Simulation Of Optical Systems Research Articles

Quantum simulations of optical systems

Within the framework of a two-dimensional microscopic, purely quantum mechanical model, we analyse the dynamics of single-photon wave packets interacting with optical elements (beam splitters, mirrors), modelled as systems of two-level atoms. That is, we utilize a two-dimensional cavity to simulate the quantum behaviour of simple optical components and networks made thereof. The field is quantized using the canonical procedure, and only the basis states with one unit of excitation are included. This, however, covers linear optical phenomena. The field is taken to interact with localized atoms through a dipole interaction. Using different configurations of atoms, and choosing their frequencies to be resonant or off-resonance, we can model mirrors, beam splitters, focusing devices and multicomponent systems. Thus we can model arbitrary linear networks of optical components. We show the time evolution of a photon wave packet in an interferometer as an example. As the state of the field is known at each instant, spectral properties and spatial coherence can immediately be obtained from the simulations. We also know the states of the two-level atoms constituting the components, which allows us to consider their quantum behaviour. Here the decay of an excited atom into the vacuum state of the electromagnetic field in the two-dimensional cavity is studied.

Simulation of single-channel optical systems at 100 Gb/s

With the help of a computer simulation, we have investigated the conditions under which the transmission of light pulses through optical fibers may be possible over thousands of kilometers at a bit rate of 100 Gb/s. Employing an amplifier spacing of only 20 km, nonreturn-to-zero (NRZ), return-to-zero (RZ), and dispersion-managed solitons (DMSs) may all be useful provided that certain additional conditions are met. These include dispersion management by means of a dispersion map, a reduced dispersion slope, low polarization mode dispersion (PMD), and in-line optical filters.

Estimation of multiple-quantum-well laser parameters for simulation of dispersion supported transmission systems at 20 Gbit/s

In this paper, a set of multiple-quantum-well (MQW) laser parameters is proposed for simulation of optical transmission systems at 20 Gbit/s. The parameters have been estimated by joint fitting of a small signal intensity modulation (IM) response model to five measured IM response curves of a strained layer MQW laser, using the Levenberg–Marquardt method. Good agreement between theoretical and experimental curves was obtained. Using these laser parameters, we have assessed the performance of dispersion supported transmission systems at 20 Gbit/s incorporating an erbium doped fibre amplifier (EDFA) or a semiconductor optical amplifier (SOA) as a booster amplifier. It is shown that the use of a SOA, with an unsaturated gain of 20 dB, improves the system performance for link lengths ranging from 8 to 20 km of standard single-mode fibre (SMF) due to partial chirp compensation in the SOA, and degrades the system performance between 1.2 and 2.5 dB for link lengths ranging from 30 to 50 km. The increase of the unsaturated gain of the SOA from 20 to 25 dB is only advantageous for link lengths ranging from 8 to about 12.5 km where a small performance improvement, less than or equal to 0.8 dB, is observed. The influence on the system performance of an increase of the laser line width enhancement factor from 2 to 3 is also investigated.

Long Haul System Issues with Bragg Fiber Grating-Based Dispersion Compensation

Using an accurate optical system simulation for Bragg fiber grating dispersion compensators, the fundamental limitations on system performance incurred by these devices operating in reflection and transmission, are studied. When the devices are operating in reflection, the limitation on system performance is due to group delay and reflectivity ripple. When they are operating in transmission, the limitation on system performance is due to dispersion slope of the grating. A range of issues, including the impact on system performance of ripple period and amplitude, concatenating many gratings, and system bit rate are considered. The results show that systems based on WDM with lower channel line rates are the more resilient to limitations introduced by these devices than high-speed TDM systems.

Simulation of Optical Fiber Transmission Systems Using SPW on an HP Workstation

In this article, an intensity modulation-direct detection (IM-DD) optical fiber transmission system is simulated and investigated using a signal processing worksystem (SPW) on a Hewlett-Packard (HP) workstation. The optical fiber transmission system simulated includes a laser diode source, a single-mode fiber and a positive-intrinsic-negative (p-i-n) photodiode receiver model. Simulation methods are pre sented on the optical source waveforms, fiber attenuation and dispersion, and receiver noise. The end-to-end performance of a typical trans mission system is also presented. In the simula tion, models can be made as detailed as neces sary and computer waveforms can be compared directly to measured waveforms. Measured data can be used to accurately characterize functional components, such as sources, fibers and detectors. The impact of noise on the per formance of the transmission system can be observed. SPW software and its usage on HP workstations are introduced.

Simulation and experimental verification of a 10-Gb/s NRZ field trial at 1.3 μm using semiconductor optical amplifiers

Optical system simulation of a field trial at 1.3 μm is presented, including attenuation, fiber dispersion, fiber nonlinearity, amplification by in-line semiconductor optical amplifiers (SOAs), amplifier noise and filtering. For the first time, simulation results in terms of saturation effects due to SOAs are compared with measurements obtained during a field trial in the network of the Deutsche Telekom, and show very good agreement.

Communication systems interactive software (comsis): modeling of components and its application to the simulation of optical communication systems

comsis, which stands for communication systems interactive software, is a computer-aided-design tool based on a time approach. It allows the design, analysis, and performance optimization of optical transmission systems by use of various optical devices. comsis allows scalar or vectorial simulations, depending on whether the polarization is taken into account. An overview concerning the optical component models is given. A new model of an erbium-doped fiber amplifier allows the user to describe the amplifier through either physical or system parameters by using silicate or fluoride glass fibers or any other material, provided the user can give a file that contains the amplifier's characteristics. The new model of a single-mode fiber allows the user to describe chromatic dispersion through a constant, a function, or a file (given by the user) and to take optionally into account the Kerr and the Raman effects and the polarization-mode dispersion. The simulation tools that are used to characterize the quality of an optical transmission system are also presented. To show the system's full range of capabilities in the optical domain, we describe examples of wavelength-division-multiplexing and soliton-transmission systems.

Spice-based optoelectronic system simulation

spiceis a widely used simulation tool for electrical circuits and systems. When optoelectronic elements, such as lasers, detectors, modulators, etc., and optical elements, such as lenses, gratings, beam splitters, etc., are incorporated into spice, optoelectronic system simulation can be combined with that of electronic systems, facilitating hybrid system design and analysis. We discuss an optoelectronic spice implementation that includes time-, power-, and wavelength-domain behaviors. Examples of optical component simulation and optical interconnect system simulation by use of spice are included and compared with the results from a conventional ray-tracing optical analysis tool.

Recirculating loop for experimental evaluation of EDFA saturated regime effects on optical communication systems

We demonstrate an optical-fiber recirculating loop for experimental simulation of long-haul optical communication systems using cascaded erbium-doped fiber amplifiers (EDFA's) operating in the gain saturation regime. The loop contains sections of dispersion shifted fibers (DSF's), standard fiber, and a set of in-line devices, such as tuning filters, optical amplifiers, polarization controllers, and a variable attenuator. The main results presented here are related to the observation of the effects due to the slow dynamics of the EDFA. We also discuss the validity of using an optical attenuator to simulate an extra length of fiber.

Study of the validity of the numerical code for the simulation of optical systems by means of cross check with analysis and experiments

In this work, we report a check of a numerical code to study system performance with theory and experiments. The theory that is taken into consideration regards soliton propagation in long links in the absence of in-line filters. This choice is due to the fact that, under this propagation condition, several predictions on the effects that limit the soliton propagation can be made. As an experiment we have considered a very successful one, obtained in the CNET laboratories, that also includes the presence of sliding filters. The agreement between the code and theory and between the code and experiment is good. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 16: 229–233, 1997.

A time-domain optical transmission system simulation package accounting for nonlinear and polarization-related effects in fiber

The fast-paced evolution of long-haul and high-bit-rate terrestrial and submarine optical transmission links requires powerful analysis tools that take into account all the relevant phenomena in the fiber. To provide such a tool, we developed a time-domain optical system simulation package, integrated in the TOPSIM simulation environment. The fiber simulation module makes use of the vector form of the propagation equations to account for the quasi-degenerate two-mode (the two polarizations) medium propagation characteristics. This way, all polarization-related effects and their interplay with the other linear and nonlinear phenomena in the fiber can be accurately modeled. In particular, the fiber third-order susceptivity, responsible for all major nonlinear effects, is expressed in its actual vector form, so that nonlinear polarization mode coupling could be accounted for. Conventional birefringence and PMD are generated using appropriate random models. A novel feature of the simulator is that it uses time-domain digital filters to simulate dispersion effects, as opposed to the usual FFT-based algorithms. This approach leads to more efficient computing for a wide range of bandwidth and dispersion values. We present the fiber simulation module in detail. As an example of the use of the simulation package, the analysis of a long-haul two-channel transoceanic WDM transmission system is presented.

Laser turn-on delay and chirp noise effects in Gb/s intensity-modulated direct-detection systems

This paper describes a new IM/DD optical transmission system simulation which incorporates the impact of laser diode stochastic turn-on effects on system performance. Using this simulation, experimentally observed error rate floors, due to inappropriate laser diode biasing, can be theoretically modelled and predicted, for the first time.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Anwendung der Momentenmethode zur Analyse von optischen Überlagerungssystemen

To estimate bit error probability we examine parametric density estimation of the decision signal for efficient simulation of optical heterodyne systems. The parameters are calculated by moment method. From 3 typical realized optical heterodyne systems the power of the procedure is proved. Both, probability density function and bit error rate are compared.

EDFA Custom-Coded Simulation Block for Use in WDM Optical Fiber Communication System Studies

An Erbium-doped fiber amplifier (EDFA) custom-coded block (CCB) for simulation of multichannel amplification has been created in the COMDISCO Signal Processing Worksystem. The resultant model can achieve accurate results with reasonable speed and can be used readily for a wide range of different situations. In the EDFA CCB both forward and backward amplified spontaneous emission (ASE) are considered. Practical application of the block is demonstrated in the analysis of a four node wavelength division multiplexed (WDM) optical fiber ring network using EDFAs to compensate the section losses. We find that for such a system non-uniform sampling of the ASE spectrum offers an advantage for reducing storage requirements and running time of the simulation compared with uniform sampling. The CCB is also used in the simulation of a WDM optical fiber communication system using 9 cascaded EDFAs, which are highly saturated, to compensate for the transmission loss of the fiber. We find that the simulation results of the output signal level and ASE spectrum exhibit the same general pattern as previously published results, demonstrating the applicability of the EDFA CCB for such highly saturated cases.

Simulation of Dispersion Tolerant Long-Haul Optical Fiber Communication Systems with Distributed In-Line Group-Delay Equalizers

Article Simulation of Dispersion Tolerant Long-Haul Optical Fiber Communication Systems with Distributed In-Line Group-Delay Equalizers was published on December 1, 1994 in the journal Journal of Optical Communications (volume 15, issue 6).

DEMOS: state-of-the-art application software for design, evaluation, and modeling of optical systems

A new version of the DEMOS program is presented. DEMOS (design, evaluation, and modeling of optical systems) is integrated dialog software for automatic modeling to estimate and design optical systems with conventional and hologram optical elements. The theoretical principles and the current state of the primary possibilities and application principles of the DEMOS program for optical systems design and simulation on computers are discussed.

Simulation of optical heterodyne single-filter FSK system with line coding

The simulation results for an optical heterodyne single-filter FSK system are presented when two different line-coding plans, viz. alternate-mark-inversion (AMI) and delay modulation (DM), for the laser-driving signal are used to overcome the adverse effect of nonuniformity in the FM response of the transmitting laser.

Computer simulation of electron optical systems

The first major step in computer simulations of electron optical systems is a numerical field calculation. Therefore a survey of field computation techniques is given, where emphasis is put on the boundary-element method. Thereafter follows a discussion of methods to determine electron optical properties of given systems, especially of their aberrations. In this context a new form of the trajectory equation is derived which allows a calculation of aberrations with greater accuracy.

Compensation of thermal defocusing by a three-element adaptive corrector

A numerical simulation of a slow adaptive optical system is reported. It is suggested that the wavefront of a beam can be controlled by a phase corrector with three degrees of freedom: the angle of inclination of the beam and two focusing radii along mutually perpendicular directions. Various algorithms for the control of the corrector coordinates are considered and a study is made of the effectiveness of suppression of thermal defocusing in a moving nonlinear medium.

Optical Sensor System Simulation

To evaluate an optical sensor's performance capabilities for specific system applications, it is often cost effective to simulate the optical component's response to the intended environment and the subsequent effect on the system's performance. High-fidelity computer simulations have been developed which provide valuable assistance to hardware development programs. The elements and techniques of optical system simulations are described, accompanied by samples of results. Existing high-fidelity simulations are described and computational resources discussed.