A simple intensity noise reduction technique for optical low-coherence reflectometry

It is shown that by attenuating the reference power in an optical low-coherence reflectometry (OLCR) measurement, the reflection sensitivity can be improved, even though, in many other types of optical measurements, sensitivity is improved as optical power is increased. The difference is due to the presence of inherent intensity noise associated with low-coherence sources, which can dominate over shot noise at optical powers that are as low as 1 mu W. A reflection sensitivity of -146 dB is demonstrated using this technique.>