Distributed active optical fiber sensor, for bending measurement

Abstract

A unique and very important feature of fiber-optic technology consists in its capability for long-range distributed sensing. The paper introduces a simple system based on a bendable large mode area (LMA) fiber, meant for a sensing accuracy of the microns order. The simulation shows that for a 1 m-3 m length of active fiber the 1 μm difference in fiber bending radius is quite well discerned. A power variation of the fundamental mode in excess of 10 μW (-20 dBm) up to 48μW has been obtained. The signal was in L and C band (typical for wavelength division and multiplexing- WDM systems) and the pump wavelength 980nm (lower noise) or 1480 nm (optimizes the output power but higher noise), also typical for telecommunication links. The performance is optimized by varying the bending radius, index/ doping profile, and the LMA fiber core diameter. © 2011 Springer-Verlag.