British Telecommunications Public Limited Company

British Telecommunications Corporation

Bt&d Technologies Limited

Jonathan R Armitage

Raman Kashyap

Richard Wyatt

Benjamin J Ainslie

Douglas L Williams

Graeme Douglas Maxwell

Colin A Millar

Stephen A Cassidy

Loudon Thomas Blair

Michael J Robertson

Michael Charles Brierley

Roger Alyn Payne

Fiona MacKenzie

Susan P Craig

Timothy J Whitley

Robert J Campbell

Jennifer F Massicott

Howard John Wickes

Robert John Campbell

Gerard Sherlock

An optical network includes interconnected via an N&times;N WDM router. The nodes are connected to an optical waveguide ring having a duplex structure. A first set of optical waveguides connects the transmitters in the nodes and a second set of optical waveguides connects the receivers in the nodes. The N&times;N wavelength router is connected across the ring between the first set of optical waveguides and the second set of optical waveguides. Each of the nodes is able to communicate with any other of the nodes on a respective wavelength channel via the router.

Meshed optical network

It has been demonstrated that B containing glasses are sensitive to radiation in the band 225-275 nm and, therefore, B,O,glasses are particularly adapted to receive refractive index modulation, e.g., to make reflection gratings. Glasses containing SiO,and B,O,are particularly suitable when the grating is to be localized in the cladding of a fiber. Glasses containing SiO,, GeO,, and B,O,are suitable when the grating is in the path region of a waveguide, e.g., in the core of a fiber.

Photo induced grating in B2O3 containing glass

Boron containing glasses are sensitive to radiation in the band 225-275 nm and therefore, B.sub.2 O.sub.3 glasses are particularly adapted to receive refractive index modulation, e.g., to make reflection gratings. Glasses containing SiO.sub.2 and B.sub.2 O.sub.3 are particularly suitable when the grating is to be localized in the cladding of a fibre. Glasses containing SiO.sub.2, GeO.sub.2 and B.sub.2 O.sub.3 are suitable when the grating is in the path region of a waveguide, e.g., in the core of a fibre.

Photoinduced grating in B.sub.2 O.sub.3 containing glass

A resonant laser device including first and second reflectors defining an optical cavity with given optical resonance characteristics. The laser device including a laser active material in a first optical fiber disposed between the reflectors in the cavity and a second photosensitive optical fiber coupled to the cavity. One of the reflector being a refractive index grating formed in the second fiber such that the laser operates with a selected predetermined wavelength and the laser being tuned to a different wavelength by exposing the second fiber to a second spatially periodic pattern of optical radiation such that the second pattern becomes recorded in the second optical fiber.

Laser device tuned by forming a refractive index grating in optical fiber

Laser

A high power monomode laser arrangement is able to manipulate the output from a high power laser diode array pump source using a computer-generated hologram to launch a high proportion of the pump source light into a multimode fibre portion including input reflector. A monomode fibre portion with the same fundamental-mode spot size as the multimode fibre portion is optically coupled to the multimode fibre portion and includes a reflector which reflects only the fundamental mode of the multimode and monomode fibre portions. The fundamental mode reflection forced by the monomode fibre portion provides the feedback necessary to force predominantly fundamental mode oscillation which enables stimulated emission in only the fundamental mode.

Two-stage mono-mode optical fibre laser

Filter with preselected attenuation/wavelength characteristic

Optical waveguide amplifier

A high power monomode laser arrangement is able to manipulate the output from a high power laser diode array pump source 3 using a computer-generated hologram 4 to launch a high proportion of the pump source light into a multimode fiber portion including in input reflector 6. A monomode fiber portion 2 with the same fundamental-mode spot size as the multimode fiber portion 1 is optically coupled to the multimode fiber portion and includes a reflector 5 which reflects only the fundamental mode of the multimode and monomode fiber portions. The fundamental mode reflection forced by the monomode fiber portion 2 provides the feedback necessary to force predominantly fundamental mode oscillation which enables stimulated emission in only the fundamental mode.

Method of forming a refractive index grating in an optical waveguide

A laser amplifier having an improved pump efficiency for a given pump power comprises a pump source (46) longitudinally coupled at a plurality of coupling points (47, 48, 49) to an optical fibre (41). By thus coupling the pump power into the fibre (41), a fraction of the pump power is applied to the fibre (41) at each of the coupling points (47, 48, 49). A significant improvement in pump efficiency may be achieved in this way.

Laser amplifier

Laser systems

An optical fibre for use in fibre lasers has the lasing additive eg Er.sup.3+, concentrated in center of the core. Preferably the core has an inner region which contains the additive and an outer region which is dopant free. The concentration of the dopant reduces the pump threshold for a laser and improves the gain performance for a given pump power. The fibre is conveniently made in MCVD. The use of Al.sub.2 O.sub.3 in the inner zone appears to reduce loss of dopant during tube collapse.

Optical fibre with fluorescent additive

Growing community of inventors

Ipswich, United Kingdom

Jonathan R Armitage