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Proceedings Paper

Tunable optical true time delay generator for phased array antenna
Author(s): Olukayode Okusaga; Weimin Zhou; Gary Carter
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Paper Abstract

We present an application of fiber Bragg gratings as tunable optical delays in transmission for use as true-time-delay line in a RF-Photonic phased array antenna. Most delay line applications using fiber gratings require that they be used in reflection mode and they can provide only discrete variation of time delay. It also requires the use of bulky and expensive optical circulators. We have designed an optical true time delay array generator using fiber gratings in cascading transmission mode for such applications which significantly simplified the system and lowered the cost. A wavelength tunable laser is used as the light source. The laser light is modulated by an RF-microwave input signal, then enters into the optical true time delay array generator to provide a sequence of time delays Δt, 2Δt,...nΔt. The goal is to obtain large group delay Δt with low loss and with the capability of tuning Δt continuously by varying the wavelength of the laser. We combined an apodized grating profile, large index step and increased grating length to achieve our goal. We fabricated and tested the grating with about 100mm length which showed at least Δt=60 ps tunable time delay range. We have demonstrated the applicability of the transmission-mode fiber Bragg gratings in an optical true-time-delay type of phased array antenna.

Paper Details

Date Published: 28 February 2006
PDF: 11 pages
Proc. SPIE 6116, Optical Components and Materials III, 611608 (28 February 2006); doi: 10.1117/12.644802
Show Author Affiliations
Olukayode Okusaga, U.S. Army Research Lab. (United States)
Weimin Zhou, U.S. Army Research Lab. (United States)
Gary Carter, Univ. of Maryland, Baltimore County (United States)

Published in SPIE Proceedings Vol. 6116:
Optical Components and Materials III
Michel J. F. Digonnet; Shibin Jiang, Editor(s)

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