Can the power of an optical power meter be adjusted Why

Yes, an optical power meter can be adjusted, but the method depends on whether it is a factory calibration or a field verification.

Factory Calibration

Optical power meters rely on photodiodes to convert light into electrical signals, which are then interpreted using internal calibration tables. Over time, these detectors can drift, and the internal tables may become less accurate. True calibration is performed by sending the meter to a certified lab, where it is measured against NIST-traceable reference standards at multiple wavelengths and power levels.

If deviations exceed specifications, the lab adjusts the meter's internal tables and re-tests it, issuing a calibration certificate documenting the results.

Field Verification and Adjustment

Some meters allow limited field adjustments, such as zeroing the meter to ensure it reads zero when no light is present. This is typically done by covering the sensor and pressing a zero or null button. Field verification can also be performed by comparing readings against a recently calibrated reference meter or a stable light source.

Any significant discrepancy may indicate the need for recalibration or adjustment.

Practical Steps for Adjustment

Clean connectors and sensors: Dirt or contamination can cause inaccurate readings, so clean the meter port and fiber connectors before measurement. Set the correct wavelength: Ensure the meter's wavelength matches the signal being measured, as detector response varies with wavelength. Zero the meter: Cover the sensor and press the zero button to eliminate baseline offsets.

Verify against a reference: Use a calibrated light source or another meter to check for drift or inconsistencies. Send for professional calibration if needed: If readings remain inaccurate, the meter should be sent to a certified calibration lab for adjustment.

Summary

While minor adjustments like zeroing and wavelength selection can be done in the field, full calibration of an optical power meter requires professional service. Regular verification and proper maintenance, including cleaning and correct wavelength settings, help ensure accurate measurements between annual calibrations.