The differences between a PASSIVE WDM network and PON
http://www.championone.com/uploads/documents/appnotes/The%20difference%20between%20a%20PASSIVE%20WDM%20network%20and%20PON.pdf

Cologix Toronto: Metro Connect Services
https://www.cologix.com/pdf/Cologix-Metro-Connect-Toronto.pdf

DWDM active and passive comparison
http://networkengineering.stackexchange.com/questions/2925/dwdm-active-and-passive-comparison