nanog mailing list archives
Re: Muni fiber: L1 or L2?
From: Johnny Eriksson <bygg () cafax se>
Date: Fri, 1 Feb 2013 23:33:40 WET
Owen DeLong <owen () delong com> wrote:
Nope The power going into each fiber out of the splitter is 1/16th that of what went into the splitter.
... which is 12 dB loss.
Yes, your total in-line loss is still 10km, but you are forgetting about the fact that you lost 15/16th of the power effectively going to the fiber when you went through the splitter (in addition to the splitter loss itself). So: CO Based splitter: Each customer gets (IN - 16dB - (10km x .26db))/32
Each customer gets IN - ~0dB - 12 dB - 2.6 dB = IN - 14.6 dB.
Splitter at 9km: Each customer gets (IN - (9km x .26dB) -16db)/32-(1km x .26db)
Each customer gets IN - 2.34 dB - 12 dB - 0.26 dB = IN - 14.6 dB.
If we use 5dBm as our input, this works out: CO: (5db - 16db - (10km x .26db) / 32 /32 is effectively -15 db (-3db = ½ power, 32 = 2^5) Substituting: (5db - 16db - 2.6db) -15db = -28.6db to each customer. Spitter at 9km: (5db - (9km x .26db) -16db)/32-(1km x .26db) Substituting: (5db - 2.34db -16db)-15db-.26db = -28.08db to each customer So there is a difference, but it seems rather negligible now that I've run the numbers. However, it's entirely possible that I got this wrong somewhere, so I invite those more expert than I to review the calculations and tell me what I got wrong.
You are multiplying logarithmic values.
Owen
--Johnny
Current thread:
- Re: Muni fiber: L1 or L2?, (continued)
- Re: Muni fiber: L1 or L2? Masataka Ohta (Feb 09)
- Re: Muni fiber: L1 or L2? Jason Baugher (Feb 08)
- RE: Muni fiber: L1 or L2? Eric Wieling (Feb 06)
- RE: Muni fiber: L1 or L2? Eric Wieling (Feb 06)
- Re: Muni fiber: L1 or L2? Scott Helms (Feb 06)
- Re: Muni fiber: L1 or L2? Jean-Francois Mezei (Feb 06)
- Re: Muni fiber: L1 or L2? Scott Helms (Feb 06)
- Re: Muni fiber: L1 or L2? Jay Ashworth (Feb 05)
- Re: Muni fiber: L1 or L2? Stephen Sprunk (Feb 10)
- Re: Muni fiber: L1 or L2? Stephen Sprunk (Feb 10)
- Re: Muni fiber: L1 or L2? Johnny Eriksson (Feb 01)
- RE: Muni fiber: L1 or L2? Frank Bulk (iname.com) (Feb 01)
- Re: Muni fiber: L1 or L2? Fletcher Kittredge (Feb 03)
- Re: Muni fiber: L1 or L2? Jay Ashworth (Feb 01)
- Re: Muni fiber: L1 or L2? Jérôme Nicolle (Feb 05)
- Re: Muni fiber: L1 or L2? Jay Ashworth (Feb 05)
- Re: Muni fiber: L1 or L2? Masataka Ohta (Feb 06)
- Re: Muni fiber: L1 or L2? Jay Ashworth (Feb 11)
- Re: Muni fiber: L1 or L2? Owen DeLong (Feb 11)
- Re: Muni fiber: L1 or L2? Scott Helms (Feb 12)
- Re: Muni fiber: L1 or L2? Stephen Sprunk (Feb 11)
- Re: Muni fiber: L1 or L2? Owen DeLong (Feb 11)