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Proceedings Paper

Impulsive coding in optical free-space links: optimum choice of the receive filter and impact of a transmit booster amplifier
Author(s): Peter J. Winzer; Andras Kalmar
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Paper Abstract

A theory for the signal-to-noise ratio of optical direct detection receivers employing return-to-zero coding (and possibly optical preamplification) is developed. The results are valid for both signal-independent noise limited and signal-dependent noise limited receivers, as well as for arbitrary optical pulse shapes and receive filter characteristics, taking into account intersymbol interference. Even if the same receiver bandwidth is used, return-to-zero coding is seen to yield higher signal-to-noise ratio than nonreturn-to-zero coding. Asymptotic expressions for the signal-to-noise ratio for very high and very low receiver bandwidths show that the full sensitivity enhancement potential of return-to-zero coding is exhausted at fairly moderate duty cycles. A realistic example taking into account inter-symbol interference shows that a receiver sensitivity gain (compared to nonreturn-to-zero coding) of e.g. 3.2 dB can be obtained in a signal-independent noise limited receiver with a bandwidth of 80% of the data rate, using a duty cycle of 3. For the signal-independent noise limited case, the sensitivity enhancement potential depends on the receive filter characteristics; we provide a design rule for filters with high sensitivity enhancement potential. Further, we investigate the role of rare-earth doped booster amplifiers in impulsively coded communication links: It is shown that, due to the average power limitation of these devices, a less powerful booster amplifier as with nonreturn-to-zero coding can be employed if certain conditions regarding the data rate and the return-to-zero duty cycle are met.

Paper Details

Date Published: 26 April 1999
PDF: 11 pages
Proc. SPIE 3615, Free-Space Laser Communication Technologies XI, (26 April 1999); doi: 10.1117/12.346171
Show Author Affiliations
Peter J. Winzer, Technische Univ. Wien (United States)
Andras Kalmar, Technische Univ. Wien (Austria)

Published in SPIE Proceedings Vol. 3615:
Free-Space Laser Communication Technologies XI
G. Stephen Mecherle, Editor(s)

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