Optical voltage probe

Abstract

To provide an optical voltage probe capable of reducing an influence due to an ambient variable magnetic field and measuring the voltage signal at a measurement point more accurately.SOLUTION: An optical voltage probe includes an optical modulator that modulates the intensity of incident light and outputs the light depending on the voltage between first and second electrode pads, a first contact terminal and a second contact terminal that can be in contact with a measurement point, a first electric line connecting the first contact terminal and the first electrode pad, and a second electric line connecting the second contact terminal and the second electrode pad. The first and second contact terminals or the first and second electric lines intersect with each other in a non-contact state at least once. In a case where the magnetic field penetrating between the first and second contact terminals or between the first and second electric lines varies, the inductive electromotive force is generated whose directions are opposite between the first and second contact terminals or the first and second electric lines in a part before and after the intersection part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical voltage probe that applies a voltage signal obtained from a contact terminal to an optical modulator to convert it into an optically modulated signal, and outputs the optically modulated signal through an optical fiber. [Background technology]

[0002] In recent years, various control devices using high-speed CPUs and other devices have been developed, and in order to prevent malfunctions, various tests are being conducted to apply electrical loads to electrical circuits and electrical components, such as ESD (Electrostatic Discharge) tests, in which electrical circuits and components are charged and then discharged to ground, and noise immunity tests.The criteria for these tests are solely to verify malfunction or destruction, and they are expected to accurately measure input / output signals of electrical components installed on the electrical circuit board under test and electrical signals transmitted through wiring.

[0003] A common method for measuring electrical signals from electrical components or wiring is to use an electric probe with contact terminals to conduct the electrical signal at the point of measurement to a measuring instrument such as an oscilloscope, and then measure the transmitted voltage waveform. However, when the ground level of the point of measurement differs from that of the measuring instrument, or when measuring a voltage signal between two ungrounded points, accurate measurement of the voltage waveform can be difficult due to signal interference from the ground and the capacitance of the electric probe. The effects of ground and capacitance are particularly significant in the high-frequency range. Furthermore, many integrated circuits, such as ICs and LSIs, have input and output impedances that are not 50 Ω. Therefore, when measuring noise voltages using an electric probe with a low input impedance, current flows through the electric probe, reducing the actual electrical signal and noise voltage.

[0004] To solve this problem, a measuring instrument has been developed that uses an optical voltage probe, which converts the voltage signal into an optical signal and transmits that optical signal to the measuring instrument via optical fiber. With this method, the probe's capacitance is very small and its input impedance is very high, so the original electrical signal and noise voltage are converted into an optical signal without degradation, and the signal is then transmitted as an optical signal through optical fiber, completely isolating the point under test from the measuring instrument electrically. The optical voltage probe can measure even high-frequency components and can prevent the effects of grounding and the introduction of electrical signal noise along the way.

[0005] Examples of such conventional measuring instruments are described in Patent Documents 1, 2 and 3. Patent Document 1 describes an optical voltage probe using a bulk-type optical modulator. The probe applies a voltage signal to a contact terminal of a crystal with an electro-optic effect to change the polarization state of incident light, which is then passed through an analyzer to become intensity-modulated light and guided to an O / E converter via an optical fiber. Patent Document 2 describes an optical voltage probe using a waveguide-type optical modulator. An optical intensity modulated signal is obtained by applying a voltage signal from a contact terminal between two modulation electrodes of an interference-type optical modulator formed on a lithium niobate crystal substrate. The optical voltage probe is connected to a device equipped with a light source and an O / E converter via an optical fiber. Patent Document 3 shows a configuration in which the package of an optical voltage probe is covered with a conductive material such as metal or a radio wave absorbing material such as ferrite. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Unexamined Patent Publication No. 63-196863 [Patent Document 2] Japanese Patent Application Publication No. 8-35998 [Patent Document 3] Patent Publication No. 2021-165666 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, conventional optical voltage probes can eliminate the effects of the ground and prevent electrical signal noise from being mixed in from the wiring to the measuring instrument. Furthermore, the optical voltage probe of Patent Document 3 covers the package with metal or an electromagnetic wave absorbing material, thereby eliminating the effects of electromagnetic noise that propagates through the space around the optical voltage probe and uses the wiring from the contact terminal to the modulation electrode as an antenna to directly reach the modulation electrode.

[0008] However, in ESD testing, a voltage of several kV is generated on the charged plate carrying the electric circuit board. When this radio wave is generated and then grounded to discharge, a current of several amperes can flow. With conventional optical voltage probes, even when a cover is provided to block the above radio waves, the noise generated during the discharge is directly picked up by the optical voltage probe, making it impossible to accurately measure input / output signals of electrical components or electrical signals transmitted through wiring. The inventors' experiments have revealed that this is because the current flowing during the discharge generates a large fluctuating magnetic field in the surrounding area, which in turn generates an induced electromotive force in the wiring from the optical voltage probe's contact terminal to the modulation electrode. Furthermore, because this magnetic field is so large, it cannot be completely eliminated by covering the optical voltage probe with a simple magnetic material.

[0009] SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide an optical voltage probe that can reduce the influence of the surrounding fluctuating magnetic field and can more accurately measure the voltage signal at the point to be measured. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, in a first aspect, an optical voltage probe according to the present invention is an optical voltage probe for measuring a voltage signal at a point to be measured, comprising: an optical modulator having a modulation electrode having a first electrode pad and a second electrode pad, which intensity-modulates incident light depending on the voltage between the first and second electrode pads and outputs the modulated light; an input optical fiber and an output optical fiber connected to the optical modulator; a first contact terminal and a second contact terminal that can come into contact with the point to be measured; a first electric line connecting the first contact terminal and the first electrode pad; a second electric line connecting the second contact terminal and the second electrode pad; and an optical modulator, at least a portion of the first and second electric lines, and the input optical fiber and the output optical fiber. and a package accommodating a part of a power supply, the power supply being configured to convert a voltage signal induced between the first and second electrode pads via the first and second contact terminals into an optical intensity modulated signal by the optical modulator and output the signal from the output optical fiber, the first contact terminal and the second contact terminal, or the first electric line and the second electric line, having an intersection where they cross each other in a non-contact state, and when a magnetic field penetrating between the first and second contact terminals or the first and second electric lines fluctuates, induced electromotive forces in opposite directions are generated between the first and second contact terminals or between the first and second electric lines by the fluctuating magnetic field in portions before and after the intersection.

[0011] In conventional optical voltage probes, as described above, a large fluctuating magnetic field is generated in the vicinity due to a current flowing during discharge, and if this magnetic field penetrates between the first and second contact terminals or the first and second electrical lines, the fluctuating magnetic field generates an induced electromotive force between the first and second contact terminals or the first and second electrical lines. This induced electromotive force is superimposed on the voltage signal between the first and second contact terminals and applied between the first and second electrode pads. This prevents accurate measurement of the voltage signal at the point of measurement. In contrast, in the optical voltage probe of the present invention, as described above, by crossing the first and second contact terminals or the first and second electrical lines without contacting each other, opposite induced electromotive forces are generated between the first and second contact terminals or the first and second electrical lines before and after the crossing. This induced electromotive forces cancel each other out, thereby reducing the influence of the fluctuating magnetic field. This reduces the influence of the surrounding fluctuating magnetic field, making it possible to measure the voltage signal at the point to be measured more accurately.

[0012] The optical voltage probe of the present invention can be effectively used not only in the ESD test described above, but also in various measurement environments where a fluctuating magnetic field is present, such as measurements near power supplies or power plants that handle large, fluctuating currents, which are likely to generate large fluctuating magnetic fields, and measurements of electrical components in a measured electrical circuit that has a circuit that generates a fluctuating magnetic field in part.

[0013] In an optical voltage probe, measurements are made by bringing a contact terminal into contact with a measurement point on a circuit board or the like. The contact terminal may be provided integrally with the optical voltage probe, or may be detachable from the package so that the contact terminal can be selected according to the purpose.

[0014] In a second aspect, the optical voltage probe of the present invention is the optical voltage probe of the first aspect, wherein the varying magnetic field is a magnetic field generated by an electrical load in a test environment in which an electrical load is applied to an electrical circuit or electrical component, and the point under test is a point under test within the electrical circuit or electrical component. The invention of this aspect is an optical voltage probe for use in a test environment in which an electrical load is applied, the effectiveness of which has been confirmed by the inventor.

[0015] In a third aspect, the optical voltage probe according to the present invention is the optical voltage probe according to the first aspect, characterized in that the first contact terminal and the second contact terminal, or the first electric line and the second electric line, have a plurality of intersections. The induced electromotive force is proportional to the magnitude of the magnetic flux in the area surrounded by the electric lines, such as the first and second contact terminals or the first and second electric lines, and is proportional to the area of ​​the area when the magnetic flux density is constant. Therefore, when reducing the influence of a fluctuating magnetic field by canceling out the induced electromotive force in the areas before and after the intersection, it is necessary to make the areas surrounded by the electric lines before and after the intersection as equal as possible. In this case, it is easier to cancel out the induced electromotive force by providing multiple intersections to reduce the areas surrounded by the electric lines before and after the intersection and thus canceling out the induced electromotive force over multiple areas, rather than by providing only one intersection and making the areas surrounded by the electric lines equal before and after the intersection.

[0016] In a fourth aspect, the optical voltage probe according to the present invention is the optical voltage probe of the first aspect, characterized in that the first electric line and the second electric line are twisted together in a non-contact state. By twisting the first electric line and the second electric line together in a non-contact state in this way, the area of ​​the region surrounded by the first electric line and the second electric line and through which the varying magnetic field passes can be reduced, and the induced electromotive force can be canceled out in a larger number of regions.

[0017] In a fifth aspect, the present invention provides the optical voltage probe of the first aspect, wherein the first electric line and the second electric line have the intersection, and an area of ​​a region surrounded by a straight line connecting the tips of the first and second electric lines, the first and second electric lines, and the intersection, or an area of ​​a region surrounded by a straight line connecting the intersection and the rear ends of the first and second electric lines and the first and second electric lines, is adjustable.

[0018] In the present invention, when canceling out induced electromotive forces generated in portions before and after an intersection, it is necessary to equalize the areas enclosed by the electric lines before and after the intersection. In this aspect of the invention, a first electric line and a second electric line are configured to intersect with each other, and at least one of the areas enclosed by the first and second electric lines before and after the intersection is adjustable. As a result, for example, by equalizing the areas enclosed by the first and second electric lines before and after the intersection, induced electromotive forces generated in the portions of the first and second electric lines can be canceled out. Furthermore, when induced electromotive forces are generated in the first and second contact terminals, it is also possible to adjust the area so that the induced electromotive forces are canceled out by the induced electromotive forces generated in the first and second electric lines.

[0019] In a sixth aspect, the present invention is characterized in that the first electric line and the second electric line have the intersection, and the lengths of the first contact terminal and the second contact terminal are configured to be adjustable, thereby making it possible to adjust the area of ​​the region surrounded by the straight line connecting the tips of the first and second contact terminals, the first and second contact terminals, the first and second electric lines connected to the first and second contact terminals, respectively, and the intersection.

[0020] In this aspect of the invention, the first electric line and the second electric line are configured to cross each other, and the lengths of the first contact terminal and the second contact terminal are configured to be adjustable, thereby making it possible to adjust the area surrounded by the first and second contact terminals, thereby making it possible to adjust the total area surrounded by the first and second electric lines and the first and second contact terminals before the intersection.By making this adjustment so that the total area is equal to the area surrounded by the first and second electric lines after the intersection, it is possible to cancel out the induced electromotive forces generated before and after the intersection.

[0021] In a seventh aspect, the present invention provides the optical voltage probes of any one of the first to sixth aspects, characterized in that the optical modulator is an interferometric optical modulator using an optical waveguide formed on a lithium niobate crystal substrate. The invention of this aspect employs a conventional interferometric optical modulator using an optical waveguide formed on a lithium niobate crystal substrate as the optical modulator. The basic configuration of the interferometric optical modulator is an input optical waveguide extending from the light input side, two phase-shifting waveguides branching from the input optical waveguide, an output optical waveguide where the two phase-shifting waveguides join and connect to the light output side, and a modulation electrode arranged parallel to the phase-shifting waveguide. A voltage signal is applied to the phase-shifting waveguide via the modulation electrode to change the refractive index of the phase-shifting waveguide, and the light passing through the two phase-shifting waveguides joins and interferes, modulating the light intensity. Since a compact, highly efficient, and wide-band optical modulator can be obtained, it is suitable for the optical voltage probe of the present invention.

[0022] In the present invention, the modulation electrode can be a so-called segmented electrode consisting of multiple electrodes that are divided in the longitudinal direction and capacitively coupled to each other. A segmented electrode, in which one modulation electrode is divided into multiple capacitively coupled electrodes, is an effective means of improving the trade-off between the length and capacitance of the modulation electrode, which is related to modulation efficiency and modulation bandwidth. By using this segmented electrode, a high-efficiency, wide-band optical modulator can be obtained.

[0023] In an eighth aspect, the present invention provides the optical voltage probes of any one of the first to sixth aspects, characterized in that the optical modulator is an interferometric optical modulator using an optical waveguide formed on a lithium niobate crystal substrate, and is a reflective optical modulator that internally reflects and returns the incident light, and the input optical fiber and the output optical fiber are configured as a single input / output optical fiber. The reflective optical modulator of this aspect uses a configuration in which incident light is reflected in a phase-shift waveguide and returned to the incident-side optical waveguide. By using such a reflective optical modulator configuration, light transmits twice as far as a transmissive optical modulator for the same electrode length, thereby enabling the optical modulator to be more efficient, have a wider bandwidth, and be more compact. Furthermore, since only a single optical fiber is connected to the optical modulator, it is easier to handle. [Effects of the Invention]

[0024] As described above, the present invention provides an optical voltage probe that can reduce the influence of ambient fluctuating magnetic fields and more accurately measure voltage signals at points to be measured. [Brief explanation of the drawings]

[0025] [Figure 1] 1A and 1B are diagrams illustrating a schematic configuration of an optical voltage probe according to a first embodiment, in which FIG. 1A is a plan view of a transmission type and FIG. 1B is a side view of the transmission type. [Figure 2] FIG. 1 is a block diagram of a measurement system using an optical voltage probe according to a first embodiment. [Figure 3] 3A and 3B are diagrams illustrating an example of the configuration of a reflective optical modulator built into the optical voltage probe of Example 1, where FIG. 3A is a plan view and FIG. 3B is an AA cross-sectional view. [Figure 4] FIG. 10 is a plan view of a transmission type optical voltage probe according to a second embodiment, schematically illustrating the configuration thereof. [Figure 5] FIG. 10 is a plan view of a transmission type optical voltage probe according to a third embodiment, schematically illustrating the configuration thereof. [Figure 6] FIG. 10 is a plan view of a transmission type optical voltage probe according to a fourth embodiment, schematically illustrating the configuration thereof. DETAILED DESCRIPTION OF THE INVENTION

[0026] The optical voltage probe of the present invention will be described in detail below by way of examples with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals and redundant description will be omitted. [Example]

[0027] FIG. 1 is a diagram showing a schematic configuration of an optical voltage probe according to Example 1, where FIG. 1(a) is a plan view of a transmission type and FIG. 1(b) is a side view of the transmission type. 1, an optical voltage probe 10 of this embodiment 1 includes a modulating electrode 13 having a first electrode pad 11 and a second electrode pad 12, an optical modulator 1 that intensity-modulates incident light depending on the voltage between electrode pad 11 and electrode pad 12, and outputs the modulated light, and an input optical fiber and an output optical fiber connected to optical modulator 1. The optical modulator also includes a first contact terminal 3 and a second contact terminal 4 that can be brought into contact with a point to be measured, a wire 5 that is a first electrical line connecting contact terminal 3 and electrode pad 11, and a wire 6 that is a second electrical line connecting contact terminal 4 and electrode pad 12. The wires 5 and 6 intersect at an intersection 17 in a non-contact state. In this embodiment, optical modulator 1 is a reflective optical modulator that internally reflects and returns incident light, and the input optical fiber to optical modulator 1 and the output optical fiber from optical modulator 1 are formed by a single input / output optical fiber 2. The tip of the input / output optical fiber 2 is inserted into and fixed in a ferrule 7 in order to adhesively fix the input / output end face and the end face of the optical modulator 1 together.

[0028] The optical modulator 1, wiring 5, 6, and part of the input / output optical fiber 2 are housed in a package 8. The contact terminals 3 and 4 are configured to be detachable by being in contact with the respective metal cylindrical portions of contact terminal attachment parts 14 and 15 fixed to the package 8. The metal cylindrical portions are fixed inside a cylindrical insulator, and the insulator is fixed to the package 8. During measurement, the contact terminal 3 is inserted into the contact terminal attachment part 14, and the contact terminal 4 is inserted into the contact terminal attachment part 15. The wiring 5 and 6 are connected to their respective metal cylindrical portions.

[0029] The package 8 has a rectangular parallelepiped shape and is made of a metal plate such as aluminum to shield it from external electric fields. The optical modulator 1 is fixed to a base 9 fixed to the package 8, and the input / output optical fiber 2 is fixed to the package 8 by a rubber-like fixing part 16.

[0030] Next, a measurement system using the optical voltage probe 10 of this embodiment will be described. Figure 2 is a block diagram of a measurement system using an optical voltage probe according to Example 1. As shown in Figure 2, incident light 18 is sent to optical voltage probe 10 from optical transmitting / receiving unit 21 through input / output optical fiber 2, and optical intensity modulated signal 19 output from optical modulator 1 is input to transmitting / receiving unit 21 through the same input / output optical fiber 2. The optical transmitting / receiving unit 21 includes a light source 22 such as a semiconductor laser, an O / E converter 23, a transceiver separator 24 for separating the incident light 18 and the optical intensity modulated signal 19, and an amplifier 25. The light emitted from the light source 22 is coupled to the input / output optical fiber 2 through the transceiver separator 24, and the optical intensity modulated signal 19 returning from the input / output optical fiber 2 is input to the O / E converter 23 through the transceiver separator 24. In the O / E converter 23, the optical intensity modulated signal 19 is converted into an electrical signal, amplified by the amplifier 25, and output to an output terminal 26. The electrical signal is input to a measuring instrument 27 such as an oscilloscope. The transceiver separator 24 can be configured using an optical circulator, an optical fiber branch, or a semi-transparent mirror.

[0031] Figure 2 shows a case in which a voltage signal generated between two terminals of an electrical component 28, such as an IC, placed on a charged plate 29 as a point under test during an ESD test is measured. Contact terminals 3 and 4 of optical voltage probe 10 are brought into contact with the two terminals of electrical component 28 to be measured. As shown in Figure 1, the voltage signal input through contact terminals 3 and 4 is conducted to modulation electrode 13 via wires 5 and 6 and electrode pads 11 and 12, and this voltage signal is converted into an optical intensity modulated signal 19 by optical modulator 1. This optical intensity modulated signal 19 is converted into an electrical signal within optical transmitting / receiving unit 21. The voltage waveform generated between the two terminals of electrical component 28 can be determined by observing the voltage waveform with measuring instrument 27.

[0032] In an ESD test, a voltage is applied to the charged plate 29, and then the grounding needle 31 is brought into contact with the charged plate 29 to discharge the charge. This discharge then causes malfunction or damage to the electrical component 28, which is then inspected by measuring the voltage signal at the terminal under test. During this ESD test, a high voltage of several kilovolts is generated on the charged plate, and a current of several amperes may flow during discharge. This current generates a large fluctuating magnetic field in the surrounding area. In conventional optical voltage probes, when this magnetic field penetrates between contact terminals 3 and 4 or between wiring 5 and 6, an induced electromotive force is generated by the fluctuating magnetic field. This induced electromotive force is superimposed on the voltage signal between contact terminals 3 and 4 and applied between electrode pads 11 and 12, preventing accurate measurement of the voltage signal at the point under test.

[0033] On the other hand, in the optical voltage probe of this embodiment, as shown in Figure 1, by crossing wires 5 and 6 without contact, opposite induced electromotive forces are generated between wires 5 and 6 before and after intersection 17. Therefore, the induced electromotive forces cancel each other out, reducing the effects of fluctuating magnetic fields. Furthermore, in this embodiment, the area enclosed by the line connecting tips 3a and 4a of contact terminals 3 and 4, wires 5 and 6 connected via contact terminals 3 and 4, contact terminal mounting portions 14 and 15, and intersection 17 is set to be approximately equal to the area enclosed by the line connecting intersection 17, wires 5 and 6, and electrode pads 11 and 12 behind it. Since the magnitude of the induced electromotive force is proportional to the area of ​​this area when the magnetic flux density is the same, making the areas before and after the intersection equal can cancel out the induced electromotive force. This reduces the effects of fluctuating magnetic fields in the surroundings, enabling more accurate measurement of the voltage signal at the measurement point.

[0034] 3A and 3B are diagrams showing an example of the configuration of a reflective optical modulator 1 built into the optical voltage probe 10 of this embodiment, where FIG. 3A is a plan view and FIG. 3B is a cross-sectional view taken along line AA. 3, the optical modulator 1 is composed of a substrate 41 made by cutting an X-cut out of lithium niobate (LiNbO3) crystal, which is a crystal having an electro-optic effect, a branching interference type optical waveguide 42 made by Ti diffusion on the upper surface side of the substrate 41, a buffer layer 43 formed on the upper surface side of the substrate 41, a modulating electrode 13 formed on the buffer layer 43, and a light reflecting portion 45 installed at one end of the substrate 41. The modulating electrode 13 is a two-layer film of chromium (Cr) and gold (Au) formed by sputtering or the like.

[0035] The branching interference type optical waveguide 42 is composed of one input / output optical waveguide 42a extending on the input light incident side, and two phase-shift waveguides 42b and 42c branching off from the input / output optical waveguide 42a. The input / output optical waveguide 42a and the phase-shift optical waveguides 42b and 42c have the same width W in the direction perpendicular to the extension direction, ranging from 5 to 12 μm. The phase-shift optical waveguides 42b and 42c have approximately the same length in the extension direction, ranging from 10 to 30 mm. The phase-shift optical waveguides 42b and 42c extend parallel to each other, with their centers spaced apart by a predetermined distance ranging from 15 to 50 μm. The buffer layer 43 is provided for the purpose of preventing a portion of the light propagating through the optical waveguide 42 from being absorbed by the modulation electrode 13, and is made mainly of a silicon dioxide (SiO2) film or the like, with a thickness of about 0.1 to 1.0 μm.

[0036] In the optical modulator 1, the modulating electrode 13 is composed of electrode pads 11 and 12 and a divided electrode consisting of three electrodes 46, 47, and 48 that are divided in the longitudinal direction of the branching interference type optical waveguide 42 and are capacitively coupled to each other. Between the electrode pads 11 and 12, the electrodes 46 and 47, and the electrodes 47 and 48 are capacitively coupled to each other and arranged in series.

[0037] The input / output end face of the input / output optical fiber 2 is coupled to the optical input / output end of the input / output optical waveguide 42a of the substrate 41. The optical reflector 45 reflects light that enters the input / output optical waveguide 42a and propagates through the phase-shift optical waveguides 42b and 42c, and then propagates it back to the input / output optical waveguide 42a from the phase-shift optical waveguides 42b and 42c. When a voltage is applied between the electrode pads 11 and 12, electric fields are applied in opposite directions to the two phase-shift optical waveguides 42b and 42c between the electrodes 46 and 47 and between the electrodes 47 and 48. This causes refractive index changes in the phase-shift optical waveguides 42b and 42c in opposite directions, resulting in phase shifts of opposite polarities in the light passing through them. When these light beams merge, they interfere with each other, resulting in a change in intensity. This produces an optical intensity-modulated signal whose optical intensity changes in response to the voltage applied between the electrode pads 11 and 12.

[0038] An ESD test was performed using the optical voltage probe of this embodiment, and it was confirmed that the voltage signal at the measurement point could be accurately measured without being affected by the magnetic field generated by discharge. [Example]

[0039] FIG. 4 is a transmission-type plan view showing a schematic configuration of an optical-voltage probe according to Example 2. As shown in FIG. 4, in an optical-voltage probe 20 according to Example 2, an optical modulator 1 similar to that of Example 1 is installed and fixed in a package 31. In this example, contact terminal 33 is connected to wire 35 via terminal plate 37, and contact terminal 34 is connected to wire 36 via terminal plate 38. Furthermore, wires 35 and 36 are twisted together in a non-contact state and connected to electrode pads 11 and 12, respectively. By twisting wires 35 and 36 together in this way, the area surrounded by the wires and through which a fluctuating magnetic field passes is reduced, and induced electromotive forces are canceled out in multiple areas, thereby reducing the influence of the surrounding fluctuating magnetic field. [Example]

[0040] FIG. 5 is a transmission-type plan view schematically illustrating the configuration of an optical voltage probe according to Example 3. The optical voltage probe 30 of Example 3 has the same configuration as Example 1 except for the first and second electrical lines. In this example, a wire 55, which is a first electrical line, and a wire 56, which is a second electrical line, are configured to intersect with each other at an intersection 57 in a non-contact state, and the position of intersection 57 is configured to be movable before and after the intersection, i.e., left and right in FIG. 5. The solid lines in FIG. 5 indicate the case where intersection 57 of wires 55 and 56 is located on the side of contact terminals 3 and 4, and the dashed lines in FIG. 5 indicate the case where intersection 57 is located on the side of electrode pads 11 and 12.

[0041] As shown in Figure 5, the area enclosed by the solid lines before the intersection, i.e., the area enclosed by the wires 55 and 56 on the left side, is smaller than the area enclosed by the dashed lines. Conversely, the area enclosed by the solid lines after the intersection, i.e., the area enclosed by the dashed lines, is larger than the area enclosed by the dashed lines. In this way, by adjusting the position of intersection 57 forward or backward, it is possible to adjust the area enclosed by the line connecting the tips of wires 55 and 56, wires 55 and 56, and intersection 57, as well as the area enclosed by the line connecting intersection 57, wires 55 and 56, and the rear ends of wires 55 and 56. By making this adjustment so that the area enclosed by contact terminals 3 and 4 and wires 56 and 57 before intersection 57 is equal to the area enclosed by wires 56 and 57 after intersection 57, the induced electromotive forces generated before and after intersection 57 can be canceled out. This adjustment can be performed in various ways, for example, by making the lid of the package 8 removable, or by inserting an adjustment rod with its tip fixed to the intersection 57 from outside the package 8 so that it can be moved. [Example]

[0042] FIG. 6 is a transmission-type plan view schematically illustrating the configuration of an optical-voltage probe according to Example 4. Optical-voltage probe 40 according to Example 4 has the same configuration as Example 1 except for the first and second contact terminals. In this example, the lengths of first and second contact terminals, contact terminal 53 and contact terminal 54, are adjustable. Specifically, contact terminals 53 and 54 each comprise terminal needles 53a and 54a and metal tubes 53b and 54b that can be inserted and brought into contact with terminal needles 53a and 54a, respectively. The lengths of contact terminals 53 and 54, i.e., the lengths from the tips of terminal needles 53a and 54a to the rear ends of metal tubes 53b and 54b, can be adjusted by adjusting the insertion depth of terminal needles 53a and 54a into metal tubes 53b and 54b.

[0043] This makes it possible to adjust the total area enclosed by the wiring 5 and 6 before the intersection 17 and the contact terminals 53 and 54, and if the total area can be made equal to the area enclosed by the straight line connecting the wiring 5 and 6 after the intersection 17 and the electrode pads 11 and 12, the induced electromotive force generated in the parts before and after the intersection 17 can be canceled out.

[0044] Needless to say, the present invention is not limited to the above-described embodiments, and various modifications are possible depending on the purpose. For example, in order to cancel out induced electromotive forces, crossings can be provided not only in the wiring but also in the contact terminals. The optical modulator used may be not only a reflective type but also a transmissive type. Furthermore, the modulation electrode does not have to be a divided electrode. The shape and structure of the contact terminals and the contact terminal mounting portion can also be selected according to the purpose. Furthermore, the material, shape, and structure of the package can also be selected arbitrarily. For example, in addition to the rectangular parallelepiped shape of the above-described embodiments, cylindrical shapes and other shapes are also possible. [Explanation of symbols]

[0045] 1 Optical modulator 2 Input / Output Optical Fiber 3,4,33,34,53,54 Contact terminal 3a,4a tip 5,6,35,36,55,56 Wiring 7 Ferrules 8,31 packages 9. Pedestal 10,30,20,30,40 Optical Voltage Probe 11,12 Electrode pads 13 Modulation electrode 14,15 Contact terminal mounting part 16 Fixing parts 17,57 Intersection 18 Incident light 19 Optical Intensity Modulation Signal 21 Optical transmitting and receiving unit 22 Light source 23 O / E converter 24 Transmitter / receiver separator 25 amps 26 Output terminal 27 Measuring instruments 28 Electrical Components 29 Charged plate 31 Ground needle 37,38 Terminal board 41 PCB 42 Branching and interference optical waveguide 42a Input / output optical waveguide 42b, 42c Phase-shifting optical waveguide 43 Buffer layer 45 Light reflection part 46,47,48 electrode 53a,54a Terminal needle 53b,54b Metal tube

Claims

1. An optical voltage probe for measuring a voltage signal at a point under test, an optical modulator comprising a modulation electrode having a first electrode pad and a second electrode pad, and configured to intensity-modulate incident light depending on a voltage between the first and second electrode pads and output the modulated light; an input optical fiber and an output optical fiber connected to the optical modulator; a first contact terminal and a second contact terminal that can come into contact with the point to be measured; a first electrical line connecting the first contact terminal and the first electrode pad; and a second electrical line connecting the second contact terminal and the second electrode pad. a package that houses the optical modulator, at least a portion of the first and second electrical lines, and a portion of the input optical fiber and the output optical fiber; a voltage signal induced between the first and second electrode pads via the first and second contact terminals is converted into an optical intensity modulated signal by the optical modulator and output from the output optical fiber; the first contact terminal and the second contact terminal, or the first electric line and the second electric line, have an intersection where they intersect with each other in a non-contact state; an optical voltage probe configured such that, when a magnetic field passing between the first and second contact terminals or between the first and second electric lines fluctuates, induced electromotive forces in opposite directions are generated between the first and second contact terminals or between the first and second electric lines in the portions before and after the intersection by the fluctuating magnetic field.

2. The fluctuating magnetic field is a magnetic field generated by an electrical load in a test environment in which an electrical load is applied to an electrical circuit or an electrical component, 2. The optical voltage probe according to claim 1, wherein the point to be measured is a point to be measured within the electrical circuit or electrical component.

3. 2. The optical voltage probe according to claim 1, wherein the first contact terminal and the second contact terminal, or the first electrical line and the second electrical line, have a plurality of intersections.

4. 2. The optical voltage probe according to claim 1, wherein the first electric line and the second electric line are twisted together in a non-contact state.

5. 2. The optical voltage probe according to claim 1, wherein the first electric line and the second electric line have the intersection, and an area of ​​a region surrounded by a straight line connecting the tips of the first and second electric lines, the first and second electric lines, and the intersection, or an area of ​​a region surrounded by a straight line connecting the intersection, the first and second electric lines, and the rear ends of the first and second electric lines, is adjustable.

6. 2. The optical voltage probe according to claim 1, wherein the first and second electric lines have the intersection, and the lengths of the first and second contact terminals are adjustable, thereby making it possible to adjust the area of ​​a region surrounded by a straight line connecting the tips of the first and second contact terminals, the first and second contact terminals, the first and second electric lines connected to the first and second contact terminals, respectively, and the intersection.

7. 7. The optical voltage probe according to claim 1, wherein the optical modulator is an interferometric optical modulator using an optical waveguide formed on a lithium niobate crystal substrate.

8. 7. The optical voltage probe according to claim 1, wherein the optical modulator is an interferometric optical modulator using an optical waveguide formed on a lithium niobate crystal substrate, and is a reflective optical modulator that internally reflects and returns the incident light, and the input optical fiber and the output optical fiber are configured as a single input / output optical fiber.

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