Laser diode protection circuit

摘要

A laser diode protection circuit includes an input connected to receive the RF amplitude modulating signal. A second RF amplifier is connected to amplify the received RF amplitude modulating signal and to put out an amplified signal. A sensing element such as differential amplifier or Schmitt trigger is connected to put out a control signal when the amplified signal exceeds in amplitude a reference level. A switching element preferably includes a series PIN diode network having a PIN diode connected in parallel in reverse conduction order across the laser diode. The switching arrangement is responsive to the control signal and effectively swamps or diverts the forward conduction current away from the laser diode thereby causing it to become reverse biased. A reverse bias connection is made to the PIN diode network for causing the PIN diode across the laser diode to be reverse biased whenever the control signal is not present thereby presenting the high impedance across the laser diode and also protecting the laser diode against excessive reverse bias potentials and electrostatic discharge protection. The switching element preferably includes a switching transistor having its control element connected to receive the control signal.