多芯掺铒光纤的制备及其放大性能

Fabrication and Amplification Characteristics of Multicore Erbium-Doped Fiber

空分复用技术被认为是未来实现光纤通信容量升级扩容的关键技术。传输距离是决定空分复用系统应用场景的关键,空分复用系统中信号的传输离不开放大器对损耗的补偿,因此,基于多芯掺铒光纤的空分复用光放大器是空分复用技术走向实用化的核心器件。本文基于改进的化学气相沉积技术结合打孔法制备了七芯掺铒光纤,并搭建了纤芯独立泵浦多芯光纤的放大系统,测试了七芯掺铒光纤的放大性能。在输入信号为0dBm,泵浦光功率为350mW的条件下,测得七芯掺铒光纤纤芯在C波段(1526~1566nm)的平均增益为14dB,平均噪声指数小于6dB,不同纤芯间的增益差小于5dB。

Objective With the development of the global mobile internet,short video,internet of things,cloud computing,and 5G technology,there is a rising interest and growth in data communication.The transmission capacity of optical transmission networks in different areas such as in division multiplexing,polarisation mode multiplexing,timedivision multiplexing,and multi-level modulation has now reached 100 TB/s via wavelength technology.However,there are still challenges in the transmission capacity of the existing single-mode optical fibre communication system due to the nonlinear effect in the fibre.Multicore fibre space division multiplexing technology is one of the pivotal technologies required to realise exponential growth in fibre transmission capacity.As early as 1979,the concept of multicore fibre was introduced.However,due to the popularisation of erbium-doped fibre amplifier and dense wavelength division multiplexing,the space division multiplexing technology did not receive much attention.Space division multiplexing technology expands the data-carrying capacity of the optical communication system using space.If the existing commercial single-mode fibre is compared to a single-layer road,then the space division multiplexing based on multicore fibre would be equivalent to laying a multilayer viaduct at a time.In this case,space channels increase several times,meeting the data transmission capacity demand for high-speed growth.Methods The seven-core erbium-doped fibre was prepared by the drilling method.Firstly,seven identical erbium-doped preforms were prepared based on the modified chemical vapor deposition(MCVD)process and liquid phase doping technology,and then draw and polish them.Secondly,the high purity wove quartz fibre sock was drilled according to designed parameters.This step can accurately control the core arrangement to ensure uniform core spacing of the multicore fiber(MCF)in the drawing process.In the final step,seven prefabricated erbium-doped rods were inserted into the seven-hole casing and placed on the drawing tower for high-temperature drawing,during the preparation of the seven-core erbium-doped fibre.A seven-core erbium-doped fibre amplifier with core pumping was obtained via the fan in/out devices,which couples light between single-core fibre and multi-core fibre and was fabricated by a tapering fibre bundle.However,the insertion loss among each channel of the fan in/out coupler differs sharply,which causes the nonuniformity of the amplification curves of each core.Results and Discussions We successfully fabricate a seven-core erbium-doped fibre with a uniform structure by the drilling method.The cladding diameter and core pitch of the fibre are 150 pm and 41 pm,respectively.At a total signal power of 0 dBm and a pump power of 350 mW,the gain and noise properties versus wavelength are obtained as shown in Fig.4.A 5.5 m seven-core erbium-doped fibre is used in the system.The maximum gain and average gain in the C band(1526-1566 nm)were 17 dB and 14 dB,with the gain difference between different cores less than 5 dB,and the average noise index is less than 6 dB.This erbium-doped fibre meets the requirements for a communication system for amplifier performance.In addition,the gain contains the loss of all passive components,which means the gross gain at both ends of the gain fibre is more than 21 dB.More so,we obtain a small power signal absorption curve at the C band of each core using the amplified spontaneous emission(ASE)source.The gain and noise characteristics are simulated according to the MC-Cumber theory,which shows a good match in comparison with experimental results.For better performance of the multicore erbium-doped fibre amplifier,more work needs to be carried out,such as a clad-pumping scheme with double-cladding fibre,broadband,and high-power erbium-doped fibre with novel doping component and low insertion space division multiplexing(SDM)passive device.Conclusions In this paper,a seven-core erbium-doped fibre,to the best of our knowledge is fabricated for the first time with a China-based MCVD technology combined with drilling.A seven-core erbium-doped fibre amplifier is constructed with core pumping using fan in/out devices.For the signal,a 31 channel C-band DWDM light is used,with a total power of 0 dBm.The gain fibre is pumped by a 980 nm light source with a power of 350 mW.The maximum gain of 17 dB,average noise index of less than 6 dB,and the gain difference between individual fibre cores of less than 5 dB are obtained.Seven channels of signals are amplified simultaneously.After compensating for the passive loss of the whole system,the gain as high as 21 dB is able to meet the commercial application of erbium-doped fiber amplifier(EDFA).The disadvantage lies in the high complexity of the amplification structure system of the core pumping,and thus,the cladding pumping scheme is an effective way to reduce the structural complexity and improve the energy utilisation rate of the future MC-EDFA system.