragg wavelength λ, and the voltage of the circuit under measurement 15 is obtained based on the measured photon amount.

  In the broadband light emitted from the light source 11 and propagating on the optical fiber 12 side, light having a wavelength other than the Bragg wavelength λ is transmitted through the second FBG 23 and propagates downstream thereof. As described above, since the wavelength used for measuring the voltage to be measured is only the light having the Bragg wavelength λ, the light transmitted through the second FBG 23 is used for purposes other than the voltage measurement of the circuit under measurement 15. It is possible. Examples of such applications include measurement of voltage at another part, measurement of physical quantities other than voltage, such as strain, vibration, temperature, etc. of an object to be measured, or transmission of information other than measured physical quantities.

  As described above, the propagation speed can be changed by the Pockels effect member 21 and the light with the Bragg wavelength λ reflected by the first FBG 22 and the light with the Bragg wavelength λ propagated through the optical fiber 12 and reflected by the second FBG 23 Since the interference phenomenon is generated by synthesizing and the interfering light is received by the measuring instrument 14, the intensity of the light received by the measuring instrument 14, specifically, the photon amount proportional to the intensity is measured. The voltage of the measurement circuit 15 can be measured. In addition, among the light propagating through the optical fiber 12, light having a wavelength other than the Bragg wavelength λ is transmitted to the second FBG 23, so that the transmitted light can be used for other purposes. Therefore, in the optical fiber type voltage sensor 10, one light source 11 can be used for a plurality of types of applications. Note that the multiple types of applications include, for example, a case where it is used for a voltage sensor for measuring voltages at a plurality of locations and a case where it is used for a plurality of types of sensors such as a current sensor and a voltage sensor.

Embodiment 2. FIG.
Next, an optical fiber type voltage sensor according to Embodiment 2 of the present invention will be described. In the optical fiber type voltage sensor according to the second embodiment, the measuring instrument 14 in the first embodiment is connected to the light source 11 side in the optical fiber 12, whereas the measuring instrument 14 is opposite to the light source 11. It connects to the edge part which becomes. In the embodiment described below, the same reference numerals as those shown in FIGS. 1 and 2 are the same or similar components, and thus detailed description thereof is omitted.

  As shown in FIG. 3, the light source 11 is connected to one end of the optical fiber 12 in the optical fiber type voltage sensor 30, and the measuring instrument 14 is connected to the other end. A circulator 31 is provided in the middle of the optical fiber 12, and the measurement optical fiber portion 12 b is connected to the circulator 31. The measurement optical fiber portion 12b is provided with a Pockels effect member 21 and a first FBG 22 as in the first embodiment. On the other hand, the optical fiber 12 is not provided with the second FBG 23 in the first embodiment, and light propagating on the optical fiber 12 side (see arrow A) is guided to the measuring instrument 14.

  The circulator 31 allows light incident on the optical fiber 12 from the light source 11 to pass in the direction indicated by the arrow A and branches to the measurement optical fiber portion 12b as indicated by the arrow B. Further, the circulator 31 allows the light reflected by the first FBG 22 (see arrow D1) to pass in a direction where the light propagates in the direction indicated by the arrow E, that is, the direction indicated by the arrow A. Other configurations are the same as those in the first embodiment.

  In the optical fiber type voltage sensor 30 configured as described above, light incident on the optical fiber 12 from the light source 11 is branched by the circulator 31 and propagates in the optical fiber 12 and the measurement optical fiber portion 12b. The light propagating through the measurement optical fiber portion 12 b is incident on the first FBG 22 after being changed to a propagation speed corresponding to the voltage of the circuit under test 15 when passing through the Pockels effect member 21. The first FBG 22 reflects light having the Bragg wavelength λ of the incident light, and when this reflected light is returned into the optical fiber 12 by the circulator 31, the light having the wavelength λ is reflected between the light beams having the wavelength λ. As a result of the synthesis, an optical interference phenomenon occurs. The interfered light propagates in the optical fiber 12 in the direction indicated by the arrow A and is guided to the measuring instrument 14, whereby the voltage of the circuit under test 15 is obtained.

  Thus, even if the optical fiber type voltage sensor 30 is configured such that the light source 11 is connected to one end side of the optical fiber 12 and the measuring device 14 is connected to the other end side, as in the first embodiment, The voltage of the circuit under test 15 can be obtained using the light interference phenomenon. Further, since the light used for the voltage measurement is only the light having the Bragg wavelength λ of the first FBG 22, light having a wavelength other than the wavelength λ is used for other purposes as in the first embodiment. be able to. Further, in the optical fiber type voltage sensor 30, unlike the second FBG 23 in the first embodiment, it is not necessary to form the FBG on the optical fiber 12, so that the voltage of the circuit under test 15 can be measured at low cost. It becomes.

  Although the electro-optic effect member in the first and second embodiments is configured as the Pockels effect member 21 having the Pockels effect, it is not limited to utilizing the Pockels effect. Even if a member having a Kerr effect in which the refractive index of a substance changes in proportion to the square of the intensity of the electric field is used as the electro-optic effect member, the same effect as in the first and second embodiments can be obtained.

  DESCRIPTION OF SYMBOLS 10, 30 Optical fiber type voltage sensor, 12 Optical fiber, 12b Measurement optical fiber part, 15 Circuit to be measured, 21 Pockels effect member (electro-optic effect member), 22 1st FBG, 23 2nd FBG.

Claims (2)

An optical fiber type voltage sensor for measuring the voltage of a circuit under test,
Optical fiber,
An electro-optic effect member whose refractive index changes according to voltage,
The optical fiber includes a measurement optical fiber portion that is branched from the optical fiber and connected to the electro-optic effect member.
The optical fiber type voltage sensor, wherein the measurement optical fiber portion is provided with a first FBG on the downstream side of the electro-optic effect member in a direction in which incident light propagates.   2. The optical fiber according to claim 1, wherein the optical fiber is provided with a second FBG that reflects light having the same wavelength as the first FBG on the upstream side of the electro-optic effect member in a direction in which the incident light propagates. Type voltage sensor.

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