[191314] in North American Network Operators' Group
Re: Optical transceiver question
daemon@ATHENA.MIT.EDU (Eric Kuhnke)
Wed Sep 7 16:51:05 2016
X-Original-To: nanog@nanog.org
In-Reply-To: <001001d20945$b2dc9680$1895c380$@iname.com>
From: Eric Kuhnke <eric.kuhnke@gmail.com>
Date: Wed, 7 Sep 2016 13:51:01 -0700
To: "nanog@nanog.org list" <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
What you're saying is if you purchase ten identical optics with the same
SKU, and put them on a few hundred meters of coiled SC/UPC to SC/UPC
simplex fiber and an optical power meter on the other end, they're showing
varying real world Tx powers from between +0 to +5dBm?
That's not right at all, they're supposed to be sorted at the factory by
their actual optical power output before they have labels put on them.
On Wed, Sep 7, 2016 at 1:23 PM, Frank Bulk <frnkblk@iname.com> wrote:
> We recently purchased some generic optics from a reputable reseller that
> were marketed to reach 60 km.
>
> But what we found, based on the spec sheets, is that it could only reach
> that distance if the optics were transmitting on the high side of the
> transmit power range.
>
> For example, if the TX range was 0 to +5 dBm and minimum RX power was -20
> dB, the designed optical budget should be no more than 20 dB (0 - -20).
> Based on the wavelength the appropriate loss would be 0.4 dB/km and results
> in only 50 km, not 60 km. To get 60 km it would need 24 dB of link margin,
> and that would only be attainable if it was transmitting on the high side,
> at +4 dBm.
>
> Is it an industry practice to market distance based on the hot optics, not
> on the worst case, which is minimum TX power?
>
> Frank
>
>
