Multi-bandpass filter

Abstract

The present invention provides a multi-bandpass filter comprising a thin film superimposed layer portion 3 by mirror layers, cavity layers, etc., provided on a substrate 2 with two kinds of dielectrics having different refractive indices, the optical film thickness thereof being a quarter of a reference wavelength as one unit, so as to form a plurality of Fabry-Perrot interferometer structures, wherein the thin film superimposed layer portion 3 has a structure having relationship for superimposition i.e. [M0C1M1 . . . CiMi(T)]k or [M0C1M1 . . . CiMi]k (where i and k are an integer not less than 2, films of the dielectrics being represented by X and Y, the mirror layer being represented by M, the cavity layer being represented by C, and the matching layer being represented by T, and M is a single layer, the optical film thickness of films thereof being odd times of a quarter of the reference wavelength, or an alternating layer represented by [(2p+1)X, (2q+1)Y, . . . ] different dielectrics X, Y (where p, q, . . . are 0 or positive integers); C is a single layer, the optical film thickness of films thereof being even times of a quarter of the reference wavelength, or an alternating layer represented by [(2r)Y, (2s)X, . . . ] of different dielectrics X and Y (where r, s, . . . are zero or positive integers), and T is a single layer, the optical film thickness of films thereof being odd times of a quarter of the reference wavelength.

Description

technical field [0001] The present invention relates to a multi-bandpass filter having passbands in multiple wavelength regions. Background technique [0002] As is well known, optical signals necessary in an optical fiber transmission system for optical communication are efficiently transmitted by a wavelength division multiplexing system (WDM). In this system, a plurality of lights with different wavelength regions are simultaneously transmitted through a single optical fiber cable through an optical wavelength multiplexer, which is a type of interference filter that uses light effectively. Filtering band-pass filter, and then through the signal demodulator with the same structure as the optical multiplexer, these lights are divided into the light of each wavelength region. However, in order to ensure excellent transmission, the multiplex modulation and demodulation must be performed when band-pass filters corresponding to multiple wavelength regions are prepared. [000...

AI Technical Summary

Problems solved by technology

For filters capable of multiplexing or demodulating a plurality of light with different wavelength regions, it is necessary to make the cut-off depths between the different wavelength regions concerned sufficiently large and highly reliable, because if the cut-off depths are not sufficient, Mutual interference will be generated and the communication quality will be deteriorated

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