ZTE claims record for single-carrier 400G transmission

ZTE Corp. (H: 0763.HK / A: 000063.SZ) is claiming a new world record for 400G high-speed optical transmission using a single carrier. The previous distance record for single-carrier 400G transmission was 1200 km, in which non-standard fibers and all-optical Raman amplification technology were used.

In the experiment, ZTE successfully transmitted 40 channels, each running at 400-Gbps, over 2800 km of standard singlemode fiber (35 spans, 80 km per span). The modulation scheme was single-carrier polarization-division multiplexing quadrature phase-shift keying (PDM-QPSK).

The Chinese vendor presented a paper about its experiment at the European Conference on Optical Communication (ECOC) in Amsterdam today. It also says that a committee of experts from ECOC evaluated the results and presented ZTE with a certificate in recognition of the work.

Single-carrier transmission has advantages over multi-carrier techniques as a way to increase channel rate and system capacity because it has simple transmitting and receiving structures and is easier to manage, according to ZTE. What’s more, PDM-QPSK modulation is a well-developed modulation scheme with acute receiver sensitivity, which makes it possible to employ standard singlemode fibers and ordinary erbium-doped fiber amplifiers to achieve ultra-long-distance system transmission – and that means no need for major modifications to the installed fiber base. “The experiment demonstrates the feasibility of deploying wavelengths beyond 100G over the current fiber transmission system,” said ZTE in its press release.

At the same time, the single-carrier system reaches 108 Gbaud, the highest symbol rate in the industry. It will be a while before the electronics needed to generate such high-speed signals becomes available, however, so the researchers used optical time-division multiplexing.

ZTE is clearly aiming to make a name for itself in high-speed transmission. It claims to have been one of the first equipment manufacturers to demonstrate a single-channel 11.2-Tbps optical signal in the laboratory, which was successfully transmitted over 640 km of standard singlemode fiber (see “ZTE describes single-channel 10 Tbps experiment”).

In February 2012, ZTE, in cooperation with Deutsche Telekom, successfully completed 2450-km ultra-long-distance hybrid transmission of 100G/400G/1T signals in Germany, marking what the vendor claims is the longest distance of high-speed signal hybrid transmission over installed fiber in the industry.

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 (see “ZTE displays 400-Gbps and 1-Tbps DWDM prototype”).

For more information on high-speed transmission systems and suppliers, visit the Lightwave Buyer’s Guide.