Evaluation of a High Sampling Rate Time-Domain Multiplexing Fiber-Optic Sensor System

Abstract

A fiber-optic system for continuous high sampling rate measurement of strain is presented in this paper. It is clear that many applications require a monitoring system with high sampling rate capability and the ability to multiplex many sensors. This has led to the definition and development of a time-domain multiplexed system for measurement of strain and temperature. The system concept is based on short-pulse interferometry and Bragg-grating reflective elements. Time-domain multiplexing is achieved by using an optical amplitude modulator, synchronized with the triggering of light pulses, as a switch to select the reflected pulses from a particular sensor. The sequentially queried sensors all have the same spectral characteristics, with the number of sensors being limited by the available light intensity, the reflectivity of the sensors and the sensitivity of the detection system. The current version of the optical system has a fast digital signal processor (DSP), which increases the attainable sampling rates in the order of 100kHz, divided among sensors. The dedicated DSP controls the system and performs all data reduction tasks autonomously in real-time, storing the results in its memory. The capabilities of this system are evaluated in the present work. A series of strain experiments, involving surface-attached sensors were conducted to evaluate the system performance. It was shown that the system was capable of measuring strains at high sampling rates as well as to determine operational loads at low frequency ranges.