N-port reconfigurable DWDM multiplexer and demultiplexer

• US 6,137,927 A
• Filed: 12/18/1998
• Issued: 10/24/2000
• Est. Priority Date: 01/16/1998
• Status: Expired due to Fees

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Nolan, Daniel A., Keck, Donald B.
• Primary Examiner(s): Lee, John D.
• Assistant Examiner(s): HAHM, SARAH UH YOUNG
• Application Number:
  US09/216,435
• Time in Patent Office: 676 Days
• Field of Search: 385/15, 385/24, 385/30, 385/31, 359/124, 359/127, 359/128
• US Class Current: 385/24
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/12011 characterised by the arrayed waveguides, e.g. comprising a filled groove in the array section
• CPC Class Codes: G02B 6/2935 Mach-Zehnder configuration, i.e. comprising separate splitting and combining means
• CPC Class Codes: G02B 6/29358 Multiple beam interferometer external to a light guide, e.g. Fabry-Pérot, etalon, VIPA plate, OTDL plate, continuous interferometer, parallel plate resonator G02B6/29347, G02B6/29349, G02B6/2935, G02B6/29361 take precedence; resonator evanescently coupled to light guide G02B6/29335
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04J 14/03 WDM arrangements ADM arrangements H04J14/0202; WDM network architectures H04J14/0278

Abstract

An N-port optical wavelength division multiplexer and demultiplexer includes two evanescent wave couplers connected by N optical paths. Each of the optical paths includes wavelength-selecting elements that are used to select specific wavelengths of light. Light signals composed of N wavelengths of light introduced to an exterior port in one of the couplers are split substantially equally among all the optical paths within the coupler, so that each optical path exiting the coupler includes light of all the wavelengths initially introduced to the coupler. The wavelength selecting elements disposed on each optical path are situated to direct the light in a manner such that light of only the selected wavelengths interferes constructively at a given exterior coupler port and other wavelengths interfere destructively. Consequently, optical signals composed of N wavelengths may be demultiplexed such that N optical paths carry light having one wavelength. Conversely, N optical paths carrying light signals having only one wavelength can be multiplexed into a signal having wavelengths λ₁, λ₂, . . . λ_N. The multiplexed signal is then coupled into up to M+O exterior ports.

Claims

1. A monolithic optical device for wavelength division multiplexing or demultiplexing a plurality of light signals, each of said plurality of light signals is characterized by a wavelength or a plurality of wavelengths and a signal light power, said optical device comprising:

a first evanescent wave coupler having M exterior ports and N interior ports, wherein the signal light power is uniformly coupled between said M exterior ports and said N interior ports;

a second evanescent wave coupler having N interior ports and O exterior ports, wherein the signal light power is uniformly coupled between said N interior ports and said O exterior ports;

N optical paths for connecting each of said N interior ports of said first evanescent coupler, respectively, to a corresponding one of said N interior ports of said second evanescent coupler; and

,

a plurality of wavelength selecting elements disposed on each of said N optical paths for routing each of the plurality of light signals to any selected M exterior port or O exterior port on the basis of the wavelength or the plurality of wavelengths.

2. The optical device of claim 1, wherein the wavelength selecting elements are adjustable in accordance with a network command.

3. The optical device of claim 1, wherein at least one of the evanescent couplers is a fused waveguide fiber coupler.

4. The optical device of claim 1, wherein at least one of the first evanescent coupler or second evanescent couplers is a planar coupler.

5. The optical device of claim 4, wherein the planar coupler is an N×

N free-space planar coupler.

6. The optical device according to claim 1, wherein the plurality of wavelength selecting elements comprises:

a plurality of reflective elements disposed on the N optical paths, wherein each of said plurality of reflective elements is tuned to reflect light having a specific wavelength selected from the plurality of wavelengths and separated from an adjacent reflective element by an interval.

7. The optical device according to claim 6, wherein the plurality of reflective elements comprise a plurality of mirrors.

8. The optical device according to claim 6, wherein the plurality of reflective elements comprise a plurality of gratings.

9. The optical device of claim 8, wherein each of the N optical paths provides a distinctive phase shift to each of the plurality of wavelengths of light propagating in the N optical paths.

10. The optical device of claim 9, wherein the distinctive phase shift causes constructive interference with a selected light signal and destructive interference with all other light signals propagating in the N optical paths, when one of the plurality of gratings routes the selected light signal to the selected M exterior or O exterior port.

11. The optical device of claim 10, wherein the N optical paths comprise:

a plurality of optical waveguide fibers, wherein each of said plurality of optical waveguide fibers has a refractive index, a refractive index delta, a length, and a core diameter.

12. The optical device of claim 11, wherein routing the selected light signal to the selected M exterior or O exterior port is adjusted by varying the refractive index delta.

13. The optical device of claim 11, wherein routing the selected light signal to the selected M exterior or O exterior port is adjusted by varying the length.

14. The optical device of claim 11, wherein routing the selected light signal to the selected M exterior or O exterior port is adjusted by varying the core diameter.

15. The optical device of claim 10, wherein routing the selected light signal to the selected M exterior or O exterior port is adjusted by varying the interval, thereby causing the distinctive phase shift to create constructive interference with the selected light signal and, destructive interference with all other light signals.

16. The optical device of claim 15, wherein the interval is varied by a distance δ

characterized by the equation;

##EQU3## wherein λ

is the wavelength of the selected light signal, n is the refractive index of the optical fiber, and M is an integer.

17. The optical device of claim 8, wherein each of the plurality of gratings is at least partially transmissive.

18. The optical device of claim 1, wherein the wavelength selective element further comprises:

a plurality of gratings disposed on the N optical paths, wherein each of said plurality of gratings is tuned to reflect light having a specific wavelength from among the plurality of wavelengths and separated from an adjacent one of said plurality of gratings by an interval;

a plurality of heaters disposed on the N optical paths and interleaved with said plurality of gratings; and

,

a configuration controller connected to each of said plurality of heaters, wherein said configuration controller dynamically changes the routing of each of the plurality of light signals to the selected M exterior or O exterior port by individually actuating selected ones of said plurality of heaters in response to a network command.

19. The optical device of claim 18, wherein each of the N optical paths provides a distinctive phase shift to each of the plurality of wavelengths of light propagating in the N optical paths.

20. The optical device of claim 19, wherein the distinctive phase shift causes constructive interference with a selected light signal and destructive interference with all other light signals propagating in the N optical paths, when one of the plurality of gratings routes the selected light signal to the selected M exterior or O exterior port.

21. The optical device of claim 20, wherein the N optical path lengths comprise:

a plurality of optical waveguide fibers, wherein each of said plurality of optical waveguide fibers has a refractive index delta.

22. The optical device of claim 21, wherein the heaters dynamically change the routing of the selected light signal to the selected M exterior or O exterior port by heating selected ones of the plurality of optical waveguide fibers to thereby vary the refractive index delta.

23. The optical device of claim 18, wherein the plurality of heaters further comprise:

a plurality of electrodes individually connected to the configuration controller, wherein each of said plurality of electrodes is individually actuated by the configuration controller to provide heat energy to the selected ones of the plurality of heaters in accordance with the network command.

24. The optical device of claim 1, wherein the wavelength selective element further comprises:

a plurality of sub-elements disposed on the N optical paths, wherein each of said plurality of sub-elements is tunable to change the phase of each of the plurality of light signals in accordance with the wavelength; and

,

a configuration controller connected to each of said plurality of sub-elements, wherein said configuration controller dynamically changes the routing of the plurality of light signals to the selected M exterior or O exterior port by individually actuating said plurality of sub-elements in accordance with a network command.

25. The optical device of claim 24, wherein each of the plurality of sub-elements comprise:

a lithium niobate waveguide element; and

a voltage modulator connected to said lithium niobate waveguide element, wherein said voltage modulator is individually controlled by said configuration controller and individually actuates said lithium niobate waveguide element by changing the electromagnetic field around said lithium niobate waveguide element.

26. The optical device of claim 25, wherein changing the electromagnetic field induces a phase shift causing constructive interference of a selected light signal and destructive interference of all other light signals propagating in the N optical paths, when routing the selected light signal to the selected M exterior or O exterior port.

27. The optical device of claim 24, wherein each of the plurality of sub-elements comprise:

an indium phosphate waveguide element; and

a voltage modulator connected to said indium phosphate waveguide element, wherein said voltage modulator is individually controlled by said configuration controller and individually actuates said indium phosphate waveguide element by changing the electromagnetic field around said indium phosphate waveguide element.

28. The optical device of claim 27, wherein changing the electromagnetic field induces a phase shift causing constructive interference with a selected light signal and destructive interference with all other light signals propagating in the N optical paths, when routing the selected light signal to the selected M exterior or O exterior port.

29. A method for manufacturing a device for wavelength division multiplexing or demultiplexing of light signals, each of said light signals being characterized by a wavelength or a plurality of wavelengths and a signal light power, said method comprising the steps of:

forming a first evanescent wave coupler having M exterior ports and N interior ports, wherein the signal light power is uniformly coupled between said M exterior ports and said N interior ports;

forming a second evanescent wave coupler having N interior ports and O exterior ports, wherein the signal light power is uniformly coupled between said N interior ports and said O exterior ports; and

forming N optical paths to connect each of said N interior ports of said first coupler, respectively, to a corresponding one of said N interior ports of said second coupler; and

,

disposing a plurality of wavelength selecting elements on each of said N optical paths, wherein said wavelength selecting element routes light signals to a selected one of said M exterior or O exterior port on the basis of the wavelength or the plurality of wavelengths.

30. The method of claim 29 wherein said forming steps are carried out such that the device is monolithically formed.

31. The method of claim 29, wherein at least one of the first evanescent coupler or second evanescent coupler is a fused waveguide fiber coupler.

32. The method of claim 29, wherein at least one of the first evanescent coupler or second evanescent coupler is a planar coupler.

33. The method of claim 32, wherein at least one of the first evanescent coupler or second evanescent coupler is an N×

N free-space planar coupler.

34. A method for wavelength division multiplexing or demultiplexing of a plurality of light signals in an optical device having a first evanescent wave coupler with M exterior ports and N interior ports, a second evanescent wave coupler having N interior ports and O exterior ports, and N optical paths that connect each of said N interior ports of said first evanescent coupler to a corresponding one of said N interior ports of said second evanescent coupler, said method comprising the steps of:

providing a plurality of wavelength selecting elements disposed on each of the N optical paths; and

,

routing selected ones of the plurality of light signals to any selected M exterior or O exterior port on the basis of a wavelength or a plurality of wavelengths, wherein each of the plurality of light signals is characterized by said wavelength or said plurality of wavelengths.

35. The method for wavelength division multiplexing or demultiplexing of a plurality of light signals of claim 34, wherein the plurality of wavelength selecting elements are heatable grating elements and the step of routing further comprises:

providing a distinctive phase shift to each of the plurality of wavelengths of light propagating in the N optical paths, wherein said distinctive phase shift causes constructive interference with a selected light signal and destructive interference with all other light signals propagating in the N optical paths;

reflecting selected ones of the plurality of wavelengths of light, wherein each of the heatable grating elements are tuned to a specific wavelength of light to thereby reflect a light signal characterized by said specific wavelength of light; and

,

heating selected ones of the heating elements to thereby dynamically change the routing of the selected ones of the plurality of light signals to any selected M exterior or O exterior port.