Optical wavelength router using reflective surfaces to direct output signals

• US 6,594,082 B1
• Filed: 02/26/2001
• Issued: 07/15/2003
• Est. Priority Date: 06/05/2000
• Status: Expired due to Term

• Current Assignee: II-VI Delaware, Inc. (Coherent Corp.)
• Original Assignee: Avanex Corporation (Oclaro (North America), Inc.)
• Inventors: Peng, Song, Li, Ming
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): Harrington, Alicia M.
• Application Number:
  US09/794,590
• Time in Patent Office: 869 Days
• Field of Search: 359/290, 359/291, 359/296, 359/618, 359/627, 359/122, 385/11
• US Class Current: 359/618
• CPC Class Codes: G02B 6/272 comprising polarisation means for beam splitting and combining
• CPC Class Codes: G02B 6/2766 Manipulating the plane of polarisation from one input polarisation to another output polarisation, e.g. polarisation rotators, linear to circular polarisation converters
• CPC Class Codes: G02B 6/278 Controlling polarisation mode dispersion [PMD], e.g. PMD compensation or emulation PMD minimised transmission systems H04B10/2569
• CPC Class Codes: G02B 6/2931 Diffractive element operating in reflection
• 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 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 2011/0024 using space switching
• CPC Class Codes: H04Q 2011/003 using switches based on microelectro-mechanical systems [MEMS]

Abstract

An optical wavelength router utilizes a dispersive medium (e.g., a diffraction grating) and reflective surfaces. The dispersive medium separates an input optical signal (light beam) into a plurality of components, for example by wavelengths. The reflective surfaces convert the components into separate output beams traveling in the desired directions. The number and the direction of the output beams can be controlled by manipulating the angle of incidence at which the components strike the reflective surfaces. A micro-mirror array modulator serves as the reflective surfaces. Each mirror in the micro-mirror array modulator is positioned to direct individual components into a number of output signals. Alternatively, a polarization steering device which includes a polarization modulator and at least one birefringent element in addition to reflective surfaces is utilized. A Wollaston prism with a reflective surface may also be used.

Claims

1. An optical router comprising:

at least one dispersive medium;

at least one reflective surface optically coupled to said at least one dispersive medium;

wherein an incident beam is separated into individual components by said at least one dispersive medium, each one of said individual components being reflected back to said at least one dispersive medium from said reflective surface and being recombined into one or more separate output signals;

a first birefringent element directing said individual components having a first polarization state and said individual components having a second polarization state in different direction;

a polarization modulator comprising

a rotating segment to rotate the polarization of said individual components; and

a non-rotating segment to not rotate the polarization of said individual components;

wherein said segments are aligned along an axis substantially perpendicular to the direction in which said individual components travel through said polarization modulator; and

a second birefringent element directing said individual components having a first polarization state and said individual components having a second polarization state to different parts of said at least one reflective surface.

2. The optical router of claim 1 further comprising:

a lens located to focus said individual components onto segments of said polarization modulator.

3. The optical router of claim 1 wherein said at least one reflective surface is at least one surface of an angled reflector.

4. The optical router of claim 1 further comprising:

at least one polarization rotating element placed between said first birefringent element and said second birefringent element.

5. The optical router of claim 4 wherein the thickness of said first birefringent element and the thickness of said second birefringent element are substantially the same in the direction in which said individual components propagate.

6. The optical router of claim 4 wherein each of said individual components travel substantially the same distance between said at least one dispersive medium and said at least one reflective surface.

7. The optical router of claim 4 wherein the thickness of said birefringent element and the thickness of said second birefringent element are adjusted to minimize polarization mode dispersion in said optical wavelength router.

8. The optical router of claim 4 wherein the thickness of said birefringent element and the thickness of said second birefringent element are optimized to minimize polarization mode dispersion in said optical wavelength router while maintaining a substantially equal travel distance of said individual components between said at least one dispersive element and said at least one reflective surface.

9. The optical router of claim 4 wherein the combined thickness of said first birefringent element and said second birefringent element are minimized.

10. The optical router of claim 4 wherein said polarization rotating element is a half-wave waveplate with an optic axis inclined at forty-five degrees in the plane orthogonal to the direction in which individual components travel through said half-wave waveplate.

11. The optical router of claim 10 wherein at least one of said first and second birefringent elements comprises calcite crystals.

12. The optical router of claim 10 wherein at least one of said first and second birefringent elements comprises yttrium vanadate.

13. The optical router of claim 10 wherein at least one of said first and second birefringent elements comprises yttrium orthovanadate.

14. The optical router of claim 4 wherein said at least one reflective surface is a surface of a Wollaston prism farthest from the surface through which said individual components enter said at least one Wollaston prism, said at least one Wollaston prism comprising:

a first birefringent prism; and

a second birefringent prism adjacent to said first birefringent prism;

wherein the optic axis of said first birefringent prism is perpendicular to the optic axis of said second birefringent prism; and

wherein the optic axis of said first birefringent prism and the optic axis of said second birefringent prism are perpendicular to the direction in which said individual components travel through said first birefringent prism.

15. A method of routing a multiplexed optical signal comprising the acts of:

spatially separating said optical signal in a dispersive medium into individual components;

reflecting each of said individual components at different angles back into the dispersive medium, wherein said reflecting comprises;

dividing each of said individual components into sub-components of different polarization states;

passing said sub-components through a Wollaston prism, said Wollaston prism comprising;

a first birefringent prism;

a second birefringent prism adjacent to said first birefringent prism; and

a reflective coating on the inner surface farthest away from said dispersive medium;

wherein the optic axis of said first birefringent prism is perpendicular to the optic axis of said second birefringent prism; and

wherein the optic axis of said first birefringent prism and the optic axis of said second birefringent prism are perpendicular to the direction in which said sub-components travel through said first birefringent prism;

directing each of said sub-components to reflective surfaces positioned at different angles; and

combining said individual components in the dispersive medium into output signals.