A free-space optical (FSO) communication demonstration was conducted with JHU/APL and AOptix at the TCOM Test Facility in Elizabeth City, NC in May 2006. The primary test objective was to evaluate the performance of an FSO link from a fiber-tethered aerostat to a ground platform at effective data rates approaching 100 Gigabits/sec using wavelength division multiplexing (WDM) techniques. (Multiple optical channels operating near 1550 nm were modulated at data rates of 1, 10 and 40 Gbps). The test was conducted with a 38 meter aerostat raised to an altitude of 1 km and a ground platform located 1.2 km from the aerostat (limited by property boundary). Error free data transfers of 1.2 Terabits in 30 seconds at 40 Gbps were demonstrated. The total data transferred during the test was greater than 30 Terabits with an average BER of 10 -6 without any forward error correction (FEC) coding.
A 150 km free-space optical (FSO) communication link between Maui (Haleakala) and Hawaii (Mauna Loa) was demonstrated by JHU/APL and AOptix Technologies, Inc. in September 2006. Over a 5 day period, multiple configurations including single channel 2.5 Gbps transmission, single channel 10 Gbps, and four wavelength division multiplexed (WDM) 10 Gbps channels for an aggregate data rate of 40 Gbps were demonstrated. Links at data rates from 10 to 40 Gb/s were run in excess of 3 contiguous hours. Data on the received power, frame synchronization losses, and bit error rate were recorded. This paper will report on the data transfer performance (bit error rates, frame synchronization issues) of this link over a 5 day period. A micropulse lidar was run concurrently, and on a parallel path with the FSO link, recording data on scattering loss and visibility. Comparisons between the state of the link due to weather and the data transfer performance will be described.
We propose a design for a free space optical communications (FSOC) receiver terminal that offers an improved field of view (FOV) in comparison to conventional FSOC receivers. The design utilizes a microlens to couple the incident optical signal into an individual fiber in a bundle routed to remote optical detectors. Each fiber in the bundle collects power from a solid angle of space; utilizing multiple fibers enhances the total FOV of the receiver over typical single-fiber designs. The microlens-to-fiber-bundle design is scalable and modular and can be replicated in an array to increase aperture size. The microlens is moved laterally with a piezoelectric transducer to optimize power coupling into a given fiber core in the bundle as the source appears to move due to relative motion between the transmitter and receiver. The optimum position of the lens array is determined via a feedback loop whose input is derived from a position sensing detector behind another lens. Light coupled into like fibers in each array cell is optically combined (in fiber) before illuminating discrete detectors.
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