Proceedings Article | 28 April 2009
Proc. SPIE. 7316, Fiber Optic Sensors and Applications VI
KEYWORDS: Modulation, Waveguides, Sensors, Signal attenuation, Polymers, Modulators, Wave propagation, Antennas, Optical antennas, Electric field sensors
We present progress on advanced optical antennas, which are compact, small size-weight-power units capable
to receive super wideband radiated RF signals from 30 MHz to over 3 GHz. Based on electro-optical
modulation of fiber-coupled guided wave light, these dielectric E-field sensors exhibit dipole-like azimuthal
omni directionality, and combine small size (<< λRF) with uniform field sensitivity over wide RF received
signal bandwidth. The challenge of high sensitivity is addressed by combining high dynamic range photonic
link techniques, multiple parallel sensor channels, and high EO sensing materials. The antenna system
photonic link consists of a 1550 nm PM fiber-pigtailed laser, a specialized optical modulator antenna in
channel waveguide format, a wideband photoreceiver, and optical phase stabilizing components. The optical
modulator antenna design employs a dielectric (no electrode) Mach-Zehnder interferometer (MZI) arranged
so that sensing RF bandwidth is not limited by optical transit time effects, and MZI phase drift is bias
stabilized. For a prototype optical antenna system that is < 100 in3, < 10 W, < 5 lbs, we present test data on
sensitivity (< 20 mV/m-Hz1/2), RF bandwidth, and antenna directionality, and show good agreement with
theoretical predictions.
