dark fiber and sfp distance limitations
rene.avi at gmx.net
Sat Jan 2 08:22:39 CST 2010
On 02.01.2010 13:22, Richard A Steenbergen wrote:
> On Sat, Jan 02, 2010 at 12:35:15PM +0100, Rene Avi wrote:
>> With regards to suggested EDFA amplification tricks and similar: If
>> the requirement is not > 150km at 1G or 80km at 10G/DWDM then I personally
>> strongly disencourage the use of optical amps. 200km / 41dB 1G SFPs
>> are available with costs way below dual EDFAs plus spare, and the
>> chance for the untrained to get eye damages in the process of
>> implementation is far less. So put some laser googles at around 400
>> USD/each to the purchase list. If one decides to do so then add a
>> post-amplifier on each *end* of the fiber link to increase the signal
>> before hitting the receiver, and do not pump in star-wars class laser
>> power at the beginning ;) .
> Depends where you buy your EDFAs, I suspect you could probably get them
> for less than the cost of a single channel of super long reach optics if
> you tried hard enough.
Respectfully disagree here - been there (googled^H^Hmarket research,
talked to both manufactures and resellers for the last year), bought
sample and went through lab tests. Still was unable to find
trustful/working EDFAs near the cost of a pair of 40dB SFPs. 200km SFPs
are even cheaper than 'original' Cisco CWDM-SFPs (standard 80km). We
have them on stock for resale (no commercials intended here), so this
price indication is near real-time ;)
> If you needed to add DWDM later on, and/or
> dispersion compensation for 10G links the EDFAs will be needed anyways,
> so sometimes it just makes sense to solve the problem once with an amp
> rather than trying to solve it on a per-channel basis.
It depends on the requirement - of course.
When Mike is heading for 10G DWDM demand levels he will probably have to
amplify and cromatic-disperse-compensate with 120km G.652 (depending on
the transceiver type) in any case. There are plenty of commercial
solutions available for such spans, or he can try a building-block
My point is to skip EDFAs in a single 1G 120km fiber setup for
commercial aspects, let alone technical reasons (complexity, safety), if
there is no requirement for more bandwidth. IMHO even with multiple 1G
CWDM-style setups, but your mileage may of course vary.
> You're also vastly exagerating the power of what are effectively metro
> reach amps, you're really in no danger of making an eye hazard unless
> you start slapping on ultra long-haul 1500+km transport gear with class
> 3B lasers
In Mikes scenario this might be as a +10dB pre-amp would do the trick
with low power, but a post-amp (+17dB gain with levels around
-20..-30dBm to get some additional power budget) is what I would use if
EDFAs are a stringent requirement.
Most new long-haul transport systems have an automatic power-off feature
for optical protection (e.g.the splice teams after a fiber
cut/disconnect) now because of this.
> (i.e. you're in far more danger from someone with a green
> laser pointer ordered from the Internet :P).
Agreed, but failed to save the whales -
> Remember that 1550nm is
> infrared and very effectively filtered by the human eye, so even a
> +17dBm output EDFA (the max output for most metro systems) is still
> going to be class 1M and effectively safe as long as you don't stare at
> it in a microscope.
Or stare in the beam at 500mW/27dBm without noticing because it is
infrared, and there is no eyelid closure reflex. I tend not to take
chances for my colleagues and me but as common knowledge says it is
everyones own decision to look into the laser with the remaining good eye.
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