A wavemeter measures the wavelength of laser beams in optical fibers. There are two types: scanning and static, based on Michelson and Fizeau interferometers respectively. Accuracy depends on stability and resolution, and some wavemeters can also function as spectrometers.
A wavemeter is a device used in optical fibers to measure the wavelength of laser beams. Also called a wavelength meter, a wavemeter tests the optical elements of products as they are being manufactured. Wavemeters are used when extremely precise measurements are needed.
Wavemeters are interferometers used only to measure wavelengths. Interferometers measure light waves by using interference, usually provided by mirrors, to split a beam of light in two and then recombine it. By studying the resulting shape, measurements of the radius can be taken.
There are two main types of wavemeters: scanning and static. The first type is usually based on the Michelson scanning interferometer. These types of wavemeters consist of three mirrors, a light source, and a detector. Resembling a cross, each piece of the Michelson interferometer is on one corner of the cross. The light source is placed in front of one of the mirrors and a second mirror and the detector are placed perpendicular to them. The third mirror, semi-silvered, is positioned at an angle in the centre. This is the mirror that actually splits the beam.
When the light source is activated, the laser will hit the silver half mirror and split, one half of the beam passes directly and the other half moves perpendicular to the first. Both halves will hit mirrors located behind and above the central mirror, bounce and be recombined by the silver half mirror. The recombined beam will then travel down into the detector, which will analyze the results.
The distance between the mirrors, or arms, can be changed to scan a range of lengths. The accuracy of these wavemeters can reach 0.01 nm. However, several problems, such as beam imperfections, length drifts, and input power fluctuations, could lead to less accurate results.
Most static wavemeters are based on the Fizeau static interferometer. These wave meters have no moving parts, but use the same principle of specular reflection. Less common static wavemeters are based on Fabry-Pérot interferometers, which are linear. However, these are more often used as optical spectrometers than wave meters.
High accuracy for any type of wavemeter depends on the stability of the configuration and resolution of the display. A reference laser, whose wavelength is known, working in tandem with the laser under test will also help increase accuracy. In cases where extreme accuracy is critical, it may be necessary to calibrate the machine once a minute.
Wavelengths can also be measured with spectrometers, but although spectrometers provide more information about the components of the light beam, accuracy is sacrificed. Some types of wavemeters can also function as spectrometers, thus providing additional information without sacrificing accuracy.
Protect your devices with Threat Protection by NordVPN
