Abstract: A method for locating faults in an optical communication system that includes at least two optical fibers begins by supplying an optical test signal to a first optical fiber. The optical test signal propagates on the first optical fiber in a first direction. A second optical fiber receives the optical test signal via a coupling device. The optical test signal propagates on the second optical fiber in the first direction, reaches a termination point and reflects back on the second optical fiber in a second direction opposite to the first direction. The reflected signal received on the second optical fiber may then be analyzed to determine whether a fault has occurred.

Abstract: An optical transmission system with a mechanism to locate a fault on a transmission line effectively and efficiently to ensure the quality of communication between end stations and repeaters. Repeaters respond to a monitoring control command sent from an end station, returning a monitoring report signal that indicates their current operating status and input/output signal conditions. In the end station, a monitoring report processor identifies a faulty link section of the optical transmission line, if the monitoring report signal indicates a fiber fault. The end station sends a troubleshooting control command to cause a relevant repeater to transmit a probing light pulse signal and a complementary light pulse signal simultaneously in opposite directions. Some of the probing light pulse is reflected back as a result of Rayleigh scattering. The end station locates the fiber fault by analyzing the backscatter, using the complementary light pulse signal for synchronization.

Abstract: Disclosed is a WDM network which has: a lightwave path which connects between clients and each of which is provided with an overhead, and a sub-network which is defined by dividing the WDM network. In this WDM network, the sub-network has a partial lightwave path to go through the sub-network, the overhead has a partial lightwave path supervisory control information region which is terminated at both nodes of the partial lightwave path, and when a fault occurs on a lightwave path, the fault information of partial lightwave path including the position information of fault occurred is added to the partial lightwave path supervisory control information region of the overhead.

Abstract: The present invention relates to a branch line monitoring system and branch line monitoring method comprising a configuration which improves the S/N ratio of measurement information and can be realized inexpensively. This system is provided with optical filters which correspond to optical fiber lines to be monitored as branch lines. These optical filters each have such a cutoff characteristic as to cut of f respective one channel of monitor light but transmit therethrough the remaining monitor light and signal light. When the optical filters having such a cutoff characteristic are provided, each of the optical fiber lines is monitored by use of a plurality of channels of monitor light other than the one cut off by the optical filter provided so as to correspond thereto. Consequently, as compared with the case where one optical fiber line is monitored by its corresponding one channel of monitor light, the S/N ratio of measurement information is improved, whereby highly accurate monitoring is possible.

Abstract: In a transparent fiber-optic communication network with several central systems that are interconnected by optical fibers, to which systems at least one decentralized system is connected via two optical feed fibers, at least one first and at least one second optical fiber are connected to the decentralized optical system by a first and a second optical feed fiber in an optically transparent manner through a monitoring equipment of the central system.

Abstract: A network is protected against interruption of service while one or more faulty switches or optical fiber transmission lines are repaired or replaced, by an interconnecting configuration of small N×N optical input/output switches, where N is 2 or greater than 2. The switches are configured among protection and working transmission lines. The small number of fibers for each switch improves repair and installation connection reliability and permits configurations that flexibly meet differing requirements. Also the fault is monitored with a fault check signal.

Abstract: The present invention provides a method of monitoring a transmission fiber including the steps of transmitting a monitor signal on the transmission fiber in a direction opposite to the propagation of traffic signals on the transmission fiber, at an optical amplifier connected to the transmission fiber detecting the monitor signal and automatically shutting down the optical amplifier in response to a predetermined change in the detected monitor signal. The invention facilitates a faster shut down of amplifiers when a fault occurs than is currently available because it shuts down the amplifier feeding directly into the area of broken fiber first rather than last as in conventional communication systems.

Abstract: An inspection apparatus for an optical transmission device comprises a coupling means to be optically coupled to an optical transmission device, a selecting means for optically separating and selecting an optical signal of a specific wavelength from a plurality of optical signals having different wavelengths transmitted from the optical transmission device, a converting means for converting the selected optical signal into an electrical signal, and a displaying means for displaying the selected wavelength according to the electrical signal. The wavelength of a transmission signal from the optical transmission device can be easily and visually checked by selecting a signal of a specific wavelength out of a plurality of signals having different wavelengths transmitted from the transmission device, and by displaying the selected wavelength by the displaying means.

Abstract: A method for designing an optical system is disclosed. The optical system launches optical signals modulated with data into a fiber link having a property of inducing nonlinear distortion of the optical signals as a function of signal power of the optical signals and distance traversed in the fiber link. A Q-factor curve for the fiber link is determined as a function of the signal power. A signal power is preselected based on the Q-factor curve. The preselected signal power is associated with a set of channels. A coding gain is preselected based on the preselected signal power and a desired channel spacing for the set of channels.