Army

Optical fiber positioner with wide frequency bandwidth

Precision alignment means better laser communication in free-space

Communications

Laser communication down optical fiber has greatly increased available bandwidth and the speed of data transfer to the point where terabits are moved every second across oceans. But as many in rural locations have experienced, optical fiber deployment is slow and costly. And, in areas were fiber cannot be run, such as between satellites, ships, and aircraft, we must rely on slow, radio frequency (RF) modes. Optical transmission through free-space promises to address this, but there are obstacles in the path towards reliable, high-throughput, fiber-less laser communications. One of those obstacles is the need for high-precision and dynamic devices for aligning the output end of the fiber signal. The extremely narrow divergence of beams used in free-space optics creates challenges for their pointing, acquisition, and tracking across large distances. For example, axial displacement of the optic fiber should be in the range of a fraction of a micron in order to obtain useful transmissions into free-space. Furthermore, frequency bandwidth for the fiber tip displacement should be in the range of hundreds or even thousands of hertz for keeping the spot on the target or receiver, effectively mitigating the wandering of beams for lower bandwidths. For this reason, optical fiber positioners are used in free-space laser transmissions but increased precision and speed of alignment is needed to obtain reliable, large-bandwidth communications.

Army researchers have developed a new optical fiber positioner to address the above limitations. The device utilizes piezoelectric actuators to precisely manipulate the fiber which is wrapped in a protective sheath. The Army invention also includes two highly accurate fixtures for use in construction of the fiber positioner capable of orienting the device components with repeatable accuracy. These fixtures make building arrays of the positioner easier and faster.

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