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, an increase of nearly 40 percent over last year’s record.

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 the 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 the 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 the transmission capacity of each core and channel by adjusting the information entropy of the loading signal.

According to cgtn