Abstract: One method of determining the signal to noise ratio of an optical signal models the noise floor based on amplified spontaneous emission (ASE) which is accumulated along the link. The ASE wavelength dependence is represented by a known mathematical function with a limited number of parameters. The parameters of this function are derived from measurements of the noise floor at a limited number of points by computational best fit means. A number of fiber grating filters at wavelengths between ITU allocated wavelengths are used to sample the optical noise and reflect the light back. An optical circulator is used to direct the reflected ASE light to an optical switch which allows the detector to select between transmitted and reflected light. The signal transmitted through the switch is monitored by a scanning filter with the appropriate resolution to resolve the signal or noise peaks. A first scan of the transmitted peaks is carried out and the signal is digitized and stored.

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: A system and method are disclosed for adjusting the gain profile of an optical amplifier including a pump laser and an active gain element by selectively controlling the electron populations of at least one Stark sublevel of the electronic energy levels of the optical amplifier's active gain element. By dynamically controlling the electron populations of selected Stark sublevels the gain profile of the active gain element can be flattened. In a first method for controlling electron populations two-photon transitions are initiated between a pair of Stark sublevels of the same energy manifold of the active gain element. Two-photon transitions are stimulated by two additional pump lasers operating at wavelengths whose difference approximates the energy difference in the pair of Stark sublevels between which electrons are to be moved.

Abstract: Digital information is represented by surface designs with features smaller than the wavelength of the reading light on the surface of a record carrier, said designs producing continuously varying phases of the light reflected from them in a given direction. The designs are written by ion beam or electron beam milling of the surface of a master record carrier, then replicated onto a plurality of polymeric record carriers by stamping or molding. The records can also be written by applying light induced compaction of the surface materials.

Abstract: A method and apparatus are disclosed for predicting the failure of semiconductor lasers. To predict the failure of a particular semiconductor laser, operational characteristics that are predictive of a laser's health are computed while the laser is in use (e.g., while the laser is transmitting a signal or pumping an optical amplifier or solid state laser). This is done by modulating the injection current of the semiconductor laser and observing changes in laser parameters such as output power and junction voltage. From these observations, various laser characteristics can be computed including current threshold, slope efficiency and dynamic resistance. By carefully selecting the injection current modulation frequency and degree, the system in which the laser is used is not significantly disturbed by the changes in output power.

Abstract: Digital information is represented by surface steps orthogonal to the surface of a record carrier, said steps having a plurality of values between one tenth and 10,000 nanometers. The steps are read out by an optical differential interference method that is capable of resolving one tenth of a nanometer. The steps are written by a repeated masking and etching technique to form a master record carrier on glass from which a stamper is formed by molding and used to stamp replicate record carriers in polymeric material. In a different embodiment of the record carrier the surface steps are created by a modulated laser beam that ablates an integral number of layers from a pre-coated multilayer structure. In a third embodiment the data is represented by modulating the index of refraction between spots on a thin material film. The index difference is written optically. An extension to multiple thin film layers is also disclosed.

Abstract: A radio frequency excitation system is disclosed for use in conjunction with a ring laser gyroscope. The radio frequency excitation system is comprised of a closed resonant cavity which surrounds a helical coil driven at a high radio frequency at a range of 5 to 550 megahertz. This closed resonant coil surrounds one leg of a ring laser gyroscope which is carved out and exposed so that it may be surrounded by the resonant cavity. Using such a radio frequency excitation system eliminates the need for high power DC discharge components such as cathodes and anodes, as well as problems inherent with properly sealing the cathodes and anodes to the monolithic frame of the ring laser gyroscope.

Abstract: A compact three axis ring laser gyroscope having six laser corner mirrors which are positioned on the faces of a parallelopiped laser block, and method for making. Preferably the laser block is a cube. The laser block has a plurality of conduits therein for defining a plurality of closed laser beam-paths for guiding counterpropagating laser waves. Each laser beam-path has a gain medium therein and is formed to define a sensing axis for detection of rotations of the laser block. A single cathode is positioned inside the laser block, preferably substantially at its geometric center, and a plurality of anodes are mounted to the laser block and spaced apart from the cathode. A ion flow path is formed between each anode and the cathode such that application of a suitable electrical potential difference between the anodes and the cathode produces counterpropagating laser beams in each laser beam-path.

Abstract: A method and associated apparatus for measuring the intensity decay time of an optical cavity is particularly useful for accurate measurement of cavities of the type that include highly reflective mirrors. In the method, apparatus is provided for generating at least one pulse of laser light having a bandwidth that exceeds the resonant frequency spacing of the optical cavity and for directing that pulse into the cavity. The intensity of the light within the cavity is then measured and the amount of time is determined for such intensity to decay from a first predetermined value to a second predetermined value.