Abstract: A system for checking the correct operation of a wavelength filter comprising a wavelength filter comprising a first selectively reflective element (SRE) for reflecting a first signal of a first wavelength and a second SRE for reflecting a second signal of a different wavelength. The system also detects the second signal reflected by the second selectively reflective element.

Abstract: A system for individually controlling the chromatic dispersion of one or more wavelength division multiplexed (WDM) optical signals, chromatic dispersion is compensated a plurality if individually controllable differential optical delay elements. An example of a suitable differential optical delay element is a tunable fiber Bragg grating filter whose spectral response varies along the length of the grating, i.e. is chirped in a non-linear fashion. The system may, in addition, comprise one or more second individually controllable optical delay elements arranged so as to compensate for any unwanted delays across the wavelength band of a signal introduced by a first delay element. Optical circulators may be used to route signals into and between the pluralities of differential optical delay elements. This system has the advantage of providing a compact multi-channel selective differential delay suitable for compensating for chromatic dispersion in a WDM optical communications network.

Abstract: An optical switching arrangement, e.g. an add-drop multiplexer or switch, for receiving an input signal comprising a plurality of input wavelength encoded optical channels. The arrangement includes a selector for selecting from the plurality of input optical channels for forming a plurality of output signals comprising selected ones of the plurality of input optical channels. A combination of input optical channels in any one of the plurality of output signals is different from a combination of input optical channels in the input signal. The selector comprises a plurality of selective reflectors for selectively reflecting optical channels selected from the plurality of input optical channels. The plurality of selective reflectors are arranged to selectively reflect each of the input optical channels selected for forming the plurality of output signals.

Abstract: An optical communications system for communication of a plurality of wavelength multiplexed channels. The communications system comprises a node. The node comprises a plurality of add-drop multiplexers (ADM), one per channel. Each ADM comprises a tributary. The ADMs are interconnected by the tributaries.

Abstract: A method for upgrading an-optical communications system in which the system comprises a plurality of nodes linked by one or more optical paths. Each path for the communication of traffic includes a single optical channel. Each node comprises add/drop multiplexers (ADM) for adding and dropping signals in electrical form, and conversion circuitry for converting between electrical and optical form signals output by the ADM for transmission via a first one of the optical paths, and for converting signals received via a second one of the optical paths for input to the ADM.

Abstract: A system for individually controlling the power levels of a plurality of wavelength division multiplexed (WDM) optical signals in a single optical guide comprising a first plurality of individually controllable optical attenuators. An example of a suitable optical attenuator is a tunable fiber Bragg grating filter whose reflectivity characteristic varies with wavelength over an active region thereof. By tuning the filter, it is possible to control the reflectivity at a particular wavelength in the active region. The system may, in addition, comprise a second plurality of optical attenuators arranged so as to compensate for any power level distortion introduced by the first plurality. Optical circulators may be used to route signals into and between the pluralities of optical attenuators.

Abstract: A photonics system comprising an optical circulator, comprising a plurality of ports; a first port arranged to receive a plurality of spatially separate optical signals each comprising a plurality of wavelengths; the optical circulator arranged to pass the plurality of optical signals to a second port so as to produce them as spatially separate signals; a plurality of optical wavelength filters arranged at the second port, in which each of the plurality of optical wavelength filters is arranged to align with a different one of the plurality of optical signals at the second port, each of the plurality of optical wavelength filters for selectively reflecting a selection of the plurality of wavelengths comprised in the respective optical signal and selectively passing others of the plurality of wavelengths.

Abstract: A relatively large scale low cost method of fabricating optical devices with associated coupling lenses comprises the following steps:(a) producing in one surface of a substrate (1) of suitable material(s) a predetermined array of planar diffused lenses (4);(b) forming or otherwise producing on the opposite surface of the substrate (1) remote from the planar lenses (4) but in predetermined positional relationship to the lenses in the general planar direction of the substrate an array or pattern of metallic bonding pads or other registration means co-operable with corresponding pads or other means provided on a multiplicity of optical devices (10) for the accurate registration of such devices relative to the optical lenses; and,(c) dividing the substrate (1) into a multiplicity of parts each of which comprises an optical device (10) having an associated planar lens (4).

Abstract: The electronic component includes a mounting substrate having a surface provided with a plurality of spaced contact pads. A semiconductor chip is mounted on the substrate and includes at least one active element in the form of a photodiode on a substrate of light transmissive material. The active element has a metallized contact region and the semiconductor chip has a plurality of projecting metallized contact regions which are each electrically conductively bonded to a different one of the spaced contact pads of the mounting substrate. The photodiode may be a PIN diode and the semiconductor chips may be an integrated circuit to which the PIN diode is connected thereby providing an optical receiver equivalent to a PIN receiver.

Abstract: A system for multiplexed transmission of different wavelengths of light comprises an array of at least two light sources whose images are formed on the end of an optical fibre. The images have displaced spectra so that a different part of the spectrum of each light source is imaged on to the end of the optical fibre and each part is transmitted by the optical fibre. The images themselves may be displaced by displacing the light sources. A number of such arrays having light sources with emission spectra centered on different wavelengths may be used to increase the number of multiplexed transmission channels.

Abstract: The invention relates to a monolithic light detector or generator integratd with an amplifier. The amplifier includes an F.E.T. comprising a substrate on which are formed source and drain contact layers separated by a groove. The gate layer is formed in the groove bridging the source and drain layers, and the optical system comprises additional layers formed on the substrate or formed on top of the gate layer with suitable conductive connections between the two.

Abstract: In a semi-conductor laser of buried active laser layer type, the laser layer is located between a layer of n-type material and a layer of p-type material, the sides of the active laser layer and at least a portion of the n-type layer and the p-type layer being covered with a plurality of thin layers with a doping sequence such that a large number of p-n junctions are included in the plurality of thin layers.

Abstract: An optical fibre is sealed into a light emitting diode package by initially positioning the optical fibre above the L.E.D. and then melting a low melting point substance round the fibre and an upper support member, maneuvering the fibre until a maximum output is obtained and then allowing the low melting point substance to solidify while still holding the fibre in the optimum position.