Number of visits: date: 2022-10-15
Source: OFweek Light Communication network
-- Is single-mode fiber still the main application in fiber optic transmission?
Yes, multicore fiber is a cutting-edge endeavor. There are some related applications that are still not mainstream, but they will be possible in the next generation.
The above is a brief introduction to the topic of optical fiber application trends by Professor Xiao Limin of OFweek Optical Communication and School of Information Science and Engineering of Fudan University.
Recently, the research group of Xiao Limin, School of Information Science and Engineering, Fudan University, has made an important breakthrough in the research of multi-core fiber fusion technology. It has fabricated multi-core fiber core to distance converter with excellent performance, and achieved low-loss and low-crosstalk fusion between heterogeneous multi-core fibers for the first time in the world. Vico Optical Communications sent a message of congratulations.
The inevitable development trend of optical fiber communication transmission
Today, the global network traffic is increasing rapidly due to the booming business of cloud computing, high-definition video, Internet of things and 5G communication systems. However, the transmission of common single-core single-mode fiber is limited by Shannon limit. In the next few years, the contradiction between the weak growth of optical network and the demand of high bandwidth in the market 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 optical communication capacity expansion in the future, the industry recognized technical solution to improve the capacity of single fiber is to use the space division multiplexing technology, multi-core fiber, multi-mode fiber or multi-core multi-mode fiber is the inevitable development trend of fiber communication transmission.
A breakthrough in space division multiplexing fiber technology: Seamless optical interconnection can be realized between different types of multi-core fibers
Multi-core optical fiber can effectively improve the spatial density of optical fiber, which has been preemptively applied by Internet giants overseas.
As early as 2018, Facebook and Google bet on increasing the amount of fiber in their cables in order to capture the communications market and expand the frequency band of fiber.
Google's Dunant cable, for example, which went live in January, has 12 pairs of fiber with a total capacity of 250 Tbit/s. Two of its networks under construction in the Atlantic are using 16 pairs of fiber, which are expected to have 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, the New Transatlantic Cable, with 24 pairs of fiber optics. It will deliver a record total capacity of 500 terabytes per second (about 4,000 Blu-ray discs of data) between North America and Europe on the world's busiest data superhighway.
The difference was not made at the same time by Benjamin J. A research team led by Puttnam reported that his team used a 4-core fiber with an outer diameter of 0.125 mm to transmit data, and by combining various amplifier technologies, built a transmission system that took advantage of WDM technology, setting a record for data transmission over a standard cladding diameter fiber: Let each channel achieve a transmission throughput of 319 Tbit/s data rate over a distance of up to 3001 km.
More applications are also being reported.
Multi-core fiber-to-core converters unlock new potential applications
Compared with the traditional single-core fiber, multiple cores in Multicore fiber (MCF) share the same cladding. This high-density and multi-channel structure has the advantages of low production cost, space saving and high transmission capacity. Multi-core fiber has very important application value in space division multiplexing optical communication system, data center connection, interchip communication, next generation fiber amplifier, optical sensing, quantum technology and so on.
The research of new multi-core fiber technology is one of the key points to solve the problem of future communication capacity expansion.
However, up to now, there is still no unified international standard for the design of multi-core fiber, and high-tech companies are different in the number of fiber cores, core arrangement, core size, core spacing, refractive index distribution and other aspects when manufacturing multi-core fiber, which increases the difficulty of fusion between different types of multi-core fiber.
FiberHome Fujikura Optic Technology Co. Ltd and other companies need to fuse heterogeneous multi-core fibers to build a long-distance multi-core fiber transmission system. However, limited fan-in and fan-out devices may not match the multi-core fibers used in the transmission system.
"Low loss optical fiber welding technology is the basis of optical devices and systems, on the academic research, more than just reported the same core optical fiber welding progress, but different types of core optical fiber welding the technology bottleneck problem remains unresolved, foreign researchers even think that different types of fiber fusion are almost impossible to achieve, which severely hampered widely used in the field." "Xiao Limin said.
To build a huge multi-core fiber multichannel multiplexing system and fuse dissimilar fiber, especially multi-core fiber with different core spacing, is an unavoidable technical bottleneck.
To conquer many core optical fiber technology development of this technical problem, information science and engineering school of fudan university XiaoLi sensitive group after studying, finally in multi-core optical fiber welding technology make a new breakthrough in the world - the preparation of the various performance of multi-core optical fiber core spacing converter, realized the heterogeneous multi-core optical fiber low loss and low crosstalk between welding.
Xiao Limin's research group proposed multi-core fiber pulling technology (FIG. 2), including forward pulling and reverse pulling, which can be used to adjust the core spacing of multi-core fiber and simultaneously regulate the mode characteristics of multi-core fiber.
Based on the technology of multi-core fiber reverse pull cone, by matching the core spacing and mode field diameter of heterogeneous multi-core fibers, Xiao Limin's research group can accurately prepare a low-loss and low-crosstalk core spacing converter for two kinds of multi-core fibers with mismatched core spacing.
For two kinds of multi-core fibers with different structure and core spacing difference of 26 μm (FIG. 3 (a, b)), the core spacing converter prepared by Xiao's group can achieve the loss as low as 0.18 dB and the crosstalk as low as -68 dB.
For multi-core fibers with the same junction and slightly different core spacing (FIG. 3 (b, c)), the loss of the core spacing converter is as low as 0.17 dB and the crosstalk is as low as -66 dB.
A breakthrough in space division multiplexing fiber technology: Seamless optical interconnection can be realized between different types of multi-core fibers
The fabrication technology of multi-core fiber core to distance converter proposed by Xiao Limin's research group perfectly solves the technical problems of heterogeneous multi-core fiber fusion in optical communication networks, provides a unique perspective for the fabrication of multi-core fiber devices, and will release more potential of multi-core fiber in practical applications.
The results were published in the journal Optics Letters: Low-loss fusion splicing between spacing-mismatched multicore fibers. Wei Ji and Ruowei Yu are the co-first authors, and Limin Xiao is the corresponding author of the paper. This research was supported by the Yiwu Research Institute of Fudan University.
