OC-3 SingleMode Minimum Distance?

[NPT_2]

We are having an OC-3 Delivered from our Local Telco, and I was asked whether I wanted the OC-3 Delivered on Singlemode or Multimode.  I will be using a PA-POS-1OC3 card in our 7206VXR Router that will be connecting to the Telco's FLM150 MUX that is under 12 feet away from the 7206. 

My question is can I use singlemode on such a short distance link without issues?            

The reason I am considering singlemode (on such a short link) is that if I ever wanted to move the OC-3 to a differant router located further away, I could extend it over our in house single mode fiber a couple miles away. 

Do you think we would have issues with an initial OC-3 link so short over SingleMode fiber? 

Jim

[Tom Randstrom]

Do you know what OC3 reach interface specification the telco is using?  This will help determine the answer.

The PA-POS-OC31 card uses pluggable SFP optics.  According to the Cisco Compatibility Docs, an Intermediate-Reach (IR1) and Long-Reach (LR1) are the available options for SMF. If the telco is using either of these reach specifications, then, according to Cisco data sheet, it shouldn't be a problem to direct connect at such a short reach.  It may be advantageous to install a 5db attenuator on your receiver end to put the received light level more within the receiver's operating range.   

[Joseph W. Doherty]

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Posting

I recall (?) reading somewhere that minium distance for SX and LX is 2 meters.

[Michael Dooley]

The question for you is which of the three SFPs the PA-POS-1OC3 card uses did you buy? 

POM-OC3-MM  you want Multimode

POM-OC3-SMIR you want single mode

POM-OC3-SMLR you want single mode

Mike Dooley

Cisco Optical TAC

[NPT_2]

Mike,

I haven't actually bought my SFP's yet, however the question wasn't which SFP to buy, but whether the POM-OC3-SMIR SFP would work with a very short singlemode distance (around only 2 to 3 meters) so I have the option to extend the distance in the future if the need arises.  Or would I be better off just using multimode? 

At this point from what other feedback I am getting it sounds like a short link is doable with the POM-OC3-SMIR. 

[Tom Randstrom]

If the service provider is allowing you the option of SMF or MMF, choose the one that suits your needs (today and tomorrow).  They both, when operated within their operating parameters, will provide the same results; an error free link. 

The multimode fiber OC3 SFP has a reach of 2km/1.2 miles.  If your next router is less than this distance, then you could use the multimode SFP and save a few dollars.  Otherwise, you could spend a few extra dollars today and invest in an intermediate-reach (IR) SFP to "anticipate" the possible move to a router further from the SP POP over SMF

(up to ~15km/9miles).

I hope this helps.

Tom  

[Michael Dooley]

Jim,

In your original post you said "...extend it over our in house single mode fiber a couple miles away"...  So if there is a remote possibility you will do this, then you should get the intermediate reach SFP.  As Tom points out, it will go up to 9 miles over single mode fiber.  But, you will probably need attenuators to use it with the router located 2-3 meters away.

Mike