Passive Equalization of Semiconductor Diode Laser Frequency Modulation

摘要

Optical heterodyne communication systems using direct frequency modulated semiconductor diode lasers often exhibit system degradation because of the nonuniform injection current to frequency modulation (FM) transfer function present in most semiconductor diode lasers. In a frequency-shift-keyed (FSK) system, a nonuniform FM transfer function causes tone drift which results in increased crosstalk between tone slots and a corresponding degradation in system bit-error-rate (BER). Using simple passive electrical networks it is possible to equalize the nonuniform FM response and substantially reduce this transfer function induced BER degradation. The theory, computer optimization, construction, and test of various equalization networks and their use in realizing an FM equalized transmitter for a 100-Mbit/s binary FSK communication system is described. Reprints. (rh)