Ultra narrow-band optical fibre sidetap filters

We present a new fibre structure for use in sidetap filters for telecommunications applications with low insertion loss due to splices and bends and a filter FWHM bandwidth of only 3.4 nm. The aim of our research in this area has been to find fibre and grating designs yielding very narrow filter responses while maintaining low backreflection by the appropriate choice of blaze angle, and low insertion loss due to splices and bends by the appropriate choice of index profile.