Abstract

A nondestructive optical path tracing method for guided-wave optical devices is proposed, which has been successfully used in evaluating guided-wave multi/demultiplexer performance for optical frequency-division-multiplexing (FDM) transmission. When a testing light is injected into one of the two input ports of a multi/demultiplexer having a Mach-Zehnder interferometer configuration, each output light from the two output ports contains two mixed components, one from the upper branch and the other from the lower branch of the interferometer. This makes waveguide parameter measurements difficult. We overcome this difficulty by utilizing the light source's coherence length finiteness. The ratios of the two mixed optical power components traveling along the two different paths can be determined by using the spatial interferometric technique with a heterodyne power detection scheme.¹ The power coupling coefficients at the two branching points are thus nondestructively determined from the measured power ratios.

© 1987 Optical Society of America