Increased ranging depth in optical frequency domain imaging by frequency encoding.

A technique for increasing the ranging depth in optical frequency domain imaging utilizing frequency encoding is presented. Ranging depth is enhanced by using two interferometer reference arms with different path lengths and independent modulation frequencies (25 and 50 MHz). With this configuration, the sensitivity decreases by 6 dB over a depth range of 7 mm, approximately a threefold improvement over the conventional optical frequency domain imaging technique. We demonstrate that the reference arm frequency separation, tuning speed, center wavelength, and instantaneous coherence length determine the signal-to-cross-talk ratio.