questions about fiber....

[shire]

i work for a company who wants to build an offsite backup data center... new fcc (or some agency) are tryin to impose some rules that a backup center for a company as large as ours must be like 300km away... now we lease dark fiber from some company (i forgot who)... anyways... i was told that after you get passed 100km bad things start happening to the data carried by th fiber... i obviously dont know what im talking about but could someone post some info about long haul fiber...

 

[blahblah99]

Maybe you need a repeater to amplify the light signals? Or a signal conditioner? Not too sure about this one.. maybe someone else can elaborate.

 

[Lynx516]

Sure the range of Fibre is longer than 100km as it is layed over oceans however it is most likly that you need a repeater if it is 100km because light does leak out of them.

 

[zephyrprime]

The need for repeaters totally depends on the particular equipment in use. I remember reading about some transmitter a few years ago that could do 800km but maybe yours is limited to 100km. If you just got the "100km" figure from some guy, you can safely ignore him. Ask the telco technicians of the company you contract with. They'd know.

 

[davesaudio]

simplified:
fibre is not all the same
your terminating equipment must be designed for the fibres in use
things are commonly catagorized metro(local city) and longhaul
you are crossing into the other design area
fibre does not attenuate all light frequencies equally
whole bunch of other things-jitter etc
you need to redesign to handle the losses and determine depending
on the kind of fibre where the repeating equip needs to be
repeating can be done optically or optical-electrical-amp-electrical-optical or.....

 

[Mingon]

And dont let squirrels near your cables :Q replacing 50m of cabling because of those little furry rats is no fun. As for the Q - they need boosting after so long and thats not always possible

 

[spidey07]

Originally posted by: Mingon
And dont let squirrels near your cables :Q replacing 50m of cabling because of those little furry rats is no fun. As for the Q - they need boosting after so long and thats not always possible

The manufacturers make squirrel and gopher proof cable.

 

[Amorphus]

I'l show you gopher proof...

*flips on transformer*
*bzz.... hummmmmmmmmmmmmmm*

lock'n'load.

 

[dym]

Well, depends on wat wavelength you use to transfer data and the receivers. Normally, 100->150 Kms are the distances that we need to put the repeaters. Light does not leak out, it just be absorbed by the un-pureness of the glass, in addition, the dispersion takes place that spread out the signal causing noise... and the unability for the sensors to recover optical to electrical signal.

Repeater is definitely needed. For the 300 kms distance, you probably need 2 repeaters (in case you use the single mode cable and DTFS cable)...

Hope that this can help...

 

[Howard]

Originally posted by: Lynx516
Sure the range of Fibre is longer than 100km as it is layed over oceans however it is most likly that you need a repeater if it is 100km because light does leak out of them.

Leak-proof-ness is part of the fundamental design of fiber.

 

[spidey07]

Originally posted by: Howard

Originally posted by: Lynx516
Sure the range of Fibre is longer than 100km as it is layed over oceans however it is most likly that you need a repeater if it is 100km because light does leak out of them.

Leak-proof-ness is part of the fundamental design of fiber.

But you do lose light directly proportional to distance. Hence the need for a booster or repeater. Heck even the way the fiber is bent or routed can cause significant loss.

 

[Fencer128]

Originally posted by: spidey07

Originally posted by: Howard

Originally posted by: Lynx516
Sure the range of Fibre is longer than 100km as it is layed over oceans however it is most likly that you need a repeater if it is 100km because light does leak out of them.

Leak-proof-ness is part of the fundamental design of fiber.

But you do lose light directly proportional to distance. Hence the need for a booster or repeater. Heck even the way the fiber is bent or routed can cause significant loss.

Okay, so ignoring severe bends, light is not "leaked" out of the fibre - it is absorbed by the core material and spontaneously remitted (scattered). This means you get ~ 0.2dB/km loss at 1.3 and 1.55 microns.

For those who don't speak decibel - that means if you had a 15km long cylinder of the glass that is the core of the fibre and shone a laser through it - the laser light would only be half as bright at the exit of the cylinder as opposed to the entrance! Pretty good!

Hope that clears this up.

Cheers,

Andy

 

[spidey07]

Thanks,

Guess I was trying to point out "you do lose light with distance".

with any given fiber/transmitter/receiver there is always a "loss budget" allowed. You can lose so much light give the receiver, etc. One you are below that threshold data integrity can't be guaranteed.