Optical Interlocking of Mode-Locked Lasers in Coherent Communication

With the progress of generating more compact, efficient, and high bandwidth mode-locked lasers (MLLs), many novel applications have risen. Such advanced applications demand the acquisition of the cross-correlation (XCORR) between two MLLs for examination and interlocking two lasers. As opposed to the common techniques for acquiring the XCORR via non-linear crystals as effective multipliers, here, employment of conventional optical communication on-chip integrated coherent receiver (ICR) peak detector (PKD) circuit is proposed, analyzed, and demonstrated. A rigorous connection between the PKD circuit and the optical XCORR is derived, along with the expected response of the circuit to MLL inputs. Two interlocking techniques are suggested and examined: a power proportional-integral (PI) and extremum seeking (ES). In addition, inclusive experiments with 40 GHZ MLLs verifying the analytical predictions are conducted, and successful interlocking is demonstrated. The presented approach enables the efficient realization of various interlocking and examination applications using low-cost, compact, low-power pulse lasers.