HIGH-PRECISION PLANAR WAVE-GUIDE PROPAGATION LOSS MEASUREMENT TECHNIQUE USING A FABRY-PEROT CAVITY

A high precision measurement technique for characterizing the propagat ion loss in silica low-loss optical waveguides, based on measuring the contrast of a Fabry-Perot cavity, is demonstrated. The cavity consist s of the waveguide coupled to two polarization-maintaining fibers, eac h end facet coated with dielectric mirrors, leaving the reflectivity a s an adjustable parameter. The contrast is measured by modulating the cavity length without influence on the waveguide characteristics and t he coupling efficiency. A double modulation of the cavity length reduc es the measurement uncertainty, and provides a measurement precision b etter than 0.1 dB, corresponding to 0.02 dB/cm in case of a 5 cm long waveguide.