DWDM interconnects

[Pete Kruckenberg <pete () kruckenberg com>]

How common are DWDM interconnects between networks
(carriers)?

Is DWDM considered a reliable/scalable/operable carrier
interconnection technology?

Is multi-vendor DWDM (whether internal to the network or for
carrier interconnection) practical or sensible, especially
for carrier/network interconnection? Many vendors proclaim
interoperability, but does that work in the real world?

Pete.