Methods used to measure wavelength

1. Naked eye observation

   2. The oldest (and easiest) way to analyze light is just to look at it: are your Christmas lights red or green? Using eyes alone, a person can get a general idea of the wavelength of visible light.

   3. Gas composition analysis commonly uses this fact. Gasses glow at different wavelengths, due to the differences in electron orbit energies. When put in a high electric field, gasses glow (think about fluorescent lights).

   4. When you look at the glowing light through a prism, instead of a full rainbow, you will see specific bands of color, each corresponding to energy differences specific to that gas. Matching up observed light bands with known bands of gasses, you can determine the composition of glowing gasses. This is how astronomers determine the composition of far away stars.

   5. Open an illustration
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2. Standard spectrum analyzers

   2. Optical analyzers function like oscilloscopes for light. Plug in a light source (usually through a fiber optic cable), and the optical analyzer can tell you how much light is at each frequency. These machines are big and bulky, and run very slowly (only a few samples per second).

3. Adaptive analysis with interrogators

   2. In recent years, engineers have developed systems that can scan adaptively. Unlike the broad spectrum analyzer, adaptive analyzers only examine a small range of frequencies at a time. They use a filter to block other frequencies and a simple photodiode to detect how much light has passed through.

   3. By changing the range and remembering how much power passed through at each frequency, an adaptive analyzer can produce a picture of the overall frequency response much faster, and with smaller and cheaper components, than a broad spectrum analyzer. These devices are called "interrogators" because they interrogate one frequency at a time.

   4. BYU is currently developing an adaptive analyzer that will be faster, cheaper, and more flexible than current models available on the market. Click to learn more about the FSIM project

   5. Compare sizes of wavelength analyzers
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