Philip H. Wisseman

Low-loss fiber optic time-delay element for phased-array antennas

We present a novel concept, the fiber optic Bragg grating true- time-delay (TTD) element, for implementing true time delay in the distribution network of an optically fed phased array antenna. the device utilizes narrowband optical Bragg reflection gratings written holographically into the core of a single-mode fiber at various positions along its length. An optical carrier is modulated by the RF signal of interest and launched into this delay-line fiber. The desired RF time delay may be realized by wavelength-selectable nature of the TTD device offers the possibility for simplified beamsteering control and channel multiplexing.

Optical electroabsorption modulators for wideband, linear, low-insertion-loss photonic links

We describe the characterization and development of semiconductor quantum well electroabsorption modulators (EAMs) for insertion into high-performance photonic links intended for analog applications. Limitations of existing approaches are described, motivating the potential of EAMs for exploiting the flexibility of semiconductor bandgap engineering. Relationships are established between basic modulator device characteristics and the RF system performance measures of link gain (insertion loss), bandwidth, noise figure, and dynamic range; results are then presented that have established the viability of EAMs for wideband, low-loss, linear analog photonic links.

Integrated optoelectronic interconnect for phased-array antenna applications

An integrated semiconductor interconnect chip is being developed for the distribution of microwave signals to the subarrays and/or radiating elements of a phased array antenna (PAA). The baseline chip design calls for a 1 X 4 distribution fanout, and consists of both waveguide splitters and integrated optical amplifiers to compensate for inherent splitting as well as excess waveguide and coupling losses. Analysis is being performed to evaluate the RF performance of photonic links containing semiconductor optical amplifiers, and to determine the most judicious use of such an interconnect in the photonic feed network of a PAA.