Interfaces for High-Speed Fiber-Optic Links: Analysis and Experiment

Abstract

An analysis of directly and externally modulated fiberoptic links is presented here. The theoretical analysis is based on the signal flow diagram of the interface circuits to the laser diode, Mach—Zehnder electro-optic modulator p-i-n photodiode. System parameters such as gain, noise figure, two-tone intermodulation distortion spurious free and compression dynamic range are expressed as a function of frequency and operating point of the laser and external modulator. Two di-rectly and externally modulated fiber-optic links were designed and fabricated to verify the analytical models. The direct modu-lation FO link was developed at the Ku-band (11.6-12A GHz), whereas the external modulation link was at L-band (875–925 MHz). Spurious-free dynamic ranges of 95.8 dB.Hz 2/3 and 113 dB.Hz 2/3, respectively, were achieved, the best reported to date for these frequency bands. The predictions based on the analyti-cal models match the measured results very well. © 1991 IEEE