RF OVER FIBER - what are your experiences? - Page 1
Forum section: electronics / rf-microwave

author: PETER ERSKINE
author_rank: Newbie
timestamp: March 28, 2019, 01:15:48 am
content: I use a couple of devices to carry broadband RF over fiber. An inexpensive one from RFVENUE for about 3K and a multi channel one from WISYCOM for 20k.Typically I am trying to get UHF and VHF reception from far away (>300' and <2000')What other devices are there? I am not particularly interested in component level parts, just off the shelf devices.This is a pix of the RFVENUE device:

author: coppercone2
author_rank: Super Contributor
timestamp: March 28, 2019, 02:04:29 am
content: Is this for commercial use?For home use, at those prices, would it not be more cost effective to demodulate the signal at the antenna and transmit the lower frequency demodulated stuff?How much do these things go for second hand? What is the life time of the optical section?Compared to a LME400 for 1000 feet thats going to be ~20dB loss. Did you look at various coax options to see if there is a acceptable cheap solution?https://www.timesmicrowave.com/calculator/?Product=LMR-600&RunLength=1000&Frequency=5001000$/dB seems like alot. How does SNR compare from a LNA to regain loss vs the Optical solution? I think you need to evaluate the benefit vs your exact wiring run size to see how much better your signal quality will be to compare with amplification losses with good coaxial cable.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: March 28, 2019, 09:23:21 am
content: Quote from: coppercone2 on March 28, 2019, 02:04:29 amDepends on what you are doing - if you have line-of-sight, it might be easier still to up-convert to higher carrier and use high-gain antennas to get a point-to-point link.These RF-over-fiber solutions are also gaining interest in 5G, where you could do complex modulation processing at the bottom of the tower, and then only have an optical-to-RF converter and an amplifier near the antenna. Also for larger scale solutions, like a single point in the block where all the RF processing is done, and then fiber distributes it all around the city block to nano-cells.I don't have any details as I work on different solutions, but as these are 'competitors' to what I do for a living I would be interested in any information shared here. Generally these optical solutions all suffer from the same drawback: doing coherent optical requires high cost components, and optical fiber is a pain to run and terminate, and expensive. They are also very sensitive - bit of dust or condensation or air-gap and your SNR is just gone. We are talking about a few micrometers or less in alignment error.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 28, 2019, 10:19:23 am
content: I hat a the same Problem but with different Signals.1) Sat. I choose an SAT -> IP Device from a German Company (who have me Discount for trial). Behind that Box I put an Fiber Media Converter.2) For SDR Stuff I got this:https://www.icronshop.com/fibre-usb-extenders/icron-raven-3124Mine hat some bad solder joint I guess (when the Temp drop under 10c the lost the connection between each other). The Works perfect with the "narrow" SDR with 2Mhz Bandwith. A HackRF need sadly enough to much band with.

author: Yansi
author_rank: Super Contributor
timestamp: March 28, 2019, 10:36:24 am
content: Quote from: Lord of nothing on March 28, 2019, 10:19:23 amStrongly doubt it, the converter thingy would have to be very very slow otherwise. They claim even USB 3.1, I doubt hackRF even uses one (likely just USB 2.0 in HS mode - nowhere close to 3.1 speeds). The problem may be elsewhere.//EDIT: Confirmed, HackRF uses Hi-Speed USB 2.0.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 28, 2019, 10:46:43 am
content: quite all of my Pc are to slow for the HackRF just my i7 Thinkpad work without any problem.I had to send it back because the make trouble when the Temp was falling.The company dont know what happened so I had to send it to Canada (bought from UK) and the will check it.

author: coppercone2
author_rank: Super Contributor
timestamp: March 28, 2019, 08:34:18 pm
content: Quote from: TheUnnamedNewbie on March 28, 2019, 09:23:21 amThat is a good idea so long you accomodate a rain fade budget

author: hagster
author_rank: Frequent Contributor
timestamp: March 28, 2019, 11:14:05 pm
content: It might be worth getting prices from ViaLite also.If it matters for your application, make sure you look into the linearity and dynamic range of the various systems.

author: PETER ERSKINE
author_rank: Newbie
timestamp: March 29, 2019, 03:43:10 am
content: These are for professional use. Typically the cable route is hard or the distance is long which precluded LMR400. A lot of times the house has fiber but no RF installed. I use it on the Macy's Parade for wireless mics. Th RX is located at the FOH position near the performing area on 34th street. However the mics must work around the corner on 6th ave as the floats approach and the only way to connect is via fiber provided by Verizon under the streets.On another show we had a 10 watt 460MHZ band repeater and 5000' away the TX could still be heard but radios couldn't hit the repeater so we put second antenna there on RFOF.

author: ogden
author_rank: Super Contributor
timestamp: March 29, 2019, 01:16:36 pm
content: Quote from: PETER ERSKINE on March 29, 2019, 03:43:10 amWhat if you put receivers next to antenna and runaudio over IP? I think IP circuits may be less expensive than dark fiber and IP solution may pay off quickly, not to mention that it is way more flexible.

author: dmills
author_rank: Super Contributor
timestamp: March 29, 2019, 03:20:35 pm
content: Low latency AOIP works just fine AS LONG AS YOU CONTROL THE NETWORK!Basically AES67/2110-30 (Same thing pretty much) needs reliable UDP delivery over a multicast aware network, with defined maximum amounts of buffering. If you have that it does just fine (Well providing the switches are PTP aware or sufficiently low latency), but trying it over a public packet switched network?Problematic at the latencies I would want for a live show.Give me a pile of Arista 7150s and fibre and I can cart almost unlimited amounts of audio around and it will all be in sync, with latencies in the few ms region (And the SAME latency to all end points), but I would not try that over the public network.Dante is NOT better in this regard.Of course if you don't need low latency then the game changes.Regards, Dan.

author: ogden
author_rank: Super Contributor
timestamp: March 29, 2019, 06:48:53 pm
content: Quote from: dmills on March 29, 2019, 03:20:35 pmArista for voip? LOL. I'm afraid that while typing your internet search query, you confused stock exchange with TV/radio studio. When you want to replace dark fiber withEthernet/IP circuityou obviously don't use public network- you look for carrier grade Metro Ethernet. Obviously you shall look for company which can not only offer strict SLA, but deliver it as well. There are loads of Carrier Grade Ethernet providers in Manhattan area.

author: coppercone2
author_rank: Super Contributor
timestamp: March 30, 2019, 02:08:52 am
content: the only thing, i wonder if someone would try to troll a wifi network during a parade with a DOSI would want wired.

author: dmills
author_rank: Super Contributor
timestamp: March 30, 2019, 12:27:21 pm
content: Quote from: ogden on March 29, 2019, 06:48:53 pmNo internet searches necessary, there is a 7124 in my broadcast toys rack, with a Embrionix Encap to get from SDI to IP (2110 or 2022-6) and some IP capable kit from work.My day job is designing equipment for TV studios and trucks, and yes modern TV production will absolutely use the 7150s and there more modern brethren from Arista, Melanox or Cisco. A single 4k60 ST2110 essence is over 10Gb/s even a mundane 1080P60 feed is ~3Gb/s.This is not compressed domain stuff, but compressed domain is a pain in the arse in a production context where you may be wanting to key off croma or suchlike. In the live production game the cost of even a very quick switch is small compared to the costs of a old school SDI switcher once you get above a few hundred sources or dests, and that trasistion point is getting smaller fast.The new BBC Wales facility for example is an IP infrastructure built as a leaf and spine network on 100Gb links, and IIRC NEPs OBZ is a Grass Valley/Cisco infrastructure in a truck.For audio only (as opposed to audio tightly synced with video), Dante or Ravenna (Basically AES67) over the MAN might be ok, but that is a high stakes game on a big event.Yep, the switch companies developed a lot of this stuff for the HFT crowd, but you better believe broadcast is not afraid to leverage the tech, our needs are close enough (Actually the early low latency switches for HFT borrowed experience from the broadcast SDI switcher game where precisely timed near zero latency switching was a hard requirement).Regards, Dan.

author: PETER ERSKINE
author_rank: Newbie
timestamp: March 30, 2019, 06:24:23 pm
content: Quote from: ogden on March 29, 2019, 01:16:36 pmTypically RFOF is used for additional antennas. For instance for the New Years celebration in Times square, wireless Mics and IFB are required to work from 42nd street up to 48th street and to the top of the Ball tower. Every block has local RX antennas both for Wireless mics and Intercom (Clear-Com Freespeak) All of these are run with fiber.

author: dmills
author_rank: Super Contributor
timestamp: March 30, 2019, 06:42:37 pm
content: That is a NASTY RF environment as well, probably why so many rx aerials are needed. Production audio usually lives in between TV channels, and NY is not short of high powered transmitters.The usual trap with RF over fibre (Really over anything except copper) is the dynamic range which is generally smaller then that of a really good receiver because the RF->Fibre box usually lacks the kind of filtering that a good cavity or stub preselector can buy you.It is a solution to a specific problem, but is not really generally applicable outside of that specific problem space.Regards, Dan.

author: PETER ERSKINE
author_rank: Newbie
timestamp: March 31, 2019, 01:02:18 am
content: Quote from: dmills on March 30, 2019, 06:42:37 pmThe wisycom system has fully programmable HP, LP, Notch filters on each input. Their actual dynamic range is much more than most wireless Rx.The system has 2 channel in each direction which allows for IFB TX as well. Their MPA221 power amp has clever multi amp Parallel/series configuration which eliminates any Intermod creation when amplifying the broadband Max 0 dBM fiber signalThe RFVENUE system has no built in filtering and has higher noise floor but for RX of dozens of channels it is fine. RFVENUE does not do TX.I am interested in any other systems which are out there

author: dillonjerry
author_rank: Newbie
timestamp: October 11, 2022, 07:03:42 pm
content: You mentioned in bold you were interested in any other systems out there. I have a background in fiber optics that goes back almost two decades now. I've worked in fiber applications for broadcast, government, cellular, and military applications.The biggest issue with RF over fiber for people that are not familiar with fiber is the noise. RF over fiber will always have a high noise floor due to noise introduced by the lasers. This is a problem with physics, not a particular manufacturer. The typical solution to dealing with this is to had higher gain to the front end via an LNA, and then attenuate back down after optical transport if needed. This maximizes the SNR as much as possible. There are two types of RF over fiber systems - direct modulation and external modulation. With direct modulation, an incoming RF signal is used to directly drive the bias circuit of a laser diode and the signal is amplitude modulated on the optical output. External modulation systems use a crystal that varies in it's opacity based on a voltage. A constant output laser is shined through this device, and the incoming signal AM modulates the output by varying how much light can pass through the crystal.I see a lot of wireless microphone applications for RFoF where a bunch of remote antennas get positioned around a venue, and all the fibers lead back to a central location. Most applications this is one directional, with only optical transmitters being used by the antennas. I have personally worked on a lot of these systems for large theme parks. These wireless mike Distributed Antenna Systems (DAS) are becoming more and more popular. In the cellular markets fiber DAS systems are getting more and more common. I worked on a large downtown distribution for the largest city in Arizona, and all of their cellular radios for several city blocks are now co-located in a single room. This allows easier management because cellular operators only have to access one secured location.I've worked with several equipment manufacturers throughout the years. You don't always get what you pay for. A lot of companies will outsource their production and manufacturing, and are doing little more than slapping a new sticker on OEM manufactured gear from China. I've never personally handled the Wisycom equipment, but it looks nice. Seems like they have some good RF engineering support. I have handled RFVenue gear, and it's reasonably made for the price. Some of the other gear I've handled includes equipment from Optical Zonu, Thor Fiber, Vialite, RF Optic, Foxcomm - and probably several more I am forgetting. Optical Zonu is the company that I have the most familiarity with (www.opticalzonu.com). I have been to their production facility in Los Angeles, and their RF engineering team was incredibly helpful in several different projects I worked on. Since they manufacture here in the states, they are able to modify existing COTS equipment for individual applications where the requirements might vary. They have some solutions that don't exist anywhere else, like Iridium Satellite Phone over fiber systems, and DirecTV over fiber. Zonu is who I reach out to when I have an application that hasn't been done before.RF over fiber is a complicated discipline that requires expertise in both fiber optics and RF to be implemented successfully. The primary benefit is the low attenuation over fiber cable vs coax. This loss is literally measured in fractions of a dB per kilometer. Its that low. If you need to transport RF over fiber you need to find a partner that knows what they are doing. Most of the time it can be done well, but a lot of different parameters need to be taken into account. I've gone on for too long now, if anyone has any questions let me know.

author: trash
author_rank: Contributor
timestamp: October 28, 2022, 07:59:23 am
content: It's been a long time since I worked with such a system but it was a commercial one and not that expensive 20 years ago. It brought the whole band pass of an L band satellite IFL down on fibre. It was also a two way system so we would up convert the 70 and 140MHz IF from the satellite modems up to L band and then combine them and transmit that via a dark fibre across town to a location to a remote dish. From there it was converted from fibre back to L band coax and then upconverted to C or ku band and transmitted.The receive path was the same in reverse. I don't remember haven't any noise or conversion issues with the system and it worked really well over about 10km of single mode fibre. I suspect had I looked I might have not been so impressed. The system was just a black box to me at the time. It just worked and I never had to worry about it.I did pick up a similar unit surplus many years later which I still have but have never got around to using. It's one of those projects that is waiting for an application.

author: Lord of nothing
author_rank: Super Contributor
timestamp: October 28, 2022, 09:14:07 am
content: As I mention it somewhere here before I use an USB over Fiber Box. One from China the other is from Canada. Both work perfect. Before someone argue yes it is USB over Fiber not the other way around. There are 2 Box one who the RF Reception HW is pluged in the other side is connect to my Pc and hopefully someday to my Server who the necessary Software run.