Dane DeValcourt

Ever since the CampFiber meeting this past weekend in Lafayette, Louisiana where I heard from Major Joey Durel and Terry Huval the Director of Lafayette Utilities System (LUS) who reported that they had selected Alcatel-Lucent for the Fiber To The Home service I have been very interested in more technical details of the network.

Being the geek that I am with a thirst of knowledge for all things networking related I decided to try seeing what solutions by Alcatel-Lucent might be used for this.

I didn’t find much but I did come across the Alcatel-Lucent 7342 Intelligent Service Access Manager (ISAM)

What I found interesting about this solution is on pg. 3 where it states:

“Each PON line supports 2.5 Gb/s downstream and 1.2 Gb/s upstream. In addition to GPON performance, PON lines can be extended up to 20 km with 32 subscribers per PON, or up to 64 subscribers per PON for shorter distances.”

So, each PON supports between 32 to 64 subscribers.  Each PON also supports 2.5Gb/s downstream and 1.2 Gb/s upstream.  So, lets say we go the minimum 32 subscribers.  If you divide the 2.5Gb/s by the 32 subscribers you get 78 Mb/s per user on the downstream.  If you divide the 1.2Gb/s by the 32 subscribers you get roughly 38 Mb/s.

None of this is a problem when we are just talking about the 10Mb/s for the internet service.  But it does lead to some concerns about the 100 Mb/s peer to peer capabilities.  Of course it is understood that all ISP’s over subscribe their service so it’s not a big surprise.

The numbers do get pretty darn low however when you go to the full 64 subscribers each PON is capable of.  For example, the 2.5 Gb/s downstream divided by 64 subscribers gives you only about 40 Mb/s.   The 1.2 Gb/s upstream divided by the 64 subscribers gives you only about 19 Mb/s.

Again I will be the first to admit that none of this is really all that bad.  It’s well above the 10 Mb/s minimum internet service they will be offering.  And since the 100 Mb/s Peer to Peer is kind of a lagniappe service I doubt anyone will complain if they find themselves in a situation where they are unable to attain the full 100 Mb/s service.

To me the most interesting part of it all is the fact that the upstream and downstream aren’t equal within the underlying infrastructure.

And what I would really be curious about is whether the video and voice services also use up some of this bandwidth as well which would effectively lower the total rates I provided previously.  The numbers above assume that the 2.5 and 1.2 are dedicated to data only which I really don’t think is the case.

Of course I don’t even know if this is the solution they picked and I suck at math so I could be way off about everything.  :-)

Another good read about this from Alcatel-Lucent:

http://www1.alcatel-lucent.com/com/en/appcontent/opgss/23168_DeployFiber_wp_tcm228-1336491635.pdf