NRL Develops a Fiber-Optic Beamformer Network

10/1/1997 - 54-97r
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Four Naval Research Laboratory (NRL) researchers have developed and demonstrated a fiber-optic beamformer for true time-delay steering of a two-dimensional transmitter array. They report that the beamformer is a cost-effective method for distributing the microwave signals and for providing a true time-delay function to antenna sub-arrays.

The research team includes: Drs. Michael Y. Frankel, Ronald D. Esman, and Paul J. Matthews of NRL's Optical Sciences Division and 0Mark D. Parent of NRL's Radar Division.

According to Dr. Frankel, "Phased-array antennas are finding increasing applications in modern commercial and military radar and communication systems. The individual element control that is possible with array antennas permits the implementation of such functions as dynamic beam steering and shaping. The distribution of microwave signals over fiber-optics is advantageous to metal waveguides in the areas of routing ease; system size and weight; signal loss and bandwidth; and susceptibility to electro-magnetic interference. Fiber-optic systems also make possible signal processing functions such as true time-delay, which is required for precise beam steering over wide frequency ranges.

The NRL group has developed a signal distribution technique that preserves all the advantages of fiber-optics technology. The speed of light in a material depends on light color. NRL's approach relies on this property to control the timing of signals in the system by changing the color of light. This technique overcomes the limitations typically associated with optics by providing a system that uses all commercially available components leveraging off the high-volume production of the telecommunications industry," says Dr. Frankel. The NRL approach is compact, affordable, provides for operation stability, covers a wide signal frequency range, and is based on all commercial components.

"The NRL team has demonstrated excellent performance of this approach for controlling one-dimensional and two-dimensional arrays over the 2 to 18 GigaHertz (GHz) frequency range. A communications array antenna based on this technology can directly support OC-192 type signal transmission capable of 10 Gigabits per second transmission (Gbps) (125,000 simultaneous voice channels at 64 Kilobits per second (Kbps)). A radar array antenna can directly support an unprecedented ~ 2 centimeter (cm) spatial resolution," concludes Dr. Frankel.

The research team reports, "This technology can be used on any broadband array antenna for both military and civilian applications." Future plans include refining this approach to use fiber Bragg gratings (FBG's) instead of dispersive fibers.

This research is sponsored by the Office of Naval Research (ONR).

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The U.S. Naval Research Laboratory provides the advanced scientific capabilities required to bolster our country's position of global naval leadership. The Laboratory, with a total complement of approximately 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 90 years and continues to advance research further than you can imagine. For more information, visit the NRL website or join the conversation on Twitter, Facebook, and YouTube.

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