Hi Missed one important item..
On Feb 4, 2013, at 7:38 PM, Bob Camp <[email protected]> wrote: > Hi > > The transit time of the system is made up (more or less) of: > > Forward: > > 1) electro to optical (likely an LED is involved) > 2) transit over the fiber > 3) optical to electro (probably a photo diode is involved) > Reverse: > 4) electro to optical (likely a different LED is involved) > 5) transit over the same fiber in the opposite direction > 6) optical to electro (likely a different photo diode) > > > For a short link, the variation in 1,3,4 and 6 are often significant compared > to 2 and 5. In a bi-directional transit, there is no need to model 2 or 5. > Since it's the same fiber, it's got the same delay. Any limitation comes from > the fact that you have different "stuff" in 1,3, 4 and 6. > > Yes there are other ways to do this. All that I know cancel out the fiber > delay. If you want to go a bit crazy, you can use multiple pieces of fiber of > matched length and path. For some things having two sets of data can help you > out. > > Bob > > On Feb 4, 2013, at 6:22 PM, Stanley <[email protected]> wrote: > >> My thinking is the temperature has the largest effect on change in delay of >> the cable and more data points would better to predict this change. The >> round trip change in delay would collate with a average of the temperature >> along the cable but not necessary as accurate, think cable buried at >> different depths under asphalt and grass. It is just noise if we can not >> correct for it. >> >> Stanley >> >> >> ----- Original Message ----- From: "Bob Camp" <[email protected]> >> To: "Discussion of precise time and frequency measurement" >> <[email protected]> >> Sent: Monday, February 04, 2013 4:39 PM >> Subject: Re: [time-nuts] Smart fiber-optic cable ( a reference to Hp's >> smartclock ) >> >> >>> Hi >>> >>> Consider that cost to manufacture the cable goes up as you put stuff in it. >>> You not only need sensor packages, you also need to connect them so they >>> can report data. Unless the sensors are optically powered and linked, they >>> would compromise the inherent lighting immunity the fiber provides. >>> >>> It's a *lot* easier to do the same thing with a round trip traverse of the >>> entire optical link. This is already done by at least one supplier of these >>> parts. It may be done by several others as well. >>> >>> Cable delay is not the limiting issue on most short link systems. It's not >>> clear that data rates would be improved by delay modeling. >>> >>> Bob >>> >>> >>> On Feb 4, 2013, at 5:09 PM, Stanley <[email protected]> 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. >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
