China Telecom Completes World’s First Bi-directional Real-time Transmission Verification of Thousand Kilometer Hollow Fiber Optic Cables
Recently, the co construction units of China Telecom Research Institute and Changfei Company, as well as ZTE Corporation, jointly completed the world’s first thousand kilometer air core fiber bidirectional real-time transmission verification: on a 1007.48-kilometer air core fiber link, the extended C+L band single wave 800Gb/s (PCS-16QAM modulation) single fiber bidirectional transmission was achieved, with a total capacity of 128Tb/s, pushing the distance record of real-time transmission of air core fiber to a new height, marking another milestone breakthrough in China’s key core technology for next-generation optical communication.
This experiment is based on the National Key Laboratory Innovation Platform for Advanced Manufacturing and Application Technology of Optical Fiber and Cable and the China Telecom Cloud Network Integration Technology Experimental Verification Platform, coordinating and promoting collaborative research and development at the three levels of optical fiber, equipment, and systems. At the fiber end, by optimizing the fiber preparation process, the absorption of CO ₂ and CO gas lines (GLA) in the extended C+L band has been eliminated, overcoming the core technical challenge of GLA deteriorating transmission performance; At the device end, by combining the loss characteristics of hollow fiber and the working characteristics of amplifiers, high-power amplifiers are abandoned and commercial amplifiers with conventional output power are selected to achieve the optimal performance of a single wave 800G full wave transmission system; On the system side, a lightweight front-end pre equalization scheme is used to ensure smooth and balanced performance of the extended C+L full band channel. An end-to-end reflection and mode interference impact assessment model is established, and extreme operational scenarios such as band dropout are verified to confirm that the system has no performance degradation in this scenario.
This experiment has achieved three landmark advances: firstly, setting a record for the world’s longest point-to-point non loopback real-time transmission distance of hollow fiber optic cables, with a loss margin of no less than 3dB per span and at least 3dB of OSNR system maintenance margin; The second is the completion of real-time bidirectional transmission of single fiber hollow core optical fibers at the kilometer level for the first time, verifying the feasibility of long-distance bidirectional transmission. The OSNR degradation caused by reflection ranges from 0.5dB to 4dB; The third is to build the world’s longest extended C+L band GLA free air core fiber transmission link, achieving GLA free transmission in the extended C+L band on a thousand kilometer air core fiber link.
The success of this experiment provides a practical and feasible technical basis for constructing a backbone network with high bandwidth, long distance, and low latency based on high-order modulation format systems using hollow fiber. It is an important achievement of China’s independent innovation in key core technologies of next-generation optical communication, further consolidating China’s leading position in the global hollow fiber technology and industry. China Telecom stated that it will continue to work with industry partners to deepen the innovation and industrialization of hollow fiber optic technology, build a solid “optical foundation” for the development of computing power networks and digital economy, and help the global optical communication network move towards a faster, lower latency, and more efficient future.