Huawei claims to have added up to 50% more capacity per fiber in an optical transport network, using a technique called Super C-band. This could greatly increase the efficiency and cost-effectiveness of advanced backhaul and fronthaul deployments for 5G and cloud networks.
The vendor pointed out that a combination of technologies – higher order modulation, flex grid channel spacing, higher symbol rates and super channels – has been deployed in recent years by the optical industry, to boost spectral efficiency in the C-band to deliver 32Tbps per single fiber, or 38.4Tbps in systems supporting the extended C-band.
Now Huawei says it has pushed that capacity further, to 48Tbps per fiber, by developing a new optical amplifier for the Super C-band (Super C), which does away with the need for parallel L-band optics – the usual approach to boosting capacity, but one which adds cost and complexity.
The original ITU G.694.1 C-band channel plan supports 25 GHz, 50 GHz and 100 GHz spacing with built-in guard bands, which adds up to 4 THz of spectrum. A typical implementation supports 8Tbps using 50 GHz spacing and 80 channels of 100Gbps with QPSK modulations and 32 Gbaud symbol rate. Doubling the symbol rate doubles the capacity per fiber to 16Tbps.
The flexible grid standardized by the ITU in 2012 is now being deployed in the mainstream, allowing flexible channel spacing based on multiples of 12.5 GHz, plus multi-carrier super-channels. A typical application will use 75 GHz spacing for 400Gbps channels – with 16QAM modulation this will deliver 32Tbps over a single fiber. A 600Gbps implementation using 64QAM modulation and the 4.8 THz extended C-band, supported by the flexible grid, will boost the maximum to 38.4Tbps.
The Huawei Super C-band approach takes advantage of all these techniques but also increases the width of the C-band further to 6 THz, enabling 120 channels with 50 GHz spacing or 80 channels with 75 GHz spacing. This has been enabled by a new optical amplifier design. A 600Gbps implementation with 64QAM modulation will now support a maximum bandwidth of 48Tbps over a single fiber (80 x 75GHz), which is six times the capacity in a typical 100G system.