Optical spectrum analyzer
View Patent ↗An optical spectrum analyzer (OSA) 10 sequentially or selectively samples (or filters) a spectral band(s) 11 of light from a broadband optical input signal 12 and measures predetermined optical parameters of the optical signal (e.g., spectral profile) of the input light 12 . The OSA 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 or spreads spatially the collimated input light, and reflects the dispersed 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 light back through the collimating lens 18 . The lens 18 focuses spectral bands of light (λ 1 –λ N ) at different focal points in space. One of the spectral bands 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 spectral band 11 to the receive pigtail 28 . A position sensor 42 detects the displacement of the diffraction grating 24 or mirror.
1. An optical spectrum analyzer for determining a parameter of an optical input signal, the optical spectrum analyzer comprising:
a collimator to collimate the input signal;
a light dispersion element that diffracts the collimated light into spectrally spaced optical wavelengths;
a reflector that reflects the spectrally-spaced optical wavelengths back to the light dispersion element;
a first mirror disposed adjacent to the light dispersion element wherein the first mirror receives light from the reflector to provide an optical reference signal indicative of a first relative position of the reflector; and
a pivoting mechanism that rotates the reflector to spectrally move the spectrally-spaced optical wavelengths to select an optical wavelength band.
2. The optical spectrum analyzer of claim 1 , further includes a first optical waveguide projects the optical signal and a second optical waveguide for receiving at least one of the spectrally-spaced optical wavelength bands.
3. The optical spectrum analyzer of claim 1 , wherein a first optical waveguide projects the optical signal and receives at least one of the selected optical wavelength bands.
4. The optical spectrum analyzer of claim 1 , further includes an optical detector that senses a parameter of the at least one selected optical wavelength band and provides a sensed signal indicative of the parameter of the at least one selected optical wavelength band.
5. The optical spectrum analyzer of claim 1 , further includes a position sensor that provides a position signal indicative of the displacement of the reflector.
6. The optical spectrum analyzer of claim 1 , wherein the pivoting mechanism further includes an actuator for moving the reflector about a pivot point.
7. The optical spectrum analyzer of claim 1 , wherein the reflector is at least one of a flat mirror, a folded mirror, a roof prism and a reflecting dihedron.
8. The optical spectrum analyzer of claim 1 , wherein the light dispersion element is a diffraction grating.
9. The optical spectrum analyzer of claim 1 , wherein the collimator includes at least one of an aspherical lens, an achromatic lens, a doublet or a laser diode doublet.
10. The optical spectrum analyzer of claim 2 , further comprising a pair of optical detectors that respectively detect the output of the first and second optical waveguides.
11. The optical spectrum analyzer of claim 1 , further comprising an optical source to provide light for projecting onto and reflecting off of the first mirror.
12. The optical spectrum analyzer of claim 1 , 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.
13. The optical spectrum analyzer of claim 6 , wherein the pivoting mechanism is a resonant actuator.
14. The optical spectrum analyzer of claim 13 , wherein the resonant actuator is a magnetic pulse drive.
15. The optical spectrum analyzer of claim 1 , wherein the light reflecting off the first mirror propagates substantially along the same optical path as the optical input signal.
16. The optical spectrum analyzer of claim 1 , wherein the light reflecting off the first mirror is a portion of the optical input signal.
17. The optical spectrum analyzer of claim 1 , wherein the light reflecting off the first mirror is provided by a separate light source.
18. An optical spectrum analyzer for determining a parameter of an optical input signal, the optical spectrum analyzer comprising:
a collimator to collimate the input signal;
a light dispersion element that diffracts the collimated light into spectrally spaced optical wavelengths;
a reflector that reflects the spectrally-spaced optical wavelengths back to the light dispersion element;
a first mirror disposed adjacent to at least one of the reflector and light dispersion element that provides an optical reference signal indicative of a first relative position of the reflector;
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; and
a pivoting mechanism that rotates the reflector to spectrally move the spectrally-spaced optical wavelengths to select an optical wavelength band.
19. An optical spectrum analyzer for determining a parameter of an optical input signal, the optical spectrum analyzer comprising:
a collimator to collimate the input signal;
a light dispersion element that diffracts the collimated light into spectrally spaced optical wavelengths;
a reflector that reflects the spectrally-spaced optical wavelengths back to the light dispersion element;
a first mirror disposed adjacent to the reflector that provides an optical reference signal indicative of a first relative position of the reflector;
a cylindrical lens disposed between the light dispersion element and the reflector; and
a pivoting mechanism that rotates the reflector to spectrally move the spectrally-spaced optical wavelengths to select an optical wavelength band.
20. An optical spectrum analyzer for determining a parameter of an optical input signal, the optical spectrum analyzer comprising:
a collimator to collimate the input signal;
a light dispersion element that diffracts the collimated light into spectrally spaced optical wavelengths;
a reflector that reflects the spectrally-spaced optical wavelengths back to the light dispersion element, wherein the light dispersion element diffracts the reflected optical wavelengths back to the collimator; and
a resonant actuator that rotates the reflector to spectrally move the spectrally-spaced optical wavelengths to select an optical wavelength band.
21. The optical spectrum analyzer of claim 20 , further includes a first optical waveguide projects the optical signal and a second optical waveguide for receiving at least one of the spectrally-spaced optical channels.
22. The optical spectrum analyzer of claim 20 , wherein a first optical waveguide projects the optical signal and receives at least one of the selected optical channels.
23. The optical spectrum analyzer of claim 20 , 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 spectrum analyzer of claim 20 , further includes a position sensor that provides a position signal indicative of the displacement of the reflector.
25. The optical spectrum analyzer of claim 22 , 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.
26. The optical spectrum analyzer of claim 20 , wherein the resonant actuator moves the reflector about a pivot point.
27. The optical spectrum analyzer of claim 20 , wherein the reflector is at least one of a flat mirror, a folded mirror, a roof prism and a reflecting dihedron.
28. The optical spectrum analyzer of claim 20 , wherein the light dispersion element is a diffraction grating.
29. The optical spectrum analyzer of claim 20 , wherein the collimator includes at least one of an aspherical lens, an achromatic lens, a doublet or a laser diode doublet.
30. The optical spectrum analyzer of claim 21 , further comprising a pair of optical detectors that respectively detect the output of the first and second optical waveguides.
31. The optical spectrum analyzer of claim 22 , further comprising an optical switch to selectively provide one of a plurality of optical input signals to the first optical waveguide.
32. The optical spectrum analyzer of claim 20 , further including a coupling device to redirect the output signal back to the collimator to again diffract off the light dispersion element onto the reflector and reflected back to the dispersion element and collimator to provide a quadruple pass optical spectrum analyzer.
33. The optical spectrum analyzer of claim 20 , wherein the resonant actuator is a magnetic pulse drive.
34. An optical spectrum analyzer for determining a parameter of an optical input signal, the optical spectrum analyzer comprising:
a collimator to collimate the input signal;
a light dispersion element that diffracts the collimated light into spectrally spaced optical wavelengths;
a reflector that reflects the spectrally-spaced optical wavelengths back to the light dispersion element, wherein the light dispersion element diffracts the reflected optical wavelengths back to the collimator; and
a cylindrical lens disposed between the light dispersion element and the reflector; and
a pivoting mechanism that rotates the reflector to spectrally move the spectrally-spaced optical wavelengths to select an optical wavelength band.