Strain related characteristics of composite cavity fibre lasers

Abstract

A novel composite cavity fibre laser (CCFL) design is being investigated for its use in sensing applications. A CCFL can be fabricated simply by writing three spectrally matched Bragg gratings directly into a continuous length of doped fibre. When strained evenly, so that the strain experienced by both cavities are the same, the strain response of the CCFL is expected to be similar to that of a FBG or single cavity fibre laser sensor. However, if the internal cavities are strained unevenly, simulations derived from theoretical analysis suggest that the wavelength-encoded and intensity-encoded sensitivities can become significantly different from that of a typical single cavity fibre laser. A 3cm/9cm CCFL was tested using three different straining formats, and results agree well with theoretical expectations.