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Radio over Fiber Optic

Doing some research to see if products are available to use Fiber Optic for an antenna feed line. I've found this solution from Broadcom but it doesn't cover VLF/HF.
https://docs.broadcom.com/docs/AV02-3184EN
https://www.digikey.com/catalog/en/partgroup/afbr-2310z/40195

So any recommendations of existing products that would do this similar to the above devices?
Ron
KA7U

Comments

  • According to what I read the LED transmitters are limited to about 10MHz for the blue lights and maybe 5MHz for the Red, so a laser system is needed to directly modulate radio frequency. I think the problem with the transmitter/receiver pair in my links above is not the laser but the built in RF amplifier that drives the laser. If I can find a laser with the RF input pins so that it can be fed RF externally to modulate it, then DC-60MHz or on up to microwave should be possible. I'll keep looking for a suitable low cost product.
    Ron - KA7U
  • Hi Ron,

    I think you may have a problems trying to find an off-the shelf product that does what you require.

    I designed a lot of specialist signal distribution systems for my last employer (before I retired) and we had quite a comprehensive analogue RF over fibre network, that carried all sorts of test signals between various labs. We had some special units made for us to carry some of the lower frequency signals, but they were very expensive (at the time) and not particularly reliable as the biasing on the TX laser diodes caused them to fail earlier than they should have done.

    At LF/MF/HF a lot of the laser diode transmitters / receivers also have problems with poor S/N.

    For your application initially thought of using some cheap TOSLINK SPDIF digital audio coax to fibre transmitter /receiver modules, but they are not analogue.

    It could be that Analogue (Analog) Video over fibre (CCTV) units may work, many of these are only specified up to 10MHz but if you can get hold of a cheap pair it may be possible to remove the low pass filters and further extend frequency coverage.

    You can also get hold of professional Analogue HD video over fibre modules, but these are very expensive.

    There are also RF over Fibre RFoF modules which are used for radio communication and radio / TV distribution purposes, but these tend to have a LF limit of 50MHz even though they may go up to several GHz at the HF end. However even the cheap ones are still relatively expensive.

    https://www.gionlineshop.com/Downloads/RF Optical Link - 03.pdf

    You could upconvert to VHF and then back down again, but that adds further problems.

    What is your plan ? There may be easier ways to do it :-)

    Regards,

    Martin - G8JNJ
  • edited September 2018
    Martin,
    K7RHB asked me to consider RF over Fiber as an antenna to receiver line. We talked it over and thought it might be worth investigating and if feasible, testing it out to see if any improvement over coax and twisted pair could be realized. K7RHB was thinking plastic fiber would be the medium to use, but as I've been reading and looking at data sheets for existing products, it looks like single mode is more feasible. So it is in the talking stage, gathering information, and trying to understand what the technology is and how to use it.

    This brochure / datasheet is the latest teaser, but comes without order info or pricing.
    https://speag.swiss/assets/downloads/speagflyers/1504TDSRFoF1P.pdf

    Ron - KA7U
  • Something I see as a potential market - more modular radio kit.
    For example RX front end with optical standard IP network connection back to the rig, or for QRP systems complete "QRP rig in a can" (mast mounted), with optical interface back to the shack.
    I know I'd still need DC at the antenna end but where anyone has only 5W to play with having it right at the antenna feed point (even elevated) would make the most of it.
    Where to feed the optical cable? feed it along your radiating wire if need be.

    Here being bathed in QRM and the limit of my "get it away from the house" at about 30ft (9m) I see every bit of copper as a potential way to inject noise back in. If I had a QRP radio that was waterproof and mast mounted I could concentrate on shielding the DC as main potential pickup, hell with a tube of 18650 batteries I could probably run it physically disconnected from DC feed for hours (or battery for RX, DC for TX).

    I have bought enclosures and network kit with this in mind, I just need the IP based QRP rig that I can loft in a box at the extreme (lol) end of my garden. perhaps some small solar cells to top it up during the day.
    KA7U
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