Dispersed image inverting optical wavelength multiplexer

Abstract

A method and apparatus for multiplexing and demultiplexing light signals of multiple wavelengths using two canceling dispersion stages with a stage between them which transforms the angular positions of the beams, the lateral positions of the beams, or both the angular and lateral positions of the beams. Light of multiple wavelengths is introduced through an input waveguide. The light then enters the first stage of the invention which disperses the signal. The dispersed signals then enter a second stage in which they are transformed. The transformed signals then enter a third stage where they are subject to the inverse of the dispersion performed in the first stage. In other words, if the third stage were placed immediately after the first stage, the third stage would nullify the dispersion of the first stage. However, adding the intervening transformation step results in only the simple linear dispersion being canceled in the system while the transformed part of the dispersion is retained. In specific examples of the invention, the intervening transformation step causes the resulting signals which are outputted from the third stage to remain coplanar with the input waveguide despite any displacement of the input waveguide in a direction orthogonal to both the direction of dispersion and the optical axis. This persistent alignment between the input and output waveguides reduces system performance degradation resulting from displacement caused by mechanical and thermal effects and also allows for multiple input/output combinations to be used consisting of stacked, linear arrays of fibers or waveguides.