How to choose the nm value of an optical power meter for different types of light

Select the optical power meter wavelength to match the light source and fiber type for accurate measurements, typically 850 nm or 1300 nm for multimode fibers and 1310 nm or 1550 nm for single-mode fibers.

Matching Wavelength to Fiber Type

• Multimode fiber: Use 850 nm or 1300 nm, as these are standard transmission wavelengths for multimode systems .
• Single-mode fiber: Use 1310 nm or 1550 nm, which correspond to the low-loss windows of single-mode fibers .
• Special applications: For CWDM or PON systems, select the wavelength that matches the specific channel or service wavelength .

Detector Considerations

The type of photodetector in the optical power meter affects the usable wavelength range :

• Silicon (Si) detectors: Sensitive from 400–1000 nm, suitable for visible light and short-wavelength multimode fiber (e.g., 665 nm or 820 nm LEDs).
• Germanium (Ge) detectors: Sensitive from 800–1600 nm, commonly used for telecom wavelengths.
• Indium-Gallium-Arsenide (InGaAs) detectors: Sensitive from 900–1700 nm, ideal for single-mode fiber and long-wavelength telecom applications (1310 nm, 1550 nm).

Calibration and Accuracy

• Always set the meter to the wavelength of the light source to ensure accurate readings .
• Optical power meters are typically calibrated at 850 nm, 1300 nm, and 1550 nm, and some meters allow custom calibration for other wavelengths .
• Using a mismatched wavelength can result in significant measurement errors due to detector sensitivity variations.

Practical Tips for Field Testing

1. Check the fiber type and light source wavelength before measurement.
2. Select the corresponding wavelength on the power meter to match the source.
3. Clean connectors and adapters to minimize measurement errors .
4. Verify the meter's measurement range to ensure it can handle the expected power levels, typically from -70 dBm to +30 dBm .
5. Use appropriate adapters (FC, SC, ST, LC) to maintain consistent coupling and calibration . By carefully matching the optical power meter's wavelength to the light source and considering the detector type, you can achieve accurate and reliable power measurements across different fiber optic systems.