ASE swept source with self-tracking filter for OCT medical imaging
View Patent ↗An integrated swept wavelength tunable optical source uses a narrowband filtered broadband signal with an optical amplifier and self-tracking filter. This source comprises a micro optical bench, a source for generating broadband light, a tunable Fabry Perot filter, installed on the bench, for spectrally filtering the broadband light from the broadband source to generate a narrowband tunable signal, an amplifier, installed on the bench, for amplifying the tunable signal. The self-tracking arrangement is used where a single tunable filter both generates the narrowband signal and spectrally filters the amplified signal. In some examples, two-stage amplification is provided. The use of a single bench implementation yields a low cost high performance system. For example, polarization control between components is no longer necessary.
1. An optical coherence analysis system, comprising:
a swept source including a tunable filter for spectrally filtering light from a broadband source, which generates a broadband optical signal, to generate a tunable optical signal that is spectrally tuned over a scanband and an optical amplifier for amplifying the tunable optical signal with the amplified tunable optical signal being returned to be again filtered by the tunable filter while preventing lasing and formation of a resonator; and
an interferometer for dividing the amplified tunable optical signal between a reference arm and a sample arm and generating an interference signal by combining the optical signal from the reference arm and the sample arm; and
a detector system for detecting the interference signal.
2. A system as claimed in claim 1 , wherein the broadband source generates light over the scanband.
3. A system as claimed in claim 1 , wherein the broadband source comprises an amplified spontaneous emission source that generates light over the scanband.
4. A system as claimed in claim 1 , wherein the tunable filter is a Fabry Perot tunable filter.
5. A system as claimed in claim 1 , wherein the tunable filter is a micro electro mechanical system Fabry Perot tunable filter.
6. A system as claimed in claim 1 , wherein in a passband of the tunable optical filter is less than 20 GigaHertz (FWHM).
7. A system as claimed in claim 1 , wherein in a passband of the tunable optical filter is less than 5 GigaHertz (FWHM).
8. A system as claimed in claim 1 , further comprising a tuning controller that drives the tunable filter to tune over the scanband at a speeds greater than 10 kiloHertz.
9. A system as claimed in claim 1 , further comprising a tuning controller that drives the tunable filter to tune over the scanband at speeds greater than 100 kiloHertz.
10. A system as claimed in claim 1 , wherein the optical amplifier comprises a semiconductor optical amplifier.
11. A system as claimed in claim 1 , further comprising a reflector for reflecting the tunable optical signal to pass through the optical amplifier a second time and back to the tunable filter.
12. A system as claimed in claim 1 , further comprising a loop including the optical amplifier for directing the tunable optical signal back to the tunable filter.
13. A system as claimed in claim 1 , further comprising a polarization rotation system for rotating a polarization of the tunable optical signal between being filtered by the tunable filter.
14. A system as claimed in claim 13 , wherein the polarization rotation system includes a non-reciprocal polarization rotation element.
15. A system as claimed in claim 13 , wherein the polarization rotation system includes a halfwave plate.
16. A system as claimed in claim 1 , wherein the filtering by the tunable filter of the tunable optical signal is co-directional with the filtering of the amplified tunable optical signal by the tunable filter.
17. A system as claimed in claim 1 , wherein the filtering by the tunable filter of the tunable optical signal is contra-directional with the filtering of the amplified tunable optical signal by the tunable filter.
18. A method for generating a tunable optical signal, comprising:
spectrally filtering a broadband optical signal of a broadband source to generate a tunable optical signal with a tunable filter that is spectrally tuned over a scanband;
amplifying the tunable optical signal to generate an amplified tunable optical signal;
spectrally filtering the amplified tunable optical signal again with the same tunable filter while preventing lasing and formation of a resonator;
sending the filtered amplified tunable optical signal to an interferometer, which generates an interference signal; and
detecting the interference signal.
19. A method as claimed in claim 18 , further comprising generating the light with the broadband source that generates light over the scanband.
20. A method as claimed in claim 18 , wherein the tunable filter is a Fabry Perot tunable filter.
21. A method as claimed in claim 18 , further comprising tuning the tunable filter over the scanband at a speeds greater than 10 kiloHertz.
22. A method as claimed in claim 18 , further comprising tuning the tunable filter over the scanband at a speeds greater than 100 kiloHertz.
23. A method as claimed in claim 18 , further comprising directing the tunable optical signal back to the tunable filter using a loop.
24. A method as claimed in claim 18 , further comprising directing the tunable optical signal back to the tunable filter using a reflector.