Terrestrial optical communication network of integrated fiber and free-space links which requires no electro-optical conversion between links

• US 6,868,237 B2
• Filed: 05/04/2001
• Issued: 03/15/2005
• Est. Priority Date: 04/24/1998
• Status: Expired due to Term

• Current Assignee: LightPointe Communications, Inc.
• Original Assignee: LightPointe Communications, Inc.
• Inventors: Clark, Gerald R., Willebrand, Heinz
• Primary Examiner(s): NEGASH, KINFE MICHAEL
• Application Number:
  US09/849,613
• Publication Number:
  US 20020012139A1
• Time in Patent Office: 1,411 Days
• Field of Search: 359/152, 359/134, 359/160, 359172-173, 359/341.3, 359/145, 359/118, 359/341.1, 398/92, 398/103, 398/96, 398/115, 398/116, 398/88, 398/118, 398/127, 398/130, 398/139, 398/144, 398/141, 398/157, 398/160, 398/200, 398/212, 398/214
• US Class Current: 398/214
• CPC Class Codes: H04B 10/1125 using a single common optical path
• CPC Class Codes: H04B 10/1149 Arrangements for indoor wireless networking of information
• CPC Class Codes: H04B 10/2912 characterised by the medium used for amplification or processing
• CPC Class Codes: H04B 10/40 Transceivers
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04Q 11/0062 Network aspects
• CPC Class Codes: H04Q 2011/0026 using free space propagation (e.g. lenses, mirrors)

Abstract

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.

Claims

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.