Abstract: A micro-structured optical fiber precursor 1 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 2 of the precursor 1. The effect of the fiber fuse is to consume the core 2 along the whole length of the fiber or to consume periodically spaced lengths of core 2 along the whole length of the fiber.

Abstract: An optical component comprising a plurality of optical input ports and a plurality of optical output ports. A polymer amplifying medium is provided within the component which is pumped by a pump source for exciting the polymer amplifying medium. Signals passing through the optical component are routed through the polymer amplifying medium. This, provides amplification using a polymer amplifying medium which is integrated into the structure of the component. This amplification can then compensate for the loss resulting from the other functions of the component.

Abstract: A power control arrangement for an optical transmission system involves detecting optical power upstream of a delay element, adjusting a perchannel optical power in the optical path downstream of the delay element to maintain the optical power constant. Such a feed forward arrangement enables power transients to be detected in time for pre-emptive control to suppress transients which are too fast to be suppressed otherwise by conventional control of optical amplifiers. This enables a reduction in power margins, and prevents damage to sensitive receivers for example. Such controllers can be distributed through networks and provided at interfaces with other optical networks to enable third party wavelengths to be carried with less risk of damaging transients propagating through the 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.

Abstract: An optical amplifier is constituted by a planar waveguide having an optical core intersected by a transverse trench occupied by a polymeric optically amplifying medium. An optical pump for the amplifier is provided by a laser diode positioned to direct its emission, transversely with respect to the waveguide axis, into the polymer.

Abstract: An orientation switchable optical fiber 1 has an elongate body 8 with two ends N, F. The body 8 is twisted intermediate the two ends at M and has a central core region 14 in which light carried by the fiber is confined. Passive means in the form of air channels 6 extend substantially from one end N to substantially the other end F of the body 8. The passive means 6 promotes orientation of light in at least one first transverse axis A of the body 8. Active means in the form of thermally stressable rods 10 extend substantially from the location of the twist M to substantially the other end F of the body 8. The active means 10 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 8.

Abstract: A micro-structured optical fibre precursor 1 is made by size reducing a multiple core optical fibre having solid multiple cores or a multiple core optical fibre preform O having multiple solid core preforms C. A fibre fuse is induced in at least one of the cores 2 of the precursor 1. The effect of the fibre fuse is to consume the core 2 along the whole length of the fibre or to consume periodically spaced lengths of core 2 along the whole length of the fibre.

Abstract: An orientation switchable optical fibre 1 has an elongate body 8 with two ends N, F. The body 8 is twisted intermediate the two ends at M and has a central core region 14 in which light carried by the fibre is confined. Passive means in the form of air channels 6 extend substantially from one end N to substantially the other end F of the body 8. The passive means 6 promotes orientation of light in at least one first transverse axis A of the body 8. Active means in the form of thermally stressable rods 10 extend substantially from the location of the twist M to substantially the other end F of the body 8. The active means 10 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 8.

Abstract: An optical component comprising a plurality of optical input ports and a plurality of optical output ports. A polymer amplifying medium is provided within the component which is pumped by a pump source for exciting the polymer amplifying medium. Signals passing through the optical component are routed through the polymer amplifying medium This, provides amplification using a polymer amplifying medium which is integrated into the structure of the component. This amplification can then compensate for the loss resulting from the other functions of the component.

Abstract: An optical fiber amplifier or laser comprises an optical housing having a diffusive reflective inner surface and at least one opening for receiving pump light. An optical fiber having a doped core is at least partially contained within the optical housing. The optical fiber can be pumped by an optical source without the need for any complex or expensive optical couplers. Lateral illumination of the fiber core with pump light enables many fibers to be pumped by the same pump source, so that a separate dedicated coupler is no longer required to couple the pump light into each optical cable.

Abstract: 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.

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.

Abstract: 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.

Abstract: An intermediate optical amplifier stage of an optical amplifier having cascaded amplifier stages includes an optical circulator having a first port forwardly coupled with a second port which is forwardly coupled with a third port, wherein the second port is optically coupled with an orthogonal polarisation state converting reflector via a length of optically pumped optically amplifying optical fibre. The orthogonal polarisation state converting reflector may be constituted by the series combination of a collimating lens, a Faraday rotator that provides a &pgr;/4 plane of polarisation rotation in respect of a single transit of light through the rotator, and a mirror.

Abstract: An optical amplifier comprises an erbium doped optical fiber (2) and a plurality of optical filtration elements (12) provided at respective positions along the fiber. The wavelength response of each of the optical filtration elements (12) is selected in dependence on the gain response of the optical fiber at the respective position along the fiber, thereby flattening the gain of the amplifier with respect to wavelength over a predetermined bandwidth. This bandwidth may include both the C and L bands.