cf discussion at  https://git.opendaylight.org/gerrit/c/transportpce/+/96193/4/olm/src/main/java/org/opendaylight/transportpce/olm/power/PowerMgmtImpl.java

Current code is not compliant with OpenROADM MSA since the commit https://git.opendaylight.org/gerrit/c/transportpce/+/94560

It increases the power with 3 dB for 87.5 GHz slot-width compared to 50 GHz while the MSA says it should be increased by 10*log(87.5/50).
Before the mentioned commit, olm-renderer-input in transportpce-common-types included slot-width instead of width ("Width of nmc" according to the description) and the power calculation was done according to the MSA recommendation.

Width is defined in transportpce-common-types@2021-06-18.yang:

leaf width

The approximation is about using the spacing rather than the signal width @-20 dBm to make the calculation in OpenROADM.
The reason is basically because we don't have all the elements to qualify the signal width for all modulation format (different filter shapes, unkown exact Roll off factor...).