Hi Bob, Sounds interesting -- for what it's worth, I've just learnt some fellow astronomers in Italy (Andrea Maccaferri at INAF's Medicina observatory) have built some PPS/refclk distribution systems based on the Avago fiber parts -- perhaps you might be interested in getting in touch with him...
Thanks (to everyone on this thread) Jack On Mon, 4 May 2015 at 20:19 Bob Stricklin <bstr...@n5brg.com> wrote: > Hi Jack and John, > > I wanted to add an input here….. > > I am working on a 10 MHz GPS slaved reference for my personal use. I am > working with a Analog Devices AD9548 Evaluation board (~$250) , GPS with 1 > PPS, and a ovenized 10 MHz osc. I also plan to distribute this clock and > have considered the Avago fiber product line. One of the older generation > Avago fiber parts should work fine for <$25 per channel. With careful > control of lengths and delays it should be possible to maintain good > phasing between channels. The analog devices chip is <$50 so a custom > solution should be <$500/reference but with considerable development time. > > Bob Stricklin > > > On May 4, 2015, at 10:02 PM, Jack Hickish <jackhick...@gmail.com> wrote: > > Hi John, > > Thanks for the info. I'll add Litelink to my list of suppliers to > investigate. > We have no particular urge to multiplex the signals on to the fiber unless > there's a particularly neat/cheap solution to do that. There's no great > appetite to go custom. We've got about ~30 nodes, and my first stab at > getting an off-the-shelf solution turned up at a few k$ / node, not > including any cleanup electronics. > > Thanks again, > > Jack > > On Mon, 4 May 2015 at 19:25 John Ford <jf...@nrao.edu> wrote: > >> > Hi CASPERites, >> > >> > For HERA, we're looking at distributing timing signals (PPS & 10Mhz ref >> or >> > 500 MHz clock) over O(100m) fibers to various digitization nodes. >> > I figure some folks in CASPERland have experience with this kind of >> > system? >> > Did you use custom RF-over-fiber kit, or off-the-shelf PPS/10MHz >> > solutions? >> > Any words of wisdom/caution to share? >> > >> > Any responses much appreciated! >> >> We have several different schemes for the different signals. Are you >> planning for one fiber per signal per node? or one fiber with the signals >> multiplexed on them? >> >> If the signals are one per signal, you can use some off-the-shelf >> solutions, but they are kind of pricey, and if you have a lot of nodes to >> supply, it might be worth working on something custom. We have used Math >> Associates stuff for this kind of work. Math Associates is now litelink, >> and they tout the affordability of their stuff, so maybe it's >> reasonable... >> >> >> On the 10 MHz, we send the 10 MHz reference over fiber, and at the far end >> use a crystal oscillator locked to the reference to clean up the noise >> from the fiber electronics. This is essential for interferometry, but >> maybe not for single-dish use. >> >> John >> >> > >> > Jack >> > >> >> >> >
