SU1315797A1 - Fibre-optic transducer - Google Patents

Abstract

The invention relates to a measurement technique and can be used in optical interferometry to record small acoustic signals, deformations and temperatures. The aim of the invention is to increase the sensitivity of the sensor by eliminating the influence of parasitic birefringent optical fibers. The radiation from a light source 1, for example a laser, passes through a linear polarizer 2 and is divided by the beam splitter 3 into two beams of the same intensity. The beams propagate in the optical fibers 4 and 5, passing at the end of each of the optical fibers through the Farad cells 11 and 12, respectively. After reflection from the reflectors 6 and 7, the beams pass for the second time through the cells 11 and 12, and after they are combined on the beam splitter, 3 parts of the radiation fall on the receivers 13 and 14 of the radiation. In this case, radiation arrives at the inputs of receivers 13 and 14, in which the parasitic change in polarization is compensated. In the processing and display circuit 13, signals are converted from receivers 13 and 14. 1 3.p. f-ly, 1 ill. about SAE in SS

Description

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The invention relates to a measurement technique and can be used in optical interferometry for detecting small acoustic signals, deformations and temperatures.

The purpose of the invention is to increase the sensitivity by eliminating the influence of the parasitic birefringence of optical fibers.

The drawing shows a diagram of a fiber optic sensor.

The sensor contains a light source 1 located along the course of the radiation polarizer 2, a Michelson interferometer consisting of a beam splitter 3, two optical fibers 4 and 5 forming the two arms of the interferometer, two reflectors 6 and 7 installed in each of the arms of the interferometer , phase modulator 8 placed in one of the arms of the interferometer, sound generator 9, the output of which is electrically connected to the input of the modulator 8, processing and recording unit 10, two inputs of which are optically connected to the output ends of optical fibers 4 and 5, and the third electric The bushes are connected to the output of the generator 9, two Farad cells 11 and 12, each of which is installed in one of the interferometer arms in front of the reflectors 6 and 7. The Farade cells 11 and I2 are made in one of the possible variants in the form of a coil (not shown) of an electromagnet direct current with coils of the light guide 4 and 5 wound on it in such a way that they are arranged perpendicular to the turns of the coil, and the light guide is made of paramagnetic or ferromagnetic materials.

The processing and recording unit 10 comprises two radiation receivers 13 and 14 and a processing and display circuit 15.

The device works as follows.

Radiation from a light source 1, such as a laser, passes through a linear polarizer 2. Linearly polarized radiation with the help (fiber splitter 3 is divided into two beams of the same intensity that propagate in fibers 4 and 5. Light guide 4 is placed in the medium under study and it is influenced by a measurable value, such as an acoustic field or temperature.

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the medium has no effect, but its optical length varies sinusoidally under the influence of the modulator 8. At the end of the optical fibers 4 and 5

the beams pass through the Farad cells 11 and 12, are reflected from the mirror reflectors 6 and 7, and pass through cells 11 and 12 a second time in the opposite direction. After folding beams

on the beam splitter 3, part of the radiation hits the receiver 13, and part goes to the receiver 14. Due to the interference of the beams in the beam splitter, 3 phases of the signals at the output of the receivers 13 and

14 differ on IT. In the processing and display circuit 15, these signals are sent to a differential amplifier with a synchronous detector, from which output a signal proportional to

the measured value is converted to a digital code and visually displayed by display elements. Under the influence of external conditions due to parasitic anisotropy in the material of optical fibers 4 and 5, a parasitic change occurs both in ellipticity and in the azimuth of polarization. As a result of the passage of the beams in each of the optical fibers through the Farad cell in the forward and after reflection from the isotropic mirror in the opposite direction, the parasitic polarization change is compensated, and the resulting polarization of the output radiation of the optical fibers

Lip is experiencing rotation of the polarization plane on IT / 2.

Claims (2)

Invention Formula  Fiber optic sensor, containing a light source, a Michelson interferometer, consisting of a beam splitter, two fiber light guides forming the two arms of the interferometer, two reflectors installed in each of the arms of the interferometer, and a phase modulator placed in one of the arms of the interferometer, sound generator whose output is electrically electrically connected to the modulator input, and the processing and recording unit, whose two inputs are optically coupled to the output ends of the optical fibers, and the third electrically connected to the generator output, characterized in that Strongly povsch1eni sensitivity, it is provided with a polarizer, mounted between the light source and the interferometer, and two cells 3 13157974 Farad, each of which is a direct current electromagnet with naked in one of the arms of the interferometer windings of a light guide wound on it in front of the reflector. so that they are located 2. The sensor according to claim 1, which is perpendicular to the turns of the coil, and u and with the fact that each cell the light guide is made of paramagnetic Farad is made. In the form of a coil or ferromagnetic materials.