Generation of a CW Local Oscillator Signal Using a Stabilized Injection Locked Semiconductor Laser

We explore the technique of injection locking a semiconductor laser with a portion of the received optical signal to regenerate a local oscillator for eventual use with a homodyne receiver. In addition, we show that the injection locking process can be electronically stabilized by using the Modulation Transfer Ratio (MTR) of the slave laser as a monitor, given either a DFB or Fabry-Perot slave laser. We show that this stabilization technique maintains injection lock (given a locking range of ~1 GHz) for laser drift much greater than what is expected in a typical transmission system. In addition, we explore the quality of the output of the slave laser, and analyze its suitability as a local oscillator signal for a homodyne receiver.