The key idea behind our experiment is to assess path length changes by measuring the phase delay of an RF signal that propagates on an optical carrier through the cable. An ultra-stable phase meter compares the arrival phase of an RF signal at the cable output with a stable local reference, capturing any delay variation as a varying phase difference.
A varying phase difference does not automatically point to a length fluctuation; it could also originate from a frequency drift in the RF signal. Therefore, having a correspondingly stable frequency synthesizer is essential in these experiments.
Our Rubidium-controlled OCXO synthesizer locks to a 10-MHz standard, derived from a GPS signal, ensuring excellent short-, medium-, and long-term stability, which is crucial for accurate measurements.
Chromatic dispersion converts any wavelength drift of the carrier into latency variations of the received signal, creating artifacts in measurements that need to be assessed carefully.
[
Collection
]
[
|
...
]