Abstract

Optical transmitters capable of efficiently transporting narrow-band millimeter-wave signals to and from fiber-fed antenna sites in applications such as indoor millimeter-wave wireless picocellular networks and phased-array systems are of considerable interest. Resonant modulation of monolithic semiconductor lasers in the vicinity of the round-trip cavity frequency is one several methods currently being explored. Recently, we demonstrated resonant modulation at 45 GHz by using a conventional low-frequency (direct modulation bandwidth <5 GHz) monolithic Fabry-Perot laser, and we showed that these devices can be used to build simple, efficient narrow-band optical transmitters at subcarrier frequencies up to 100 GHz.¹ These devices typically lase in many longitudinal modes and can limit the transmission distance to a few hundred meters.² Active mode locking of a semiconductor laser coupled to a grating external cavity was shown to provide single-longitudinal mode transmission at a carrier frequency of 35 GHz.³ In this paper, we demonstrate single-mode transmission of millimeterwave signals at 45 GHz by using a monolithic three-section tunable distributed-Bragg-reflector (DBR) laser. The modulation efficiency, passband bandwidth, noise and distortion of this device are fully characterized. The spur-free dynamic range at 45 GHz is higher than that of Fabry-Perot structures.² Furthermore, by simply adjusting the bias current into the phase-control and Bragg sections, fine adjustment of the modulation efficiency, passband bandwidth, and dynamic range is achieved.

© 1995 Optical Society of America