Polarization maintaining multiple-depth en face optical coherence tomography system using active re-circulation loops in the non-stationary state

Multiple path optical coherence tomography using re-circulating loops has previously been presented as a means of simultaneously acquiring images from multiple depths in multiple imaging channels. The configurations reported so far present the drawback that the strength of the signal from one channel to the next, reduced as the number of circulations increased. A decay of signal of not better than 4 dB from one channel to the next was reported. We present a technique to reduce this attenuation by using polarization maintaining fiber, and modulation of the drive current of the semiconductor optical amplifiers contained in each arm. The effect of these improvements resulted in a decay less than 20 dB from the 1st channel to the 10th channel.