A Quick Guide To Fiber Optic Power Meter

by Fiber-MART.COM

When you install and terminate fiber optic cables, you always have to test them. A test should be conducted for each fiber optic cable plant for three main areas: continuity, loss, and power. And optical power meters are part of the toolbox essentials to do this. There are general-purpose power meters, semi-automated ones, as well as fiber optic power meters optimized for certain types of networks, such as FTTx or LAN/WAN architectures. It’s all a matter of choosing the right gear for the need.

 

Here is a quick guide to fiber optic power meters and how they work.

 

Optical power meters are commonly used to measure absolute light power in dBm. For dBm measurement of light transmission power, proper calibration is essential. A fiber optic power meter is also used with an optical light source for measuring loss or relative power level in dB. To calculate the power loss, optic power meter is first connected directly to an optical transmission device through a fiber optic pigtail, and the signal power is measured. Then the measurements are taken at the remote end of the fiber cable.

 

Fiber optic power meter detects the average power of a continuous beam of light in an optical fiber network, tests the signal power of laser or light emitting diode (LED) sources. Light dispersion can occur at many points in a network due to faults or misalignments; the power meter analyzes the high-powered beams of long-distance single-mode fibers and the low-power multibeams of short-distance multimode fibers.

 

Important specifications for fiber optic power meters include wavelength range, optical power range, power resolution, and power accuracy. Some devices are rack-mounted or hand held. Others are designed for use atop a bench or desktop. Power meters that interface to computers are also available.

 

The fiber optic power meter is a special light meter that measures how much light is coming out of the end of the fiber optic cable. The power meter needs to be able to measure the light at the proper wavelength and over the appropriate power range. Most power meters used in datacom networks are designed to work at 850nm and 1300nn. Power levels are modest, in the range of –15 to –35dBm for multimode links, 0 to –40dBm for single mode links. Power meters generally can be adapted to a variety of connector styles such as SC, ST, FC, SMA, LC, MU, etc.

 

Generally, multimode fiber is tested with LEDs at both 850nm and 1300nm and single mode fiber is tested with lasers at 1310nm and 1550nm. The test source will typically be a LED for multimode fiber unless the fiber is being used for Gigabit Ethernet or other high-speed networks that use laser sources. LEDs can be used to test single mode fibers less than 5000 meters long, while a laser should be used for long single mode fibers.

 

Most fiber optic power meters are calibrated in linear units such as milliwatts or microwatts. They may also provide measurements in decibels referenced to one milliwatt or microwatt of optical power. Typically, fiber optic power meters include a removable adaptor for connections to other devices. By measuring average time instead of peak power, power meters remain sensitive to the duty cycle of digital pulse input streams.

 

Use fiber optic power meter and other useful fiber optic test equipment to ensure that your fiber optic system will operate smoothly.