Simultaneous Measurement of Flow at Several Depths Using Multiple Active Paths in a Low-Coherence Interferometer

We present a multiple-path scalable configuration that allows the interrogation of an intralipid flow in a vessel at five multiple depths separated by a spatial interval that could be easily adjusted from zero to values less, larger, or much larger than the coherence length of the optical source. The range of flow values measured is accommodated by modifying the difference between the frequencies of signals driving two frequency shifters, each being a part of an active loop placed in each arm of a Mach-Zehnder interferometer.