Pierre Tihon

Development of a multi-point polarization-based vibration sensor

In this paper we propose a novel kind of multi-point vibration sensor based on the polarization properties of light. Its principle relies on the combination of mechanical transducers with fiber Bragg gratings. When subject to vibrations, the mechanical transducers induce birefringence variations within the fiber and in turn modify the state of polarization, which appears as a power variation after going through a polarizer. The FBGs reflect light from different positions of the sensing fiber and provide wavelength multiplexing. We show that this sensor can provide the vibration frequencies in a quasi-distributed manner.

Temperature-insensitive polarimetric vibration sensor based on HiBi microstructured optical fiber

A new type of highly birefringent microstructured optical fiber has been tested for vibration measurements using a polarimetric technique. This technique takes advantage of the stress-induced phase shift between the two orthogonally polarized fiber eigenmodes. Comparison of three different fiber types shows that standard single-mode fibers do not provide stable measurements and that conventional polarization-maintaining fibers lead to a significant cross-sensitivity to temperature. However, for highly birefringent microstructured fibers specifically designed to provide a temperature-independent birefringence, our experiments show repeatable vibration measurements over a frequency range extending from 50 Hz to 1 kHz that are unaffected by temperature variations (up to 120 °C).

Linearity considerations in polarization-based vibration sensors.

In this paper, the characteristics of a polarization-based vibration sensor are theoretically and experimentally analyzed with a focus on its sensitivity and linearity. It is shown that this sensor can correctly recover the vibration frequency spectrum (i.e., with limited distortions) up to an acceleration of 140 m/s(2), with a sensitivity equal to 9.98 mV/(m/s(2)).

Quasi-distributed vibration sensor based on polarization-sensitive measurement

In this paper we propose a novel kind of quasi-distributed vibration sensor based on the measurement of the polarization state of light. Its principle is based on the combination of mechanical transducers -which transform the mechanical perturbation into a birefringence variation- with fiber Bragg gratings. We show that several vibrations can be detected and localized at each transducer position with a frequency resolution of 1.25 Hz.

Design of an Optical-Fiber Accelerometer Based on Polarization Variation Due to Crushing of the Fiber

This paper presents the design of a novel kind of accelerometer. The sensor is based on the modification of the polarization state of the light inside the fiber by the means of a mechanical transducer. The transducer presented uses crushing to deform the fiber. Measurements were done with an acceleration varying from 1 to 40 m/s² and a frequency range varying from 100 to 1,000 Hz. The measured output is the ratio between the variable part and the constant part of the optical power at the end of the fiber. A sensitivity of the order of 6E-4/ms² was found. Numerical simulations were also performed with the Abaqus software. The obtained sensitivity is quite greater than the measured one which can be explained by the hypothesizes we made for the simulations.

Real-time measurement of dynamic accelerations with optical-fiber accelerometer based on polarization analysis

This paper presents a novel technique for the measurement of accelerations using an optical-fiber accelerometer based on the analysis of polarization variations. The technique relies on the identification of six parameters of the fiber Mueller matrix through polarimetric measurements. We demonstrate by theoretical and experimental work that the sensitivity of the proposed method does not depend on the input polarization states sent into the fiber nor on the intrinsic fiber birefringence. The sensor has been successfully tested for acceleration amplitudes between 2.5 and 20  m/s² at a frequency of 120 Hz. The acceleration resolution increases from 0.1  m/s² around an acceleration of 2.5  m/s² to 0.35  m/s² around 20  m/s². The acceleration measurements can be performed every 160 μs.

Design of a mechanical transducer for an optical fiber accelerometer based on polarization variation

This paper presents the design of a mechanical transducer for an optical-fiber accelerometer based on polarization variation. Several transducers can be imagined using either bending, twist, stretching or crushing of the fiber. The transducers are modelled analytically and are compared through the curve representing the sensitivity in function of the sensor resonant frequency. It turns out that the use of crushing shows a sensitivity several orders of magnitude higher than the other deformations. In this latter case, experimental results confirm the analytical computation of the sensitivity.

A new measurement technique for polarization-based optical-fiber accelerometers

This article presents a measurement technique for a polarization-based optical fiber accelerometer. Different optical measurements are combined to have an acceleration measurement. The technique ensures that the sensor sensitivity does not depend on the input polarization states. Experimental results are performed to validate the technique. A stable sensitivity of 1 rad/(m/s2) is achieved.

Study of the Linearity Performances of a Polarization-Based Vibration Sensor

In this paper the performances of a polarimetric vibration sensor are theoretically and experimentally analyzed. We show that this sensor can recover the vibration spectrum without distortions up to an acceleration of 300 m/s^2.

Development of a polarimetric vibration sensor for quasi-distributed measurements

In this paper we propose a novel kind of quasi-distributed polarimetric vibration sensor. Its functioning is based on the use of mechanical transducers, which transform the mechanical vibration into a birefringence variation, and of fiber Bragg gratings (FBGs), which reflect light from different positions. As it will be shown this sensor can provide the vibration frequency in a quasi-distributed manner.