Abstract: The present invention provides an optical receiver that uses an avalanche photodiode (APD) whose multiplication factor m is controlled to compensate the temperature dependence thereof. An optical module of the present invention includes a light-receiving device in addition to the APD. The light-receiving device may be a semiconductor thin film or a PIN photodiode, and is disposed in front of the APD. Accordingly, the light-receiving device receives a portion of signal light, and transmits a rest portion thereof. The APD receives the rest portion of the signal light. The bias voltage applied to the APD is so controlled that a first photocurrent generated in the light-receiving device and a second photocurrent generated in the APD maintain a constant ratio.

Abstract: An optical receiver includes an avalanche photodiode (APD) having a light-receiving area provided on a face of a first substrate, the light-receiving area receiving a part of signal light; a photodetector having a light-receiving area provided on a face of a second substrate, the light-receiving area receiving the other part of the signal light; and a mounting member having a principal plane on which the APD and the photodetector are mounted. Due to this structure, crosstalk between the APD and the photodetector does not occur and an avalanche multiplication factor of the APD can be controlled on the basis of the output current of the photodetector.

Abstract: An optical receiver includes a PIN photodiode (PIN-PD) having an incident surface for receiving signal light, the PIN-PD transmitting a part of the signal light to the surface opposite to the incident surface, and an avalanche photodiode (APD) having an incident surface for receiving light transmitted through the PIN-PD. In the optical receiver, the ratio of the quantity of signal light detected by the PIN-PD and the ratio of the quantity of signal light detected by the APD are not affected by the polarization state of the signal light incident on the optical receiver, and accordingly the avalanche multiplication factor of the APD is suitably controlled on the basis of the signal light detected by the PIN-PD.

Abstract: An optical receiver includes a light-receiving part and a control part. The light-receiving part includes an APD, a PIN-PD, and a branching optical device. First signal light is incident on the light-receiving part and is divided into second signal light and third signal light which are incident on the APD and the PIN-PD, respectively, by the branching optical device. Due to this structure, the third signal light is incident on the PIN-PD without the quantity thereof being varied depending on the polarization state of the first signal light. The control part generates a supply voltage at which a desired avalanche multiplication factor is obtained in the APD on the basis of the output current from the PIN-PD. According to the above-described structure, the avalanche multiplication factor of the APD is accurately controlled on the basis of the output current of the PIN-PD.

Abstract: A problem of the present invention is to provide a semiconductor laser module for making precise temperature control possible. A semiconductor laser module 1 according to the present invention has a Peltier element 4, a thermistor 5 for detecting the temperature of the Peltier element 4, and a differential amplification circuit 6 for generating a control signal according to the detection signal from the thermistor 5 so that the surface temperature of the Peltier element 4 conforms to a set temperature. A parallel compensating circuit 12 for generating a compensating signal for compensating for a delay in temperature variation in the Peltier element 4 with respect to the input of current signal to the Peltier element 4 branches and is connected to the output portion of the differential amplification circuit 6. The compensating signal is sent to an addition circuit 9 and detection correction signal obtained by adding the detection signal of the thermistor 5 and the compensating signal is generated.

Abstract: An optical module includes a semiconductor optical device, an optical fiber, a ferrule, and a mounting component. The optical fiber is optically coupled to the semiconductor optical device. The ferrule holds the optical fiber. The mounting component includes a first support groove for supporting the ferrule and a second support groove for supporting the optical fiber. The semiconductor optical device is mounted on the mounting component. The first and second support grooves are sequentially arranged in a direction of a predetermined axis. The second support groove has one end and the other end. The depth of the second support groove decreases from the one end toward the other end. With such a structure, the optical module allows the optical fiber to be positioned with high accuracy onto the mounting component.

Abstract: The present invention provides an optical module capable of simplifying the assembly thereof. The optical module has a first substrate, an electronic device mounted on the first substrate, an optical device electrically connected to the electronic device, a fiber assembly coupled to the optical device and a housing. The housing has a base and a cover. The base has an opening, into which the first substrate is inserted, and a mounting region where the optical device is mounted thereon. The base and the cover sandwiches and secures the fiber assembly therebetween. The first substrate may be connected to a second substrate provided outside of the optical module with a flexible or a resilient connecting member.

Abstract: An optical transmission and receiver module suitable for a single-fiber bi-directional communication includes a light emitting device, a photodiode, an optical path routing element which allows light emitted from the light emitting device and light directed to the photodiode to pass through the element and which changes their optical paths, as required, and a lens transparent to both light emitted from light emitting device and light directed to the photodiode.

Abstract: An optical receiver comprises (a) an optical fiber, (b) a rear-illuminated type PD for receiving incoming light emerging from the optical fiber, (c) a submount supporting the PD, (d) a coaxial type package housing the submount, and (e) a preamplifier IC for amplifying electric signals from the PD. In particular, the submount is provided with a reflecting face for reflecting the incoming light so that the light can enter the PD. The submount may be provided with an optical path-forming groove having at least one reflecting face for introducing and reflecting the incoming light so that the light can enter the light-receiving portion of the PD mounted on the submount. This structure enables the production of an optical receiver most suitable for high-speed response and excellent in productivity. A method of producing the optical receiver is also offered.

Abstract: An optical receiver comprises a PD for receiving an incident light from an optical fiber, a preamplifier IC for amplifying an electrical signal from the PD, a submount on which the PD and the preamplifier IC are mounted on the same plane, and a package on which the submount is mounted. The PD and the preamplifier IC are directly connected to each other by a wire, and these components are both mounted on the same submount. Therefore, the distance between the PD and the preamplifier IC can be reduced, and parasitic inductance, parasitic capacitance, etc. can be greatly reduced. As a result, an optical receiver is provided which has reduced parasitic inductance and parasitic capacitance, and which is optimum for high speed response.

Abstract: It is an object of the present invention to provide a driving circuit which can drive a light emitting element in spite of a reduced power supply voltage and which is thus suitable for size reduction. The present invention provides a driving circuit which supplies a bias current to a light emitting element and which carries out modulation on the basis of voltage driving, the driving circuit comprising a boosting circuit that increases a power supply voltage Vcc, a resistance element connected between an output of the boosting circuit and an anode terminal of the light emitting element, and a capacitive element connected to the anode terminal of the light emitting element to supply a modulation signal to the light emitting element for voltage driving.

Abstract: A problem of the present invention is to provide a semiconductor laser module for making precise temperature control possible.

Abstract: This optical module comprises a photodiode 1, a current mirror circuit 2 having two parallel lines, one of the lines being connected to the photodiode 1, and a transimpedance amplifier 3 connected to the photodiode 1. Since the current mirror circuit 2 is provided, the photocurrent from the line flows into the photodiode 1 and amplified by the transimpedance amplifier 3. This photocurrent is observed as a current flowing out of the other line of the current mirror circuit 2.

Abstract: Since this photocurrent monitor circuit can detect, by way of first and second current mirror circuits 2F, 2R, a current proportional to the photocurrent flowing into a photodiode 1 from a photocurrent monitor terminal IMT, it can monitor the correct photocurrent without its detecting circuit influencing the photocurrent of the photodiode itself.

Abstract: A sub-assembly containing an optical element and having a holder portion into which a ferrule that is attached to the end portion of an optical fiber can be inserted with sufficient gap, an electronic circuit electrically connected to the optical element, and a lead frame are molded with a transfer mold resin to produce a molded sub-assembly. The ferrule is inserted into the holder portion of the molded subassembly, and the optical coupling efficiency between the optical fiber and the optical element is adjusted while moving the ferrule in the ferrule insertion direction, a direction perpendicular thereto or by rotating the ferrule.

Abstract: A signal detecting apparatus is to obtain hysteresis characteristic at a constant ratio regardless of signal amplitude fluctuations by supplying the threshold level adjusting signal corresponding to the input signal amplitude to the comparison circuit. The threshold value setting signal and the hysteresis adjusting signal is supplied to a comparison circuit through an amplifier and a hysteresis adjusting means having the identical characteristic with the peak hold circuit to set a threshold value and a hysteresis range. Therefore even in the case where the operating characteristic of the amplifier and the peak hold circuit for detecting the peak level of signal amplitude fluctuate, the threshold value and the hysteresis range fluctuation corresponding to the fluctuation. As a result, there can not need the adjustment for resetting the operating characteristic, the threshold value and the hysteresis range in each circuit and thus the time and labor required for adjustment can be further saved.

Abstract: A luminous element and driving circuit in which an additional circuit is connected in parallel with the luminous element which in turn is serially connected with a suitable transistor. The additional circuit includes an element for minimizing distortion of the luminous output. In one embodiment, a field effect transistor with its gate and source connected together is serially connected with a coil to quickly discharge the luminous element when the transistor is turned off and charge the element quickly when the transistor is turned on. In a second embodiment, a semiconductor diode is serially connected to the coil to form the additional circuit. The voltage across the light emitting diode when the transistor is turned off causes the luminous element to be immediately luminous.

Abstract: A light detecting circuit in which noise superposed on a bias voltage of a photodiode is substantially canceled without the aid of a filter circuit employing an inductor. The photodiode is connected between a bias voltage terminal and an inverting terminal of a main amplifier, the latter being implemented with a differential amplifier or a comparator. A capacitance device is connected between the same bias voltage terminal and the other (noninverting) input terminal of the main amplifier. The capacitance device may be either a physical capacitor or a second photodiode which, in either case, should have a capacitance equal to the parasitic capacitance of the first photodiode.

Abstract: An optical connector in which a pair of ceramic optical plugs having optical fibers extending coaxially therethrough are fitted within a ceramic sleeve. In one embodiment, an inner surface of the sleeve is provided with a longitudinal groove extending from one end of the sleeve to the other so that air and dust will be expelled from the sleeve when plugs are inserted therein. A housing may be provided around the sleeve with a flange being formed on the housing. In another embodiment, a protective cover is provided surrounding each plug which is movable axially along the plug.