Free-space optical communications (FSO) systems have gained increasing interest for both defense and commercial applications due to their ability to provide secure, long-distance, high-capacity communications on the move. In terrestrial environments, because clouds and strong weather effects can limit FSO systems performance, integrating them with directional radio frequency (RF) links can yield a system that leverages the best of both modalities - the high capacity of FSO when available with the reliability of the RF link to ensure the highest priority data can be sent even during degraded weather conditions. This paper will present the development of a highly integrated FSO/RF link architecture implementing three key functionalities: (1) operation at data transfer rates up to 10 Gbps, (2) seamless failovers between the FSO and RF modalities, and (2) the necessary quality of service (QoS) mechanisms to handle the rate disparity between the two links while providing priority to critical data. This architecture utilizes a network transport system that provides layer 2 data transport and QoS arbitration across the FSO and RF modalities. Results from testing in lab as well as at outdoor ranges of up to 30 km will be presented.
Laser communications (Lasercomm) systems have gained increasing interest for both defense and commercial applications due to their ability to provide secure, long-distance, high-bandwidth communications on the move, without the need for RF spectrum management. This paper will present field test results from the U.S. Navy’s Trident Warrior 2017 fleet exercise, where a compact Lasercomm system was evaluated. As compared to previously demonstrated long range Lasercomm terminals, this compact terminal design leverages simultaneous transmit and receive spatial diversity to mitigate scintillation fades in a smaller form factor. In addition, a 10 Gbps retransmission capability has been integrated and tested to assure error-free data transport even through short duration path blockages and optical fades. The system was operated at full functionality over seven test days with network traffic loads ranging from 1 - 7.5 Gbps in bidirectional configurations. The system was exercised to a line of sight limited range of 45 km and showed capability through haze and even some levels of fog on multiple days.