Angular dispersion amplification method and apparatus for optical demultiplexing

• US 7,139,447 B1
• Filed: 04/19/2002
• Issued: 11/21/2006
• Est. Priority Date: 04/21/2001
• Status: Expired due to Fees

• Current Assignee: Santanu Basu
• Original Assignee: Santanu Basu
• Inventors: Basu, Santanu
• Primary Examiner(s): ST CYR, DANIEL
• Application Number:
  US10/126,758
• Time in Patent Office: 1,677 Days
• Field of Search: 385/14, 385/15, 385/31, 385/33, 385/36, 385/37
• US Class Current: 385/14
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0205 Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
• CPC Class Codes: G01J 3/14 using refracting elements, e.g. prisms G01J3/18, G01J3/26 take precedence prisms per se G02B5/04
• CPC Class Codes: G02B 27/141 using dichroic mirrors
• CPC Class Codes: G02B 6/2706 as bulk elements, i.e. free space arrangements external to a light guide, e.g. polarising beam splitters
• 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 6/2931 Diffractive element operating in reflection
• CPC Class Codes: G02B 6/29311 Diffractive element operating in transmission
• CPC Class Codes: G02B 6/29373 utilising a bulk dispersive element, e.g. prism
• CPC Class Codes: G02B 6/34 utilising prism or grating G02B6/293 takes precedence

Abstract

An optical demultiplexer, having an angular dispersion generator followed by an angular amplifier. The angular dispersion generator disperses an incident optical signal into a plurality of channels. While traveling through the angular dispersion amplifier, the channels with incident angles larger than a critical angle are internally totally reflected, and the channels with incident angles smaller than the critical angle are partly reflected, and partly transmitting into an ambient medium. The transmitting part of the channels are thus further dispersed and demultiplexed.

Claims

1. An optical demultiplexer, comprising:

an angular dispersion generator, operative to disperse an incident optical signal into a wavelength plurality of channels each being angularly separated from at least one of the others; and

an angular dispersion amplifier, operative to receive the dispersed optical signal and amplify an angular separation of at least one of the wavelength channels with respect to at least one other wavelength channel in the angularly dispersed optical signal,

wherein the angular dispersion amplifier comprises an internal reflection interface with a critical angle, and wherein the channels which are further dispersed having an incident angle smaller than the critical angle.

2. The optical demultiplexer as recited in claim 1, wherein the angular dispersion generator comprises a wavelength separation element.

3. The optical demultiplexer as recited in claim 1, wherein the angular dispersion generator comprises a diffraction grating.

4. The optical demultiplexer as recited in claim 1, wherein the angular dispersion generator comprises a prism.

5. The optical demultiplexer as recited in claim 1, wherein the angular dispersion amplifier has a refractive index greater than that of a surrounding ambient medium.

6. The optical demultiplexer as recited in claim 1, wherein the angular dispersion generator and the angular dispersion amplifier are integrated in a common structure.

7. The optical demultiplexer as recited in claim 1, further comprising a polarizer disposed between the angular dispersion generator and the angular dispersion amplifier.

8. The optical demultiplexer as recited in claim 1, further comprising an anti-reflection coating on at least one surface of the angular dispersion amplifier.

9. The optical demultiplexer as recited in claim 1, wherein the angular dispersion amplifier includes a round optical wedge window, which has a wedge with an wedge angle along which propagation direction of an incident signal is variable upon rotation of the wedge.

10. The demultiplexer as recited in claim 1, wherein the angular dispersion amplifier has an internal reflection interface which totally reflects the remaining channels that are not further dispersed by the angular dispersion amplifier.

11. The demultiplexer as recited in claim 1, wherein the angular dispersion amplifier comprises a prism truncated to have a pentagonal cross section.

12. The demultiplexer as recited in claim 1, wherein the angular dispersion amplifier includes a round optical wedge window, which further comprises a round optical window having a perimeter and two wedges located on two distal parts of the perimeter.

13. The demultiplexer as recited in claim 1, wherein the angular dispersion amplifier includes a round optical edge having an inclined edge and a plurality of surfaces polished for low loss optical transmission.

14. The demultiplexer as recited in claim 1, wherein the angular dispersion amplifiers includes a wedge slab having two inclined ends.

15. The demultiplexer as recited in claim 1, further comprising an additional angular dispersion amplifier disposed along an optical path of the channel further dispersed by the angular dispersion amplifier.

16. The demultiplexer as recited in claim 1, further comprising an additional angular dispersion amplifier disposed along an optical path of the channels that are not further dispersed by the angular dispersion amplifier.

17. The demutiplexer as recited in claim 1, wherein the angular dispersion generator comprises an element to induce optical interference.

18. A method of multiplexing an input, multichannel optical signal, comprising:

communicating the input optical signal to an angular dispersion generator;

dispersing the input optical signal to define a plurality of angular dispersion channels;

communicating a plurality of the channels to be incident upon at least one angular dispersion amplifier having an internal reflection interface; and

adjusting the orientation of the internal reflection interface with respect to the incident angles of the channels, such that the channels having incident angles larger than a critical angle at the internal reflection interface are internally reflected, and the channels having incident angles smaller than the critical angle are partly transmitted through the internal reflection interface.

19. An optical demultiplexer, comprising:

an angular dispersion generator, operative to disperse an incident optical signal into a wavelength plurality of channels each being angularly separated from at least one of the others; and

an angular dispersion amplifier, operative to receive the dispersed optical signal and amplify an angular separation of at least one of the wavelength channels with respect to at least one other wavelength channel in the angularly dispersed optical signal;

wherein the angular dispersion amplifier has an internal reflection interface which totally reflects the remaining channels that are not further dispersed by the angular dispersion amplifier.

20. The demultiplexer as recited in claim 19, wherein orientation of the internal reflection interface is adjustable, such that the number of the channels to be further dispersed by the angular dispersion amplifier is controllable.

21. The demultiplexer as recited in claim 19, wherein the angular dispersion generator includes a grating, the angular dispersion amplifier includes a prism, and the grating is directly attached on an inclined surface of the prism.

22. The demultiplexer as recited in claim 21, wherein the angular dispersion amplifier includes a prism that has two inclined surfaces and an internal reflection interface.

23. A demultiplexer for selectively demultiplexing a multi-channel signal, comprising:

an angular dispersion generator, operative to receive an input multi-channel signal, and to split the multi-channel signals into a plurality of angularly dispersed channels separated from each other by an angular dispersion;

a first angular dispersion amplifier, operative to receive the angularly dispersed channels and to selectively extract a first fraction of the angularly dispersed channels by amplifying the angular dispersion thereof; and

at least one second angular dispersion amplifier so arranged to selectively extract at least a second fraction of the angularly dispersed channels by amplifying angular dispersion.

24. The demultiplexer as recited in claim 23, wherein a material for forming the angular dispersion amplifier includes silicon.

25. The demultiplexer as recited in claim 23, wherein the angular dispersion generator, the angular dispersion amplifier, an optical path of the input multi-channel signal, and at least one optical path of the angularly dispersed channels are integrated into a common substrate.

26. A demultiplexer for selectively demultiplexing a multi-channel signal, comprising:

an angular dispersion generator, operative to receive an input multi-channel signal, and to split the multi-channel signals into a plurality of angularly dispersed channels separated from each other by an angular dispersion;

a first angular dispersion amplifier, operative to receive the angularly dispersed channels and to selectively extract a first fraction of the angularly dispersed channels by amplifying the angular dispersion thereof;

wherein the first angular dispersion amplifier has an internal reflection interface with a critical angle such that the angularly dispersed channels incident onto the internal reflection interface with an incident angle smaller than the critical angle are partly reflected and partly transmitted, while the angularly dispersed channels incident onto the internal reflection interface with an incident angle larger than the critical angle are totally reflected.

27. The demultiplexer as recited in claim 26, wherein orientation of the internal reflection interface relative to the incident angles of the angularly dispersed channels is adjustable such that selection of the first fraction of the angularly dispersed channels is tunable.

28. The demultiplexer as recited in claim 26, further comprising a dispersion adjusting means for applying an external force to the angular dispersion generator, so as to modify angular dispersion of the angularly dispersed channels generated by the angular dispersion generator.

29. An optical demultiplexer, comprising:

an angular dispersion generator, operative to disperse an incident optical signal into a wavelength plurality of channels each being angularly separated from at least one of the others; and

an angular dispersion amplifier, operative to receive the dispersed optical signal and amplify an angular separation of at least one of the wavelength channels with respect to at least one other wavelength channel in the angularly dispersed optical signal;

wherein the angular dispersion amplifier comprises an internal reflection interface with a critical angle, and wherein the channels which are internally totally reflected have incident angles larger than the critical angle.

30. An optical demultiplexer, comprising:

an angular dispersion generator, operative to disperse an incident optical signal into a wavelength plurality of channels each being angularly separated from at least one of the others; and

an angular dispersion amplifier, operative to receive the dispersed optical signal and amplify an angular separation of at least one of the wavelength channels with respect to at least one other wavelength channel in the angularly dispersed optical signal;

wherein the angular dispersion amplifier includes a round optical wedge window, which has a wedge with an wedge angle along which propagation direction of an incident signal is variable upon rotation of the wedge.

31. A demultiplexer for selectively demultiplexing a multi-channel signal, comprising:

an angular dispersion generator, operative to receive an input multi-channel signal, and to split the multi-channel signals into a plurality of angularly dispersed channels separated from each other by an angular dispersion;

a first angular dispersion amplifier, operative to receive the angularly dispersed channels and to selectively extract a first fraction of the angularly dispersed channels by amplifying the angular dispersion thereof; and

at least one second angular amplifier so arranged to further amplify the angular dispersion of the first fraction of the angularly dispersed channels extracted by the first angular dispersion amplifier.

32. A demultiplexer for selectively demultiplexing a multi-channel signal, comprising:

an angular dispersion generator, operative to receive an input multi-channel signal, and to split the multi-channel signals into a plurality of angularly dispersed channels separated from each other by an angular dispersion;

a first angular dispersion amplifier, operative to receive the angularly dispersed channels and to selectively extract a first fraction of the angularly dispersed channels by amplifying the angular dispersion thereof; and

one second and one third angular dispersion amplifier so arranged to selectively extract a second fraction of the angularly dispersed channel and to further amplify the angular dispersion of the first fraction of the angularly dispersed channels extracted by the first angular dispersion amplifier, respectively.