Because they transmit specific wavelengths while rejecting others, optical thin-film filters are critical components of today’s optical communications systems. These components comprise a multilayer stack of thin films on a glass substrate. The operation of an optical filter coating is based on optical interference theory.
The design and manufacturing of the coatings determine the various filter functions of transmitting, reflecting, or blocking light in specific wavelength bands. The filter coating function adheres to the ITU or IEEE wavelength grid standards. Other requirements in some applications, such as wavelength division multiplexing (WDM), optical add-drop multiplexing (OADM), and passive optical networks, are also met by it (PON). Specific requirements drive the customization of filter performance.
A filter for optical communications systems is typically 1 to 3 mm in diameter. Coating technicians deposit the filter on a massive substrate or wafer before processing it to the final size.
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