Study On Tunable Erbium-doped Fiber Laser Based On Superimposed Fiber Gratings

Multi-wavelength, tunable fiber laser has a wide range of applications in areas such as optical communication systems, optical fiber sensing systems, dense wavelength division multiplexing systems, because of it can provide multiple wavelength laser output at the same time, and it can realize single-wavelength, multi-wavelength tunable laser output. Miniaturization and integration of multi-wavelength and tunable fiber laser have become the development trend in the future. SIFG is the grating device with compact size, it have many advantages, such as the flexibility of wavelength interval and reflectance, consistency of temperature and strain response, all these makes it fit for fiber laser integration. So it is important for us to study the tunable Erbium-doped fiber lasers based on SIFG.In the paper, the reflection spectrum characteristics of SIFBG are analized by coupled mode theory, the principle of multi-wavelength linear cavity Erbium-doped fiber laser is studied, and the output characteristics of multi-wavelength, tunable Erbium-doped fiber laser based on SIFBG and CFBG, or based on D-SIFBG are studied in experiments. The main contents of the paper are as follows:Firstly, based on coupled mode theory, on the condition of fiber grating meet resonance coupled, the characteristics of fiber grating and SIFBG are studied in detail, the reflection spectrum of multi-wavelength SIFBG, SIFBG with different bandwidth and SIFBG with different wavelength interval are studied in numerical simulation. The uniformity gain characteristic of Erbium-doped fiber is studied, the important parameters of linear Erbium-doped fiber laser are researched, such as particles number reverse, gain, the threshold value, output power and slope efficiency. The mode competition of Erbium-doped fiber laser and stable oscillation conditions of multi-wavelength Erbium-doped fiber laser are studied.Secondly, the principle of Erbium-doped fiber laser based on Giles model is studied. The fiber laser based on two-wavelength or multi-wavelength SIFBG and CFBG are designed. The output characteristics of switchable and tunable of single and two-wavelength laser based on two-wavelength SIFBG and CFBG, and the output characteristics of switchable and tunable of single, two and three wavelengths laser based on three-wavelength SIFBG and CFBG are studied in experiments, the output laser influenced by pumping power, the length of resonator and other effects are analyzed, the stability of output laser is also analyzed.Thirdly, in order to obtain laser output with narrower line width and high optical signal to noise ratio, two-wavelength D-SIFBG and two-wavelength Erbium-doped D-SIFBG with narrower line width are prepared and used in linear cavity erbium-doped fiber lasers. The output characteristics of fiber laser are studied in experiment, including the output power influenced by pump power and the length of resonance cavity, the stability of the center wavelength and the power of the laser, and the tunable output characteristics.At last, the characteristics of multi-wavelength D-SIFBG are analyzed, the output characteristics of single-wavelength tunable Erbium-doped fiber laser based on multi-wavelength D-SIFBG are researched in experiment, the tunable characteristics and the stability of the laser are analyzed.The characteristics of Erbium-doped fiber laser based on different SIFBGs are studied deeply. It can provide valuable reference for miniaturization and integration of the multi-wavelength, tunable Erbium-doped fiber laser.