EXFO FTB -5240S/5240BP Optical Spectrum Analyzer for FTB 500 (NS-1434) - Manual (Page 432)

Maintenance
424 FTB-5240S/5240BP
Recalibrating the Unit
Recalibrating the Unit
Manufacturing and service center calibrations are based on the
ISO/IEC 17025 Standard, which states that calibration documents must not
contain a recommended calibration interval, unless this has been
previously agreed upon with the customer.
Validity of specifications depends on operating conditions. For example,
the calibration validity period can be longer or shorter depending on the
intensity of use, environmental conditions and unit maintenance. You
should determine the adequate calibration interval for your unit according
to your accuracy requirements.
Under normal use, EXFO recommends calibrating your unit every year.