[c-nsp] Optical module transmit power

Michael Robson Michael.Robson at manchester.ac.uk
Fri May 1 10:05:35 EDT 2009


Michael Robson           | Tel: +44 (0) 161 275 6113
Senior Network Engineer  | Fax: +44 (0) 161 275 6120
Net North West           | Email: Michael.Robson at manchester.ac.uk

On 30 Apr 2009, at 16:08, Dale W. Carder wrote:

> On Apr 30, 2009, at 9:37 AM, Michael Robson wrote:
>> We have a selection of ZR modules (XENPAK-10GB-ZR)
>> For these modules, none of them are transmitting at anything like  
>> their maximum of +4.0dBm (Cisco's figures for the maximum transmit  
>> power), they are in fact transmitting between +1.9dBm and +2.3dBm.
> This is to be expected.  Vendors just publish a tolerable
> range somewhere in which the optics will operate.
>> What determines what they will transmit at i.e. is it simply that  
>> better manufactured ones achieve a transmit value closer to the  
>> +4.0dBm power level
> Maybe it's luck.
As I suspected, ah well.

> Anyway, how long are your fiber spans?  If they are really
> long, and you're living on the edge now, you may end up in
> a sticky situation as these optics degrade over time.
They are very long distances; however these links are just stop gaps  
until we procure our DWDM equipment.

> If they are not extremely long, you may have some horrible
> jumpers or splices that are eating some dB.  Do you have
> an OTDR?
> Dale
The circuit supplier quoted dB values for the links on handover which  
should have meant that most of the links would have been within  
acceptable values: perhaps the 6500-quoted values aren't very accurate?

> p.s. My fiance did her postgraduate work at Manchester.
>     Quite a nice place!
Manchester is a great place!



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