Device
performance
results
Laser
parameter
extraction
System
performance
results
SPICE
equivalent
circuit
OptSimLaserMOD
Vf
Rs Lb
01001 LD
Cp
Software&Computing
Laser modeling software requires
minimal parameter knowledge
JIGESH K. PATEL, PABLO V. MENA, AND ENRICO GHILLINO
Optical light sources and the
transmission medium are two of the
most important elements in modeling a fiber optic system, each having
a significant impact on receiver design
and system performance. Singlemode
optical fiber, the most popular choice
of transmission medium, affects the
quality of data transmission through
linear-, nonlinear-, and polariza-tion-related effects that are commonly modeled with the nonlinear
Schrödinger equation. 1
In the majority of cases, fiber man-
ufacturers provide sufficient informa-
tion such as wavelength-dependent attenuation and dispersion characteristics,
the area and nonlinear index of the core, and the polarization mode disper-
sion coefficient to enable the prediction of transmission impairments with
very good accuracy. 2 Unfortunately, the same cannot be said about optical
sources such as edge-emitting semiconductor lasers and vertical-cavity sur-
face-emitting lasers (VCSELs). Even when datasheets provide a number of
useful parameters, manufacturing variances make it very difficult, if not im-
possible, to accurately model laser behavior.
If the model of the laser is flawed, design of the driver circuit and estimation
of system performance are very likely flawed as well. As a result, Synopsys focuses on the accurate system-level characterization and modeling of semiconductor lasers. First, we outline a mixed-level design flow, starting with device-level laser modeling and using it to estimate system behavior. Next, we discuss
a datasheet-based approach to describe a physical laser. Finally, we detail the
modeling of laser behavior based on measured characteristics.
Mixed-level modeling
RSoft LaserMOD is a commercial semiconductor-laser modeling tool used by companies
that manufacture their own
lasers in-house or have access
to all data on the laser geometry and material characteristics. 3 In this case, LaserMOD
provides a parametric comput-er-aided design (CAD) interface for the layout and simulation of active photonic devices
such as Fabry-Perot, distributed feedback, and distributed
Bragg reflector semiconductor
lasers, as well as VCSELs and
silicon modulators.
LaserMOD accounts for the
optical, electrical, and thermal properties of these devices, including complex effects
such as spatial hole burning
FIGURE 1. A mixed-level design flow can incorporate device-level laser modeling results within
the context of system- and circuit-level simulation.
