Research On Key Technologies Of High Speed Broadband OCT Swept Source

Optical coherence tomography(OCT)has attracted the attention of scholars in related fields because of its non-radiation and high resolution and it has become a research hot spot.Swept laser source plays an important role in improving the quality of OCT imaging.At the same time,the swept source can also be used for absorption spectrum,accurate measurement of the active medium's gain spectrum and demodulation of the fiber grating.This paper studies a variety of key techniques to improve the sweep range and sweep rate of OCT swept source based on the optical principles such as Fourier domain mode-locking and optical buffering.The main research contents and results of this paper are as follows:(1)The F-P tunable filter driving unit is studied to meet the need of high-speed swept source,which solved the problem of insufficient driving signal power when the conventional function signal generator is working.By studying the displacementvoltage relationship of the internal piezoelectric ceramics of the F-P filter and the spectral characteristics of the actual swept source,a sinusoidal signal is used as a technical method for driving the F-P tunable filter for high-speed scanning.(2)Narrow instantaneous linewidth swept source based on quantum well SOA(QW-SOA)cascade and single quantum dot SOA(QD-SOA)are studied.The SOA and the annular cavity act as a gain medium and a pump source in the system,so the light source belongs to a kind of wavelength tunable laser.All center wavelength of two types of swept source are 1310 nm,both instantaneous linewidth are less than 0.03 nm,the sweep rate is 4 kHz,full width at half maximum(FWHM)are 80 nm and 72 nm,and output optical powers are 20 mW and 8.1 mW,respectively,.both of which have low polarization dependent gain.(3)High-speed swept source based on cascade of QW-SOA and high-speed broadband swept source based on parallel connection of QW-SOA and QD-SOA were studied.The key components and technologies used are the high speed large free spectral range FFP-TF,SOA and Fourier domain mode-locking technology.The scanning rate of both types of swept source are 101 kHz,the sweep range are 95 nm and 110 nm respectively.The spectral width of QW-SOA and QD-SOA in parallel is 318 nm,the optical power are 14.8 mW and 7.8 mW respectively.Both the instantaneous line width are 0.1 nm.(4)Combining the high-speed swept source with the optical buffering device,two types of high-speed swept source based on optical buffering device were designed and developed.We named them high-speed swept source based on buffering device outside the ring cavity and high-speed swept source based on buffering device inside the ring cavity.In the development process,it is particularly necessary to adjust the duty cycle of the swept source.Finally the sweep rate,sweep range,average output optical power and instantaneous line width of high-speed swept source based on buffering device outside the ring cavity are 202 kHz,95 nm,6.3 mW and 0.1 nm respectively.The sweep rate,sweep range,average output optical power and instantaneous line width of highspeed swept source based on buffering device inside the ring cavity are 202 kHz,95 nm,7.5 mW and 0.1 nm respectively.