High-resolution fibre-optic sensor for angular displacement measurements

Abstract

The design of a fibre-optic sensor able to measure high-precision angular displacements is presented. The sensor has a small size which allows easy integration in miniature mechanical systems. Two configurations are designed: lens-free configuration and GRIN micro-lens configuration for which the micro-lens is fixed on the tip of the probe. The experimental results obtained by the angular displacement sensor based on the lens-free configuration are compared with the simulation results based on the modelling of the system and a good agreement is found. Then, a long-range measurement technique is described. In the 'lens-free and long-range configuration', the limit of resolution is measured (2 × 10 −3•) or calculated (4.8 × 10 −4•) over a range of [−23.4 • , +23.4 • ]. In the 'GRIN lens and long-range configuration', the best limit of resolution is decreased to 2.2 × 10 −4• but over a smaller range of [-14.5 • , +14.5 • ]. Finally, the sensor in its 'lens-free configuration' design is integrated into a miniature electromagnetic actuator to determine its stroke by a comparison of the output signal obtained between this unknown-stroke actuator and a rotating stage for which the stroke was precisely known.

Ultrasensitive vector bending sensor based on multicore optical fiber

“…Some interferometric bending sensors [13][14][15][16] that have been proposed until now are highly sensitive, but they tend to be more complex. Other bending sensors based a conventional fibers codify the bending angle on intensity measurements [17][18][19]. The disadvantage in this case is the need of compensation mechanisms and the impossibility to distinguish the bending orientation.…”

Photonic crystal fiber interferometric vector bending sensor

“…To achieve such features, the optical fiber sensor community has proposed a number of sensing architectures. Most of them are based on Bragg gratings [1][2][3][4][5], long-period gratings (LPGs) [6][7][8][9][10][11][12], interferometers [13][14][15][16][17][18][19], or on intensity measurements involving optical fibers [20][21][22][23].…”

“…The disadvantage of some interferometric bending sensors is their complexity as they require several components that must be precisely aligned [16]. On the other hand, bending sensors based on intensity measurements require a mechanism to compensate fluctuations of the light source or attenuation losses [20][21][22][23].…”

Theoretical and experimental study on intensity modulation differential optical fiber angular displacement sensor

“…Angular displacement detection has important significance in the applications of civil constructions, industrial production process control, instrument development, and kinematics of robot 1‐3 . In all of these application fields, high sensitive, robust, low cost, and compact angular displacement sensors are needed 4 .…”