We propose a novel technique allowing for a substantial increase in th
e 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 o
ptical low-coherence reflectometry techniques. At this extended range,
a reflection sensitivity greater than -80 dB is demonstrated at a pro
be wavelength of 1.55 mum.