Research On Tunable Multi-wavelength Random Distributed Feedback Erbium-doped Fiber Laser

In recent years,random distributed feedback fiber laser(RDFBFL)has attracted much attention due to its simple structure,high reliability,durable in use and high flexibility.The feedback is provided by the distributed feedback mechanism of Rayleigh scattering in the medium.RDFBFL has obtained abundant achievements in the fields of high-power laser,distributed sensing,imaging and so on,and is expected to become a new generation of fiber laser.Based on the basic structure of half-open cavity RDFBFL and the broadband gain characteristic of erbium-doped fiber,3 novel tunable multi-wavelength RDFBFLs are designed by using Sagnac loop filter and Mach-Zehnder interferometer(MZI).The main research contents and achievements of this thesis are as follows.1.A tunable multi-wavelength random distributed feedback(RDFB)erbiumdoped fiber laser based on two-stage Sagnac filter is proposed.The two-stage Sagnac loop is used as a tunable multi-wavelength filter and a mirror to form a half-open cavity.The power conversion efficiency of the laser is about 0.9%.The threshold value of the laser is 30 m W.When the pump power is 180 m W,up to 4 output laser channels can be obtained.The average power and optical signal noise ratio(OSNR)of multiple laser channels can reach-8.79 d Bm and 34.5d B.In the case of 180 m W pump,the number of output laser channels can be adjusted from 1 to 4 by adjusting the angle of the polarization controller(PC)in the two-stage Sagnac loop.2.A tunable multi-wavelength RDFB erbium-doped fiber laser based on dual-pass MZI is proposed.A dual-pass MZI is used as a tunable multi-wavelength filter and a mirror to form a half-open cavity.The power conversion efficiency of the laser is about2%.The threshold value of the laser is 40 m W.When the pump power increases from60 m W to 350 m W,the number of output laser channels increases from 3 to 7,respectively.Under the condition of 150 m W pump power and 5 output laser channels,the average power and OSNR of the output laser channels can reach-9d Bm and 35.9d B.In the case of 250 m W pump power,the output multi-wavelength laser channels shift to short wavelength by 0.7 nm as the voltage on the piezoelectric ceramic increases from1 V to 5V.3.A tunable multi-wavelength RDFB erbium-doped fiber laser based on a composed filter is proposed.The composed filter consists of a Sagnac loop filter and a dual-pass MZI.In this structure,the composed filter is used as tunable multi-wavelength filter as well as a mirror to form a half-open cavity.The power conversion efficiency of the laser is about 1%.The threshold of the laser is 50 m W.When the pump power is220 m W and the angle of PC in Sagnac loop filter is adjusted,the number of laser channels in the spectrum can be adjusted from 2 to 6.The average output power and ONSR of laser channels can reach-9d Bm and 35.4d B.Under the pump power of220 m W,the angle of PC in Sagnac loop is tuned twice,and the 3 laser channels in the spectrum move 1nm simultaneously to the longer wavelength direction respectively.