An optical power meter (OPM)

An optical power meter (OPM) is a device used to measure the power in an optical signal. The term usually refers to a device for testing average power in fiber optic systems. Other general purpose light power measuring devices are usually called radiometers, photometers, laser power meters, light meters or lux meters.

A typical optical power meter consists of a calibrated sensor, measuring amplifier and display. The sensor primarily consists of a photodiode selected for the appropriate range of wavelengths and power levels. On the display unit, the measured optical power and set wavelength is displayed. Power meters are calibrated using a traceable calibration standard such as a NIST standard.

A traditional optical power meter responds to a broad spectrum of light, however the calibration is wavelength dependent. This is not normally an issue, since the test wavelength is usually known, however it has a couple of drawbacks. Firstly, the user must set the meter to the correct test wavelength, and secondly if there are other spurious wavelengths present, then wrong readings will result.

Sometimes optical power meters are combined with a different test function such as an Optical Light Source (OLS) or Visual Fault Locator (VFL), or may be a sub-system is a much larger instrument. When combined with a light source, the instrument is usually called an Optical Loss Test Set.

July 21, 2011

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