LX sfp minimum range
dholmes at mwdh2o.com
Thu Jan 26 12:46:44 CST 2012
I have found that -5dB or -10dB attenuators must be used on the send or receive strands between Cisco LX connected switches at relatively short distances of < 1 km over standard singlemode fiber.
Other Vendors' SFPs rated up to 25 km do not need attenuators at distances <1 km.
From: Jon Heise [mailto:jon at smugmug.com]
Sent: Thursday, January 26, 2012 9:41 AM
To: Pierre-Yves Maunier
Cc: nanog at nanog.org
Subject: Re: LX sfp minimum range
Awesome, i got some single mode LC LC fiber off monoprice, sounds like i
should be all set for this. Thanks for everyones info
On Thu, Jan 26, 2012 at 6:24 AM, Pierre-Yves Maunier <nanog at maunier.org>wrote:
> 2012/1/26 David Storandt <dstorandt at teljet.com>
> > You can put a 3dB or 5dB optical pad on the link if the receiver can't
> > handle zero-distance optical power.
> We're using SFP LX for a couple of years even in back to back configuration
> for equipments within the same rack with a 1 meter patch cord without any
> Max TX is -3dBm, Max RX sensivity is -3dBm so there is no problem.
> 1. I don't think I've ever had a LX SFP that TX at -3 dBm, they're usually
> around -5 to -7 dBm.
> and example in a live router :
> pymaunier at re1.tcr1.rb.par> show interfaces diagnostics optics ge-7/3/* |
> match "Laser output power "
> Laser output power : 0.3160 mW / -5.00 dBm
> Laser output power : 0.1800 mW / -7.45 dBm
> Laser output power : 0.2600 mW / -5.85 dBm
> Laser output power : 0.3210 mW / -4.93 dBm
> Laser output power : 0.3070 mW / -5.13 dBm
> Laser output power : 0.3200 mW / -4.95 dBm
> Laser output power : 0.3180 mW / -4.98 dBm
> Laser output power : 0.3140 mW / -5.03 dBm
> 2. You can assume a patch cord add between 0.2 to 0.5 dB of attenuation so
> even with a SFP TX at -3dBm, you won't receive at the Max RX sensitivity.
> Pierre-Yves Maunier
This communication, together with any attachments or embedded links, is for the sole use of the intended recipient(s) and may contain information that is confidential or legally protected. If you are not the intended recipient, you are hereby notified that any review, disclosure, copying, dissemination, distribution or use of this communication is strictly prohibited. If you have received this communication in error, please notify the sender immediately by return e-mail message and delete the original and all copies of the communication, along with any attachments or embedded links, from your system.
More information about the NANOG