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RE: Question? 1300nm WWDM channel width


Having surveyed the temperature dependence, not only of our lasers, but also
lasers from other vendors, a more reasonable number is 0.08 nm/degreeC,
rather then the 0.1 nm/degree number that you quoted.  In addition, with a 0
to 70 degree ambient temperature requirement, there is no reason why the
laser junction should see a 100 degree temperature range.  Of course this is
implementation dependent, but it is difficult to imagine much more than an
80 degree variation.  This would use up 6.4 nm of the 11.4 nm window,
leaving another 5 nm for tolerance.  Most laser vendors are comfortable with
a +/- 2.5 nm specification. 

Best Regards,


Brian E. Lemoff, Ph.D.
Project Manager
LAN/MAN Optical Technologies
Agilent Laboratories
3500 Deer Creek Rd., MS 26M-9
Palo Alto, CA 94304-1392

phone:  (650) 485-8957
FAX:     (650) 485-3626
email:   brian_lemoff@xxxxxxxxxxx 

> -----Original Message-----
> From: Eric Grann [mailto:grann@xxxxxxxxxxx]
> Sent: Tuesday, October 31, 2000 9:12 AM
> To: stds-802-3-hssg@xxxxxxxx
> Subject: Question? 1300nm WWDM channel width
> To all:
> I have been trying to get some feedback on the channel width 
> of the 1300nm
> WWDM system.   As I currently understand the specifications, 
> the bandwidth
> of an individual wavelength channel is 11.4nm (spec of * 
> 5.7nm).  At these
> laser wavelengths, both DFBs and VCSELs have a temperature 
> coefficient of
> 0.1nm/*C.  In order to achieve a final transceiver 
> temperature specification
> of 0-70*C, the lasers must have a slightly higher temperature 
> range.  To be
> safe, I would recommend a range of (-5) to 95*C.  With this range, the
> wavelength drift will account for 10nm of the channel 
> bandwidth, leaving
> only 1.4nm for the tolerance of the laser fabrication.  The 
> feedback I have
> received from several laser vendors is, this will be very difficult,
> resulting in low yields and increased costs for both DFBs and 
> especially new
> 1300nm VCSELs.  
> I would like to recommend that this specification be 
> increased to at least
> 14nm (spec of * 7.0nm).  With a 24.5nm channel spacing, this 
> will still
> provide plenty of room for a relatively simply filter.  
> I would like to get some feedback and response to this recommendation.
> Eric Grann
> Chief Technical Officer
> Blaze Network Products