Research On Fabrication And Amplification Performance Of Erbium-Ytterbium Co-Doped Fiber

The 1.5μm fiber laser has the advantages of human eye safety,long detection distance and strong anti-interference ability.It has gradually become an important laser light source for technologies such as lidar,ranging and wind measurement,space optical communication and optical fiber sensing.Therefore,it has attracted extensive attention in scientific research and industry.As an important gain material of 1.5μm fiber laser,erbium-ytterbium co-doped fiber is the key to realize high power,high energy and high beam quality laser output in the 1.5μm.This dissertation focused on the preparation and amplification performance of erbium-ytterbium co-doped fiber,and high power,high efficiency 1550 nm laser output and extended L-band broadband amplification were realized.The main research contents of this paper are as follows:In this paper,the preparation process of erbium-ytterbium co-doped preform based on MCVD was studied.By adopting reverse deposition,adjusting the POCl₃/Si Cl₄ flow ratio and adjusting the center depression of the refractive index profile,the P₂O₅ content was raised to 13.26 mol%in 10/125 erbium-ytterbium co-doped fiber.A laser test platform was built independently,and a 5 W continuous laser output with a center wavelength of 1550nm was realized,and the slope efficiency reached 41.2%.Large mode field fiber is an important solution to improve the thermal damage threshold,nonlinear threshold and laser damage threshold of optical fiber.In this paper,the theoretical simulation and preparation of pedestal erbium-ytterbium co-doped single-mode fiber and large-mode field fiber were carried out.An optical fiber simulation of the pedestal structure was carried out.And based on multiple deposition processes,erbium-ytterbium co-doped 10/125 single-mode and 25/300 large-mode field fibers were realized,and the core numerical apertures were 0.11 and 0.1,respectively.Based on the self-developed erbium-ytterbium co-doped single-mode fiber,an all-fiber structure laser amplifier was built,which achieved a 6.55 W continuous laser output with a center wavelength of 1550 nm,and the slope efficiency reached 41.8%.Based on the self-developed erbium-ytterbium co-doped single-mode fiber and large-mode field fiber,a two-stage amplification test platform with an all-fiber structure was built,which achieved a CW laser power output of 85.4 W with a center wavelength of 1550 nm,and the slope efficiency reached 48.4%.The polarization-maintaining 1.5μm fiber laser has very important applications in the fields of coherent optical communication,wind radar and optical fiber sensing.The structure simulation of polarization-maintaining fiber was carried out and 10/125 and 25/300polarization-maintaining erbium-ytterbium co-doped fibers were prepared.Among them,the mode birefringence of the 10/128 polarization-maintaining fiber was 1.319×10^-4,and the polarization extinction ratio is 24 d B@5 m.Based on the self-built laser amplification test platform,a 5.8 W continuous laser output with a center wavelength of 1550 nm was realized,the slope efficiency reached 35.96%.The mode birefringence of the 25/300polarization maintaining fiber was 1.55×10^-4,and the polarization extinction ratio was 17d B@5 m.Based on the self-built laser amplification test platform,a 16.8 W laser output with a center wavelength of 1550 nm was realized,and the slope efficiency was reached31.5%.With the upgrading of 5G and the development of cloud computing,Internet of things and short video,the demand for transmission capacity of optical fiber communication system is increasing exponentially,and the existing dense wavelength division multiplexing communication system is facing huge capacity expansion pressure.Extending the gain bandwidth of the amplifier is the most direct and effective solution to increase the transmission capacity of the existing communication system.In this paper,based on erbium-ytterbium co-doped fiber,the related research on extending the L-band amplification bandwidth was carried out.The emission spectrum,signal excited state absorption cross section and fluorescence lifetime of Er³⁺were tested respectively.Based on the self-built extended L-band amplification test platform,the erbium-ytterbium co-doped fiber extended the maximum wavelength of the 20 d B gain of the traditional Er-doped fiber from 1610 nm to 1623 nm,and the maximum noise figure was lower than 6.1 d B.The results showed that erbium-ytterbium co-doped fiber has great potential in expanding L-band gain bandwidth and improving transmission capacity,which provided a new solution to alleviate the"capacity crisis".