BIAS CURRENT DISPLAY SYSTEM OF SEMICONDUCTOR LASER

• Main Authors: ENDO TAKEMI, ARAI MASANORI
• Format: Patent
• Language: English
• Published: 26.05.1986
• Subjects: BASIC ELECTRIC ELEMENTS; DEVICES USING STIMULATED EMISSION; ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; TRANSMISSION

PURPOSE:To detect deterioration of a laser diode LD without being affected by temperature by using an element whose characteristic changes by temperature and a differential amplifier so as to compensate the change in a bias current of the LD due to ambient temperature. CONSTITUTION:A voltage drop VB across a resistor 10 by a bias current IB of the LD2 is amplified by an amplifier 11, the waveform is a voltage I due to temperature change and fed to a non-inverting input of the differential amplifier 16. The voltage divided by a resistor 22 and a thermister 18 is inputted to a differential amplifier 17, a voltage II having a waveform in response to the temperature change is outputted from the amplifier 17 and fed to an inverting input of the amplifier 16 via voltage dividing resistors 14, 15, and the amplifier 16 outputs a difference voltage IV between the voltages I and II. The voltage IV corresponds to a change voltage III due to secular deterioration of the LD2, inputs an output of the amplifier 16 to an A/D converter 20 via a variable resistor 19, the converted digital value of displayed on a digital display device 21. In setting the voltage at the initial state to a prescribed value by the resistor 19, the secular deterioration of the LD not affected by temperature change is detected by the display device 21.