Chinese scientists have broken the world record for single-mode multi-core optical fiber transmission capacity, achieving 4.1 Pbit/s combined transmission over 19-core fiber, the research team announced on Tuesday. 

The State Key Laboratory of Optical Communication Technology and Network under China Information and Communication Technologies Group Corporation (CICT), set a world record in the field last November, achieving 3.03 Pbit/s (wavelength division multiplexed (WDM)/space division multiplexing (SDM) combined transmission over 19-core fiber by using 680 wavelength channels with 25-GHz spacing, covering 17 THz bandwidth of S, C and L-band.

The study was published in the journal of IEEE Photonics Technology Letters.

About six months later, the lab broke its own world record and achieved a total transmission capacity of 4.1 Pbit/s with a net transmission capacity of 3.61 Pbit/s, with an increase of nearly 40 percent over last year's record.

Optimized, upgraded system

To make the new record, Xiao Xi, head of the lab, said that the R&D team optimized and upgraded the optical transmission system architecture and its digital signal processing algorithm.

Keeping the 17 THz bandwidth of S, C and L-band, the team optimized some key optoelectronic devices in the system to equal the spectrum in an ultra-wide optical domain, improving performance of transmission channels in different bands.

In the meanwhile, they adopted an advanced ultra-high-order probabilistic constellation shaping algorithm to make full use of transmission capacity of 680 wavelength channels in the S, C and L-band.

Based on the probabilistically-shaped (PCS)-256 quadrature modulation (QAM) and PCS-64QAM formats, and performance differences of each fiber core, the team maximized transmission capacity of each core and channel through adjusting information entropy of the loading signal.