New high speed fiber optic - Page 1
Forum section: electronics / general

author: vvanders
author_rank: Regular Contributor
timestamp: May 27, 2013, 06:21:05 pm
content: Seen this article popping up on some of my tech sites:http://www.bbc.co.uk/news/science-environment-22656238Supposedly increasing the bandwidth of fiber by sending an inverted signal along with the data. I'm trying to understand why this is being hailed as revolutionary since from the little bit of data I can find it seems to just be a fiber version of a differential pair?

author: madires
author_rank: Super Contributor
timestamp: May 27, 2013, 06:50:28 pm
content: Quote from: vvanders on May 27, 2013, 06:21:05 pmIt's funny that they talk about "noise" instead of distortion. The light distortion increases with the length of the fibre. Therefore the carrier has to place regeneration stations each x km (x is based on the fibre and the technology used). Those regeneration stations need power and may fail. So it would nice to reduce the amount of required stations or get rid of them completely for long fibers, like a submerged seacable. The regen stations are built for a specific bandwidth, i.e. if you upgrade your network you'll have to upgrade them too. If that new method works, seacables would become just a simple fibre connection between two landing sites without any regens in between, less expensive, less problems and a more simple upgrade path.

author: Nermash
author_rank: Frequent Contributor
timestamp: May 28, 2013, 07:17:42 am
content: I see one potentialy pretty big downside to this, and that's the issue of halving the available fiber count in the already laid cable.Operators consider fibers as premium resource, since it is very expensive to lay it, either in ground or at sea bottom. That is why they will turn to wavelength division multiplexing and/or complex modulation schemes to gain more bandwith, rather than increasing the fiber count.

author: Psi
author_rank: Super Contributor
timestamp: May 28, 2013, 09:27:47 am
content: The technology that goes into undersea fiber nodes is quite interesting.They use optical amplifiers to boost the light and re-transmit without ever converting it to an electrical signal.This means they can amplify any wavelength within the supported range. It's a far better approach than doing it electrically with a sensor and laser for each and every wavelength/channel used.Years later when new wavelength laser diodes are discovered (or become cost effective) they can be used to add more channels and increase the bandwidth of the fiber link without needing to replace the undersea nodes.

author: madires
author_rank: Super Contributor
timestamp: May 28, 2013, 01:17:51 pm
content: Quote from: Nermash on May 28, 2013, 07:17:42 amMaybe I missed something in the article, but I think the differential method could be done by two neighboring wavelengths in one fibre.QuoteTrue for undersea fiber but not for burried fiber. Just 10% of the burried fiber is lit!

author: Nermash
author_rank: Frequent Contributor
timestamp: May 28, 2013, 01:39:17 pm
content: I think that dual wavelength differential signaling is possible, but again that halves the available resources, since single mode fibers used in long haul applications have limited range of usable wavelengths / channels.

author: madires
author_rank: Super Contributor
timestamp: May 28, 2013, 02:08:17 pm
content: Quote from: Nermash on May 28, 2013, 01:39:17 pmThat's the trade-off between halfed bandwidth and regen sites or EDFAs. But since regen sites got speed limitations (EDFAs not so much) that limits also the bandwidth of the seacable. Whithout them the carrier may upgrade his systems to higher speeds and more advanced modulation technologies later on (as long as fiber supports it) more easily and less expensive. Therefor I think that a momentary halfed bandwidth is the better way to go. Whithout the regens or EDFAs it's feasable to put more fibers into the cable too :-)