<title>TDM of FBG sensors by use of a tunable laser source</title>

Abstract

The results of an investigation of the performance of a TDM FBG sensor array using a tunable laser source are reported. The system performance is found to be limited by the extinction ratio of the optical pulse modulator used for pulse amplitude modulation. Formulas that relate the crosstalk to the extinction ratio of the optical pulse modulator, the modulation parameters of the tunable laser, and the optical path differences among sensing channels are derived. Computer simulation shows that an array of 20 FBG sensors with 3 (mu) (epsilon) resolution can be realized with a commercially available single Mach-Zehnder type optical pulse modulator of -35 dB extinction ratio. Experiments with a 4-FBG sensor array demonstrated a strain resolution of about 3.98 (mu) (epsilon) with an optical pulse modulator of about -24 dB extinction ratio.