The Research On The Fabrication Technique And Amplification Performance Of The Bismuth-doped Fiber

With the rise of big data,internet of things,cloud computing and 5G,the ever-increasing demand for information puts forward higher requirements on the transmission capacity and bandwidth of optical fiber communication systems.Due to the limitation of the 4f narrow band forbidden transition structure of erbium ions,traditional erbium-doped fiber amplifiers can only achieve optical amplification in the limited wavelength range of 1530～1620 nm,covering only a small part of the low-loss transmission window of the optical fiber,with O,E,S,U bands not being fully utilized.Based on this reason,bismuth-doped glass and fiber with 1000～1800 nm ultra-wideband near-infrared fluorescence can be used as a promising gain medium for ultra-wideband fiber amplifiers and lasers,which can not only make up for the shortcomings of traditional rare earth ion doped fiber lasers and amplifiers,but also promote the development and application of optical fiber full-band communications,as well as the further development of ultra-wideband fluorescent light sources,ultra-wideband spectrum measurement,large-capacity optical fiber sensing,and optoelectronic information processing.In this paper,a series of researches have been carried out on the preparation of Bi-doped fiber and its broadband amplification performance.The main contents include:（1）Based on the MCVD reverse deposition technique,thin-walled tubes,liquid phase doping and gas phase compensation were used to optimize the process,and a phosphosilicate matrix bismuth-doped fiber with a P₂O₅content of 28 wt%and a Bi₂O₃content of 0.26 wt%in the core was fabricated.And under the excitation of 532 nm,808nm,and 976 nm pump light,bismuth-doped phosphosilicate fiber could realize ultra-wideband fluorescence in the 1000～1600 nm band.A maximum gain of 9.72 d B at a wavelength of 1442 nm was achieved when bismuth-doped phosphosilicate fiber was pumped by 808 nm laser diode.Besides,a homemade 1348 nm Raman random fiber laser was constructed to pump 2 m long bismuth-doped fiber.The phosphor-silicon-based bismuth-doped fiber had a fluorescence peak wavelength of 1440 nm,a maximum output power of 4.44 W,and a pump conversion efficiency of 11.66%.Compared with silica-based bismuth-doped fiber,bismuth-doped phosphosilicate fiber had better spectral performance,higher output power and pump efficiency,which were beneficial to the further application of bismuth-doped fiber in the wavelength range of 1400～1600 nm.（2）Nanoporous silica glass was prepared by the soda borosilicate glass phase separation technology,and then erbium-bismuth co-doped silica glass was prepared combined with solution doping technology,the optimal doping concentration of which was Er0.1 Bi0.3 Al2.0 mol/L.When erbium-bismuth-aluminum co-doped silica glass was pumped by 793 nm LD with a output power of 5 W,the corresponding fluorescence FWHM was 63 nm.The silica glass rod was drawn into the erbium-bismuth co-doped silica glass fiber by the tube-rod method.Under the excitation of 976 nm laser diode with a pump saturation power of 600 m W,a complete inversion gain coefficient of 20.97 d B/m was achieved at a wavelength of 1536 nm in the fiber.