In the era of big data, artificial intelligence, the Internet of Things, and the forthcoming 6G networks, the capacity of single-mode optical fiber is no longer sufficient to meet the exponentially growing demand for data transmission speed and volume. The need for new, high-capacity optical fibers has never been more urgent. While we effortlessly enjoy short videos, streaming media, and facial recognition payments, a "capacity crisis" is quietly approaching. How long can current optical communication technologies continue to support our digital world? Is it still possible to expand transmission capacity through optical fibers?
Space-division multiplexing (SDM) technology, particularly using multi-core fibers (MCF), has emerged as a promising solution to multiply communication capacity. Research and development efforts across Europe, the United States, and Japan acknowledge MCF as a viable pathway to overcoming the current capacity limitations of optical communication. Multi-core few-mode fibers increase the number of transmission channels by incorporating multiple cores, each capable of carrying several modes, effectively addressing future needs for communication expansion.
Building the Foundation: Research and Development of Multi-Core Fibers and Passive Devices
In 2019, Professor Li Shuguang of Yanshan University led a critical national research project titled "Research on Multi-Core/Few-Mode Microstructured Optical Fibers and Their Passive Devices" under the National Key R&D Program of China. This project, supervised by Professor Dong Yi of Beijing Institute of Technology, involved systematic research on the design, fabrication, and testing of multi-core few-mode fibers and their passive components based on guided-wave optics and coupled-mode theory.
The research team successfully developed a 13-core few-mode fiber. Each core in this fiber can transmit five LP modes. When accounting for degenerate modes, each core supports up to eight modes, meaning the entire fiber can carry 104 independent channels—a substantial leap in communication capacity.
However, multi-channel transmission introduces challenges such as inter-core crosstalk and intra-core mode coupling, which can severely degrade signal quality. Therefore, a key scientific and technical challenge in developing and applying multi-core few-mode fibers is minimizing these crosstalk effects.
Experimental results for the 13-core fiber demonstrated an inter-core crosstalk level below -30 dB/100 km (or -50 dB/km). Bit error rate measurements and eye diagram analyses confirmed that the fiber meets the requirements for long-distance transmission.
Collaborating with Professor Cheng Tonglei of Northeastern University and Professor Yuan Jinhui of Beijing University of Science and Technology, the team also developed spatial multiplexers, mode multiplexers, and beam splitters specifically designed for their 13-core few-mode fiber.
This significant project concluded successfully in May 2023, receiving unanimous praise from review experts. Key findings were published in the top-tier journal Optics Express. The team has been granted two Chinese patents and one U.S. patent for their innovations in low-crosstalk, large-capacity few-mode fibers.
The project involved researchers from multiple institutions, including Yanshan University, Northeastern University, Beijing University of Science and Technology, Beijing Institute of Technology, and Zhongtian Precision Material Co., Ltd., along with contributions from several doctoral students.
Industry-Academia Collaboration: Expanding Applications and Promoting Industrialization
The future focus of Professor Li Shuguang’s team is to advance the industrialization of multi-core fiber technology. Through university-enterprise collaboration, they aim to establish an industrial incubation and demonstration center for multi-core fibers and related devices, paving the way for large-scale production and practical application.
High-Speed, Large-Capacity Optical Communication Systems
Multi-core few-mode fibers are central to breaking through current optical communication limits and supporting 6G technologies. Future 6G networks will integrate terrestrial wireless and satellite communications, creating a fully connected world. Signals will reach even the most remote villages, enabling telemedicine and distance education, bridging the digital divide, and revolutionizing lifestyles through the Internet of Everything and intelligent connectivity.
Multi-Dimensional, Multi-Parameter Sensors
Sensors based on multi-core fibers can simultaneously measure multiple physical quantities—such as refractive index, temperature, bending, twisting, stress, strain, and humidity—across different dimensions. These advanced sensors are critical for the development of smart robotics and represent the next frontier in sensor technology.
High-Precision, Miniaturized Fiber Optic Gyroscopes
By employing coil multiplexing technology and unique coupling methods in multi-core fibers, the effective length of the fiber coil can be multiplied without increasing its physical size. This approach significantly enhances the measurement accuracy of fiber optic gyroscopes, which are vital for navigation systems.
Novel Optoacoustic Devices
Current ultrasonic transmitters and sensors based on single-core fibers suffer from low excitation efficiency, limited sensitivity, and narrow detection ranges. Combining multi-core fibers with new composite transducer materials promises higher optoacoustic conversion efficiency, greater acoustic pressure output, improved sensitivity, wider bandwidth, and deeper detection capabilities.
Cultivating Talent and Advancing Research in Specialty Optical Fibers
With 37 years in education, Professor Li Shuguang has made significant contributions to both teaching and research. After graduating from Shanxi Normal University in 1988, he taught at Wuzhai Normal School, dedicating his early career to foundational education in Northwest Shanxi. Since joining Yanshan University in 2000, he has taught core courses including optics, electromagnetics, electromagnetic field theory, and nonlinear optics.
Under the mentorship of Professor Hou Lantian, an authority in specialty optical fibers and infrared technology, Professor Li embarked on research into new photonic devices based on specialty fibers. Today, as a distinguished professor and doctoral advisor at Yanshan University, he continues to lead advancements in this field.
To date, Professor Li has supervised 50 master's and 16 doctoral students. Among them, 26 have received outstanding thesis awards at the university level, seven have earned provincial outstanding master's thesis awards, two have won provincial outstanding doctoral thesis awards, and one has been recognized as a national-level young talent.
His graduates now hold positions at prominent institutions such as Beihang University, Northeastern University, Yanshan University, and Hebei University of Technology, among others. Others contribute to government, military, and high-tech enterprises, reflecting the broad impact of his mentorship.
For his teaching excellence, Professor Li received the Hong Kong-based Fok Ying Tung Education Foundation Award for Young Teachers in 2004 and was twice honored as an Advanced Individual in Ethics at Yanshan University.
An active member of several professional societies, including the Chinese Physical Society and the Optical Society of America, Professor Li has also served as a director of the Chinese Optical Society and on the editorial board of Optoelectronics. He has led multiple research projects funded by the National Natural Science Foundation of China, the Ministry of Science and Technology, and Hebei Province.
His prolific output includes over 200 academic papers, 34 authorized invention patents, 14 software copyrights, and a scholarly monograph titled Design, Fabrication, and Application of Microstructured Optical Fiber, published by Science Press. He has been invited to deliver 12 conference presentations and has received multiple provincial awards for natural science and technological invention.
Professor Li leads a robust research team focused on specialty optical fibers and devices. The team consists of nine faculty members, including six doctoral advisors and three master's advisors, alongside more than 50 graduate students. Their research spans multi-core fiber communication systems, specialty fiber sensors, nonlinear effects and frequency conversion in microstructured fibers, optoacoustic devices based on specialty fibers, ultrashort pulse fiber lasers, and hollow-core fiber devices.
Looking ahead, Professor Li remains committed to innovation, talent cultivation, and the translation of research achievements into practical applications, contributing persistently to academic advancement and societal progress.
Frequently Asked Questions
What is multi-core few-mode fiber?
Multi-core few-mode fiber is an advanced type of optical fiber containing multiple independent cores within a single cladding. Each core can guide several light modes, significantly increasing the total number of data transmission channels compared to conventional single-mode fibers.
How does multi-core fiber address the optical communication capacity crisis?
By multiplying the number of physical transmission paths (cores) and utilizing multiple modes per core, multi-core fibers dramatically increase overall data capacity without requiring additional fibers. This approach is essential for supporting future high-bandwidth applications like 6G and IoT.
What are the main challenges in deploying multi-core fiber systems?
Key challenges include managing inter-core crosstalk and mode coupling within cores, which can degrade signal integrity. Developing efficient multiplexers, demultiplexers, and compatible optical components is also critical for system integration. 👉 Explore advanced optical communication strategies
In which applications are multi-core fibers most beneficial?
They are particularly valuable in high-speed data centers, long-haul communication links, fiber optic sensing networks, precision gyroscopes for navigation, and advanced optoacoustic imaging and sensing systems.
How does multi-core fiber support the development of 6G technology?
Multi-core fibers provide the immense bandwidth and low latency required for 6G's integrated ground-satellite networks. They are fundamental in building the infrastructure for ubiquitous connectivity, smart cities, and the Internet of Everything.
What is the future outlook for multi-core fiber technology?
Ongoing research focuses on improving fabrication techniques, reducing crosstalk, developing cost-effective components, and enabling large-scale industrialization. The technology is expected to play a cornerstone role in next-generation communication and sensing systems.