Fiber networks and optical switches and "wireless" fiber

[frizzlefry]

I'm trying to learn more about fiber technologies. You guys might be thinking WTF? wireless fiber? Well I'm just amazed at what they are able to do these days.

Wireless fiber in a nutshell is the ability to transmit on gigabit speeds between buildings in a metro area. Basically FDDIs are expensive and difficult to install especially in a metroplitan area. But the most amazing thing that I really want to learn is how they got around the sway between buildings (especailly skyscrapers). I would have never thought of that being an issue but they were able to overcome this. How? Anyone know?

Now what exactly is an optical switch? I know what the definition is but I'm curious as to how it really works. A switch by definition is a physical thing. How would it work optically? Alot of venture capital has been put into this technology but I'm really curious to how it works.

I've been reading up on it a little recently but haven't delved too deeply into the actual workings of it. If anyone can shed some light on this subject matter I would greatly appreciate it.

 

[bigd480]

from what little i know, an optical switch takes the incoming fiber, and through a process call DWDM (dense wavelength division multiplexing) it puts data from different sources together on an optical fiber, with each signal carried on its own separate light wavelength. Using DWDM, up to 80 (and theoretically more) separate wavelengths or channel of data can be multiplexing into a lightstream transmitted on a single optical fiber. In a system with each channel carrying 2.5 Gbps (billion bits per second), up to 200 billion bits can be delivered a second by the optical fiber.

most of that was cut/paste from this link: whatis.com

 

[spidey07]

<< Wireless fiber in a nutshell is the ability to transmit on gigabit speeds between buildings in a metro area >>



Hmmm, sounds like a marketing term to me. fiber is a physical medium, there is no such thing as wireless fiber optics.

I believe what your referring to is radio or microwave networks? I've used products before that give speeds in excess of 1 Gbs. They do it by combining multiple microwave carriers and muxing them together. Kind of like what gigabit ethernet over copper does with all four pairs.

An optical switch is a router that does not need software to switch frames (that's what a router does...switch frames). The frames come in one side or interface of the opswitch and are by a process of using light and microscopic photo cells or switch is &quot;routed&quot; to another interface.

A DWDM mux is just that...a DWDM mux.

 

[frizzlefry]

Yeah I know fiber is a medium. And I know that wireless fiber is a marketing term. Hence the quotes. But companies like Optical Access and Optical Crossing use free space optics. It's not using RF or microwave. They use 1310 or 1500nm I believe. But the question was regarding how do they deal with building sway? When you're transmitting from rooftop to rooftop on a 30 story building. you're gonna have building sway. And in metro areas, not to mention fog or rain.

How can these obstacles be overcome. I know they do it already. But I'm curios as to the HOW part of it.

 

[CTho9305]

there was an article in Wired about that, i think. most of the solutions involve using REALLY big emitters / receivers (dont know how big) that can handle things like birds and building sway.

 

[spidey07]

Size of the antennae on the receivers? Spread of the laser maybe?

So we're not talking about radio or mwave, were talking laser? Laser has to be line of sight and cannot move around buildings.

 

[Killbat]

If you're talking switches like network components, I think most optical products actually receive the light signal, process it electronically (voltage data, silicon ICs, etc.), and then retransmit the data on an optical line. The only true optical network equipment commercially available as far I know is Lucent's Lambda router. They actually have an array of tiny mirrors on a die that physically switches the light beams. :Q I think that particular router can handle more bandwidth than ANY part of the Internet backbone needs to support as of now.

 

[DAM]

to deal with swaying more than likey has to do with the angle of the transmetir and receiver.


the transmitter might omit at a 10deg angle, whily the reciever captures anything in a 30deg angle. i am sure buildings do not sway more than 20deg (but i could be wrong)

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R/            /T
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R=recevier T=transmitter


dam(like the illustration? drawn to scale too :--))

 

[frizzlefry]

DAM I like that illustration. Where'd u learn to draw like that? I wanna learn!

Killbat Yeah I meant real optical switching like you mentioned. I know they used some sort of mirror but I wasn't sure how they switched. I always figured maybe it was on a galvonometric scanner of some sort. But thanks for the info. I'll check out Lucent then.

Spidey07 Yup it's all line of sight. 2.5gps wireless using lasers. really interesting stuff.

I've worked with lasers for the past 3 years for medical products but I'm trying to get into the networking industry.

Thanks for the info thus far. I'll be reading up on some more hopefully when I have more time. I'll post what I find out in case anyone else is interested.

 

[Rastus]

The only optical switch that is currently deployed right now is made by Corvis. Broadwing (Cincinnati Bell) is running their new network on it. It was turned up a couple months ago.

Nortel, Lucent, Juniper, and Cisco are working on theirs right now, but there aren't any that I know of in the field yet.