Abstract: The present invention provides an optical transmission module having a laser diode that generates laser beams and a differential type current switch provided with a first switch and a second switch in order to supply a modulating current to the laser diode. A terminal of the laser diode and the first switch are connected in series through a first transmission line and a first capacitor, the other terminal of the laser diode and the second switch are connected in series through a second transmission line and a second capacitor. The current driven by the second switch is terminated by a resistor connected to the first switch and the current driven by the first switch is terminated by a resistor connected to the second switch. Thus, the laser diode is modulated bidirectionally.

Abstract: According to the present invention there are provided a transmission line and an optical module having the transmission line, the transmission line having on a dielectric substrate a first signal wiring conductor, a second signal wiring conductor insulated from the first signal wiring conductor, a first electrode disposed near the first and second signal wiring conductors, a second electrode disposed near the second signal wiring conductor, and a ground wiring conductor disposed in adjacency to the second electrode, wherein a passing frequency band can be changed by changing the connection of conductor wires.

Abstract: For preventing an optical axis from shifting due to a heat cycle in a semiconductor laser module, or in a optical transmitter, the semiconductor laser module comprises, a semiconductor laser element, a frame for storing the semiconductor laser element therein, an optical fiber fixing portion being connected to the frame; and a flange being connected to the frame, and having a fixing portion for fixing the frame on a substrate, wherein the flange has a narrow width region between a fixing region, including a foxing portion with the substrate therein, and the frame, and the narrow width region is narrower than width of the fixing region.

Abstract: A variable optical attenuator VOA and a gain-clamped semiconductor optical amplifier GC-SOA are combined as an optical preamplifier. The variable optical attenuator is controlled so that a desired optical power is sent to the gain-clamped semiconductor optical amplifier or so that a desired optical power is sent to a photoelectric conversion stage. A optical power monitor is provided to compare a monitored value with a target value, and a variable optical attenuator control circuit controls the variable optical attenuator so that the deviation from the target value approximates 0.

Abstract: This optical transmission module wires and connects a coaxial can package in which high-speed signal transmission wiring whose characteristic impedance matches is formed on a ceramic PC board into which a coaxial can stem penetrates and a PC board on which a peripheral circuit is mounted using a flexible PC board in which the high-speed signal transmission wiring is formed in the same manner. The module makes, on the opposite side, an elastic conductive heat-conducting material is interposed between the coaxial can package and a housing in which a radiating fin is formed and the conductive heat-conducting material or an elastic insulating heat-conducting material between a circuit component mounted on a PC board and the housing in which the radiating fin is formed intervene. The module forms a fitting structure in each of a ferule and a receptacle portion of a transmission module or receiving module and can rotate to the direction of an optical axis.

Abstract: There is provided a thin and small size connector-less optical transmission module M which assures excellent high frequency characteristic. This optical transmission module comprises transmission line substrates and a coaxial cable for connecting these transmission line substrates and is connected to the transmission line substrate via a contact sleeve which is provided with projections fixed to the external conductor of the coaxial cable and projected in the extending direction of the coaxial cable. Since an electromagnetic field mode alleviating portion formed of a dielectric material is provided to the core wire of the coaxial cable, the thin and small size optical transmission module M can assure less amount of radiation of an interference electromagnetic wave, high frequency characteristic through connection with the coaxial cable.

Abstract: In the initial state, any wavelength variation of the output signal light with a change of the current injected into the laser is monitored with a wavelength meter, the quantity of wavelength variation is fed back to the wavelength compensation circuit, a compensation voltage for maintaining the wavelength in the initial stage is figured out, and that voltage is recorded into a memory element or the like. A configuration to add this compensation voltage to a comparator makes it possible to compensate for fluctuations of the characteristics of the optical splitter, wavelength filter and light receiving elements and thereby to obtain a stable optical wavelength. By constantly monitoring the injected current applied to the laser when the optical transmitter is in operation and giving a compensation voltage matching the current variation to the comparator, stabilization of the optical wavelength can be realized.

Abstract: For achieving a transmission light source having different transmission properties or characteristics, i.e., the a parameters, depending upon application thereof, in a light emission element of semiconductor EA modulator integrated type being constructed with a light emission portion for lasing with a single vertical mode and a plurality of EA modulators, wherein an absorption edge wavelength under the condition of applying no bias thereto, in the semiconductor multiple-quantum-well structure owned by the modulator which is near to an emission side of the light emission portion, is to be equal or longer than the absorption edge wavelength owned by the modulator positioned far from the emission side of the light emission portion.

Abstract: With respect to an avalanche photodiode (APD) having a semi-insulating re-grown guard-ring layer, its photocurrent-vs.-reverse-bias-voltage characteristic at several temperature-points is measured. Moreover, based on the measured result, the optical responsivity is determined from a flat portion that will appear in the photocurrent-vs.-reverse-bias-voltage characteristic at a temperature that is higher than the several temperature-points.

Abstract: Optical transmission equipment with more than one power supply which can, when turning on the power supplies, set predetermined function of a signal processing circuit after a predetermined time period after the last turn-on of the power supply and can enable the operation of a drive circuit of the light emitting device after an additional predetermined time period.

Abstract: Reducing a dark current in a semiconductor photodetector provided with a second mesa including an regrown layer around a first mesa. An n-type buffer layer, a n-type multiplication layer, a p-type field control layer, a p-type absorption layer, a cap layer made of p-type InAlAs crystal, and a p-type contact layer 107 are made to grow on a main surface of a n-type substrate. Thereafter the p-type contact layer, the p-type cap layer, the p-type absorption layer and the p-type field control layer are patterned to form a first mesa. Next, after making a p-type regrown layer selectively grow around the first mesa or by forming a groove in the regrow layer located in a vicinity of the p-type cap type during a step of the selective growth, the p-type cap layer containing Al and the regrow layer are separated owing to the groove such that no current path is formed between both layers.

Abstract: A transmission line with a bending portion is provided, which line comprises any one of a coplanar line, another coplanar waveguide line formed on the dielectric substrate under which a ground layer is provided and a coplanar strip line. A chamfered portion is provided on the outer angular portion of the bending portion of the signal wiring conductor and a triangular conductor is disposed to an inner angular portion thereof. Given that length of the chamfered portion is defined as a, and length of the wiring edge side of the triangular conductor is defined as b and width of the signal wiring conductor is defined as c, it is arranged such that a is greater than b+c×square root of 2. Thereby, a transmission line or an optical module of smaller reflection loss at the bending portion thereof and of improved high-frequency characteristics is provided.

Abstract: In an optical module including an optical element and a semiconductor IC for driving it in a case, a metal stem 35 on which an optical element 10 is mounted is provided with a wiring plate 11, a semiconductor IC 30 for electrically driving the optical element 10, and the wiring plate 11 are connected with each other by wires 16, and further the wiring plate 11 and the optical element 10 are connected with each other by the wires 16. The optical communication module having excellent high frequency characteristics is formed that shuts out influence of heat from the semiconductor IC upon the optical element and causes no interference between the semiconductor IC and optical connecting lenses.

Abstract: A PD (20) is mounted to a position offset (23) as viewed in the direction orthogonal to the center of an optical axis (14) of backward light (13) of an LD (11) in such a manner that a light receiving plane (21) thereof becomes substantially parallel to the center of the optical axis. Alternatively, the PD (20) is mounted thereto so that the light receiving plane of the PD is inclined at angles ranging from about 0° to about 30° to the center of the optical axis of the backward light. Further, the PD whose side face on the LD side is inclined, is used to repeatedly reflect the backward light between the PD and an LD mounting substrate, after which the backward light is launched on the light receiving plane 21.

Abstract: A Mach-Zehnder optical modulator that can attain a higher transmission speed than the driver signal speed but also attains, by setting multi-value amplitudes, an information transmission volume corresponding to an integer multiple of a single driver while allowing the transmission speed to remain as it is, wherein plural optical waveguide branches and plural Mach-Zehnder modulator portions are used, and by utilizing a propagation delay of a modulation signal for driving each of the modulator portions there is attained a transmission speed proportional to the delay time. This leads to a transmission signal having a frequency higher than the cut-off frequency of, for example, an IC or a transmission line substrate having an electrical characteristic of generating and propagating a modulation signal in such a form as an optical MUX (multiplexer).

Abstract: The present invention provides a highly reliable ridge-waveguide semiconductor laser diode and an optical module. The p-side electrode of the ridge-waveguide laser diode has a first conductor layer region and a second conductor layer region formed on the first conductor layer region. At least one of facets of the second conductor layer region is recessed inward from a reflection facet. Thus, the ridge-waveguide semiconductor laser diode has a structure in which strain which is caused by the electrode stress to be applied on the diode facet is reduced and the saturable absorption does not occur. The ridge-waveguide semiconductor laser diode thus obtained is highly reliable, and the optical module using the same is remarkably high in reliability.

Abstract: An optical transmission module with an optical device mounted in a substrate provided with an optical waveguide is provided wherein respective metallic electrodes in pair are symmetrically disposed in each side of an optical device divided by a centerline parallel to an optical axis such that those electrodes have an error of 60 &mgr;m or less and said metallic electrodes are soldered to a metallic electrode as disposed on a substrate, which electrode has a size enough to cover those electrodes as disposed in the optical device.

Abstract: An optical receiver circuit comprising: a pre-amplifier for amplifying a signal supplied from a photodetector to output positive and negative signals; first and second peak hold circuits for detecting maximum levels of these positive and negative signals respectively; an offset canceler circuit for compensating the positive signal at the maximum level of the negative signal, for compensating the negative signal at the maximum level of the positive signal, and for then performing differential amplification; and a level shift circuit for replacing an output signal level of the first peak hold circuit with a signal level higher than an actual value for a period of time that light input to the photodetector is in a no-input signal state.

Abstract: The provision of a coplanar waveguide coupled with a microstrip line with a transmission line substrate that is used between two functional units of different impedance characteristics allows the input and output impedance matching to be performed, the impedance matching between which coplanar waveguide and microstrip line is performed by the variation of the signal linewidth. It allows the transmission characteristics of the optical transmission device in high frequency band to improve.

Abstract: An optical transmitter comprises a modulator for generating a modulated current in accordance with a modulation control signal, a light emitting element driven by the modulated current from the modulator to emit light in accordance with the modulated current, a first current source for supplying the modulator with a driving current, a first temperature detector for detecting an operating temperature of the modulator to output a signal indicative of a detected operating temperature of the modulator, and an amplifier for receiving a data signal to supply the modulator with the modulation control signal based on the data signal. The amplifier has a first modulation control signal controller for controlling a changing amount per unit time of the modulation control signal at rising and falling times in accordance with an output signal of the temperature detector.