Analysis and design of three-stage concatenated color-shift keying

Visible Light Communication (VLC) relies on abundant unlicensed bandwidth resources. As an attractive high-data-rate modulation scheme designed for VLC, Color Shift Keying (CSK) assisted modulation is analysed. We commence our study from an uncoded M-CSK scheme relying on the joint Maximum Likelihood (ML) Hard-Detection (HD) of three colors, when communicating over an AWGN channel, where both empirical and analytical results are provided. We invoke EXtrinsic Information Transfer (EXIT) charts for designing a Maximum A-posteriori Probability (MAP) based Soft-Detection (SD) aided iterative receiver jointly detecting the three colors. Based on the EXIT characteristics of M-CSK, we design different signal labeling strategies for diverse color constellations and detection schemes, which are capable of achieving a substantially improved Bit Error Ratio (BER) performance. Thus, given a fixed transmission power, a CSK system using our proposed signal labeling is capable of increasing the reliable data transmission distance by about 30%

Cascaded PLC-VLC channel using OFDM and CSK techniques

Abstract: This paper puts in Cascade the power line communications (PLC) channel and the visible light communications (VLC) channel, in order to use the PLC channel as backbone for the VLC channel. This combination is suitable for applications in which hybrid PLC-VLC systems are needed. We investigate the behaviour of the cascaded channels for a full link transmission. Quadrature phase shift keying combined with orthogonal frequency division multiplexing (QPSK-OFDM) is used over the PLC channel and color shift keying (CSK) is deployed over the VLC channel to convey the information. Cascaded channel variances are analyzed. Complete simulated bit error rate (BER) is analyzed and presented for multiple scenarii that could occur in the two channels

Anwendung von maschinellem Lernen in der optischen Nachrichtenübertragungstechnik

Aufgrund des zunehmenden Datenverkehrs wird erwartet, dass die optischen Netze zukünftig mit höheren Systemkapazitäten betrieben werden. Dazu wird bspw. die kohärente Übertragung eingesetzt, bei der das Modulationsformat erhöht werden kann, erforder jedoch ein größeres SNR. Um dies zu erreichen, wird die optische Signalleistung erhöht, wodurch die Datenübertragung durch die nichtlinearen Beeinträchtigungen gestört wird. Der Schwerpunkt dieser Arbeit liegt auf der Entwicklung von Modellen des maschinellen Lernens, die auf diese nichtlineare Signalverschlechterung reagieren. Es wird die Support-Vector-Machine (SVM) implementiert und als klassifizierende Entscheidungsmaschine verwendet. Die Ergebnisse zeigen, dass die SVM eine verbesserte Kompensation sowohl der nichtlinearen Fasereffekte als auch der Verzerrungen der optischen Systemkomponenten ermöglicht. Das Prinzip von EONs bietet eine Technologie zur effizienten Nutzung der verfügbaren Ressourcen, die von der optischen Faser bereitgestellt werden. Ein Schlüsselelement der Technologie ist der bandbreitenvariable Transponder, der bspw. die Anpassung des Modulationsformats oder des Codierungsschemas an die aktuellen Verbindungsbedingungen ermöglicht. Um eine optimale Ressourcenauslastung zu gewährleisten wird der Einsatz von Algorithmen des Reinforcement Learnings untersucht. Die Ergebnisse zeigen, dass der RL-Algorithmus in der Lage ist, sich an unbekannte Link-Bedingungen anzupassen, während vergleichbare heuristische Ansätze wie der genetische Algorithmus für jedes Szenario neu trainiert werden müssen

Fiber-based phase-sensitive optical amplifiers and their applications

Optical parametric amplifiers rely on second-order susceptibility (three-wave mixing) or third-order susceptibility (four-wave mixing) in a nonlinear process where the energy of incoming photons is not changed (elastic scattering). In the latter case, two pump photons are converted to a signal and to an idler photon. Under certain conditions, related to the phase evolution of the waves involved, this conversion can be very effi-cient, resulting in large amplification of an input signal. As the nonlinear process can be very fast, all-optical applications aside from pure amplification are also possible. If the amplifier is implemented in an optical input-phase-sensitive manner, it is possible to amplify a signal wave without excess noise, i.e., with a noise figure of 0 dB. In this paper, we will provide the fundamental concepts and theory of such amplifiers, with a focus on their implementation in highly nonlinear optical fibers relying on four-wave mixing. We will discuss the distinctions between phase-insensitive and phase-sensitive operation and include several experimental results to illustrate their capability. Different applications of parametric amplifiers are also discussed, including their use in optical communication links

Silicon-organic hybrid electro-optical devices

Organic materials combined with strongly guiding silicon waveguides open the route to highly efficient electro-optical devices. Modulators based on the so-called silicon-organic hybrid (SOH) platform have only recently shown frequency responses up to 100 GHz, high-speed operation beyond 112 Gbit/s with fJ/bit power consumption. In this paper, we review the SOH platform and discuss important devices such as Mach-Zehnder and IQ-modulators based on the linear electro-optic effect. We further show liquid-crystal phase-shifters with a voltage-length product as low as V pi L = 0.06 V.mm and sub-mu W power consumption as required for slow optical switching or tuning optical filters and devices

Fiber-optic communications with microresonator frequency combs

Modern data communication links target ever-higher information throughput. To utilize the available bandwidth in a single strand of fiber, optical communication links often require a large number of lasers, each operating at a different wavelength. A microresonator frequency comb is a chip-scale multi-wavelength laser source whose spectrum consists of multiple evenly spaced lines. As the line spacing of a microresonator comb is on the order of several tens of GHz, it provides a promising light source candidate for implementing an integrated multi-wavelength transceiver. The interest for using microresonator combs in communications applications has therefore increased greatly in the last five years. The application-related developments have been complemented with an increased exploration and understanding of the operating principles behind these devices.This thesis studies microresonator frequency combs in both long-haul and high data-rate (multi-terabit per second) fiber communications systems. The results specifically include the longest demonstrated communications link with a microresonator light source as well as the highest order modulation format demonstration using any integrated comb source. The used microresonators are based on a high-Q silicon nitride platform provided by our collaborators at Purdue University. Part of the results are enabled by the high line powers resulting from a recently demonstrated novel comb state. This state bears similarities with dark solitons in fibers in that it corresponds to a train of dark pulses circulating inside the microresonator cavity. Overall, the results in this thesis provide a promising pathway towards enabling a future chip-scale multi-wavelength coherent transmitter

Coherent Optical OFDM Modem Employing Artificial Neural Networks for Dispersion and Nonlinearity Compensation in a Long-Haul Transmission System

In order to satisfy the ever increasing demand for the bandwidth requirement in broadband services the optical orthogonal frequency division multiplexing (OOFDM) scheme is being considered as a promising technique for future high-capacity optical networks. The aim of this thesis is to investigate, theoretically, the feasibility of implementing the coherent optical OFDM (CO-OOFDM) technique in long haul transmission networks. For CO-OOFDM and Fast-OFDM systems a set of modulation formats dependent analogue to digital converter (ADC) clipping ratio and the quantization bit have been identified, moreover, CO-OOFDM is more resilient to the chromatic dispersion (CD) when compared to the bandwidth efficient Fast-OFDM scheme. For CO-OOFDM systems numerical simulations are undertaken to investigate the effect of the number of sub-carriers, the cyclic prefix (CP), and ADC associated parameters such as the sampling speed, the clipping ratio, and the quantisation bit on the system performance over single mode fibre (SMF) links for data rates up to 80 Gb/s. The use of a large number of sub-carriers is more effective in combating the fibre CD compared to employing a long CP. Moreover, in the presence of fibre non-linearities identifying the optimum number of sub-carriers is a crucial factor in determining the modem performance. For a range of signal data rates up to 40 Gb/s, a set of data rate and transmission distance-dependent optimum ADC parameters are identified in this work. These parameters give rise to a negligible clipping and quantisation noise, moreover, ADC sampling speed can increase the dispersion tolerance while transmitting over SMF links. In addition, simulation results show that the use of adaptive modulation schemes improves the spectrum usage efficiency, thus resulting in higher tolerance to the CD when compared to the case where identical modulation formats are adopted across all sub-carriers. For a given transmission distance utilizing an artificial neural networks (ANN) equalizer improves the system bit error rate (BER) performance by a factor of 50% and 70%, respectively when considering SMF firstly CD and secondly nonlinear effects with CD. Moreover, for a fixed BER of 10-3 utilizing ANN increases the transmission distance by 1.87 times and 2 times, respectively while considering SMF CD and nonlinear effects. The proposed ANN equalizer performs more efficiently in combating SMF non-linearities than the previously published Kerr nonlinearity electrical compensation technique by a factor of 7

Code Design for Visible Light Communications Under Illumination Constraints

Visible light communication (VLC) uses the same LEDs which are an efficient source of illumination to transmit information concurrently using optical direct-detection. As a result of modulating the LED to convey information, there may be a perceived change in the light perception which besides being annoying, may produce physiological consequences under prolonged exposure. The aim of this research is to propose code design methodologies for controlling the effects of light intensity flickering, brightness control, and color shifts due to the modulation, encoding information bits in organized optical symbol sequences, and improving the coding gain by the use of the Viterbi algorithm. In order to mitigate the effect of intensity flickering presented in On-Off Keying modulation, five codes are designed with two proposed algorithms using finite-state machines (FSMs) for constraining the runs of zeros or ones. The codes are compared with the codes proposed in the IEEE 802.15.7 standard on VLC (Manchester code, 4B6B code, and the 8B10B code) in terms of flicker mitigation using the perceived flicker index (PFI) (a mathematical measure of flicker introduced in this study) and error-rate performance. The designed codes show asymptotic coding gains between 1:25 and 6 dB with a low sacrifice in PFI. To avoid color shifts in color-shift keying (CSK) modulation, four codes were designed from optimally CSK constellations and two classes of codes where one class is based on FSMs and the other on trellis-coded modulation (TCM) according to the desired color perception constraint. The designed codes show asymptotic coding gains between 1:5 to 3:5 dB with respect to uncoded transmission. For brightness control, variable-weight multipulse pulse-position modulation (VW-MPPM) is introduced as an alternative for increasing the spectral efficiency by the selection of multipulse pulse-position modulation symbols of diverse weight to attain the desired dimming level. Combining VM-MPPM symbols with Huffman codes and TCM, two designed codes are compared with MPPM codes for dimming level of 0:67 and 0:40 showing an asymptotic coding gain of 0:94 and 1:29 dB, respectively. Finally, we show the trade-offs between coding gain improvement and their effects on light perception