Study On Tunable Multiwavelength Erbium-doped Fiber Laser Based On Birefringent Filter Effect

In recent years, the tunable multiwavelength erbium-doped fiber lasers(TMWEDFLs) have attracted much attention of researchers due to the widespread applications in the fields such as high capacity fiber-optic communication, optical detecting and fiber-optic sensing. However, the TMWEDFLs existed already usually depend on the tunability of comb filter to achieve tunable function. And there are still some problems with this kind of TMWEDFLs, such as mono-tuning function or hard to achieve individual control for the multi-parateters which will result in poor controllability to such TMWEDFLs output characteristics. For overcoming the problems above, a novel TMWEDFLs based on the intensity-dependent loss(IDL) effect and fiber-optic birefringent filter effect has been proposed and demonstrated in this work, which can achieve individual tuning fuction for multi-parameter. In addition, in order to optimize the performance of the proposed TMWEDFL, both theoretical analysis and experimental demonstration have been conducted. In this dissertation, the specific work is as follows.Firstly, the model of Lyot birefringent filter with loop structure is built based on the tunability of birefringent filter effect. The transmission characteristics of one-stage Lyot birefringent filter and two-stage Lyot birefringent filter are studied respectively by Jones matrixs method and analysed by numerical simulation.Secondly, a new kind of TMWEDFLs based on the combination of IDL effect induced by a power-symmetric nonlinear optical loop mirror(NOLM) and fiber-optic birefringent filter effect induced by a one stage Loyt birefrengent filter is proposed and demonstrated. The individual tuning function for multi-parameter is achieved based on the complementarity on tuning function between NOLM and Lyot birefringent filter. A continuous fine tuning for the lasing line peak locations within one free spectrum range is achieved by adjusting one-stage Lyot birefringent filter. In addition, a coarse tuning on spectral range can be obtained by adjusting NOLM. The shift of wavelength spectral range could reach 8 nm at most. The number of lasing-line can be controlled by two ways. One is based on adjusting the input light polarization of NOLM, and another is by controlling pump power. The maximum number of lasing-line can up to eighteen. This system keeps a good stability because the wavelength drift is less than 0.06 nm and power fluctuation is lower than 0.35 dB. Nearly no high frequency component in the frequency signal of single wavelength system. On the other hand, if a two-stage Lyot filter is used as a comb filter, the switchable channel-spacing between 0.52 nm,0.78 nm and 1.56 nm also could be achieved. Finally, we realize the individually tuning function of multiple parameters including channel spacing, wavelength number and spectral range.At last, a further study is completed based on the one-stage Lyot birefringent filter. By optimizing laser resonator such as the length of erbium-doped fiber, single-mode fiber and polarization maintaining fiber by turn, the influence on system tuning performance is analyzed. When the length of erbium-doped fiber, single-mode fiber and polarization maintaining fiber is 15 m, 10 km and 8 m, respectively, the multiwavelength sysyem could reach a good output performance.