Optical Sources for Coherent Optical Fiber Communication Systems

Abstract

This paper reports recent progress in the development of three categories of optical sources with linewidths, Ay, sufficiently narrow to be used in heterodyne and homodyne optical fiber communication systems: First, single-longitudinal-mode semiconductor lasers with relatively broad linewidths of several tens of MHz, suitable for amplitude-shift-keying and frequency-shift-keying heterodyne with envelope detection. Second, semi-conductor lasers with weak optical feedback having Lv = 1 MHz. Such narrow linewidth sources would be required for differential-phase-shift-keying heterodyne detection. Third, semiconductor lasers with strong optical feedback, and 1523 nm He-Ne lasers, both having Av , ▵ν≤15kHz ,Such very narrow linewidth sources would be required for PSK homodyne detection.