JP2006313072A - Triaxial optical field sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact triaxial optical field sensor of high sensitivity capable of enhancing spatial resolution since a separation distance is narrowed between antennas. <P>SOLUTION: This triaxial optical field sensor has a structure of arranging on respective side faces of an equilateral triangle pole base block 5 a light modulator part 1 comprising a Mach-Zehnder interferometer for measuring orthogonal triaxial-directional electric fields, and a uniaxial optical field sensor comprising a metal antenna electrode 3 formed on a printed board, and is arranged in structure with a field detecting direction of the antenna tilted by about 54.7°with respect to a direction of a branched optical waveguide, and with the printed board 2 crossed three-dimensionally with the adjacent printed board 2 to detect the triaxial-directional electric fields orthogonal to each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical electric field sensor that measures an electric field by utilizing an electro-optic effect, and in particular, measurement of electric field strength in three orthogonal axis directions and total electric field strength obtained by a combined calculation of the electric field strengths in the three axis directions. The present invention relates to a three-axis optical electric field sensor suitable for.

An optical electric field sensor using an interference optical waveguide utilizing the electro-optic effect has the following excellent properties.
(1) Since there is almost no metal part except the antenna, the electric field to be measured is not disturbed.
(2) Since the detection signal is transmitted through an optical fiber, it is not affected by guidance or electrical noise on the way.
(3) Since the electro-optic effect of the crystal is used, high-speed response is possible, and the detection signal can be transmitted as it is with little loss.
(4) No power is required for the sensor unit.
Due to these characteristics, the optical electric field sensor is used for a wide range of electric field measurements in the EMC field.

  A conventional triaxial optical electric field sensor for detecting electric fields in three orthogonal directions is composed of three uniaxial optical electric field sensors each having a metal electrode on which an optical modulation electrode and an antenna electrode for electric field detection are integrated on an electro-optic substrate. Some are arranged on each side of a regular triangular prism (see Patent Document 1).

  Hereinafter, a conventional three-axis optical electric field sensor will be described with reference to FIGS. 4, 5, and 6. FIG. 4 is a perspective view showing the structure of a reflective uniaxial optical electric field sensor used to measure a uniaxial electric field used in a conventional triaxial optical electric field sensor. FIG. 5 is a perspective view showing the structure of a conventional triaxial optical electric field sensor. FIG. 6 is a cross-sectional view of a conventional triaxial optical electric field sensor as viewed from above.

As shown in FIG. 4, the light incident from the optical fiber 4 is branched into two branched optical waveguides 8a and 8b through an optical waveguide 7 on a LiNbO ₃ substrate 6 which is an electro-optic crystal substrate. When an electric field is applied to one branched optical waveguide 8a by the metal electrode 9, a refractive index change occurs in the branched optical waveguide 8a, whereas a refractive index change due to the electric field does not occur in the branched optical waveguide 8b. Light propagating through any of the branch optical waveguides is reflected by the reflection mirror 10, propagates in the opposite direction through the branch optical waveguide, and is multiplexed again. Thereafter, the combined light is emitted to the optical fiber 4, guided to the photodetector, and converted into an electrical signal. The combined light intensity changes according to the phase difference caused by the refractive index difference between the two optical paths. This change in light intensity corresponds to a change in the intensity of the detected electric field.

  The metal electrode 9 is formed so as to be an electric field detection antenna having high sensitivity in the electric field detection direction inclined by 54.7 ° with respect to the branched optical waveguides 8a and 8b. Next, by arranging the reflective uniaxial optical electric field sensor shown in FIG. 4 on each side surface of the equilateral triangular prism fixed base as shown in FIG. 5, a triaxial optical electric field that can measure electric fields in three orthogonal directions. Create a sensor. As shown in FIG. 6, it can be seen that the width of the uniaxial optical electric field sensor is the same or shorter than the length of each side of the regular triangular prism section due to the structure.

Japanese Patent Laid-Open No. 2004-219088

The easiest way to increase the sensitivity of the optical electric field sensor is to increase the antenna length. In the above-described triaxial electric field measurement optical electric field sensor disclosed in Patent Document 1, the optical modulation electrode and the electric field measurement antenna are integrally formed on the electro-optic crystal substrate. In this case, the electro-optic crystal substrate serving as a base has to be increased in accordance with the antenna length. However, when the electro-optic crystal is enlarged, there is a problem that the distance to the center of the antenna between the axes becomes longer and the three-dimensional measurement resolution is deteriorated. Further, since the electro-optic crystal substrate for light modulation such as LiNbO ₃ and LiTaO ₃ has a high dielectric constant, there is a problem that the influence on the electric field to be measured cannot be ignored when the substrate is enlarged. Furthermore, the electro-optic crystal substrate is difficult and expensive to process into a complicated shape. Therefore, it is better in terms of cost if the electro-optic crystal substrate is as small as possible and the processing shape is simple. In addition, a three-axis optical electric field sensor having a structure resistant to humidity change as much as possible has been demanded.

  The present invention has been made to solve the above-mentioned problems, and a technical problem thereof is to provide a three-axis optical electric field sensor having a high sensitivity, a small size, a high spatial resolution, and a structure resistant to humidity change. .

  The first invention for achieving the above object comprises three branched optical waveguide type Mach-Zehnder interferometers in which a branched optical waveguide and a metal electrode comprising an antenna mounting electrode and a modulation electrode are formed on an electro-optic crystal substrate. In a three-axis optical electric field sensor for detecting electric fields in three axial directions orthogonal to each other, a direction inclined approximately 54.7 ° from the direction of the branch optical waveguide on a printed circuit board having a longitudinal direction in the same direction as the branch optical waveguide A metal antenna is formed on the printed circuit board, and the printed circuit board has rectangular cutouts at two corners on a rectangular diagonal line, and the lengths of the cutout parts in the longitudinal direction are the other diagonal lines. The length of the projecting portion that protrudes relatively by the formation of the notch portion is longer than the length in the longitudinal direction, and the metal antenna is formed over the entire width of the rectangle. The branched optical waveguide type Mach-Zehnder interferometers are arranged on three side surfaces of the regular triangular prism base, respectively, and are arranged so that the notches of the printed circuit board and the convex parts of the adjacent printed circuit board intersect three-dimensionally. This is an axial optical electric field sensor.

  A second invention for achieving the above object is a three-axis optical electric field sensor in which the branched optical waveguide type Mach-Zehnder interferometer has a common input and output and is a reflection type.

  A third invention for achieving the above object is a three-axis optical electric field sensor including a container for vacuum-sealing the branched optical waveguide type Mach-Zehnder interferometer.

  According to the present invention, three branch optical waveguide type Mach-Zehnder interferometers in which a branch optical waveguide and a metal electrode composed of an antenna mounting electrode and a modulation electrode are formed on an electro-optic crystal substrate are provided, and the three axial directions are orthogonal to each other. In the three-axis optical electric field sensor for detecting the electric field, the upper side of the main surface of the printed circuit board has a wide portion on the left side with respect to the direction of the branch optical waveguide, and the lower side of the main surface of the printed circuit board is A uniaxial optical electric field sensor made of a metal antenna formed on a printed circuit board having a bowl-like shape with a wide portion on the right side with respect to the direction of the branch optical waveguide. It is placed on the three sides of the equilateral triangular prism base so that it can detect electric fields in three axes perpendicular to each other at an angle of 7 °. In, to achieve 3-axis optical electric field sensor of a very simple and compact construction, it is possible to narrow the distance between the three axes, it can increase the spatial resolution of the three-axis optical field sensor. Further, the branch optical waveguide type Mach-Zehnder interferometer can realize a smaller three-axis optical electric field sensor by making the input / output common and making it a reflection type. Furthermore, a three-axis optical electric field sensor that is resistant to changes in humidity can be realized by providing a light modulation base made of a glass container to be vacuum-sealed.

  As a result, it is possible to provide a three-axis optical electric field sensor having a high sensitivity, a small size, a high spatial resolution, and a structure resistant to humidity change.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a uniaxial optical electric field sensor according to the best mode for carrying out the present invention. FIG. 2 is a schematic perspective view showing a three-axis optical electric field sensor according to the best mode for carrying out the present invention. FIG. 3 is a cross-sectional view of the triaxial optical electric field sensor according to the best mode for carrying out the present invention as seen from the upper surface.

A uniaxial optical electric field sensor according to the best mode for carrying out the present invention includes a Ti diffusion waveguide fabricated on an electro-optic substrate such as LiNbO _3, a metal electrode for applying a voltage thereto, a reflection mirror, and an optical fiber. It comprises a Mach-Zehnder interferometer configured and a printed circuit board on which an antenna electrode is arranged and a glass container 12 (see FIG. 3) for vacuum-sealing the Mach-Zehnder interferometer.

  As shown in FIG. 1, 1 is a Mach-Zehnder interferometer, 2 is a printed circuit board, 3 is a metal antenna electrode formed on the printed circuit board, and 4 is an optical fiber. The metal antenna electrode pattern is formed in a shape extending in a direction inclined approximately 54.7 ° with respect to the direction of the branched optical waveguide on the regular triangular prism base used for the configuration of the triaxial optical electric field sensor. At maximum sensitivity. In the printed circuit board, the upper side of the main surface of the printed circuit board has a wide portion on the left side about the direction of the branch optical waveguide, and the lower side of the main surface of the printed circuit board is wide on the right side about the direction of the branch optical waveguide. When a three-axis optical electric field sensor is formed, the shape is formed by combining two ridges with a portion, and is formed in a shape that three-dimensionally intersects with the adjacent printed circuit board and the center of the metal antenna as a boundary.

  As shown in FIG. 2, the uniaxial optical electric field sensor shown in FIG. 1 is arranged on each side of the regular triangular prism base 5. As shown in FIGS. 3 and 4, the electric field detection directions of the three uniaxial optical electric field sensors are orthogonal to each other.

  As described above, the triaxial optical electric field sensor according to the best mode for carrying out the present invention has a wide portion on the left side with respect to the direction of the branched optical waveguide on the upper side of the main surface of the printed circuit board. The lower side of the main surface is a uniaxial optical electric field sensor composed of a metal antenna formed on a printed circuit board having a bowl-like shape with a wide portion on the right side with respect to the direction of the branch optical waveguide. By arranging the three sides of the equilateral triangular prism base so as to detect electric fields in three axis directions perpendicular to each other inclined approximately 54.7 ° from the direction of the A triaxial optical electric field sensor having a simple and small structure is realized. Since the distance between the three axes can be reduced, the spatial resolution of the three-axis optical electric field sensor can be increased. Further, the branch optical waveguide type Mach-Zehnder interferometer can realize a smaller three-axis optical electric field sensor by making the input / output common and making it a reflection type. Furthermore, a three-axis optical electric field sensor that is resistant to changes in humidity can be realized by providing a light modulation base made of a glass container to be vacuum-sealed.

  As a result, a three-axis optical electric field sensor that does not take a method of increasing the sensitivity by increasing the antenna length like a conventional three-axis optical electric field sensor having a high sensitivity, a small size, a high spatial resolution, and a structure resistant to humidity change. Provision is possible.

The front view which shows the uniaxial optical electric field sensor which concerns on the best form for implementing this invention. 1 is a schematic perspective view showing a triaxial optical electric field sensor according to the best mode for carrying out the present invention. Sectional drawing seen from the upper surface of the triaxial optical electric field sensor which concerns on the best form for implementing this invention. The perspective view which shows the structure of the reflection type uniaxial optical electric field sensor which measures the electric field of the uniaxial direction used for the conventional triaxial optical electric field sensor. The perspective view which shows the conventional triaxial optical electric field sensor. Sectional drawing which looked at the conventional triaxial optical electric field sensor from upper direction.

Explanation of symbols

1 the optical modulator unit 2 printed circuit board 3 metal antenna electrode 4 optical fiber 5 regular triangular prism base 6 LiNbO ₃ substrate 7 waveguide 8a, 8b branching optical waveguide 9 metal electrode 10 reflecting mirror 11 one-axis light field sensor

Claims (3)

  Three branch optical waveguide type Mach-Zehnder interferometers each having a branch optical waveguide and a metal electrode composed of an antenna mounting electrode and a modulation electrode formed on an electro-optic crystal substrate are provided to detect electric fields in three axial directions orthogonal to each other. In the axial optical electric field sensor, a metal antenna is formed on a printed circuit board having a longitudinal direction in the same direction as the branched optical waveguide in a direction inclined approximately 54.7 ° from the direction of the branched optical waveguide, and the shape of the printed circuit board is A rectangular cutout is provided at each of two corners of the rectangular diagonal, and the length of each of the cutouts in the longitudinal direction is relatively convex due to the formation of the other cutout on the diagonal. The metal antenna is formed over the entire width of the rectangle, and the branched optical waveguide type Mach-Zehnder interferometer is A triaxial optical electric field sensor, which is arranged on each of three side surfaces of a triangular prism base, and is arranged so that the notch portion of the printed circuit board and the convex portion of the adjacent printed circuit board intersect three-dimensionally. .   2. The three-axis optical electric field sensor according to claim 1, wherein the branched optical waveguide type Mach-Zehnder interferometer is a reflection type with a common input / output.   The triaxial optical electric field sensor according to claim 1 or 2, further comprising a container for vacuum-sealing the branched optical waveguide type Mach-Zehnder interferometer.

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