Abstract: An optical fiber amplifier employing a prism to optimally couple pump energy into the pump core of a dual clad fiber. The optical fiber amplifier consists of a dual clad fiber having an inner (e.g., signal) core, an outer (e.g., pump) core surrounding the inner core, and a cladding layer at least partially surrounding the outer core. Pump energy can be injected into the outer core through the prism located adjacent to the outer core in order to amplify signals propagating through the inner core.

Abstract: A real-time control system for an optical phased array is disclosed that comprises a computationally efficient algorithm for calculating phase differences between a plurality of array beamlets and a reference plane wave and further generates phase correction signals that are transmitted to a plurality of phase modulators to realign the array beamlets to compensate for external perturbations and atmospheric aberrations. The phase measurements are based on a phase angle of a complex number comprising square wave functions, and alternately, based on a phase angle of a complex number comprising sine and cosine functions to correct for harmonic content of phase measurements. Furthermore, the phase correction signal is based on the phase measurement times modulo2&pgr;.

Abstract: A real-time control system for an optical phased array is disclosed that comprises a computationally efficient algorithm for calculating phase differences between a plurality of array beamlets and a reference plane wave and further generates phase correction signals that are transmitted to a plurality of phase modulators to realign the array beamlets to compensate for external perturbations and atmospheric aberrations. The phase measurements are based on a phase angle of a complex number comprising square wave functions, and alternately, based on a phase angle of a complex number comprising sine and cosine functions to correct for harmonic content of phase measurements. Furthermore, the phase correction signal is based on the phase measurement times modulo2&pgr;.

Abstract: An optical fiber amplifier employing a prism to optimally couple pump energy into the pump core of a dual clad fiber. The optical fiber amplifier consists of a dual clad fiber having an inner (e.g., signal) core, an outer (e.g., pump) core surrounding the inner core, and a cladding layer at least partially surrounding the outer core. Pump energy can be injected into the outer core through the prism located adjacent to the outer core in order to amplify signals propagating through the inner core.

Abstract: A method for compensating a reference signal used in a coherent receiver of a micro-doppler sensor having a transmitter includes the steps for: (a) repeatedly measuring phase differences between a signal emitted by the transmitter a first time and a previous signal emitted at a previous time so as to produce a plurality of phase error signals; (b) accumulating the phase error signals over a propagation time between the transmitter and the coherent receiver so as to produce a cumulative phase error signal; and (c) modulating a signal produced by the transmitter at the end of the propagation period so as to generate a compensated reference signal having a phase characteristic substantially identical to the signal produced by the transmitter at the beginning of the propagation period. A phase error or noise compensator, which can form part of a micro-doppler ladar system, is also described.

Abstract: A single mode optical waveguide includes a first region having a relatively high refractive index, a second region having a relatively low refractive index disposed adjacent to the first region, and a dopant region overlapping the first and second regions. Preferably, the first and second regions are circular regions which are concentric with respect to one another. Moreover, the dopant material in the dopant region advantageously can have a non-uniform dopant gradient. In addition, a predetermined percentage of dopant material defining the dopant region is disposed coincident with the second region. Preferably, the predetermined percentage is greater than or equal to 10 percent and, most preferably, the predetermined percentage is greater than or equal to 50 percent. Alternatively, the first region corresponds to an inner core of a dual core optical fiber, while the second region corresponds to an outer core of the dual core optical fiber.