Abstract
Optical transmitters capable of efficiently transporting several millimeter-wave (mm-wave) subcarriers to fiber-fed antenna sites for indoor mm-wave mobile wireless networks and wireless cable-television systems are of considerable interest.12 Future deployment of a fiber infrastructure in these systems rests primarily on the availability of low-cost mm-wave optical transmitters. Recently, optical transmission of a single narrow-band channel at 45 GHz was demonstrated by using resonant modulation for a conventional low-frequency (direct modulation bandwidth <5 GHz) monolithic semiconductor laser.3 It was shown that this technique provides a means of building simple, low-cost narrow-band mm-wave optical transmitters for frequencies approaching 100 GHz. In this paper we ascertain the multichannel analog and digital performances of these transmitters at 41 GHz. Two-tone dynamic range is characterized in detail as a function of bias to the laser, and a maximum dynamic range of 66 dB·Hz2/3 is obtained. Although this is modest by conventional measures, it is adequate for serving a typical indoor picocell with a 40-dB variation in received rf power and a per-user voice-channel bandwidth of 30 kHz. A multichannel-system implementation of resonant modulation, in which two signals centered around 41 GHz and operating at 2.5 Mbit/s BPSK are transmitted over 400 m of optical fiber, is also presented. The required rf drive power to the laser to achieve a bit error rate (BER) of 10−9 for both channels transmitting simultaneously is measured to be <5 dBm per channel. On the basis of these transmission results and by taking advantage of conventional wireless time-division-multiplexing techniques in which as many as eight users can share a single channel,4 these mm-wave links are adequate in remoting signals from an antenna serving as many as 16 mobile users.
© 1995 Optical Society of America
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