Research On All-Fiber Wavelength-Swept Laser Source Based On Erbium-Doped Fiber Amplifier

With the rapid development of Swept Source Optical Coherence Tomography(SS-OCT)and fiber-based biosensor,the wavelength-swept laser source with high sweep rate,wide sweep range,narrow instantaneous linewidth and high output power is urgently needed.Meanwhile,owing to the incomparable advantages such as small size,anti-electromagnetic interference and good biocompatibility of fiber laser,the all-fiber wavelength-swept laser source has become a development trend of this technology.For the above requirements,the ring-cavity based wavelength-swept fiber laser and the Fourier domain mode-locked(FDML)fiber laser were theoretically and experimentally studied in this thesis.Moreover,we propose and demonstrate a Fourier domain mode-locked(FDML)fiber laser,based on the non-reciprocity effect of intra-cavity dispersion,which could operate in switchable and single wavelength-swept direction without any additional modulation device.The main contents of this thesis are listed as follows:(1)Based on the basic principles of fiber lasers,the ring-cavity based wavelength-swept fiber laser and FDML fiber laser were studied theoretically.The basic configuration,operation principle and influence factors of performance were researched,as well as the key parameters for evaluating the performance of the swept laser source were discussed.(2)The ring-cavity based wavelength-swept fiber laser based on fiber Fabry-Perot tunable filter(FFP-TF)and erbium-doped fiber amplifier(EDFA)was set up.Using the method of variable analysis,the influence of wavelength sweep rate and sweep range of FFP-TF and pump power on the laser output performance were systematically studied.The experimental results demonstrate that with the increase of wavelength sweep rate and sweep range of FFP-TF,the power density of spectrum and time-domain optical field were reduced significantly,while the increase of pump power could greatly improve the laser performance.Finally,the laser output with central wavelength of 1564.6nm,sweep range of 35.49nm,sweep rate of 2129.4nm/s and sweep frequency of 30Hz was realized.(3)The unidirectional wavelength-swept FDML fiber laser based on controlling the drive signal of FFP-TF was proposed.By analyzing the influence of pump power,sweep range and sweep center wavelength on the laser output performance,it was found that due to the existence of intra-cavity dispersion,the output spectrum of forward wavelength sweeping and backward wavelength sweeping were strikingly different.Further,by using the non-reciprocal effect of intra-cavity dispersion and the controlling of FFP-TF drive signal,the unidirectional wavelength sweeping was achieved without any additional device.The experiment proves that the switching of the unidirectional forward sweep and the unidirectional backward sweep of the laser can be realized via changing the driving parameters of FFP-TF.Specifically,the unidirectional forward sweep lasing was with center wavelength of 1552.7nm,sweep range of25.4nm,wavelength sweep rate of 1.299×10~6nm/s,sweep frequency of 25566.2Hz,instantaneous linewidth of 0.108nm,and the unidirectional backward sweep output was with center wavelength of 1556.3nm,sweep range of 25.6nm,wavelength sweep rate of1.310×10~6nm/s,sweep frequency of 25583.2Hz,instantaneous linewidth of 0.126nm.