Joint Digital Signal Processing Receivers for Spatial Superchannels

TLDR

Spatial superchannels bundle SDM modes at a wavelength, simplifying transponder and routing design, and enable exploitation of common‑mode impairments to streamline receiver DSP. The study aims to demonstrate reception of spatial superchannels with a coherent receiver using joint DSP and to assess applying the technique to subchannels on separate single‑mode fibers as a transition toward multicore fiber networks. The authors implement a coherent receiver with joint DSP that performs master‑slave phase recovery on two 112‑Gbps subchannels in a seven‑core fiber, reducing processing complexity without increasing bit‑error rate, and explore extending the method to single‑mode fibers. Laboratory measurements show strong correlation of phase fluctuations across multicore fiber cores, confirming common‑mode impairment, and the master‑slave phase recovery achieves reduced processing complexity with unchanged bit‑error ratio.

Abstract

We discuss the advantages of spatial superchannels for future terabit networks based on space-division multiplexing (SDM), and demonstrate reception of spatial superchannels by a coherent receiver utilizing joint digital signal processing (DSP). In a spatial superchannel, the SDM modes at a given wavelength are routed together, allowing a simplified design of both transponders and optical routing equipment. For example, common-mode impairments can be exploited to streamline the receiver's DSP. Our laboratory measurements reveal that the phase fluctuations between the cores of a multicore fiber are strongly correlated, and therefore constitute such a common-mode impairment. We implement master-slave phase recovery of two simultaneous 112-Gbps subchannels in a seven-core fiber, demonstrating reduced processing complexity with no increase in the bit-error ratio. Furthermore, we investigate the feasibility of applying this technique to subchannels carried on separate single-mode fibers, a potential transition strategy to evolve today's fiber networks toward future networks using multicore fibers.