LASER DIODE DRIVING SYSTEM

PURPOSE:To output an NRZ optical signal whose half value width is 100% by taking logic operation to a retarded NRZ signal and the original NRZ signal and inputting a signal whose half value width is increased by 100% or above to the driving circuit of a laser diode. CONSTITUTION:A variable delay circuit 1 retards an inputted NRZ electric signal for an optical time and is connected to the 2nd input terminal of an OR circuit 2. A laser diode LD 3 emits a coherent light with the strength responding to the current to be inputted, the output terminal of the circuit 2 is connected to an LD driving circuit 4 driving the LD 3. The circuit 4 is a differential current switching circuit, an NRZ signal is inputted to the base of one TR 1 and a voltage VREF1 being the center level of the NRZ signal inputted to the base of the TR 1 is fed to the base of other TR 2. A 3rd TR 3 is a TR to supply a bias current and the voltage VREF2 to set the bias current is applied to the base.