A simple method for fabricating phase-shifted fibre Bragg gratingswith flexible choice of centre wavelength

摘要

A simple technique for fabricating phase-shifted fibre Bragg gratings (PSFBGs)without the use of a phase-shifted phase mask is presented. Two, 3-mm long,standard fibre Bragg gratings (FBGs) were inscribed sequentially in singlemodefibre at the same Bragg wavelength such that the FBGs physically overlapped byone grating period. This induces a spectral-hole in the middle of the reflectionspectrum of a standard FBG, equivalent to a π-phase shifted FBG. The flexibilityof the technique in writing PSFBGs at any choice of wavelength is demonstrated.The results show that PSFBG devices produced by this method are highlyreproducible and the process is fast