A hybrid wireless optical and radio frequency (RF) communication link utilizes parallel free-space optical and RF paths for transmitting data and control and status information. The optical link provides the primary path for the data, and the RF link provides a concurrent or backup path for the network data, as well as a reliable and primary path for the control and status information. When atmospheric conditions degrade the optical link to the point at which optical data transmission fails, the hybrid communication link switches to the RF link to maintain availability of data communications. The switch may occur automatically, based on an assessment of the quality of the optical signal communicated through the optical path.

Hybrid wireless optical and radio frequency communication link

A system and method for establishing a laser link communications system in free space includes first and second terminals which are distanced from each other on an optical path. Each terminal includes a plurality of laser transmitters which together generate a plurality of laser beams, with each of the laser beams carrying a communication signal. Further, each terminal directs its independently generated laser beams along substantially parallel paths. Though their paths are substantially parallel, the transmitted beams generally overlap in the far field, at the other terminal, where they are collected and incoherently summed for reception and analysis of the communication signal.

Multiple transmitter laser link

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.

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

Erbium doped fiber amplifiers (ERDAs) optically couple optical signals between free-space and fiber optic links of a terrestrial optical communication network. The optical gain of transmitting and receiving ERDAs is controlled to achieve good optical signal communication. Control occurs in response to signals received at the transmitting and receiving ends of the links. Control, status and management information may be communicated optically between link head stations. The physical position of transceivers at opposite ends of the link optical signal paths is also controlled.

Method and apparatus for free-space optical communication without eletro-optical conversion

The present invention provides an apparatus and method for free-space optical communication. The apparatus includes a first board with a plurality of optoelectronic converter components mounted on the first board. The apparatus additionally includes at least one optics element optically aligned with at least one of the optoelectronic converter components, where the optics element is configured to pass light directly between free-space and the plurality of optoelectronic converter components, and electronics coupled to at least one of the plurality of optoelectronic converter component. In one embodiment, communication is achieved by providing electric signals to a plurality of lasers that are mounted on a first board, generating a plurality of optical signals with the plurality of lasers and directing the plurality of optical signals into free-space with a plurality of optics elements.

Apparatus and method for use in free-space optical communication comprising optically aligned components integrated on circuit boards

Laser satellite networking is a key element of effective communications operations to support both strategic and tactical missions. Lasercom offers a number of important advantages over conventional RF satellite communications. The shorter wavelength available using lasers provides higher data rates at less power and smaller apertures, both resulting in lower weight requirements. On the other hand, lasercom entails more difficulty in acquisition and tracking because of the narrow beams used. Technology problems to be overcome before intersatellite laser communications can reliably outperform RF communications include acquisition in the presence of significant background light from the earth, tracking to resolutions of a few microradians, high speed modulation of semiconductor lasers with close to one watt of power in a diffraction limited beam, high bandwidth low noise detector response, and demonstrated long term performance. We have developed critical technologies to solve some of these problems, and demonstrated them in a laboratory testbed which also supports development and testing of network protocols and algorithms. Our hardware provides new capability in background light rejection by using innovative atomic line filter technology, improved tracking accuracy by using innovative zero backlash Roto-Lok drive gimbal telescopes, and increased communications bandwidth by incorporating multi-link networking protocols.

Status of SDIO/IS&T lasercom testbed program

Laser communications between satellites, high flying aircraft (such as JSTARS), and the ground offer the potential to transfer extremely high amounts of information faster and with a much smaller package than is possible using current radio frequency and microwave technologies. This can be especially important in downlinking time sensitive satellite reconnaissance information because the satellite stays within range of a ground station or aircraft for only a few minutes. A capability to downlink from a satellite to an aircraft can provide all weather performance, and multiple data transfers for every satellite orbit. Over the last few years, SDIO (now BMDO) has funded a number of technology efforts through the US Army Space and Strategic Defense Command reducing the risks associated with laser communications. This paper describes one of these efforts which is now being carried forward to an Advanced Technology Demonstration at ThermoTrex Corporation. The program will lead to the demonstration of high data rate communications of 270 MBPS (Mega Bits Per Second) to 1.08 GBPS (Giga Bits Per Second) between high altitude aircraft and possibly between a satellite and the ground. The Laser Communications Terminals incorporate Atomic Line Filter technology for background light rejection during acquisition, reactionless Roto-Lok offset cable drive gimbals for fast slewing and high accuracy pointing, and direct digital modulation of semiconductor diode lasers detected with low noise avalanche photodiodes. We present designs and preliminary performance results for both a simplified terminal appropriate for a near term satellite-to-ground data transfer experiment, and a full capability terminal appropriate for ground, aircraft, or satellite operations.

Irene H. Chen

Papers

Status of SDIO/IS&T lasercom testbed program

Status of BMDO/IST lasercom advanced technology demonstration

An Coarse-fine Wi-Fi Localization base on Trilateration, KNN algorithm and Classification and Regression Tree