Optimizing the placement of spare amplifier cards to increase the achievable information rate resilience

We evaluate the impact of optical amplifier failure on the achievable information rate (AIR) of a transmission link. We consider two scenarios to avoid link failure. First, we consider that after amplifier failure the optical signals are switched to a redundant passive optical line card which surpasses the damage amplifier. Second, we assume that the optical signals are switched to a redundant amplifier card. From the evolution of the AIR with the position in the link where the failure occurs we demonstrate which are the critical amplifiers that demand amplifier cards redundancy to avoid a link failure, and in which place a redundant passive optical line card is admissible. We consider polarization multiplexing (PM) quadrature amplitude modulation (QAM) constellations. To evaluate the AIR, we consider the optical amplified spontaneous emission noise and the nonlinear interference optical noise coherent, as well as the receiver thermal and shot noise sources. Results show that for the first scenario the maximum value attainable by the AIR is strongly dependent on the position of the amplifier failure on the transmission link, being the first amplifiers more critical for the performance of the link. Findings also show that a failure of the last amplifier tends to not affect the AIR. We also observe that it is possible to partially compensate the AIR decrease after an amplifier failure in the first scenario, by optimizing the gain of the remain available amplifiers on the transmission link and by optimizing the transmitter power.