Optical Bandpass filters transmit Light over a pre-determined band of wavelengths while rejecting, by absorption, Radiation or scattering, all other wavelengths.

Filters are an important part of optical and electro-optical technology. They control spectral Energy in applications ranging from spectrometry to optical communication systems. Various optical components are needed in the optical communication systems such as Laser diodes, Photodetectors and optical filters. Among others, the optical filters are the essential elements in the large capacity optical Telecommunication Network that employs the technique of Wavelength multiplexing. In the field of optical communication, an optical Filter is used to separate signal light of a specific wavelength from light of any other wavelengths (e.g., Noise light). Optical Bandpass filers transmit light over a pre-determined band of wavelengths while rejecting, by absorption, radiation or scattering, all other wavelengths. In the wavelength Multiplex network, a large number of information signals are multiplexed on a single optical Fiber by changing the Frequency and hence the wavelength of the optical carrier for each optical channel. The Multiplexing and/or Demultiplexing may be accomplished using a series of light bandpass filters. Each filter is formed as a substrate and a multilayer Dielectric light-transmissive optical stack deposited upon the substrate. The Bandpass Filter transmits only light of a specific wavelength. Optical bandpass filters generally include an optical resonant cavity comprising an Optical Fiber having a specific length and mirrors formed at each end of the optical fiber. Apertures in each mirror allow an RF modulated light signal to be injected into and resonate at the RF Modulation frequency within the fiber.