Wavelength insensitive fiber optic sensor based on an axially strained fused coupler

A wavelength insensitive fiber optic strain sensor configuration is presented. It consists of two variable ratio couplers in series: a reference and a sensing element. Difference-over-sum processing yields linear outputs that are insensitive to fluctuations in optical intensity. By subtracting the reference from the sensor output, wavelength compensation is achieved. The wavelength properties of this sensor were determined experimentally and the results compared to computer simulations. Theoretical and experimental results show good agreement. The compensation technique is suitable for any variable ratio coupler sensor and is not limited to axially strained fused tapered couplers. (C) 1996 Society of Photo-Optical Instrumentation Engineers.