Theoretical Research And Test Analysis Of SOA-based Multi Wavelength Fiber Lasers

Multi-wavelength semiconductor optical amplifier(SOA)fiber lasers have large output band and high output power,and the stable output with multi-longitudinal mode and narrow spacing is achieved easily at room temperature.In addition,the ultra-narrow wavelength spacing can be achieved by using the nonlinear effect of SOA.So,it has great research value and development potential.In this paper,four SOA-based multi-wavelength fiber lasers are designed based on the research and analysis of the relevant theories of multi-wavelength SOA fiber lasers.The main content is as follows:(1)Firstly,the research background and significance of the multi-wavelength SOA fiber laser are introduced.Then,the development history and some progress so far of SOA and SOA-based multi-wavelength fiber laser are introduced.(2)The theory of multi-wavelength SOA fiber laser is studied and analyzed.Firstly,the gain amplifying characteristics and nonlinear effects of SOA are introduced.Then the filter structure and frequency stabilization mechanism of fiber laser are studied and analyzed.(3)A stable multiwavelength SOA fiber laser using a nonlinear fiber loop mirror(NOLM)is designed and experimentally demonstrated.The Lyot–Sagnac loop mirror serves as a wavelength selection device,and the wavelength spacing is determined by the length of the polarization maintaining fiber(PMF).The NOLM serves as a power equalizer to achieve power equalization and improve stability.Moreover,the NOLM can also suppress the mode competition effect within homogenous broadening linewidth of SOA.When 7.3m long PMF is used,multiwavelength output with power equality has been achieved at room temperature,with no obvious power fluctuation.The number of lasing lines is 31 within the 10 dB bandwidth,and the wavelength spacing is 0.63 nm.Finally,narrower wavelength spacing is obtained by increasing the length of the PMF.When 13.5m long PMF is used,the number of lasing lines is 45 within the 10 dB bandwidth,and the wavelength spacing is 0.34 nm.When 71 m long PMF is used,the number of lasing lines is 149 within the 10 dB bandwidth,and the wavelength spacing is 0.078 nm.(4)A multi-wavelength fiber laser based on nonlinear polarization rotation(NPR)effect of SOA is designed and experimentally demonstrated.Due to the NPR effect of SOA,the intensity-dependent loss(IDL)is induced by the intensity equalizer consisting of SOA,polarization controller(PC)and polarization-dependent isolators(PDI)to suppress mode competition effect within homogenous broadening linewidth of SOA.The number of lasing lines is 35 with wavelength spacing of 0.63 nm in the range of 1524nm?1546nm.In addition,wavelength tuning in the 12 nm range is achieved by adjusting the PC.Finally,increasing the length of PMF can achieve multi-wavelength output with smaller wavelength spacing.(5)A multi-wavelength SOA fiber laser based on NPR effect and NOLM is designed and experimentally demonstrated.Due to inhomogeneous broadening and NPR effect of SOA,the SOA is used as the primary gain medium,which allows to achieve stable multi-wavelength output with ultra-narrow wavelength spacing.The combination of PC-SOA-PC-polarizer and NOLM serve as the intensity equalizer for inducing IDL to suppress mode competition effect.The Lyot–Sagnac loop mirror serves as a wavelength selection device.When the length of PMF is 71 m,the number of lasing lines is up to 184 with wavelength spacing of 0.08 nm within 10 dB.The side mode suppression ratio(SMSR)is up to 22 dB.Finally,the length of PMF is changed to 7.3m and 13.5m to obtain stable multi-wavelength output with wavelength spacing of 0.63 nm and 0.33 nm,and the number of lasers is 21 and 40 respectively.(6)A wavelength-number-tunable multi-wavelength SOA fiber laser incorporating a double pass Mach–Zehnder interferometer(MZI)is designed and experimentally demonstrated.The double pass MZI serves as the wavelength selection device.Similarly,the PC-SOA-PC-polarizer combined with NOLM to suppress mode competition effect within homogenous broadening linewidth of SOA.In addition,the degree of IDL can be controlled by adjusting PCs for the purpose of tuning the number of wavelengths.Stable multiwavelength output with power equality have been achieved at room temperature,which have no obvious power fluctuation.The wavelength spacing is as small as0.081 nm,and the number of lasing lines can be tuned from 168 to 250.