Fujitsu Corporation

Akihiko Yasuda

Yuji Miyaki

Hiroshi Kuzukami

Kazuhiro Suzuki

Setsuo Misaizu

Hisaya Sakamoto

Norio Nagase

Yoshinori Ohkuma

The control circuit for supplying a driving current to a laser diode makes it possible to keep the laser driving current variable in a wide range. The control circuit includes a laser diode, a photo diode for receiving a part of an optical output emitted from the laser diode and outputting an electrical signal corresponding to a level of the optical output, a first current supplying circuit for supplying a bias current to the laser diode, a first monitor circuit for monitoring a size of a signal driving current supplied by the first current supplying circuit, a second monitor circuit for monitoring a size of the bias current supplied by the second current supplying circuit, a first feed-back loop for controlling the signal driving current supplied from the first current supplying circuit by the output of the first monitor circuit, as a reference of the electric signal outputted from the photo diode corresponding to the level of the optical output emitted from the laser diode, a second feed-back loop for controlling the bias current supplied from the second current supplying circuit by the output of the second monitor circuit, as said reference of the signal outputted from the photo diode corresponding to the level of the optical output emitted form the laser diode; and an adder circuit for adding an offset current of the signal driving current supplied from the first current supplying circuit on the outside of the first feed-back loop.

Control circuit for supplying a driving current to a laser diode

A light receipt system has a bias circuit and a light-receipt element. The bias circuit controls light input power to the light-receipt element to the optimum multiplication factor. The bias circuit of the light-receipt element has a first resistor, a second resistor, and a third resistor. The first resistor and the second resistor are connected in parallel, and the light-receipt element is connected between a connection of the first resistor and the second resistor, and the third resistor. A bypass current path is provided, connected to a junction point between the first resistor and the second resistor.

Light-receipt system with current bias circuit and pre-amplifier for use

Growing community of inventors

Yokohama, Japan

Akihiko Yasuda