[time-nuts] Smart fiber-optic cable ( a reference to Hp's smart clock )

Michael Tharp gxti at partiallystapled.com
Mon Feb 4 18:26:01 EST 2013

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.


Here is a demonstration in which fiber is blasted with a heat gun:

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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