[j-nsp] LX SFP Question

Richard A Steenbergen ras at e-gerbil.net
Fri Sep 25 11:58:06 EDT 2009

On Fri, Sep 25, 2009 at 11:15:32AM -0400, Shane Ronan wrote:
> Along these lines, but slightly off topic, what kind of light meters  
> do you guys use?

Search ebay for "optical power meter", you'll find any number of 
perfectly good 850/1310/1550 handheld meters for around $200. The 
hardest part is making sure the connector actually takes SC, rather than 
something less useful like ST or FC. You really can't go wrong with 
something like:


Note that all light meters use wideband rx optics, and will receive and
report a value for any color light you throw at them. The reason for the
850/1310/1550 selector is simply to "correct" the value picked up by the
receiver, i.e. if you select 1310 but fire a 1550 signal at it the value
reported will be higher than reality. Other than that, the only thing
you need to know about a light meter is the difference between relative
mode (measuring loss from a known fixed light source on the other end)
and absolute mode (measuring the actual light received from any
transmitter). If I had a nickle for every time a datacenter tech got
confused between those two and told me I was transmitting +67dBm I'd be
a very rich man (or own a very powerful laser).

Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)

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