OPTICAL MULTIPLEXER/DEMULTIPLEXERS USING THIN-FILM OPTICAL FILTERS.

Designs and characteristics of optical multiplexer/demultiplexers (MDMUXs) and their thin-film filters and lenses are described. Properties of thin-film filters, lenses and light spectrum are discussed in relation to insertion loss, crosstalk loss and interchannel spacing. The most important component of the MDMUX described in this paper is the thin-film optical filter. Optical filters of less than 0. 2 db transmission loss were designed by varying layer thickness. The edge steepness of the filter, which is the wavelength difference between 1 db and 20 db transmission loss at wavelengths around 1 mu m, is about 400 A for a 35 layer TiO//2-SiO//2 filter. Two- and four-channel MDMUXs of double mirror configuration were made. Their insertion losses were 2. 0-2. 3 db and 1. 0-4. 3 db, respectively. The crosstalk losses of both MDMUXs were larger than 30 db.