Spectral domain optical coherence tomography with balanced detection using single line-scan camera and optical delay line

We propose a spectral domain optical coherence tomography (SD-OCT) system that uses a single line-scan detection scheme for balanced detection. Two phase-opposed spectra, generated by two optical fiber couplers, were detected by using a spectrometer with fast optical switching. A 2.69 km optical fiber was introduced to provide a proper time delay to prevent phase errors caused by the difference in measurement time between the two opposing spectra and unstable output voltages for controlling the galvano-scanner. Hence, a phase difference of π was obtained between the spectra over the sample depth without a phase error, which improved sensitivity by approximately 6 dB compared to that of conventional SD-OCT. We directly showed and compared the OCT images before and after applying the proposed balanced detection method in a phantom and in vivo sample.