JPS6063417A - Measuring device - Google Patents

Abstract

PURPOSE:To prevent variance of the optical loss in an optical fiber to improve the precision of measurement by transmitting multiplexed lights with one optical fiber in wavelength multiplex and branching the exit light of the optical fiber to wavelengths of two vertical polarized components with a branching filter and subjecting them to photoelectric conversion. CONSTITUTION:One component of the light made incident to a polarizing beam splitter 17 is transmitted through the plane of polarization and a filter 21 as shown by a solid line and is converted to a prescribed wavelength and exit to a microlens 8. The other is reflected on the plane of polarization and strikes a reflective mirror 24 and is turned at 180 deg. as shown by a broken line. Meanwhile, the light made incident to a polarizing beam splitter 18 is converted to a prescribed wavelength by the filter 21, and one component is transmitted through the plane of polarization and exits to the lens 8. The other is reflected on the plane of polarization and is returned in the incidence direction. This light is branched to two vertical polarized components by an analyzer 25, and they are converted to wavelengths different from each other and are multiplexed in wavelength multiplex, and the multiplexed light is condensed by the lens 8 and is transmitted by one optical fibe 10 and is branched to two vertical polarized components by a branching filter 26, and they are subjected to photoelectric conversion by optical receivers 12 and 13. They are preocessed by an operator so that a ratio of the difference to the sum of these electric outputs is operated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a measuring device that applies polarization of light.

[Prior art]

Figure 1 shows a conventional measurement device that applies polarization of light. (1) is a light source, (2) is an optical fiber, (3) is a microlens, (4) is a polarizer, (5) is a photoelastic element, (
6) is an IA wavelength plate, (7) is an analyzer that splits and emits vertically polarized light into two components, (8) and (9) are microlenses,
QO, (11) is an optical fiber, (12) and (13) are optical receivers, α4) is an adder, 05) is a subtracter, and 06) is a divider. A computing unit is configured.

With this configuration, the light emitted from the light source (1) passes through the optical fin (2) and passes through the microlens (2).
3), the light is made into a parallel beam, and the polarizer (4) converts the light into linearly polarized light. The photoelastic element (5) is configured such that a pressure to be measured is applied to its negative surface, and the applied pressure causes a birefringence phenomenon. For example, photoelastic element (5)
If it is an isotropic medium, the refractive index in the pressure direction and the two directions perpendicular to it will be different. Therefore, when light having an electric field component in the pressure direction and light having an electric field component perpendicular thereto are simultaneously incident on the photoelastic element (5), a phase difference occurs at the output end. For example, a polarizer (
When the linearly polarized light of the output of 4) is incident on the photoelastic element (5) at an angle of 450 with respect to their axes, the output of this photoelastic element (5) becomes elliptically polarized depending on the pressure. become.

This elliptically polarized light is further processed by a 1/4 wavelength plate (6).
Apply a phase difference of 0° and apply an optical bias to the analyzer (7
) is split into two polarized components at right angles to each other, the light of each component is de-lighted by microlenses (8) and (9), and passed through optical fibers QQ and (11) to an optical receiver (12).
), (13) performs photoelectric conversion. By performing the sum and difference of these electrical outputs in an adder (14) and a subtracter (), and processing the division of both the sum and difference in a divider (06), the light source (
It is not affected by the fluctuations in 1) and generates electrical output according to the pressure. Thereby, the pressure applied to the photoelastic element (5) is measured as an electrical output.

By the way, the conventional measuring device performs (3) to (3) as described above.
9) from the optical sensor consisting of two optical fibers,
Since two optically modulated components of light are transmitted, variations in optical loss between the two optical fibers have caused measurement errors. For this reason, there was a drawback that it was difficult to improve measurement accuracy.

[Summary of the invention]

This invention was made to eliminate the above drawbacks.
The analyzer is configured to split the passing light into two perpendicularly polarized components, convert the two polarized components into wavelengths with different wavelength ranges, and combine them.The combined light is then connected to a single optical fiber. By transmitting the light at a multiple wavelength of 1, the output light from the optical fiber is split into wavelengths of two perpendicularly polarized components using a demultiplexer, and photoelectrically converted, thereby preventing changes in optical loss in the optical fiber. , tears 10 self-contained hemp and Tonas offers πL odd needle flood 11 kanshin.

[Embodiments of the invention]

FIG. 2 is a configuration diagram showing an embodiment of the present invention, (1) to
(6), (8), I) (J, Q2) ~06
) is exactly the same as the conventional one, and (25) is a V4 wave plate (
an analyzer that splits the light received from
6) The light transmitted by the optical fiber (αQ) is passed through the analyzer (25
) is a demultiplexer that separates each wavelength of the two polarized light components emitted from the analyzer (25). , (]8) is a second polarizing beam splitter, and each polarizing beam splitter (17) and (18) has a polarizing plane arranged between a pair of right-angled prisms that are aligned so that their long sides face each other. The planes of polarization are aligned at right angles to each other. (1 is each polarizing beam splitter 07) (18
) is placed between the IA wave plate, (20) is a tracing plate, and
0 (21) placed at the end of the A wavelength plate 09) is a first filter placed on a predetermined surface of each polarizing beam splitter Q7) (18), which converts the transmitted light into a predetermined wavelength. do. (22) is a second filter, which is arranged on the surface facing the V4 wavelength plate 09) of the first polarization splitter (17), and sets the wavelength of the transmitted light to the wavelength transmitted through the first filter (21). Convert to a different wavelength.

(23) is a 1A wavelength plate, which is placed facing the second filter (22). (24) is a reflecting mirror, which is placed opposite to the wavelength plate (23). Above 07)~(2
4) constitutes an analyzer (25).

In such an analyzer (25), the light emitted from the wavelength plate (6) is transmitted to the first and second polarizing beam splitters (17) and (18).
The analyzer (25
) is adjusted so that the emitted light almost uniformly enters the microlens (8).

Next, the operation of the analyzer (25) will be explained with reference to FIG. When the output light of the IA wave plate (6) is incident from above in the figure, the first and second wave plates (6) are distributed almost equally across the IA wave plate (1).
is incident on the polarizing beam splitter (17) Q8).

At this time, the light incident in the thickness direction of the 1μ wavelength plate 0 is returned to the incident direction by the light shielding plate ((9).

One component of the light incident on the first polarizing beam splitter 07) passes through the polarization plane and the first filter (21) as shown by the solid line in the figure, is converted into a predetermined wavelength, and is sent to the microlens (8). It is emitted to. In addition, the remaining components are reflected by the polarization plane and sent to the second filter (22), as shown by the broken line in the figure.
, passes through the x/e wave plate (23) and reaches the reflector (24) to change the direction of the IBcP. During this time, the wavelength of the light is converted by the second filter (22), and the phase of the light is changed to 90
degree, the first polarizing beam splitter (passes through the 1θ polarization plane 100 times and passes through the wave plate (19). This causes the phase to change by an additional 9 dl), so the second polarizing beam splitter (18 ) 100% on the polarization plane
It is reflected, changes its angle by 90 degrees, and is emitted to the microlens (8). On the other hand, the polarizing beam splitter (18
) is converted into a predetermined wavelength by the first filter (21), and one component is transmitted through the polarization plane and output to the microlens (3). At this time, the remaining component is reflected by the polarization plane and returned to the incident direction.

Therefore, the light that is split into two vertically polarized components by the analyzer (25), converted into P wavelengths, and combined in wavelength multiplexing is condensed by the microlens (3) and becomes one light beam. It is transmitted through the fiber αQ, split into two vertically polarized components by the splitter (26), and sent to the respective optical receivers (12) (1
3) is photoelectrically converted. As in the past, processing is performed by a computing unit to calculate the ratio of the sum and difference of each electrical output.

Figure 4 shows the wavelength spectrum and filter characteristics of a light source.If a light source such as a light emitting diode (r, . Within the wavelength range of this light source, if you install a narrow band filter as shown in Figure 4 in the region as close as possible to the center wavelength so that the transmission wavelengths do not overlap with each other, it is possible to use one polarized light component as an analyzer. becomes the light with the wavelength of (B), and the other mutually perpendicular polarized component becomes the light with the wavelength of (B).Also, as shown in Figure 4-0, one side with the center wavelength of the light source as the border, The filter allows light in the short wavelength range to pass through, and the other filter allows light in the long wavelength range to pass through, and by making sure that the wavelengths do not overlap, it is possible to wavelength-separate the two orthogonally polarized light components. Can be separated by shape.

In the above embodiment, a case has been described in which the detection element is a photoelastic element and the physical quantity to be measured is pressure, but it is also possible to measure a magnetic field or an electric field using a Faraday element or a Pockels element.

〔Effect of the invention〕

As explained above, according to the present invention, the analyzer is configured to split the incident light into two perpendicular meridional light components, convert each polarized light component to a different wavelength, and combine the light into wavelength multiplexers. However, the output light from the analyzer is transmitted through a single optical fiber, and the output light from the optical fiber is split into two vertically polarized components for photoelectric conversion, thereby preventing changes in optical loss in the optical transmission section. can do. This has the effect of improving measurement accuracy.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional measuring device, Fig. 2 is a block diagram showing an example of the present invention, Fig. 3 is a detailed diagram of an analyzer, and Fig. 4 is a block diagram of a conventional measuring device.
The figure is a characteristic diagram of the filter. In the figure, (1) is the light source, (2) is the first optical fiber, (3) is the microlens, (4) is the polarizer, (5) is the detection element, (8) is the microlens, and the head is the first optical fiber. 2 optical fibers, (12) (1,1
) is an optical receiver, 04) to (kon are arithmetic units, (26) is an analyzer, and (26) is a demultiplexer. The same reference numerals in each figure indicate the same or equivalent parts. Agent: Oiwa Masuo Figure 1 Figure 4

Claims (1)

[Claims] (1) One light source, a first optical fiber that transmits the light of this light source, a first microlens that converts the output light of the first light beam into a parallel beam, this first A polarizer that keeps the plane of polarization of the parallel beam of the microlens constant, a detection element whose optical characteristics change depending on the physical quantity to be measured, and a detection element that splits the light that has passed through this detection element into two perpendicularly polarized components. An analyzer that converts the components into wavelengths with different wavelength ranges and combines them, a second microlens that collects the light emitted from this analyzer, and a second microlens that transmits the light emitted from this second microlens. a second optical fiber, a demultiplexer disposed at the exit of the second optical fiber for wavelength-separating the two vertically polarized components from the analyzer, an optical receiver for photoelectrically converting the light emitted from the demultiplexer; (2) The analyzer is equipped with a calculation unit designed to take the ratio of the sum and difference of each electrical output of this optical receiver. A first filter is arranged in parallel and converts one component of the light incident on a predetermined position of both optical splitters into a predetermined wavelength, and the other component is converted into a wavelength different from that of the one component. 2. The measuring device according to claim 1, further comprising: a second filter for converting the signal, a first wavelength plate for converting the phase, and a reflecting mirror for reflecting the light. (8) The measuring device according to claim 2, wherein the first and second filters are narrow band filters having different wavelength ranges within the wavelength range of the light source. (4) A patent characterized in that the first and second filters are filters, with the center wavelength of the light source serving as a boundary, one of which passes through a wavelength range longer than the center wavelength, and the other filter which passes a wavelength range shorter than the center wavelength. A measuring device according to claim 2. (5) The measuring device according to claim 2, wherein the first and second filters are interference film filters deposited on predetermined surfaces of the analyzer. (6) The reflecting mirror is 3. The measuring device according to claim 2, wherein a metal is vapor-deposited on the analyzer.