Available at: https://digitalcommons.calpoly.edu/theses/220
Date of Award
MS in Electrical Engineering
Swept Frequency Source Optical Coherence Tomography (OCT) requires high repetition rate and wide spectral width wavelength tunable sources at a low cost. The sampled grating distributed Bragg reflector (SG-DBR) laser provides wide wavelength tuning range while exhibiting a wavelength switching speed that is among the fastest currently available. The SG-DBR laser is used to generate linear frequency ramps with high repetition rates. Since the SG-DBR laser is currently used for the telecommunications industry in high volume, the price of the system is much lower than current OCT sources. Therefore the SG-DBR laser provides a practical solution for Swept Source OCT.
Four synchronized waveforms sent to the inputs of the laser control the linear frequency ramp. Three of the waveforms control the output frequency, while the fourth waveform controls the output amplifier of the laser to keep the output power stable. Two SG-DBR lasers with overlapping wavelength coverage are also concatenated to increase the bandwidth of the swept frequency source.
The linear ramp stitching points in the frequency ramps are investigated and methods are outlined to reduce them. Finally, experimental OCT tests are performed using the swept frequency sources created to analyze the linearity of our sources. From these test results, an evaluation can be made on the specifications and capabilities of the swept frequency sources and analyze their value for OCT applications.