Abstract: A Doppler compensation method is used for radio transmission between a mobile body possibly but not exclusively a train and some base station, both mobile body and base station comprise respectively a transceiver connected to an antenna for the radio transmission. The method comprises the step of determining the direction of motion of the mobile body with respect to the active base station i.e. the base station to which a radio transmission link is just built. The method is then followed by the step to apply a constant Doppler compensation corresponding to the cancellation of the Doppler effect for a mobile body moving in the same direction at predefined limiting speed of motion (vlimit) at which a quality threshold is reached with the used radio transmission technology in the case without a Doppler compensation.

Abstract: A Doppler compensation method is used for radio transmission between a mobile body possibly but not exclusively a train and some base station, both mobile body and base station comprise respectively a transceiver connected to an antenna for the radio transmission. The method comprises the step of determining the direction of motion of the mobile body with respect to the active base station i.e. the base station to which a radio transmission link is just built. The method is then followed by the step to apply a constant Doppler compensation corresponding to the cancellation of the Doppler effect for a mobile body moving in the same direction at predefined limiting speed of motion (vlimit) at which a quality threshold is reached with the used radio transmission technology in the case without a Doppler compensation.

Abstract: The goal of the invention is to keep the delay of a communication signal between a moving vehicle (mobile body) and a fixed base station constant. This is achieved by a Doppler compensation method for data to be transmitted within frames via radio transmission between a mobile body and some base station, both mobile body and base station comprise respectively a transceiver connected to an antenna for the radio transmission. The method comprises the step of determining the Doppler effect acting on the frames when transmitted as a signal through that radio transmission for a given speed and direction of motion of the mobile body with respect to the base station. It is then followed by the step to apply by the transceiver some sampling procedure comprising an allocation of different time delays to the signal, the different time delays being chosen following a law adapted to compensate the determined Doppler effect.

Abstract: A method for supporting mobility of at least one mobile telecommunications terminal (5.1-5.3) in operative connection with a telecommunications network (2) having a plurality of telecommunications resources (3.1-3.6) accessible via a plurality of access networks (4.1-4.3) and associated access technologies (4.1a,b-4.3a,b) in operative connection with the telecommunications network (2), wherein the mobile telecommunications terminal (5.1-5.3) is provided with information about access networks (4.1-4.3) and access technologies (4.1a,b-4.3a,b) available at least at its present geographic location for choosing an access to the telecommunications network (2) via one of the respective access networks (4.1-4.3) and associated access technologies (4.1a,b-4.3a,b) in accordance with specifications of at least one telecommunications resource (3.1-3.6) requested by the mobile telecommunications terminal (5.1-5.3), and wherein the information are provided independently of the access networks (4.1-4.

Abstract: The invention relates to wavelength converters for optical signals, as used in telecommunications, in particular for routing signals. The invention relates in particular to a wavelength converter including an interferometer structure for delivering an output optical signal, in which converter first and second branches, including at least one first semiconductor optical amplifier, are coupled to input peripheral semiconductor optical amplifiers and/or to an output peripheral semiconductor optical amplifier, wherein the structure of the active waveguide of at least one peripheral amplifier is so designed that it has a ratio of active area to confinement factor greater than that of the active waveguide of said first amplifier.

Abstract: An interferometric semiconductor laser (YL) as well as optoelectronic arrangements with such a laser are disclosed. The laser has a special coupling segment (Z) which allows high optical output to be obtained without affecting the filtering function or significantly restricting the tuning range of the laser. Such a laser can be coupled with low loss to a subsequent optoelectronic component (e.g., a wavelength converter (WK)) which is monolithically integrated with the laser.

Abstract: An optical duplexer, configured as a directional coupler, is integrated into an optical coupling arrangement with a fiber optic pigtail, constructed in planar-optical hybrid technology on a substrate (1). To reduce the required surface area and decrease optical cross talk, the branch of the directional coupler (waveguide 6, branch 7) is sharply bent. The bend is equipped with a reflecting mirror (11) integrated opposite the inner edge (10) of the bend. Furthermore, the waveguiding end of the bent branch (7) is equipped with a cylindrical lens. A laser diode (8) is located before this, and a photodiode (5) is located before the angled end of the straight-line integrated waveguide (2).

Abstract: An integrated optoelectronic semiconductor component is presented, which can equally process light signals of any polarization direction. Such semiconductor components are used for digital optical telecommunications. The semiconductor component has active (A) and passive (B) waveguide sections, which comprise a number of semiconductor layers (SP) with so-called multiple quantum well structures. The semiconductor layers (SP) are deposited by a process known as selective area growth (SAG). A portion of the semiconductor layers has a lattice constant which is smaller than the lattice constant of a substrate (SUB). This creates a biaxial tensile strain in these layers. The tensile strain is optimized in the active waveguide sections (A) to attain polarization independence. Furthermore a process is described whereby such a semiconductor component can be manufactured.

Abstract: A semiconductor device is operated as an optical filter. The semiconductor device has a substrate and a monolithically integrated branched waveguide structure disposed above the substrate, portions of the waveguide structure being divided into a plurality of regions by troughs, one of the regions being a branching region. Light is radiated into the waveguide structure at an end face of one of the regions and currents that are smaller than respective laser threshold currents of the regions flow through the regions, including the branching region, perpendicular to a propagation direction of light through the waveguide.

Abstract: A semiconductor laser is provided monolithically integrated on a substrate and has a cavity layer extending above a plane that is coplanar with a base surface of the substrate, is branched and includes a plurality of separately controllable regions. The laser is operated by changing charge carrier density in at least one of the regions so that it emits light at one of a first wavelength and a second wavelength in correspondence with the charge carrier density change.

Abstract: An interferometric semiconductor laser includes a cavity in the form of a Y and at east three individually actuatable active segments. A central segment couples together the individually actuatable active segments. The central segment is an active or passive segment that acts as a beam divider. The arrangement of the segments forms two resonator paths which contain at least one common active segment. At least one resonator path includes an active segment that does not belong to the other resonator path. In the absence of, or with the same actuation of the active segments, the optical path length of one resonator path differs from the optical path length of the other resonator path.

Abstract: A semiconductor laser that is monolithically integrated on a substrate and whose cavity has a branched structure that is simply contiguous in a topological sense, and which includes a plurality of regions that enclose the cavity, is operated as a mode-locked semiconductor laser, with an alternating current flowing through at least one region in addition to a direct current. The frequency of the alternating current is related to the reciprocal of the round-trip time or an integral multiple of this reciprocal of light pulses generated by the alternating current in the semiconductor laser.

Abstract: An optical device includes a semiconductor laser monolithically integrated on a substrate having a branched cavity extending above a plane that is coplanar with a base surface of the substrate, and an adjustable optical power light source for radiating light into the cavity of the semiconductor laser thereby controlling the operation of the semiconductor laser optically.

Abstract: In a semiconductor laser having a semi-insulating layer on the sides of a mesa to confine the current to the mesa during operation of the laser, at least one n-type layer and at least one p-type layer are provided above or below the semi-insulating layer.

Abstract: A semiconductor laser which includes a controllable beam splitter has three segments including laser-active zones and a monitor diode forming a cross-shaped laser connected with one another by way of the beam splitter. The beam splitter is equipped with electrodes for controlling optical coupling between the segments.

Abstract: A semiconductor laser in which the photons injected from its waveguide region into the laser active region are those whose energies differ from the energy sum of the chemical potential of the electron-hole pairs and the energy of the longitudinal acoustic phonons by less than one-half the thermal energy is described. A current directed into the photon emission region in the area of the Bragg grating causes photons of this energy to be injected into the laser active region which is constituted of a layer of indium gallium arsenide phosphide.