——At present, is single-mode fiber still the mainstream application of fiber transmission?
——Yes, multi-core fiber is a cutting-edge attempt. There are some related applications, which are still not mainstream, but will become possible in the next generation.
The above is the brief beginning of OFweek Optical Communication and Xiao Limin from the School of Information Science and Engineering of Fudan University on the topic of optical fiber application trends.
Recently, Limin Xiao's research group from the School of Information Science and Engineering of Fudan University has made an important breakthrough in the research of multi-core optical fiber fusion technology - prepared multi-core optical fiber core-spacing converters with excellent performance, which is the first time in the world to realize dissimilar multi-core optical fibers. Low-loss and low-crosstalk splicing between. Hangzhou Softel Optic Co., Ltd congratulates on this.
The inevitable development trend of optical fiber communication transmission
At present, with the rapid development of cloud computing, high-definition video, Internet of Things and 5G communication systems, global network traffic has increased dramatically. However, the transmission of ordinary single-core single-mode fiber is limited by the Shannon limit. In the next few years, the contradiction between the weak optical network growth and the market's high bandwidth demand will become increasingly acute, which has become an important problem to be solved urgently in the optical communication industry.
In order to solve the problem of future expansion of optical communication, the industry-recognized technical solution to increase the capacity of a single fiber is to use space division multiplexing technology. Multi-core fiber, multi-mode fiber or multi-core multi-mode fiber is the inevitable development trend of optical fiber communication transmission.
Multi-core optical fibers can efficiently increase the spatial density of optical fibers, and have been preempted by Internet giants overseas.
In order to seize the communication market and expand the transmission band of optical fiber, as early as 2018, Facebook and Google bet on ways to increase the number of optical fibers in the cable.
For example, the Dunant cable, which Google put into use in January, has 12 pairs of fibers with a total capacity of 250 Tbit/s. And its two networks under construction in the Atlantic have used 16 pairs of optical fibers, which are expected to achieve a full capacity of 350 to 370 Tbit/s.
And most recently, in mid-October, Facebook commissioned NEC to build the world's highest-capacity submarine cable -- a new transatlantic cable with 24 pairs of optical fibers that, when completed, will run the world's busiest data highway -- Achieve a record total transfer capacity of 500 TB per second (approximately 4000 Blu-ray Disc data) between North America and Europe.
Not at the same time, by Benjamin J. of the National Institute of Information and Communication Technology (NICT) in the United States. A research team led by Puttnam reports that their team used a 4-core optical fiber with an outer diameter of 0.125 mm to transmit data. By combining various amplifier technologies, a transmission system was constructed that took advantage of WDM technology, creating a transmission system through standard cladding. Recording of data transmitted by diameter fiber: 319 Tbit/s data rate transmission throughput per channel is achieved over distances up to 3001 km.
More applications are being reported one after another.
Multi-core fiber core-to-core converters unlock new application potential
Compared with traditional single-core fibers, multiple cores in a multicore fiber (MCF) share the same cladding. This high-density, multi-channel structure has the advantages of low production cost, space saving, and high transmission capacity. Therefore, multi-core fibers have extremely important application value in space-division multiplexing optical communication systems, data center connections, inter-chip communication, next-generation fiber amplifiers, optical sensing, and quantum technology.
Research on new multi-core fiber technology is one of the research priorities to solve the problem of future communication capacity expansion.
However, up to now, there is still no unified standard for the design of multi-core optical fibers in the world. When manufacturing multi-core optical fibers, high-tech companies have different aspects such as the number of cores, core arrangement, core size, core spacing, refractive index distribution, etc. Each is different, which makes the fusion between different types of multi-core fibers more difficult.
For example, FiberHome Fujikura Optic Technology Co. Ltd and other companies need to splicing dissimilar multi-core fibers to build a long-distance multi-core fiber transmission system. The limited multi-core fiber fan-in and fan-out devices may not match the multi-core fibers used in the transmission system.
"Low-loss optical fiber fusion splicing technology is the foundation of optical fiber devices and systems. In academic research, only the progress of fusion splicing of the same type of multi-core optical fiber has been reported, but the technical bottleneck of fusion splicing of different types of multi-core optical fibers has not been solved. There are studies abroad. Some people even think that the fusion of different types of multi-core fibers is almost impossible, which seriously hinders the wide application in this field." Xiao Limin said.
Establishing a huge multi-core fiber multi-channel multiplexing system and splicing dissimilar species, especially multi-core fibers with different core spacings, is an unavoidable technical bottleneck problem at present.
In order to overcome this technical problem brought about by the development of multi-core optical fiber technology, Xiao Limin's research group from the School of Information Science and Engineering, Fudan University has finally made a new international breakthrough in multi-core optical fiber fusion technology after painstaking research. The multi-core fiber core spacing converter with excellent performance realizes low-loss and low-crosstalk fusion splicing between dissimilar multi-core fibers.
Xiao Limin's research group proposed the multi-core fiber taper technology (Figure 2), including forward taper and reverse taper techniques, both of which can be used to adjust the multi-core fiber core spacing and control the mode characteristics of the multi-core fiber at the same time.
Based on the multi-core fiber reverse taper technology, by matching the core spacing and mode field diameter of dissimilar multi-core fibers, Xiao Limin's research group can accurately prepare low-loss and low-crosstalk cores for two types of multi-core fibers with mismatched core spacings. Spacing converter.
