Available at: https://digitalcommons.calpoly.edu/theses/519
Date of Award
MS in Electrical Engineering
SG-DBR lasers look to solve many problems associated with present OCT sources by being cost effective, smaller in size, more robust, and by operating at faster repetition rates. Swept Source Optical Coherence Tomography (SS-OCT) requires a tunable laser source that exhibits linear frequency sweeps, large frequency spans, and high repetition rates. This work accomplishes this by using four synchronized waveforms sent to the input of a Sampled Grating-Distributed Bragg Reflector (SG-DBR) laser. Three mirrors control the wavelength, while an internal semiconductor optical amplifier controls the laser output power. In dealing with this complicated tuning mechanism, a manual sweep calibration is too time-consuming. This thesis demonstrates an efficient method for automating the calibration of tunable SG-DBR lasers by implementing a gain medium voltage sensing algorithm, as opposed to the previous inefficient manual efforts.
Experimental OCT tests are also performed by utilizing a Mach-Zehnder interferometer as a device under test to verify the accuracy of the laser calibration methodology. The OCT response to a single reflection event is measured over a range of repetition rates. A method to reduce these spurious display responses caused by wavelength stitching imperfections is implemented through a self-generating optical clock.