Abstract: According to one aspect of this invention, there is provided a transmitting and receiving device including a transmitting device having a pulse width modulation encoder which generates a pulse width signal having a pulse width corresponding to the binary digital signals outputted from the plurality of sigma-delta analog-to-digital conversion units, and a light-emitting element drive unit which generates and transmits an optical signal by causing a light-emitting element to emit light on the basis of the pulse width signal, and a receiving device having an optical reception unit which converts a current signal, obtained by receiving the optical signal by a light-receiving element, into the pulse width signal, and a pulse width demodulation decoder which reconstructs the binary digital signals of a plurality of channels on the basis of the pulse width signal.

Abstract: An optical receiver includes a first light receiving element to convert an optical signal to an electric signal and to output the electric signal from one end. A light receiving element row is connected to the other end of the first light receiving element to supply electric power to the first light receiving element. The light receiving element row includes a plurality of second light receiving elements connected in series.

Abstract: There may be provided a receiving apparatus including: a light receiving element which receives an optical signal and generates a current signal dependent on the optical signal; a conversion unit which converts the current signal into a voltage signal; a reference voltage generation unit which generates a reference voltage; a threshold voltage generation unit which generates, based on the voltage signal outputted from the conversion unit and the reference voltage outputted from the reference voltage generation unit, a threshold voltage signal having an amplitude smaller than an amplitude of the voltage signal with reference to substantially the center of amplitude range of the voltage signal and delayed by a predetermined time period from the voltage signal; and a comparison unit which compares the voltage signal outputted from the conversion unit with the threshold voltage signal outputted from the threshold voltage generation unit.

Abstract: According to one aspect of this invention, there is provided a transmitting and receiving device including a transmitting device having a pulse width modulation encoder which generates a pulse width signal having a pulse width corresponding to the binary digital signals outputted from the plurality of sigma-delta analog-to-digital conversion units, and a light-emitting element drive unit which generates and transmits an optical signal by causing a light-emitting element to emit light on the basis of the pulse width signal, and a receiving device having an optical reception unit which converts a current signal, obtained by receiving the optical signal by a light-receiving element, into the pulse width signal, and a pulse width demodulation decoder which reconstructs the binary digital signals of a plurality of channels on the basis of the pulse width signal.

Abstract: An optical receiver comprises a first light receiving element to convert an optical signal to an electric signal and to output the electric signal from one end thereof; and a light receiving element row connected to the other end of said first light receiving element to supply electric power to said first light receiving element, said light receiving element row including a plurality of second light receiving elements connected in series.

Abstract: A photo-detecting semiconductor device according to an embodiment of the present invention has a first photodetector element and a second photodetector element placed adjacent to each other and isolated from each other to each generate an electric signal responsive to a received optical signal; a signal detecting circuit which amplifies the electric signal from said first photodetector element and outputs a detection-use electric signal to detect a predetermined optical signal received at said first photodetector element; a power supply circuit which starts the supply of power upon receiving said detection-use electric signal from said signal detecting circuit; and a signal output circuit supplied with power from said power supply circuit to amplify the electric signal from said second photodetector element and output an output-use electric signal. An electrical circuit has the photo-detecting semiconductor device.

Abstract: An LED is an element in which when a voltage pulse applied to the intrinsic diode of an electrical equivalent model reaches a peak value, a current suddenly flows to obtain an optical output proportional to the forward current. By utilizing this property, the LED receives a rectangular voltage pulse having a large-current driving ability at a low output impedance, or a voltage pulse having two high levels. The low level of the voltage pulse is set within a voltage range where the extinction ratio of an output signal from the LED can be maintained. Even in an LED having a large internal capacitance, an increase in power consumption can be minimized, the transient response time can be shortened, high-speed modulation can be performed, and output light almost free from pulse waveform distortion can be obtained.

Abstract: A light-emitting diode driving circuit according to an embodiment of this invention includes a light-emitting diode, a first current switch circuit connected in series with the light-emitting diode, the first current switch circuit turning on/off a current in accordance with an external input signal input from an input terminal, a pulse current generating circuit connected in parallel with the first current switch circuit, the pulse current generating circuit supplying a pulse current including a pulse width smaller than the pulse width of the external input signal and shaping a leading edge portion of an optical waveform output from the light-emitting diode into a desired optical waveform, and a discharge circuit connected in parallel with the light-emitting diode, the discharge circuit quickly discharging charge stored in the light-emitting diode when the current to the first current switch circuit is turned off.

Abstract: A photo-detecting semiconductor device according to an embodiment of the present invention has a first photodetector element and a second photodetector element placed adjacent to each other and isolated from each other to each generate an electric signal responsive to a received optical signal; a signal detecting circuit which amplifies the electric signal from said first photodetector element and outputs a detection-use electric signal to detect a predetermined optical signal received at said first photodetector element; a power supply circuit which starts the supply of power upon receiving said detection-use electric signal from said signal detecting circuit; and a signal output circuit supplied with power from said power supply circuit to amplify the electric signal from said second photodetector element and output an output-use electric signal. An electrical circuit has the photo-detecting semiconductor device.

Abstract: A light-emitting diode driving circuit according to an embodiment of this invention includes a light-emitting diode, a first current switch circuit connected in series with the light-emitting diode, the first current switch circuit turning on/off a current in accordance with an external input signal input from an input terminal, a pulse current generating circuit connected in parallel with the first current switch circuit, the pulse current generating circuit supplying a pulse current including a pulse width smaller than the pulse width of the external input signal and shaping a leading edge portion of an optical waveform output from the light-emitting diode into a desired optical waveform, and a discharge circuit connected in parallel with the light-emitting diode, the discharge circuit quickly discharging charge stored in the light-emitting diode when the current to the first current switch circuit is turned off.

Abstract: An LED is an element in which when a voltage pulse applied to the intrinsic diode of an electrical equivalent model reaches a peak value, a current suddenly flows to obtain an optical output proportional to the forward current. By utilizing this property, the LED receives a rectangular voltage pulse having a large-current driving ability at a low output impedance, or a voltage pulse having two high levels. The low level of the voltage pulse is set within a voltage range where the extinction ratio of an output signal from the LED can be maintained. Even in an LED having a large internal capacitance, an increase in power consumption can be minimized, the transient response time can be shortened, high-speed modulation can be performed, and output light almost free from pulse waveform distortion can be obtained.

Abstract: A light-receiving circuit according to the present invention incorporates an amplifier 12 having differential output terminals, and it is intended that normal-phase and inverted-phase outputs (Vp, -Vp) of the amplifier 12 be supplied to a comparator 34 at an appropriate threshold level at all times. To achieve this intention, a peak-value voltage (Vi) of the normal-phase and inverted-phase outputs of the amplifier 12 is detected by a peak value detector 26, and is converted into a current by means of a voltage-current converter 28 having a mutual conductance of gm. The voltage-current converter 28 has differential output terminals, from which a normal-phase output (I.sub.+ =gm.Vi) and an inverted-phase output (I.sub.- =gm.Vi) are produced, respectively. The currents (I.sub.+, I.sub.-) are converted into voltages by means of resistors R10 and R12.

Abstract: The present invention aims to provide a fiber optic receiving circuit which can obtain a sufficient frequency band even if a junction capacity of a photo diode is large, wherein a voltage dividing ratio of said voltage dividing circuit, a capacity value of a capacitor, a junction capacity value of a photo diode, and an open loop gain of an amplifier are determined so that current, which flows in the capacitor, cancels current, which flows in a junction capacity of the photo diode and causes frequency deterioration, and the junction capacity of the photo diode, which causes the frequency deterioration, does not relate to an output voltage of the amplifier, thereby obtaining a flat gain characteristic over the broad range of the frequency band regardless of the junction capacity of the photo diode.

Abstract: A duplex optical communication module unit is disclosed, which comprises a ceramic substrate and first and second metal shells having respective transparent window members and hermetically bonded to the ceramic substrate so as to define a first and second space, respectively. A light-emitting element is assembled in the first space, and a light-emitting element and a circuit element for amplifying the photocurrent from the light-emitting element are assembled in the second space. Metallization layers are formed on the ceramic substrate over a substantial area thereof, light-receiving and light-transmitting sections being shielded by the metallization layers and metal shells.