Abstract

A number of interesting applications exist for the direct modulation of semiconductor lasers at frequencies ranging from 1 to 10 GHz. For example, analog microwave modulation could be employed in a low-loss optical fiber entrance link from an antenna to a receiver panel several kilometers away. Wideband telecommunications require pulse code modulation (PCM| at bit rates in the neighborhood of 2 Gbit/sec. For these applications, the on-off ratio must be >10:1 to avoid a significant power penalty. According to the sampling theorem, such a PCM signal requires an analog baseband width of at least 1 GHz, An additional requirement of the lasers Is that they oscillate at a single wavelength under modulation to avoid partition noise and material dispersion effects in the optical fiber, A third area of application is mode-locking of the laser to produce a uniform bit stream of narrow pulses at a fixed rate. Such a source would be useful as a synchronous clock in a high-speed computer or as one of several sources interleaved to serve as channels in a time-division multiplexed system.

© 1984 Optical Society of America