Fujitsu Corporation

Hiroki Kanesaka

Toru Matsuyama

Makoto Miki

Yasushi Koiwai

A light source driving apparatus, which adjusts a bias current to be supplied so as to control intensity of a light source, comprises a power source which outputs a variable reference voltage; a light receiving unit which receives light output from the light source and converts the light into an electric signal; a bias supply unit which supplies a bias current, which is based on an intensity control signal according to the electric signal converted by the light receiving unit and the reference voltage output from the power source, to the light source; and a voltage control unit which acquires information about intensity characteristics with respect to the intensity control signal of the light source and controls the reference voltage according to the acquired information about the intensity characteristics.

Light source driving apparatus and light source driving method

An optical apparatus comprises a phase comparator detecting a phase shift between a changing point of data transmitted through an electro/opto converter and a changing point of data received through an opto/electro converter, a delay controller and a variable delay circuit controlling a delay of the transmitted data so that the phase shift detected becomes equal to a value which minimizes a receiver sensitivity degradation due to crosstalks between a transmitter portion and a receiver portion.

Optical apparatus

An apparatus is provided with a biasing unit supplying a bias signal to a first avalanche photodiode and a second avalanche photodiode, the bias signal having a first level and a second level, the first level causing a multiplying effect and the second level causing a non-multiplying effect for the first and the second avalanche photodiodes; a smoothing unit smoothing the bias signal biasing the first avalanche photodiode into a smoothed bias signal; a current detecting unit detecting photocurrent from the second avalanche photodiode, with a multiplying current value corresponding to the multiplying bias level and a non-multiplying current value corresponding to the non-multiplying bias level; a multiplication factor calculating unit calculating a multiplication factor of the second avalanche photodiode based on the multiplying current value and the non-multiplying current value; and a control unit controlling the first level of the bias signal based on the calculated multiplication factor.

Bias control apparatus for avalanche photodiode and optical apparatus utilizing the bias control apparatus

An apparatus for transmitting and receiving optical signals and which is independent of the optical transmission bit rate. The apparatus includes an optical transmitting unit and an optical receiving unit. The optical transmitting unit receives a clock signal and transmits an optical signal at a bit rate corresponding to the frequency of the clock signal. The optical receiving unit receives an optical signal, converts the received optical signal into an electrical signal and processes the electrical signal to be an electrical representation of the received optical signal. The optical receiving unit has frequency characteristics which are controllable in accordance with the frequency of the clock signal to control the processing of the electrical signal. For example, the optical receiving unit can include an amplifying unit which amplifies the electrical signal, wherein the gain and band of the amplifier are controllable in accordance with the frequency of the clock signal. Also, the optical receiving unit can include a filter for filtering the electrical signal, wherein the cut-off frequency of the filter is controllable in accordance with the frequency of the clock signal.

Optical receiving unit having frequency characteristics which are controllable in accordance with a clock signal used to transmit data

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 device for driving a light emitting element, including a DC power source for generating a DC current, a signal driving unit for controlling, in an on-off manner, the DC current generated in the DC power source on the basis of signal data with timing in accordance with the signal data, a light emitting element which is driven by the DC current controlled in the on-off manner by the signal driving unit and emits light when the DC current flows thereto, a high-speed pulse controlling unit for controlling, in an on-off manner, the DC current which drives the light emitting element at a sufficiently short period in comparison with the signal data to pulse the DC current, and a driving control unit for controlling the timing of on-off control of the high-speed pulse controlling unit in accordance with a required mean optical output.

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Kawasaki, Japan

Hiroki Kanesaka