Nortel Networks Corporation

Andrew V Maroney

Kevin J Cordina

Vincent Handerek

Jowan Masum-Thomas

Andrew L Reynolds

Christopher R Fludger

Richard Thomas

Kostas Tastavridis

Daria Crippa

A micro-structured optical fiber precursor is made by size reducing a multiple core optical fiber having solid multiple cores or a multiple core optical fiber preform O having multiple solid core preforms C. A fiber fuse is induced in at least one of the cores of the precursor . The effect of the fiber fuse is to consume the core along the whole length of the fiber or to consume periodically spaced lengths of core along the whole length of the fiber.

Micro-structured optical fibers

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.

Optical fibre monitoring system

An optical amplification system has an active fibre section having an optical fibre and containment means containing light of a specific wavelength within the active fibre section. The specific wavelength of light is the result of the spontaneous transition of photons. The contained photons stimulate further photons emissions, which depopulates energy levels involved in the amplification process.

Optical fibre amplifiers

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.

Fiber fuse protection

In a first aspect, a Raman amplifier is pumped using pumps just above and below the fiber water peak. This enables lower power pumps to be used, as the high attenuation is avoided. In a second aspect, a first pump provides a signal having a first wavelength and a first power, and a second pump source provides a plurality of signals, each having a power lower than the first power and a wavelength in a range approximately one Stokes shift higher than the first wavelength. In this way, the second pump source signals are amplified by the Raman effect by the first pump source signal, and the amplified second pump source signals cause signal amplification. The amplified second pump source signals can then include wavelengths above and below the water peak.

Raman amplification

An orientation switchable optical fiber has an elongate body with two ends N, F. The body is twisted intermediate the two ends at M and has a central core region in which light carried by the fiber is confined. Passive means in the form of air channels extend substantially from one end N to substantially the other end F of the body . The passive means promotes orientation of light in at least one first transverse axis A of the body . Active means in the form of thermally stressable rods extend substantially from the location of the twist M to substantially the other end F of the body . The active means is switchable between an off state in which it is ineffective and an on state in which it is effective to promote orientation of light in at least one second transverse axis B of the body . In the off state of the active means light remains confined in the at least one first axis A along the length of the body and in the on state of the active means light transits as on passing the location of the twist M from the first axis A to the at least one second axis B.

Orientation switchable optical fibres

An optical component for halting the propagation of a fiber fuse through a transmission fiber has a threshold power level which is greater than the transmission power level of the system for that transmission fiber. The component comprises a fiber which is selected such that it is unable to propagate a fiber fuse when the power is below the threshold power level. The component is designed by selecting values of the core diameter and the higher mode cutoff wavelength of the fiber making up the component. If power surges are experienced which exceed the transmission power level (the transmission fiber being designed to operate at the transmission power levels without fiber fuses being initiated) then the component provide a safety margin.

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South Woodford, United Kingdom

Andrew V Maroney