Optical cable correction values are used to account for test jumper and connector losses, ensuring accurate measurement of fiber optic cable attenuation.

Understanding Correction Values

When testing fiber optic cables with an optical cable tester such as an OLTS (Optical Loss Test Set) or a power meter and light source, the measured signal can be affected by the test equipment, connectors, and reference jumpers. A correction value (also called reference loss or calibration offset) is applied to subtract these extraneous losses from the total measurement, providing the true attenuation of the fiber under test .

How to Apply Correction Values

1. Set Up Reference Measurement: Connect a test jumper (or reference cable) between the light source and power meter. Measure the power output and record it as the reference power (Pref), .
2. Measure Jumper Loss: Insert additional test jumpers or adapters and verify that their added loss is minimal (typically ≤0.75 dB). This ensures the correction value is accurate .
3. Perform Cable Test: Connect the fiber under test using the same jumper configuration. The tester automatically subtracts the reference loss (correction value) from the measured power to calculate the fiber's link attenuation.
4. Bidirectional Testing: For higher accuracy, test the fiber from both ends and average the results. This accounts for differences in connector performance at each end .

Standards and Considerations

• TIA/EIA-568 and other industry standards define acceptable insertion loss for connectors and splices. The correction value ensures that measurements reflect the fiber's performance, not the test setup .
• Use the same wavelength for testing as the network will operate (e.g., 850 nm for multimode, 1310/1550 nm for single-mode) to ensure the correction value is valid .
• Document the reference setup and correction values for future testing and troubleshooting, creating a baseline for network performance .

Summary

Correction values are essential for accurate fiber optic testing, compensating for losses introduced by test jumpers, connectors, and adapters. Proper calibration, reference measurement, and adherence to standards ensure that the measured attenuation truly represents the fiber link, enabling reliable network performance verification and troubleshooting .