Add/drop acousto-optic filter

• US 6,357,913 B1
• Filed: 05/23/2000
• Issued: 03/19/2002
• Est. Priority Date: 02/12/1998
• Status: Expired due to Term

• Current Assignee: Novera Optics, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Novera Optics, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Sorin, Wayne V., Kim, Byoung Yoon, Yun, Seok Hyun
• Primary Examiner(s): Healy, Brian
• Application Number:
  US09/577,197
• Time in Patent Office: 665 Days
• Field of Search: 385/7, 385/24, 385/27, 385/28, 385/29, 385/31, 385/39, 385/42, 385/47, 385/11, 385/123, 385/126, 385/127, 359/115, 359/116, 359/124, 359/122, 359/127, 359/130, 359/154, 359/180, 359/189, 359/195, 359/188, 359/181
• US Class Current: 383/28
• CPC Class Codes: G02B 6/02071 Mechanically induced gratings, e.g. having microbends G02B6/02066 takes precedence; mode converters G02B6/14
• CPC Class Codes: G02F 1/0134 in optical waveguides
• CPC Class Codes: G02F 1/125 in an optical waveguide structure
• CPC Class Codes: G02F 2201/02 fibre
• CPC Class Codes: G02F 2203/055 wavelength filtering
• CPC Class Codes: G02F 2203/585 Add/drop devices
• CPC Class Codes: H04J 14/0208 Interleaved arrangements
• CPC Class Codes: H04J 14/0209 Multi-stage arrangements, e.g. by cascading multiplexers or demultiplexers
• CPC Class Codes: H04J 14/0213 Groups of channels or wave bands arrangements

Abstract

A drop AOTF has a first AOTF that includes an optical fiber with a longitudinal axis, an acoustic wave propagation member with a proximal end and a distal end and an acoustic wave propagation member. The acoustic wave propagation member propagating an acoustic wave from the proximal to the distal end of the acoustic wave propagation member. An optical circulator, with first, second and third ports, is coupled to the first AOTF at the third port. A mode coupler is coupled to the first AOTF. A orthogonal-polarization reflective mirror is coupled to the mode coupler.

Claims

1. An acousto-optic filter, comprising:

a first acousto-optic mode converter including,

an optical fiber with a longitudinal axis,

an acoustic wave propagation member with a proximal end and a distal end, the distal end being coupled to the optical fiber, the acoustic wave propagation member propagating an acoustic wave from the proximal to the distal end, and

at least one acoustic wave generator coupled to the proximal end of the acoustic wave propagation member;

an optical circulator with first, second and third ports, the first acousto-optic mode converter being coupled to the third port;

a mode coupler coupled to the first acousto-optic mode converter; and

an orthogonal-polarization reflecting mirror coupled to the mode coupler.

4. The filter of claim 1, wherein a wavelength of an optical signal coupled from one mode to another mode is changed by varying the frequency of a signal applied to the acoustic wave generator.

5. The filter of claim 1, wherein the acoustic wave generator produces multiple acoustic signals with individual controllable strengths and frequencies and each of the acoustic signals provides a coupling between one mode to a different mode.

6. The filter of claim 1, wherein an amount of an optical signal coupled to one mode to another mode is changed by varying an amplitude of a signal applied to the acoustic wave generator.

7. The filter of claim 1, wherein the mode converter converts at least one spatial mode to a different spatial mode.

8. The filter of claim 1, wherein the mode converter converts at least one core mode to another core mode.

9. The filter of claim 1, wherein the mode converter converts at least one core more to a cladding mode.

10. The filter of claim 1, wherein the mode converter converts at least one cladding mode to a core mode.

11. The filter of claim 1, further comprising:

a delay coupled to the mode coupler.

2. An add/drop acousto-optic filter, comprising:

a first acousto-optic mode converter including,

an optical fiber with a longitudinal axis,

an acoustic wave propagation member with a proximal end and a distal end, the distal end being coupled to the optical fiber, the acoustic wave propagation member propagating an acoustic wave from the proximal to the distal end, and

at least one acoustic wave generator coupled to the proximal end of the acoustic wave propagation member;

a first optical circulator with first, second and third ports, the first acousto-optic mode converter being coupled to the third port and a first optical transmission line carrying optical signals λ

₁-λ

_n being coupled to the first port;

a first mode coupler coupled to the first acousto-optic mode converter and positioned between the first optical circulator and the first acousto-optic mode converter;

a first orthogonally-polarization reflecting mirror coupled to the first mode coupler;

a second optical circulator with at least a first, second and third ports, the first acousto-optic mode converter being coupled to the first port and the third port being coupled to a second transmission line;

a second mode coupler positioned between the second optical circulator and the first mode coupler;

a second orthogonal-polarization reflecting mirror coupled to the second mode coupler;

wherein at least one signal of the optical signals λ

₁-λ

_n is dropped at the second port of the first optical circulator and the non-dropped optical signals λ

₁-λ

_n are transmitted from the second transmission line of the second optical circulator.

12. The filter of claim 2, wherein a wavelength coupled from one mode to another mode is changed by varying the frequency of a signal applied to the acoustic wave generator.

13. The filter of claim 2, wherein the acoustic wave generator produces multiple acoustic signals with individual controllable strengths and frequencies and each of the acoustic signals provides a coupling between one mode to a different mode.

14. The filter of claim 2, wherein an amount of an optical signal coupled to one mode to another mode is changed by varying an amplitude of a signal applied to the acoustic wave generator.

15. The filter of claim 2, wherein each mode converter converts at least one spatial mode to a different spatial mode.

16. The filter of claim 2, wherein at least one of the mode converters converts at least one core mode to another core mode.

17. The filter of claim 2, wherein at least one of the mode converters converts at least one core more to a cladding mode.

18. The filter of claim 2, wherein at least one of the mode converters converts at least one cladding mode to a core mode.

19. The filter of claim 2, further comprising:

a first delay coupled to the first mode coupler; and

a second delay coupled to the second mode coupler.

3. An add/drop acousto-optic filter, comprising:

a first acousto-optic mode converter including,

an optical fiber with a longitudinal axis,

an acoustic wave propagation member with a proximal end and a distal end, the distal end being coupled to the optical fiber, the acoustic wave propagation member propagating an acoustic wave from the proximal to the distal end, and

at least one acoustic wave generator coupled to the proximal end of the acoustic wave propagation member;

a first optical circulator with first, second and third ports, the first acousto-optic mode converter being coupled to the third port and a first optical transmission line carrying optical signals λ

₁-λ

_n being coupled to the first port;

a first mode coupler coupled to the first acousto-optic mode converter and positioned between the first optical circulator and the first acousto-optic mode converter;

a first orthogonally-polarization reflecting mirror coupled to the first mode coupler;

a second optical circulator with at least a first, second and third ports, the first acousto-optic mode converter being coupled to the first port and the third port being coupled to a second transmission line;

a second mode coupler positioned between the second optical circulator and the first mode coupler;

a second orthogonal-polarization reflecting mirror coupled to the second mode coupler;

a second acousto-optic mode converter coupled to and positioned between the second mode coupler and the second optic circulator;

the second acousto-optic mode converter including,

an acoustic wave propagation member with a proximal end and a distal end, the distal end being coupled to the optical fiber, the acoustic wave propagation member propagating an acoustic wave from the proximal to the distal end, and

at least one acoustic wave generator coupled to the proximal end of the acoustic wave propagation member; and

wherein at least one signal of the optical signals λ

₁-λ

_n is dropped at the second port of the first optical circulator, and a signal λ

_n+1 is introduced at the second port of the second optical circulator, combined with the non-dropped optical signals λ

₁-λ

_n and are transmitted from the third port of the second optical circulator.

20. The filter of claim 3, wherein a wavelength coupled from one mode to another mode is changed by varying the frequency of a signal applied to at least one of the acoustic wave generators.

21. The filter of claim 3, wherein at least one of the acoustic wave generators produces multiple acoustic signals with individual controllable strengths and frequencies and each of the acoustic signals provides a coupling between one mode to a different mode.

22. The filter of claim 3, wherein an amount of an optical signal coupled to one mode to another mode is changed by varying an amplitude of a signal applied to at least one of the acoustic wave generators.

23. The filter of claim 3, wherein each mode converter converts at least one spatial mode to a different spatial mode.

24. The filter of claim 3, wherein at least one of the mode converters converts at least one core mode to another core mode.

25. The filter of claim 3, wherein at least one of the mode converters converts at least one core more to a cladding mode.

26. The filter of claim 3, wherein at least one of the mode converters converts at least one cladding mode to a core mode.

27. The filter of claim 3, further comprising:

a first delay coupled to the first mode coupler;

a second delay coupled to the second mode coupler; and

a third delay coupled to the third mode coupler.

28. An add/drop acousto-optic filter, comprising:

a first acousto-optic mode converter including,

an optical fiber with a longitudinal axis,

an acoustic wave propagation member with a proximal end and a distal end, the distal end being coupled to the optical fiber, the acoustic wave propagation member propagating an acoustic wave from the proximal to the distal end, and

at least one acoustic wave generator coupled to the proximal end of the acoustic wave propagation member;

a first optical circulator with first, second and third ports, the first acousto-optic mode converter being coupled to the third port and a first optical transmission line carrying optical signals λ

₁-λ

_n being coupled to the first port;

a first mode coupler coupled to the first acousto-optic mode converter and positioned between the first optical circulator and the first acousto-optic mode converter;

a first orthogonally-polarization reflecting mirror coupled to the first mode coupler;

a second optical circulator with at least a first, second and third ports, the first acousto-optic mode converter being coupled to the first port and the third port being coupled to a second transmission line;

a second mode coupler positioned between the second optical circulator and the first mode coupler;

a second orthogonal-polarization reflecting mirror coupled to the second mode coupler;

wherein at least one signal is λ

_n+1 added at the second port of the first optical circulator, and the optical signals λ

₁-λ

_n and λ

_n+1 are transmitted from the second transmission line of the second optical circulator.

29. An add/drop acousto-optic filter, comprising:

a first acousto-optic mode converter including,

an optical fiber with a longitudinal axis,

an acoustic wave propagation member with a proximal end and a distal end, the distal end being coupled to the optical fiber, the acoustic wave propagation member propagating an acoustic wave from the proximal to the distal end;

at least one acoustic wave generator coupled to the proximal end of the acoustic wave propagation member;

a first optical circulator with first, second and third ports, the first acousto-optic mode converter being coupled to the third port and a first optical transmission line carrying optical signals λ

₁-λ

_n being coupled to the first port;

a first mode coupler coupled to the first acousto-optic mode converter and positioned between the first optical circulator and the first acousto-optic mode converter;

a first orthogonally-polarization reflecting mirror coupled to the first mode coupler;

a second optical circulator with at least a first, second and third ports, the first acousto-optic mode converter being coupled to the first port and the third port being coupled to a second transmission line;

a second mode coupler positioned between the second optical circulator and the first mode coupler;

a second orthogonal-polarization reflecting mirror coupled to the second mode coupler;

a second acousto-optic mode converter coupled to and positioned between the second mode coupler and the second optic circulator;

the second acousto-optic mode converter including,

an acoustic wave propagation member with a proximal end and a distal end, the distal end being coupled to the optical fiber, the acoustic wave propagation member propagating an acoustic wave from the proximal to the distal end, and

at least one acoustic wave generator coupled to the proximal end of the acoustic wave propagation member;

a tunable notch filter positioned between the first and second acousto-optic mode converters; and

wherein at least one optical signal λ

_n+1 is added at the second port of the first optical circulator, and at least one signal λ

_n+2 is introduced at the second port of the second optical circulator, combined with the optical signals λ

₁-λ

_n and are transmitted from the third port of the second optical circulator.

30. A multiplexer, comprising:

a mode converter including an optical fiber with a longitudinal axis, a core and a cladding in a surrounding relationship to the core, the optical fiber having multiple spatial modes;

an optical circulator with at least first, second and third ports, the mode converter being coupled to the third port;

a mode coupler coupled to the mode converter; and

an orthogonal-polarization reflecting mirror coupled to the mode coupler.

31. A multiplexer, comprising:

a mode converter including an optical fiber with a longitudinal axis, a core and a cladding in a surrounding relationship to the core, the optical fiber having multiple spatial modes;

a first optical circulator with first, second and third ports, the mode converter being coupled to the third port and a first optical transmission line carrying optical signals λ

₁-λ

_n being coupled to the first port;

a first mode coupler coupled to the mode converter and positioned between the first optical circulator and the mode converter;

a first orthogonally-polarization reflecting mirror coupled to the first mode coupler;

a second optical circulator with at least a first, second and third ports, the mode converter being coupled to the first port and the third port being coupled to a second transmission line;

a second mode coupler positioned between the second optical circulator and the first mode coupler;

a second orthogonal-polarization reflecting mirror coupled to the second mode coupler;

wherein at least one signal of the optical signals λ

₁-λ

_n is dropped at the second port of the first optical circulator and the non-dropped optical signals λ

₁-λ

_n are transmitted from the second transmission line.

32. A multiplexer, comprising:

a first mode converter including an optical fiber with a longitudinal axis, a core and a cladding in a surrounding relationship to the core, the optical fiber having multiple spatial modes

a first optical circulator with first, second and third ports, the first mode converter being coupled to the third port and a first optical transmission line carrying optical signals λ

₁-λ

_n being coupled to the first port;

a first mode coupler coupled to the first mode converter and positioned between the first optical circulator and the first mode converter;

a first orthogonally-polarization reflecting mirror coupled to the first mode coupler;

a second optical circulator with at least a first, second and third ports, the first acousto-optic mode converter being coupled to the first port and the third port being coupled to a second transmission line;

a second mode coupler positioned between the second optical circulator and the first mode coupler;

a second orthogonal-polarization reflecting mirror coupled to the second mode coupler;

a second mode converter coupled to the optical fiber and positioned between the second mode coupler and the second optic circulator; and

wherein at least one signal of the optical signals λ

₁-λ

_n is dropped at the second port of the first optical circulator, and a signal λ

_n+1 is introduced at the second port of the second optical circulator, combined with the non-dropped optical signals λ

₁-λ

_n and are transmitted from the third port of the second optical circulator.

33. An add/drop acousto-optic filter, comprising:

a first acousto-optic mode converter including,

an optical fiber with a longitudinal axis,

an acoustic wave propagation member with a proximal end and a distal end, the distal end being coupled to the optical fiber, the acoustic wave propagation member propagating an acoustic wave from the proximal to the distal end, and

at least one acoustic wave generator coupled to the proximal end of the acoustic wave propagation member;

a first optical circulator with first, second and third ports, the first acousto-optic mode converter being coupled to the third port and a first optical transmission line carrying optical signals λ

₁-λ

_n being coupled to the first port;

a first mode coupler coupled to the first acousto-optic mode converter and positioned between the first optical circulator and the first acousto-optic mode converter;

a first orthogonally-polarization reflecting mirror coupled to the first mode coupler;

a second optical circulator with at least a first, second and third ports, the first acousto-optic mode converter being coupled to the first port and the third port being coupled to a second transmission line;

a second mode coupler positioned between the second optical circulator and the first mode coupler;

a second orthogonal-polarization reflecting mirror coupled to the second mode coupler;

a second acousto-optic mode converter coupled to and positioned between the second mode coupler and the second optic circulator;

the second acousto-optic mode converter including,

an acoustic wave propagation member with a proximal end and a distal end, the distal end being coupled to the optical fiber, the acoustic wave propagation member propagating an acoustic wave from the proximal to the distal end, and

at least one acoustic wave generator coupled to the proximal end of the acoustic wave propagation member;

a tunable notch filter positioned between the first and second acousto-optic mode converters; and

wherein at least one signal of the optical signals λ

₁-λ

_n is dropped at the second port of the first optical circulator, and a signal λ

_n+1 is introduced at the second port of the second optical circulator, combined with the non-dropped optical signals λ

₁-λ

_n and are transmitted from the third port of the second optical circulator.

34. An add/drop acousto-optic filter, comprising:

a first acousto-optic mode converter including,

an optical fiber with a longitudinal axis,

an acoustic wave propagation member with a proximal end and a distal end, the distal end being coupled to the optical fiber, the acoustic wave propagation member propagating an acoustic wave from the proximal to the distal end;

at least one acoustic wave generator coupled to the proximal end of the acoustic wave propagation member;

a first optical circulator with first, second and third ports, the first acousto-optic mode converter being coupled to the third port and a first optical transmission line carrying optical signals λ

₁-λ

_n being coupled to the first port;

a first mode coupler coupled to the first acousto-optic mode converter and positioned between the first optical circulator and the first acousto-optic mode converter;

a first orthogonally-polarization reflecting mirror coupled to the first mode coupler;

a second optical circulator with at least a first, second and third ports, the first acousto-optic mode converter being coupled to the first port and the third port being coupled to a second transmission line;

a second mode coupler positioned between the second optical circulator and the first mode coupler;

a second orthogonal-polarization reflecting mirror coupled to the second mode coupler;

a second acousto-optic mode converter coupled to and positioned between the second mode coupler and the second optic circulator;

the second acousto-optic mode converter including,

an acoustic wave propagation member with a proximal end and a distal end, the distal end being coupled to the optical fiber, the acoustic wave propagation member propagating an acoustic wave from the proximal to the distal end, and

at least one acoustic wave generator coupled to the proximal end of the acoustic wave propagation member;

a tunable notch filter positioned between the first and second acousto-optic mode converters; and

wherein at least one optical signals λ

_n+1 is added at the second port of the first optical circulator, and at least one signal λ

_n+2 is introduced at the second port of the second optical circulator, combined with the optical signals λ

₁-λ

_n and are transmitted from the third port of the second optical circulator.