Abstract: A method passively locks and phases an array of fiber amplifiers in a fiber amplifier system that emits a beam, such as a laser beam. The method locks the fiber amplifiers so that the fiber amplifiers operate at same or similar frequencies. The method samples a small portion of the emitted beam in a far-field around a central lobe on an optical axis and then couples this portion of emitted beam back into the array of fiber amplifiers. The fiber amplifiers may be phased so that the emitted beam concentrates its energy around the central lobe in the far-field. Phasing may be achieved by using an aperture, for example, to restrict the portion of the emitted beam to be coupled back to a restricted region around the optical axis.

Abstract: An optical network monitor and a method for monitoring the optical signals of an optical network including a spectrograph that includes a detector array, a processor and outputs. The network monitor receives an optical input signal which includes individual channels. The optical signal is transmitted onto the spectrograph which disperses the optical signal into the individual channels. The individual channels are directed onto the detector array so that the channels are spaced across the detector array. The detector array detects the channels in parallel and transmits to the processor channel parameter data which is processes the parameter data through internal algorithms to produce the outputs.

Abstract: A four-port Wavelength-Division-Multiplexing (WDM) element is disclosed that can be employed for various purposes in optical communication networks, particularly in bi-directional fiber optic lines. In one embodiment, one four-port WDM element is used with one optical amplifier to provide bi-directional propagation on the same fiber. In another embodiment, the four-port element is used in conjunction with optical attenuators to provide for gain equalization of channels and the flexibility to add or remove channels. In yet another embodiment, input and output ports are added to current-art elements thereby enabling bi-directional operation to be achieved with equipment that does not provide such capabilities.

Abstract: A bidirectionally amplifying rare earth doped fiber optical amplifier having an equalized gain at multiple wavelengths is disclosed for use in dense wavelength multiplexed bidirectional fiber transmission applications. In a first embodiment, a four port circulator is utilized with two amplifying fibers; one for each direction of propagation and a multiplicity of gratings configured to equalize the gain at the different wavelengths. Different embodiments utilizing three port and four port circulators are utilized. A more general amplifier device with equal gain at multiple wavelengths is disclosed.

Abstract: Resonant cavity apparatus comprise a Fabry-Perot optical resonant cavity of a type having families of transverse modes between longitudinal TEM.sub.00 modes. In such resonant cavity apparatus and in methods of minimizing the effect of transverse modes, families of such transverse modes are merged into longitudinal TEM.sub.00 modes of the non-confocal Fabry-Perot optical resonant cavity, providing superior optical performance. This may be manifested by a transmission spectrum similar to that of a flat-flat Fabry-Perot cavity, but with superior Finesse and transmission efficiency.

Abstract: Methods and apparatus for mode coupling a light beam into an optical cavity provide an input fiber pigtail with a fiber endface at one end of that input fiber pigtail. A cavity input aperture adapter is made integral with that input fiber pigtail at an opposite end of that input fiber pigtail for attachment to the housing of the optical cavity at its light input aperture. The input fiber pigtail is provided with a fiber input coupler integral with that input fiber pigtail at the above mentioned one end of the input fiber pigtail. That fiber input coupler has an integrated lens for focusing the light beam onto the fiber endface. The cavity input aperture adapter has a lens assembly for directing light from the above mentioned opposite end of the fiber pigtail into the input aperture of the optical cavity. Either the fiber input coupler or the cavity input aperture adapter may be omitted in different embodiments.

Abstract: A multioscillator ring laser gyroscope includes a frame that encloses a closed optical path in which four circularly polarized optical waves propagate. A combining optics system combining the waves to produce an interference pattern. A pair of photodetectors are placed in the interference pattern in half quadrature with respect to the interference pattern so that the detectors produce oscillatory output signals that are in quadrature with respect to each other. Signals indicative of the beat signal in the interference pattern are processed to determine the rotation rate, the direction of rotation and to provide a cavity length control signal.

Abstract: An apparatus and method for path length control for a laser gyro using two external gain cells and the shifted gain spectra of two neon isotopes. The laser cavity is stabilized by detecting the difference in the amplification rate between the two gain cells that are traversed by two rays. Absorption cells may be used to replace the gain cells.