Can I change my sampling optics after calibration?

No! An absolute irradiance calibration requires that the spectrometer and attached optics be calibrated as a system, since that is the only way to characterize the combined effect of all optical components and optical interfaces exactly.

Any change to the spectrometer configuration, fiber, or sensing optics will change the amount of light hitting each pixel, which invalidates the calibration. Even disconnecting the fiber from the spectrometer and reattaching it can change the response of the spectrometer and affect the calibration.

This also explains why Ocean Optics cannot include an irradiance calibration with every spectrometer made; calibration depends on the end-user’s system configuration, and not just the spectrometer configuration.