JPS5972005A - Light interference type optical fiber sensor - Google Patents

Abstract

PURPOSE:To realize simple constitution by generating light incident to an optical fiber and regarding its reflected light from a semitransparent mirror as reference light and light which is transmitted through the semitransparent mirror and reflected by the reflecting mirror of an optical fiber for a sensor as signal light, and detecting interference between both lights. CONSTITUTION:Laser projection light from a laser light source 1 is passed through a beam splitter (BS) 2 and an optical fiber 3, and the light reflected by the semitransparent mirror 5 is incident to a photodetector 8 by a BS2 as the reference light. The light transmitted through the semitransparent mirror 5 is passed through the optical fiber for the sensor which is stored in a hollow container 9 and reflected by the reflecting mirror 7 to enter the photodetector 8 as the signal light through the BS2. The reference light and signal light interfere with each other and temperature variation of the optical fiber 6 for the sensor is detected as a phase shift of interference light. Consequently, the constitution of an optical fiber interferometer is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides various physical quantities (for example, temperature, pressure, sound waves,
The present invention relates to an original fiber sensor that utilizes an optical interference boundary plate used as a sensor for vibration, electric field, e&field, etc.).

, As an optical interference type fiber sensor using original fiber,
Soba Tsuender, which has long been known in the field of optics.
There are various types of spring light interferometers, such as type, Michelson type, and Fuchipre-Bello type.

Among these, a sensor using a Matsuhatsu-ender type interferometer and a Michelson type interferometer requires two fiber arms, a reference fiber and a signal light fiber, which has the drawback of complicating the configuration of the sensor. In addition, the edge-ply bellows type does not require a reference beam arm and only has a single 7
Although it is possible to use an optical fiber arm, it is said that it is not suitable for remote measurement because the source of the light input to the fiber arm and the observation point where the receiver is placed are dispersed at the opposite ends of the fiber arm. 〇Object of the present inventionVi To solve the above-mentioned drawbacks of the conventional original 7-source interferometer, we have developed a simple light source and a light receiver arranged at the same end of one original fiber arm. Our objective is to provide a full range of interferometric fiber sensors suitable for remote sensing.

According to the present invention, a light source, a source fiber for transmission into which photons from the light source are incident on one end, a sensor body fiber having a reflecting mirror at one end, and the other ends of the optical fiber for transmission and the source fiber for seven sensors. Of the incident light that enters the semi-transparent mirror located between and the source fiber for transmission, the light that is reflected by the semi-transparent theory? As a reference source, it is transmitted through a semi-transparent mirror, guided into the sensor moonlight fiber, reflected by a reflecting mirror installed on the other end of the sensor body fiber, completely transmitted through the semi-transparent mirror again, and guided to the source fiber for transmission. An original interference type original fiber sensor is characterized in that it measures a physical quantity at a location where a sensor optical fiber is installed, and includes means for detecting optical interference between these reference sources and the signal light. can get.

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram for explaining the basic configuration of the present invention. In the figure, laser light emitted from a laser light source 1 passes through a beam splitter 2 and enters a source fiber 3 that forms the source transmission section of the interferometer. A part of the original light incident on the original fiber 3 is reflected by the semi-transparent mirror 5, returns within the fiber 3, and is guided by the beam splitter 2 to the light receiver 8 as a reference source. -The light that has completely passed through the semi-transparent mirror 5 is propagated within the source fiber 6 which is coupled to the source fiber 3 for transmission by the connector 4 without the sensor portion of the interferometer. The original fiber 6 constitutes a sensor section for interference cutting, and a reflecting mirror 7 is located at its tip. The yt propagated through the sensor fiber is reflected by the reflector 7, but it is not affected by various physical stimuli (for example, temperature, EE force, waves, vibrations, etc.) applied to the original fiber 6 from the outside world.

The signal light has its original path length and polarization plane changed depending on the magnetic field (magnetic field, etc.). This signal light exits the semi-transparent mirror 5 and is again guided to the original transmission fiber 3, guided to a light receiver 81C by a beam splitter 2VC, and combined with the reference light. As a result of the interference between the signal light and the
The physical quantity applied to the sensor body fiber 6 is detected as an electrical signal.

FIG. 2 is a cross-sectional view showing the Onho sensor, which is an embodiment of the invention. The optical length of the sensor body fiber 6 changes with the temperature of the fiber, which causes a change in the phase of the signal light propagating through the sensor body fiber 6, which overlaps with the reference source and interferes with it, thereby increasing the temperature. 0 detected
Since both the signal light and the reference light undergo the same phase change in response to a temperature change in the transmission source fiber 3, only the temperature of the sensor body fiber 6 is measured without affecting the measurement. In addition, the sensor body fiber 6 is housed in a protective hollow container 9 to eliminate the influence of external forces such as bending. In Figure 0, which is a diagram for explanation, 10 is a liquid serving as a medium for sound waves, and 11 is a container thereof.The source fiber 6 for seven sensors receives the sound waves generated by the sound generating element 12 as a sound source. The optical length of the fiber changes, and the signal light that has undergone a phase change is sent to the transmission fiber 3, overlapped with the reference source, and interfered, whereby a sound wave is detected.

FIG. 4 r1 is a diagram for explaining a current sensor which is another embodiment of the present invention. In the figure, the current to be measured is a solenoid-shaped electric current It
The polarization plane of the light wave (signal light) propagating through the sensor body fiber 6 rotates due to the Faraday effect caused by the magnetic field generated by the current. The rotation of the polarization plane of this signal light is detected as a difference in the direction of the polarization plane relative to the polarization plane of the reference source, and as a result, the t current flowing through the electric wire 13 is measured.

As is clear from the above description, the present invention has a simpler configuration than conventional optical fiber interferometers, and the reference source and the signal light propagated through the sensor body fiber are used for the same transmission. An optical interference type optical fiber sensor that is resistant to changes in the surrounding environment other than the measurement target because it is guided into the original fiber, and has extremely high sensitivity because it uses the original interference phenomenon, and is suitable for remote measurement. has become possible, and its practical effects are extremely significant.

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[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the basic configuration of the present invention. FIG. 2 Vi is a diagram for fully explaining the temperature sensor which is one embodiment of the present invention, FIG. 3 is a diagram fully explaining the acoustic sensor which is another embodiment of the present invention, and FIG. It is a figure for explaining the current sensor which is another example of the invention. ■... Laser light source, 2... Beam grip, 3... Source fiber for transmission, 4...
...Connector, 5...Semi-transparent mirror, 6...
Sensor moonlight fiber, 7...Reflector, 8...
...Receiver, 9...Protective hollow container, 10.
...acoustic medium (liquid), 11...container,
12... Sound generating element, 13... Electric wire. 2nd ward 83 sen 84 fig.

Claims (1)

[Claims] a transmission optical fiber, a light source that generates a principal input to one end of the transmission body fiber, a semi-transparent mirror located at the other end of the transmission light 7 taber, one end facing the semi-transparent mirror and the other end facing the transmission optical fiber; Interference between a sensor optical fiber having a reflecting mirror and the light incident on the transmission trunk fiber that is reflected by the front semi-transparent mirror and the light that is completely transmitted through the semi-transparent mirror and travels all the way back and forth through the seven sensor fibers. 1. An optical interference type optical fiber sensor, characterized in that the optical fiber sensor comprises a means for detecting the following: and measures all physical quantities at a location where the sensor optical fiber is installed based on changes in the front g-p interference state.