System Performance and Limits of Optical Modulation Formats in Dense Wavelength Division Multiplexing Systems

In this paper we investigate in OptSim software environment the system performance of intensity and phase modulation formats for different network scenarios and dense wavelength division multiplexing grids. OptSim employs the Time Domain Split Step method to implement the signal distribution equation in a fiber. We investigate intensity formats, such as Non Return to Zero, Return to Zero, Carrier- Suppressed Return to Zero and DuoBinary, and phase modulation formats like Differential Phase-Shift Keying and Differential Quadrature Phase-Shift Keying. The main goal is to compare these formats in terms of bit error rate, Q-factor, optical reach and grid limitations for transmission rates 10, 40 and 100 Gbps per channel and discuss the possibilities of increasing their spectral efficiency. We also focus on other advanced solutions such as the polarization division multiplexing combined with phase modulations, coherent detection and advanced digital signal processing which mainly benefits in spectral efficiency, optical signal to noise ratio and chromatic dispersion tolerances

Forward Error Correction in Memoryless Optical Modulation

The unprecedented growth in demand for digital media has led to an all-time high in society’s demand for information. This demand will in all likelihood continue to grow as technology such as 3D television service, on-demand video and peer-to-peer networking continue to become more common place. The large amount of information required is currently transmitted optically using a wavelength division multiplexing (WDM) network structure. The need to increase the capacity of the existing WDM network infrastructure efficiently is essential to continue to provide new high bandwidth services to end-users, while at the same time minimizing network providers’ costs. In WDM systems the key to reducing the cost per transported information bit is to effectively share all optical components. These components must operate within the same wavelength limited window; therefore it is necessary to place the WDM channels as close together as possible. At the same time, the correct modulation format must be selected in order to create flexible, cost-effective, high-capacity optical networks. This thesis presents a detailed comparison of Differential Quadrature Phase Shift Keying (DQPSK) to other modulation formats. This comparison is implemented through a series of simulations in which the bit error rate of various modulation formats are compared both with and without the presence of forward error correction techniques. Based off of these simulation results, the top performing modulation formats are placed into a multiplexed simulation to assess their overall robustness in the face of multiple filtering impairments

Investigation of high bit rate optical transmission systems employing a channel data rate of 40 Gb/s

Das Ziel dieser Doktorarbeit war eine detaillierte Untersuchung von hoch bit ratigen optischen Übertragungssystemen mit einer Kanaldatenrate von 40 Gbit/s, die als wavelength division multiplexing (WDM) Systeme realisiert sind. Die Erkenntnisse, die durch umfangreiche numerische Untersuchungen gewonnen worden sind, wurden für die Erarbeitung von Designkriterien für die Übertragungssysteme der nächsten Generation verwendet. Der Schwerpunkt der Arbeit liegt dabei an 40 Gbit/s basierten WDM Systemen mit amplitudenmodulierten optischen Signalen. Nach einer umfangreichen Beschreibung der Funktionsweise und des Standes der Technik von Systemkomponenten, die in optischen Übertragungssystemen zum Einsatz kommen, wurden die Übertragungseffekte (z.B. chromatische Dispersion, Kerr-Effekt) erklärt und beschrieben, die eine störungsfreie Übertragung von optischen Pulsen in Übertragungsstrecken beeinträchtigen. Wegen der Fokussierung der Arbeit auf amplitudenmodulierte Systeme, wurden Erzeugungsmethoden und Spektraleneigenschaften von zahlreichen amplitude-shift-keying (ASK) basierten Modulationsformaten erklärt. Die untersuchten Modulationsformate wurden in drei Gruppen unterteilt: Non-return-to-zero (NRZ) basierende Formate, Return-to-zero (RZ) basierende Formate und neue Modulationsformate. Zu der Gruppe von NRZ basierten Modulationsformaten gehören konventionelles NRZ und Duobinary Modulation. In der Gruppe von RZ basierten Formaten wurden konventionelles RZ, Carrier-suppressed RZ (CSRZ) und Single-side-band RZ (SSB-RZ) eingeführt. Die Gruppe der neuen Formate beinhaltet Modulationsformate, die vom Autor im Rahmen der Arbeit vorgeschlagen und weiterentwickelt worden sind: Alternate-chirped NRZ (alCNRZ), Novel-chirped RZ (nCRZ), Alternate-polarized NRZ (alPNRZ) und Alternate-polarized RZ (alPRZ). Die Anforderungen, die bei der Entwicklung von neuen Modulationsformaten berücksichtigt worden sind, waren die Verbesserung der nichtlinearen Übertragungseigenschaften (z.B. nichtlineare Toleranz) der Übertragungsstrecke und eine effizientere Ausnutzung der zur Verfügung stehenden Systembandbreite (z.B. Erhöhung der spektralen Effizienz), wobei die vorgeschlagenen Modulationsformate kompatibel mit herkömmlichen Systemkonfigurationen (z.B. Empfänger) sein sollten. Aufgrund numerischer Natur der Arbeit wurden diverse Auswertekriterien eingeführt, die eine genaue Evaluierung der Übertragungsqualität ermöglichen und im Rahmen der Arbeit verwendet worden sind. Die Vor- und Nachteile der Auswertekriterien wie Bitfehlerrate (BER), Q-Faktor, optischer Signalrauschabstand (OSNR) und Augendiagramme wurden erläutert, und ein Vergleich zwischen allen Kriterien ist gemacht worden. Die 40 Gbit/s basierten numerischen Untersuchungen wurden für Einkanal- und Mehrkanalübertragungssysteme durchgeführt. Dabei wurde im Mehrkanalfall zwischen WDM-Systemen mit einer spektralen Effizienz von 0.4 bit/s/Hz und effizienteren dense WDM (DWDM) Systemen mit einer spektralen Effizienz von 0.8 bit/s/Hz unterschieden. Das Ziel dieser Untersuchungen war eine 40 Gbit/s Systemoptimierung durch Bestimmung von optimalen Übertragungsfasern, optimalen Dispersionskompensationsschemen und optimalen Leistungsbereichen, in denen die zukünftigen Systeme betrieben werden sollen. Dabei wurden alle Untersuchungen unter Berücksichtigung von unterschiedlichen Modulationsformaten durchgeführt, um einen Vergleich zwischen den Modulationsformaten gewährleisten zu können. Die Ergebnisse der Einkanaluntersuchungen haben gezeigt, dass NRZ basierten Modulationsformate durch eine hohe Dispersionstoleranz (ca. ±50 ps/nm) und eine niedrige nichtlineare Toleranz charakterisiert sind, was eine Beschränkung der maximaler Übertragungslänge verursacht. Die wichtigsten Störeffekte stellen in diesem Fall Selbstphasenmodulation (SPM) und die Interaktion zwischen SPM und chromatischer Dispersion dar. Die RZ basierten Verfahren zeichnen sich durch eine reduzierte Dispersionstoleranz (ca. ±25 ps/nm) aus, aber ermöglichen wegen erhöhter nichtlinearer Toleranz eine Verbesserung der maximalen Übertragungslänge verglichen zu NRZ Formaten. Die limitierenden Effekte in einer RZ basierten Übertragung sind Intrakanaleffekte (z.B. Intrakanalkreuzphasenmodulation IXPM), die bei höheren Signalleistungen von SPM begleitet sind. Die wichtigste Eigenschaft der neuen Modulationsverfahren ist die große nichtlineare Toleranz, die besonders bei alternierend polarisierten Modulationsverfahren (z.B. alPNRZ, alPRZ) zur Geltung kommt. Es wurde gezeigt, dass in allen untersuchten Fällen die Übertragungsqualität von eine mittleren Faserdispersion (ca. 4-8 ps/nm·km) profitiert und dass Dispersionskompensationsschemen mit einem bestimmten Prozent (variiert von Format zu Format) der Vorkompensation das Optimum darstellen. Die Mehrkanaluntersuchungen haben gezeigt, dass solange die spektrale Effizienz eines 40 Gbit/s basierten WDM systems klein (£ 0.4 bit/s/Hz) ist, die Einkanaleffekte (z.B. SPM, IXPM) die dominierenden Effekten sind. Demzufolge haben WDM und Einkanalsysteme ähnliche optimale Systemparameter, was ein einfaches System- und Kapazitätsupgrade ermöglichen würde. Des weiteren wurde gezeigt, dass für die Realisierung von DWDM Systemen eine schmalbandige optische Filterung sowohl am Sender als auch am Empfänger notwendig ist, deren Folge die Zerstörung der RZ Pulsform ist, wodurch die untersuchten RZ und NRZ basierten Modulationsformate identische Übertragungseigenschaften in DWDM Systemen aufweisen. Eine ähnliche Tendenz wurde auch bei manchen neuen Formaten (z.B. alCNRZ) beobachtet, was mit einem breiten Signalspektrum zu erklären ist. Auf der anderen Seite zeigten alternierend polarisierte Modulationsverfahren (z.B. alPNRZ) auch in DWDM Systemen eine Verbesserung hinsichtlich Filtertoleranz und Toleranz zu Mehrkanaleffekten (z.B. XPM), und empfählen sich als optimaler Kandidat für die zukünftigen 40 Gbit/s Systeme. Es wurde gezeigt, dass der optimale Fasertyp für eine DWDM Übertragung weitgehend unabhängig vom Modulationsformat ist und dass Faser eine möglichst hohe Dispersion besitzen sollen, um eine Unterdrückung der Mehrkanaleffekte ermöglichen zu können. Um zu erkennen, wie eine weitere Verbesserung der Übertragungseigenschaften in 40 Gbit/s Systemen ermöglicht werden könnte, wurden Verfahren wie orthogonal polarisierte Kanäle sowie phase shift keying (PSK) basierte Modulationsformate (z.B. DPSK, DQPSK) untersucht. Es wurde gezeigt, dass die orthogonale Polarisation zwischen den Kanälen als eine Verbesserungsmethode auf eine Übertragungslänge von ca. 200 km begrenzt ist. PSK-Formate ermöglichen eine Verbesserung der Übertragungseigenschaften der Strecke, wobei die notwendigen komplizierten Sender- und Empfängerrealisierungen vom Nachteil sein könnten.The focus of this work was set on 40 Gb/s based optical transmission systems with a varying number of channels and various spectral efficiencies in order to investigate the potential of 40 Gb/s technologies for the implementation in the next generation optical transmission networks. The results of this work can be used as design guidelines enabling a better understanding of propagation limitations in high bit rate transmission systems and give useful insights needed for the capacity upgrade of existing transmission lines. Using conventional amplitude-shift-keying (ASK) based modulation formats and by the author proposed novel modulation formats, the optimization of the system settings is performed in 40 Gb/s based single channel, wavelength division multiplex (WDM) and dense WDM (DWDM) transmission lines, in order to enable a comparison between different modulation formats in terms of the total transmission distance and the maximum achievable spectral efficiency. The signal generation and dominant transmission characteristics of various conventional non return-to-zero (NRZ), return-to-zero (RZ), duobinary, single side band RZ (SSB-RZ), carrier suppressed RZ (CSRZ) - and novel modulation formats alternate chirped NRZ (alCNRZ), novel chirped RZ (nCRZ), alternate polarized (N)RZ (alP(N)RZ) were introduced. The idea behind the development of novel modulation formats was the performance improvement of the existing transmission lines with possibly low signal generation complexity, employing conventional ASK-based receiver configuration for the signal detection. Dividing all modulation formats in two groups NRZ- and RZ-based - their tolerances to linear and nonlinear transmission disturbances are investigated in single channel transmission, indicating that an implementation of NRZ-based modulation formats provides a better dispersion tolerance, but suffers from strong nonlinear limitations. The use of novel NRZ-based formats enables a significant improvement of nonlinear transmission characteristics at the cost of a slightly increased transmitter complexity. RZ-based formats are characterized by an increased sensitivity to residual dispersion and a significant nonlinear tolerance. It is shown that an additional phase or polarization modulation of RZ pulses enables more compact signal spectra and a further improvement of nonlinear transmission robustness, thus enlarging the maximum transmission distance. Strong intra-channel limitations were indicated as the dominant transmission limitation especially in RZ-based formats characterized by strong interactions of consecutive pulses within the bit stream, due to the fast broadening of short optical pulses at 40 Gb/s. This effect is accompanied by self-phase modulation (SPM) group velocity dispersion (GVD) interplay, which becomes evident in both format groups at larger channel powers. It is shown that the dominance of intra-channel effects requires implementation of transmission fibers with moderate dispersion values. Furthermore, it was shown, that as long as intra-channel effects dominate transmission performance, the best dispersion compensation scheme is characterized by a small amount of dispersion pre-compensation, due to suppression of interactions between adjacent pulses. Thereby, right amount of dispersion pre-compensation is dependent on the modulation format in use, because of the interplay between the pulse internal chirp induced during modulation and the local dispersion in transmission line. The importance of pre-compensation increases in long-haul transmission lines employing dispersion compensation on a span-by-span basis, because of constructive superposition of intrachannel cross-phase modulation (IXPM) contributions in each span. The modulation formats employing polarization switching between consecutive pulses were identified as best solution for the performance enhancement in 40 Gb/s single channel based transmission lines. The 40 Gb/s based WDM systems with spectral efficiency of 0.4 bit/s/Hz showed identical transmission behavior as in single channel transmission for all modulation formats, which can be explained by the dominance of single-channel effects in 40 Gb/s systems with a channel spacing of 100 GHz. This leads to the conclusion that a system upgrade from single channel to WDM at 40 Gb/s channel data rate can be made using identical transmission infrastructure. As in the single channel case, RZ-based formats indicated a significant robustness to nonlinear propagation effects, which could be further improved by the use of novel modulation formats. Basically, RZ-based modulation formats outperform the NRZ-based ones in 40 Gb/s single channel and WDM transmissions, and transmission advantages of RZ based formats become even more evident with an increased transmission distance. It was shown that an increase of spectral efficiency to 0.8 bit/s/Hz in 40 Gb/s based DWDM systems results in increased pulse distortions, because of the reduced tolerance to implemented narrow-band filtering and larger impact of multi-channel nonlinearities (particularly XPM). The differences between RZ- and NRZ-based modulation formats vanish in DWDM transmissions, because of the distortion of RZ pulse shape due to narrow-band filtering needed at the transmitter side. It was shown that transmission performance of DWDM systems could profit from implementation of transmission fibers with a large chromatic dispersion, due to suppression of multi-channel effects independently of the modulation format in use. Accordingly, already deployed fibers (e.g. G.652) can be further used in next generation of DWDM transmission systems. Furthermore, considering concatenation of identical spans in a DWDM transmission line, it was observed that XPM-induced impacts superpose constructively from span to span independently of the implemented dispersion compensation scheme, resulting in an transmission penalty, which is in high power regime proportional to number of concatenated spans. This behavior enables together with already know transmission rules (e.g. Pmax) an efficient estimation of the maximum transmission performance and maximum transmission distance in 40 Gb/s DWDM systems. This work is completed by representation of some promising technologies, e.g. polarization orthogonality between the channels or phase-shift-keying (PSK) based modulation formats, which enable a further increase of spectral efficiency (beyond 0.8 bit/s/Hz) and an enhanced maximum transmission distance. The investigations of PSK-based modulation formats showed that not all recently proposed PSK-based system could compete with ASK-based formats for implementation in DWDM systems. Differential quadrature PSK (DQPSK) based modulation formats were identified as a potential candidate for the implementation in future spectrally efficient DWDM systems

Management of fiber physical effects in high-speed optical communication and sensor systems

Ph.DDOCTOR OF PHILOSOPH

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

Chromatic dispersion compensation in 40 Gbaud optical fiber WDM phase-shift-keyed communication systems

von Ahmad Fauzi AbasPaderborn, Univ., Diss., 200

Wavelength tunable transmitters for future reconfigurable agile optical networks

Wavelength tuneable transmission is a requirement for future reconfigurable agile optical networks as it enables cost efficient bandwidth distribution and a greater degree of transparency. This thesis focuses on the development and characterisation of wavelength tuneable transmitters for the core, metro and access based WDM networks. The wavelength tuneable RZ transmitter is a fundamental component for the core network as the RZ coding scheme is favoured over the conventional NRZ format as the line rate increases. The combination of a widely tuneable SG DBR laser and an EAM is a propitious technique employed to generate wavelength tuneable pulses at high repetition rates (40 GHz). As the EAM is inherently wavelength dependant an accurate characterisation of the generated pulses is carried out using the linear spectrogram measurement technique. Performance issues associated with the transmitter are investigated by employing the generated pulses in a 1500 km 42.7 Gb/s circulating loop system. It is demonstrated that non-optimisation of the EAM drive conditions at each operating wavelength can lead to a 33 % degradation in system performance. To achieve consistent operation over a wide waveband the drive conditions of the EAM must be altered at each operating wavelength. The metro network spans relatively small distances in comparison to the core and therefore must utilise more cost efficient solutions to transmit data, while also maintaining high reconfigurable functionality. Due to the shorter transmission distances, directly modulated sources can be utilised, as less precise wavelength and chirp control can be tolerated. Therefore a gain-switched FP laser provides an ideal source for wavelength tuneable pulse generation at high data rates (10 Gb/s). A self-seeding scheme that generates single mode pulses with high SMSR (> 30 dB) and small pulse duration is demonstrated. A FBG with a very large group delay disperses the generated pulses and subsequently uses this CW like signal to re-inject the laser diode negating the need to tune the repetition rate for optimum gain-switching operation. The access network provides the last communication link between the customer’s premises and the first switching node in the network. FTTH systems should take advantage of directly modulated sources; therefore the direct modulation of a SG DBR tuneable laser is investigated. Although a directly modulated TL is ideal for reconfigurable access based networks, the modulation itself leads to a drift in operating frequency which may result in cross channel interference in a WDM network. This effect is investigated and also a possible solution to compensate the frequency drift through simultaneous modulation of the lasers phase section is examined

All-optical processing systems based on semiconductor optical amplifiers

Doutoramento em Engenharia ElectrotécnicaNesta tese investigam-se e desenvolvem-se dispositivos para processamento integralmente óptico em redes com multiplexagem densa por divisão no comprimento de onda (DWDM). O principal objectivo das redes DWDM é transportar e distribuir um espectro óptico densamente multiplexado com sinais de débito binário ultra elevado, ao longo de centenas ou milhares de quilómetros de fibra óptica. Estes sinais devem ser transportados e encaminhados no domínio óptico de forma transparente, sem conversões óptico-eléctrico-ópticas (OEO), evitando as suas limitações e custos. A tecnologia baseada em amplificadores ópticos de semicondutor (SOA) é promissora graças aos seus efeitos não-lineares ultra-rápidos e eficientes, ao potencial para integração, reduzido consumo de potência e custos. Conversores de comprimento de onda são o elemento óptico básico para aumentar a capacidade da rede e evitar o bloqueio de comprimentos de onda. Neste trabalho, são estudados e analisados experimentalmente métodos para aumentar a largura de banda operacional de conversores de modulação cruzada de ganho (XGM), a fim de permitir a operação do SOA para além das suas limitações físicas. Conversão de um comprimento de onda, e conversão simultânea de múltiplos comprimentos de onda são testadas, usando interferómetros de Mach-Zehnder com SOA. As redes DWDM de alto débito binário requerem formatos de modulação optimizados, com elevada tolerância aos efeitos nefastos da fibra, e reduzida ocupação espectral. Para esse efeito, é vital desenvolver conversores integramente ópticos de formatos de modulação, a fim de permitir a interligação entre as redes já instaladas, que operam com modulação de intensidade, e as redes modernas, que utilizam formatos de modulação avançados. No âmbito deste trabalho é proposto um conversor integralmente óptico de formato entre modulação óptica de banda lateral dupla e modulação óptica de banda lateral residual; este é caracterizado através de simulação e experimentalmente. Adicionalmente, é proposto um conversor para formato de portadora suprimida, através de XGM e modulação cruzada de fase. A interligação entre as redes de transporte com débito binário ultra-elevado e as redes de acesso com débito binário reduzido requer conversão óptica de formato de impulso entre retorno-a-zero (RZ) e não-RZ. São aqui propostas e investigadas duas estruturas distintas: uma baseada em filtragem desalinhada do sinal convertido por XGM; uma segunda utiliza as dinâmicas do laser interno de um SOA com ganho limitado (GC-SOA). Regeneração integralmente óptica é essencial para reduzir os custos das redes. Dois esquemas distintos são utilizados para regeneração: uma estrutura baseada em MZI-SOA, e um método no qual o laser interno de um GC-SOA é modulado com o sinal distorcido a regenerar. A maioria dos esquemas referidos é testada experimentalmente a 40 Gb/s, com potencial para aplicação a débitos binários superiores, demonstrado que os SOA são uma tecnologia basilar para as redes ópticas do futuro.This thesis investigates and develops all-optical processing devices for wavelength division multiplexing networks (DWM) of the future. The ultimate goal of optical networks is to transport and deliver a densely multiplexed spectrum, populated by ultra-high bit rate signals over hundreds or thousands of kilometers of optical fiber. Such signals should be transported and routed transparently in the optical domain, without recurring to optic-electro-optic (OEO) conversions, avoiding its limitations and costs. Semiconductor optical amplifier (SOA) based technology is a promising building block due to its inherent ultra-fast and efficient non-linear effects, potential for integration, low power consumption and cost. Wavelength converters are the basic optical functionality to increase the network throughput and avoid wavelength blocking. Methods to increase the operation bandwidth of cross-gain modulation (XGM) converters are studied and experimentally assessed to enable operation beyond the physical constraints of SOA. Single and multi-wavelength conversion exploiting crossphase modulation (XPM) in Mach-Zehnder interferometer with semiconductor optical amplifiers (MZI-SOA) is tested. High bit rate DWDM networks require optimized modulation formats with enhanced tolerance to fiber impairments and reduced spectral tolerance. As a consequence, it is crucial to develop all-optical modulation formats between legacy on-off-keying networks and networks employing advanced modulation formats. An all-optical format converter between optical double sideband (ODSB) and optical vestigial sideband (OVSB) based on SOA self-phase modulation is proposed and thoroughly characterized by simulations and experimental tests. A converter, which uses a mix of XGM and XPM to allow simultaneous pulse and modulation format conversion to the carrier suppressed format, is proposed. The interface between ultra-high bit rate transport networks and lower bit rate access networks requires optical pulse format conversions between return-tozero (RZ) and non-return-to-zero (NRZ). Two different structures are proposed and investigated. The first is based on detuned filtering of XPM converted signal; while the second uses the dynamics of the internal laser of a gainclamped SOA. All-optical regeneration is one of the most sought functionalities to reduce network costs. Regeneration is achieved in this work through two simple setups: a MZI-SOA based structure, and a method in which the internal laser from a GC-SOA is modulated with the input distorted signal. Most applications are experimentally validated at 40 Gb/s, with potential for even higher bit rates, demonstrating that SOA can be one of the key elements for the next generation of optical networks