The integration of laser source and Mach-Zehnder (MZ) modulator offers benefits arising from cost
effective packaging and wavelength-independent behavior making it an ideal transmitter concept for WDM systems. Design
tolerances such as the residual optical feedback from the modulator output facet need to be studied carefully as they
introduce frequency chirp and relaxation oscillation and thus limit the modulation performance in high bit-rate
This application illustrates a model of a voltage-controlled InP MZ modulator that accounts for the carrier dynamics
inside the modulated InP region. Internal loss and gain are changed dynamically according to . With this approach
it is possible to modulate voltage, current and phase simultaneously.
The schematic for the integrated laser MZ modulator is shown in
. A MQW DFB laser
acts as a CW source; its optical spectrum is represented in
Two Y-splitters are used to form the two branches of the MZ modulator. At each branch, a voltage-control module sets
the values of the two chosen parameters (internal loss and gain) according to the applied voltage . The injection
current passes through the module with no changes. The phase control module determines the dependence of phase shift
on the input electrical signal.
shows the voltage drive
signal as well as the optical power and chirp of the modulated output signal. The carrier density variation inside the quantum
wells is shown in .
Keywords: Integrated Laser Mach-Zehnder Modulator, Carrier Dynamics, MQM DFB Laser
Similar demonstrations are available in VPIComponentMaker Photonic Circuits and on the VPIphotonics Forum.
 P.Brosson and P.Delansay, J. Lightwave Technol. 16, 2407 (1998)