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Role of Amplifiers Gain on the Achievable Information Rate of M-ary PSK and QAM Constellations

Silva, N. A. ; Pinto, A. N.

Optics Communications Vol. 383, Nº 1, pp. 215 - 222, January, 2017.

ISSN (print): 0030-4018
ISSN (online): 0030-4018

Journal Impact Factor: 1,552 (in 2008)

Digital Object Identifier: 10.1016/j.optcom.2016.09.008

Abstract
The impact of optical amplification on the achievable information rate (AIR) is evaluated, considering continuous and discrete modulation formats. The theoretical model for the AIR considers the optical amplification noise, the nonlinear optical noise, and the coherent receiver shot and thermal noise sources. Two different scenarios for the AIR are analyzed. First, we admit that the gain of each optical amplifier under or over compensate the previous fiber span loss. After, we consider the case where we remove optical amplifiers from the transmission link. Results show that for the first scenario, when we under or over compensate the span loss the AIR tends to decrease. Nevertheless, for low cardinality constellations the AIR is not primarily limited by the gain of the optical amplifiers. In the second scenario, results show that it is possible to remove amplification stages from the end to the beginning of the transmission link without decreasing the AIR. We observe that for a polarization multiplexing (PM) 4-PSK constellation the plateau of 4 bits/symbol is preserved even if we remove the last two amplifiers from the transmission link.