Broad-band high-silica optical waveguide star coupler with asymmetric directional couplers

Abstract

A broad-band optical waveguide star coupler with asymmetric directional couplers is proposed. A coupling or splitting ratio of the coupler is flattened with respect to wavelength by choosing appropriate values for AD and complete power transfer length. Uniform and alternating Ap directional couplers are investigated theoretically and experimentally. A fabricated 8 x 8 star coupler exhibited 2-dB loss variation in the wavelength range of 1.3-1.55 pm, and this value was almost one fourth of that of a star coupler composed of symmetric directional couplers.