Optical channel monitor

• US 20030007148A1
• Filed: 05/31/2002
• Published: 01/09/2003
• Est. Priority Date: 06/01/2001
• Status: Active Grant

• Current Assignee: II-VI Delaware, Inc. (Coherent Corp.)
• Original Assignee: Cidra Corporate Services, Inc.
• Inventors: Fournier, David, Moon, John, Jones, Ralph, Winston, Charles, Dunphy, James, Pinto, Joseph, Brucato, Robert, Sirkis, James, Chestnut, Christopher
• Granted Patent: US 7,463,828 B2
• Time in Patent Office: Days
• US Class Current: 356/328
• CPC Class Codes: G01J 2003/064 Use of other elements for scan, e.g. mirror, fixed grating
• CPC Class Codes: G01J 2003/1819 Double pass monochromator
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0202 Mechanical elements; Supports for optical elements
• CPC Class Codes: G01J 3/0208 using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• CPC Class Codes: G01J 3/021 using plane or convex mirrors, parallel phase plates, or particular reflectors
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/0256 Compact construction
• CPC Class Codes: G01J 3/0291 Housings; Spectrometer accessories; Spatial arrangement of elements, e.g. folded path arrangements
• CPC Class Codes: G01J 3/06 Scanning arrangements arrangements for order-selection
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01J 3/32 Investigating bands of a spectrum in sequence by a single detector
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• 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 6/2793 Controlling polarisation dependent loss, e.g. polarisation insensitivity, reducing the change in polarisation degree of the output light even if the input polarisation state fluctuates
• 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 6/29314 by moving or modifying the diffractive element, e.g. deforming
• CPC Class Codes: G02B 6/29385 Channel monitoring, e.g. by tapping channel monitoring in optical transmission systems H04B10/07
• CPC Class Codes: G02B 6/29398 Temperature insensitivity
• CPC Class Codes: G02B 6/3512 : the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/359 : of the position of the moving element itself during switching, i.e. without monitoring the switched beams
• CPC Class Codes: G02B 6/4215 : the intermediate optical elements being wavelength selective optical elements, e.g. variable wavelength optical modules or wavelength lockers G02B6/4246 takes precedence
• CPC Class Codes: G02B 6/4246 : Bidirectionally operating package structures
• CPC Class Codes: H04B 10/077 : using a supervisory or additional signal
• CPC Class Codes: H04B 10/07955 : Monitoring or measuring power
• CPC Class Codes: H04Q 2011/0026 : using free space propagation (e.g. lenses, mirrors)
• CPC Class Codes: H04Q 2011/0049 : Crosstalk reduction; Noise; Power budget
• CPC Class Codes: H04Q 2011/0083 : Testing; Monitoring

Abstract

An optical channel monitor is provided that sequentially or selectively filters an optical channel(s) 11 of light from a (WDM) optical input signal 12 and senses predetermined parameters of the each filtered optical signal (e.g., channel power, channel presence, signal-noise-ratio). The OCM 10 is a free-space optical device that includes a collimator assembly 15, a diffraction grating 20 and a mirror 22. A launch pigtail emits into free space the input signal through the collimator assembly 15 and onto the diffraction grating 20, which separates spatially each of the optical channels 11 of the collimated light, and reflects the separated channels of light onto the mirror 22. A λ/4 plate 26 is disposed between the mirror 22 and the diffraction grating 20. The mirror reflects the separated light back through the λ/4 plate 26 to the diffraction grating 20, which reflects the channels of light back through the collimating lens 18. The lens 18 focuses each separated channel of light (λ₁-λ_N) at a different focal point in space. One of the optical channels 11 is focused onto a receive pigtail 28, which then propagates to a photodetector 30. A pivoting mechanism 34 pivots the diffraction grating 20 or mirror 22 about a pivot point 36 to sequentially or selectively focus each optical channel 11 to the receive pigtail 28. A position sensor 42 detects the displacement of the diffraction grating 24 or mirror.

Claims

1. An optical channel monitor of an optical input signal that includes a plurality of optical channels, the optical channel monitor comprising:

a first optical waveguide for projecting the optical input signal;

a collimator to collimate the input signal projecting from the optical lens;

a light dispersion element that diffracts the collimated light into spectrally spaced optical channels;

a reflector that reflects the spectrally-spaced optical channels back to the light dispersion element;

a first mirror disposed adjacent to the reflector that provides an optical signal indicative of the first relative position of the reflector; and

a pivoting mechanism that rotates at least one of the light dispersion element and the reflector to spectrally move the spectrally-spaced optical channels to select an optical channel.

2. The optical channel monitor of claim 1, further comprises a λ

/4 plate disposed optically between the reflector and the light dispersion element.

3. The optical channel monitor of claim 1, further includes a second optical waveguide for receiving at least one of the spectrally-spaced optical channels.

4. The optical channel monitor of claim 1, wherein the first optical waveguide projects the optical signal and receives at least one of the selected optical channels.

5. The optical channel monitor of claim 1, further includes an optical detector that senses a parameter of the at least one selected optical channel and provides a sensed signal indicative of the parameter of the at least one selected optical channel.

6. The optical channel monitor of claim 1, further includes a position sensor that provides a position signal indicative of the displacement of the reflector.

7. The optical channel monitor of claim 6, wherein the position sensor includes a pair of capacitive plates to provide a signal indicative of the spacing between the plates.

8. The optical channel monitor of claim 1, further includes a second mirror disposed adjacent to the at least one of the reflector and light dispersion element to provide a second relative position of the reflector.

9. The optical channel monitor of claim 1, wherein the pivoting mechanism further includes an actuator for moving the at least on of the reflector and the light dispersion element about a pivot point.

10. The optical channel monitor of claim 9, wherein the actuator includes at least one of a voice coil, electro-ceramics, a motor and cam configuration, a motor and slide configuration, an arc motor, a linear motor, a magnetic pulse drive and a stepper motor.

11. The optical channel monitor of claim 1, wherein the reflector is at least one of a flat mirror, a folded mirror, a roof prism and a reflecting dihedron.

12. The optical channel monitor of claim 1, further includes a cylindrical lens disposed between the light dispersion element and the reflector.

13. The optical channel monitor of claim 1, further includes a photodetector and a device having a slit wherein the slit is optically disposed between the photodetector and the light dispersion element to filter the spectrally-spaced optical channels.

14. The optical channel monitor of claim 1, further comprises a λ

/4 plate disposed optically between the reflector and the light dispersion element wherein the fast axis is angularly disposed at 45 degrees to the direction of lines of the light dispersion element.

15. The optical channel monitor of claim 1, wherein the light dispersion element is a diffraction grating.

16. The optical channel monitor of claim 1, wherein the collimator includes at least one of an aspherical lens, an achromatic lens, a doublet or a laser diode doublet.

17. The optical channel monitor of claim 3, further comprising a pair of optical detectors that respectively detect the output of the first and second optical waveguides.

18. The optical channel monitor of claim 1, further comprising an optical source to provide light for projecting onto and reflecting off of the first mirror.

20. The optical channel monitor of claim 19, further comprises a λ

/4 plate disposed optically between the reflector and the light dispersion element.

21. The optical channel monitor of claim 19, further includes a second optical waveguide for receiving at least one of the spectrally-spaced optical channels.

22. The optical channel monitor of claim 19, wherein the first optical waveguide projects the optical signal and receives at least one of the selected optical channels.

23. The optical channel monitor of claim 19, further includes an optical detector that senses a parameter of the at least one selected optical channel and provides a sensed signal indicative of the parameter of the at least one selected optical channel.

24. The optical channel monitor of claim 19, further includes a position sensor that provides a position signal indicative of the displacement of the reflector.

25. The optical channel monitor of claim 19, further includes position sensor comprising a pair of capacitive plates to provide a signal indicative of the spacing between the plates.

26. The optical channel monitor of claim 19, further includes a second mirror disposed adjacent to the reflector to provide a second relative position of the reflector.

27. The optical channel monitor of claim 19, wherein the pivoting mechanism further includes an actuator for moving the reflector about a pivot point.

28. The optical channel monitor of claim 27, wherein the actuator includes at least one of a voice coil, electro-ceramics, a motor and cam configuration, a motor and slide configuration, an arc motor, a linear motor, a magnetic pulse drive and a stepper motor.

29. The optical channel monitor of claim 19, wherein the reflector is at least one of a flat mirror, a folded mirror, a roof prism and a reflecting dihedron.

30. The optical channel monitor of claim 19, further includes a cylindrical lens disposed between the light dispersion element and the reflector.

31. The optical channel monitor of claim 19, further includes a photodetector and a device having a slit wherein the slit is optically disposed between the photodetector and the light dispersion element to filter the spectrally-spaced optical channels.

32. The optical channel monitor of claim 19, further comprises a λ

/4 plate disposed optically between the reflector and the light dispersion element wherein the fast axis is angularly disposed at 45 degrees to the direction of lines of the light dispersion element.

33. The optical channel monitor of claim 19, wherein the light dispersion element is a diffraction grating.

34. The optical channel monitor of claim 19, wherein the collimator includes at least one of an aspherical lens, an achromatic lens, a doublet or a laser diode doublet.

35. The optical channel monitor of claim 21, further comprising a pair of optical detectors that respectively detect the output of the first and second optical waveguides.

36. The optical channel monitor of claim 19, further comprising an optical source to provide light for projecting onto and reflecting off of the first mirror.

37. The optical channel monitor of claim 19, further comprising an optical switch to selectively provide one of a plurality of optical input signals to the first optical waveguide.

39. The optical channel monitor of claim 38, further comprising at least a second optical waveguide for projecting a second input signal to the collimator to select an optical channel of the second input signal.

40. The optical channel monitor of claim 38, further includes a second optical waveguide for receiving at least one of the spectrally-spaced optical channels.

41. The optical channel monitor of claim 38, wherein the first optical waveguide projects the optical signal and receives at least one of the selected optical channels.

42. The optical channel monitor of claim 38, further includes an optical detector that senses a parameter of the at least one selected optical channel and provides a sensed signal indicative of the parameter of the at least one selected optical channel.

43. The optical channel monitor of claim 38, further includes a second mirror disposed adjacent to the reflector to provide a second relative position of the reflector.

44. The optical channel monitor of claim 38, wherein the reflector is at least one of a flat mirror, a folded mirror, a roof prism and a reflecting dihedron.

45. The optical channel monitor of claim 40, further comprising a pair of optical detectors that respectively detect the output of the first and second optical waveguides.

46. The optical channel monitor of claim 38, wherein the pivoting mechanism comprising a balanced resonant actuator.

47. The optical channel monitor of claim 46, wherein the actuator includes a permanent magnet motor and a drive coil for pivoting the pivot mechanism about a pivot point.

48. The optical channel monitor of claim 47, wherein the drive coil provides a signal representative of the back EMF of the drive coil, which is representative of the velocity of the pivot mechanism.

19. An optical channel monitor of an optical input signal that includes a plurality of optical channels, the optical channel monitor comprising:

a first optical waveguide for projecting the an optical input signal;

a collimator to collimate the input signal projecting from the optical lens;

a light dispersion element that diffracts the collimated light into spectrally spaced optical channels;

a reflector that reflects the spectrally spaced optical channels back to the light dispersion element; and

a pivoting mechanism that rotates the reflector to spectrally move the spectrally spaced optical channels to select an optical channel.

38. An optical channel monitor of an optical input signal that includes a plurality of optical channels, the optical channel monitor comprising:

a first optical waveguide for projecting the optical input signal;

a collimator to collimate the input signal projecting from the optical lens;

a light dispersion element that diffracts the collimated light into spectrally spaced optical channels;

a reflector that reflects the spectrally-spaced optical channels back to the light dispersion element; and

a pivoting mechanism that rotates at least one of the light dispersion element and the reflector to spectrally move the spectrally-spaced optical channels to select an optical channel.