Abstract: A smart node is provided for use in an optical communications network wherein the smart node comprising dynamically reconfigurable optical signal manipulation devices in combination with sensing devices and processors to provide real time closed and open loop control of various channels of the network.

Abstract: An optical coupling device is provided for coupling a pump light into an optical waveguide such as an optical fiber or planar waveguide. An optical source provides a pump light. A large diameter optical waveguide is arranged in relation to the optical source, has a diameter substantially greater than 0.3 microns, and includes a reflective surface that reflects the pump light and provides a reflected pump light to the optical fiber. The reflective surface may be either a notched surface of a V-shaped indentation or a cleaved end of the large diameter optical waveguide. Alternatively, the optical coupling device is includes a side tap lens mounted to the large diameter optical waveguide for directing pump light provided by the optical source. The side tap lens is arranged in relation to the optical source and includes a reflective surface that reflects the pump light and provides a reflected pump light to the large diameter waveguide, which directs the pump light to the optical fiber.

Abstract: A system for lasing includes a diode laser array for emitting light of wavelength .lambda..sub.0, a tunable Bragg grating fiber laser connected to the diode laser array for emitting single mode light of wavelength 2*.lambda..sub.vis, a cladding pumped power amplifier connected to the diode laser array and the tunable Bragg grating fiber laser, and a second harmonic generator, including an optical cavity and crystal, connected to the cladding pumped power amplifier for emitting light of wavelength .lambda..sub.vis. The second harmonic generator is maximized, thereby maximizing emission of the light of wavelength .lambda..sub.vis, by control electronics connected to the tunable Bragg grating fiber laser, the cladding pumped power amplifier, and the second harmonic generator. The control electronics stabilize the amplitude of the light of wavelength 2*.lambda..sub.vis, emitted by the tunable Bragg grating fiber laser and lock the frequency of the light of wavelength 2*.lambda..sub.

Abstract: A fiber optic, Faraday-effect current sensor (optical current transducer) which has improved temperature sensitivity due to compensation for temperature-induced variations of the Verdet constant. Fiber optic sensing coils can exhibit shifts in their bias angle due to a number of reasons, including physical rotation of the fibers, an apparent circular birefringence attributable to the sensing coil shape (Berry's phase), circular birefringence in the sensing fiber, or a DC magnetic field or current. The present invention takes advantage of the change in bias angle by identifying a preferred channel from the two sensing axes of the output fiber, based on the manner in which these axes respond to the change in bias angle. One of the axes will exhibit a change in sensitivity that exacerbates the change in sensitivity due to the Verdet constant, while the other channel will exhibit a change that complements, or compensates for, the change in sensitivity due to the Verdet constant.

Abstract: A Faraday effect current sensor uses a plurality of concatenated field sensors, with a single light source and a single detector. At least two Faraday effect sensing elements (single mode sensing fibers) are used, preferably at least three, the sensing elements being interconnected by fusion spliced, polarizing fibers. The sensing fibers may be oriented generally straight, and arranged to form a regular polygon, e.g., an equilateral triangle for a three-element sensor. The locations of the splices between the sensing fibers and the polarizing fibers may further be advantageously arranged such that the sensing fibers form a substantially closed path which may be placed about the current-carrying conductor. The linearity of the sensor response may be improved by selecting an appropriate value of the bias angle of each sensing element, optimally equal to arctan?1/.sqroot.(2n-1)! where n is the number of sensing elements.

Abstract: A fiber optic subassembly for a Faraday-effect current sensor has an optical sensing fiber supported by a tubular holder in a square or rectangular configuration, with the three of the four corners thereof designed with bends which have a net zero bend-induced birefringence. The bends are formed by providing two loops which have effective angles of about 90.degree., the two loops lying in orthogonal planes, such that the fast axis of birefringence in the first loop is parallel to the slow axis of birefringence in the second loop, and the slow axis of birefringence in the first loop is parallel to the fast axis of birefringence in the second loop. In this manner, retardance accumulated in the first loop is offset by retardance accumulated in the second loop. If the loops are substantially identical, the offsetting of the retardance is effectively complete such that the bend exhibits negligible bend-induced birefringence.

Abstract: A single-frequency fiber-optic ring laser exhibits improved frequency stability, reduced laser intensity noise, broad tunability and narrow linewidth. The fiber-optic ring laser includes a ring-resonator with a length of single-mode optical fiber, a gain medium of rare earth-doped fiber, a broad-band fiber Fabry-Perot filter for wavelength tuning of the laser, a narrow-band fiber Fabry-Perot filter for suppression of longitudinal ring modes and an optical isolator for preventing interetalon interactions between the tandem fiber Fabry-Perot filters. Selective positioning of the tandem fiber Fabry-Perot filters, relative to the ring laser's gain medium and output coupler, results in laser intensity noise reduction to the standard quantum limit.