Wavelength division multiplexer and demultiplexer
First Claim
1. A method for demultiplexing light of a plurality of wavelengths in an input beam by means of a filter having a characteristic property that the filter passes incident light of wavelengths within a characteristic wavelength band and reflect incident light of wavelengths outside said first characteristic wavelength band, said plurality of wavelengths including at least three wavelengths, wherein said characteristic wavelength band varies with the angle of incidence of said incident light to the normal direction to the filter, said method comprising:
- (a) directing and collimating said input beam towards a filter with said characteristic property at a first incident angle so that light of one of the at least three wavelengths is reflected and light of another of the at least three wavelengths is passed by the filter; and
(b) directing and collimating said light substantially reflected or passed by the filter towards the filter at a second incident angle different from the first incident angle, the first and second incident angles being such that the selective passage and reflection of light of different wavelengths by the filter separates the input beam into three output beams, each output beam containing light of one of the at least three wavelengths.
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Accused Products
Abstract
A demultiplexer employs collimators for directing light of different wavelengths towards a filter so that light of one wavelength may be passed while reflecting light of other wavelengths. Light of the wavelengths that are passed or reflected may again be directed towards the same or different filter for further demultiplexing. The filter used has a characteristic wavelength band that varies with the angle of incidence to the filter. The same types of filter may be used for multiplexing. An input beam is passed through a filter at an angle of incidence at which light of a different wavelength would be reflected. Thus two input beams carrying such two wavelengths are directed towards the same location of the filter on opposite sides of the filter so that the reflected light of one wavelength will emerge as one beam with light of the other wavelength that passes through the filter. The emerging beam is then collected to multiplex light of the two wavelengths. This process can be repeated to multiplex light of a plurality of wavelengths.
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Citations
30 Claims
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1. A method for demultiplexing light of a plurality of wavelengths in an input beam by means of a filter having a characteristic property that the filter passes incident light of wavelengths within a characteristic wavelength band and reflect incident light of wavelengths outside said first characteristic wavelength band, said plurality of wavelengths including at least three wavelengths, wherein said characteristic wavelength band varies with the angle of incidence of said incident light to the normal direction to the filter, said method comprising:
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(a) directing and collimating said input beam towards a filter with said characteristic property at a first incident angle so that light of one of the at least three wavelengths is reflected and light of another of the at least three wavelengths is passed by the filter; and (b) directing and collimating said light substantially reflected or passed by the filter towards the filter at a second incident angle different from the first incident angle, the first and second incident angles being such that the selective passage and reflection of light of different wavelengths by the filter separates the input beam into three output beams, each output beam containing light of one of the at least three wavelengths. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for multiplexing light of a plurality of wavelengths in different light beams into one output optical channel by means of a filter having a characteristic property that the filter passes incident light of wavelengths within a characteristic wavelength band and reflect incident light of other wavelengths, wherein said characteristic wavelength band varies with the angle of incidence of said incident light to the normal direction to the filter, said method comprising:
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(a) directing and collimating a light beam containing light of one of said plurality of wavelengths towards a location of a first filter with said characteristic property from one side of the first filter so that light of said one wavelength passes through the first filter at an angle to the first filter; (b) directing and collimating a light beam containing light of at least one additional wavelength of said plurality of wavelengths towards the location of the first filter from the side of the first filter opposite to said one side at substantially said angle to the first filter so that light of at least one additional wavelength is reflected by the first filter at said location to emerge as one beam with or in proximity to light of said one wavelength that has passed through the first filter; and (c) collecting light of said one wavelength and said at least one additional wavelength into an output optical channel to form a collected beam. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. An apparatus for demultiplexing light of a plurality of wavelengths including at least three wavelengths in an input beam, said apparatus comprising:
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a filter having a characteristic property that the filter passes incident light of wavelengths within a characteristic wavelength band and reflect incident light of wavelengths outside said first characteristic wavelength band, wherein said characteristic wavelength band varies with the angle of incidence of said incident light to the normal direction to the filter; a first optical channel directing and collimating said input beam towards the filter at a first incident angle so that light of one of the at least three wavelengths is reflected and light of another of the at least three wavelengths is passed by the filter; a second optical channel directing and collimating said light substantially reflected or passed by the filter towards the filter at a second incident angle different from the first incident angle, the first and second incident angles being such that the selective passage and reflection of light of different wavelengths by the filter separates the input beam into three output beams, each output beam containing light of one of the at least three wavelengths. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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24. An apparatus for multiplexing light of a plurality of wavelengths in different light beams into one output optical channel, said apparatus comprising:
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a first filter having a characteristic property that the first filter passes incident light of wavelengths within a characteristic wavelength band and reflects incident light of other wavelengths, wherein said characteristic wavelength band varies with the angle of incidence of said incident light to the normal direction to the first filter; a first connecting optical channel directing and collimating a light beam containing light of one of said plurality of wavelengths towards a first location of the first filter from one side of the first filter so that light of said one wavelength passes through the first filter at an angle to the first filter; a second connecting optical channel directing and collimating a light beam containing light of at least one additional wavelength of said plurality of wavelengths towards the first location of the first filter from the side of the first filter opposite to said one side at substantially said angle to the first filter so that light of at least one additional wavelength is reflected by the first filter at said first location to emerge as one beam with or in proximity to light of said one wavelength that has passed through the first filter; and a first output optical channel collecting light of said one wavelength and said at least one additional wavelength to form a collected beam. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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Specification