Studies On Linearly-swept Multi-wavelength Parallel Laser Source In Swept-source Optical Coherence Tomography

OCT(optical coherence tomography)is a no-damage,noninvasive and highresolution imaging technology.Among the OCT systems,swept-source OCT(SS-OCT)is a rising one with fast imaging speed,high resolution and strong signal-to-noise ratio.These years,a new type of SS-OCT system,the multi-wavelength SS-OCT has been come up with to break the restriction between the sweeping range and the sweeping speed,which is common in traditional single-wavelength SS-OCT.Meanwhile,the multi-wavelength SS-OCT has the advantages of wide and flat sweeping range,highresolution and so on.In a multi-wavelength SS-OCT system,the performances and parameters of the multi-wavelength swept source define the imaging speed,imaging depth,resolution and linearity of the OCT system,making the multi-wavelength swept source a crucial part of the SS-OCT system.A multi-wavelength swept source designed for multi-wavelength SS-OCT is researched in this dissertation.Employing different types of multi-wavelength seed lasers,multi-wavelength linearly parallel sweeping was achieved.Further,the feasibility of applying multi-wavelength swept lasers to OCT imaging was demonstrated.The major part of this dissertation are listed as follows:1.Studies on theories of the linearly-swept multi-wavelength parallel laser designed for multi-wavelength SS-OCT systemThe theories of collecting spectral information in multi-wavelength SS-OCT systems were theoretically discussed.And the influences of multi-wavelength swept sources' linearity,sweeping speed,sweeping range and sweeping step on SS-OCT systems' imaging characterizations were theoretically analyzed.Then a linearly-swept multi-wavelength parallel laser designed for multi-wavelength SS-OCT system was proposed.Thesis on its method of OCT imaging and its progress of spectral information collection were researched.Its linearly parallel sweeping principles employing various seed lasers were also explained.2.Experimental research on the linearly-swept multi-wavelength parallel laser designed for multi-wavelength SS-OCT systemThree types of linearly-swept multi-wavelength parallel laser sources were experimentally built up and their sweeping output characteristics were researched.Firstly,the multi-wavelength laser using three parallel DFB-LDs as multi-wavelength seed lasers was built.While precisely changing the source's sweeping step by radio frequency,the output laser's linear relationship between frequency and time under different sweeping steps was demonstrated to remain ~1.Then two multi-wavelength swept lasers using FP-LD and multi-wavelength fiber laser as seed lasers were also built respectively.The multi-wavelength swept laser using three parallel DFB-LDs as seed laser was employed to measure the arm length difference of a Mach-Zehnder interferometer.Results of the interference experiments agreed with the actual arm length difference of the interferometer,which preliminarily demonstrated the feasibility of applying multi-wavelength swept lasers and the spectrum stitching method to SSOCT imaging.