What is a fiber optic power meter? The fiber optic power meter measures how much light is coming out of a fiber optic cable. It can be used to determine the amount of light being generated by an optical source, or the amount of light being coupled into an optical receiver.  

Optical power is usually measured in dBm, or decibels referenced to 1mW. These devices measure the average optical power, not the peak power, so they are sensitive to the duty cycle of the data transmitted.

Their wavelength and power range have to be appropriately matched to the system being measured. Most power meters used to test communication networks are designed to work at 850nm, 1300nm and 1500nm wavelength ranges and in the power range of -15 to -35dBm for multimode links, or 0-40dBm for single mode links.

What types of power meters are available?

Fiber optic power meters, like DMMs, come in a variety of types. The measurement uncertainty of practically all fiber optic power meters is the same, limited by the physical constrains of transferring standards with optical connections.

Most meters have an uncertainty of +/- 5% or approximately 0.2dB, no matter what the resolution of the display may be. Lower cost meters or those for field use usually have a resolution of 0.1dB, laboratory meters display 0.01dB, and a resolution of 0.001dB is available on a few specialized meters.

The appropriate resolution for a measurement should be chosen according to the test. Laboratory measurements of low-loss patch cables, connectors and splices can be made to 0.01dB resolution and an uncertainty of 0.05dB or less if great care is used in controlling the test conditions.

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