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 <$500/reference but with considerable development time. Bob Stricklin On May 4, 2015, at 10:02 PM, Jack Hickish <jackhick...@gmail.com<mailto:jackhick...@gmail.com>> wrote: Hi John, Thanks for the info. I'll add Litelink to my list of suppliers to investigate. We have no particular urge to multiplex the signals on to the fiber unless there's a particularly neat/cheap solution to do that. There's no great appetite to go custom. We've got about ~30 nodes, and my first stab at getting an off-the-shelf solution turned up at a few k$ / node, not including any cleanup electronics. Thanks again, Jack On Mon, 4 May 2015 at 19:25 John Ford <jf...@nrao.edu<mailto: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 >
