Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Neil White]

Is there really a reason HMA expanded beam wouldn't work specifically with RF over fibre?

I haven't used HMA with RFOF but it has been my experience that RFOF systems are tremendously sensitive to any kind of dirt or contamination on the fiber lens - even when the units are displaying strong levels of optical power received. As I understand it the analogue nature of the conversion between RF and light means that the optical distortions that may be present due to reflections or dirty connectors directly translate into RF noise and IM. Certainly I have experienced systems that have had very high noise floor that has been all but eliminated by thoroughly cleaning all joints in the system.

I suspect that the HMA lens's splitting and combining of the beam would actually introduce more issues in the RFOF link than standard fibre connectors.

[keven mcdonald]

Nice one all - thanks for the advice. Certainly food for thought and worth getting a dialogue with the manufacturers before we go ahead with anything.

Cheers all

[Henry Cohen]

Our Mux22 system is certainly singlemode - it was my understanding that this type of multiplexing was a pretty straightforward "no-go" with multimode fibre. The festival box allows for multimode or singlemode SFPs (or indeed coaxial SDI or madi), but its multiplexed signal is over 2 duplex singlemode connections.

But is it capable of handling RF, which is analog, not digital?. Looking at the Opticore Festival box, it would not work: the electronic interface is wrong.

Is there really a reason HMA expanded beam wouldn't work specifically with RF over fibre? We use HMA with our mux22 units and while I agree they are a little lossier to begin with than regular ferrule connectors, they are much more consistent through their lifespan and given we only have a couple of terminations they have always had loads of headroom above the optical cliff.

My guess is that spreading the light would seriously compromise the integrity of the RF signal.

[Neil White]

Related question : is the digital transmission scheme used by Axient Digital compatible with RFOF transmission? I know of previous issues using RFOF with Sennheiser 9000 digital mics.

[keven mcdonald]

But is it capable of handling RF, which is analog, not digital?. Looking at the Opticore Festival box, it would not work: the electronic interface is wrong.


My guess is that spreading the light would seriously compromise the integrity of the RF signal.

Like i was saying, I was thinking about using the aux tunnel that the festival box has... not one of the SFP interfaces - the 1310nm tunnel that goes straight to the mirrors.

Your other question still stands though. I had never considered "analogue" light transmission existed as like you say we use these systems predominantly with digital systems. I'm guessing the problem is that the light intensity is what is modulated, so you don't have a constantly strong pulse, which I totally understand could create issues with CWDM transmission

[Pete Erskine]

Related question : is the digital transmission scheme used by Axient Digital compatible with RFOF transmission? I know of previous issues using RFOF with Sennheiser 9000 digital mics.

Axient Digital works fine with RFOF.  I have used the RFVenue and wisycom systems with it and it's fine.  RFOF does no digital conversions to the RF - what goes in comes out across almost the entire spectrum.

[Henry Cohen]

Related question : is the digital transmission scheme used by Axient Digital compatible with RFOF transmission? I know of previous issues using RFOF with Sennheiser 9000 digital mics.

"Digital" RF schemes are still analog. The fundamental difference is the "modulation" of the electromagnetic wave is not changing; it's a static spectral mask. Wide band RF carriers are transported over fiber all the time: If there was a problem with a wireless mic system, digital or analog, then something else was amiss.

[Henry Cohen]

Like i was saying, I was thinking about using the aux tunnel that the festival box has... not one of the SFP interfaces - the 1310nm tunnel that goes straight to the mirrors.

If it's just a single mode I/O, and you provide the transceivers, that should work. I would recommend a fiber optic isolator (in addition to the use of angled polished connectors) on the output of the fiber TX, unless it's already built in (usually an extra cost option if available).

[Ike Zimbel]

Related question : is the digital transmission scheme used by Axient Digital compatible with RFOF transmission? I know of previous issues using RFOF with Sennheiser 9000 digital mics.

I am using AD, Sennheiser 9000 and 6000 over the Wisycom set-up I mentioned earlier. Works every night, on a big stadium tour which, AFAIK, I still can't name...

[Neil White]

"Digital" RF schemes are still analog. The fundamental difference is the "modulation" of the electromagnetic wave is not changing; it's a static spectral mask. Wide band RF carriers are transported over fiber all the time: If there was a problem with a wireless mic system, digital or analog, then something else was amiss.

Interesting, sounds like time for a bit of a test build at the warehouse as it’s not something I’ve experienced myself but anecdotal evidence from colleagues was that “it doesn’t work”.

[ProSoundWeb Community]