Abstract: A microcontroller-based controller executes interleaved DC bias and gain control routines using monitored values of the monitored photocurrent output signal of a Mach-Zehnder laser modulator to derive a gain setting for the modulation drive signal and a bias level setting for the DC bias level, without tuning or adjustment. Subsequent to convergence of the gain and bias level settings, the control unit may repetitively interrupt and restart the DC bias and gain control routine at intervals that are staggered in a random time fashion, to achieve spectral dispersion of the gain and bias level settings, and provide insensitivity to periodic environmental noise.

Abstract: A single reference tone/frequency-based control scheme adjusts the DC bias voltage and modulation signal drive level to an external X-cut lithium niobate Mach Zehnder modulator, in accordance with phase quadrature components of the output of the single tone frequency generator. A pair of phase quadrature feedback loops are coupled through a loop filter of a common feedback path electo-optically coupled to monitor the optical output of the laser modulator. Quadrature-phase (Q) and in-phase (I) frequency components are respectively coupled to respective Q and I channel phase detectors, coupled to synchronous demodulators for the Q and I channel feedback loops. The phase detectors produce respective error voltages that close Q and I channel feedback loops and control the optical extinction ratio and DC bias voltage of the modulator.

Abstract: A dual pulse width modulated driver controls the operation of a thermo-electric cooler for stabilizing the operating temperature of a laser. The pulse width modulator has complementary outputs coupled to control inputs of dual pairs of complementary polarity electronic switching elements, that are coupled in circuit between first and second power supply terminals, and a pair of output nodes. The output nodes are coupled in common through a low pass filters to drive terminals of a thermoelectric cooling element. The thermal output generated by the thermoelectric cooling element is coupled to the laser. The thermal output of the cooling element is monitored by a temperature sensing element mounted with the laser and provides an output voltage in linear proportion of its thermal input. This output voltage is fed back through a temperature control servo loop to a differential summing circuit, which is also coupled to receive a reference voltage used to control the duty cycle of the pulse width modulator.

Abstract: A microcontroller-based controller executes interleaved DC bias and gain control routines using monitored values of the monitored photocurrent output signal of a Mach-Zehnder laser modulator to derive a gain setting for the modulation drive signal and a bias level setting for the DC bias level, without tuning or adjustment. Subsequent to convergence of the gain and bias level settings, the control unit may repetitively interrupt and restart the DC bias and gain control routine at intervals that are staggered in a random time fashion, to achieve spectral dispersion of the gain and bias level settings, and provide insensitivity to periodic environmental noise.