Nortel Networks Corporation

Andrew L Reynolds

Kevin J Cordina

Andrew V Maroney

Vincent Handerek

Gordon D Henshall

Sotiris Emil Kanellopoulos

Kostas Tastavridis

Tudur A Hughes

An optical add drop component uses wavelength-selective reflectors which are switchable between first and second positions. This enables an add or drop function to be selectively applied. When the add or drop function is not required, there is no signal attenuation or degradation of an input signal. When an add or drop function is required, selected frequencies are added or dropped and other signal frequencies can pass through the wavelength-selective reflector. No demultiplexing operation is required.

Optical switchable component

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

Compensating for polarization mode dispersion in a birefringent optical transmission fibre is achieved by controlling the birefringence of the fibre. The difference in group velocity of the orthogonal polarization states of an optical signal transmitted over the fibre is monitored to generate an error signal representing the difference. The birefringence of the fibre is adjusted accordingly to minimize the difference and thereby provide dynamic compensation. Birefringence control may be achieved by a non-linear fibre grating written into the fibre to impose a differential time delay. The fibre may be a side hole fibre (SHF), a holey fibre (HF), a photonic crystal fibre (PCF), or any other suitable microstructure fibre. The fibre may have stressing rods, may be tapered along its length and may be controlled electrically, mechanically, acoustically or thermally by spaced heating elements.

Compensating for polarisation mode dispersion in optical transmission fibers

A photonic bandgap device has a lattice structure, with a waveguide formed by a mesh of defects in the lattice, the defects being located discontinuously, but sufficiently close to each other to provide coupling between overlapping evanescent defect modes. By changing shape and configuration of the mesh and varying the types of defects, it is easier to control the width and position of the transmission band, in wavelength terms, compared to a waveguide formed only from a planar defect, i.e. a single line of defects. Multiplexers, demultiplexers, filters, switches, combiners, and splitters may be created. Many devices and different types of devices can be integrated onto the same crystal lattice, with far greater compactness than planar waveguide technology. The mesh can have a periodic structure of lines of defects, or periodic spacing between defects to reduce loss.

Photonic bandgap device using coupled defects

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.

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Bearsden, United Kingdom

Andrew L Reynolds