Abstract:
An optical device comprises an optical waveguide, such as a single mode optical fiber (11), underlying a first layer (2) of material, such as a thin film, which has a refractive index higher than the refractive index of the waveguide (11) and which forms a planar waveguide capable of supporting and guiding at least one propagation mode of a higher order than, but matching the phase velocity of, the propagation mode or modes in the underlying waveguide. A reflection diffraction grating (4) is provided on or adjacent to the surface of the first layer (2) remote from the waveguide (11). The arrangement is such that an optical signal which is coupled from the waveguide (11) into the first layer (2) is reflected by the reflection diffraction grating (4) and is coupled back into the waveguide.
Abstract:
An optical coupler device comprises a waveguide structure underlying a first layer of material which has a refractive index higher than the effective refractive index of the waveguide structure and which is capable of supporting propagation modes of a higher order than, but matching the phase velocity of, the propagation mode or modes in the underlying waveguide structure, said layer thereby forming a wave guiding structure.
Abstract:
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.
Abstract:
A laser has a resonant cavity defined by a pair of mirrors (6, 10) butted to respective ends of a 3 m fluorozirconate optical fibre (14). The fibre (14) has a .DELTA.n of 0.014 and a cut-off wavelength of around 790 nm and is doped to about 500 ppm (weight) with erbium ions. An optical pump source (12) provides a pump signal at 971 nm which excites the erbium ions into the .sup.4 S.sub.3/2 energy level to provide lasing at about 546 nm. The laser may alternatively be pumped by a pump signal in the band 791 nm to 812 nm, preferably 801 nm. The pump source is preferably a high power semiconductor laser (16).
Abstract:
The invention relates to laser systems of the type comprising optical fiber amplifiers. A laser system comprises a first laser 1 and a second laser 2. The second laser 2 is pumped at a first wavelength .lambda..sub.1 and caused to lase at a second wavelength .lambda..sub.2. The first laser 1 has absorption bands .lambda..sub.1 and .lambda..sub.2. The output .lambda..sub.2 of laser 2 and the remnant pump at .lambda..sub.1 are coupled and both are used to pump the first laser 1, thus causing laser 1 to lase at a third wavelength .lambda..sub.3.
Abstract:
Features of the endface of a dielectric member are assessed by means of a reflected diffraction pattern.A plurality of light beams 6, 7 which intersect in a region containing the endface 8 can be used to generate a diffraction pattern 10 which subtends an angle of at least 180.degree. at the endface 8. Such a diffraction pattern 10 contains information about the endface 8 and may be used, in particular, to locate the plane in which the endface 8 lies.Embodiments of the invention find particular application in the measurement of endface angles of optical fibres.
Abstract:
A laser has a resonant cavity defined by a pair of mirrors (6, 10) butted to respective ends of a 3 m fluorozirconate optical fibre (14). The fibre (14) has a .DELTA.n of 0.014 and a cut-off wavelength of around 790 nm and is doped to about 500 ppm (weight) with erbium ions. An optical pump source (12 ) provides a pump signal at 971 nm which excites the erbium ions into the .sup.4 S.sub.3/2 energy level to provide lasing at about 546 nm. The laser may alternatively be pumped by a pump signal in the band 791 nm to 812 nm, preferably 801 nm. The pump source is preferably a high power semiconductor laser (16).
Abstract:
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.
Abstract:
Features of the endface of a dielectric member are assessed by means of a reflected diffraction pattern.A plurality of light beams 6, 7 which intersect in a region containing the endface 8 can be used to generate a diffraction pattern 10 which subtends an angle of at least 180.degree. at the endface 8. Such a diffraction pattern 10 contains information about the endface 8 and may be used, in particular, to locate the plane in which the endface 8 lies.Embodiments of the invention find particular application in the measurement of endface angles of optical fibres.
Abstract:
An optical communication system includes a head-end station, an optical fibre network and a number or sensors and actuators connected via the network to the head-end station. The head-end station includes one or more broadband sources and is arranged to output a broadband signal onto the network. The sensors modulate the broadband signal received from the head-end station and return narrowband components of the signal via the network to the head-end. There the different narrowband components are detected, for example using a demultiplexer and the resulting signals processed by control electronics. The head-end station also includes an optical circuit arranged to split a signal from a broadband source into different narrowband components. Electro-optic modulators (FOM) modulate the different narrowband components and the resulting narrowband signals are output onto the fibre network and transmitted to the actuators. The electro-optic modulators (FOM) are operated by the control electronics.