I use the MikroTik and FS 20km SFPs with short patch cables all the
time. Nothing bad has happened yet. DDM reports the Rx power around
-6dBm, but you can't always trust the DDM data, however I highly doubt
they're overloaded. Then we have customers at about 2-4 miles usually
around -9 to -11. When the contractor doesn't screw up anyway. Had a
couple at -21 and they still worked. Not even any errors with traffic load.
I agree completely, buy a light meter.
On 9/14/2016 8:16 PM, Faisal Imtiaz wrote:
My humble suggestion:-
invest in a light meter. not need to guess..
Get a $50 unit from FS.com or amazon... they are not junk, and get the
job done.
Standard optics (SMF) 10km should be fine with shorter cables.
LR (Long Range) 40K or up... you can have them overload the receiver...
A tip shared from the field....
Keep an #2 pencil handy.... if you need to make an attenuation in a
hurry !... take the fiber cable and start warping it around the pencil
as tightly as you can ..
and tape it so that it does not unwind.
I have tested this .... using a light meter... and yes it does work,
you may need to give it 15 or more turns....
BTW those optics putting out 4db those are meant to light up 40km or
60km links.. but are also used in link where there is lots of loss
expected due to Mux/Demux or other passive device..
and yes you don't want to use these with a short cables :)
Faisal Imtiaz
Snappy Internet & Telecom
7266 SW 48 Street
Miami, FL 33155
Tel: 305 663 5518 x 232
Help-desk: (305)663-5518 Option 2 or Email: [email protected]
------------------------------------------------------------------------
*From: *"trey" <[email protected]>
*To: *[email protected]
*Sent: *Wednesday, September 14, 2016 7:08:55 PM
*Subject: *Re: [AFMUG] Single mode attenuators needed at 30m
You should not need any attenuation if you are using the same lr
sfp/xfp on both ends. However there is a small chance if they are
different part numbers or manufacturers that one may transmit at
the same or greater than the others max receive level. Typically
it is a .5-1db tx with a max rx of 3-4. I have ran into some 4db
tx XFPs though. It will probably work fine like that, but I have
had a couple trickle errors under high utilization.
I would say it's always best to keep some attenuators on hand
probably 5db and 10db with those you can make just about any optic
work at any distance less than what they are rated. I personally
carry around everything from 1-20db because of manualy balancing
dwdm systems and seem to go through 4,7 and 13s the most.
-------- Original message --------
From: Chuck McCown <[email protected]>
Date: 9/14/16 5:19 PM (GMT-06:00)
To: [email protected]
Subject: Re: [AFMUG] Single mode attenuators needed at 30m
The SFP spec will have an absolute maximum RX level. If I
remember correctly, last one I checked was higher than the max TX
level of 4 dBm. Seems like the absolute max RX was something like
16 or 20 dBm.
*From:* Eric Kuhnke <mailto:[email protected]>
*Sent:* Wednesday, September 14, 2016 2:41 PM
*To:* [email protected] <mailto:[email protected]>
*Subject:* Re: [AFMUG] Single mode attenuators needed at 30m
Those are totally safe to use with even a 1 meter fiber patch
cable between two pieces of gear in the same rack.
On Wed, Sep 14, 2016 at 1:39 PM, TJ Trout <[email protected]
<mailto:[email protected]>> wrote:
1310 10gb 10km
On Wed, Sep 14, 2016 at 1:38 PM, Eric Kuhnke
<[email protected] <mailto:[email protected]>> wrote:
What frequency and tx power of singlemode? You do not
need to attenuate 1GbE 1310nm LX (5-10km reach) or 10GbE
1310nm LX optics for very short distances. Tons of ISPs
use all 1310/LX optics for intra-rack and intra-suite
fiber XCs because they're cheap, easy and multimode is dumb.
If you are using optics which are marketed as capable of
20, 40 or more km reach (and/or 1490nm, 1550nm optics) you
do need to attenuate on the Rx.
On Wed, Sep 14, 2016 at 11:20 AM, TJ Trout <[email protected]
<mailto:[email protected]>> wrote:
Do I need to pad my optics at 100ft? Or could someone
tell me how to estimate the loss so I can compare to
the spec?
