Marcus Duelk

Uni-directional time-domain bulk SOA Simulator considering carrier depletion by amplified spontaneous emission

A novel and comprehensive model for semiconductor optical amplifiers (SOAs) to be used in high bit rate (10-160 Gb/s) optical communication systems is presented. Its uni-directional and time-domain character makes it very appropriate to be efficiently integrated in a high-level systems simulator, as is explained through a comprehensive comparison and classification of prominent SOA models/simulators. Despite its fast execution time, the corresponding SOA simulator accurately considers a manifold of ultra-fast nonlinear effects and dynamics and, for the first time within a uni-directional simulator, the impact of amplified spontaneous emission (ASE) on the carrier dynamics. According to the numerical results here presented, the latter effect is fundamental in the simulation of SOAs longer than 0.5 mm.

Using LabVIEW™ for advanced nonlinear optoelectronic device simulations in high-speed optical communications

We present an advanced and comprehensive semiconductor optical amplifier model to analyze the propagation and amplification of 10 to, in principle, 1280 Gb/s ultra-short optical pulse sequences. Through appropriate transformation, the partial differential propagation-rate equation problem is numerically solved in a two-dimensional grid of fine resolution. The corresponding simulator, entirely programmed in the graphical language LabVIEW, is compared to an identical simulator implemented in the popular high-level text-based language Matlab. Special care has been taken to implement the same set of algorithms using equivalent codes for each language, such that a fair and objective one-to-one comparison can be carried out. In terms of computational time the LabVIEW simulator shows a tenfold outperformance, compared to its text-based identical counterpart implemented in Matlab, when typical bit sequences at 40 Gb/s with a length of 8 to 1024 bits are tested. The performance results presented here apply to a broader set of device modeling scenarios.

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We present extensive numerical simulations of an optical link deploying four electroabsorption modulated lasers (EMLs) at 25 Gb/s over up to 40 km of standard single-mode fiber. The receiver comprises a semiconductor optical amplifier (SOA) as a preamplifier. We analyze the bit error ratio (BER) along different link lengths under varying conditions such as output power and extinction ratio of the EML transmitters, the noise figure of the SOA preamplifier and the bit and word alignment of the four wavelength channels. We demonstrate that the EML transmitters require a minimum extinction ratio of 8 to 10 dB and a minimum output power of +2 to +4 dBm in order to meet the BER requirements for 100 Gigabit Ethernet (100 GbE) using 4 times 25-Gb/s physical media dependent (PMD) devices. Furthermore, we show that single-channel performance analyses can be used to estimate the behavior for multichannel amplification in the SOA preamplifier.

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The availability of analytical models and numerical simulation tools is inevitable for the development and optimization of broadband high-power superluminescent light-emitting diodes (SLEDs) and its applications. In this paper, various theoretical aspects of SLEDs are discussed, which are important for the successful design of new devices with superior performance. We study the suppression of residual facet reflections as well as the importance of a careful vertical waveguide design. Furthermore, a simple analytical model for the L-I characteristics of SLEDs is developed that is based on a power law with an exponent that is dependent on the chip length. The theoretical model is verified by a comparison with experimental results of a broadband SLED operating in the wavelength region around 1300 nm. It is shown that the model can be also used to extract important simulation parameters from measured L-I characteristics. Finally, results are presented for an improved high-performance SLED structure in the same wavelength region with output powers of more than 50 mW and a 10-dB spectral bandwidth beyond 100 nm.

25-Gb/s 40-km PHY at 1310 nm for 100 GbE Using SOA-Based Preamplifier

We demonstrate a rapidly tunable 10 Gb/s all-optical wavelength converter based on a semiconductor optical amplifier delay interferometer and a tunable laser. It uses a 16-channel 100 GHz-spacing digitally tunable multifrequency laser based on a novel external-cavity laser design. The bit sequence on the incoming wavelength is converted alternatively to different wavelengths. Power penalties are 1.1 dB for 30 ns guard-time spacing between wavelength packets.

Modeling and Simulation of Superluminescent Light-Emitting Diodes (SLEDs)

Numerical simulations are inevitable for the development and optimization of GaN-based superluminescent light-emitting diodes (SLEDs) for the blue and green spectral region. Depending on their application the devices have to be optimized with respect to given specifications. We discuss the simulation of various device performance parameters as well as the basic calibration of the full 3D device simulator. We use well-characterized SLED devices realized with standard epitaxial structures for the calibration procedure. A comparison between simulated and measured data allows the extraction of important simulation parameters such as the screening factor.

Rapidly tunable all-optical wavelength converter based on single semiconductor optical amplifier delay interferometer

A novel simulator useful to design and analyze the functionality of advanced integrated optical chips is presented and demonstrated through an example of a wavelength converter operating at 40 Gb/s. Written in a modular graphical programming language, the simulator is intuitive, fast, flexible and powerful. It represents an attractive alternative to more traditional approaches

Numerical simulations of blue and green GaN SLEDs

A numerical investigation of the performance of an automatic gain-controlled semiconductor optical preamplified receiver for a 4 x 25 Gbits/s wavelength division multiplexing transmission system with a 0-40 km reach is presented. We show that the control scheme acting on the semiconductor optical amplifier (SOA) gain increases the input power dynamic range of the optical receiver, thus allowing the transmission system to operate error free regardless of fiber length. In contrast, a fixed-gain optical receiver shows poor performance that is due to SOA nonlinearity and photodiode overload, which are well captured by the corresponding simulation models. The device represents a practical alternative to the next-generation high-speed Ethernet technology.

A Simulator for Integrated Optoelectronic Devices

Superluminescent light emitting diodes (SLEDs) have beam-like optical output similar to laser diodes (LDs) while offering a broader emission wavelength spectrum. They represent, therefore, an interesting alternative to conventional LDs for applications where a short coherence length or low speckle noise are required. Visible SLEDs emitting in the red, blue, and green are ideal candidates for the manufacturing of speckle-free light sources in portable or wearable compact projection systems. In this paper, we review the current status of EXALOS’ GaN-based SLED technology in the violet-blue spectral range and report on our recent progress in terms of performance for devices with 440-460 nm emission. Furthermore, we discuss the challenges in achieving light output at even longer wavelengths. As a matter of fact, lower refractive index contrast between the waveguiding and cladding layers, decreased p-type doping efficiency when growing at low temperatures, low crystal quality and thermal stability of the active region have to be addressed and solved in order to achieve green emission. The epitaxial structures were grown by metalorganic vapor phase epitaxy (MOVPE) on c-plane freestanding GaN substrates. Growth was followed by standard fabrication of SLEDs with a ridge waveguide design. A record CW output power of 150 mW (at an operating current of 330 mA) and a wall-plug efficiency (WPE) of 8% have been obtained at an emission wavelength >440 nm.

Gain-controlled semiconductor optical preamplifier for the 100 Gbit/s 40 km Ethernet receiver

Superluminescent light-emitting diodes (SLEDs) are very attractive as compact, highly efficient light sources for various applications in the visible red spectral region. We simulate and discuss the electro-optical performance of SLEDs operating at center wavelengths of 625–650 nm. We show that for current SLED structures the optimum wavelength with respect to maximum luminous flux and power conversion efficiency is around 635 nm. Design improvements of the epitaxial layer structure offer the way to shorter wavelengths with higher luminous flux and efficiency values.