Mitsubishi Electric Corporation

Satoshi Yoshima

Masaki Noda

Masamichi Nogami

Junichi Nakagawa

Kazuyuki Ishida

Takanori Kawanaka

Susumu Ihara

Ayano Sakamoto

A single-fiber bidirectional optical ring system includes: a central station; slave stations; and a network which connects the central station and the slave stations in a ring shape by optical fibers. The central station includes: a first single-fiber bidirectional optical transceiver connected in a clockwise direction of the network, which outputs a downstream optical signal of a second wavelength and receives an upstream optical signal of a first wavelength; a second single-fiber bidirectional optical transceiver connected in a counterclockwise direction of the network, which outputs a downstream optical signal of the second wavelength and receives an upstream optical signal of the first wavelength; and a first time synchronization control circuit that adjusts timings at which the downstream optical signals of the second wavelength are outputted, and causes the first and second single-fiber bidirectional optical transceivers to output the downstream optical signals of the second wavelength in different time slots.

Single-fiber bidirectional optical ring system, method for controlling single-fiber bidirectional optical ring system, and central station

A signal detection circuit includes: a first DC voltage remover that removes a DC voltage from an input differential signal; a limiting amplifier that adjusts an amplitude of the input differential signal; a reset signal generator that generates an internal reset signal on the basis of the input differential signal obtained after the amplitude is adjusted; a first bias voltage applying unit that generates a differential signal for detection by applying a bias voltage to the signal from which the DC voltage is removed; and a flip-flop circuit that generates a packet detection signal by holding a state indicating input of a packet signal on the basis of the differential signal for detection and releasing the holding on the basis of the internal reset signal. The reset signal generator includes: a differential single-phase conversion circuit; a voltage holding circuit; and a voltage comparison circuit.

Signal detection circuit, optical receiver, master station device, and signal detection method

Provided is an emphasis circuit capable of obtaining a desired emphasis amount with which waveform deterioration of an output signal in a high frequency band (high frequency band deterioration) is suppressed without increasing power consumption (current consumption). In the emphasis circuit, a baseband amplifier section and a peaking amplifier section are connected in parallel to each other, and respective drive current setting sections are adjusted to adjust respective drive current values thereof so that the sum of the drive current value of the baseband amplifier section and the drive current value of the peaking amplifier section may be constant.

Emphasis circuit

A burst-signal reception circuit that receives a differential signal of a burst signal input via a preamplifier. The burst-signal reception circuit includes a differential amplifier to which the differential signal is input via capacitors, an average detection circuit that detects an average of a differential input signal to the differential amplifier, and a differential-offset cancel circuit that operates to cancel a DC voltage level difference of the differential input signal on the basis of output signals of the average detection circuit. Average detection speed of the average detection circuit is configured to be switched according to presence or absence of burst signal reception. The average detection speed is switched to a high-speed side in a head portion of the burst signal and switched to a low-speed side in portions other than the head portion.

Burst-signal reception circuit

A burst-mode receiver for receiving burst optical signals having different intensities by a reversely connected APD, including: a current detection circuit outputting a photocurrent that is generated by APD and is output from a current mirror circuit (CMC) as a voltage proportional to the photocurrent, the CMC being connected in series between a power supply and APD; a peak detector circuit detecting and holding a peak value of the output voltage of the current detection circuit; a resistor connection switching circuit, which is inserted between the CMC and APD, for connecting a series resistor to APD in series by switching; and a comparator outputting a switching signal for switching the resistor connection switching circuit so that the series resistor is connected to APD in series in a case where a voltage detected by the peak detector circuit is equal to or more than a predetermined threshold.

Burst-mode receiver, and method of bias voltage control for APD of burst-mode receiver

An optical receiver includes a light receiving element configured to convert an input light signal into an electric current, a current mirror circuit including a reference current side transistor and a mirror current side transistor, the transistor being connected to the light receiving element, a current-voltage conversion circuit configured to convert an output current from the transistor into a voltage and output the voltage as a light reception level monitor voltage of the light receiving element, and a current sink circuit connected to the transistor and configured to feed an electric current to the transistor.

Optical receiver, station-side optical network unit, and light reception level monitoring method

To enable optical line terminal to detect input disconnection of optical burst signal accurately in spite of changes of transmission rate of optical-burst signal received from optical network unit, OLT (optical line terminal) includes photo-detector for converting the optical-burst signal received to current signal; preamplifier for converting the current signal to voltage signal; input disconnection detecting circuit for comparing output amplitude of preamplifier with threshold, and for outputting input disconnection signal indicating disconnection of input of the optical-burst signal; and control circuit for controlling conversion gain of preamplifier in a manner that the conversion gain becomes conversion gain corresponding to the transmission rate of the optical-burst signal received, and for controlling input disconnection detecting circuit in a manner that it outputs the input disconnection signal in response to the threshold corresponding to the transmission rate of the optical-burst signal received.

Optical line terminal

A laser diode drive circuit includes a laser diode (LD), a modulation-current differential drive circuit, a bias-current differential drive circuit, a first inductance connected between an anode of the LD and a positive power source, a second inductance connected between a cathode of the LD and a negative-phase output terminal of the bias-current differential drive circuit, a first resistor connected to a connection point of the anode of the LD and the first inductance and connected to a negative-phase output terminal of the modulation-current differential drive circuit, and a second resistor connected to a connection point of the cathode of the LD and the second inductance and connected to a positive-phase output terminal of the modulation-current differential drive circuit, and a positive-phase output terminal of the bias-current differential drive circuit is connected to the connection point.

Growing community of inventors

Tokyo, Japan

Satoshi Yoshima