Abstract

Recently there has been growing interest in wavelength multiplexed (WDM) fiber optic networks using tunable optical bandpass filters as wavelength demultiplexers. This talk reviews various schemes of guided-wave narrowband wavelength filters for multichannel WDM communication networks. High finesse fiber optic Fabry-Perot resonators have been demonstrated with bandwidths of 10-100 MHz and tuning ranges of 1-10 GHz, thus allowing continuous tuning over 10-100 wavelength channels. Comparable results have been obtained with electrooptic and acoustooptic TE ↔ TM mode converters in LiNbO₃ waveguides, where bandwidths of 100 GHz and tuning ranges of 2 and 40 THz, respectively, have been achieved. Narrowband wavelength filtering with simultaneous optical gain has been obtained via stimulated Brillouin amplification in optical fibers (20-100-MHz bandwidth) as well as with tunable distributed feedback (DFB) or distributed Bragg reflector (DBR) lasers driven just below threshold (12-GHz bandwidth, 120-GHz tuning range). Moreover, these resonant DFB and DBR amplifiers can simultaneously act as photodetectors, thus combining filtering, amplification, and detection in a single device. Cascaded two-mode interferometers, such as fiber optic and integrated Mach-Zehnder interferometers or zero-gap directional couplers, can serve as efficient multiplexers/demultiplexers in point-to-point WDM transmission systems.

© 1989 Optical Society of America