How to measure light intensity in multimode fiber optic cables

Use a calibrated optical power meter and a compatible light source to measure light intensity in multimode fiber, following proper wavelength selection, connector cleaning, and reference setup.

Equipment Needed

Optical Power Meter (OPM): Measures the optical power exiting the fiber in dBm (absolute) or dB (relative loss). Light Source: Provides a stable optical signal at standard multimode wavelengths (typically 850 nm and 1300 nm). Launch and Receive Cables: Reference fibers of the same type and core size as the cable under test.

Mating Adapters and Cleaning Supplies: Ensure proper connection and prevent contamination.

Step-by-

Step Procedure

Clean Connectors: Use lint-free wipes or click-to-clean tools to remove dust and debris from all fiber ends and adapters. Set Wavelength: Configure the power meter to match the wavelength of the light source (850 nm or 1300 nm for multimode fibers).

Warm-

Up Equipment: Turn on the light source and power meter, allowing them to stabilize for accurate readings. Establish Reference: Connect the launch cable to the light source and the receive cable to the power meter. Set the meter to 0 dB to establish a baseline reference for relative loss measurements.

Connect to Fiber Under Test: Attach the launch and receive cables to the multimode fiber plant. Ensure proper mating and alignment. Measure Optical Power: Read the optical power on the meter in dBm for absolute power or in dB for insertion loss.

Record the values for each fiber. Calculate Loss (if needed): Subtract the received power from the reference power to determine the fiber's insertion loss in dB.

Best Practices

Consistent Procedures: Always follow the same sequence to ensure repeatable results. Calibration: Regularly calibrate the power meter to maintain accuracy within industry standards. Connector Care: Avoid touching fiber end faces and always clean before testing to prevent measurement errors.

Multiple Measurements: Test each fiber multiple times to verify consistency and detect potential faults like bends, splices, or connector contamination. By following these steps, you can accurately measure the light intensity and insertion loss in multimode fiber optic cables, ensuring reliable network performance and proper documentation of fiber quality.