Hello again, authors!  I've been asked to take another look at this module on behalf of YANG Doctors.  We discussed some of the previous issues in email, and I appreciate the changes you have made.  Most of what I found a probably best described as nits, but I marked this as "with issues" again for the grouping point I raised last time.

While I acknowledge the intent of these groupings is to also be used with other structure (e.g., a "grid-type" leaf), I would like to see some explicit text in the grouping descriptions to clarify that.  While these types/groupings may only be used in ccamp/teas work, I find it odd that one can't really make use of them without additional augmentations or structure.

Also, I noticed you mix types with the l0-types: prefix and those without.  Example:

case single {
            leaf dwdm-n {
              type l0-types:dwdm-n;
              description
                "The given value 'N' is used to determine the
                 nominal central frequency.";
            }
          }

And:

leaf standard-mode {
      type standard-mode;
      config false;
      description
        "G.698.2 standard mode";
    }

Why the discrepancy?

I also notice some differences in choice naming in wdm-label-step.  You've used grid-type everywhere else, but here you use l0-grid-type.  Probably should leave out the "l0-".

Similarly, you have some groupings (like l0-tunnel-attributes) named with "l0-".  Is that required given this will be used with the l0-types: prefix?