Extended-range optical low-coherence reflectometry using a recirculating delay technique

We propose a novel technique allowing for a substantial increase in the distance measurement range for optical low-coherence reflectometry. By introducing a recirculating delay into the interferometer reference path, we achieve a 100 times increase in range compared to previous optical low-coherence reflectometry techniques. At this extended range, a reflection sensitivity greater than -80 dB is demonstrated at a probe wavelength of 1.55 mu m.>