BALANCED BYPASS CIRCULATORS AND FOLDED UNIVERSALLY-BALANCED INTERFEROMETERS

• US 20080044184A1
• Filed: 08/16/2007
• Published: 02/21/2008
• Est. Priority Date: 08/16/2006
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Popovic, Milos
• Granted Patent: US 8,111,994 B2
• Time in Patent Office: Days
• US Class Current: 398/82
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02F 1/0147 based on thermo-optic effects G02F1/132 takes precedence
• CPC Class Codes: G02F 1/212 Mach-Zehnder type
• CPC Class Codes: G02F 2201/16 series; tandem
• CPC Class Codes: G02F 2203/02 reflective
• CPC Class Codes: G02F 2203/15 involving resonance effects, e.g. resonantly enhanced interaction
• CPC Class Codes: G02F 2203/585 Add/drop devices
• CPC Class Codes: H04J 14/0206 Express channels arrangements
• CPC Class Codes: H04J 14/0209 Multi-stage arrangements, e.g. by cascading multiplexers or demultiplexers
• CPC Class Codes: H04J 14/021 Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM]

Abstract

The invention generally relates, in one aspect, to an interferometer system. The interferometer system includes a splitter/combiner element (SCE), a first bi-directional optical path, and a second bi-directional optical path.

Claims

1. An interferometer system comprising:

a first splitter/combiner element (SCE) having an input port, an output port, a first bi-directional port, and a second bi-directional port, the first SCE configured to split an input signal received at the input port among the first and second bi-directional ports and to combine signals received at the first and second bi-directional ports into an output signal at the output port;

a first bi-directional optical path for communicating light between the first bi-directional port of the first SCE and an optical device; and

a second bi-directional optical path for communicating light between the second bi-directional port of the first SCE and the optical device,

wherein a substantial portion of light at at least one wavelength that exits the first SCE through the first bi-directional port re-enters the first SCE through the second bi-directional port.

2. The system of claim 1 further comprising the optical device.

3. The system of claim 2, wherein the optical device is a group-delay-matched circulator bypass (GMCB).

5. The system of claim 3, wherein the GMCB comprises a first and second embedded optical device (EOD).

6. The system of claim 5, wherein the GMCB comprises a first optical path through the first EOD and a second optical path through the second EOD.

10. The system of claim 6, wherein the second EOD introduces a phase shift to a signal that propagates through the second optical path that is different from a phase shift introduced by the first EOD to a signal that propagates through the first optical path.

11. The system of claim 3, wherein the GMCB comprises at least one optical circulator.

12. The system of claim 2, wherein the optical device introduces a phase delay to a first signal propagating through the optical device from the first bi-directional port of the first SCE to the second bi-directional port of the first SCE that differs by approximately (π

+2π

k) radians, k an integer, from the phase delay of a second signal propagating through the optical device from the second bi-directional port of the first SCE to the first bi-directional port of the first SCE.

13. The system of claim 2 further comprising a second SCE in communication with the optical device.

14. The system of claim 13, wherein the second SCE comprises an input port, an output port, a first bi-directional port, and a second bi-directional port, the second SCE configured to split an input signal received at the input port of the second SCE among the first and second bi-directional ports of the second SCE and to combine signals received at the first and second bi-directional ports of the second SCE into an output signal at the output port of the second SCE.

19. The system of claim 1, wherein a substantial portion of light at at least one wavelength that exits the first SCE through the second bi-directional port re-enters the first SCE through the first bi-directional port.

20. The system of claim 19, wherein the light that exits the first SCE through the first bi-directional port and re-enters the first SCE through the second bi-directional port experiences a first phase shift spectrum and the light that exits the first SCE through the second bi-directional port and re-enters the first SCE through the first bi-directional port experiences a second phase shift spectrum, the first phase shift spectrum and the second phase shift spectrum differing by approximately π

radians plus an integer multiple of 2π

radians over an operating wavelength range of the interferometer system.

4. (canceled)

7-9. -9. (canceled)

15-18. -18. (canceled)

21-22. -22. (canceled)

23. A circulator bypass for use in an interferometer system, the circulator bypass comprising:

a first bi-directional input/output port;

a second bi-directional input/output port;

a first optical circulator coupled to at least one of the first and second bi-directional input/output ports;

a first optical path extending from the first bi-directional input/output port to the second bi-directional input/output port, supporting substantial transmission efficiency of light at at least one wavelength; and

a second optical path extending from the second bi-directional input/output port to the first bi-directional input/output port, supporting substantial transmission efficiency of light at at least one wavelength,

wherein, the group delay in propagation of light through the first optical path is substantially equal to the group delay in propagation of light through the second optical path.

24. The circulator bypass of claim 23, wherein the first optical path permits a substantial transmission of light from the first bi-directional input/output port to the second bi-directional input/output port over an operating wavelength range of the circulator bypass.

25. The circulator bypass of claim 23, wherein the second optical path permits a substantial transmission of light from the second bi-directional input/output port to the first bi-directional input/output port over the operating wavelength range of the circulator bypass.

27. The circulator bypass of claim 23 further comprising at least one embedded optical device coupled to the first optical circulator.

33. The circulator bypass of claim 23 further comprising a second optical circulator coupled to a different one of the first and second bi-directional input/output ports than the first optical circulator.

26. (canceled)

28-32. -32. (canceled)

34-37. -37. (canceled)

38. A method for replacing an old photonic device in a live wavelength-division-multiplexed (WDM) optical transmission network, the method comprising:

transferring all wavelengths in a WDM signal that are passing substantially unaffected through the old photonic device to a bypass path;

detaching the old photonic device from the live WDM optical transmission network without shutoff of the WDM optical transmission network;

inserting a new photonic device in the place of the old photonic device in the live WDM optical transmission network; and

transferring to the new photonic device all the wavelengths in the WDM signal that were transferred to the bypass path.

39. The method of claim 38 further comprising ensuring that the group delay between the bypass path and a device path in which the new photonic device is placed is balanced prior to transferring to the new photonic device all the wavelengths in the WDM signal that were transferred to the bypass path.

40. The method of claim 39, wherein the ensuring comprises sensing and adjusting the group delay between the bypass path and the device path.

41. The method of claim 38 further comprising ensuring that there is a 180°

differential phase shift at all wavelengths that are to pass through the new photonic device unaffected prior to transferring to the new photonic device all the wavelengths in the WDM signal that were transferred to the bypass path.

42-43. -43. (canceled)

44. An interferometer system comprising:

a splitter/combiner element (SCE) having a first bi-directional port, a second bi-directional port, and a third bi-directional port, the SCE configured to split an input signal received at the first bi-directional port among the second and third bi-directional ports and to combine signals received at the second and third bi-directional ports into an output signal at the first bi-directional port;

a first optical path for bi-directionally communicating light between the second bi-directional port of the SCE and an optical device; and

a second optical path for bi-directionally communicating light between the third bi-directional port of the SCE and the optical device,

wherein a substantial portion of light at at least one wavelength that exits the SCE through the second bi-directional port re-enters the SCE through the second bi-directional port, a substantial portion of light at said at least one wavelength that exits the SCE through the third bi-directional port re-enters the SCE through the third bi-directional port, and the phase shift of a first signal accumulated by propagating in the first optical path from the SCE, through the optical device, and back to the SCE and the phase shift of a second signal accumulated by propagating in the second optical path from the SCE, through the optical device, and back to the SCE are substantially equal or differ by a multiple of 2π

radians at said at least one wavelength.

45. The system of claim 44 further comprising the optical device.

50. The system of claim 45, wherein the optical device comprises at least one reflector.

53. The system of claim 44 further comprising an optical circulator coupled to the first bi-directional port.

46-49. -49. (canceled)

51-52. -52. (canceled)