Abstract: A large mode area fiber amplifier suitable for high power applications includes a core region specifically configured to allow for high power operation while also limiting the amount of SBS that is generated. The composition of the core region is selected to include a dopant (such as aluminum) in selected areas to reduce the acoustic refractive index of the core and limit the spatial overlap between the acoustic and optical fields. The acoustic refractive index is also structured so that the acoustic field is refracted away from the central core area. In one embodiment, the core may comprise a depressed index center portion and surrounding ring core area, with the center portion including the aluminum doping and the ring formed to have a diameter less that the phonon decay length for the operating wavelength(s).

Abstract: A large mode area fiber amplifier suitable for high power applications includes a core region specifically configured to allow for high power operation while also limiting the amount of SBS that is generated. The composition of the core region is selected to include a dopant (such as aluminum) in selected areas to reduce the acoustic refractive index of the core and limit the spatial overlap between the acoustic and optical fields. The acoustic refractive index is also structured so that the acoustic field is refracted away from the central core area. In one embodiment, the core may comprise a depressed index center portion and surrounding ring core area, with the center portion including the aluminum doping and the ring formed to have a diameter less that the phonon decay length for the operating wavelength(s).

Abstract: A large mode area fiber amplifier suitable for high power applications includes a core region specifically configured to allow for high power operation while also limiting the amount of SBS that is generated. The composition of the core region is selected to include a dopant (such as aluminum) in selected areas to reduce the acoustic refractive index of the core and limit the spatial overlap between the acoustic and optical fields. The acoustic refractive index is also structured so that the acoustic field is refracted away from the central core area. In one embodiment, the core may comprise a depressed index center portion and surrounding ring core area, with the center portion including the aluminum doping and the ring formed to have a diameter less that the phonon decay length for the operating wavelength(s).

Abstract: A large mode area fiber amplifier suitable for high power applications includes a core region specifically configured to allow for high power operation while also limiting the amount of SBS that is generated. The composition of the core region is selected to include a dopant (such as aluminum) in selected areas to reduce the acoustic refractive index of the core and limit the spatial overlap between the acoustic and optical fields. The acoustic refractive index is also structured so that the acoustic field is refracted away from the central core area. In one embodiment, the core may comprise a depressed index center portion and surrounding ring core area, with the center portion including the aluminum doping and the ring formed to have a diameter less that the phonon decay length for the operating wavelength(s).

Abstract: An arrangement for reducing the effects of pump signal relative intensity noise (RIN) in a Raman fiber amplifier. A portion of the output from a pump laser source is applied as an input to a compensating, lower power laser module, where fluctuations in the output power of the pump laser are used to control the bias current applied as an input to the compensating laser such that as the pump power increases, the bias current (and lower power laser output) decreases; conversely, as the pump power decreases, the bias current applied as an input to the compensating laser will be increased. The result is a relatively flat gain as seen by the information signal, thus minimizing the transfer of relative intensity noise from the pump to the signal.

Abstract: An arrangement for reducing the effects of pump signal relative intensity noise (RIN) in a Raman fiber amplifier. A portion of the output from a pump laser source is applied as an input to a compensating, lower power laser module, where fluctuations in the output power of the pump laser are used to control the bias current applied as an input to the compensating laser such that as the pump power increases, the bias current (and lower power laser output) decreases; conversely, as the pump power decreases, the bias current applied as an input to the compensating laser will be increased. The result is a relatively flat gain as seen by the information signal, thus minimizing the transfer of relative intensity noise from the pump to the signal.

Abstract: A stress-driven electrostrictive ceramic low-voltage plate voltage sensor based on the principle of the field-coupling between the strain and polarization in the ceramic material of the device. Application of a dithering or driving voltage to a piezoelectric tube thereby generating an oscillating polarization whose amplitude is proportional to an applied low-frequency voltage. A electrostrictive ceramic wafer material affixed to the piezoelectric tube senses this oscillation and generates a displacement current. The displacement current represents a voltage output that is an amplitude modulated carrier whose displaced amplitude is proportional to an applied unknown signal voltage sought to be determined.

Abstract: A system for determining the angular velocity of a mobile target relative to a station. The system develops first and second reference beams and a beam to the target to enable the target to generate first and second signals. Optical devices, preferably fiberoptical devices, responsive to the first and second reference beams and to the first and second signals respectively received from the target at discrete first and second positions on the station, respectively produce first and second interference pattern signals. Each of said received signals has a Doppler shift as a function of the movement of the target. An electrical processing circuit then processes the interference pattern signals to develop a signal indicative of the target's angular velocity.

Abstract: A single magnetostrictive amorphous metal sensor element is mounted on a piezoelectric resonator plate with an intervening layer of a viscous fluid, an oscillator stresses and vibrates the plate at a resonant frequency, creating a standing wave in the sensor element which is a metallic glass ribbon. Electromotive forces are generated in first and second pickup coils mounted at symmetrically spaced positions about the ribbon centerline. The electromotive force generated by each pickup coil is demodulated by a lock-in amplifier with a signal supplied by the oscillator. The demodulated outputs are amplified so as to balance the sensitivities. Outputs of amplifiers are provided to a differential amplifier which produces the gradiometer output indicative of magnetic field gradient.

Abstract: A highly-sensitive, physically small and rugged magnetometer employs a magnetostrictive amorphous metal ribbon core. A piezoelectric driver induces stress variations in the ribbon of a magnitude determined by an external magnetic field. The amplitude of the variations in magnetization is sensed by a pick-up winding disposed around the ribbon core. The dynamic range of the device is improved by employing a nulling field winding around the core to continuously null out the magnetization of the core. In contrast to the non-linear characteristic of the conventional fluxgate magnetometer, the invention provides a linear response to magnetic field strength which simplifies the processing circuitry. In addition, the ribbon may be field-annealed to improve the sensitivity of the device.

Abstract: A highly sensitive magnetometer employs a magnetostrictive amorphous metal core in which a piezoelectric driver induces stress variations. In the presence of an external magnetic field, the magnetization of the magnetostrictive core varies in relation to the induced stress. The amplitude of the variations in magnetization is proportional to the strength of the external field and is sensed by a pick-up winding disposed around the magnetostrictive core. The dynamic range of the device is improved by employing a bucking field winding around the core to null out the magnetization of the core. In contrast to the inherent non-linear characteristic of the conventional fluxgate magnetometer, the invention inherently provides a linear response to magnetic field strength.

Abstract: A magnetic field sensing transducer which converts magnetic field intensity into a magnetostrictive strain and transfers that strain to an optical fiber employs a thin wall, hollow, cylindrical shell around which is wound a ribbon of an amorphous metallic magnetostrictive material. In another embodiment, the entire shell is formed by turns of the ribbon of magnetostrictive material. The optical fiber is coiled around the magnetostrictive cylinder formed by the wound ribbon and at both its ends, the optical fiber is affixed to the shell. The shell is covered at both its ends by caps and forms a thin wall resonator having three normal axisymmetric modes of vibration. The torsional vibratory mode is here of no interest because it does not appreciably couple to the optical fiber. Any one of the other two axisymmetric modes of vibration can be made dominant by selection of the appropriate length to radius ratio of the cylindrical shell.

Abstract: A signal processor is arranged to process polarized light signals obtained from a stress sensor of the type having a photoelastic element that responds to stress by causing a phase difference between components of the polarized light propagating through that element. The stress sensor provides two output beams, each of which has a different polarized component of the transmitted light. The signal processor employs a pair of photodetectors which respond to the intensities of the two polarized light beams by converting the polarized light into electrical signals. Those two electrical signals provide the inputs to a difference differentiator that provides an output proportional to the difference between the derivatives of the inputs. The two electrical output signals of the photodetectors are also applied as inputs to a multiplier whose output is related to the product of its inputs.