Single span calibration in a multi-span optical line system

A non-transitory computer-readable medium comprising instructions that, when executed, cause a processing device to perform steps of:

• responsive for a requirement to calibrate a single span in a multi-span optical multiplex section where the single span includes a from-end node and a to-end node, determining no other upstream node in the multi-span optical multiplex section is currently calibrating or faulted;
• responsive to no other upstream node currently calibrating or faulted, calibrating the from-end node with a new target launch power into a fiber associated with the single span;
• and
• calibrating the to-end node keeping target launch power into a fiber associated with an immediate downstream span from the single span uninterrupted from a previous calibration,
• wherein the keeping target launch power into a fiber associated with an immediate downstream span includes using a baseline line-out power profile taken on a line-out port from a previous calibration.