Automatable fabrication of dispersion-tailored Bragg gratings for tunable narrowband delays

An automatable fabrication technique for fibre Bragg gratings is described, the reflection spectra of which contain regions of highly tailored group delay. The proposed method allows simulated dispersion characteristics of compound phase-shifted gratings to be achieved in practice through active monitoring of reflective group delay during tuning of the index modulation strength. Using the proposed technique, the laboratory fabrication of a dual phase-shifted grating that exhibits enhanced reflective group delay as a result of resonance superposition is demonstrated.