Research On Tunable Erbium-doped Fiber Laser Based On Tapered Fiber Structure

With the increasing demand of the optical fiber communication technology system,the fiber laser based on fiber has been developed in the aspects of reducing the threshold,improving the stability and tuning the wavelength,which has become the focus in the recent years.Compared to tunable semiconductor lasers,the tunable fiber lasers can obtain wide bandwidth,easy tuning,higher power,convenient connection with optical fiber system.This dissertation mainly focuses on the theoretical and experimental investigations on tunable erbium-doped fiber laser.The main contents are as follows:1.The research background,the characteristics and classification of the fiber laser are briefly introduced.Research status at home and abroad is simply introduced.The development prospects of fiber laser are also described.2.This part introduces the basic principle of fiber laser,including light emission and absorption of light and the principle of resonant cavity.Several kinds of optical filters and optical filters used in fiber lasers are analyzed.The basic theory of the all fiber optical filters is studied.3.A switchable dual-wavelength erbium-doped fiber laser(EDFL)based on tapered fiber structure has been demonstrated.By adjustment of the variable optical attenuator(VOA),the laser can be switched between the single-wavelength mode and the dual-wavelength mode.When temperature is applied on the tapered fiber structure filter,the pass-band varies and the wavelength of the output laser shifts correspondingly.When the temperature changes from 30 ? to 180 ?,the wavelength interval is tunable.4.A tunable erbium-doped fiber(EDF)laser with a cascade structure consisted of tapered fiber structure filter and traditional MZI is proposed.The transmission spectrum of tapered fiber structure filter is modulated by the traditional MZI.A stable single-wavelength lasing operation is obtained at 1527.14 nm.Fix the tapered fiber structure on a furnace,when the temperature changes from 30? to 230?,the central wavelength can be tuned within the range of 12.4nm.5.A tunable multiwavelength erbium-doped fiber laser is proposed.The design of a new air cavity F-P structure is used as the fiber filter to generate the multiwavelength lasers.Tapered fiber structure is introduced to suppress the mode competition and increase the side mode suppression ratio.By changing the temperature around the fiber structure the output laser could be tunable.When the temperature increased from 30? to 210?,the output laser is tuned about 10.8nm.