We present a balanced detection method for spectral domain optical coherence tomography (SD-OCT) using a fiberoptic phase shifter. SD-OCT systems typically use a single line scan camera to detect the spectrogram, and noninterfered signals are not excluded from the recorded signal. That limits dynamic range and reduces image quality. Balanced detection methods are used to overcome these problems in swept-source OCT system. Detection using two line scan cameras or multi line camera was proposed to perform the balanced detection in SD-OCT systems. Time delayed replica generated by long optical fiber have been made for that purpose. To induce a phase shift in interference signal, we used a phase shifting interferometry based on an optically tunable phase shifter. The proposed phase shifter can control refractive index variations using the optical power of the pumping beam incident on the rare-earth doped optical fiber. Phase shifts on the optical power represent non-linear behavior and require optimized tuning for proper phase shift. We measured the spectrogram and analyzed the phase change characteristics. By subtracting the phase-shifted replica from the original interference signal, the amplitude of the interference signal is doubled and sensitivity is improved. We prove balanced detection performance based on a phase shifting interferometer.

Date Published: 14 February 2018
PDF: 6 pages
Proc. SPIE 10488, Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications XVIII, 1048819 (14 February 2018); doi: 10.1117/12.2289407

Published in SPIE Proceedings Vol. 10488:
Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications XVIII
Israel Gannot, Editor(s)