I'm doing some research for a future implementation of CWDM in our infrastructure and came across CWDM-MUX8A today. Seems to me it's a new unit sporting among other features a monitor port.
Could this port be used to tap one or several of the wavelengths and if so, what equipment is required?
The monitor port on the CWDM-MUX8A will have all of the multiplexed optical aggregate traffic on it - e.g., all the individual ITU grid wavelengths that your have running on your line side of the CWDM system. Typically those wavelengths have been groomed for multiplexing via a transponder card and wrapped in something like a G.709 OTN transport protocol.
Looking at the monitor signal with anything other than an optical power meter for level checks would require an analyzer device that is able to separate and analyze the aggregated wavelengths.
That is not your typical protocol analyzer you may be familiar with from the LAN world but rather an optical test set. Something like the Anritsu MP1590b (http://www.us.anritsu.com/products/MP1590B_MP1591A_Network-Performance-Tester_ARSPG_ARQQSidZ656.aspx) or Agilent J7232A (http://www.trs-rentelco.com/Model/AT_J7232A.aspx). Just to rent one of these runs US$4000-5000 per month.
You are better off for most purposes using the limited troubleshooting / monitoring functionality built into the last bit of active electronics - e.g., the transponder cards. They will be monitoring the power level and basic error correction techniques done by the encapsulation protocol and report errors or alarms to the chassis control card and, optionally, to your element manager (e.g., CTC or CTM in the Cisco world).