Re: Optical transceiver question

[Nicolas Cortes <julionicolascortes () gmail com>]

The typical situation of the vendor is that the link-budget of the
transceiver considers the worst scenario for TX and loss of dBs generated
by time of operation of the laser, standard attenuation of the fiber, how
it changes in how old it is,... in other ways, the calc ispessimistic.

In my experience, the transceivers have a variation in TX power from
1-3 dBs in worst cases.
In short-haul links doesn't matter very much. In long-haul is something to
consider.

Nicolas./~



On Wednesday, 7 September 2016, Eric Kuhnke <eric.kuhnke () gmail com> wrote:

> 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
> <javascript:;>> 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