Improving the Spectral Efficiency of DWDM-DST Systems through Line Coding and Optimized FBGs

Abstract

In this contribution we show that by using the dense wavelength division multiplexing (DWDM) and the dispersion supported transmission (DST) techniques, together with compressed bandwidth data formats and optimized fiber Bragg grating (FBG) filters, it is possible to implement optical fiber communication systems with very high spectral efficiencies and long fiber spans. This is achieved by using fiber gratings with a Gaussian apodization together with a non-uniform average index perturbation, acting simultaneously as optical demultiplexers and group velocity dispersion compensators. For a be 32 x 20 Gsymbol/s WDM-DST system, we demonstrate spectral efficiencies of 0.7 bit/s/Hz for the binary and duobinary data formats, at distances of 65 km and 100 km, respectively, over standard single-mode fiber. Using 4-level coding, 1.28 Tbit/s (32 x 40 Gbit/s) can be packed in approximately 10 nm of optical bandwidth, corresponding to a spectral efficiency of 1 bit/s/Hz, and transmitted over a fiber span with 45 km.