Interferometric fibre grating characterisation

One of the most important fibre-optic devices to have emerged in the recent years is the fibre grating. It finds applications in DFB and DBR fibre lasers, dispersion compensation and fibre sensors. Full and accurate amplitude and phase (dispersion) characterization of this device is therefore needed. We have demonstrated such a system based on an interferometric technique (figure 1). The signal arm of a fibre Michelson interferometer is phase-modulated with a saw-tooth function to generate an electric signal at the photodetector which carries the optical phase and amplitude information of the reflective fibre device under test (DUT). The amplitude response of the interferometer is directly proportional to the field reflection coefficient, whereas the measured relative phase is related to the time delay response of the device. The set-up is fully automated and uses a Hewlett Packard tunable laser source (1470-1560nm) with wavelength accuracy are high resonance piezoelectric ceramic cylinders which are wrapped round with some turns of fibre