Near field combat identification
View Patent ↗Systems and methods are provided regarding an optical communication system for both short- and long-range applications employing specialized diffusive elements. An interrogator unit can utilize a diffusive element that diffuses a portion of the laser beam for short-range applications. Other portions of the beam can have low divergence to enable long-range functionality as well. A response unit can utilize a diffusive retroreflector to help ensure sensors coupled to the interrogator unit detect a reflected beam. The interrogator unit can employ a plurality of sensors for sensing one or more response signals at a plurality of angles.
1. A method of free-space optical communication using laser light, the method comprising:
generating a beam of light with a laser at a first location;
modulating the beam of light with a first data signal to provide an optical transmission signal;
diffusing a first portion of the optical transmission signal with an optical element to cause an increase in beam divergence of the first portion of the optical transmission signal;
receiving at least a portion of the optical transmission signal at a second location;
reflecting the optical transmission signal to provide a reflected optical transmission signal;
modulating the reflected optical transmission signal;
diffusing at least a portion of the reflected optical transmission signal to cause an increase in beam divergence of the at least the portion of the reflected optical transmission signal; and
providing a plurality of sensors configured to detect the reflected optical transmission signal from one or more of a plurality of angles.
2. The method of free-space optical communication using the laser light recited in claim 1 , further comprising collimating a second portion of the optical transmission signal with the optical element.
3. The method of free-space optical communication using the laser light recited in claim 1 , wherein the beam divergence of the first portion of the optical transmission signal, after being diffused with the optical element, is at least 40 milliradians (mrad).
4. The method of free-space optical communication using the laser light recited in claim 1 , wherein the beam divergence of the at least the portion of the reflected optical transmission signal, after being diffused, is at least 1 mrad.
5. The method of free-space optical communication using the laser light recited in claim 1 , wherein the first portion of the optical transmission signal comprises 15% or less of the total power of the optical transmission signal.
6. The method of free-space optical communication using the laser light recited in claim 1 , wherein the reflecting the optical transmission signal includes using a plurality of retroreflective features, each of the retroreflective features having a set of three reflective surfaces that are approximately orthogonal to each other.
7. The method of free-space optical communication using the laser light recited in claim 1 , further comprising:
determining, at the first location, that a signal received from a sensor of the plurality of sensors representing the reflected optical transmission signal is below a threshold level, and
increasing power of the beam of light.
8. The method of free-space optical communication using the laser light recited in claim 1 , wherein the plurality of sensors comprise avalanche photo diodes.
9. A free-space optical interrogator comprising:
a laser configured to generate a beam of light;
a modulation component coupled with the laser and configured to modulate the beam of light with a first data signal to provide an optical transmission signal;
an optical element disposed in a path of the optical transmission signal, wherein:
a first portion of the optical element is configured to diffuse a first portion of the optical transmission signal; and
wherein a second portion of the optical element is configured to collimate a second portion of the optical transmission signal;
a plurality of sensors configured to receive a reflected optical transmission signal from one or more of a plurality of angles; and
a demodulation component coupled with the one or more sensors and configured to determine second data signal from the reflected optical transmission signal, wherein the second data signal is different from the first data signal.
10. The free-space optical interrogator recited in claim 9 , wherein the first portion of the optical element is configured to cause beam divergence of the first portion of the optical transmission signal of at least 40 milliradians (mrad).
11. The free-space optical interrogator recited in claim 9 , wherein the optical element is configured to diffuse 15% or toss of the total power of the optical transmission signal.
12. The free-space optical interrogator recited in claim 9 , further comprising a feedback component communicatively coupled with the sensors and configured to increase power of the beam of light if a detection signal representing the reflected optical transmission signal is below a threshold level.