4 ms·

Photonics engineer here: DAS isn’t sensitive or spatially accurate enough to eavesdrop like that. Also, fibre is very rarely to the home. Normally it’s to a con

by binbag 5y ago

Photonics engineer here: DAS isn’t sensitive or spatially accurate enough to eavesdrop like that. Also, fibre is very rarely to the home. Normally it’s to a connection box just outside the property and then co-ax to the modem. Lastly, fibre telecoms uses lots of repeaters and switches that DAS can’t see past (needs optical line of sight).

dustfinger 5y ago
Thank you for your insight, those are all great points. The fiber to my home physically runs through my home to a box that is located inside of my home. I didn't realize that most people have the box located outside of their home.
- galangalalgol 5y ago
  I've had fiber into an apartment and into my current home. I don't think it is that unusual.
devit 5y ago
At least in some European countries fiber goes to a GPON terminal in the apartment and then proceeds via Ethernet cable to the home router. I'd guess the co-ax cable is probably a US-only practice.
- stordoff 5y ago
  Virgin Media (UK) use coax. There are some FTTP installs (with coax to the router), but most, as far as I'm aware, use coax for the last leg to the house and from the wall to the router.
  - trollied 5y ago
    I've just had BT FTTP installed, and have a fibre coming into the building. They use GPON. It's wired into a modem ("Optical Network Terminal") that Openreach provide, which then presents the connection via cat5. You then plug your router in, which then uses PPPoE to establish the connection.
- binbag 5y ago
  I was speaking from a UK perspective which, as another commenter says, is mostly co-ax from a point on the pavement. 'Actual' FTTP is coming in now, like HyperOptic, starting with apartment blocks where they can get lots of customers per one new civil engineering job. Most consumer telecoms fibre networks in the UK were laid in the 90s and don't go right to the home. If you're in the lucky situation of having true FTTP, then it's still very unlikely such fibre could be used as a 'microphone' because of the sensitivity and spatial resolution issues. It would also be pretty obvious it was being used because it would probably interfere unless they were very careful with bands. So don't worry, DAS isn't going to be used to listen to your voice. Much easier to do that with your phone!
- jkepler 5y ago
  When I lived in Chattanooga back in 2011, the Electric Power Board offered fiber to the home with an offer of a Gigabyte up and down---hence the original use of Gig city for Chattanooga. I think this was even before Google showcased fiber to the home (was it in Oklahoma City at first? I don't recall) We had to have a router with a fiber port to connect, then Ethernet via cat 5 or WiFi.
- fpoling 5y ago
  By the same principle it should be possible to listen to reflections of the signal propagating in the Ethernet cable that external vibrations introduce. But I guess the noise in the cable is much greater and the frequency of the signal is like 6 order of magnitude smaller making this mostly theoretical.
- dcow 5y ago
  In the US it’s not called fiber if there’s coaxial in the line. If that were true everybody with a cable modem would essentially have fiber.
  - meepmorp 5y ago
    > In the US it’s not called fiber if there’s coaxial in the line My FIOS ONT has a coax out, so that's probably not entirely true.
  - binbag 5y ago
    Yeh that seems to basically be what we call fiber in the UK!
jcims 5y ago
Any idea if the fiber being used for DAS is simultaneously capable of carrying data, or do they pick a strand that is unused?
- binbag 5y ago
  There are a few different flavours of physics you can use for DAS, and they 'use up' different areas of the spectrum. As long as what you want to do for telecoms is using completely separate wavelengths (channels or bands) then yes you can do both. Most DAS providers and users prefer to just use un-used/dark fibres though as it avoids any headaches.
annoyingnoob 5y ago
I have fiber to my home. It runs from the side of my house back to a box at the edge of the park down the street. Inside that box its combined with the feeds to all of my neighbors into a smaller number of runs back to the CO. On the side of my house is a steel utility box that contains an ONT which converts the signal into ethernet. The ethernet cable runs to the other end of my house where I have a router. I guess theoretically it could sense when I operate the garage door and drive in and out, maybe if I take out the trash. But the fiber runs through conduit. And given they way the fibers are multiplexed down the street in practice its hard to infer much from that fiber.
- ta988 5y ago
  Same here, the fiber gets to my home.
- flutas 5y ago
  At least for me, my fiber install is fully inside my house. My ONT (buried inside a BGW-320 that I can't bypass -_-) is fully inside as well. I think a lot of AT&T's setup is going this route as well from what I've read.

by binbag 5y ago

dustfinger 5y ago

Thank you for your insight, those are all great points. The fiber to my home physically runs through my home to a box that is located inside of my home. I didn't realize that most people have the box located outside of their home.

galangalalgol 5y ago
I've had fiber into an apartment and into my current home. I don't think it is that unusual.

devit 5y ago

At least in some European countries fiber goes to a GPON terminal in the apartment and then proceeds via Ethernet cable to the home router. I'd guess the co-ax cable is probably a US-only practice.

stordoff 5y ago
Virgin Media (UK) use coax. There are some FTTP installs (with coax to the router), but most, as far as I'm aware, use coax for the last leg to the house and from the wall to the router.
- trollied 5y ago
  I've just had BT FTTP installed, and have a fibre coming into the building. They use GPON. It's wired into a modem ("Optical Network Terminal") that Openreach provide, which then presents the connection via cat5. You then plug your router in, which then uses PPPoE to establish the connection.
binbag 5y ago
I was speaking from a UK perspective which, as another commenter says, is mostly co-ax from a point on the pavement. 'Actual' FTTP is coming in now, like HyperOptic, starting with apartment blocks where they can get lots of customers per one new civil engineering job. Most consumer telecoms fibre networks in the UK were laid in the 90s and don't go right to the home. If you're in the lucky situation of having true FTTP, then it's still very unlikely such fibre could be used as a 'microphone' because of the sensitivity and spatial resolution issues. It would also be pretty obvious it was being used because it would probably interfere unless they were very careful with bands. So don't worry, DAS isn't going to be used to listen to your voice. Much easier to do that with your phone!
jkepler 5y ago
When I lived in Chattanooga back in 2011, the Electric Power Board offered fiber to the home with an offer of a Gigabyte up and down---hence the original use of Gig city for Chattanooga. I think this was even before Google showcased fiber to the home (was it in Oklahoma City at first? I don't recall) We had to have a router with a fiber port to connect, then Ethernet via cat 5 or WiFi.
fpoling 5y ago
By the same principle it should be possible to listen to reflections of the signal propagating in the Ethernet cable that external vibrations introduce. But I guess the noise in the cable is much greater and the frequency of the signal is like 6 order of magnitude smaller making this mostly theoretical.
dcow 5y ago
In the US it’s not called fiber if there’s coaxial in the line. If that were true everybody with a cable modem would essentially have fiber.
- meepmorp 5y ago
  > In the US it’s not called fiber if there’s coaxial in the line My FIOS ONT has a coax out, so that's probably not entirely true.
- binbag 5y ago
  Yeh that seems to basically be what we call fiber in the UK!

jcims 5y ago

Any idea if the fiber being used for DAS is simultaneously capable of carrying data, or do they pick a strand that is unused?

binbag 5y ago
There are a few different flavours of physics you can use for DAS, and they 'use up' different areas of the spectrum. As long as what you want to do for telecoms is using completely separate wavelengths (channels or bands) then yes you can do both. Most DAS providers and users prefer to just use un-used/dark fibres though as it avoids any headaches.

annoyingnoob 5y ago

I have fiber to my home. It runs from the side of my house back to a box at the edge of the park down the street. Inside that box its combined with the feeds to all of my neighbors into a smaller number of runs back to the CO. On the side of my house is a steel utility box that contains an ONT which converts the signal into ethernet. The ethernet cable runs to the other end of my house where I have a router. I guess theoretically it could sense when I operate the garage door and drive in and out, maybe if I take out the trash. But the fiber runs through conduit. And given they way the fibers are multiplexed down the street in practice its hard to infer much from that fiber.

ta988 5y ago
Same here, the fiber gets to my home.
flutas 5y ago
At least for me, my fiber install is fully inside my house. My ONT (buried inside a BGW-320 that I can't bypass -_-) is fully inside as well. I think a lot of AT&T's setup is going this route as well from what I've read.