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Electronics Letters

Low-noise amplification under the 3 dB noise figurein high-gain phase-sensitive fibre amplifier

Wataru Imajuku, Atsushi Takada, Y. Yamabayashi

Published Oct 28, 1999• 96 citations
Publisher

Abstract

A noise figure which is less than the standard quantum limit of 3 dB has been observed for the first time in a high gain phase-sensitive fibre parametric amplifier. A noise figure of 1.8 dB with a 16 dB signal gain was measured by a precisely calibrated electrical spectrum analyser.
DOI
10.1049/el:19991343

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The noise figure (NF) of a phase sensitive amplifier (PSA) based on a periodically poled LiNbO3 (PPLN) waveguide was evaluated in the optical and electrical domains. Phase sensitive amplification was realized using degenerate parametric amplification in the PPLN waveguide, which was pumped by the second harmonic frequency of the signal. Second harmonic pumping enables direct observation of the intrinsic amplified spontaneous emission (ASE), which determined the NF of the PSA. An NF below the 3 dB quantum limit was obtained by observing the intrinsic ASE. The low NF was also confirmed via the noise floor measurement of a cascaded PSA and erbium doped fiber amplifier in the electrical domain. The PSA was used as a preamplifier for detecting a 40 Gbit/s phase shift keying signal. The low noise characteristics were confirmed by the improved sensitivity.
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