If an ONU does not wish to use its entire allocated time slot, it may inform the OLT about this. The OLT may then decide to reallocate the remaining time slot to another ONU which does not have an SLA.
In cases where an ONU chooses not to use its full allotted period, it can inform the OLT of this decision. The OLT may subsequently choose to reassign the unused portion of the time slot to another ONU without an SLA.