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: supp...@snappytelecom.net > From: "trey" <t...@3dsc.co> > To: af@afmug.com > 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 <ch...@wbmfg.com> > Date: 9/14/16 5:19 PM (GMT-06:00) > To: af@afmug.com > 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 > Sent: Wednesday, September 14, 2016 2:41 PM > To: af@afmug.com > 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 < t...@voltbb.com > wrote: >> 1310 10gb 10km >> On Wed, Sep 14, 2016 at 1:38 PM, Eric Kuhnke < eric.kuh...@gmail.com > 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 < t...@voltbb.com > 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?
