Physical Layer Strategies to Save Lightpath Regenerators

We investigate the viability of hybrid fiber amplifiers (HFA) and advanced digital signal processing (DSP)-based transceivers in translucent optical networks. We focus on the reduction of optical-electro-optical (OEO) regenerators required to support a 200 Gbps any-to-any traffic. In this paper, two network topologies, PanEuropean and USNET, are quantitatively analyzed according to three different upgrade strategies. The first upgrade strategy includes selective placement of HFA in a network using different Raman amplification levels. The second upgrade strategy includes the use of two different DSP techniques of digital backpropagation and probability shaping (PS) at the transceivers. The third upgrade strategy involves a combination of both HFA and DSP techniques in a network. Our results indicate that by using these upgradation strategies, a prominent reduction in OEO regenerators can be obtained, which can lead to full transparency of a network. In the Pan-European topology, improving the equivalent noise figure (ENF) of the optical amplifiers by 5 dB, it is possible to reduce by 74% the amount of required regenerators. Then, by applying advanced DSP techniques like PS, this percentage grows up to 82%. In the USNET topology, by reducing the ENF by 2 dB, it is possible to reach full transparency. By using PS, it is enough to reduce the ENF by just 0.5 dB to reach the same results.