Abstract: A non-blocking optical switch has a non-dilated architecture wherein dual mode input waveguides are connected to first and second inputs of mode selective couplers through mode conversion devices. Switching is effected by signals from a processing unit applied to a mode converter to convert the signal to be switched from a fundamental mode to a higher order mode. The mode selective coupler then couples the signal to one of the outputs thereof, whereas fundamental mode signals pass through to the other output thereof. An array of rows (layers) and columns of such elements make it possible to switch any incoming signal to be switched to any of a plurality of outputs after reconversion to the fundamental mode.

Abstract: An optical fiber sensing system (20) applies spectral analysis to time-varying disturbances in the output optical power from a Sagnac interferometer. In particular, harmonically related null frequencies in the spectrum (402) of the output optical power from the Sagnac interferometer are used to uniquely determine the location of a disturbance along a fiber cable (50). An optical signal having relatively high coherence is fed into a splitter (25), which creates a pair of subsignals that are sent in opposite directions around a common optical path. The splitter is effective to recombine the subsignals after they have traveled around the common path. The location of the disturbance is determined by the formula: ##EQU1## z is the distance between the locations of the disturbance and the splitter;2L is the length of the common path;c is the speed of light;n.sub.e is the effective index of refraction of the optical fiber path experienced by the subsignals; and.OMEGA..sub.

Abstract: An optical integrated circuit is used to simultaneously test both the transmit fiber and the receive fiber in a fiber optic pair which extends between a telephone central office and a subscriber's site. By testing both fibers simultaneously testing time is cut in half without the loss of any important information, as fibers are replaced in pairs. In addition, the cost of test equipment is reduced considerably, as the expensive portions of the test equipment can be used for twice as many optical circuits as was heretofore possible. Finally, there are half as many connections needed between the optical switch and the optical integrated circuits built in accordance with the present invention, thereby simplifying their interconnections, and eliminating the extra cost in optical ports and interconnecting fiber.

Abstract: An improved fiber optic cable connector is provided that exhibits a consistent return loss rating of 60 dB or better. The connector comprises matable connector housings that terminate the ends of respective optical cables to be joined. Within each housing, the optical fiber of the respective cable is secured within a ceramic ferrule that extends axially of the connector. The endface of each optical fiber is exposed at the end of its respective ferrule. The ends of the ferrules are ground and polished in such a way that the endfaces of the optical fibers exhibit a planar undercut with respect to the lip of the axial passageway in which the fibers are secured. When the ferrules are brought and pressed together end-to-end as the connectors are mated, the material of each ferrule compresses until the endfaces of the optical fibers engage each other with near null pressure.

Abstract: An improved fiber optic cable connector is provided that exhibits a consistent return loss rating of 60 dB or better. The connector comprises matable connector housings that terminate the ends of respective optical cables to be joined. Within each housing, the optical fiber of the respective cable is secured within a ceramic ferrule that extends axially of the connector. The endface of each optical fiber is exposed at the end of its respective ferrule. The ends of the ferrules are ground and polished in such a way that the endfaces of the optical fibers exhibit a planar undercut with respect to the lip of the axial passageway in which the fibers are secured. When the ferrules are brought and pressed together end-to-end as the connectors are mated, the material of each ferrule compresses until the endfaces of the optical fibers engage each other with near null pressure.

Abstract: An optical integrated circuit (OIC) 10 and an optical fiber array 20 are joined using index matching material, and mounted on a planar bridging structure 30 to form a device which can be readily connected to other devices using conventional optical connectors. The OIC and the fiber array comprise a silicon substrates 100, 200 having bottom surfaces that include reference areas 14, 24, and top sides that include a number of optical paths 16, 50. These paths are positioned above each reference area by an exact distance. Additionally, the bottom sides of the OIC and the fiber array include alignment features 13, 23 which are etched into their substrates and bear a predetermined horizontal relation to the optical paths. The planar bridging structure also includes a reference surface 34 that interfaces the reference surfaces of the OIC and the fiber array to assure that the optical paths are in vertical alignment. The resulting device achieves excellent alignment (i.e., less than 0.

Abstract: An optical fiber communication system according to the invention comprises an optical fiber filter that can be manufactured at low cost and that can be conveniently incorporated into the system, substantially like a conventional fiber jumper. The filter comprises a length L of axially uniform optical fiber selected to have substantially no loss (e.g., <1 dB) at a wavelength .lambda..sub.1, and to have relatively high loss (e.g., >20 dB) at a wavelength .lambda..sub.2. The length L will typically be less than 100 m. In one embodiment the optical fiber is a single mode optical fiber at .lambda..sub.1 (e.g., 1.3 .mu.m) that does not have a guided mode at .lambda..sub.2 (e.g., 1.55 .mu.m). In another embodiment the fiber contains a dopant that does substantially not absorb radiation of wavelength .lambda..sub.1, but substantially absorbs at .lambda..sub.2. In the second embodiment, .lambda..sub.1 can be greater than .lambda..sub.2.