Systems and methods for demodulation of free space optical signals without wavefront correction

Patent metadata

Field	Value
Publication number	US-9973281-B2
Application number	US-201715717175-A
Country	US
Kind code	B2
Filing date	Sep 27, 2017
Priority date	Sep 27, 2016
Publication date	May 15, 2018
Grant date	May 15, 2018

Abstract

Optical signal receivers and methods are provided that include an optical resonator that allows an optical signal to enter and optical signal energy to accumulate at regions inside the optical resonator. A portion of optical signal energy is emitted from among various regions of the optical resonator, such that a combination of the emitted optical signal energy is disturbed when a phase transition occurs in the received optical signal. A detector aligned with the output detects the combined emitted optical signal energy and is configured to detect the disturbance and determine a characteristic of the phase transition in the received optical signal based upon the disturbance.

First claim

What is claimed is:

1. An optical signal receiver comprising:
at least one optical resonator defining a plurality of regions, an aperture to allow optical signal energy to enter, and an output to allow a portion of optical signal energy to be emitted, the at least one optical resonator configured to receive an optical signal via the aperture, to accumulate resonant optical signal energy at least within each region, to cause the emitted optical signal energy associated with each region to approach a steady-state output value, and to disturb the emitted optical signal energy associated with each region upon a transition in the received optical signal, the at least one optical resonator having at least one dimension to cause phase alignment of the accumulated optical signal energy at one or more resonant wavelengths; and
a detector aligned with the output and configured to detect the disturbance to the emitted optical signal energy from one or more of the regions, and to determine a characteristic of the transition in the received optical signal based upon the disturbance.

2. The optical signal receiver of claim 1 wherein the at least one optical resonator includes a plurality of optical resonators, each of the plurality of optical resonators defining at least one of the plurality of regions.

3. The optical signal receiver of claim 1 further comprising a focusing optic aligned with the output and configured to focus the emitted optical signal energy associated with each region to provide a focused optical signal to the detector.

4. The optical signal receiver of claim 1 wherein each region of the at least one optical resonator is configured to produce a temporary change in intensity of the emitted optical signal energy in response to a phase transition in the received optical signal, and the detector is further configured to detect a combined temporary change in the intensity of a combined emitted optical signal energy from all of the plurality of regions, and to determine the phase transition in the received optical signal based upon the combined temporary change.

5. The optical signal receiver of claim 4 wherein each region of the at least one optical resonator is configured to produce a variation in intensity of the emitted optical signal energy in response to amplitude variations in the received optical signal, and the detector is further configured to detect a combined variation in intensity from the combined emitted optical signal energy from all of the plurality of regions, and to determine the amplitude variation in the received optical signal based upon the combined variation in intensity.

6. The optical signal receiver of claim 1 wherein the at least one optical resonator includes first and second reflective surfaces with reflective sides facing each other, the first reflective surface forming at least a portion of the aperture and being partially transmissive to optical signal energy arriving from outside the at least one optical resonator to allow optical signal energy into the at least one optical resonator, the second reflective surface forming at least a portion of the output and being substantially reflective but partially transmissive to optical signal energy inside the at least one optical resonator to allow the portion of the optical signal energy inside the at least one optical resonator to be emitted outside the at least one optical resonator.

7. The optical signal receiver of claim 1 further comprising an optical-electrical converter configured to convert the emitted optical signal energy into an electrical signal, the electrical signal having an amplitude indicative of an intensity of the emitted optical signal energy, and the detector configured to detect the disturbance to the emitted optical signal energy by processing the electrical signal.

8. A method of detecting information encoded in an optical signal, the method comprising:
receiving an optical signal at a plurality of regions of an aperture;
accumulating optical signal energy from the optical signal in associated regions of at least one optical resonator, to approach a steady state of accumulated optical signal energy in the associated regions;
outputting optical signal energy from the accumulated optical signal energy, the intensity of the output optical signal energy from each associated region proportional to the accumulated optical signal energy in each associated region;
detecting combined output optical signal energy, the combined output optical signal energy being a combination of the output optical signal energy from a plurality of the associated regions; and
determining a modulation characteristic of the received optical signal based on the detected combined output optical signal energy.

9. The method of claim 8 wherein determining a modulation characteristic of the received optical signal based on the detected combined output signal energy includes determining a phase variation in the received optical signal based on an intensity variation in the combined output optical signal energy.

10. The method of claim 8 further comprising reducing the accumulated optical signal energy in the associated regions of the optical resonator by destructive interference within the at least one optical resonator, in response to the modulation characteristic of the received optical signal.

11. The method of claim 10 wherein the modulation characteristic of the received optical signal is a phase transition associated with a phase modulation.

12. The method of claim 8 wherein accumulating the optical signal energy in associated regions of at least one optical resonator includes partially reflecting the optical signal energy between two semi-reflective surfaces.

13. The method of claim 8 further comprising converting the combined output optical signal energy into an electrical signal, the amplitude of the electrical signal being representative of the intensity of the combined output optical signal energy.

14. The method of claim 13 wherein converting the combined output optical signal energy into an electrical signal includes focusing the output optical signal energy from a plurality of the associated regions.

15. An optical receiver comprising:
at least one etalon configured to at least partially accumulate optical signal energy at a plurality of regions between two semi-reflective surfaces and having an aperture to allow optical signal energy to enter and an output to allow a portion of the accumulated optical signal energy to be emitted from the plurality of regions, the at least one etalon configured to cause the output optical signal energy from each of the plurality of regions to temporarily vary in intensity based upon a phase transition in the entering optical signal energy at the respective region;
an optical-electrical converter configured to receive the output optical signal energy from the plurality of regions and to convert the output optical signal energy into an electrical signal; and
a receiver configured to receive the electrical signal and to determine information about the phase transition based in part on the electrical signal.

16. The optical receiver of claim 15 wherein the at least one etalon includes a plurality of etalons, each of the plurality of etalons defining at least one of the plurality of regions.

17. The optical receiver of claim 15 further comprising an analog to digital converter configured to convert the electrical signal from an analog form to a digital form, the receiver configured to receive the digital form of the electrical signal.

18. The opt

Assignees

• Raytheon Co

Inventors

• Kowalevicz Andrew
• Graceffo Gary M
• Dolgin Benjamin P

Classifications

• H04B10/671 Primary

  for controlling the input optical signal · CPC title

• G02F2/00

  Demodulating light; Transferring the modulation of modulated light; Frequency-changing of light (G02F1/35 takes precedence) · CPC title

• G02B5/28

  Interference filters · CPC title

• G02B17/004

  Systems comprising a plurality of reflections between two or more surfaces, e.g. cells, resonators (multipass arrangements for optical cuvettes G01N21/031; laser resonators H01S3/05) · CPC title

• H04B10/1123 Primary

  Bidirectional transmission · CPC title