Abstract: A laser module includes: a chassis having a light-output window from which one or more laser beams are outputted; a hermetically sealed package which is fixed to the chassis; one or more semiconductor laser elements which are arranged in the hermetically sealed package, and emit the one or more laser beams; a transparent member which is arranged to cover the light-output window; an optical fiber which has a light-entrance end face, and is arranged outside the chassis so that the light-entrance end face is in contact with the transparent member; and an optical condensing system which is arranged inside the chassis, and makes the one or more laser beams pass through the transparent member and be condensed on the light-entrance end face. The transparent member and the optical fiber are detachably attached to the chassis.

Abstract: The present invention relates to a method for generating a single-sideband optical signal. According to the method, as data signals having a 90-degree phase difference with respect to input data signals, which are NRZ signals at 10 Gb/s, 0.5-bit delay data signals are generated by a 0.5-bit delay circuit for obtaining a delay corresponding to ?/2 of the bit period of the input data signal. An SSB optical signal produced from the data signals and the 0.5-bit delay data signals is generated through an optical filter. Further, to eliminate a residual intensity-modulated component, the generated SSB optical signal is fed back to appropriately adjust the center frequency of the optical filter. The carrier output frequency of a semiconductor laser can be adjusted instead of the center frequency of the optical filter. When an RZ signal is used as an input data signal, a 0.25-bit delay circuit is used.

Abstract: Laser beams are synthesized by offsetting in different positions in the direction of the fast axis beam bundles radiated from semiconductor lasers, converging the optical axes of the beam bundles in the fast axis view, and introducing the beam bundles into an optical fiber after converging them in the directions of the fast and slow axes. A convergent angle transforming optical system is disposed further upstream of the upstream-most position in the positions where the optical axes of the beam bundles converged in the fast axis view intersect in the fast axis view. The whole beam bundle formed of the beam bundles converged in the fast axis view is passed through the convergent angle transforming optical system so that the angle of convergence of the whole beam bundle or part of the beam bundles is made smaller in the fast axis view, and introduced into the optical fiber.

Abstract: The present invention provides an optical modulator, a method of manufacture thereof and an optical transmitter employing the optical modulator. In one embodiment, the optical modulator includes a substrate having a waveguide located therein, and an electrode, located adjacent the waveguide, having at least one aperture located therein.

Abstract: The present invention provides an optical modulator, a method of manufacture therefore, and an optical communications system including the optical modulator. The optical modulator may include a substrate, a waveguide located within the substrate and electrodes located over the substrate. Additionally, the waveguide includes a first doped region and a second doped region that overlaps the first doped region and is located adjacent an outer surface of the substrate and the electrodes.

Abstract: The present invention relates to a method for generating a single-sideband optical signal. According to the method, as data signals having a 90-degree phase difference with respect to input data signals, which are NRZ signals at 10 Gb/s, 0.5-bit delay data signals are generated by a 0.5-bit delay circuit for obtaining a delay corresponding to &pgr;/2 of the bit period of the input data signal. An SSB optical signal produced from the data signals and the 0.5-bit delay data signals is generated through an optical filter. Further, to eliminate a residual intensity-modulated component, the generated SSB optical signal is fed back to appropriately adjust the center frequency of the optical filter. The carrier output frequency of a semiconductor laser can be adjusted instead of the center frequency of the optical filter. When an RZ signal is used as an input data signal, a 0.25-bit delay circuit is used.

Abstract: An improved optical waveguide device having an optical waveguide for guiding a lightwave comprises, on a surface of a substrate having an electrooptical effect, at least a pair of electrodes composed of a hot electrode and a ground electrode which controls a guided lightwave, a buffer layer formed between the electrodes and the optical waveguide; further comprising an antistatic film which is formed on an upper surface of the buffer layer such that it comes into contact only with the hot electrode.

Abstract: An optical waveguide device usable as an optical wave-modulator and having a reduced DC drift includes a LiNbO.sub.3 substrate, an optical waveguide formed in a front surface portion of the substrate, a dielectric layer covering the front surface of the substrate and the optical waveguide surface, and an electrode system arranged on the dielectric layer, the dielectric layer comprising a matrix component consisting of an amorphous SiO.sub.2 and a doping element component consisting of Li and/or Nb; and having a refractive index lower than that of the amorphous SiO.sub.2 matrix free from the doping element component.