Measuring device and method of polarization maintaining optical fibre Verdet constant

Abstract

The invention discloses a measuring device and a method of a polarization maintaining optical fibre Verdet constant. The measuring device mainly comprises a light source and isolation module, a polarization control injection module, a magnetic field and modulation module, a precision moving platform, a polarization beam splitter, a photoelectric detector, a signal processing module and a peak value detection module. A certain characteristic shaft of an optical fiber to be measured is coupled with a counter shaft of the polarization beam splitter at the exiting end. The measuring method comprises the following steps of changing light sent by a laser into circularly polarized light through the polarization control injection module and then outputting to the optical fiber to be measured, separating the light into two bundles of light through the polarization beam splitter, moving a guide rail to control the position of a magnetic filed, collecting two bundles of light intensity, conducting processing on the two bundles of the light intensity to obtain a corresponding voltage signal peak value, and further calculating a Verdet constant of the polarization maintaining optical fibre. The measuring device is simple and easy to operate, ensures maximum measured sensitivity, simultaneously avoids a measuring error caused by counter shaft operation and angle adjusting of the optical fiber injection end, and further improves measuring precision.

Description

technical field [0001] The invention relates to the technical field of improving the precision of a polarization-maintaining optical fiber gyroscope, in particular to a device and method for measuring a polarization-maintaining optical fiber Verdet constant. Background technique [0002] The fiber optic gyroscope is a high-precision sensor that uses the Sagnac effect to measure the angular velocity of an object. It is a new type of all-solid-state inertial device with simple structure, low cost, and high potential accuracy. It will be used in inertial navigation and strategic applications. The main instrumentation of the field. [0003] In the fiber optic gyroscope whose sensitive ring is a single-mode fiber, the birefringence effect introduced by factors such as the ellipticity of the fiber core and internal residual stress produces polarization phase errors in the Sagnac interferometer, resulting in zero drift and Signal fades. In order to reduce the polarization error i...

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Problems solved by technology

However, the residual birefringence of the fiber will introduce circularly polarized light, which cannot be separated from the Faraday rotation angle, which will bring a large error to the measurement

The residual line birefringence of ordinary single-mode fiber is small, and the detection signal can still reflect the influence of Faraday rotation angle. Due to the high birefringence characteristics of polarization-maintaining fiber, the phase difference α is much larger than the Faraday rotation angle θ F , for example the magnetic field strength is 5×10 5 At A / m, at a working distance of 1mm, α and θ F 0.6rad and 10 respectively -3 rad, high birefringence suppresses the rotation of linearly polarized light, so it is difficult to determine the Verdet constant by directly detecting the angle of rotation of the polarization plane of input linearly polarized light

[0007] The traditional method uses spatial optical coupling to measure the Verdet constant of the polarization-maintaining fiber. The basic principle is to measure the Faraday rotation angle under the action of a magnetic field. It needs a large magnetic field strength or needs to modulate the magnetic field at a certain frequency and supplement it with a coherent demodulation circuit

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