摘要:
An all-optical fibre Sagnac antiresonant interferometer (2) is formed from an optical fibre having a non-linear refractive index. The coupler (8) is a dichroic coupler coupling equal portions of a cw optical signal at 1.53 .mu.m from laser (16) to ports (14 and 16) and all of a pulsed optical signal from laser (20 ) to port (14). The intensity of the pulsed optical signal is sufficient to provide a relative phase shift in the counter propagating 1.53 .mu.m signals. The loop (6) is longer than the inverse of the absolute difference in group delays of the cw and pulsed optical so causing a square optical pulse at 1.53 .mu.m to be switched to port (12) of the coupler.
摘要:
A sheath for optical fibres comprises a compound sheath having an inner sheath of high modulus and density, and an outer sheath layer of low density material. The outer sheath layer may be of foamed polyethylene and the inner sheath of polypropylene, both conveniently formed by extrusion. Such fibre members are installed by first installing a conduit having one or more bores and subsequently inserting the flexible, lightweight optical fibre members containing the optical fibres into the bores. The optical fibre members are propelled by employing the fluid drag of air, or another suitable gas, passed at high velocity through the bores.
摘要:
A method of mounting a saw device comprising applying metallized areas to the surface of an appropriate substrate, attaching conductive leads to the metallized areas, locating the said surface adjacent a selected area of another substrate so that said leads contact conductive regions on the second substrate and attaching said leads to said conductive regions on the second substrate so that the first substrate is supported on the leads and the conductive regions.
摘要:
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.
摘要:
A selective filtering device for use in optical communications systems takes the form of a transversely coupled Fabry-Perot interferometer. One described embodiment comprises a first length of monomode optical fiber transversely coupled to a second fiber in a coupling region. One end of each fiber at opposite respective ends of the coupling region is provided with a suitable highly reflective surface, or example, an evaporated gold/aluminum deposit. In operation, a light input may be modified by the resonant cavity behavior of the Fabry-Perot cavity formed between the mirrored ends to provide filtered or enhanced outputs. The outputs may be further modified by alternative or additional light input via the ends of the fibers.
摘要:
An omnidirectional antenna comprises a ring-shaped subreflector surrounding an omnidirectional feed and a ring-shaped main reflector for redirecting radiation from the subsidiary reflector to the target zone. The feed has a focal ring and a hollow centre to accommodate supports, feeders etc which facilitates stacking of antennas.
摘要:
A submarine telecommunications cable includes a plurality of optical fibers in the bore of an orientated plastics strength member. The cable may have an average density of 0.9 to 4.0 and preferably a neutral buoyancy whereby most of the weight of the cable is carried by the sea. This reduces tension in the cable during laying. The bore of a submarine cable is filled with a solid elastomeric embedding medium which occupies the space between the fibers. This gives a void-free structure which assumes ambient pressure. The strength member may be made from orientated polyethylene. The cable is preferably buried in the sea bed during use.