JPH0720177A - Optical field sensor - Google Patents

Abstract

PURPOSE:To provide an optical field sensor wherein an outer package including antenna elements is downsized as much as possible and its handling is simplified. CONSTITUTION:An optical field sensor is structured so that an optical waveguide 1 is split on an optical substrate 2 (a part of 8) attached in a package 9, an electric field to be measured which is parallel to a crystal axis of the optical substrate is applied via a pair of antenna elements to the split optical waveguide for fluctuating a phase of waveguide light and waves are combined again to measure light intensity, wherein the pair of antenna elements 11 are placed oppositely to each other in parallel to the optical waveguide 1 with a center on a side of the package 9 as an end, or they are attached to an outer wall of the side of the package oppositely to each other in parallel to the optical waveguide 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric field light sensor, which is represented by EMC measurement (noise measurement) and is used for measuring the electric field strength in a field.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing the structure of a conventional optical electric field sensor as viewed from above. After branching the optical waveguide 1 formed on the LiNbO ₃ substrate 2 which is an optical crystal, an electric field parallel to the crystal axis of the substrate is applied to one or both of the branched optical waveguides to phase the guided light. An optical waveguide Mach-Zehnder interferometer is formed up to the point where it is varied and recombined. Since this interferometer changes the light intensity after the combination by the applied voltage, the antenna element is provided via the lead wire 5a to the control electrode 5 provided in the optical axis direction to apply the electric field in the crystal axis direction. Connect 3. The antenna element 3 is fixed to a package (not shown). Here, when input light is taken in from the optical fiber 4 and a minute voltage applied from the antenna element 3 to the control electrode 5 is measured, an optical field sensor of an optical waveguide type is obtained. In this optical electric field sensor, not only the antenna element can be made relatively small, but also the metal portion excluding the antenna element, particularly the coaxial cable is not required, and therefore the electric field can be measured without disturbance.

In the above structure, the antenna element 4 is generally arranged so as to be orthogonal to the longitudinal direction of the element. This is due to the position of the extraction electrode, and is for efficiently extracting from the control electrode 3 that changes the phase of the guided light of the optical waveguide. However, in the optical electric field sensor having such a configuration, the antenna element is oriented in the electric field direction as shown in the figure at the time of measurement, so that the extraction portion of the optical fiber 4 is oriented in the measurement direction. For this reason, not only the optical fiber may be damaged, but also the overall structure is large and the handling is inconvenient.

[0004]

DISCLOSURE OF THE INVENTION The present invention focuses on this antenna element and provides an optical electric field sensor in which the exterior part including the antenna element is made as small as possible to facilitate handling.

[0005]

According to the present invention, after branching an optical waveguide on an optical substrate mounted in a package, the branched optical waveguide is measured parallel to the crystal axis of the optical substrate. In an optical electric field sensor configured to apply an electric field through a pair of antenna elements and a control electrode to change the phase of guided light and combine them again to measure light intensity, the pair of antenna elements includes the package. An optical electric field sensor is obtained, which is a rod antenna element that is arranged in parallel to the optical waveguide in opposite directions with the central portion of the side surface of the one end as one end. The pair of antenna elements may be thin-film antenna elements that are formed on the outer wall of the side surface of the package in parallel with the optical waveguide in opposite directions with the center of the outer wall as one end.

[0006]

1 is a plan view of an optical electric field sensor according to a first embodiment of the present invention, in which an optical waveguide 1 of a Mach-Zehnder interferometer is formed on a Z surface of a LiNbO ₃ Z substrate 2 by thermal diffusion of Ti. Then, the polarization-maintaining optical fiber 6 was connected to the light incident side so as to have the TE input, and the single mode optical fiber 7 was connected to the light emitting side. The size of the element is 36 × 5 × on the substrate
It was set to t0.5 mm. 40 × 12 × for the entire package 9
It is 6 mm. Two lead wires 10 are led out from a lead electrode (not shown) of the optical modulator 8 to the side surface of the package 9, and a pair of rod antenna elements 11 are arranged in opposite directions. That is, it is a sensor that should be called a rod antenna parallel arrangement type optical electric field sensor.

FIG. 2 is a perspective view of the second embodiment of the present invention. This embodiment differs from the above-mentioned embodiments in that a pair of printed antenna elements 12 are patterned with gold electrodes in a direction opposite to the side surface of the package 9.
As a comparative example, an optical electric field sensor having the structure shown in FIG. 3 was manufactured. That is, it should be called a package print parallel arrangement type optical electric field sensor.

First, comparing the size of the optical electric field sensor including the antenna with FIG. 1 of the present invention and FIG. 3 of the comparative example, the optical electric field sensor of the present invention becomes extremely small without needing to look at the above-mentioned dimensions. ing. Particularly, in the case of the second embodiment shown in FIG. 2, it is extremely remarkable and structurally strong.

Next, in order to know whether or not the characteristics of the optical electric field sensor of the present invention have been changed by the above modification, the configuration shown in FIGS. 1, 2 and 3 is used. The following three types of optical electric field sensors were prepared to measure the frequency characteristics and the sensitivity characteristics by the electric field strength. The characteristics of the optical electric field sensor produced at that time as a Mach-Zehnder interferometer are as follows: optical modulation characteristics, insertion loss, extinction ratio, half-wave voltage, optical bias position in the first example, the second example, and the comparative example. In both cases, the same elements were selected and the electrodes were formed and measured. The measurement was performed by generating an electric field in the anechoic chamber through the three types of manufactured elements.

Regarding the measured values, the electric field sensor using the present invention of FIG. 1 or FIG. 2 has no variation in its sensitivity characteristics (maximum sensitivity 80 dB μV / m, 0 to 2) as compared with the conventional type of FIG.
There was no sensitivity fluctuation up to GHz), and almost the same sensitivity characteristics were obtained. FIG. 4 shows an example thereof, and the frequency characteristics of measurement sensitivity are the same between the present invention type and the conventional type to the extent that they cannot be distinguished. The same applies to other characteristics. Therefore, it was confirmed that the optical electric field sensor characteristics were not deteriorated even when the present invention was used.

[0011]

From the above results, it is understood that the optical electric field sensor of the present invention can be miniaturized without deterioration of characteristics. Also, since the measurement arrangement direction is parallel to the optical fiber, it is possible to arrange the optical fiber linearly without bending, and the handling of the element during measurement is greatly improved.

[Brief description of drawings]

FIG. 1 is a schematic top view of the configuration of an optical electric field sensor according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a configuration of an optical electric field sensor according to a second embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the frequency and the measurement sensitivity of the optical electric field sensor of the present invention and the optical electric field sensor of the comparative example.

[Explanation of symbols]

1 Optical Waveguide 2 LiNbO ₃ Z Substrate 3 Antenna Element 4 Optical Fiber 5 Control Electrode 5a Lead Wire 6 Constant Polarization Optical Fiber 7 Single Mode Optical Fiber 8 Optical Modulator 9 Package 10 Lead Wire 11 Rod Antenna Element 12 Printed Antenna Element

Claims (2)

[Claims] 1. After branching an optical waveguide on an optical substrate mounted in a package, the branched optical waveguide is provided with a pair of an antenna element and a control electrode for measuring a measured electric field in parallel to a crystal axis of the optical substrate. In the optical electric field sensor configured to vary the phase of the guided light by applying through, and combine again to measure the light intensity, the antenna elements of the pair, the central portion of the side surface of the package as one end, An optical electric field sensor comprising rod antenna elements which are arranged in parallel to an optical waveguide and opposite to each other. 2. A pair of antenna elements and a control electrode for branching an optical waveguide on an optical substrate mounted in a package, and applying a measured electric field to the branched optical waveguide in parallel with a crystal axis of the optical substrate. In the optical electric field sensor configured to vary the phase of the guided light by applying through, and combine again to measure the light intensity, the pair of antenna elements are provided on an outer wall of a side surface of the package, and a center of the outer wall. An optical electric field sensor, wherein the thin film antenna element is formed by depositing one end of the thin film antenna in parallel with the optical waveguide in the opposite direction.