System and method for minimizing interferometric distortion in directly modulated analog fiber optic links

摘要

A method for minimizing the generation of interferometric intermodulation distortion in an analog fiber optic link that employs a directly modulated diode laser as its optical source. This is accomplished via the reduction of frequency chirp in the current-modulated diode laser source (32). To reduce frequency chirp, the diode laser (32) is coupled to an external reflector (52), so that an external laser cavity with a long, passive section is formed. Specifically, the frequency chirp of this extended laser cavity is reduced from that of the original diode laser by the ratio of the optical path length in the external cavity to that in the diode. The external reflector (52) can also be integrated, via splicing, to the fiber pigtail (54) of the laser transmitter (50) so that the compact geometric form factor of a diode transmitter is preserved.