Fujitsu Corporation

Makoto Miki

Toru Matsuyama

Tadashi Ikeuchi

Tadao Inoue

Norio Ueno

Norio Murakami

Toshiyuki Takauji

Hiroyuki Rokugawa

Masaaki Kawai

Hiroki Kanesaka

Using a switching signal from a coarse/fine switching and operation mode switching circuit, the width of change of a counter control value during power up is increased, and the width of change is reduced once a steady state is reached. In the steady state, the frequency of updating is limited by a control signal from an update permit control circuit. In the steady state, the frequency band of a current source in an LD driving circuit is reduced in width.

Light output control circuit

Light output control device

A circuit for controlling pulse width of a signal for driving a light emitting element, includes a pulse width control circuit capable of responding to multi-bit rates in the same circuit structure. For this purpose, the pulse width control circuit has a Tr/Tf control section controlling at least one of a rise time Tr and a fall time Tf of an input signal according to the bit rate of the input signal; a waveform shaping section shaping a signal output from the Tr/Tf control section to generate an output signal; and a control signal generating section generating a control signal for controlling an operation of the Tr/Tf control section based on pulse width control information.

Pulse width control circuit controlling pulse width of output light

The present invention alms at providing a low cost optical transmitter capable of controlling, with a high precision, fluctuations in optical output characteristic of a semiconductor light emitting device such as due to a temperature change. To this end, the optical transmitter of the present invention is constituted to comprise; a semiconductor light emitting device; a driving circuit for supplying a driving current to the semiconductor light emitting device; an optical output detecting section for detecting an optical output power of the semiconductor light emitting device; a storing section for storing temperature characteristic information including temperature characteristic data concerning the driving current to be supplied to the semiconductor light emitting device and temperature characteristic data concerning the optical output detecting section; a temperature detecting section for detecting temperature; and a controlling section for controlling the operation of the driving circuit, based on the temperature characteristic information read out from the storing section corresponding to the temperature detected by the temperature detecting section and based on the detection result of the optical output detecting section.

Optical transmitter provided with optical output control function

A light output control circuit to update light output synchronously with input data in burst signal transmission system is disclosed. The circuit has a function of issuing light deterioration warning unerringly, which includes: a monitoring portion to detect light output emitted from a light emission element driven in accordance with transmission data; a level comparator to compare a monitoring signal outputted from the monitoring portion with a reference signal; a data detection portion to detect the existence of the transmission data; and an output controller to determine whether a light output deterioration warning is to be issued using an output signal of the data detection portion and an output signal of the level comparator.

Light output control circuit with a warning function of deteriorated light output

An optical transmitter circuit including a light receiving element, such as a photodiode, which monitors the optical output of a light emitting element such as a semiconductor laser. A current-voltage converting circuit supplies a drive current from a drive circuit to the light emitting element and converts the output voltage of the light receiving element into voltage. An APC amplifier compares the converted output signals and a reference signal, and a hold circuit holds the output signal of the APC amplifier and uses the output signal as a current control signal of the drive circuit. A &ldquo;1&rdquo; continuous signal detecting circuit detects the continuation of &ldquo;1&rdquo; in a specified number of bits in the input data (DATA) and updates the hold value in the hold circuit.

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Sapporo, Japan

Makoto Miki