Optical fiber question

Anton Kapela tkapela at gmail.com
Thu Dec 10 16:52:02 CST 2009


Wanted to add something to this and clarify/correct a few points:

> Plus, while I'm sure someone in a lab has done it, you really don't run DWDM
> over multimode fiber - I'd second the opinion of it's cheap enough, go for
> the single mode and get the most flexibility in your options possible.

In fact, already being done - this is how 10GB-LX4 operates. The point
here is that each of the four channels operates at less than 10
gigabits/sec, and that MMF didn't prevent it, in fact, it was done
entirely to make 10 gig work over MMF. Caveats include mode-adapter
cables and other funk to interface LX4 to mmf.

Long-reach single-carrier (ie. single optical channel/frequency) 10
gig over MMF salso has a 'spec' (10G-LRM), but I'm not personally
familiar enough with vendors to offer anything useful or practical.

> One minor consideration is usually SM optics are stronger, so don't forget
> attenuation if it's a short distance or you might burn out your pricey new
> optics!

I would invite folks to examine the various gradations of gig and 10
gig LR/ER/ZR devices. Pulled from a handy table at
http://www.andovercg.com/datasheets/juniper-ethernet-pics.pdf, I
submit for your consideration a summary of the powers across the
various flavors of xenpak. Note the modest increases in launch power,
while there are considerable and huge increases in sensitivity.

10-Gbps Gigabit Ethernet XENPAK, 1-port
• XENPAK pluggable optics (SR, LR, ER, ZR types)
• SR optical interface (IEEE 802.3ae compliant)

– Average launch power: -4.5 through -1 dBm
– Receiver saturation: -1.0 dBm
– Receiver sensitivity: -7.5 dBm

• LR optical interface (IEEE 802.3ae compliant)
– Average launch power: -4 through 0.5 dBm
– Receiver saturation: 0.5 dBm
– Receiver sensitivity: -10.3 dBm

• ER optical interface (IEEE 802.3ae compliant)

– Average launch power: -4.7 through 4 dBm
– Receiver saturation: 1 dBm
– Receiver sensitivity: -11.3 dBm

• ZR optical interface (IEEE 802.3ae compliant)
– Average launch power: 0 through 4 dBm
– Receiver saturation: -7 dBm
– Receiver sensitivity: -24 dBm

-tk




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