nbsCohpmThresholdsMaxQ is read-write and holds a persistent, administrator-set alarm threshold for the maximum Q factor on this coherent optical interface, i.e. a composite signal-quality figure of merit derived from the coherent receiver's error statistics, where a higher value means a cleaner, lower-error signal; not-supported is encoded as 0xFFFFFFFF. Unit measurement: 0.1 dB. The first time nbsCohpmCurrentMaxQ meets/exceeds this threshold (or, for a Min object, drops below it) during a reporting interval, the device raises the nbsCohpmTrapsMaxQ notification, so a sysadmin sets this value to the maximum Q factor level they consider unsafe for this specific link's optics and fiber path.