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What is a Fiber-Optic Power Meter?

Mal Baxter
Mal Baxter

As a handheld or desktop device, a fiber-optic power meter detects the average power of a continuous beam of light in an optical fiber network. Much the same way as a multimeter measures voltage or current, a fiber-optic power meter 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; this power meter analyzes the high-powered beams of long-distance single-mode fibers and the low-power multibeams of short-distance multimode fibers. The unit is typically made of a solid state detector with signal conditioning electronics, a digital readout, and adapters for connecting with other equipment.

The fiber-optic power meter comes in a range of types to serve multiple applications in fiber-optics networks. Adhering within international standards of optical specifications, the complexity of network design demands that power meters include a certain degree of measurement uncertainty. They analyze average time rather than peak power in order to monitor the duty cycle of continually pulsing light streams.

Man holding computer
Man holding computer

With higher resolutions, desktop-type meters serve in laboratory environments for testing, manufacturing, and research and development. Handheld power meters are used by fiber-optics field technicians in telecommunications and data networks. These devices are calibrated to measure optical power in milliwatts (mW), microwatts (┬Ám), or decibels referenced to one milliwatt (dBm).

Multimode optical applications typically have wavelengths at 850 nanometers (nm) and 1,300 nm of the electromagnetic spectrum. Single-mode uses are often at 1310 nm and 1,0550 nm. A fiber-optic power meter calibrated at these four wavelengths can function for both modes in a wide range of network conditions for field use.

Optical detectors convert light into voltage for electronic measurement of wavelength, as well as dynamic range, or the range of effective light power. Silicon detectors sense the light directly for short wavelength systems, at 350 nm to 1,100 nm. Indium gallium arsenide (InGaAs) detectors suit long wavelength systems at 850 nm to 1,650 nm, as well as germanium detectors at 750 nm to 1,800 nm.

A fiber-optic power meter may also be rack-mounted or able to be interfaced with a computer for direct analysis of a signal. General-purpose interface bus (GPIB) is one typical serial bus used to connect the test equipment with control devices; for greater distances and baud rates, RS232 and RS422 serial interfaces provide increased digital transmission. Another interface is the transistor-transtator logic (TTL), a digital circuit that derives output from dual transistors. Handheld units may be physically and ergonomically designed for improved versatility in field conditions, with interchangeable adapters and large memory capacities. They may run on rechargeable batteries or electrical power.

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