As reported by our sister site Lightwave, ZTE Corp., a global provider of telecom and network equipment, says it has transmitted 400 Gbps over more than 5000 km.

The transmission, which reportedly involved what ZTE called “a unique frequency algorithm,” used a WDM system based on 100-GHz channel spacing. The link included 25 ROADM nodes, but no electrical repeaters. The company did not reveal where the trial took place, whether a carrier was involved, and whether the optical transport system used was a prototype or commercially available.

Related: First successful North American 400G field trial conducted

More: CDFP MSA group forms to advance 400G cabling, modules

The trial is the most recent in a series of 400-Gbps experiments ZTE has conducted. The company reported at the ECOC 2012 tradeshow that it had sent 40 channels, each running at 400-Gbps, over 2800 km of standard singlemode fiber. The company also unveiled a 400-Gbps/1-Tbps prototype optical transport system the previous June. ZTE said the 5000 km set "a benchmark for the global optical networking industry."

However, as noted by Lightwave, AT&T delivered a paper at this year's OFC/NFOEC in which it reported transmitting 400 Gbps over 12,000 km using a time-domain-hybrid modulation format that comprised a mix of 48 QPSK and 77 8QAM symbols on a 100-GHz grid.

See: Looking from 100/400G toward Terabit networking line cards