Numerical modeling is of paramount importance for the design and characterization of optical transmission systems, including metro networks, long-haul and ultra long-haul terrestrial and submarine communication systems, wavelength-division multiplexed systems, all-optical networks, soliton systems, and optical interconnects. In system simulators, the properties of individual photonic devices (components) can be modeled at different levels, ranging from "black-box" models to measurement-based models and detailed physical models. In addition, in some cases the system simulators are interfaced with device-level modeling software.
Often, when field trials and even laboratory experiments are too expensive, such as in the case of long-haul and submarine systems, numerical simulations play a key role in system design. Existing simulation tools provide a wide range of capabilities, including various advanced input signal modulation formats, realistic sources of noise, dispersion variations in fiber links, nonlinear, dispersive and polarization effects, facilitating detailed studies of signal propagation in realistic transmission systems. Many important output characteristics, such as eye-diagram calculations, BER and Q-factor evaluations, are readily available and can be directly compared to experimental data. Importantly, many individual physical effects and system components can be modified or turned on and off independently in numerical experiments, thus enabling the designer to develop an insight into the impact of various effects on overall system performance, a feature usually unattainable in real experiments.
This section includes a number of freely available (FOCSS developed at TRLabs, LIGHTSIM by Softronix Software, SIMFOCS developed by Dr. Geckeler) and commercial (ModeSYS by RSoft, OptiSYSTEM by Optiwave, OptSim by RSoft, PHOTOSS distributed by P. I. Systemtechnik Jens Lenge, VPItransmissionMaker™ WDM by VPIsystems) packages for transmission system modeling. These packages include extended libraries of photonic components for transmitter, communication channel (fiber/waveguide), amplifier, and receiver design, and extensive output parameter capabilities.
In addition to general system simulation software, some software providers (OptiSYSTEM Amplifier Edition by Optiwave, VPIcomponentMakerTM Optical Amplifiers by VPIsystems) offer specialized tools for modeling various types of optical amplifiers, including Erbium Doped Fiber Amplifiers (EDFAs), Semiconductor Amplifiers (SOAs), Raman Amplifiers, and doped fibers. These tools facilitate amplifier design and performance optimization by including a variety of important metrics and detailed models for physical effects, specific to a particular type of amplifier, such as noise figure calculations, gain flattening, spectral hole burning, concentration quenching, and excited-state absorption in EDFAs, or nonlinear effects in doped fibers. Optiwave also offers an OptiSYSTEM Multimode Edition that facilitates the design, analysis and simulation of multimode fiber communication systems primarily used for short-distance communications, such as Local Area Networks (LANs).
Another specialized modeling tool that compliments the VPIsystems general system simulator is active photonics software (VPIcomponentMakerTM Active Photonics), allowing the investigation and design of active photonic circuits and advanced semiconductor lasers, including integrated tunable lasers, high-power lasers, fast switches, optical logic, modulators, 2R and 3R regenerators, among others. Finally, VPIsystems also provide a tool for designing the so-called "last mile" (VPItransmissionMakerTMCable Access).
LIGHTSIM (previously PC-SimFO) is an easy to use simulator for modeling optical fiber communication systems using a PC.
Capabilities:
Wide range of photonic device models available as icons
Models operate over a wide and continuous spectral bandwidth
Model parameters can be modified easily
Fast and stable algorithms
A complete user friendly hierarchical topology layout environment
Block-oriented waveform simulation
Instrumentation to measure, signal and noise ratio, optical and RF spectra, eye diagrams, bit error rates and optical meters
Simulation includes crosstalk, dispersion, nonlinearities, variations in component parameters
Signal waveforms, eye diagrams, and spectral plots may be viewed at any point in link
Bit error rate (BER) curves may be plotted vs. received optical power or any parameter or user variable in the link
LIGHTSIM library has almost all critical photonics components, including a variety of passive and active optical and electrical component models, semiconductor lasers like multimode Fabry-Pérot lasers and monomode DFB lasers, visualizers to monitor the signal state in the simulation (e.g. eye-diagrams, power meters, etc.)
ModeSYS is a software supporting the design, analysis, and simulation of multimode optical communication systems.
Capabilities:
A variety of launch conditions is supported and the system impact of the launch conditions can be studied since the excitation of the modes in multimode communication systems has a strong effect on the system performance
Temporal and spatial characteristics are modeled
The differential mode delay of a fiber with a given index profile and the effective modal bandwidth of the fiber can be investigated
Effecive integration of system-level and device-level modeling approaches to combine the speed of system-level simulations with the accuracy of device level simulations
A very straightforward system-level analysis
The signal representations in the simulations include both temporal waveforms and spatial modes
Simulations of single- and multi-channel systems utilizing multiplexing techniques such as coarse wavelength division multiplexing are supported
ModeSYS also includes an internal mode solver to enable the simulation of arbitrary index profiles in multimode fibers
ModeSYS also provides interfaces to device-level tools such as BeamPROP for more detailed device-level modeling of multimode components in conjunction with the system simulations
For custom model development, ModeSYS also provides interfaces to third party tools such as MATLAB® and an application programming interface (API) for custom user model development in languages such as C/C++
Applications:
System-level analysis of standardized multimode optical communications technologies such as 1 Gb and 10 Gb Ethernet and Fiber Channel, as well as the study of proprietary optical data communication platforms
Semiconductor lasers
Semiconductor lasers
Multiplexing
Multimode fiber with arbitrary index profiles and profile perturbations
Fiber/fiber and fiber/receiver coupling and offsets
Transceiver/fiber pair encircled flux (EF)
Fiber differential mode delay (DMD)
Modal and chromatic dispersion (MD, CD)
Inter-symbol interference (ISI)
Effective modal bandwidth
Signal analysis
Signal spectra
BER estimation
Related publications:
R. C. J. Hsu et al., "Capacity enhancement in coherent optical MIMO (COMIMO) multimode fiber links," IEEE Commun. Lett. 10, 195 (2006).
R. C. J. Hsu et al., "Capacity enhancement in coherent optical MIMO (COMIMO) multimode fiber links," IEEE Commun. Lett. 10, 195 (2006).
J. Morikuni et al., "System simulation of multiplexing methods for multimode local area networks," OFC/NFOEC 2005 Technical Proceedings, March 2005.
G. Shaulov and Y.Sun, "DMD simulations based on scaled/non-scaled index profiles and comparison with Cambridge model results," IEEE 802.3aq Interim Meeting, Ottawa, Canada, September 2004.
G. Shaulov and B. Whitlock, "Multimode Fiber Communication System Simulation," IEEE 802.3aq Plenary Meeting, Portland, Oregon, July 2004.
OptiSystem is optical communication system and amplifier design software that enables users to plan, test, and simulate almost every type of optical link in the transmission layer of a broad spectrum of optical networks.
OptiSystem Amplifier Edition allows optical component and system design engineers to determine the tradeoffs between EDFAs, EYDFs, EYDWs, YDFs, SOAs and Raman amplifiers. Evaluate cost and performance by calculating how metrics such as minimum output power, maximum noise figure, maximum gain ripple, and minimum pump power depend on device specifications such as pump wavelength range, passive component losses, component costs and much more. The component library includes single or double-clad fibers, static and dynamic amplifiers.
Applications:
Single and multi-stage EDFA design for CATV or WDM networks
Reflective, split-band and bi-directional amplifiers
OptiSystem Multimode Edition facilitates the design, analysis and simulation of multimode fiber communication systems. By temporal and spatial propagation of signals OptiSystem MMC can handle system level analysis of communication technologies including 10 GB Ethernet.
Capabilities:
A library of multimode lasers and transmitters that generate transverse output fields with different profiles, including Laguerre-Gaussian and Hermite-Gaussian profiles
Multimode fiber models, including Parabolic-Index and Measured-Index profile Advanced mode-solvers allows for calculation of coupling coefficients and modal delays for different fiber profiles
Integration with OptiFiber that allows the users to design fibers and import the refractive index profile into OptiSystem
Spatial couplers that allow for simulation of the rotation, shifts and tilts between different components, e.g. laser-fiber coupling
A library of multimode photodetectors and receivers that include the effects of losses due to optical misalignments
Lenses and aperture components that allow for manipulating the spatial distribution of optical signals
Encircled Flux Analyzer that allows for calculating Average Radial Intensity and Encircled Flux
OptSim is a modeling and simulation environment supporting the design and the performance evaluation of the transmission level of optical communication systems.
Applications:
DWDM/CWDM amplified (e.g. EDFA, Multipump Raman, SOA, Hybrid amplifier) systems
FTTx/PON systems
OTDM/OCDMA systems
CATV Digital/Analog systems
All-optical networks
Ultra long-haul terrestrial and submarine systems
Soliton systems
Optical LANs
Optical interconnects
Free-space optics systems
Link optimization: power budget, dispersion map, gain balancing, tailoring of pulse shape and chirp, transmitter pre-emphasis, amplifier positioning
Spectral occupancy and gain optimization through Multipump Raman Amplification
Edge design and validation: channel spacing, number of supported channels, transmission rate, enhancement of modulation techniques, coherent systems
Monte-Carlo simulation to evaluate system sensitivity to stochastic phenomena (e.g. polarization mode dispersion, pattern effects, dispersion statistical variation, ASE noise)
Research novel modulation schemes
System sensitivity evaluation
Laser driver design optimization
Analysis of power transients due to adding and dropping of channels in optical amplifier chains
All-optical gain control design for amplifier chains
Related publications:
Lyubomirsky and C.-C. Chien, "Experimental demonstration of an optimized optical RZ-duobinary transmission system," IEEE Photon. Technol. Lett. 17, 2757 (2005).
R. P. Scott et al., "An eight-user time-slotted SPECTS O-CDMA testbed: Demonstration and simulations," J. Lightwave Technol. 23, 3232 (2005).
K. K. Y. Wong et al., "Temperature control of the gain spectrum of fiber optical parametric amplifiers," Opt. Express 13, 4666 (2005).
Lyubomirsky and C.-C. Chien, "DPSK demodulator based on optical discriminator filter," IEEE Photonics Technology Letters, vol. 17, no. 2, pp. 492-494, February 2005.
V. Baby et al., "Experimental demonstration and scalability analysis of a four-node 102-Gchip/s fast frequency-hopping time-spreading optical CDMA network", IEEE Photon. Tech. Lett. 17, 253 (2005).
P. Bravetti et al., "Chirp-inducing mechanisms in Mach-Zehnder modulators and their effect on 10 Gb/s NRZ transmission studied using tunable-chirp single drive devices," J. Lightwave Technol. 22, 605 (2004).
J. Mendez et al., "Design and performance analysis of wavelength/time (W=T) matrix codes for optical CDMA," J. Lightwave Technol. 21, 2524 (2003).
G. S. Kanter et al., "Electronic equalization for enabling communications at OC-192 rates using OC-48 components," Opt. Express 11, 2019 (2003).
Commercial software sold by P. I. Systemtechnik Jens Lenge.
PHOTOSS, the Photonic System Simulator, is a simulation software for the design and analysis of fiber optic point-to-point links and transmission systems on the physical layer.
Capabilities:
Flexible component library includes a large number of simulation models and pre-defined parameter sets
Extendable by user-defined components with customized parameters
A number of component models are provided at different levels of complexity, i.e. there is a choice physical models to gain deep insight in the phenomena that influence a transmission, or simplified models for a quicker components simulations An intuitive GUI
The embedded programming interface enables the integration of user-defined component models and simulation algorithms with full control over their respective parameters
Investigations of the effects of noise (ASE-shot noise, ASE-ASE beat noise, ASE-channel beat noise, channel-shot noise and thermal noise) on system performance
Dispersion effects (group-velocity dispersion and third-order dispersion)
Nonlinear effects, including self-phase modulation, cross-phase modulation, and four-wave mixing
Evaluation of system performance based on BER calculations, Q-factor, path analysis
M Windmann et al., "PHOTOSS: the simulation tool for optical transmission systems," Proceedings of SPIE 5247, Optical Transmission Systems and Equipment for WDM Networking II , Ed. by Werner Weiershausen, Achyut K. Dutta, Ken-Ichi Sato, 51, (2003).
Free software developed by Dr. Siegfried Geckeler.
SIMFOCS is a program for simulating signal transmission properties of fiber-optic communication systems of various kinds.
Capabilities:
Structure: the simulator core, a graphics program, and a text editor
These parts can work independently, but they can also communicate in various ways
Text editor allows the automatic conversion of SIMFOCS results for use in other programs, or vice versa the use of results of other programs in SIMFOCS calculations
As input signals, transfer functions or measured properties can optionally enter/exit SIMFOCS in the form of numerical tables
Mathematical models, available for all relevant components of fiber-optic transmission systems, can be divided in three groups:
Signal source and optical transmitter
Optical transmission medium
Photo receiver
Models include signal generator, laser diode, external modulator, single-mode fiber, graded-index fiber, attenuator, erbium-doped fiber amplifier, optical filter, photodetector, low-pass filter, and binary decider, as well as models of the noise sources that are active in some of these components
Simulations are not limited to binary digital signals
For simulating a transmission link, the models of all its components are connected together: The signal generator produces a signal with desired bit rate, bit pattern, pulse shape, and amplitude, which feeds a directly modulated laser diode, or the external modulator of a CW laser diode
For WDM systems multiple optical transmitters with different wavelengths can be defined, whose combined optical power is fed into the first fiber
Output characteristics include bit-error rate calculations, the eye diagram or the optical power
The effects of crosstalk and jitter can be studied
VPItransmissionMakerTM WDM is a tool for the design of new photonic systems including link and all-optical networks.
Capabilities:
Over 300 design templates are provided, with regular updates on the Optical Systems Forum An unrivaled range of photonic and electronic modules supports almost every system concept
The graphical interface allows almost any topology to be built and simulated using Sample and Block modes, both in unidirectional and bidirectional simulations.
Advanced multiple-signal representations and sophisticated numerical models ensure speed and accuracy
Interactive Simulation, Design-Assistants, simulation scripting, data import with automatic file format conversion and MATLAB/DLL/Python cosimulation streamline and capture design processes
Technical marketing is supported, by providing a dynamic environment to design, evaluate, demonstrate and compare the technical and cost superiority of solutions
Applications:
Comparison of upgrade strategies for Dense WDM with high bit rate systems
Development of Ultra Long Haul amplified systems and submarine systems
Selection of technologies for Metro-WDM and digital access networks
Assess to component performance in a systems context to develop component specifications
Fine tuning of link designs using Design Assistants for synthesis and analysis
Mitigation of PMD effects in 40 Gbit/s systems using compensators and novel modulation formats
Exploration of several Tbit/s systems using C, L and S band windows
Evaluation of crosstalk in Super-Dense WDM metro networks
Simplification of the architecture of an access network by using OSSB sub-carrier multiplexed data
Extension of transmission distance of 40 Gbit/s OTDM systems using partial ptical regeneration
Upgrading of the backbone network with ULH 640 x 2.5, 160 x 10, 80 x 40 RZ/CRZ/Soliton systems
Maximization of the capacity of the fiber plant using bidirectional transmission.
Related publications:
X. Chen et al., "Improvement of Dispersion Tolerance Using Phase-Modulated NRZ Signals in 40-Gb/s Transmission Systems, "IEEE Photonics Technol. Lett. 18, 37 (2006).
Cable access systems offer a ready-made solution to the last mile. VPItransmissionMaker™ Cable Access allows the benefits and limitations of fiber in access systems to be explored in detail.
Capabilities:
Flexible signal-processiing modules
Substantial library of photonic components
Almost any mixed analog and digital access technology can be investigated
Data presented as waveforms, eye-diagrams, constellations and spectra (optical and RF)
Industry standard measurement tools for analysis of Q, BER, CTB, CSO, 3-IM and SNR
Applications:
Investigations of mixed transmission formats such as baseband digital plus SCM
analog plus QAM digital, including upstream path options. Use the
Extensive library of signal processing modules to simulate novel
modulation and demodulation schemes
Investigations of transmitter and modulator performance requirements, including directly modulated laser clipping and memory effects
Calculations of fiber-induced signal degradation including XPM, FWM, Raman,
dispersion, multiple reflections and interaction with the source
Evaluation of upstream-data DWDM systems using frequency stacking or high-
speed digital-analog conversion
Identification of critical design parameters including dispersion, amplifier gain-tilt,
demultiplexer performance, amplifier noise, Rayleigh backscattering and
multi-path interference
Development of antenna-remoting and radar applications, using optical millimeter-wave signal generation, up-conversion and mixing
VPIcomponentMaker™ Active Photonics is an integrated design environment for active photonic circuits and advanced semiconductor lasers.
Capabilities:
Unique large-signal bidirectional-signal time-domain algorithms are used
Can predict the complex nonlinear dynamics of multi element circuits and lasers over wide optical bandwidths
Applications:
Designing of integrated tunable lasers, based on DBR/Active/DFB/GC/Passive sections for tuning dynamics and stability
Investigations of optimum mixes of gain, loss and index coupling for spectral stability, feedback insensitivity and power in high-power lasers
Enhancement of modulation speed using MQW materials, gain coupling and optimized drive waveforms for high-speed lasers
Investigations of the spectral stability and modulation dynamics of bulk-grating or fiber Bragg grating stabilized lasers
Characterization of anti-reflection coating specifications by simulating the full interaction of laser and modulator
Simulations of active, passive, ring and hybrid mode-locked lasers, to determine amplitude and timing stability of ultra-fast sources
Development of fast switches, optical logic, modulators, detectors, edge detectors, gain flatteners, semiconductor line amplifiers and semiconductor preamplifiers
Comparison of XPM, XGM and FWM wavelength conversion technologies for speed, noise and conversion range
Development of 2R and 3R regenerators and optimize their speed, transfer characteristics and induced chirp
Simulations of full dynamics including spectrum evolution, dynamic/adiabatic/SHB chirp, turn-on jitter, intensity noise and patterning due to deep modulation
Predictions of instabilities due to physical processes, such as spatial-hole-burning in lasers
VPIcomponentMaker™ Optical Amplifiers is a software for modeling multi-band, multi-stage, hybrid, Raman, doped-fiber and doped-waveguide amplifiers.
Capabilities:
Highly-advanced optical amplifier models incorporate super-stable and efficient algorithms
The same models can be used in systems simulations using the same GUI, as they incorporate advanced signal representations including multiple sampled bands, noise-bins and parameterized signals
Alternatively, doped amplifiers (fiber and waveguide) can be automatically characterized and converted into pump-power dependent Black-Box models for rapid systems simulations of gain-controlled amplifiers
Applications:
Simulations using an advanced bi-directional Raman model with full signal-pump-noise power interactions (stimulated and spontaneous Raman scattering). Includes Kerr nonlinearity for systems simulations
Importing of an OTDR trace representing local insertion loss and reflections into the Raman fiber model for true characterization of a transmission link
Modeling of sophisticated EDFAs with flexible input parameter specifications including Giles parameters or gain and absorption cross-sections, refractive index and doping profiles (includes a circular waveguide solver) or wavelength-dependent overlap factors, wavelength-dependent Rayleigh backscatter and background loss, two or three-level parameters.
Sophisticated algorithms to simulate ultra-long L-band amplifiers
Investigations of concentration quenching, excited-state absorption, gain temperature-dependence, and spectral hole burning in EDFAs
Designing of doped Waveguide amplifiers from waveguide dimensions upwards, and including excited-state absorption, up conversion, cross-relaxation, and pair-induced interactions in co doped waveguides
Stimulations of full interaction between amplifier stages, including pump reuse and ASE-pumped amplification
Characterization of amplifier performance and BER estimation using specialist instrumentation, including an Amplifier Test Set
Abstract doped-fiber designs to Pump-Power dependent Black-Box models
Investigations of gain flattening, pump reuse and multistage amplifier design with a wide range of passive component models
Implementation of gain or power control schemes using feedback loops and control circuits
