Apparatus and method for controlling the optical output power of a laser in an optical transmitter (TX)

摘要

A semi-open feedback loop optical output power control apparatus and method are provided for use in an optical TX. The apparatus and method enable input data signals having content frequencies that are below the cutoff frequency of the optical output power monitoring and control feedback loop to be utilized. This is accomplished at least in part by opening and closing (i.e., is disabling and enabling) the feedback loop based on whether or not one or more transitions in the input data signal to the optical TX from a logic 0 to a logic 1, or vice versa, are detected within a predetermined timing interval. In addition, the apparatus and method provide these and other advantages without causing the optical TX to have an increased link startup settling time period. The feedback loop has a low pass filter (LPF) that has a selectable bandwidth. The bandwidth of the LPF is set to a high bandwidth at startup to enable shorter link startup settling time periods to be achieved by the TX and is set to a low bandwidth at a later time to enable the feedback loop to cause more accurate adjustments to the optical output power of the laser to achieve a better bit error rate (BER).