On 02/04/2013 05:09 PM, Stanley wrote:
If a fiber-optic cable had temperature sensors either installed with or
embedded inside of this could make for better modeling changes in delay making
more accurate transfer of time and frequency possible. With fiber to tower
installs now under way to provide more data at cell towers why not backup GPS
frequency and time transfer with the same medium ? Would this also increase the
data rate of the cable ? That is faster rates due to the better timing
uncertainty.
Take a look at CERN's White Rabbit project. They're doing sub-nanosecond
time transfer over fiber, including compensating for temperature variations.
http://www.ohwr.org/projects/white-rabbit/wiki
Here is a demonstration in which fiber is blasted with a heat gun:
https://www.youtube.com/watch?v=ZSRQEExbdq8
The hardware is rather specialized at the moment but it seems there is
ongoing work on making it more generally available. Certainly if the
telcos were interested they could make it happen, but probably they are not.
There is quite a lot of useful, open-source material coming out of this
project including a VHDL implementation of a Vernier TDC. At some point
I plan to use it to build a high-performance TIC.
-- m. tharp
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