Design and performance optimization of fiber optic adaptive filters

Adaptive optoelectronic signal processor with metal-semiconductor-metal photodetector arrays

Optoelectronic structures utilizing switched fiber delays and switched metal-semiconductor-metal photodetectors for signal processing over a 1.25-GHz bandwidth are presented. Fully tunable finite-impulse-response and infinite-impulse-response structures were synthesized with internal compensation for bias dependency of photodetectors. The application of such filter structures to the equalization of modal dispersion in a multimode fiber is also described.

Design and performance analysis of fiber-optic infinite-impulse response filters

Design of direct forms of infinite-impulse response digital filters using radiatively tapped fiber-optic delay lines is discussed. Infinite-impulse response filters are attractive because they can provide better magnitude characteristics and sharp transition bands in their frequency response for a smaller number of taps than finite-impulse response filters can. The designs described here use spatial-light modulators and thus can be incorporated into optical adaptive filters for processing light-wave signals. Models of error sources in the fiber-optical realization and their effects on both time- and frequency-response characteristics are explained. Cascading of lower-order subsystems to obtain higher-order filters is discussed. A possible way of reducing the insertion loss using erbium-doped fiber-optic amplifiers is derived.