利用非线性偏振旋转效应的可调谐多波长光纤激光器

提出了一种基于非线性偏振旋转(NPR)效应的可调谐多波长掺铒光纤(EDF)激光器，非线性偏振旋转诱导的强度相关非均匀损耗有效地抑制了均匀加宽增益介质掺铒光纤中的模式竞争,使光纤激光器在室温下产生稳定的多波长输出。其中利用保偏光纤和偏振相关隔离器组成的等效Lyot 双折射光纤滤波器作为波长选择器件，该滤波器可以通过选择合适的双折射光纤长度改变波长间隔，调节偏振控制器改变偏振态实现对波长的精密调谐。实验采用10 m长的保偏光纤(PMF)，得到了波长间隔为0.35 nm、最多17个波长的稳定激光输出,并且实现了输出波长在4 nm范围内的连续可调谐。分别采用10:90、30:70和50:50的输出耦合器，激光信号分别从10%、30%和50%的端口输出，得到了最多17、14和13个波长的输出，其波长功率浮动分别为13 dB、10 dB和7 dB，另外，其最大输出功率分别为-7 dBm、-3 dBm和0 dBm。实验结果表明，输出耦合器输出端比例越大，输出波长就越少，各波长激光输出功率越平坦，且输出功率越高。

Tunable multi-wavelength fiber laser based on nonlinear polarization rotation

A tunable multi-wavelength erbium-doped fiber laser with up to 17 wavelengths was proposed.The intensity-dependent inhomogeneous loss induced by nonlinear polarization rotation(NPR) was applied to mitigate the mode competition caused by the homogeneous gain medium of erbium-doped fiber.Therefore,stable multi-wavelength output was generated at room temperature.In this experiment,a polarization-maintaining fiber(PMF) with a polarization-dependent isolator was used to form an equivalent Lyot birefringent fiber filter.The wavelength spacing could be altered by selecting proper length of the birefringent fiber.In the meantime,the fine tuning of wavelength could be achieved through adjusting polarization controllers(PC).A 10 m length of PMF was inserted into the laser cavity,which resulted in 17 wavelengths output with 0.35 nm wavelength spacing.In addition,a 4 nm tuning range was realized through PCs′ fine tuning.Three different coupling ratio couplers were used.And the laser was output from the small ratio port.The maximum numbers of the output wavelengths were 13,14 and 17 with 7 dB,10 dB and 13 dB fluctuation for 50:50,30:70 and 10:90 couplers,respectively.Besides,the corresponding maximum output power were 0 dBm、-3 dBm and-7 dBm.The results indicate that the output wavelength number is reduced,wavelength spectrum becomes smoother and output power is higher while the output rate of the output coupler is increasing.