[191315] in North American Network Operators' Group
Re: Optical transceiver question
daemon@ATHENA.MIT.EDU (Jared Mauch)
Wed Sep 7 17:26:47 2016
X-Original-To: nanog@nanog.org
From: Jared Mauch <jared@puck.nether.net>
In-Reply-To: <001001d20945$b2dc9680$1895c380$@iname.com>
Date: Wed, 7 Sep 2016 17:26:41 -0400
To: Frank Bulk <frnkblk@iname.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces@nanog.org
We have seen cases where the patches introduce enough loss to cause a lot of=
loss. Have you done an OTDR on each link?
Jared Mauch
> On Sep 7, 2016, at 4:23 PM, Frank Bulk <frnkblk@iname.com> wrote:
>=20
> We recently purchased some generic optics from a reputable reseller that
> were marketed to reach 60 km.
>=20
> 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.=20
>=20
> 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 result=
s
> 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.
>=20
> Is it an industry practice to market distance based on the hot optics, not=
> on the worst case, which is minimum TX power?
>=20
> Frank
