Wavelength router

• US 6,501,877 B1
• Filed: 11/16/1999
• Issued: 12/31/2002
• Est. Priority Date: 11/16/1999
• Status: Expired due to Term

• Current Assignee: Altera Corporation (Intel Corporation)
• Original Assignee: Network Photonics, Inc.
• Inventors: Roth, Richard S., Georgis, Steven P., Weverka, Robert T.
• Primary Examiner(s): Sanghavi, Hemang
• Assistant Examiner(s): PAK, SUNG H
• Application Number:
  US09/442,061
• Time in Patent Office: 1,141 Days
• Field of Search: 385/31, 385/15, 385/37, 385/33, 385/35, 385/39, 385/47
• US Class Current: 385/31
• CPC Class Codes: G02B 6/29307 components assembled in or forming a solid transparent unitary block, e.g. for facilitating component alignment
• CPC Class Codes: G02B 6/29308 Diffractive element having focusing properties, e.g. curved gratings Rowland circle spectrometers G01J3/20
• CPC Class Codes: G02B 6/2931 Diffractive element operating in reflection
• CPC Class Codes: G02B 6/29311 Diffractive element operating in transmission
• CPC Class Codes: G02B 6/29313 characterised by means for controlling the position or direction of light incident to or leaving the diffractive element, e.g. for varying the wavelength response switching G02B6/35
• CPC Class Codes: G02B 6/29373 utilising a bulk dispersive element, e.g. prism
• CPC Class Codes: G02B 6/2938 for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
• CPC Class Codes: G02B 6/29383 Adding and dropping
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: G02B 6/29397 Polarisation insensitivity
• CPC Class Codes: G02B 6/352 the reflective optical element having a shaped reflective surface, e.g. a reflective element comprising several reflective surfaces or facets that function together
• CPC Class Codes: G02B 6/3522 the optical element enabling or impairing total internal reflection using evanescent coupling G02B6/3536
• CPC Class Codes: G02B 6/3548 1xN switch, i.e. one input and a selectable single output of N possible outputs
• CPC Class Codes: G02B 6/356 in an optical cross-connect device, e.g. routing and switching aspects of interconnecting different paths propagating different wavelengths to (re)configure the various input and output links switching polarized beams G02B6/3594; power equalizers G02B6/356 and G02B6/3594; path selecting means H04Q11/0001
• CPC Class Codes: H04J 14/0204 Broadcast and select arrangements, e.g. with an optical splitter at the input before adding or dropping
• CPC Class Codes: H04J 14/0205 Select and combine arrangements, e.g. with an optical combiner at the output after adding or dropping
• CPC Class Codes: H04J 14/0206 Express channels arrangements
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04J 14/0213 Groups of channels or wave bands arrangements
• CPC Class Codes: H04J 14/0283 WDM ring architectures
• CPC Class Codes: H04J 14/0291 : Shared protection at the optical multiplex section (1:1, n:m)
• CPC Class Codes: H04Q 11/0005 : Switch and router aspects
• CPC Class Codes: H04Q 2011/0016 : using wavelength multiplexing or demultiplexing
• CPC Class Codes: H04Q 2011/0024 : using space switching
• CPC Class Codes: H04Q 2011/0026 : using free space propagation (e.g. lenses, mirrors)
• CPC Class Codes: H04Q 2011/0035 : using miscellaneous components, e.g. circulator, polarisation, acousto/thermo optical

Abstract

A wavelength router that selectively directs spectral bands between an input port and a set of output ports. The router includes a free-space optical train disposed between the input ports and said output ports, and a routing mechanism. The free-space optical train can include air-spaced elements or can be of generally monolithic construction. The optical train includes a dispersive element such as a diffraction grating, and is configured so that the light from the input port encounters the dispersive element twice before reaching any of the output ports. The routing mechanism includes one or more routing elements and cooperates with the other elements in the optical train to provide optical paths that couple desired subsets of the spectral bands to desired output ports. The routing elements are disposed to intercept the different spectral bands after they have been spatially separated by their first encounter with the dispersive element.

Claims

1. A wavelength router for receiving light having a first number, N, of spectral bands at an input port and directing subsets of the N spectral bands to respective ones of a second number, M, of output ports, the wavelength router comprising:

a first cylindrical lens for collimating light emanating from the input port in a first transverse dimension;

a second cylindrical lens for collimating the light in a second transverse dimension that is orthogonal to the first transverse dimension;

a transmissive dispersive element for dispersing the light in the first transverse dimension in a particular sense;

a third cylindrical lens for focusing the light in the first transverse dimension;

a plurality of N tiltable mirrors in the focal plane of said third cylindrical lens, each intercepting a respective spectral band and directing that spectral band back toward said third cylindrical lens; and

a plurality of actuators, each coupled to a respective tiltable mirror to effect selective tilting of the light path of the respective spectral band;

wherein each spectral band is collimated in the first transverse dimension by said third cylindrical lens, dispersed in the first transverse dimension by said dispersive element in a sense opposite the particular sense, focused in the second transverse dimension by said second cylindrical lens and focused in the first transverse dimension by said first cylindrical lens, whereupon each spectral band is brought to a focus in both the first and second transverse dimensions at a respective position determined by the respective tiltable mirror.

2. The wavelength router of claim 1, and further comprising an array of output fibers positioned at the output ports.

3. The wavelength router of claim 1 wherein said mirrors are made from micro-electro-mechanical system (MEMS) elements.

4. A wavelength router for receiving light having a first number, N, of spectral bands at an input port and directing subsets of the N spectral bands to respective ones of a second number, M, of output ports, the wavelength router comprising:

a first optical element with positive optical power disposed to collimate light emanating from the input port;

a transmissive dispersive element for dispersing the light in a first transverse dimension in a particular sense to spatially separate the spectral bands;

a second optical element with positive optical power disposed to focus the light traveling from said dispersive element; and

a plurality of retroreflectors in the focal plane of said second optical element, each retroreflector intercepting a respective spectral band and directing that spectral band back toward said second optical element with a transverse displacement in a second transverse dimension that is orthogonal to the first transverse dimension, said transverse displacement depending on a state of that retroreflector;

wherein each spectral band is collimated by said second optical element, dispersed in the first transverse dimension by said dispersive element in a sense opposite the particular sense, and focused by said first optical element, whereupon each spectral band is brought to a focus at a respective position determined by the respective retroreflector.

5. A wavelength router for receiving light having a first number, N, of spectral bands at an input port and directing subsets of the N spectral bands to respective ones of a second number, M, of output ports, the wavelength router comprising:

an optical element with positive optical power disposed to collimate light emanating from the input port;

a reflective dispersive element for dispersing the light traveling from said optical element in a first transverse dimension in a particular sense to spatially separate the spectral bands, said dispersive element directing the spectral bands back to said optical element, which focuses the light traveling from said dispersive element; and

a plurality of retroreflectors in the focal plane of said optical element, each retroreflector intercepting a respective spectral band and directing that spectral band back toward said optical element with a transverse displacement in a second transverse dimension that is orthogonal to the first transverse dimension, said transverse displacement depending on a state of that retroreflector;

wherein each spectral band is collimated by said optical element, dispersed in the first transverse dimension by said dispersive element in a sense opposite the particular sense, and focused by said optical element, whereupon each spectral band is brought to a focus at a respective position determined by the respective retroreflector.

6. The wavelength router of claim 5 wherein said optical element is a spherical lens.

7. The wavelength router of claim 5 wherein said optical element is a concave reflector.

8. The wavelength router of claim 5 wherein:

each retroreflector includes a rooftop prism; and

the state of that retroreflector is defined by a transverse position of that retroreflector'"'"'s rooftop prism.

9. The wavelength router of claim 5 wherein:

each retroreflector includes a rooftop prism and a relatively movable associated body of transparent material configured for optical contact with that retroreflector'"'"'s rooftop prism; and

the state of that retroreflector is defined at least in part by whether that retroreflector'"'"'s rooftop prism is in optical contact with its associated body.

10. A wavelength router for receiving light having a first number, N, of spectral bands at an input port and directing subsets of the N spectral bands to respective ones of a second number, M, of output ports, the wavelength router comprising:

a first cylindrical lens for collimating light emanating from the input port in a first transverse dimension;

a second cylindrical lens for making the light traveling from said first cylindrical lens less divergent in a second transverse dimension that is orthogonal to the first transverse dimension;

a reflective dispersive element for dispersing the light traveling from said second cylindrical lens, said light being dispersed in the first transverse dimension in a particular sense, said dispersive element directing the spectral bands at different angles back to said second cylindrical lens;

the spectral bands traveling away from said dispersive element being collimated by said second cylindrical lens in the second transverse dimension and being focused by said first cylindrical lens in the first transverse dimension; and

a plurality of N tiltable mirrors in the focal plane of said first cylindrical lens, each intercepting a respective spectral band and directing that spectral band back toward said first cylindrical lens;

wherein each spectral band leaving its respective tiltable mirror is collimated in the first transverse dimension by said first cylindrical lens, partially focused by said second cylindrical lens in the second transverse dimension, dispersed in the first transverse dimension by said dispersive element in a sense opposite the particular sense, further focused in the second transverse dimension by said second cylindrical lens and focused in the first transverse dimension by said first cylindrical lens, whereupon each spectral band is brought to a focus in both the first and second transverse dimensions at an output port determined by the respective tiltable mirror.

11. The wavelength router of claim 10 wherein said dispersive element has a resolution significantly less than a separation between spectral bands.

12. The wavelength router of claim 11 wherein the resolution is achieved by a differential path length greater than about 3 cm.

13. The wavelength router of claim 10 wherein:

each of said tiltable mirrors has a geometric dimension that defines a respective spectral acceptance range; and

said dispersive element has a resolution that is finer than the spectral acceptance range of said tiltable mirrors so as to provide each routed channel a spectral transfer function that is characterized by a band shape having a relatively flat top.

14. A wavelength router for receiving light having a first number, N, of spectral bands at an input port and directing subsets of the N spectral bands to respective ones of a second number, M, of output ports, the wavelength router comprising:

a first spherical lens having positive optical power;

a transmissive dispersive element for dispersing light in a first transverse dimension;

a second spherical lens having positive power; and

a plurality of retroreflectors, each retroreflector intercepting a respective spectral band and directing that spectral band back toward said second spherical lens with a transverse displacement in a second transverse dimension that is orthogonal to the first transverse dimension, said transverse displacement depending on a state of that retroreflector;

wherein;

said first spherical lens, said dispersive element, said second spherical lens, and said plurality of N retroreflectors are disposed so that light emanating from the input port encounters, in order, said first spherical lens a first time, said dispersive element a first time, said second spherical lens a first time, said plurality of N retroreflectors, said second spherical lens a second time, said dispersive element a second time, and said first spherical lens a second time;

said first spherical lens operates said first time to collimate the light, and said second time to focus the light on the output ports;

said second spherical lens operates said first time to focus the light on said plurality of retroreflectors, and said second time to collimate the light; and

said dispersive element operates said first time to impart an angular separation among the spectral bands in the first transverse dimension so that the spectral bands encounter their respective retroreflectors, and operates said second time to remove said angular separation among the spectral bands in the first transverse dimension;

whereupon each spectral band is brought to a focus at an output port determined by the state of the respective retroreflector.

15. The wavelength router of claim 14 wherein wherein said dispersive element has a resolution significantly less than a separation between spectral bands.

16. The wavelength router of claim 15 wherein the resolution is achieved by a differential path length greater than about 3 cm.

17. The wavelength router of claim 14 wherein:

each of said retroreflectors has a geometric dimension that defines a respective spectral acceptance range; and

said dispersive element has a resolution that is finer than the spectral acceptance range of said retroreflectors so as to provide each routed channel a spectral transfer function that is characterized by a band shape having a relatively flat top.

18. A wavelength router for receiving light having a first number, N, of spectral bands at an input port and directing subsets of said N spectral bands to respective ones of a second number, M, of output ports, the wavelength router comprising:

a spherical lens having positive optical power;

a reflective dispersive element for dispersing light in a first transverse dimension; and

a plurality of retroreflectors, each retroreflector intercepting a respective spectral band and directing that spectral band back toward said spherical lens with a transverse displacement in a second transverse dimension that is orthogonal to the first transverse dimension, said transverse displacement depending on a state of that retroreflector;

wherein;

said spherical lens, said dispersive element, and said plurality of N retroreflectors are disposed so that light emanating from the input port encounters, in order, said spherical lens a first time, said dispersive element a first time, said spherical lens a second time, said plurality of N retroreflectors, said spherical lens a third time, said dispersive element a second time, and said spherical lens a fourth time;

said spherical lens operates said first time to collimate the light, said second time to focus the light onto said plurality of N retroreflectors, said third time to collimate the light, and said fourth time to focus the light on the output ports; and

said dispersive element operates said first time to impart an angular separation among the spectral bands in the first transverse dimension so that the spectral bands encounter their respective retroreflectors, and operates said second time to remove said angular separation among the spectral bands in the first transverse dimension;

whereupon each spectral band is brought to a focus at an output port determined by the state of the respective retroreflector.

19. The wavelength router of claim 18 wherein said dispersive element has a resolution significantly less than a separation between spectral bands.

20. The wavelength router of claim 19 wherein the resolution is achieved by a differential path length greater than about 3 cm.

21. The wavelength router of claim 18 wherein:

each of said retroreflectors mirrors has a geometric dimension that defines a respective spectral acceptance range; and

said dispersive element has a resolution that is finer than the spectral acceptance range of said retroreflectors so as to provide each routed channel a spectral transfer function that is characterized by a band shape having a relatively flat top.

22. A wavelength router for receiving light having a first number, N, of spectral bands at an input port and directing subsets of the N spectral bands to respective ones of a second number, M, of output ports, the wavelength router comprising:

a first cylindrical lens having positive optical power in a first transverse dimension;

a second cylindrical lens having positive optical power in a second transverse dimension that is orthogonal to the first transverse dimension;

a transmissive dispersive element for dispersing light in the first transverse dimension;

a third cylindrical lens having positive optical power in the first transverse dimension; and

a plurality of N tiltable mirrors, each tiltable mirror intercepting a respective spectral band and directing that spectral band back toward said second cylindrical lens with an angular displacement depending on a state of that tiltable mirror;

wherein;

said first cylindrical lens, said second cylindrical lens, said transmissive dispersive element, and said plurality of N tiltable mirrors are disposed so that light emanating from the input port encounters said first cylindrical lens a first time, said second cylindrical lens a first time, said dispersive element a first time, said third cylindrical lens a first time, said plurality of N tiltable mirrors, said third cylindrical lens a second time, said dispersive element a second time, said second cylindrical lens a second time, and said first cylindrical lens a second time;

said first cylindrical lens operates said first time to collimate the light in the first transverse dimension, and said second time to focus the light in the first transverse dimension on the output ports;

said second cylindrical lens operates said first time to collimate the light in the second transverse dimension, and said second time to focus the light in the second transverse dimension; and

said third cylindrical lens operates said first time to focus the light in the first transverse dimension onto said plurality of N tiltable mirrors, and said second time to collimate the light in the first transverse dimension;

said dispersive element operates said first time to impart an angular separation among the spectral bands in the first transverse dimension so that the spectral bands encounter their respective tiltable mirrors, and operates said second time to remove said angular separation among the spectral bands in the first transverse dimension;

whereupon each spectral band is brought to a focus in both the first and second transverse dimensions at an output port determined by the state of the respective tiltable mirror.

23. The wavelength router of claim 22 wherein said dispersive element has a resolution significantly less than a separation between spectral bands.

24. The wavelength router of claim 23 wherein the resolution is achieved by a differential path length greater than about 3 cm.

25. The wavelength router of claim 22 wherein:

each of said tiltable mirrors has a geometric dimension that defines a respective spectral acceptance range; and

said dispersive element has a resolution that is finer than the spectral acceptance range of said tiltable mirrors so as to provide each routed channel a spectral transfer function that is characterized by a band shape having a relatively flat top.

26. A wavelength router for receiving light having a first number, N, of spectral bands at an input port and directing subsets of the N spectral bands to respective ones of a second number, M, of output ports, the wavelength router comprising:

a first cylindrical lens having positive optical power in a first transverse dimension;

a second cylindrical lens having positive optical power in a second transverse dimension that is orthogonal to the first transverse dimension;

a reflective dispersive element for dispersing light in the first transverse dimension; and

a plurality of N tiltable mirrors, each intercepting a respective spectral band and directing that spectral band back toward said first cylindrical lens with an angular displacement depending on a state of that tiltable mirror;

wherein;

said first cylindrical lens, said second cylindrical lens, said dispersive element, and said plurality of N tiltable mirrors are disposed so that light emanating from the input port encounters, in order, said first cylindrical lens a first time, said second cylindrical lens a first time, said dispersive element a first time, said second cylindrical lens a second time, said first cylindrical lens a second time, said plurality of N tiltable mirrors, said first cylindrical lens a third time, said second cylindrical lens a third time, said dispersive element a second time, said second cylindrical lens a fourth time, and said first cylindrical lens a fourth time;

said first cylindrical lens operates said first time to collimate the light in the first transverse dimension, said second time to focus the light in the first transverse dimension onto said plurality of N tiltable mirrors, said third time to collimate the light in the first transverse dimension, and said fourth time to focus the light in the first transverse dimension on the output ports;

said second cylindrical lens operates to collimate the light in the second transverse dimension upon passage of the light through said second cylindrical lens said first and second times, and to focus the light in the second transverse dimension upon passage of the light through said second cylindrical lens said third and fourth times; and

said dispersive element operates said first time to impart an angular separation among the spectral bands in the first transverse dimension so that the spectral bands encounter their respective tiltable mirrors, and operates said second time to remove said angular separation among the spectral bands in the first transverse dimension;

whereupon each spectral band is brought to a focus in both the first and second transverse dimensions at an output port determined by the state of the respective tiltable mirror.

27. The wavelength router of claim 26 wherein said dispersive element has a resolution significantly less than a separation between spectral bands.

28. The wavelength router of claim 27 wherein the resolution is achieved by a differential path length greater than about 3 cm.

29. The wavelength router of claim 26 wherein:

each of said tiltable mirrors has a geometric dimension that defines a respective spectral acceptance range; and

said dispersive element has a resolution that is finer than the spectral acceptance range of said tiltable mirrors so as to provide each routed channel a spectral transfer function that is characterized by a band shape having a relatively flat top.