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Calculating link loss

Hi

I've a problem with calculating link loss budget. Everywhere people say to add attenuation of all connectors, but there (

http://www.cisco.com/en/US/products/hw/optical/ps2006/products_tech_note09186a00800e6eeb.shtml) in link loss calculation section they add only two connectors in ODF(between patchcord and main optical cable) and don't add connectors between active modules and patchcords. There is info that system margin comprises patchcords, but I think that these connectors should be added too to link loss.

There is also second thing - I want to create connection using 10GBASE-LRM modules and current MM 62,5 links. I calculated power budget by subtracting receiver sensitivity from transmitter power with result of 1,9dB. In that case, I can't even use patchpanels at both sides because link loss exceed this power budget - 4 connectors 0,6dB each exceeds 1,9dB. What to do in this case - is there another method for calculating power budget for this technology? Who to do in this case?

1 REPLY

Calculating link loss

When calculating the loss of a link, the connectors that attach to the terminal equipment are not included in the loss calculations. 

For a 10G-BASE-LRM link:

FIBER LOSS = 1dB/km at 1300nm operating wavelength over MMF. 

Max distance of LRM is 220m, thus fiber loss is < ~0.22dB.

CONNECTOR LOSS = 0.75dB/km (per TIA-568, which is very, very conservative)

2 connectors (patch panel) x 0.75db = 1.5dB loss

0.22 + 1.5dB = 1.72dB link loss.  This is less than the 1.9dB link budget you had calculated. 

The following website, although in need of a good webmaster, has good, basic fiber optic information that can be helpful.

http://www.thefoa.org

Their version of a network calculation

http://www.thefoa.org/tech/ref/basic/design.html#CommSystem

Hope this helps!

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