Research On Multi-wavelength Erbium-doped Fiber Laser Employing A Large-core Fiber Filter

highWith the large increase of modern communication system capacity and the development of wavelength division multiplexing optical networks,the traditional single-wavelength fiber lasers can not meet the rapidly growing demands in modern communication systems.It is urgent to develop-performance multi-wavelength lasers that can provide stable light sources for multiple channels.At the same time,high-performance multi-wavelength light sources also have broad application prospects in the fields of optical measurement,optical signal processing,spectral analysis,optical sensing and microwave generation.In view of the problems existing in multi-wavelength erbium-doped fiber lasers(MW-EDFLs)and their applications,the research on stable switchable MW-EDFLs and stable L-band tunable MW-EDFLs are carried out by developing novel and high-performance fiber filters.The main research works completed in this thesis are as follows:(1)Based on a segment of large-core fiber,a novel tapered structure large-core fiber Mach-Zehnder interference is proposed.By comparing the frequency domain analysis of filter transmission spectrum using Matlab simulation with the mode calculation results of the large-core fiber simulation model by Comsol software,the multi-mode interference phenomenon of the filter is deeply analyzed.On this basis,the polarization dependence and axial stress characteristics of the proposed filter are experimentally studied.A filter transmission spectrum with minimum insertion loss of 5 dB,extinction ratio of 16 dB and maximum axial strain linear sensitivity of 1.63 pm/??is obtained.(2)A switchable MW-EDFL with a side mode suppression ratio(SMSR)of 50 dB is proposed based on the designed tapered structure large-core fiber filter.By rotating the polarization controller,the arbitrary switching of single-,dual-,triple-and quad-wavelength laser regimes is realized.The experimental study on the equalization and stability of the proposed laser is also carried out.Research results show that the maximum peak power difference in quad-wavelength lasing regime is 3.67 dB,demonstrating a good equalization characteristic.Within half an hour,the wavelength shifts and peak power fluctuations for all obtained laser regimes are less than 0.02 nm and 1.3 dB,respectively,proving that the laser has good stability.In addition,by changing the filter length,a stable quintuple-wavelength laser regime with a SMSR up to 50 dB can also be obtained.(3)A C-and L-band widely tunable MW-EDFL with a SMSR of 55 dB is proposed based on the designed tapered structure large-core fiber filter.By adjusting the axial strain of the filter,two C-and L-band tunable triple-wavelength laser regimes with total tuning range from 1558.71 to 1579.81 nm are realized with SMSR as high as 55 dB.By rotating the polarization controller,tunable single-and dual-wavelength regimes are also achieved with tuning range of 11 nm and 6.23 nm,respectively.The tuning step for each laser regime is compact,all of them are 0.02 nm,and the maximal axial strain linear sensitivity reaches to 1.87 pm/??.Within an hour,the lasing wavelength shifts and peak power fluctuations of each laser regime are less than 0.02 nm and 0.78 dB,respectively,which proves that the laser has good stability.