Optical transmission device and optical transmission system using the same

An optical transmission system comprising a plurality of optical transmission devices each for converting a transmission electrical signal into a transmission light signal, a multiplexer for multiplexing a plurality of transmission light signals having different wavelengths thereby generating and producing an optical wavelength division multiplexing light signal, an optical demultiplexer for demultiplexing said optical wavelength division multiplexing light signal into a plurality of receiving light signals having different wavelengths, respectively, and a plurality of optical receivers for converting said receiving light signals into receiving electrical signals, respectively, wherein said optical transmission device comprises:

• a current source for outputting a drive current;
• a semiconductor laser for converting the drive current into a stimulated emission light and outputting the same;
• a drive circuit for converting a transmission data signal into a modulation control signal and outputting the same;
• an optical modulator for receiving said stimulated emission light and said modulation control signal and producing and outputting transmission signal light by changing an amount of transmission of said stimulated emission light according to said modulation control signal;
• and
• a shading element for receiving said transmission signal light and a shading control signal for interrupting light emission and interrupting the transmission of said transmission signal light according to said shading control signal.

An optical transmission device comprising:

• a current source for providing a drive current;
• a semiconductor laser connected to receive the drive current and in response emit stimulated emission light;
• a drive circuit connected to receive a transmission data signal and in response to provide a control signal;
• an optical modulator positioned to receive the stimulated emission light and connected to receive the control signal and in response change transmission of the stimulated emission light thereby generating a transmission light signal a shading element for receiving the transmission signal light and a shading control signal for interrupting the transmission signal light according to the shading control signal;
• shading element for receiving the transmission signal light and a shading control signal for interrupting the transmission signal light according to the shading control signal;
• a photo detector for detecting the stimulated emission light and in response provide an optical strength detection signal;
• an optical strength setting circuit for producing and outputting an optical strength setting signal;
• and
• an optical strength stabilization circuit for comparing the optical strength setting signal with the optical strength detection signal and thereby provide the optical strength setting signal.