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US 6,487,335 B1Granted
Distributed filter for DWDM cascade device using Mach-Zehnder interferometers
AssigneeTera Fiberoptics, Inc.
InventorsYawen Yang, Wenyong Zhu
Life of this patent
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Abstract
System and method for wavelength discrimination using a DWDM (N+1)-stage cascade tree structure with distributed filtering to provide acceptable optical isolation and acceptable flat-top wavelength response. Each channel has a Mach-Zehnder interferometer (MZI) that provides wavelength discrimination. The input channel includes an inverted Fabry-Perot etalon (FPE) filter or an inverted, non-symmetric MZI filter that helps provide a desired flat-top response. Each channel in a second stage has a selected conventional MZI filter, and each channel in a third stage has a selected FPE filter, to help provide the desired optical isolation. The number of output channels may be 32, 64 or more.
Claims32
A system for processing light, the system comprising:
- an (N+1)-stage fiber optic cascade structure, numbered n=0, 1, 2, . . . , N with N≧5, with stage number 0 being a light input channel, with stage number n′(1≦n′≦N) having 2n fiber optic channels and each channel in each stage n″ being connected to two channels in stage n″+1(n″=0, 1, 2, . . . , N−1) by a Mach-Zehnder interferometer, referred to as an “MZI”;
- a first filter array, positioned in a selected stage n1 and including 2n1 selected Fabry-Perot etalons, referred to as “FPEs,” with each FPE in stage n1 having transmission minima at a first selected sequence of wavelengths and being positioned in one of the 2n1 channels of stage n1, where n1 lies in the range 0≦n1≦N1, where N1≦N;
- a second filter array, positioned in a selected stage n2 and including 2n2 selected MZI filters, each MZI filter having transmission maxima at a second selected sequence of wavelengths and being positioned in one of the 2n2 channels of stage n2, where n2 lies in the range 0≦n2≦N2;
- where N2 ≦N;
- and
- a third filter array, positioned in a selected stage n3 and including 2n3 selected FPEs, with each FPE in stage n3 having transmission maxima at a third selected sequence of wavelengths and being positioned in one of the 2n3 channels of stage n3, where n3 lies in the range 0≦n3≦N3, where N3≦N.
3 more elements
A system for processing light, the system comprising:
- an (N+1)-stage fiber optic cascade structure, numbered n=0, 1, 2, . . . , N with N ≧5, with stage number 0 being a light input channel, with stage number n′(1≦n′≦N) having 2n fiber optic channels and each channel in each stage n″ being connected to two channels in stage n″+1(n″=0, 1, 2, . . . , N−1) by a Mach-Zehnder interferometer, referred to as an “MZI”;
- a first filter array, positioned in a selected stage n1 and including 2n1 selected non-symmetric MZIs with each non-symmetric MZI in stage n1 having at least one coupling coefficient α<0.5 and having transmission minima at a first selected sequence of wavelengths and being positioned in one of the 2n1 channels of stage n1, where n1 lies in the range 0≦n1≦N1, where N1≦N;
- a second filter array, positioned in a selected stage n2 and including 2n2 selected MZI filters, each MZI filter having transmission maxima at a second selected sequence of wavelengths and being positioned in one of the 2n2 channels of stage n2, where n2 lies in the range 0≦n2≦N2, where N2≦N;
- and
- a third filter array, positioned in a selected stage n3 and including 2n3 selected FPEs, with each FPE in stage n3 having transmission maxima at a third selected sequence of wavelengths and being positioned in one of the 2n3 channels of stage n3, where n3 lies in the range 0≦n3≦N3, where N3≦N.
2 more elements
A method for processing light, the method comprising:
- receiving light at an (N+1)-stage fiber optic cascade structure, numbered n=0, 1, 2, . . . , N with N≧5 with stage number 0 being a light input channel, with stage number n′(1≦n′≦N) having 2n fiber optic channels and each channel in each stage n″ being connected to two channels in stage n″+1(n″=0, 1, 2, . . . , N−1) by a Mach-Zehnder interferometer, referred to as an “MZI”;
- passing the received light through a first filter array, positioned in a selected stage n1 and including 2n1 selected Fabry-Perot etalons, referred to as “FPEs,” with each FPE in stage n1 having transmission minima at a first selected sequence of wavelengths and being positioned in one of the 2n1 channels of stage n1, where n1 lies in the range 0≦n1≦N1, where N1≦N;
- passing the received light through a second filter array, positioned in a selected stage n2 and including 2n2 selected MZI filters, each MZI filter having transmission maxima at a second selected sequence of wavelengths and being positioned in one of the 2n2 channels of stage n2, where n2 lies in the range 0≦n2≦N2;
- where N2≦N;
- and
- passing the received light through a third filter array, positioned in a selected stage n3 and including 2n3 selected FPEs, with each FPE in stage n3 having transmission maxima at a third selected sequence of wavelengths and being positioned in one of the 2n3 channels of stage n3, where n3 lies in the range 0≦n3≦N3, where N3≦N.
3 more elements
A method for processing light, the method comprising:
- receiving light at an (N+1)-stage fiber optic cascade structure, numbered n=0, 1, 2, . . . , N with N≧5, with stage number 0 being a light input channel, with stage number n′(1≦n′≦N) having 2n fiber optic channels and each channel in each stage n″ being connected to two channels in stage n″+1(n″=0, 1, 2, . . . , N−1) by a Mach-Zehnder interferometer, referred to as an “MZI”;
- passing the received light through a first filter array, positioned in a selected stage n1 and including 2n1 selected non-symmetric MZIs with each non-symmetric MZI in stage n1 having at least one coupling coefficient (α<0.5 and having transmission minima at a first selected sequence of wavelengths and being positioned in one of the 2n1 channels of stage n1, where n1 lies in the range 0≦n1≦N1, where N1≦N;
- passing the received light through a second filter array, positioned in a selected stage n2 and including 2n2 selected MZI filters, each MZI filter having transmission maxima at a second selected sequence of wavelengths and being positioned in one of the 2n2 channels of stage n2, where n2 lies in the range 0≦n2≦N2;
- where N2≦N;
- and
- passing the received light through a third filter array, positioned in a selected stage n3 and including 2n3 selected FPEs, with each FPE in stage n3 having transmission maxima at a third selected sequence of wavelengths and being positioned in one of the 2n3 channels of stage n3, where n3 lies in the range 0≦n3≦N3, where N3≦N.
3 more elements
Dependencies are inferred from the claim text.