Proposal and feasibility study of a converged all-optical intra-/inter-data-center network with external laser sources to distribute optical carriers to coherent transceivers

Abstract

We propose a DCN architecture that directly connects server racks distributed among DCs connected to metro-access nodes consisting of ROADMs. ELSs are introduced to coherent TRXs to prevent laser diodes being operated under high-temperature conditions on ToR electrical packet switches. A single-wavelength ELS for intra-DCIs is distributed to several hundred TRXs by splitting its optical power. A full C-band WDM ELS for inter-DCIs supplies each wavelength to a TRX. Both intra- and inter-DCIs are executed using an identical colorless coherent TRX, and the wavelength assignment and optical-path switching are carried out using OCSs. We experimentally evaluated the feasibility of the proposed architecture through BER measurements in a four-node ring network with four DCs per node and about 300 racks per DC, where ToR pairs communicated using 112 Gb/s DP-QPSK signals. The intra-DCI results indicate a sufficient received power margin of 11.6 dB despite a 2.4 dB penalty induced by in-band XT occurring in the OCSs. We conducted 42 channel dense WDM transmission experiments involving flat bandwidth loading with ASE noise for inter-DCIs, where in-band XT in each node and DC was ignored since our analytical estimations showed that its impact was negligible. The inter-DCI results indicate a sufficient OSNR margin of 10.9 dB despite the OSNR penalties induced by the linear/nonlinear impairments of 100 km transmission and spectrum narrowing by eight wavelength-selective switches.