Optical Fibre Bending Sensor With Automatic Intensity Compensation

Abstract

An extrinsic optical fibre bending sensor based on intensity modulation technique aimed for physiological application is presented. This sensing technique is capable of measuring the bending angle continuously in flexion, extension and lateral movements. The sensor working range is between −22°and 22°with 0.4°accuracy and 0.1°resolution. From the theoretical estimation, the bending sensor automatically compensates for variation in the source intensity and various losses in the input and output fibres. The experimental results obtained in this investigation verified the theoretical finding. Among the advantages of the this optical bending sensor are being noninvasive, suitable for continuous measurement and immune from electromagnetic effects.Index Terms-Bending sensor, health monitoring, intensitymodulation sensor, optical fibre sensor.

An Extrinsic Optical Fiber Bending Sensor: A Theoretical Investigation and Validation

“…core radius, a = 0.49; gap, l = 0.5 mm; NA/no = 0.5, and centralized input-output fibre arrangement (x 1 = 0.289 mm; x 3 = 0.577 mm). Due to the scope limitation and the objective of this article, the experimental procedure is not covered here and it is available in [20]. The typical range of motion of human lumbar spine is presented in Table II [30], which serves as the reference for the accuracy and working range of the proposed sensor.…”

“…In this work, the proposed extrinsic optical fibre bending sensor was placed on a self-made bending apparatus [20] and cross-checked with a two-arm goniometer. However, for actual spine measurement on human subjects, various approaches can be implemented as reported by L. Dziuda [19], such as via belts, special garment, at the back of a chair, under the bed, pneumatic cushion or directly affixed to the body.…”

“…This sensor uses a single input fibre and three output fibres, being separated at a predetermined gap. A theoretical representation of the output ratio for bending angle measurement is briefly discussed here and the details are provided in our previous report [20]. In terms of the novelty of this article as compared to our previous work, the effects of the involved parameters, i.e.…”

“…The fibre gap factor has been discussed in our previous work [20], but it is highlighted here to show the overall effects of all contributing parameters for the proposed compensation technique aimed for bending sensor application. The gap range used for the theoretical estimation is between 0.2 and 1.2 mm.…”

Compact and Low-Cost Optical Fiber Respiratory Monitoring Sensor Based on Intensity Interrogation

“…A sensor based on a similar concept has been previously described for the measurement of back (spine) bending [12]. The sensor comprises a POF, a light emitting diode (LED) as the light source and an electronic circuit that consists of a photodetector and amplifier.…”