Re: transcievers/amplifiers for 150 km fiber run

* Francois Menard · * Sun Oct 12 08:39:12 2008

or you buy some boxes from BTI Photonics that specialize into taking
GigE around the world...
F.
--
François D. Ménard
[email protected]

On 11-Oct-08, at 12:25 PM, Lamar Owen wrote:
On Friday 10 October 2008 14:50:11 Fletcher Kittredge wrote:

We are looking to light a two strand fiber link of about 95 miles (or

150km). It would be worth a lot to us not to have repeaters. We
are

hoping for Gigabit Ethernet. Sonet is possible but a less
attractive

solution. Are there options for this sort of distance? The longest

current link we have is about 65 miles. I understand the
transmission

characteristics of the fiber will effect distance of transmission.

EDFA's can extend your power budget a few dB. Chromatic dispersion
could

still be an issue, though.
Used units that had previous homes in CATV supertrunk applications
should work

well, at least for GigE; up to 120mW is easily possible (I have a
few 65mW

(18.1dBm) EDFA's that came as part of a donation). You hit the
input of the

EDFA with your ZX (1550nm) transceiver's transmit on each end, and
don't look

at the lit fiber or even a reflection of the lit fiber (IOW, wear
laser

safety goggles). And don't even think about looping the EDFA output
back

around without many dB of attenuation.
At this power level you will have to use angle polish connectors at
the EDFA

output (the green SC/SPC or FC/APC ones) or you can burn out the
pump laser

with the reflections.
You also will need to notify your carrier's tech department of the
power level

with which you're lighting that fiber, as even several km down fiber
from an

EDFA is in Class IIIB laser territory.
A bare Cisco ZX GBIC or SFP is rated to light 70km of ordinary
singlemoder

fiber, and up to 100km of either premium (low-loss) or dispersion-
shifted

(which is also low-loss) singlemode fiber. The rated output is
between 0 and

+5dBm (1 and 3.2 mW) for the ZX laser. The link budget is 23dB for
the

standard ZX optics. With a high-gain EDFA outputting 13 more dBm of
power

(20 times the power) you can get a link budget for loss of 36dB;
which could

increase your range 40km, on ordinary fiber.
So, in a nutshell, you'd take the TX from a ZX SFP or GBIC, a few
feet worth

of jumper to an EDFA, and light the fiber (with APC connectors only)
from the

EDFA output. You do this at both ends.