The maximum data throughput in a single mode optical fibre is a function of both the signal bandwidth and the wavelength-dependent signal-to-noise ratio (SNR). In this paper, we investigate the use of hybrid discrete Raman & rare-earth doped fibre amplifiers to enable wide-band signal gain, without spectral gaps between amplification bands. We describe the widest continuous coherent transmission bandwidth experimentally demonstrated to date of 16.83 THz, achieved by simultaneously using the S-, C-and L-bands. The variation of fibre parameters over this bandwidth, together with the hybrid amplification method result in a significant SNR wavelengthdependence. To cope with this, the signal was optimised for each SNR, wavelength and transmission band. By using a system-tailored set of geometrically shaped constellations, we demonstrate the transmission of 660⇥25 GBd channels over 40 km, resulting in a record single mode fibre net throughput of 178.08 Tbit/s. Index Terms-Broadband transmission system, high order modulation format, geometric shaping.

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We report a novel, two-crystal, walkoff-compensated optical parametric oscillator design using β-BaB2O4, which significantly improves the performance of the device. The oscillator is pumped at 354.7 nm and is tunable throughout 0.42–2.3 μm with overall conversion efficiencies as high as 32%. We also report on demonstration of linewidth narrowing in the same β-BaB2O4 oscillator, obtaining linewidths as narrow as 0.3 Å.

Raman amplification has been commercially utilized in optical transmission systems for more than a decade. The drive towards higher spectral density has increased the interest in Raman to improve system performance. This tutorial reviews the benefits of Raman amplification, defines methods to analyze system performance, and describes the issues involved with system deployment and operation.Index Terms-Distributed amplifiers, optical fiber amplifiers, Raman scattering, optical fiber communications, optical fiber networks, coherent communications. 0733-8724 (c)

Hybrid distributed Raman-EDFA amplifiers, with a continuous 91 nm gain bandwidth and 1.4 dB average effective noise figure, are used to enable a record single mode fibre transmission capacity of 120 Tbit/s using 312×35 GBd DP-256QAM over 9×70 km spans.