communication platforms) at a significantly reduced expense in comparison with micro-wave-based satellite communication systems.

 

The Navy seeks a Group 1, 2, or 3 UAV capability to transmit video data in a FSO network including pointing an optical data beam from a first UAV to a second UAV during a first period of time, transmitting data from the first UAV to the second UAV during the first period of time, pointing the optical data beam from the first UAV to a third UAV during a second period of time, and transmitting data from the first UAV to the third UAV during the second period of time.

 

The UAVs in the FSO network should: (1) be mobile and autonomous with no Global Positioning System (GPS) support; (2) not use an out-of-band radio frequency (RF) link to exchange control information (e.g., their orientation and velocity), but can only use the FSO link itself; (3) not move on straight lines only, but in any direction; (4) be equipped with Inertial Measurement Units (IMU) giving them the sense of velocity and orientation; and (5) be equipped with two non-mechanical or micro-electro-mechanical (MEM) beam-steering FSO transceivers steerable hemispherical heads each, one on top and one at the bottom of the UAV, mounted with FSO transceiver, that have the ability to scan complete 360 degrees in the horizontal plane and 180 degrees in the vertical plane with each head, if need be multiple sensors are allowed in order to scan 360 degrees in the horizontal plane and 180 degrees in the vertical plane. During early design, the UAVs may initially use GPS and RF communication to discover each other, and then exchange information about their positions and point the FSO transceivers toward each other to initiate the FSO link. Once the FSO link is established while maintaining line of sight (LOS) exchanging data between the UAVs should be performed. The FSO metrics for measuring success are: (a) 1 to 2 gigabits of error-free data transport at ranges greater than 25 km in clear weather on the wavelength of 1550 nm; (b) voice communications at greater than 35 km in clear weather on the wavelength of 1550 nm; (c) chat messaging out to 45 km, the maximum available line of sight in clear weather on the wavelength of 1550 nm; and (d) repeatable, semiautomatic reacquisitions over the entire line-of-sight range.

 

The proposer must identify the beam steering technological problems that must be overcome or developed to realize the proposed UAV FSOC system. In addition to the number of links supported, the field of view, space, weight, power, throughput, and expected terminal cost are also important performance parameters. As a point of comparison, the Navy funded the development of a single-beam optical terminal [Ref 1] with an optical antenna that was less than 1 cubic foot in size and less than 20 lbs. in weight. The Navy seeks to have a multi-beam capability (i.e., 2 to 3 beams full duplex) to operate in Group 3 UAVs within 1 cubic foot in size and less than 20 lbs. in weight.

 

Performance non-mechanical or micro-electro-mechanical (MEM) beam steering objectives are: (a) Field of Regard (FoR) 60 degrees azimuth 30 degrees elevation; (b) Throughput optical power greater than 80 percent; (c) Pointing Accuracy less than 10 microradians; (d) Optical Power Handling Capability (pulsed) >greater than 4 kW; (e) Optical Power Handling Capability CW greater than 10 W.; and (f) Electrical Power Consumption less than one watt.

 

PHASE I: Develop an initial conceptual design for a full-duplex FSO Communication Link. Perform design modeling in order to provide a conceptual design trade study for the proposed UAV FSO network. The Phase I option period, if exercised, may include developing a Group 3 UAV FSOC initial system terminal design that includes beam director with laser source(s) performance estimates for the number of links that can be supported (objective is 2 to 3 simultaneous bi-directional laser links), field of view, size, weight, power, throughput, and anticipated terminal cost. Develop a concept for the Group 3 UAV FSO relay node that addresses how the fully stabilized multi-beam (minimum 2 beams full-duplex) optical head provides 360 degrees azimuth and 105 degrees elevation coverage on Group 3 UAVs. Single or multiple aperture systems may be considered, with special emphasis on minimizing beam blockage while steering and inter-beam handoffs. The option, if exercised, will be used to further refine the terminal initial system design to address any technical or performance risks that are identified (i.e., inter-UAV node discovery, beam steering, autonomous beam pointing, acquisition, and tracking (PAT), link adaptation and (beam-to-beam) handoff). Undergo Navy design assessment of the technical merits of the proposed design and its suitability for potential installation on Group 3 UAVs for Phase II selection. A successful design must also include how the point, tracking, acquisition, and stabilization is accomplished to enable operations from Group 3 UAVs acting as a communications relay. The Phase I effort will include prototype plans to be

developed under Phase II.

 

PHASE II: Develop a prototype based on the Phase I design; and test critical technical components to validate maturity and expected performance. Propose, test and validate mitigations for any technical issues that are discovered during the Phase II testing and assessment. In the first Phase II option, if exercised, improve the Group 3 UAV preliminary terminal design to address any technical or performance risks identified during the Phase II base period with the objective of developing a prototype design that addresses the Navy's concerns with the Group 3 UAV FSOC system original design. In the second Phase II option, if exercised, fabricate the prototype UAV FSOC multi-beam optical terminal and perform initial testing to validate its performance. Realize the objective of a functioning terminal with sufficient test data to validate terminal performance operating on a Group 3 UAV FSOC system in land and ship board environments. Collect test data of interest: signal fading and range limitations quality- of-service (QoS), low latency, low packet error rates, and reduced network congestion.

 

PHASE III DUAL USE APPLICATIONS: Assess the prototype terminal's performance as part of a TRL 6 or higher demonstration to support a transition. Support installation of the terminal on military Group 3 UAV platforms, with all of the required gimbaling for pointing and tracking, to support a demonstration at an appropriate experimentation venue. Support additional technology insertions as required and an open architecture system to accommodate various optical modems, software algorithm updates, tech refresh opportunities, and platform integration requirements.

 

The private sector uses optical communications systems between fixed (e.g., buildings) and/or mobile sites. Private companies (i.e., SpaceX and OneWeb) are involved in efforts to deliver Internet service via a constellation of satellites in low earth orbit. Optical communications between these satellites could potentially provide the high- capacity backbone required to deliver broadband services to end users. All of these private sector applications could benefit from multi-beam, optical terminal technology.

 

This technology also could have significant impact on the cellular phone and data industry. The ability to rapidly deploy a network could change the industry. It could move from tower-based systems, which have reception problems, to unmanned systems that could be more robust and cheaper. This technology also has potential humanitarian and homeland defense applications to bring in a temporary network to supplement a damaged one until repairs can be made. The FSO market as of 2015 was $120M and expects to reach $1B by 2020.

 

Examples of commercial applications include law enforcement, security, cinema, broadcast, newsgathering, energy resource monitoring, and firefighting.

 

REFERENCES:

1.  Thomas, Linda and Moore, Chris. �TALON � Robust Tactical Optical Communications.� CHIPS Magazine, Oct. Dec. 2014. http://www.doncio.navy.mil/CHIPS/ArticleDetails.aspx?id=5550

 

2.   Kaushal, Hemani and Kaddoum, Georges. �Free Space Optical Communication: Challenges and Mitigation Techniques.� arXIV, 16 June 2015. http://arxiv.org/pdf/1506.04836.pdf

 

3.   Malik, Aditi and Singh, Preeti. �Free Space Optics: Current Applications and Future Challenges.� International Journal of Optics, Volume 2015, Article ID 945483, 29 September 2015. http://www.hindawi.com/journals/ijo/2015/945483/-

 

4.   Son, I. K. and Moa, S. "A Survey of Free Space Optical Networks." Digital Communications and Networks, Vol 3, Issue 2, May 2017, pp. 66-77. http://www.sciencedirect.com/science/article/pii/S2352864816300542

 

5.   Demers, F., Yanikomeroglu, H., and St-Hiliare, M. "A Survey of Opportunities for Free Space Optics in Next Generation Cellular Networks." IEEE Computer Society, 2011 Ninth Annual Communication Networks and Services Research Conference, 2-5 May 2011. https://ieeexplore.ieee.org/document/5771213