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.

We experimentally demonstrated the transmission of 312⇥35 GBd DP-256QAM over 9⇥70 km spans using hybrid distributed Raman-EDFA (HRE) amplifiers with a continuous 91 nm gain bandwidth. A total throughput of 120 Tbit/s over 630 km is demonstrated, with a net achievable information rate after SD-FEC of 10.99 bit/symbol. An extensive, theoretical investigation of the noise contributions originating from amplifier, transceiver sub-system and fiber nonlinearity were carried out using the Gaussian noise model in the presence of inter-channel stimulated Raman scattering (ISRS GN model). The ISRS GN model accounts for arbitrary, wavelength dependent signal power profiles along fiber spans, which is vital for the modeling of ultra-wideband transmission, particularly for hybrid Ramanamplified links. The analysis serves to quantify the relative noise contributions and explain the performance achieved. It was found that, due to the low noise HRE amplifier and a transmission distance of 630 km, the noise originating from the transceiver sub-system imposed a penalty of 6 dB in SNR. For this system, the transceiver noise is, therefore, the main limitation to the system throughput.Index Terms-Hybrid Raman-EDFA amplifier, broadband transmission system, high order modulation format, adaptive rate LDPC decoder.

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.

Transmission of 306×35 GBd, dual polarization, 64-ary geometrically shaped channels over 90×70 km of SMF was demonstrated, achieving a net throughput of 74.38 Tb/s. A combination of hybrid fiber spans and EDFA/Raman amplifiers enabled a continuous gain bandwidth of 10.8 THz.

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