| ... | ... | @@ -12,12 +12,18 @@ |
|
|
|
|
|
|
|
### Why the GPS receivers are installed on the surface?
|
|
|
|
|
|
|
|
GPS antenna, cable and receiver are normally characterized as a single
|
|
|
|
entity. It is very convenient to keep an antenna cable length of ~40m,
|
|
|
|
in such a way that the ensemble can be dismounted and sent to
|
|
|
|
calibration by another lab (calibration by METAS) or another lab can
|
|
|
|
bring a traveling GPS to our installation (PTB calibration).
|
|
|
|
|
|
|
|
## Fiber length calibration
|
|
|
|
|
|
|
|
### Why haven't you used fiber reflectometry to measure fiber lengths?
|
|
|
|
|
|
|
|
We avoided using reflectometry to calibrate our delays for the following
|
|
|
|
consideration:
|
|
|
|
considerations:
|
|
|
|
|
|
|
|
1. Commercial reflectometers are known to be accurate at the ~10ns
|
|
|
|
level, whereas we know that our internal delay chain is stable at
|
| ... | ... | |
