How to diagnose a fault in an optical power meter

To check the error of an optical power meter, verify its readings against a known reference, inspect for drift or zero-point issues, and ensure proper calibration and maintenance.Pre-Check and Inspection

Before testing accuracy, inspect the meter and connectors for visible damage, dust, or debris, as contamination can affect readings. Ensure the meter is properly powered and all settings, including wavelength selection, are correct for the fiber system under test . Clean the sensor and input ports with isopropyl alcohol and lint-free wipes to prevent measurement errors .

Zeroing the Meter

Perform a zeroing procedure by covering the sensor and pressing the zero or null button. This ensures the meter reads zero when no light is present. A significant reading during zeroing indicates a zero-point failure, which may result from contamination or incorrect calibration .

Cross-Checking and Drift Verification

Optical power meters can drift over time due to aging photodiodes, temperature cycling, and humidity exposure. To check for drift, compare the meter's readings with a known-good reference meter or a stable, self-calibrated optical source. Deviations within the manufacturer's specifications indicate acceptable performance, while larger deviations suggest the meter may need recalibration .

Calibration and Error Assessment

True calibration requires a NIST-traceable reference lab. The lab measures the meter at multiple wavelengths and power levels, providing a certificate with deviations. If deviations exceed specifications, the meter's internal calibration tables are adjusted . While you cannot fully calibrate the meter yourself, regular verification against a reference source helps monitor error between annual calibrations .

Recording and Documentation

Document all readings, pre-checks, and verification results. Keeping a log allows you to track changes over time, identify trends in drift, and ensure consistent measurement accuracy .

Summary

To check the error of an optical power meter:

1. Inspect and clean the meter and connectors.
2. Zero the meter to detect zero-point errors.
3. Compare readings with a known reference or stable optical source.
4. Monitor for drift over time.
5. Maintain documentation and schedule regular calibration with an accredited lab. Following these steps ensures your optical power meter provides reliable and accurate measurements, minimizing errors in optical network testing and maintenance .