초록 ▼

A free-space adaptive optical laser communication system having signal transmission and reception channels at all terminals in the communication system, wherein wavefront sensing and wavefront correction mechanisms are employed along signal transmission and reception channels of all terminals in the

A free-space adaptive optical laser communication system having signal transmission and reception channels at all terminals in the communication system, wherein wavefront sensing and wavefront correction mechanisms are employed along signal transmission and reception channels of all terminals in the communication system (i.e. adaptive optics) to improve the condition of the laser beam at the receiver (i.e. reduce the size of the spot a the detector plane). Speckle-to-receiver-aperture tracking mechanisms are employed in the transmission channel of the communication system and laser beam speckle tracking mechanism in the reception channels thereof, so as to achieve a first level of optical signal intensity stabilization at signal detector of each receiving channel. Speckle-to-fiber/detector locking mechanisms are also employed in signal receiving channels of all terminals in the communication system so as to achieve a second level of optical signal intensity stabilization at signal detector of each receiving channel.

대표청구항 ▼

What is claimed is: 1. A free-space optical (FSO) laser communication system automatically stabilizing variations in the detected intensity of laser beam carrier signals, caused by atmospheric turbulence along signal reception channels supported within said FSO laser communication system, said FSO

What is claimed is: 1. A free-space optical (FSO) laser communication system automatically stabilizing variations in the detected intensity of laser beam carrier signals, caused by atmospheric turbulence along signal reception channels supported within said FSO laser communication system, said FSO laser communication system comprising: at least first and second communication terminals in optical communication by way of a broad-band FSO laser beam communication link supporting signal transmission and reception channels; wherein each said communication terminal has a transmitter module and a receiver module; and wherein each said receiver module includes a receiving aperture for receiving a FSO laser beam carrier signal transmitted from said transmitter module of another one of said communication terminals; a fast steering mirror (FSM) for steering said FSO laser beam carrier signal along an optical pathway having downstream direction; a beam splitter, disposed downstream from said FSM, for splitting said FSO laser beam carrier signal into a first signal component and a second signal component; a receiving optical fiber, disposed at the end of said optical pathway, for receiving the second component of said FSO laser beam carrier signal after transmission along said optical pathway; a single-cell signal detector in optical communication with said receiving optical fiber, for detecting the intensity of said second component of said FSO laser beam carrier signal and generating an electrical signal corresponding thereto; a multi-segment signal detector, disposed downstream from said beam splitter, for detecting the intensity of said first signal component of said FSO laser beam carrier signal, and generating electrical signals corresponding thereto; a processor for automatically analyzing signals generated from said multi-segment signal detector, controlling said FSM, and automatically tracking or following a maximum intensity laser beam speckle in said FSO laser beam carrier signal, and moving low intensity laser beam speckles appearing in said FSO laser beam carrier signal away from said receiving optical fiber, and thereby achieving a first level of optical signal intensity stabilization at said single-cell signal detector in said receiver module; a spatial modulator for spatially modulating said second component of said FSO laser beam carrier signal; said processor further analyzing electrical signals produced by said single-cell signal detector, controlling said spatial modulator, and spatially modulating said second component of said FSO laser beam carrier signal so as to lock a maximum intensity speckle appearing in the received second component of said FSO laser beam carrier signal, onto said receiving optical fiber, and thereby achieving a second level of optical signal intensity stabilization at said single-cell signal detector in said receiver module. 2. The FSO laser communication system of claim 1, wherein said signal transmission and reception channels are optically-separated. 3. The FSO laser communication system of claim 1, wherein said signal transmission and reception channels are optically-combined. 4. The FSO laser communication system of claim 1, wherein said receiving aperture comprises a telescopic receiving aperture. 5. The FSO laser communication system of claim 1, wherein said transmitter module and said receiver module are realized as separate modules. 6. The FSO laser communication system of claim 1, wherein said transmitter module and said receiver module are realized as a single transceiver module. 7. The FSO laser communication system of claim 1, wherein said spatial modulator is a spatial phase modulator. 8. The FSO laser communication system of claim 7, wherein said spatial phase modulator is realized as a spatial phase modulation panel having a plurality spatial phase modulation elements. 9. The FSO laser communication system of claim 8, wherein said spatial phase modulation panel comprises a deformable mirror. 10. The FSO laser communication system of claim 1, wherein said spatial modulator is a spatial intensity modulator. 11. The FSO laser communication system of claim 10, wherein said spatial intensity modulator is realized as a spatial intensity modulation panel having a plurality spatial intensity modulation elements. 12. The FSO laser communication system of claim 1, wherein said multi-segment detector is a quad-cell detector. 13. The FSO laser communication system of claim 8, wherein said processor generates spatial phase modulation (SPM) control signals for controlling said spatial phase modulation panel, so as to lock said maximum intensity speckle in the received laser beam carrier signal onto said receiving optical fiber, and achieve said second level of optical signal intensity stabilization at said single-cell signal detector in said receiver module. 14. The FSO laser communication system of claim 11, wherein said processor generates spatial intensity modulation (SIM) control signals for controlling said spatial intensity modulation panel, so as to lock said maximum intensity speckle in the received laser beam carrier signal onto said receiving optical fiber, and achieve said second level of optical signal intensity stabilization at said single-cell signal detector in said receiver module. 15. A method of automatically stabilizing variations in the detected intensity of free-space optical (FSO) laser beam carrier signals caused by atmospheric turbulence in a free-space optical (FSO) laser communication system having at least first and second communication terminals in optical communication by way of a broad-band FSO laser beam communication link supporting signal transmission and reception channels, wherein each said transmission and reception channel has a transmitter module and a receiver module, and wherein each said receiver module includes (i) a receiving aperture for receiving a FSO laser beam carrier signal transmitted from said transmitter module of another one of said communication terminals, along a optical pathway having downstream direction, (ii) a receiving optical fiber, disposed at the end of said optical pathway, for receiving said FSO laser beam carrier signal after transmission along said optical pathway, and (iii) a single-cell signal detector in optical communication with said receiving optical fiber, for detecting the intensity of said FSO laser beam carrier signal and generating an electrical signal corresponding thereto, said method comprising the steps of: (a) providing within each said receiver module, a fast steering mirror (FSM), disposed upstream from said receiving optical fibers, for steering said FSO laser beam carrier signal along an optical pathway having a downstream direction; (b) providing a beam splitter, disposed downstream from said FSM, and splitting said FSO laser beam carrier signal into a first signal component and a second signal component; (c) providing a multi-segment signal detector, disposed downstream from said beam splitter, and detecting the intensity of said first signal component of said FSO laser beam carrier signal, and generating electrical signals corresponding thereto; (d) processing signals generated from said multi-segment signal detector, controlling said FSM, and automatically tracking or following a maximum intensity laser beam speckle in said FSO laser beam carrier signal, and moving low intensity laser beam speckles appearing in said FSO laser beam carrier signal away from said receiving optical fiber, and thereby achieving a first level of optical signal intensity stabilization at said single-cell signal detector in said receiver module; (e) providing a spatial modulator, disposed downstream from said beam splitter, and spatially modulating said second component of said FSO laser beam carrier signal; and (f) further processing electrical signals produced by said single-cell signal detector, controlling said spatial modulator, and spatially modulating said second component of said FSO laser beam carrier signal so as to lock a maximum intensity speckle appearing in the received second component of said FSO laser beam carrier signal, onto said receiving optical fiber, and thereby achieving a second level of optical signal intensity stabilization at said single-cell signal detector in said receiver module. 16. The method of claim 15, wherein said signal transmission and reception channels are optically-separated. 17. The method of claim 15, wherein said signal transmission and reception channels are optically-combined. 18. The method of claim 15, wherein said receiving aperture comprises a telescopic receiving aperture. 19. The method of claim 15, wherein said transmitter module and said receiver module are realized as separate modules. 20. The method of claim 15, wherein said transmitter module and said receiver module are realized as a single transceiver module. 21. The method of claim 15, wherein in step (e), said spatial modulator is a spatial phase modulator. 22. The method of claim 21, wherein in step (e), said spatial phase modulator is realized as a spatial phase modulation panel having a plurality spatial phase modulation elements. 23. The method of claim 8, wherein in step (e), said spatial phase modulation panel comprises a deformable mirror. 24. The method of claim 1, wherein in step (e), said spatial modulator is a spatial intensity modulator. 25. The method of claim 24, wherein in step (e), said spatial intensity modulator is realized as a spatial intensity modulation panel having a plurality spatial intensity modulation elements. 26. The method of claim 15, wherein in step (c), said multi-segment detector is a quad-cell detector. 27. The method of claim 22, wherein in step (e), said processor generates spatial phase modulation (SPM) control signals for controlling said spatial phase modulation panel, so as to lock said maximum intensity speckle in the received laser beam carrier signal onto said receiving optical fiber, and achieve said second level of optical signal intensity stabilization at said single-cell signal detector in said receiver module. 28. The method of claim 25, wherein in step (e), said processor generates spatial intensity modulation (SIM) control signals for controlling said spatial intensity modulation panel, so as to lock said maximum intensity speckle in the received laser beam carrier signal onto said receiving optical fiber, and achieve said second level of optical signal intensity stabilization at said single-cell signal detector in said receiver module.