Monolithic array of fiber optic bandpass filters

摘要

An array of optical RF bandpass filters which is fabricated from planar waveguides on a single substrate. The array of filters receives an input of frequency multiplexed optical signals and separates the intensity modulated optical signal of the desired frequency from signals at other frequencies. Each bandpass filter comprises a resonant cavity formed from a segment of a planar optical waveguide with mirrors deposited at each end. By using ultra high purity CVD techniques common in the optical fiber industry, material absorption is dramatically reduced. Much thicker waveguides are grown than those conventionally fabricated, allowing the use of refractive index differences between waveguide and cladding which are much smaller than those normally used in planar waveguides. To enable the fabrication of a monolithic array of filters having differing center frequencies, the substrate is cut at an angle so that resonant cavities of different lengths are formed.