Tuning a narrow band filter for telecommunication applications with an acoustic optical tunable filter
An optical tunable filter that includes a thin-film filter for band-passing at least two bands of wavelengths. The tunable filter further includes a tunable band-passing device tunable over the at least two bands for tuning to a tunable pass-band spectrally overlapped with one of the at least two bands. The tunable band-passing device further includes an Acousto-optical cell tunable with acoustic wave signals. The thin-film filter cooperating with the tunable band-pass device for generating a tunable output waveform that has substantially a square waveform spectrally corresponding to the at least two bands. The thin-film filter further cooperates with the tunable band-pass device for generating a tunable output waveform having substantially a square waveform over a spectral range of a C-band, an L-band and an S-band. The tunable band-pass device band-passes a tunable substantially Sinc-function-like waveform and the thin film filter band-passing a substantially square waveform with a center attenuated dip for compensating the tunable substantially Sinc-function waveform.
1. A tunable filter comprising:
a thin-film filter for band-passing at least two bands of wavelengths; and a tunable band-passing device tunable over said at least two bands for tuning to a tunable pass-band spectrally overlapped with one of said at least two bands.
2. The tunable filter of claim 1 wherein:
said tunable band-passing device further comprising an Acousto-optical cell tunable with acoustic wave signals.
3. The tunable filter of claim 2 wherein:
said Acoustic-optic cell further comprising a TeO2 in shear mode with an acoustic wave traveling in a direction substantially aligned with an crystal axis.
4. The tunable filter of claim 2 wherein:
said Acoustic-optic cell further comprising a TeO2 in shear mode with an optical wave traveling in a direction substantially aligned with an crystal axis.
5. The tunable filter of claim 1 wherein:
said thin-film filter cooperating with said tunable band-pass device for generating a tunable output waveform having substantially a square waveform spectrally corresponding to said at least two bands.
6. The tunable filter of claim 1 wherein:
said thin-film filter cooperating with said tunable band-pass device for generating a tunable output waveform having substantially a square waveform over a spectral range of a C-band, an L-band and an S-band.
7. The tunable filter of claim 1 wherein:
said tunable band-pass device band-passing a tunable substantially Sine-function waveform and said thin film filter band-passing a substantially square waveform with a center attenuated dip for compensating said tunable substantially Sine-function waveform.
8. The tunable filter of claim 1 wherein:
said tunable band-passing device further comprising an Acousto-optical cell having a first and second Acousto-optical diffraction means having a set of narrow-band optical filtering Bragg grating.
9. The tunable filter of claim 8 wherein:
said first and second Acousto-optical diffraction means comprising a first Acousto-optical crystal and a second Acousto-optical crystal.
10. The tunable filter of claim 8 further comprising:
a first electrode connected to said first Acousto-optical diffraction means and a second electrode connected to said second Acousto-optical diffraction means.
11. The tunable filter of claim 10 wherein:
said first electrode is connected to an RF signal for tuning a central frequency of said narrow band Bragg grating.
12. The tunable filter of claim 10 wherein:
said second electrode is connected to a second electric source to provide a second order filtering for compensating a wavelength shift.
13. The tunable filter of claim 8 wherein:
said first and second Acousto-optical diffraction means having diffraction phase gratings for intra-cavity narrow-band wavelength filtering.
14. The tunable filter of claim 8 wherein:
said thin-film filter cooperating with said tunable band-pass device for generating a tunable output waveform having substantially a square waveform spectrally corresponding to said at least two bands of wavelengths.
15. The tunable filter of claim 8 wherein:
said thin-film filter cooperating with said tunable band-pass device for generating a tunable output waveform having substantially a square waveform over a spectral range of a C-band, an L-band and an S-band.
16. The tunable filter of claim 8 wherein:
said tunable band-pass device band-passing a tunable substantially Sine-function waveform and said thin film filter band-passing a substantially square waveform with a center attenuated dip for compensating said tunable substantially Sine-function waveform.
17. The tunable filter of claim 8 further comprising:
a first and a second collimating lens for collimating a first and a second output optical signals from said first and second diffraction means of said tunable band-pass device.
18. The tunable filter of claim 8 wherein:
said first and second Acousto-optical diffraction means are formed as a first column and a second column respectively in a single Acousto-optical crystal.
19. The tunable filter of claim 8 further comprising:
said first and second Acousto-optical diffraction means are formed as a first column and a second column respectively in a birefringent crystal having a predefined responsiveness to an radio-frequency (RF) driven signal.
20. The tunable filter of claim 8 wherein:
said first and a second Acousto-optical diffraction means having said narrow-band optical filtering Bragg grating further comprising a surface acoustic wave (SAW) grating.
21. The tunable filter of claim 1 further comprising:
a photo diode for receiving an optical signal from said tunable band-pass device for monitoring optical intensity.
22. The tunable filter of claim 1 wherein:
said thin-film filter is provided for band-passing bands of wavelengths substantially aligned with a Telecommunication ITU wavelength grid.
23. The tunable filter of claim 1 further comprising:
a polarizer for receiving an optical signal from said tunable band-pass device for reducing a residual polarization of said optical signal.
24. The tunable filter of claim 1 wherein:
said tunable band-pass device further includes a means for adjusting an optical intensity of said tunable pass-band.
25. The tunable filter of claim 1 wherein:
said tunable band-passing device further comprising an Acousto-optical cell having a single Acousto-optical diffraction column having a set of narrow-band optical filtering Bragg grating.
26. A tunable optical filter comprising:
a frequency-tuning device configured as an Acousto-optical cell for cooperating with a fixed wavelength band-pass filter for flexibly tuning a pass-band of optical signals for passing therethrough.
27. The tunable optical filter of claim 26 wherein:
said Acousto-optical cell further comprising a first and a second Acousto-optical crystal.
28. The tunable optical filter of claim 26 wherein:
said Acousto-optical cell further comprising a first and a second Acousto-optical diffraction means disposed in an Acousto-optical crystal.
29. The tunable optical filter of claim 26 wherein:
said Acousto-optical cell further comprising a first and a second Acousto-optical diffraction columns respectively disposed in an Acousto-optical crystal.
30. The tunable optical filter of claim 26 wherein:
said first and second Acousto-optical cells are formed as a first column and a second column respectively in a birefringent crystal having a predefined responsiveness to an radio-frequency (RF) driven signal.
31. The tunable optical filter of claim 26 wherein:
said first and a second Acousto-optical cells having said narrow-band optical filtering Bragg grating further comprising a surface acoustic wave (SAW) grating.
32. The tunable optical filter of claim 26 wherein:
said fixed wavelength band-pass filter comprising a thin-film filter.
33. The tunable optical filter of claim 26 wherein:
said fixed wavelength band-pass filter comprising a fixed wavelength band-pass filter for band-passing bands of wavelengths substantially aligned with a Telecommunication ITU wavelength grid.
34. The tunable optical filter of claim 26 wherein:
said frequency-tuning device configured as a non-collinear Acousto-optical cell having an acoustic wave propagates almost perpendicular to an optical transmission therethrough.
35. The tunable filter of claim 26 wherein:
said Acoustic-optic cell further comprising a TeO2 in shear mode with an acoustic wave traveling in a direction substantially aligned with an crystal axis.
36. The tunable filter of claim 26 wherein:
said Acoustic-optic cell further comprising a TeO2 in shear mode with an optical wave traveling in a direction substantially aligned with an crystal axis.
37. The tunable filter of claim 26 wherein:
said Acousto-optical cell having a single Acousto-optical diffraction column having a set of narrow-band optical filtering Bragg grating.
38. A tunable optical attenuator comprising:
a frequency-tuning device configured as an Acousto-optical cell for cooperating with a fixed wavelength band-pass filter for flexibly tuning an intensity of a pass-band of optical signals for attenuating a designated pass-band of optical signals passing therethrough.
39. The tunable optical attenuator of claim 38 wherein:
said Acousto-optical cell further comprising a first and a second Acousto-optical crystal.
40. The tunable optical attenuator of claim 38 wherein:
said Acousto-optical cell further comprising a first and a second Acousto-optical diffraction means disposed in an Acousto-optical crystal.
41. The tunable optical attenuator of claim 38 wherein:
said Acousto-optical cell further comprising a first and a second Acousto-optical diffraction columns respectively disposed in an Acousto-optical crystal.
42. The tunable optical attenuator of claim 38 wherein:
said first and second Acousto-optical cells are formed as a first column and a second column respectively in a birefringent crystal having a predefined responsiveness to an radio-frequency (RF) driven signal.
43. The tunable optical attenuator of claim 38 wherein:
said first and a second Acousto-optical cells having said narrow-band optical filtering Bragg grating further comprising a surface acoustic wave (SAW) grating.
44. The tunable optical attenuator of claim 38 wherein:
said fixed wavelength band-pass filter comprising a thin-film filter.
45. The tunable optical attenuator of claim 38 wherein:
said fixed wavelength band-pass filter comprising a fixed wavelength band-pass filter for band-passing bands of wavelengths substantially aligned with a Telecommunication ITU wavelength grid.
46. The tunable optical attenuator of claim 38 wherein:
said frequency-tuning device configured as a non-collinear Acousto-optical cell having an acoustic wave propagates almost perpendicular to an optical transmission therethrough.
47. The tunable optical attenuator of claim 38 wherein:
said frequency-tuning device further includes a means to adjust an optical intensity of said pass-band.
48. A method for configuring a tunable optical filter comprising:
employing an Acousto-optical cell for configuring a frequency-tuning device for cooperating with a fixed wavelength band-pass filter for flexibly tuning a pass-band of optical signals for passing therethrough.
49. The method of claim 48 wherein:
said step of employing said Acousto-optical cell further comprising a step of employing said Acousto-optical cell having a first and a second Acousto-optical crystal.
50. The method of claim 48 wherein:
said step of employing said Acousto-optical cell further comprising a step of employing said Acousto-optical cell having a first and a second Acousto-optical diffraction means disposed in an Acousto-optical crystal.
51. The method of claim 50 wherein:
said step of employing said first and a second Acousto-optical cells further comprising a step of employing said first and second Acousto-optical cells having said narrow-band optical filtering Bragg grating comprising a surface acoustic wave (SAW) grating.
52. The method of claim 48 wherein:
said step of employing said Acousto-optical cell further comprising a step of employing said Acousto-optical cell having a first and a second Acousto-optical diffraction columns respectively disposed in an Acousto-optical crystal.
53. The method of claim 48 wherein:
said step of employing said Acousto-optical cell further comprising a step of employing said Acousto-optical cell having a first column and a second column respectively in a birefringent crystal having a predefined responsiveness to an radio-frequency (RF) driven signal.
54. The method of claim 48 wherein:
said step of cooperating with said fixed wavelength band-pass filter comprising a step of cooperating with a thin-film band-pass filter.
55. The method of claim 48 wherein:
said step of cooperating with said fixed wavelength band-pass filter further comprising step of cooperating with a fixed wavelength band-pass filter for band-passing bands of wavelengths substantially aligned with a Telecommunication ITU wavelength grid.
56. The method of claim 48 wherein:
said step of employing said frequency-tuning device configured as a non-collinear Acousto-optical cell further comprising a step of propagating an acoustic wave along a direction almost perpendicular to an optical transmission therethrough.
57. A method of configuring a tunable optical attenuator comprising:
configuring an Acousto-optical cell as a frequency-tuning device for cooperating with a fixed wavelength configured band-pass filter for flexibly tuning an intensity of a pass-band of optical signals for attenuating a designated pass-band of optical signals passing therethrough.