Source And Suppression Of Relative Intensity Noise In Swept-Source OCT System

Optical coherence tomography (OCT) technology and system has become the necessary detection method in the fields of biomedical engineering. Swept-source OCT (SS-OCT) has become various medical detecting application systems with the excellent imaging quality at high speed and high sensitivity, in which the signal to noise ratio (SNR) is one of key technological performances. In this thesis, in order to improve the SNR of SS-OCT system, the performance degradation of the core passive devices in SS-OCT system performance, the methods for suppressing relative intensity noise (RIN) and relative experiments are studied.Firstly, the theoretical model for SS-OCT system considering the wavelength dependence characteristics of the passive optical devices used in the system is presented and derived. The influence factors on SNR of the system are analyzed. Then, the spectral characteristics of the passive components in the system are tested and analyzed in detail. The empirical formula of wavelength dependence for each device is given. The impacts of these devices on the output optical signal of the system are analyzed by simulation, and the result shows the wavelength dependence characteristics of the devices reduce SNR of the SS-OCT system of 7.384dB. Then the approach of dual digital signal SS-OCT system is proposed. Hotelling detection evaluation model for evaluating the output signal of the system is established, by which the digital filter can be realized. The spectral compensation algorithm based on the wavelength dependence of the key components in the system is proposed, and the compensation function curves are obtained by simulation, and the result shows SNR of the SS-OCT system is increased by 7.384dB using the spectral compensation. Finally, an experimental system of dual digital signals SS-OCT based on the all fiber Michelson interferometer is constructed. The dual output digital signals of the system with different output powers from the optical source are measured respectively. The results show that (1) the SNRs are always improved at different output powers of the source by means of the wavelength dependence compensation; (2) under the condition of optical power 0.3mW, the SNR increases 3.271dB,3.695dB without and with the differential operation, respectively; (3) SNR is larger than 29dB when the optical source power is more than 1.2mW. The experimental results are in agreement with the simulation ones, and demonstrate Hotelling detection evaluation model and the spectral compensation method, and the results.