448-Gb/s Reduced-Guard-Interval CO-OFDM Transmission Over 2000 km of Ultra-Large-Area Fiber and Five 80-GHz-Grid ROADMs

TLDR

The authors propose a novel coherent optical OFDM scheme with reduced guard interval to enable high‑speed, high‑spectral‑efficiency long‑haul transmission. The scheme compensates chromatic dispersion at the receiver, uses reduced guard intervals, employs orthogonal band multiplexing, and receives the 448‑Gb/s signal with banded digital coherent detection across two detection bands. They generated a 448‑Gb/s RGI‑CO‑OFDM signal with 16‑QAM subcarriers, transmitted it over 2000 km of ultra‑large‑area fiber with five 80‑GHz‑grid ROADMs, and demonstrated WDM of three such channels achieving 5.2 b/s/Hz spectral efficiency over 1600 km.

Abstract

We propose a novel coherent optical orthogonal frequency-division multiplexing (CO-OFDM) scheme with reduced guard interval (RGI) for high-speed high-spectral-efficiency long-haul optical transmission. In this scheme, fiber chromatic dispersion is compensated for within the receiver rather than being accommodated by the guard interval (GI) as in conventional CO-OFDM, thereby reducing the needed GI, especially when fiber dispersion is large. We demonstrate the generation of a 448-Gb/s RGI-CO-OFDM signal with 16-QAM subcarrier modulation through orthogonal band multiplexing. This signal occupies an optical bandwidth of 60 GHz, and is transmitted over 2000 km of ultra-large-area fiber (ULAF) with five passes through an 80-GHz-grid wavelength-selective switch. Banded digital coherent detection with two detection bands is used to receive this 448-Gb/s signal. Wavelength-division multiplexed transmission of three 80-GHz spaced 448-Gb/s RGI-CO-OFDM channels is also demonstrated, achieving a net system spectral efficiency of 5.2 b/s/Hz and a transmission distance of 1600 km of ULAF.