My first ever engineering job was at a company that made RF over fibre optic equipment. If you've ever watched satellite TV, or driven through a tunnel and still had GPS signal, the RF signal for that was probably passed over a fibre optic. Since they support frequencies of over 4GHz it's all done totally analogue - the laser amplitude is modulated by the RF itself. Somehow, it works.
Love it. One idea I had to work around the retimer - modulate the TOSLINK signal with OOK (or more generally, FSK) so you have a carrier signal of several MHz that would be in spec for those devices.
In some subway systems, mobile phone reception is implemented by having the RX/TX equipment in some cabinet, and then the tunnel just has dumb antennas that receive/relay the signal they see via fiber optics. That's done because maintenance in the tunnel would be too hard, or there is no space. Berlin has such things. Probably there are some old one sold off at some time?
remote radio heads are really common these days. It's also convenient for antennas on buildings, since it allows you to put a lot of the stuff in a box outside the building on the ground (or inside but more accessible than on the roof), run power and high speed data up to the remote heads and antennas. Means you have to put people on the roof a lot less often, and the distance from RF Frontend to antenna is minimized, which is especially critical for 5G FR2 (which should never have been deployed anyways but that's a different topic)
There's no discrete antennas in the excellent Prague metro coverage but a leaky cable, a coax cable with slits in the sheathing running between the stations
In general in tunnels they use a leaky coaxial cable with cuts in the outer shell, one cable can be used for multiple frequencies at the same time, and this also works in turn's
I was recently looking into this for a thing to help me and my entrepreneurs find the correct fiber. We have our own (as in my employer) fiber network with the longest being 100km. We have almost no WDM, and we have no amplifiers. Everything that is not used is dark fiber and available for lab 🙂 This really got me excited.
Yeah, the thing about YOLOing FM is that the first thing almost any modern FM receiver does (after the frequency discrimination) is to put the input signal into an AGC and then amplify it up until it's a nice square wave so that it can just count the zero crossings. So if your medium is turning it into a square wave for you... it's not really that bad.
In reality, it could be possible to see gravity waves with those signals on optical wires. They shift in time, when a big enough gravity wave hits the earth.
My first ever engineering job was at a company that made RF over fibre optic equipment. If you've ever watched satellite TV, or driven through a tunnel and still had GPS signal, the RF signal for that was probably passed over a fibre optic. Since they support frequencies of over 4GHz it's all done totally analogue - the laser amplitude is modulated by the RF itself. Somehow, it works.
The production of this convention is just flawless...
Kindof disappointed there wasn't a toslink over transatlantic fiberoptic cable section in there.
Love it. One idea I had to work around the retimer - modulate the TOSLINK signal with OOK (or more generally, FSK) so you have a carrier signal of several MHz that would be in spec for those devices.
But then it won't be toslink on the wire anymore, so you can't claim the world record for this
In some subway systems, mobile phone reception is implemented by having the RX/TX equipment in some cabinet, and then the tunnel just has dumb antennas that receive/relay the signal they see via fiber optics. That's done because maintenance in the tunnel would be too hard, or there is no space. Berlin has such things. Probably there are some old one sold off at some time?
remote radio heads are really common these days.
It's also convenient for antennas on buildings, since it allows you to put a lot of the stuff in a box outside the building on the ground (or inside but more accessible than on the roof), run power and high speed data up to the remote heads and antennas. Means you have to put people on the roof a lot less often, and the distance from RF Frontend to antenna is minimized, which is especially critical for 5G FR2 (which should never have been deployed anyways but that's a different topic)
There's no discrete antennas in the excellent Prague metro coverage but a leaky cable, a coax cable with slits in the sheathing running between the stations
In general in tunnels they use a leaky coaxial cable with cuts in the outer shell, one cable can be used for multiple frequencies at the same time, and this also works in turn's
I was recently looking into this for a thing to help me and my entrepreneurs find the correct fiber. We have our own (as in my employer) fiber network with the longest being 100km. We have almost no WDM, and we have no amplifiers. Everything that is not used is dark fiber and available for lab 🙂
This really got me excited.
absolutely wild. I just started digging into this a few weeks ago. I hope he will publish more technical details so I can reproduce this!
Toslink or FM-over-long-haul-fibre loop echo guitar pedal when? Like a tape loop echo, but with flashy lights!
Yeah, the thing about YOLOing FM is that the first thing almost any modern FM receiver does (after the frequency discrimination) is to put the input signal into an AGC and then amplify it up until it's a nice square wave so that it can just count the zero crossings. So if your medium is turning it into a square wave for you... it's not really that bad.
We need to get acoustic couplers working through optic lines!
They make LVDS experimenter boards, I have always wanted to get one to drive an SFP+ but never have the time...
Gravity waves, shift every signal sligtly in time!
RFO: some customer was trying to send toslink over a dark fiber...
That was a funny one!
In reality, it could be possible to see gravity waves with those signals on optical wires. They shift in time, when a big enough gravity wave hits the earth.
So if you really want, you can very easily replace toslink with just fiber and sfp on both ends
PTP master clocks in SFP
I wonder if we could send morse code down the fibre......
Why wonder?
@kreuner11 because Morse code would be the lowest possible bitrate way to send data, so it would be funny.
@@varno no, not sending anything at all would be the lowest possible bitrate of 0 bits per infinite time
@@gorak9000that's cheating though, you have to send _something_ for it to count :D
this is funny
Its 62,5 um not 62um