Abstract: Methods and apparatus for detecting degradation of a fiber optic connector. In a preferred embodiment, the method includes transmitting a optical pulse in a first direction along the fiber optic cable such that a first portion of the optical pulse is either absorbed or reflected by the degradation. The method also includes determining the degradation's location within at most two connectors of the cable based on the first portion of the optical pulse. If the at most two connectors is two connectors then the method includes transmitting a second optical pulse in a second direction along the cable so that a portion of the second optical pulse is either absorbed or reflected by the degradation. A determination is made of the location of the degradation within one of the two connectors based on the first portion and the second portion of the optical pulses.

Abstract: A method for detecting a connector disengagement of an optical fiber amplifier and a transmission optical fiber connected thereto, the optical fiber amplifier including a doped optical fiber and a pumping light source, and a transmission optical fiber including at least one connecting portion connected to an output of the optical fiber amplifier, includes the steps of: measuring a reflection from the transmission optical fiber to the optical fiber amplifier; and comparing the reflection to an allowable range between a first threshold that is greater than a predetermined reflection in the absence of a connector disengagement, and a second threshold that is smaller than the predetermined reflection in the absence of a connector disengagement; determining that there is no connector disengagement when the measured reflection is within the allowable range; and determining that there is a connector disengagement otherwise.

Abstract: Signal reflection mitigation in fiber-optic networks. Signal reflections are mitigated using near-end echo cancellation, threshold adjustment and/or error correction code. Signal reflections in a receive signal that are caused by near-end connectors may be mitigated using an echo cancellation signal. Signal reflections caused by other discontinuities on a fiber-optic network may be mitigated by using error correction code. Also, an average value of a reflected signal maybe detected and used to set an adjusted threshold value to interpret logical values of an electronic or optical signal.

Abstract: The detection light reflection function is given to PLC type LD, PD or LD/PD modules having light guides and optoelectronic chips (LD, LED, PD or APD) by forming a grating on the light guides which selectively reflects only the detection light.

Abstract: A system for quickly and reliably detecting a failed structure includes a signal source, a cable attached to the structure, an anti-slip cable anchor, a signal detector, and user indicator. When the structure fails, the cable attached to the structure is also broken. The user indicator is operable to display the status of the cable. The cable breaks due to exceeding the elastic modulus of the cable, caused by elongation of the distance between two fixed points caused by the failing structure. Electric power must be provided to each signal source, signal detector and user indicator.

Abstract: A technique for performance-monitoring of a standard SONET signal involves first converting the optical signal to an electrical signal, removing in the framing signal time slot the framing signal for leaving only the framing signal noise in such time slot, and separating the framing signal noise from the data signal for viewing as a measure of the quality of the SONET signal.

Abstract: The present invention provides methods, apparatus and systems for protecting connections between optical cross-connect switches and client equipment. A connection failure is detected, signaled, and a switch made by the client equipment and the optical cross-connect switch to a protection connection between them so as to minimize service interruption. An out-of-band channel or an in-band channel can be used to signal the connection failure.

Abstract: Fiber-optic communications systems are provided for optical communications networks. Fiber-optic communications links may be provided that use spans of transmission fiber to carry optical data signals on wavelength-division-multiplexing channels at different wavelengths. Raman pump light may be used to provide Raman amplification for the optical data signals. The Raman pump light may be used to make measurements on the spans of transmission fiber. Raman pump light may be modulated to make optical time domain reflectometry measurements and measurements of the Raman gain coefficient in the fiber. Information on the measurements made using the Raman pump light may be used to control the Raman pump light during operation of the communications link and may be provided to a network management system.

Abstract: A method and apparatus is provided for using optical time-domain reflectometry (OTDR) with a WDM transmission system that includes a plurality of terminals interconnected by at least two pairs of unidirectional optical transmission paths each of which has at least one repeater therein. The method begins by transmitting an optical probe signal from a first OTDR unit associated with a first terminal into the repeater over a first optical path in a first of the at least two pairs of unidirectional optical transmission paths. The first OTDR unit receives a first returned OTDR signal over a second optical path in the first optical path pair. The first OTDR signal contains status information concerning the first optical path in the first optical path pair. The optical probe signal from the first optical path in the first optical path pair is coupled to a second optical path in the second optical path pair.

Abstract: An automatic optical power management system for use with an optical communications system includes a light source residing in a first circuit pack and adapted to emit light at a nominal power level only absent receipt of an indicator signifying a loss of signal resulting from a fiber discontinuity relating to the first optical fiber, wherein the nominal power level is of sufficient magnitude to violate laser safety guidelines in the event of the fiber discontinuity. A redundant detection system includes a first optical detector residing in the first circuit pack, and a second optical detector residing in a second circuit pack that is optically adjacent to the first circuit. A redundant response system communicates an indicator signifying loss of signal from the first and second optical detectors to the light source upon detection of loss of signal by either detector.

Abstract: A method for identifying faults in a branched optical network having a central office optically connected to a plurality of optical network units by a plurality of optical paths. The method involves transmitting an optical signal from the central office to the optical network units reflecting a portion of the transmitted optical signal back to the central office. This reflected signal is then used to determine whether a fault exists in the branched optical network.

Abstract: A method of routing of signals through an optical network involves determining a route through the network for which the power level within each branch of the network along the route is below a threshold power level which is a function of the fiber characteristics of the branch. This threshold power is the power below which a fiber fuse can not be initiated. This method enables power levels within a network to be controlled such that the threshold power is not exceeded, and a fiber fuse will not be initiated. The invention provides a network controller for carrying out this method.