Low Cost CWDM or DWDM

What vendors do you recommend for low cost CWDM / DWDM gear? Assume you
have a fiber ring of 50 miles of fiber, and want to have POPs evenly
spaced around the ring that you want to jump on and off of. Assume you only
have 2 fiber strands to work with, but can obtain two more at an additional
cost. Does 2 vs 4 fibers make a difference? The goal is to be able to offer
multiple 10G connections to clients on the ring. All ethernet/wave no
support for legacy SONET needed. How do you decide between CWDM vs DWDM?

There are so many manufacturers that make transport gear I do not even know
where to begin. Is there a guide to navigating through the big optical
transport vendors? There are over 20 of them, and they all seem to do the
same thing on paper.

We have been very happy with Adva for our DWDM ring deployments with multiple drop-add points. As always proper engineering is critical to make sure you are taking into account the loss points from all the muxes, drop-adds, etc.

Adva's sales / engineering / and subsequent support have been fantastic.

Granted they aren't as cheap as the "low cost" ebay gear out of china but you are getting quality instead of a crapshoot of loss on each mux or drop/add you source.