Angular displacement fiber-optic sensor: theoretical and experimental study

Abstract

An optical-fiber sensor based on twist-induced optical activity has been developed for measuring angular displacements at low temperature. The sensing part is composed of a fiber coil rotated between two points, which induces a twist of two sections of fiber. A theoretical study of the evolution of a general input state of polarization in the sensor gave us its main characteristics. Then experimental investigations permitted the construction of a sensor to take angular measurements over a 100-deg range with an accuracy of 0.2 deg. The thermal sensitivity of this kind of sensor is also briefly reported.

Fiber-Optic Sensors for Measurements of Torsion, Twist and Rotation: A Review

“…Measurement of the wavelength deepened Polarization Dependent Loss (PDL) around the FBG’s central wavelength revealed two distinctive spectral peaks in the PDL spectrum, with an amplitude ratio that was twist/rotation dependent. An interesting approach was presented in [11] where a fiber-loop was inserted in-between two fixed fiber points, while the loop plane was rotated around the fiber axis. These twisted fiber sections between the fixation points and the fiber loop and caused the appearance of circular birefringence proportional to the loop plane rotation angle, while the loop itself acted as linear birefringent retarder (due to the bend-induced linear birefringence).…”

High-resolution fibre-optic sensor for angular displacement measurements

“…Fibre-optic sensors offer the possibility of reducing strongly the part of the sensor which interacts with the mechanical system. The interaction can take place by a direct contact with the fibre [9][10][11]. Most of the times, these studies are based on fibres in which a Bragg grating was etched.…”