Crosstalk Analysis in Planner Waveguide Couplers

Directional couplers are very important devices in integrated optics and could well be the only device necessary for most integrated optics chips. When light is launched into an input waveguide of directional coupler, one would like to get all the power from one of the two output waveguides. Whereas it is generally observed that small amount of power does go to the other guide, causing undesirable crosstalk. This phenomenon gets worst in WDM systems as at each wavelength coupling, length vary and so is the output. Crosstalk is an important figure of merit for a directional coupler. The crosstalk is attributed to many reasons like asymmetry of the waveguides, absorption loss, bending losses etc. This paper also deals with the directional couplers with special emphasis on measurement of their response over a wide frequency range. It also includes the simulation of the coupler response and comparisons with the tested results