A fiber-optic meter, more often referred to as a fiber-optic power meter, is a device that measures a continuous light beam's average power coming from a fiber-optic cable. It can determine the amount of light either coupled into an optical receiver or produced by an optical source. Fiber-optic meters typically measure the signal in microwatts or milliwatts. The majority of procedures used in the testing of fiber-optic meters are standardized by both national and international organizations, including the International Electrotechnical Commission (IEC) and the Electronic Industries Association (EIA).
Typical fiber-optic meters consist of a calibrated sensor, usually a photodiode, and a display showing measurement units. The photodiode is calibrated to measure the appropriate range of wavelengths. A display unit, usually an LED readout, shows the measured optical power and the corresponding wavelength being measured. The power shown will be relative to the wavelength being measured, and will vary depending on how the meter is calibrated. A fiber-optic meter is calibrated using a traceable calibration standard, such as one put forth by the National Institute of Standards and Technology (NIST).
Fiber-optic meters use optical cables that are either single or multi-mode, or a combination of both. A single-mode cable allows signal transmissions at particularly high bandwidths and allows relatively longer transmission distances. Multi-mode cables allow shorter transmission distances and bandwidths because the signal is dispersed.
There are a variety of connectors that can be used with a fiber-optic power meter. Their use depends on the type of cable being used, the device it is attached to, and the modality of transmission being measured. When using multi-mode cables, connector alignment and coupling is less critical than with single-mode fibers.
The wavelength range, power resolution, and accuracy and optical power range of the meter should all be taken into consideration. There a variety of sizes and types, ranging from hand-held to more powerful rack-mounted systems. Some fiber-optic meters can interface with computers. There are also several types of other interfaces made for use with different media and signal types.
Even though fiber-optic systems use light instead of electric current, it's important to follow safety precautions when testing with a fiber-optic meter. Wearing eye protection when working with high-power cables will provide an extra layer of safety. It is also prudent to double check couplings, even when working with lower power cables.
