About 10 MHz Optical Distro
Thanks to all the posters. Especially to Dana - That is exactly what I was looking for - suggestions for parts and/or circuits to do the job. I was originally thinking that I would go with a digital circuit (sine to square to sine), but maybe analog/sinewave would be simpler and perform about as well.
Anyway, I have ordered some of the recommended optical transceivers. We'll see how that works out.
One or two posters mentioned that phase noise and/or thermal stability may be issues. The referenced research papers don't seem to indicate that phase noise is a problem. I don't think that thermal effects will be a big problem for me - I just need to check the phase calibration from time to time. Certainly there are expensive commerical optical clock distribution systems with excellent properties. Maybe the devil is in the details...
My specifical application at the moment is putting several SDRs at diverse antenna locs and feeding the IF via ethernet-converted-to-optical to my computer. I may want to transmit at some point but receiving is all I want to do for now. Still need a way to get a stable ref clock to each radio to provide phase coherence.... I only need 50-60 meters but an optical solution with single mode fibers can go many km if I ever wanted to scale up. Anyway, my plan is to have only power carried by copper.
I don't want to go with coax, twisted pair, or any other copper solution because of high ambient noise levels in my area and a desire to avoid adding to it. Stringing several 100 meters of copper about my yard, carrying 10 MHz clock signals, no matter if the cables are well shielded, doesn't seem like a great idea.
Overkill? Probably.
BTW, I would NEVER try to do something like this with copper Ethernet. Even shielded Ethernet cables (Cat-7 and Cat-8) radiate badly when used for 1-G and 10-G Ethernet.
Thanks again to all!
Jim
On 8/28/21 7:13 PM, AC0XU (Jim) wrote:
Thanks to all the posters. Especially to Dana - That is exactly what I was looking for - suggestions for parts and/or circuits to do the job. I was originally thinking that I would go with a digital circuit (sine to square to sine), but maybe analog/sinewave would be simpler and perform about as well.
Anyway, I have ordered some of the recommended optical transceivers. We'll see how that works out.
One or two posters mentioned that phase noise and/or thermal stability may be issues. The referenced research papers don't seem to indicate that phase noise is a problem. I don't think that thermal effects will be a big problem for me - I just need to check the phase calibration from time to time. Certainly there are expensive commerical optical clock distribution systems with excellent properties. Maybe the devil is in the details...
My specifical application at the moment is putting several SDRs at diverse antenna locs and feeding the IF via ethernet-converted-to-optical to my computer. I may want to transmit at some point but receiving is all I want to do for now. Still need a way to get a stable ref clock to each radio to provide phase coherence.... I only need 50-60 meters but an optical solution with single mode fibers can go many km if I ever wanted to scale up. Anyway, my plan is to have only power carried by copper.
I don't want to go with coax, twisted pair, or any other copper solution because of high ambient noise levels in my area and a desire to avoid adding to it. Stringing several 100 meters of copper about my yard, carrying 10 MHz clock signals, no matter if the cables are well shielded, doesn't seem like a great idea.
This is totally the thing that OVRO LWA dealt with.. Not only is fiber a
LOT cheaper than coax, it solves a lot of problems.
Ethernet to fiber is really cheap ($20 for an endpoint from TP-link )
$20 from newegg
https://www.newegg.com/tp-link-mc100cm/p/N82E16833704015?item=N82E16833704015
I did see the tp link. Pretty amazing. For the group these devices are
pretty useful.
But watch out for the wavelength of the light you typically need matching
fiber. Also note the connectors and get the matching units.
I have no idea how well 1350 light would pass on multimode for 850 nm.
Regards
Paul
WB8TSL
On Sat, Aug 28, 2021 at 11:57 PM Lux, Jim jim@luxfamily.com wrote:
On 8/28/21 7:13 PM, AC0XU (Jim) wrote:
Thanks to all the posters. Especially to Dana - That is exactly what I
was looking for - suggestions for parts and/or circuits to do the job. I
was originally thinking that I would go with a digital circuit (sine to
square to sine), but maybe analog/sinewave would be simpler and perform
about as well.
Anyway, I have ordered some of the recommended optical transceivers.
We'll see how that works out.
One or two posters mentioned that phase noise and/or thermal stability
may be issues. The referenced research papers don't seem to indicate that
phase noise is a problem. I don't think that thermal effects will be a big
problem for me - I just need to check the phase calibration from time to
time. Certainly there are expensive commerical optical clock distribution
systems with excellent properties. Maybe the devil is in the details...
My specifical application at the moment is putting several SDRs at
diverse antenna locs and feeding the IF via ethernet-converted-to-optical
to my computer. I may want to transmit at some point but receiving is all I
want to do for now. Still need a way to get a stable ref clock to each
radio to provide phase coherence.... I only need 50-60 meters but an
optical solution with single mode fibers can go many km if I ever wanted to
scale up. Anyway, my plan is to have only power carried by copper.
I don't want to go with coax, twisted pair, or any other copper solution
because of high ambient noise levels in my area and a desire to avoid
adding to it. Stringing several 100 meters of copper about my yard,
carrying 10 MHz clock signals, no matter if the cables are well shielded,
doesn't seem like a great idea.
This is totally the thing that OVRO LWA dealt with.. Not only is fiber a
LOT cheaper than coax, it solves a lot of problems.
Ethernet to fiber is really cheap ($20 for an endpoint from TP-link )
$20 from newegg
https://www.newegg.com/tp-link-mc100cm/p/N82E16833704015?item=N82E16833704015
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To unsubscribe, go to and follow the instructions there.
Paul is right, and it can be difficult to figure out which cable works well
at a given
wavelength and which connector type is which. A phone conversation with an
applications person at the cable supplier ought to help avoid any of the
traps
At the Arecibo Observatory we had some bad experiences with fiber to
ethernet
converters.
As a class, these things seemed to have problems with UHF/microwave leakage
and often had to be put in properly-shielding enclosures of our own
design. Of
course, being a radio observatory, we might have been a wee bit more
sensitive
to such EMI than would many garden-variety users :-)
Dana
On Sun, Aug 29, 2021 at 9:04 AM paul swed paulswedb@gmail.com wrote:
I did see the tp link. Pretty amazing. For the group these devices are
pretty useful.
But watch out for the wavelength of the light you typically need matching
fiber. Also note the connectors and get the matching units.
I have no idea how well 1350 light would pass on multimode for 850 nm.
Regards
Paul
WB8TSL
On Sat, Aug 28, 2021 at 11:57 PM Lux, Jim jim@luxfamily.com wrote:
On 8/28/21 7:13 PM, AC0XU (Jim) wrote:
Thanks to all the posters. Especially to Dana - That is exactly what I
was looking for - suggestions for parts and/or circuits to do the job. I
was originally thinking that I would go with a digital circuit (sine to
square to sine), but maybe analog/sinewave would be simpler and perform
about as well.
Anyway, I have ordered some of the recommended optical transceivers.
We'll see how that works out.
One or two posters mentioned that phase noise and/or thermal stability
may be issues. The referenced research papers don't seem to indicate that
phase noise is a problem. I don't think that thermal effects will be a
big
problem for me - I just need to check the phase calibration from time to
time. Certainly there are expensive commerical optical clock distribution
systems with excellent properties. Maybe the devil is in the details...
My specifical application at the moment is putting several SDRs at
diverse antenna locs and feeding the IF via ethernet-converted-to-optical
to my computer. I may want to transmit at some point but receiving is
all I
want to do for now. Still need a way to get a stable ref clock to each
radio to provide phase coherence.... I only need 50-60 meters but an
optical solution with single mode fibers can go many km if I ever wanted
to
scale up. Anyway, my plan is to have only power carried by copper.
I don't want to go with coax, twisted pair, or any other copper
solution
because of high ambient noise levels in my area and a desire to avoid
adding to it. Stringing several 100 meters of copper about my yard,
carrying 10 MHz clock signals, no matter if the cables are well shielded,
doesn't seem like a great idea.
This is totally the thing that OVRO LWA dealt with.. Not only is fiber a
LOT cheaper than coax, it solves a lot of problems.
Ethernet to fiber is really cheap ($20 for an endpoint from TP-link )
$20 from newegg
send
an email to time-nuts-leave@lists.febo.com
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Started into white rabbit on fiber recently - one tidbit that was
shared with me: White rabbit typically uses a BIDI over a single fiber
to keep the fiber length (and respective transmit / receive times) as
close as possible
Martin
W2RWJ
On 8/29/2021 10:03 AM, paul swed wrote:
I did see the tp link. Pretty amazing. For the group these devices are
pretty useful.
But watch out for the wavelength of the light you typically need matching
fiber. Also note the connectors and get the matching units.
I have no idea how well 1350 light would pass on multimode for 850 nm.
Regards
Paul
WB8TSL
On Sat, Aug 28, 2021 at 11:57 PM Lux, Jim jim@luxfamily.com wrote:
On 8/28/21 7:13 PM, AC0XU (Jim) wrote:
Thanks to all the posters. Especially to Dana - That is exactly what I
was looking for - suggestions for parts and/or circuits to do the job. I
was originally thinking that I would go with a digital circuit (sine to
square to sine), but maybe analog/sinewave would be simpler and perform
about as well.
Anyway, I have ordered some of the recommended optical transceivers.
We'll see how that works out.
One or two posters mentioned that phase noise and/or thermal stability
may be issues. The referenced research papers don't seem to indicate that
phase noise is a problem. I don't think that thermal effects will be a big
problem for me - I just need to check the phase calibration from time to
time. Certainly there are expensive commerical optical clock distribution
systems with excellent properties. Maybe the devil is in the details...
My specifical application at the moment is putting several SDRs at
diverse antenna locs and feeding the IF via ethernet-converted-to-optical
to my computer. I may want to transmit at some point but receiving is all I
want to do for now. Still need a way to get a stable ref clock to each
radio to provide phase coherence.... I only need 50-60 meters but an
optical solution with single mode fibers can go many km if I ever wanted to
scale up. Anyway, my plan is to have only power carried by copper.
I don't want to go with coax, twisted pair, or any other copper solution
because of high ambient noise levels in my area and a desire to avoid
adding to it. Stringing several 100 meters of copper about my yard,
carrying 10 MHz clock signals, no matter if the cables are well shielded,
doesn't seem like a great idea.This is totally the thing that OVRO LWA dealt with.. Not only is fiber a
LOT cheaper than coax, it solves a lot of problems.Ethernet to fiber is really cheap ($20 for an endpoint from TP-link )
$20 from newegghttps://www.newegg.com/tp-link-mc100cm/p/N82E16833704015?item=N82E16833704015
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
an email to time-nuts-leave@lists.febo.com
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From here
https://forums.xilinx.com/t5/Serial-Transceivers/Sending-10Mhz-clock-over-Fiber/td-p/1026390
They suggest these
*** SNIP ***
what length do you need to send over ?
this sort of stuff is a LOT cheaper and more rugged, and more than
capable of sending 10 MHz clock
Cable
https://uk.farnell.com/broadcom-limited/hfbr-rus100z/cable-fibre-optic-1-fibre/dp/1247714
https://uk.farnell.com/broadcom-limited/hfbr-rus100z/cable-fibre-optic-1-fibre/dp/1247714
Drivers
http://www.farnell.com/datasheets/1812660.pdf?_ga=2.29282815.2110613125.1570030173-2072545025.1569659196
http://www.farnell.com/datasheets/1812660.pdf?_ga=2.29282815.2110613125.1570030173-2072545025.1569659196
and you just drive it with TTL.
*** SNIP ***
Using cheap POF - It seems like 50m is the max for 10MHz
But i think with POF , we should be able to "do connectors at home"
Using 200 μm PCS cable , it seems you could go 120m@50Mbd
But a 100m SC connected fiber cable was "only" like $30 on Aliexpress
They seem a "bit like" the other drivers mentioned , but starts with A
instead of H
CFO
Still timenut beginner
On 8/29/21 12:13 PM, CFO wrote:
From here
https://forums.xilinx.com/t5/Serial-Transceivers/Sending-10Mhz-clock-over-Fiber/td-p/1026390
They suggest these
*** SNIP ***
what length do you need to send over ?
this sort of stuff is a LOT cheaper and more rugged, and more than
capable of sending 10 MHz clock
Cable
https://uk.farnell.com/broadcom-limited/hfbr-rus100z/cable-fibre-optic-1-fibre/dp/1247714
https://uk.farnell.com/broadcom-limited/hfbr-rus100z/cable-fibre-optic-1-fibre/dp/1247714
Drivers
http://www.farnell.com/datasheets/1812660.pdf?_ga=2.29282815.2110613125.1570030173-2072545025.1569659196
http://www.farnell.com/datasheets/1812660.pdf?_ga=2.29282815.2110613125.1570030173-2072545025.1569659196
and you just drive it with TTL.
Yeah, but those are piece parts. What would be nice is if a cheap "box"
could be found - ideally (for 10 MHz) BNC in/out and fiber connector
with a wall wart for power. Maybe this a good idea for a TAPR project if
someone was willing to do the design (!)
There's probably plenty of applications out there in amateur radio land
for a inexpensive RF over optical link with "decent" performance
(defined however).
Hi
Ok so what is “decent” performance?
Is -150 dbc/ Hz “floor” good enough? it is for some stuff ….
Is -130 dbc/ Hz at 10 Hz a requirement?
Is -100 dbc / Hz at 1 Hz the target?
Is 1x10^-12 at 1 second “good enough” ADEV?
How about 1x10^-13 at 10 seconds …..
Keep in mind that these are system floor numbers. The real signal
“as delivered” isn’t going to ever be as good as the system floor.
You could easily move any of those phase numbers 20 db one way or the other.
The ADEV could go up or down by at least two orders of magnitude. The numbers
would still be “decent” by some definitions.
Bob
On Aug 29, 2021, at 3:24 PM, Lux, Jim jim@luxfamily.com wrote:
On 8/29/21 12:13 PM, CFO wrote:
From here
https://forums.xilinx.com/t5/Serial-Transceivers/Sending-10Mhz-clock-over-Fiber/td-p/1026390
They suggest these
*** SNIP ***
what length do you need to send over ?
this sort of stuff is a LOT cheaper and more rugged, and more than capable of sending 10 MHz clock
Cable
https://uk.farnell.com/broadcom-limited/hfbr-rus100z/cable-fibre-optic-1-fibre/dp/1247714 https://uk.farnell.com/broadcom-limited/hfbr-rus100z/cable-fibre-optic-1-fibre/dp/1247714
Drivers
http://www.farnell.com/datasheets/1812660.pdf?_ga=2.29282815.2110613125.1570030173-2072545025.1569659196 http://www.farnell.com/datasheets/1812660.pdf?_ga=2.29282815.2110613125.1570030173-2072545025.1569659196
and you just drive it with TTL.
Yeah, but those are piece parts. What would be nice is if a cheap "box" could be found - ideally (for 10 MHz) BNC in/out and fiber connector with a wall wart for power. Maybe this a good idea for a TAPR project if someone was willing to do the design (!)
There's probably plenty of applications out there in amateur radio land for a inexpensive RF over optical link with "decent" performance (defined however).
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To unsubscribe, go to and follow the instructions there.
On 30/8/21 5:24 am, Lux, Jim wrote:
Yeah, but those are piece parts. What would be nice is if a cheap "box"
could be found - ideally (for 10 MHz) BNC in/out and fiber connector
with a wall wart for power. Maybe this a good idea for a TAPR project if
someone was willing to do the design (!)
You'd do it using an SFP cage, so the actual optics could be swapped in
for standard commercial ones, and generic 1G LR optics should be < US$10
in small quantity by now (they've been much less than that in tray
quantity for at least a decade), and drive 2km easily.
I've done a little design with SFP for a previous (work-ish) project,
and basing it on the redesigned Spectracom 8140 pods I did a few years
ago[1], I could probably knock out a prototype design in an afternoon.
(Quite if I ever will, and when is a different matter)