ZTE claims to have set a new world record for 400G high-speed optical transmission based on single-carrier DWDM. The Chinese vendor presented a paper about its work at ECOC in Amsterdam.
In the experiment, ZTE successfully transmitted 40 channels, each carrying 400Gbps, over 2800km of standard singlemode fibre arranged in 35 spans, with 80 km per span. The previous distance record for single-carrier 400G transmission was 1200km, and relied on non-standard types of optical fibre as well as Raman amplification.
Optical vendors and carriers are investigating 400Gbps as a way to increase channel rate and overall system capacity. Single-carrier transmission has advantages over multi-carrier schemes because it has simple transmitting and receiving structures and is easier to manage, according to the Chinese vendor.
ZTE also points out that the modulation scheme that it used – polarization-division multiplexing quadrature phase-shift keying (PDM-QPSK) – is a well-developed scheme that benefits from acute receiver sensitivity, which makes it possible to employ standard singlemode fibres and ordinary erbium-doped fibre amplifiers to achieve ultra-long-distance system transmission. That means no need for major modifications to the installed fibre base.
“The experiment demonstrates the feasibility of deploying wavelengths beyond 100G over the current fibre transmission system,” said ZTE in its press release.
The single-carrier system reaches 108 Gbaud, which the company claims is the highest symbol rate in the industry. It will be a number of years before the electronics needed to generate such high-speed signals becomes generally available, however, so the researchers used optical time-division multiplexing (OTDM) to generate the data signal.
ZTE is clearly aiming to associate its name with high-speed transmission. The Chinese vendor says it had a prototype 1Tbps DWDM as early as July 2011, and that during 2012 it has released seven versions of 400G/1T DWDM prototype equipment targeting a variety of network applications
By Pauline Rigby