Terrestrial optical communication network of integrated fiber and free-space links which requires no electro-optical conversion between links
View Patent ↗Optical signals are received from a free-space link by directing received light onto a plurality of microlenses and then directing light received through each of the microlenses into a respective single mode optical fiber (SMF). Light beams from the SMFs are combined into a single light beam in one SMF. The single light beam is amplified with a multi-wavelength fiber amplifier and attenuated with a variable optical attenuator. The power gain of the multi-wavelength fiber amplifier and the attenuation of the variable optical attenuator are controlled. The single light beam is directed into a fiber optic communication system that is optically coupled to the variable optical attenuator.
1. A method of receiving optical signals from a free-space link, comprising the steps of:
receiving light from the free-space link with one or more lenses;
directing light received through each of the one or more lenses into a respective fiber optic conductor;
combining light beams output from all of the respective fiber optic conductors into a single light beam in one fiber optic conductor;
amplifying the single light beam with a multi-wavelength fiber amplifier that is optically coupled to the one fiber optic conductor;
controlling a power gain of the multi-wavelength fiber amplifier; and
directing the single light beam into a fiber optic communication system without using electro-optical conversion.
2. A method in accordance with claim 1 , wherein the step of directing light received through each of the one or more lenses into a respective fiber optic conductor comprises the step of using each of the one or more lenses to focus incoming light to a focal point within an associated tube that supports its respective lens.
3. A method in accordance with claim 1 , wherein the step of controlling comprises the step of controlling the power gain of the multi-wavelength fiber amplifier in response to an optical signal received over the free-space link.
4. A method in accordance with claim 1 , wherein the multi-wavelength fiber amplifier comprises an erbium doped fiber amplifier (EDFA).
5. A method in accordance with claim 1 , wherein the light communicated in the fiber optic communication system comprises a fundamental wavelength falling in the 1550 nanometer (nm) band.
6. A method ire accordance with claim 5 , wherein the light received from the free-space link and the single light beam comprises a fundamental wavelength falling in the 1550 nanometer (nm) band.
7. An optical receiver for receiving optical signals from a free-space link, comprising:
one or more lenses for receiving light from the free-space link;
one or more fiber optic conductors configured to each receive light from a respective one of the lenses;
a beam combiner configured to combine light beams output from all of the fiber optic conductors into a single light beam in one fiber optic conductor;
a multi-wavelength fiber amplifier optically coupled to the one fiber optic conductor and configured to amplify the single light beam;
a controller configured to control a power gain of the multi-wavelength fiber amplifier; and
another fiber optic conductor optically coupled to the multi-wavelength fiber amplifier for optically coupling the single light beam into a fiber optic communication system without using electro-optical conversion.
8. An optical receiver in accordance with claim 7 , further comprising one or more tubes with each tube being used to support one of the lenses so that each lens focus incoming light to a focal point within its associated tube in order to direct light into its respective fiber optic conductor.
9. An optical receiver in accordance with claim 7 , wherein the controller is further configured to control the power gain of the multi-wavelength fiber amplifier in response to an optical signal received over the free-space link.
10. An optical receiver in accordance with claim 7 , wherein the multi-wavelength fiber amplifier comprises an erbium doped fiber amplifier (EDFA).
11. An optical receiver in accordance with claim 7 , wherein the light communicated in the fiber optic communication system comprises a fundamental wavelength falling in the 1550 nanometer (nm) band.
12. An optical receiver in accordance with claim 11 , wherein the light received from the free-space link and the single light beam comprises a fundamental wavelength falling in the 1550 nanometer (nm) band.
13. A method of receiving optical signals from a free-space link, comprising the steps of:
receiving light from the free-space link;
directing the received light onto a plurality of microlenses;
directing light received through each of the microlenses into a respective single mode optical fiber;
combining light beams output from all of the respective single mode optical fibers into a single light beam in one single mode optical fiber;
amplifying the single light beam with a multi-wavelength fiber amplifier that is optically coupled to the one single mode optical fiber;
attenuating the single light beam with a variable optical attenuator that is optically coupled to the multi-wavelength fiber amplifier;
controlling a power gain of the multi-wavelength fiber amplifier and an attenuation provided by the variable optical attenuator; and
directing the single light beam into a fiber optic communication system that is optically coupled to the variable optical attenuator.
14. A method in accordance with claim 13 , wherein the step of combining comprises the step of combining with a multi-stage combiner.
15. A method in accordance with claim 13 , wherein the light communicated in the fiber optic communication system comprises a fundamental wavelength falling in the 1550 nanometer (nm) band.
16. A method in accordance with claim 15 , wherein the light received from the free-space link and the single light beam comprise a fundamental wavelength falling in the 1550 nanometer (nm) band.
17. A method in accordance with claim 13 , wherein the step of receiving comprises the step of receiving light from the free-space link with a focusing device.
18. A method in accordance with claim 17 , wherein the focusing device comprises a telescope.
19. A method in accordance with claim 18 , wherein the telescope comprises a Schmidt-Cassegrain telescope.
20. A method in accordance with claim 13 , wherein the step of receiving comprises the step of receiving light from the free-space link with an infrared window.
21. A method in accordance with claim 20 , wherein the infrared window comprises an 850/1550 nanometer (nm) bandpass filter window.
22. An optical receiver for receiving optical signals from a free-space link, comprising:
a plurality of microlenses configured to receive light from the free-space link;
a plurality of single mode optical fibers configured to each receive light from a respective one of the microlenses;
a combiner stage configured to combine light beams output from the plurality of single mode optical fibers into a single light beam in one single mode optical fiber;
a multi-wavelength fiber amplifier optically coupled to the one single mode optical fiber and configured to amplify the single light beam;
a variable optical attenuator optically coupled to the multi-wavelength fiber amplifier and configured to attenuate the single light beam;
a controller configured to control a power gain of the multi-wavelength fiber amplifier and an attenuation provided by the variable optical attenuator; and
means for optically coupling the variable optical attenuator to an external single mode optical fiber.
23. An optical receiver in accordance with claim 22 , wherein the combiner stage comprises a multi-stage combiner.
24. An optical receiver in accordance with claim 22 , wherein the light communicated in the single mode optical fibers comprises a fundamental wavelength falling in the 1550 nanometer (nm) band.
25. An optical receiver in accordance with claim 24 , wherein the light received from the free-space link comprises a fundamental wavelength falling in the 1550 nanometer (nm) band.
26. An optical receiver in accordance with claim 22 , further comprising a focusing device configured to receive light from the free-space link and provide the received light to the plurality of microlenses.
27. An optical receiver in accordance with claim 26 , wherein the focusing device comprises a telescope.
28. An optical receiver in accordance with claim 27 , wherein the telescope comprises a Schmidt-Cassegrain telescope.
29. An optical receiver in accordance with claim 22 , further comprising an infrared window configured to receive light from the free-space link and provide the received light to the plurality of microlenses.
30. An optical receiver in accordance with claim 29 , wherein the infrared window comprises an 850/1550 nanometer (nm) bandpass filter window.