How to measure the transmittance of a fiber optic panel

Transmittance of a fiber optic panel is measured by injecting a known light source into the fiber and using a power meter at the output to calculate the optical loss.

Equipment Needed

To measure transmittance, you typically need:

• Optical Light Source: Provides a stable light signal at the operational wavelength of the fiber (commonly 850 nm, 1300 nm, or 1550 nm for single-mode/multimode fibers) .
• Optical Power Meter: Measures the optical power received at the output end of the fiber, calibrated in dBm or milliwatts .
• Optical Loss Test Set (OLTS): Combines a light source and power meter for precise insertion loss measurements .
• Connector Adapters and Cleaners: Ensure proper coupling and minimize contamination at fiber end faces .

Measurement Procedure

1. Prepare the Fiber Panel: Inspect and clean all fiber connectors to prevent contamination, which can affect transmittance .
2. Connect the Light Source: Attach the source to the input port of the fiber panel.
3. Measure Input Power: Record the optical power directly from the source to establish a reference level.
4. Measure Output Power: Connect the power meter to the output port of the fiber panel and record the received power.
5. Calculate Transmittance: Transmittance (or insertion loss) is calculated as the difference between input and output power: $$\text{Loss (dB)}=10{\log }_{10}\left(\frac{P_{\text{input}}}{P_{\text{output}}}\right)$$ A lower loss indicates higher transmittance .

Best Practices

• Bi-directional Testing: Measure in both directions to account for connector and fiber variations .
• Multiple Wavelengths: Test at the operational wavelength and at a secondary wavelength to ensure consistent performance .
• Environmental Considerations: Temperature, bending, and stress on the fiber can affect measurements, so maintain stable conditions .

Optional Advanced Methods

• Optical Time Domain Reflectometer (OTDR): Can provide a detailed loss profile along the fiber, identifying localized losses or defects .
• Spectral Analysis: For systems with multiple wavelengths, an optical spectrum analyzer can measure transmittance across the spectrum . By following these procedures, you can accurately determine the transmittance and optical loss of a fiber optic panel, ensuring reliable performance in communication or data transmission systems.