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Proceedings Paper

Integrated CMOS transceiver for indoor optical wireless links
Author(s): David M. Holburn; Vinod A. Lalithambika; Valencia M. Joyner; Rina J. Samsudin; Robert J. Mears
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Paper Abstract

The purpose of this work is to develop integrated CMOS designs for optical transceivers at 1.55um wavelength that both meet the current system specification of 155Mb/s and provide a viable upgrade path to higher bit-rates. We present the design and implementation of an integrated multi-channel CMOS transceiver for use in a cellular 155Mb/s Manchester-coded optical wireless link. The receiver is an angle-diversity design and consists of multiple sectors with relatively small field of view; each driving an individual pre-amplifier channel. An on-chip selector selects signals to be passed to the combiner depending on the signal level and external control signals. The outputs of all the selected channels are combined using a current summing junction, implemented using a transconductance-transimpedance approach. In order to achieve a receiver design that will be robust in the face of process variations, an on-chip circuit is provided to maintain the operating point of the amplifier chain. The design has been optimized to achieve -30dBm sensitivity at a BER of 10-9. The CMOS transmitter circuit is tailored to match the electro-optic response of the resonant cavity LEDs being used. The transmitter driver incorporates current-peaking and charge-extraction circuitry using a novel timing generator, and has been designed to achieve rise and fall times of better than 0.2ns. Considerable effort is being directed towards the development of integrated designs which do not require significant numbers of discrete components. The prototype designs are being realised in a 0.7μm commodity mixed-signal CMOS process by Alcatel Microelectronics. We report results from the first prototype multi-channel demonstrator system and discuss future research directions.

Paper Details

Date Published: 27 November 2001
PDF: 6 pages
Proc. SPIE 4530, Optical Wireless Communications IV, (27 November 2001); doi: 10.1117/12.449806
Show Author Affiliations
David M. Holburn, Univ. of Cambridge (United Kingdom)
Vinod A. Lalithambika, Univ. of Cambridge (United Kingdom)
Valencia M. Joyner, Univ. of Cambridge (United Kingdom)
Rina J. Samsudin, Univ. of Cambridge (United Kingdom)
Robert J. Mears, Univ. of Cambridge (United Kingdom)

Published in SPIE Proceedings Vol. 4530:
Optical Wireless Communications IV
Eric J. Korevaar, Editor(s)

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