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Fast Light and the Speed of Information Transfer in the Presence of Detector Noise

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3 Author(s)
Feng, M.Z. ; ARC Special Res. Centre for Ultra-Broadband Inf. Networks, Univ. of Melbourne, Melbourne, VIC, Australia ; Sorin, W.V. ; Tucker, RodneyS.

The phenomenon of fast-light pulse propagation has seen renewed interest in recent years, but its relationship to the speed of information transfer is still being debated. In this paper, we define the speed of information transfer as the propagation speed of a point of constant signal-to-noise ratio (SNR) on the leading edge of a signal pulse. We use standard telecommunication analysis to include the effects of noise so that the bit-error rate (BER) can be calculated as a function of a variable decision time. We introduce the concept of a time-dependent Q-factor so that pulse arrival times can be compared at equivalent BERs. We show that when receiver noise is included in a gain-assisted fast-light system, the measured speed of information transfer can exceed the speed of light for an equivalent pulse travelling through a vacuum.

Published in:

Photonics Journal, IEEE  (Volume:1 ,  Issue: 3 )