China Mobile, together with Peking University, Huawei, and Changfei, completed the world's first research and verification of key technologies of three mode weakly coupled mode division multiplexing real-time transmission

Recently, China Mobile took the lead in collaborating with Peking University, Huawei, and Changfei to jointly develop backbone network transmission technology based on weakly coupled few mode optical fibers. They achieved experimental verification of real-time weakly coupled mode division multiplexing transmission with a total length of 300km, using 3 modes, 4 wavelengths, and 200Gb/s. This has rapidly promoted the research progress of ultra large capacity optical transmission technology based on multidimensional multiplexing for the future.

Three mode weakly coupled mode division multiplexing real-time transmission system block diagram

At present, the ultra high speed optical transmission system based on commercial single-mode fiber is approaching the nonlinear saturation limit. In order to break the capacity bottleneck, few mode optical fibers that can achieve multiple fold growth in transmission capacity by transmitting multiple independent modes have become a research hotspot in recent years and have received widespread attention from academia and industry. Among them, weakly coupled few mode optical fibers and their mode division multiplexing transmission systems have the advantage of being compatible with existing real-time OTN devices and have good practical prospects. China Mobile has conducted long-term research in the field of space division multiplexing transmission based on new optical fibers, exploring their transmission characteristics and growth potential. A total of 5 related papers have been published in journals and conferences such as JLT, OFC, and PJ.

In order to further improve the overall performance of weakly coupled mode division multiplexing transmission systems, the research team has conducted comprehensive optimization from the aspects of fiber optics, fiber optic devices, and transmission system design. China Mobile and Peking University have jointly completed the design of ultra-low crosstalk weak coupling ten mode fiber for optical fiber, and Changfei Company has achieved mass production of this few mode fiber; For fiber optic devices, Peking University has designed and processed an all fiber mode multiplexer with ultra-low loss and crosstalk; For weakly coupled mode division multiplexing transmission systems, China Mobile and Huawei have jointly completed a comprehensive system design based on 200G QPSK OTN commercial equipment; Finally, the verification of the real-time weak coupling mode division multiplexing system with three modes of LP01/LP02/LP03 carrying four 200G wavelength signals together for 300km is realized. Compared to previous similar experiments, the number of available modes has increased to 3, and the transmission distance has been tripled, setting a current world record. This provides an important reference for the development of multi-dimensional multiplexed optical transmission technology for the future.

(a) Weakly coupled ten mode fiber cross-section; (b) Weakly coupled ten mode fiber core structure; (c) Mode field diagrams of LP01, LP02, and LP03 modes