Advanced optical modulation and fast reconfigurable en/decoding techniques for OCDMA application

With the explosive growth of bandwidth requirement in optical fiber communication networks, optical code division multiple access (OCDMA) has witnessed tremendous achievements as one of the promising technologies for optical access networks over the past decades. In an OCDMA system, optical code processing is one of the key techniques. Rapid optical code reconfiguration can improve flexibility and security of the OCDMA system. This thesis focuses on advanced optical modulations and en/decoding techniques for applications in fast reconfigurable OCDMA systems and secure optical communications. A novel time domain spectral phase encoding (SPE) scheme which can rapidly reconfigure the optical code and is compatible with conventional spectral domain phase en/decoding by using a pair of dispersive devices and a high speed phase modulator is proposed. Based on this scheme, a novel advanced modulation technique that can simultaneously generate both the optical code and the differential-phase-shift-keying (DPSK) data using a single phase modulator is experimentally demonstrated. A symmetric time domain spectral phase encoding and decoding (SPE/SPD) scheme using a similar setup for both the transmitter and receiver is further proposed, based on which a bit-by-bit optical code scrambling and DPSK data modulation technique for secure optical communications has been successfully demonstrated. By combining optical encoding and optical steganography, a novel approach for secure transmission of time domain spectral phase encoded on-off-keying (OOK)/DPSK-OCDMA signal over public wavelength-division multiplexing (WDM) network has also been proposed and demonstrated. To enable high speed operation of the time domain SPE/SPD scheme and enhance the system security, a rapid programmable, code-length variable bit-by-bit optical code shifting technique is proposed. Based on this technique, security improvements for OOK/DPSK OCDMA systems at data rates of 10Gb/s and 40Gb/s using reconfigurable optical codes of up to 1024-chip have been achieved. Finally, a novel tunable two-dimensional coherent optical en/decoder which can simultaneously perform wavelength hopping and spectral phase encoding based on coupled micro-ring resonator is proposed and theoretically investigated. The techniques included in this thesis could be potentially used for future fast reconfigurable and secure optical code based communication systems

Fiber Bragg Grating Based Sensors and Systems

This book is a collection of papers that originated as a Special Issue, focused on some recent advances related to fiber Bragg grating-based sensors and systems. Conventionally, this book can be divided into three parts: intelligent systems, new types of sensors, and original interrogators. The intelligent systems presented include evaluation of strain transition properties between cast-in FBGs and cast aluminum during uniaxial straining, multi-point strain measurements on a containment vessel, damage detection methods based on long-gauge FBG for highway bridges, evaluation of a coupled sequential approach for rotorcraft landing simulation, wearable hand modules and real-time tracking algorithms for measuring finger joint angles of different hand sizes, and glaze icing detection of 110 kV composite insulators. New types of sensors are reflected in multi-addressed fiber Bragg structures for microwave–photonic sensor systems, its applications in load-sensing wheel hub bearings, and more complex influence in problems of generation of vortex optical beams based on chiral fiber-optic periodic structures. Original interrogators include research in optical designs with curved detectors for FBG interrogation monitors; demonstration of a filterless, multi-point, and temperature-independent FBG dynamical demodulator using pulse-width modulation; and dual wavelength differential detection of FBG sensors with a pulsed DFB laser

Green radio communication networks applying radio-over-fibre technology for wireless access

Wireless communication increasingly is becoming the first choice link to enter into the global information society. It is an essential part of broadband communication networks, due to its capacity to cover the end-user domain, outdoors or indoors. The use of mobile phones and broadband has already exceeded the one of the fixed telephones and has caused tremendous changes in peoples life, as not only to be recognised in the current political overthrows. The all-around presence of wireless communication links combined with functions that support mobility will make a roaming person-bound communication network possible in the near future. This idea of a personal network, in which a user has his own communication environment available everywhere, necessitates immense numbers of radio access points to maintain the wireless links and support mobility. The progress towards “all-around wireless” needs budget and easily maintainable radio access points, with simplified signal processing and consolidation of the radio network functions in a central station. The RF energy consumption in mobile base stations is one of the main problems in the wireless communication system, which has led to the worldwide research in so called green communication, which offers an environmentally friendly and cost-effective solution. In order to extend networks and mobility support, the simplification of antenna stations and broadband communication capacity becomes an increasingly urgent demand, also the extension of the wireless signal transmission distance to consolidate the signal processing in a centralised site. Radio-over-Fibre technology (RoF) was considered and found to be the most promising solution to achieve effective delivery of wireless and baseband signals, also to reduce RF energy consumption. The overall aim of this research project was to simulate the transmission of wireless and baseband RF signals via fibre for a long distance in high quality, consuming a low-power budget. Therefore, this thesis demonstrated a green radio communication network and the advantage of transmitting signals via fibre rather than via air. The contributions of this research work were described in the follows: Firstly, a comparison of the power consumption in WiMAX via air and fibre is presented. As shown in the simulation results, the power budget for the transmission of 64 QAM WiMAX IEEE 802.16-2005 via air for a distance of 5km lies at -189.67 dB, whereas for the transmission via RoF for a distance of 140km, the power consumption ranges at 65dB. Through the deployment of a triple symmetrical compensator technique, consisting of SMF, DCF and FBG, the transmission distance of the 54 Mbps WiMAX signal can be increased to 410km without increasing the power budget of 65dB. An amendment of the triple compensator technique to SMF, DCF and CFBG allows a 120Mbps WiMAX signal transmission with a clear RF spectrum of 3.5 GHz and constellation diagram over a fibre length of 792km using a power budget of 192dB. Secondly, the thesis demonstrates a simulation setup for the deployment of more than one wireless system, namely 64 QAM WiMAX IEEE 802.16-2005 and LTE, for a data bit rate of 1Gbps via Wavelength Division Multiplexing (WDM) RoF over a transmission distance of 1800km. The RoF system includes two triple symmetrical compensator techniques - DCF, SMF, and CFBG - to obtain a large bandwidth, power budget of 393.6dB and a high signal quality for the long transmission distance. Finally, the thesis proposed a high data bit rate and energy efficient simulation architecture, applying a passive optical component for a transmission span up to 600km. A Gigabit Optical Passive Network (GPON) based on RoF downlink 2.5 Gbps and uplink 1.25Gbps is employed to carry LTE and WiMAX, also 18 digital channels by utilising Coarse Wavelength Division Multiplexing (CWDM). The setup achieved high data speed, a low-power budget of 151.2dB, and an increased service length of up to 600km

High Data Rate Coherent Optical OFDM System for Long-Haul Transmission

The growth in internet traffic has driven the increase in demand for bandwidth and high data rates. Optical Orthogonal Frequency Division Multiplexing is considered as a promising technology to satisfy the increased demand for bandwidth in broadband services. Optical OFDM received a great attention after proposing it as a modulation technique for the long-haul transmission in both direct and coherent detection. However, Coherent Optical OFDM (CO-OFDM) is the next generation technology for the optical communications, since it integrates the advantages of both coherent systems and OFDM systems. It has the ability to overcome many optical fiber restrictions such as chromatic dispersion (CD) and polarization mode dispersion (PMD). Moreover, Integrating the Coherent Optical OFDM with Wavelength Division Multiplexing (WDM) systems will provide the transmission system with a high bandwidth, a significant data rates, and a high spectral efficiency without increasing the cost or the complexity of the system. WDM systems help to enhance the capacity and the data rate of the system by sending multiple wavelengths over a single fiber. This research focuses on the implementation and performance analysis of high data rate coherent optical OFDM for long-haul transmission. The study starts with a single user and extends to the implanting of the WDM system. OptiSystem-12 simulation tool is fully used to design and implement the system. The system utilizes to carry range of data rates start from 10 Gbps to 1 Tbps, 4-QAM (2 bits-per-symbol) is used a modulation type for the OFDM signal, Optical I/Q modulation is employed at the transmitter and coherent detection is employed at the receiver. The performance of the system is studied and analyzed system in terms of Bit-Error-Rate (BER), the effect of the transmission distance on the Optical-Signal-to-Noise-Ratio (OSNR), and the relation of BER and OSNR with regard to the transmission distance

Detection and processing of phase modulated optical signals at 40 Gbit/s and beyond

This thesis addresses demodulation in direct detection systems and signal processing of high speed phase modulated signals in future all-optical wavelength division multiplexing (WDM) communication systems where differential phase shift keying (DPSK) or differential quadrature phase shift keying (DQPSK) are used to transport information. All-optical network functionalities -such as optical labeling, wavelength conversion and signal regeneration- are experimentally investigated. Direct detection of phase modulated signals requires phase-to-intensity modulation conversion in a demodulator at the receiver side. This is typically implemented in a one bit delay Mach-Zehnder interferometer (MZI). Two alternative ways of performing phase-to-intensity modulation conversion are presented. Successful demodulation of DPSK signals up to 40 Gbit/s is demonstrated using the proposed two devices. Optical labeling has been proposed as an efficient way to implement packet routing and forwarding functionalities in future IP-over-WDM networks. An in-band subcarrier multiplexing (SCM) labeled signal using 40 Gbit/s DSPK payload and 25 Mbit/s non return-to-zero(NRZ) SCM label, is successfully transmitted over 80 km post-compensated non-zero dispersion shifted fiber (NZDSF) span. Using orthogonal labeling, an amplitude shift keying (ASK)/DPSK labeled signal using 40 Gbit/s return-to-zero (RZ) payload and 2.5 Gbit/s DPSK label, is generated. WDM transmission and label swapping are demonstrated for such a signal. In future all-optical WDM networks, wavelength conversion is an essential functionality to provide wavelength flexibility and avoid wavelength blocking. Using a 50 m long highly nonlinear photonic crystal fiber (HNL-PCF), with a simple four-wave mixing (FWM) scheme, wavelength conversion of single channel and multi-channel high-speed DPSK signals is presented. Wavelength conversion of an 80 Gbit/s RZ-DPSK-ASK signal generated by combining different modulation formats is also reported. Amplitude distortion accumulated over transmission spans will eventually be converted into nonlinear phase noise, and consequently degrade the performance of systems making use of RZ-DPSK format. All-optical signal regeneration avoiding O-E-O conversion is desired to improve signal quality in ultra long-haul transmission systems. Proof-of-principle numerical simulation results are provided, that suggest the amplitude regeneration capability based on FWM in a highly nonlinear fiber (HNLF). The first reported experimental demonstration of amplitude equalization of 40 Gbit/s RZ-DPSK signals using a 500 m long HNLF is presented. Using four possible phase levels to carry the information, DQPSK allows generation of high-speed optical signals at bit rate that is twice the operating speed of the electronics involved. Generation of an 80 Gbit/s DQPSK signal is demonstrated using 40 Gbit/s equipment. The first demonstration of wavelength conversion of such a high-speed signal is implemented using FWM in a 1 km long HNLF. No indication of error floor is observed. Using polarization multiplexing and combination of DQPSK with ASK and RZ pulse carving at a symbol rate of 40 Gbaud, a 240 Gbit/s RZ-DQPSK-ASK signal is generated and transmitted over 50 km fiber span with no power penalty. In summary, we show that direct detection and all-optical signal processing -including optical labeling, wavelength conversion and signal regeneration- that already have been studied intensively for signals using conventional on-off keying (OOK) format, can also be successfully implemented for high-speed phase modulated signals. The results obtained in this work are believed to enhance the feasibility of phase modulation in future ultra-high speed spectrally efficient optical communication systems

Optical code-division multiple access system and optical signal processing

This thesis presents our recent researches on the development of coding devices, the investigation of security and the design of systems in the optical cod-division multiple access (OCDMA) systems. Besides, the techniques of nonlinear signal processing used in the OCDMA systems fire our imagination, thus some researches on all-optical signal processing are carried out and also summarized in this thesis. Two fiber Bragg grating (FBG) based coding devices are proposed. The first coding device is a superstructured FBG (SSFBG) using ±π/2-phase shifts instead of conventional 0/π-phase shifts. The ±π/2-phase-shifted SSFBG en/decoders can not only conceal optical codes well in the encoded signals but also realize the reutilization of available codes by hybrid use with conventional 0/π-phase-shifted SSFBG en/decoders. The second FBG based coding device is synthesized by layer-peeling method, which can be used for simultaneous optical code recognition and chromatic dispersion compensation. Then, two eavesdropping schemes, one-bit delay interference detection and differential detection, are demonstrated to reveal the security vulnerability of differential phase-shift keying (DPSK) and code-shift keying (CSK) OCDMA systems. To address the security issue as well as increase the transmission capacity, an orthogonal modulation format based on DPSK and CSK is introduced into the OCDMA systems. A 2 bit/symbol 10 Gsymbol/s transmission system using the orthogonal modulation format is achieved. The security of the system can be partially guaranteed. Furthermore, a fully-asynchronous gigabit-symmetric OCDMA passive optical network (PON) is proposed, in which a self-clocked time gate is employed for signal regeneration. A remodulation scheme is used in the PON, which let downstream and upstream share the same optical carrier, allowing optical network units source-free. An error-free 4-user 10 Gbit/s/user duplex transmission over 50 km distance is reazlied. A versatile waveform generation scheme is then studied. A theoretical model is established and a waveform prediction algorithm is summarized. In the demonstration, various waveforms are generated including short pulse, trapezoidal, triangular and sawtooth waveforms and doublet pulse. ii In addition, an all-optical simultaneous half-addition and half-subtraction scheme is achieved at an operating rate of 10 GHz by using only two semiconductor optical amplifiers (SOA) without any assist light. Lastly, two modulation format conversion schemes are demonstrated. The first conversion is from NRZ-OOK to PSK-Manchester coding format using a SOA based Mach-Zehnder interferometer. The second conversion is from RZ-DQPSK to RZ-OOK by employing a supercontinuum based optical thresholder

Design of optical fiber sensors and interrogation schemes

[ES] Las fibras ópticas son dispositivos muy utilizados en el campo de las telecomunicaciones desde su descubrimiento. En las últimas décadas, las fibras ópticas comenzaron a utilizarse como sensores fotónicos. Los primeros trabajos se centraron en la medición de unas dimensiones físicas en un punto específico. Posteriormente, surgió la posibilidad de medir las propiedades de la fibra óptica en diferentes puntos a lo largo de la fibra. Este tipo de sensores se definen como sensores distribuidos. Los componentes optoelectrónicos fueron desarrollados e investigados para telecomunicaciones. Los avances en las telecomunicaciones hicieron posible el desarrollo de sistemas de interrogación para sensores de fibra óptica, creciendo en paralelo con los avances de las telecomunicaciones. Se desarrollaron sistemas de interrogación de fibra óptica que permiten el uso de una única fibra óptica monomodo estándar como sensor que puede monitorear decenas de miles de puntos de detección al mismo tiempo. Los métodos que extraen la información de detección de la señal reflejada en la fibra óptica son los más empleados debido a la facilidad de acceso al sensor y la flexibilidad de estos sistemas. Los más estudiados son la reflectometría en dominios de tiempo y frecuencia. La reflectometría óptica en el dominio del tiempo (OTDR) fue la primera técnica utilizada para detectar la posición de los fallos en las redes de comunica-ción de fibra óptica. El OTDR sensible a la fase hizo posible detectar la elongación y la temperatura en una posición específica. Paralelamente, los gratings de Bragg (FBG) se convirtieron en los dispositivos más utilizados para implementar sensores en fibra óptica discretos. Se desarrollaron técnicas de multiplexación para realizar la detección en múltiples puntos utilizando FGBs. La reflectometría realizada interrogando arrays de FBG débiles demuestra que mejora el rendimiento del sistema en comparación al uso de una fibra monomodo. Los sistemas de interrogatorio actuales tienen algunos inconvenientes. Algunos de ellos son velocidad de interrogatorio limitada, grandes dimensiones y alto costo. En esta tesis doctoral se desarrollaron nuevos sistemas de interrogación y sensores de fibra óptica para superar algunos de estos inconvenientes. Los sensores de fibra óptica de plástico demuestran ser una plataforma innovadora para desarrollar nuevos sensores y sistemas de interrogación de bajo costo y fáciles de implementar para fibras de plástico comerciales. Se investigó la reflectometría en el dominio del tiempo y las técnicas fotónicas de microondas para la interrogación de una matriz de rejillas débiles que permitieron simplificar el sistema de interrogación para la detección de temperatura y vibración.[CA] Les fibres òptiques són dispositius molt utilitzats en el camp de les telecomunica-cions des del seu descobriment. En les últimes dècades, les fibres òptiques van començar a utilitzar-se com a sensors fotònics. Els primers treballs es van centrar en el mesurament d'unes dimensions físiques en un punt específic. Posteriorment, va sorgir la possibilitat de mesurar les propietats de la fibra òptica en diferents punts al llarg de la fibra. Aquest tipus de sensors es defineixen com a sensors distribüits. Els components optoelectrònics van ser desenvolupats i investigats per a telecomunicacions. Els avanços en les telecomunicacions van fer possi-ble el desenvolupament de sistemes d'interrogació per a sensors de fibra òptica, creixent en paral·lel amb els avanços de les telecomunicacions. Es van desenvolupar sistemes d'interrogació de fibra òptica que permeten l'ús d'una única fibra òptica monomodo estàndard com a sensor que pot monitorar desenes de milers de punts de detecció al mateix temps. Els mètodes que extreuen la informació de detecció del senyal reflectit en la fibra òptica són els més utilitzats a causa de la facilitat d'accés al sensor i la flexibilitat d'aquests sistemes. Els més estudiats són la reflectometría en dominis de temps i freqüència. La reflectometría òptica en el domini del temps (OTDR) va ser la primera tècnica utilitzada per a detectar la posició de les fallades en les xarxes de comunicació de fibra òptica. El OTDR sensible a la fase va fer possible detectar l'elongació i la temperatura en una posició específica. Paral·lelament, els gratings de Bragg (FBG) es van convertir en els dispositius més utilitzats per a implementar sensors en fibra òptica discrets. Es van desenvolupar tècniques de multiplexació per a realitzar la detecció en múltiples punts utilitzant FGBs. La reflectometría realitzada interrogant arrays de FBG febles demostra que millora el rendiment del sistema en comparació a l'ús d'una fibra monomodo. Els sistemes d'interrogatori actuals tenen alguns inconvenients. Alguns d'ells són velocitat d'interrogatori limitada, voluminositat i alt cost. En aquesta tesi doctoral es van desenvolupar nous sistemes d'interrogació i sensors de fibra òptica per a superar alguns d'aquests inconvenients. Els sensors de fibra òptica de plàstic demostren ser una plataforma innovadora per a desenvolupar nous sensors i siste-mes d'interrogació de baix cost i fàcils d'implementar per a fibres de plàstic comercials. Es va investigar la reflectometría en el domini del temps i les tècniques fotòniques de microones per a la interrogació d'una matriu de reixetes febles que van permetre simplificar el sistema d'interrogació per a la detecció de temperatura i vibració.[EN] Optical fibers are devices largely used in telecommunication field since their discovery. In the last decades, optical fibers started to be used as photonic sensors. The first works were focused on the measurement of physical dimensions to a specific point. Afterward, emerged the possibility to measure the optical fiber properties at different locations along the fiber. These kinds of sensors are defined as distributed sensors. The optoelectronic components were developed and investigated for telecommunications. The progress in telecommunication made possible the development of optical fiber sensors interrogation systems, growing in parallel with the advances of telecommunications. Optical fiber interrogation systems were developed to use a single standard monomode optical fiber as a sensor that can monitor tens of thousands of sensing points at the same time. The methods that extract the sensing information from the backscattered signal in the optical fiber are widely employed because of the easiness of access to the sensor element and the flexibility of these systems. The most studied are the reflectometry in time and frequency domains. The optical time domain reflectometry (OTDR) was the first technique used to detect the position of the failures in the optical fiber communication networks. Using phase sensitive OTDR it is possible to sense strain and temperature at a specific position. In parallel, fiber Bragg gratings (FBGs) became the most widely used devices to implement discrete optical fiber sensors. Multiplexing techniques were developed to perform multi points sensing using these gratings. The reflectometry performed interrogating weak FBGs arrays demonstrate to improve the performance of the system employing a single mode fiber. The interrogation systems nowadays have some drawbacks. Some of them are limited speed of interrogation, bulkiness, and high cost. New interrogation systems and optical fiber sensors were developed in this doctoral thesis to overcome some of these drawbacks. Plastic optical fiber sensors demonstrate to be an innovative platform to develop both new sensors and low cost, easy to implement interrogation systems for commercial plastic fibers. Reflectometry in time domain and microwave photonic techniques were investigated for the interrogation of weak gratings array allowed to simplify the interrogation system for the sensing of temperature and vibration.I would like to greatly thank the European Union’s Horizon 2020 Research and Innovation Program that funded the research described in this thesis under the Marie Sklodowska-Curie Action Grant Agreement 722509.Sartiano, D. (2021). Design of optical fiber sensors and interrogation schemes [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/161357TESI

Photonic Modulation and Demodulation techniques for Multi-Gb/s Millimetre wave Wireless Links

Los sistemas de radio sobre fibra(Radio Over fibre ROF) ofrecen el ancho de banda y flexibilidad necesario para la generación y distribución de del señales inalámbricas del futuro en una arquitectura de red óptica, que reduce el coste de las redes centralizando el procesado y simplificando la ubicación de la antena (estación de base EB). El uso de sistemas de comunicaciones ópticas como una media de transporte de señales inalámbricas en enlaces RoF reduce el cuello de botella entre los estándares de acceso inalámbrico y cableado en un dominio convergente óptico. Las redes de acceso ópticas están evolucionando con capacidades de hasta 10 Gb/s con el estándard 10GEPON, dejando un cuello de botella entre tecnologías de acceso inalámbrico y óptico. . Eso ha motivado gran esfuerzo de investigación en la generación y distribución de señales inalámbricas de alta capacidad (> 10 Gb/s) basada en RoF. En esta tesis se ha investigado el uso de técnicas fotónicas para la generación , distribución y demodulación de señales inalámbricas moduladas vectorialmente. Esta tesis está principalmente dedicada a la generación de señales inalámbricas espectralmente eficientes como la modulación de fase en cuadratura (QPSK) o modulación de amplitud cuadratura de multinivel (M-QAM). El trabajo presentado en esta tesis está clasificado en dos partes: la primera de ellas trata de las técnicas fotónicas que utilizan señales eléctricas coherente para la generación y demodulación de señales inalámbricas, mientras la segunda parte trata de usar señales ópticas incoherentes. En la primera parte de la tesis, están presentadas diferentes arquitecturas de sistemas y están analizadas numéricamente, y demostradas experimentalmente. Un nuevo concepto denominado "modulación vectorial fotónica" (PVM) es propuesto para la generación de señales inalámbricas con una modulación M-QAM. Basado en esta técnica se presenta la generación de señales de capacidad 10Gb/s con una modulación de QPSK y 16-QAM.Sambaraju -, R. (2010). Photonic Modulation and Demodulation techniques for Multi-Gb/s Millimetre wave Wireless Links [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8857Palanci