Optical amplifier noise figure in a coherent optical transmission system

Abstract

Two important aspects of optical amplifier noise figure as measured with a heterodyne detection receiver are investigated. First, differential mode gain will result in polarization-dependent degradation of the perceived amplifier noise figure, even when the noise figures for the TE and TM modes of the amplifier are the same. For a differential mode gain of 7.5 dB the noise figure degradation can be as large as 3 dB, and experimental data is reported in good agreement with theoretical predictions. Secondly, the first experimental demonstration of the use of image-rejection techniques to improve the sensitivity of a heterodyne receiver limited by beat noise between the local oscillator and amplified spontaneous emission is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>