[c-nsp] Where do you put the optical attenuators?

[Eric Van Tol]

I am by no means a fiber expert, but I've been told by old school fiber
guys that the RX side is the best place to put them, as the attenuators
generate some back reflectance which is best to have as far away from
the TX of a GBIC/SFP as possible.

-evt


> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net 
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Deepak Jain
> Sent: Friday, October 26, 2007 4:35 PM
> To: neal rauhauser
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] Where do you put the optical attenuators?
> 
> 
> All of these are good ideas and points. What I'd suggest to 
> the equation 
> is if one side is more staffed/more manned/more accessible, 
> its better 
> to put your attenuators there. Cleaner is also a nice point 
> to consider, 
> but of course everyone keeps their connectors and environment 
> super-neat, right?
> 
> 
> neal rauhauser wrote:
> >   Well, BOFH style, I would say you put them where you need them :-)
> > 
> > 
> >    We had a problem with this last month - burned up a 
> PA-POS-OC3 due to
> > having it on only 800' of dark fiber. We bought 3dB through 
> 15dB attenuators
> > from Fiber Instrument Sales along with an inexpensive test 
> kit ($1,000 or
> > so) and then fooled around until we got what we wanted. We 
> ended up with 7dB
> > of input attenuation and 5dB of output.
> > 
> >    Place the stuff where it makes sense - out of harm's 
> way, which can be
> > either at the device or at the patch panel. Get two of 
> everything you use
> > *including the fiber jumpers*. I've seen people with one 
> critical oddball
> > fiber jumper make a wrong move and then have *long* outages 
> - this happened
> > with one customer when the change from SC to LC connectors 
> was just starting
> > ...
> > 
> >   Oh, and I don't have to tell you to document this, right? 
> Use the system
> > in place, and if the system is "ad hoc" print a couple 
> single page copies of
> > what was done and why, then laminate 'em and glue 'em to 
> the wall in the
> > appropriate location :-)
> > 
> > 
> > 
> > On 10/26/07, Tassos Chatzithomaoglou <achatz at forthnet.gr> wrote:
> >> Does anyone know if in-line optical attenuator have to be 
> connected on the
> >> receiver side only?
> >>
> >> For example in the following link
> >>
> >>
> >>     A---------------------C
> >> SW1                      SW2
> >>     B---------------------D
> >>
> >> SW1 is transmitting through A and receiving through B
> >> SW2 is transmitting through D and receiving through C
> >>
> >> Where is the best place to put the attenuators? B & C?
> >> Can i put them on A & B?
> >>
> >> I did some tests putting them on every possible side (as 
> long as there is
> >> one on each fiber strand) and all of them worked, but i
> >> was wondering if there is a best practice about them.
> >>
> >> --
> >> Tassos
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