High-bandwidth, free space optical communications links for drone networks
A free space optical communication (FSOC) system suitable for drones with appropriate size, weight, acquisition performance, and range characteristics for a broad variety of drone applications including both civilian and military applications. Depending on requirements, the system may be configured to support point-to-point communications between ground stations and individual drones, mesh networking among multiple drones in a swarm configuration, and hybrid FSOC and RF capabilities providing automatic failover to maintain connectivity when optical line-of-sight is temporarily blocked. The system delivers the operational resilience necessary for tactical operations in contested environments while maintaining the bandwidth, security, and jam-resistance advantages inherent to free space optical communications.
1 . A free space optical communication system for unmanned aerial vehicles, the system comprising:
a base station optical communications device configured to transmit and receive optical signals, the base station comprising:
a laser light source configured to produce an outgoing laser emission;
a first pointing, acquisition, and tracking (PAT) module operating on a first computing device, the first PAT module configured to acquire and track an unmanned aerial vehicle; and
a first solid-state beam steering device configured to aim the outgoing laser emission at the unmanned aerial device based on tracking information from the first PAT module;
an unmanned aerial vehicle optical communications device comprising:
a common optics arrangement configured to both receive the outgoing laser emission from the base station and transmit a return laser emission to the base station through a single shared aperture;
a second PAT module operating on a second computing device, the second PAT module configured to acquire and track the base station; and
a second solid-state beam steering device configured to aim the return laser emission at the base station optical communications device based on tracking information from the second PAT module; and
a fiber optic coupler between the common optics arrangement and the second solid-state beam steering device.
2 . The system of claim 1 , wherein the unmanned aerial vehicle optical communications device is configured as a payload for the unmanned aerial vehicle.
3 . The system of claim 1 , wherein the outgoing laser emission and the return laser emission are in the infrared spectrum from 800 nm to 1 mm.
4 . The system of claim 3 , wherein the outgoing laser emission and the return laser emission are in the range of 1,250 nanometers to 1,850 nanometers (1,550 nm+/−300 nm).
5 . The system of claim 1 , wherein:
the second solid state beam steering device comprises retroreflectors or micromirrors; and
the return laser emission is a reflection of the outgoing laser emission from the retroreflectors or micromirrors of the second solid-state beam steering device.
6 . The system of claim 1 , wherein:
the unmanned aerial vehicle optical communications device further comprises a second laser light source;
the return laser emission is a laser emission from the second laser light source; and
the second solid-state beam steering device comprises an optical phased array (OPA) or a photonic integrated circuits (PIC).
7 . The system of claim 1 , wherein:
the base station optical communications device further comprises:
a third laser light source configured to produce a second outgoing laser emission; and
a first dichroic mirror;
the unmanned aerial vehicle optical communications device further comprises:
a second dichroic mirror;
a beacon position detector; and
a data light detector;
wherein:
the first outgoing laser emission is a beacon signal at a first wavelength;
the second outgoing laser emission is a data signal at a second wavelength;
the first dichroic mirror is configured to merge the first outgoing laser emission and the second outgoing laser emission into a dual-wave beam aimed at the unmanned aerial vehicle;
the second dichroic mirror is configured to separate the dual-wave beam back into the first outgoing laser emission and the second outgoing laser emission;
the beacon position detector is configured to decode the beacon signal of the first outgoing laser emission; and
the data light detector is used to decode the data signal of the second outgoing laser emission.
8 . The system of claim 7 , wherein:
the first wavelength is in the range of 800 nanometers to 1,250 nanometers;
the second wavelength is in the range of 1,250 nanometers to 1,850 nanometers; and
the dichroic mirrors are configured to reflect the first wavelength and pass through the second wavelength.
9 . The system of claim 1 , wherein:
the base station optical communications device further comprises:
a first radio frequency communications subsystem;
a first link monitor operating on the first computing device; and
a first switching logic module operating on the first computing device;
the unmanned aerial vehicle optical communications device further comprises:
a second radio frequency communications subsystem;
a second link monitor operating on the second computing device; and
a second switching logic module operating on the second computing device;
wherein:
the link monitors monitor a quality of an optical communications connection and a quality of a radio frequency communications connection between the base station optical communications device and the unmanned aerial vehicle optical communications device;
when the switching logic modules determine that the quality of the optical communications connection falls below a threshold, they switch to radio frequency communications using the radio frequency communications systems, and vice-versa.
10 . The system of claim 9 , wherein a tracking control loop operating on the base station optical communications device comprising a cycle of detection of a laser emission, position error computation, control algorithm calculation, beam steering, and laser emission to a target operates at 1 millisecond or less per cycle.
11 . A method of free space optical communication for unmanned aerial vehicles, the method comprising the steps of:
at a base station optical communications device configured to transmit and receive optical signals:
producing an outgoing laser emission using a laser light source;
acquiring and tracking an unmanned aerial vehicle using a first pointing, acquisition, and tracking (PAT) module operating on a first computing device; and
aiming the outgoing laser emission at the unmanned aerial device using a first solid-state beam steering device based on tracking information from the first PAT module;
at an unmanned aerial vehicle optical communications device:
receiving the outgoing laser emission from the base station and transmitting a return laser emission to the base station through a single shared aperture using a common optics arrangement;
acquiring and tracking the base station using a second PAT module operating on a second computing device; and
aiming the return laser emission at the base station optical communications device using a second solid-state beam steering device based on tracking information from the second PAT module; and
coupling optical signals between the common optics arrangement and the second solid-state beam steering device using a fiber optic coupler.
12 . The method of claim 11 , wherein the unmanned aerial vehicle optical communications device is configured as a payload for the unmanned aerial vehicle.
13 . The method of claim 11 , wherein the outgoing laser emission and the return laser emission are in the infrared spectrum from 800 nm to 1 mm.
14 . The method of claim 13 , wherein the outgoing laser emission and the return laser emission are in the range of 1,250 nanometers to 1,850 nanometers (1,550 nm+/−300 nm).
15 . The method of claim 11 , wherein:
the second solid state beam steering device comprises retroreflectors or micromirrors; and
the return laser emission is a reflection of the outgoing laser emission from the retroreflectors or micromirrors of the second solid-state beam steering device.
16 . The method of claim 11 , wherein:
the unmanned aerial vehicle optical communications device further comprises a second laser light source;
the return laser emission is a laser emission from the second laser light source; and
the second solid-state beam steering device comprises an optical phased array (OPA) or a photonic integrated circuits (PIC).
17 . The method of claim 11 , further comprising the steps of:
at the base station optical communications device:
producing a second outgoing laser emission using a third laser light source;
merging a first outgoing laser emission and the second outgoing laser emission into a dual-wave beam aimed at the unmanned aerial vehicle using a first dichroic mirror;
at the unmanned aerial vehicle optical communications device:
separating the dual-wave beam back into the first outgoing laser emission and the second outgoing laser emission using a second dichroic mirror;
decoding a beacon signal of the first outgoing laser emission using a beacon position detector; and
decoding a data signal of the second outgoing laser emission using a data light detector;
wherein:
the first outgoing laser emission is the beacon signal at a first wavelength; and
the second outgoing laser emission is the data signal at a second wavelength.
18 . The method of claim 17 , wherein:
the first wavelength is in the range of 800 nanometers to 1,250 nanometers;
the second wavelength is in the range of 1,250 nanometers to 1,850 nanometers; and
the dichroic mirrors are configured to reflect the first wavelength and pass through the second wavelength.
19 . The method of claim 11 , further comprising the steps of:
monitoring a quality of an optical communications connection and a quality of a radio frequency communications connection between the base station optical communications device and the unmanned aerial vehicle optical communications device using a first link monitor operating on the first computing device and a second link monitor operating on the second computing device;
when a first switching logic module operating on the first computing device and a second switching logic module operating on the second computing device determine that the quality of the optical communications connection falls below a threshold, switching to radio frequency communications using a first radio frequency communications subsystem at the base station optical communications device and a second radio frequency communications subsystem at the unmanned aerial vehicle optical communications device, and vice-versa.
20 . The method of claim 19 , wherein a tracking control loop operating on the base station optical communications device comprising a cycle of detecting a laser emission, computing position error, calculating a control algorithm, steering a beam, and emitting a laser to a target operates at 1 millisecond or less per cycle.