Fujitsu Corporation

Toshiyuki Takauji

Tadashi Ikeuchi

Tadao Inoue

Toru Matsuyama

Norio Ueno

Norio Murakami

Makoto Miki

Hiroyuki Rokugawa

Masaaki Kawai

Satoshi Ide

Yuji Tochio

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

An optical transmission circuit includes: a semiconductor laser; a drive circuit for supplying drive current to the semiconductor laser; a duty changing circuit for changing a duty value of an input data; a converting circuit for supplying a duty control signal to the duty changing circuit in order to adjust the duty value of the input data; and an adjusting circuit for supplying an optical power control signal to the converting circuit and the drive circuit. The adjusting circuit performs an initial setting of an optical power of the semiconductor laser, and the converting circuit performs the initial setting of the duty value so as to have a characteristic opposite to the optical power. According to the above structure, it is possible to realize the duty adjustment and the optical power adjustment by using only one adjusting circuit so that it is possible to achieve a simplified, miniatuarized, and low cost optical transmission circuit.

Optical transmission circuit using a semiconductor laser

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

The present invention provides a light emitting element driving apparatus having a driving unit for driving a light emitting element by means of a driving signal while performing automatic light power control, which enables a light output to rise at a high speed in the head portion of a burst signal to be first inputted and light outputs of a second burst signal after the first burst signal and signals thereafter to be stably supplied irrespective of holding time. To this end, the light emitting element driving apparatus comprises a reference voltage generation unit for generating a reference voltage from an input electric signal containing data information, the reference voltage being used for obtaining a light output having specified power from the light emitting element in a normal condition, a monitoring voltage generation unit for generating a monitoring voltage signal corresponding to power of an optical signal outputted from the light emitting element, a light power control unit for controlling, based on a result of comparison from the reference voltage and the monitoring voltage signal, the driving unit by a discrete control amount such that a light output from the light emitting element can have the specified power and an initial value setting unit for setting a raising component as an initial value in a control signal having the discrete control amount.

Light emitting element driving apparatus

A burst mode optical transmitter circuit comprises a semiconductor laser, a photodiode for monitoring the light output from the semiconductor laser, a current-voltage converting circuit for converting the current detected by the photodiode into a voltage, an APC amplifier, a holding circuit for holding, as a current control signal, the output signal from the APC amplifier, a driving circuit for supplying a driving current to the semiconductor laser according the current control signal from the holding circuit and the the data input in the burst mode, and a data interruption detecting circuit for detecting an interrupt period of the data input to the driving circuit to reset the holding circuit, in which the current control signal held in the hold circuit is reset by the reset signal, whereby a stable burst optical transmission can be performed stably with a simple construction.

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Sapporo, Japan

Toshiyuki Takauji