Power and wavelength polarization bistability with very wide hysteresis cycles in a 1550nm-VCSEL subject to orthogonal optical injection

We have measured optical power and wavelength polarization bistability in a 1550nm-Vertical Cavity Surface-Emitting Laser (VCSEL) subject to orthogonally-polarized optical injection into the orthogonal polarization of the fundamental transverse mode. Optical bistability with very wide hysteresis cycles, up to four times wider than previously reported results has been measured for both the optical power and wavelength domain. We also report the experimental observation of three different shapes of polarization bistability, anticlockwise, clockwise and X-Shape bistability, all of them with wide hysteresis cycles. This rich variety of behaviour at the important wavelength of 1550 nm offers promise for the use of VCSELs for all-optical signal processing and optical switching/routing applications. ©2009 Optical Society of America

Optical performance monitoring in optical packet-switched networks

Para poder satisfacer la demanda de mayores anchos de banda y los requisitos de los nuevos servicios, se espera que se produzca una evolución de las redes ópticas hacia arquitecturas reconfigurables dinámicamente. Esta evolución subraya la importancia de ofrecer soluciones en la que la escalabilidad y la flexibilidad sean las principales directrices. De acuerdo a estas características, las redes ópticas de conmutación de paquetes (OPS) proporcionan altas capacidades de transmisión, eficiencia en ancho de banda y excelente flexibilidad, además de permitir el procesado de los paquetes directamente en la capa óptica. En este escenario, la solución all-optical label switching (AOLS) resuelve el cuello de botella impuesto por los nodos que realizan el procesado en el dominio eléctrico. A pesar de los progresos en el campo del networking óptico, las redes totalmente ópticas todavía se consideran una solución lejana . Por tanto, es importante desarrollar un escenario de migración factible y gradual desde las actuales redes ópticas basadas en la conmutación de circuitos (OCS). Uno de los objetivos de esta tesis se centra en la propuesta de escenarios de migración basados en redes híbridas que combinan diferentes tecnologías de conmutación. Además, se analiza la arquitectura de una red OPS compuesta de nodos que incorporan nuevas funcionalidades relacionadas con labores de monitorización y esquemas de recuperación. Las redes ópticas permiten mejorar la transparencia de la red, pero a costa de aumentar la complejidad de las tareas de gesión. En este escenario, la monitorización óptica de prestaciones (OPM) surge como una tecnología capaz de facilitar la administración de las redes OPS, en las que cada paquete sigue su propia ruta en la red y sufre un diferente nivel de degradación al llegar a su destino. Aquí reside la importancia de OPM para garantizar los requisitos de calidad de cada paquete.Vilar Mateo, R. (2010). Optical performance monitoring in optical packet-switched networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8926Palanci

Towards all-optical label switching nodes with multicast

Fiber optics has developed so rapidly during the last decades that it has be- come the backbone of our communication systems. Evolved from initially static single-channel point-to-point links, the current advanced optical backbone net- work consists mostly of wavelength-division multiplexed (WDM) networks with optical add/drop multiplexing nodes and optical cross-connects that can switch data in the optical domain. However, the commercially implemented optical net- work nodes are still performing optical circuit switching using wavelength routing. The dedicated use of wavelength and infrequent recon¯guration result in relatively poor bandwidth utilization. The success of electronic packet switching has inspired researchers to improve the °exibility, e±ciency, granularity and network utiliza- tion of optical networks by introducing optical packet switching using short, local optical labels for forwarding decision making at intermediate optical core network nodes, a technique that is referred to as optical label switching (OLS). Various research demonstrations on OLS systems have been reported with transparent optical packet payload forwarding based on electronic packet label processing, taking advantage of the mature technologies of electronic logical cir- cuitry. This approach requires optic-electronic-optic (OEO) conversion of the op- tical labels, a costly and power consuming procedure particularly for high-speed labels. As optical packet payload bit rate increases from gigabit per second (Gb/s) to terabit per second (Tb/s) or higher, the increased speed of the optical labels will eventually face the electronic bottleneck, so that the OEO conversion and the electronic label processing will be no longer e±cient. OLS with label processing in the optical domain, namely, all-optical label switching (AOLS), will become necessary. Di®erent AOLS techniques have been proposed in the last ¯ve years. In this thesis, AOLS node architectures based on optical time-serial label processing are presented for WDM optical packets. The unicast node architecture, where each optical packet is to be sent to only one output port of the node, has been in- vestigated and partially demonstrated in the EU IST-LASAGNE project. This thesis contributes to the multicast aspects of the AOLS nodes, where the optical packets can be forwarded to multiple or all output ports of a node. Multicast capable AOLS nodes are becoming increasingly interesting due to the exponen- tial growth of the emerging multicast Internet and modern data services such as video streaming, high de¯nition TV, multi-party online games, and enterprise ap- plications such as video conferencing and optical storage area networks. Current electronic routers implement multicast in the Internet protocol (IP) layer, which requires not only the OEO conversion of the optical packets, but also exhaus- tive routing table lookup of the globally unique IP addresses. Despite that, there has been no extensive studies on AOLS multicast nodes, technologies and tra±c performance, apart from a few proof-of-principle experimental demonstrations. In this thesis, three aspects of the multicast capable AOLS nodes are addressed: 1. Logical design of the AOLS multicast node architectures, as well as func- tional subsystems and interconnections, based on state-of-the-art literature research of the ¯eld and the subject. 2. Computer simulations of the tra±c performance of di®erent AOLS unicast and multicast node architectures, using a custom-developed AOLS simulator AOLSim. 3. Experimental demonstrations in laboratory and computer simulations using the commercially available simulator VPItransmissionMakerTM, to evaluate the physical layer performance of the required all-optical multicast technolo- gies. A few selected multi-wavelength conversion (MWC) techniques are particularly looked into. MWC is an essential subsystem of the AOLS node for realizing optical packet multicast by making multiple copies of the optical packet all-optically onto di®er- ent wavelengths channels. In this thesis, theMWC techniques based on cross-phase modulation and four-wave mixing are extensively investigated. The former tech- nique o®ers more wavelength °exibility and good conversion e±ciency, but it is only applicable to intensity modulated signals. The latter technique, on the other hand, o®ers strict transparency in data rate and modulation format, but its work- ing wavelengths are limited by the device or component used, and the conversion e±ciency is considerably lower. The proposals and results presented in this thesis show feasibility of all-optical packet switching and multicasting at line speed without any OEO conversion and electronic processing. The scalability and the costly optical components of the AOLS nodes have been so far two of the major obstacles for commercialization of the AOLS concept. This thesis also introduced a novel, scalable optical labeling concept and a label processing scheme for the AOLS multicast nodes. The pro- posed scheme makes use of the spatial positions of each label bit instead of the total absolute value of all the label bits. Thus for an n-bit label, the complexity of the label processor is determined by n instead of 2n

Fundamentals and applications of spatial dissipative solitons in photonic devices : [Chapter 6]

We review the properties of optical spatial dissipative solitons (SDS). These are stable, self‐localized optical excitations sitting on a uniform, or quasi‐uniform, background in a dissipative environment like a nonlinear optical cavity. Indeed, in optics they are often termed “cavity solitons.” We discuss their dynamics and interactions in both ideal and imperfect systems, making comparison with experiments. SDS in lasers offer important advantages for applications. We review candidate schemes and the tremendous recent progress in semiconductor‐based cavity soliton lasers. We examine SDS in periodic structures, and we show how SDS can be quantitatively related to the locking of fronts. We conclude with an assessment of potential applications of SDS in photonics, arguing that best use of their particular features is made by exploiting their mobility, for example in all‐optical delay lines

Label-controlled optical switching nodes

Optical networks are evolving from initially static optical circuits and subsequently optical circuit switching towards optical packet switching in order to take advan- tage of the high transport capacity made available by WDM systems in a more °exible and e±cient way. Optically labeling of packets and routing the packets's payload optically under control of its label allows the network nodes to route and forward IP data without having to process the payload, thus keeping it in the optical domain; this is a promising solution to avoid electronic bottlenecks in routers. All-optical label switching can therefore be used to route and forward packets independent of their length and payload bitrate. Several optical signal labeling techniques have been proposed in previous re- search reported in literature; orthogonal labeling and time-serial labeling have been studied in this thesis. This thesis studies two orthogonal modulation label- ing techniques: one based on FSK labels with an IM payload, and another one on SCM labeling for a DPSK modulated payload. A time-serial labeling method based on IM labels with IM or DPSK payload is also presented and studied. The ¯rst two techniques assume electronic processing of the labels in the node, and hence assume that labels can be transmitted at a much lower bitrate than the payload data rate. The third technique assumes all-optical signal processing in the nodes, capable of handling a label at the same bitrate or slightly lower than the payload data. Labels at low bitrate in comparison with the payload bitrate are desirable in systems where the label processing will be conducted in the electrical domain, while labels at the same bitrate as the payload can be used in systems where the processing is conducted in the optical domain, exploiting all-optical processing techniques. These three techniques have been chosen because they are compatible with the existing networks, since the modulation format, bitrates, transmission properties, and other features of the signals are similar to the ones used for commercially available applications. Thus, they can be considered important candidates for migration scenarios from optical circuit switching towards optical burst switching networking. Orthogonal labeling based on FSK/IM is a promising scheme for implementing the labeling of optical signals, and it is the technology of choice in the STOLAS project. This technique o®ers advantageous features such as a relaxed timing de- lineation between payload and label, and ease of label erasure and re-writing of new labels. By using wavelength-agile tunable laser sources with FSK modula- tion capability, wavelength converters, and passive wavelength routing elements, a scalable modular label-controlled router featuring high reliability can be built. In this thesis, several aspects of the physical parameters of an FSK/IM labeling scheme within a routing node have been studied and presented. Optical ¯ltering requires special care, since the combined FSK/IM scheme has a broader spectrum than that of pure intensity modulated signals. The requirements on the limited extinction ratio for the IM signal can be relaxed at low bitrates of the label signal or, alternatively, by introducing data encoding. Optical labeling by using FSK/IM represents a simple and attractive way of implementing hybrid optical circuit and burst switching in optical networks. Architecturally, similar advantages can be mentioned for the second orthogo- nal labeling technique studied in this thesis, based on SCM labels and a DPSK payload. In-band subcarriers carrying low bitrate labels located at a frequency equal to half the bitrate of the payload signal can be inserted introducing only low power penalties. Wavelength conversion can be implemented by using passive highly nonlinear ¯bers and exploiting the four-wave mixing e®ect. This thesis also studies the design of two functional blocks of an all-optical core node proposed in the LASAGNE project, namely the all-optical label and payload separator and the wavelength converter unit for a time-serial labeling scheme. The label and payload processor can be realized exploiting nonlinear e®ects in SOAs. An implementation using polarization division multiplexing to transport the external control light for an IM/IM time-serial scheme was demon- strated. Label and payload processors with self-contained control signals were also demonstrated, either using a DPSK signal to simultaneously transport the payload data and the control signal or inserting a CW dummy in between the label and the payload, which were based on IM-RZ format. A study on single- and multi- wavelength conversion based on FWM in a HNLF was presented. This approach allows transparent wavelength conversion (independent of the data format used) at high bitrates (the nonlinear e®ects in a ¯ber are obtained at ultrafast speeds). The labeling techniques explored have indicated a viable way of migration towards optical burst packet switched networks while signi¯cantly improving the throughput of the routing nodes

Birefringent fibre ring resonators: Analysis and stabilization techniques

The polarization stability of single-mode fibre resonators has been recognized as a potential problem in their operation. One method to overcome the polarization drift is to use a polarization-maintaining optical fibre, in the resonator system. Even this kind of resonators, still suffer from environmentally-induced polarization instabilities. Depending on the type of resonator, these instabilities are manifest as a split resonant dip, reduced finesse, reduced fringe modulation, fringe asymmetry, and unequal spacing between successive fringes. If we assume that a non zero amount of polarization crosstalk at the coupler is inevitable, then there is only one ideal type of resonator which is free from instabilities: a resonator made from polarizing fibre (or one that incorporates a perfectly aligned polarizer in the loop). The fringe shape variation can be reduced if the resonator is made with a deliberate 90 deg. axis twist at the splice or coupler, or if it is made with a polarization-selective coupler. No practical technique has been demonstrated so far, for producing consistently stable resonators with high finesse, using birefringent fibre. This is because the tolerable amount of coupler polarization crosstalk is very small, and the above ideal form is not easily made. It is therefore important to compare the output stability of the different resonator types as well as to investigate possible techniques for passive or active stabilization of the output. In this thesis work we have developed a experimentally verifiable resonator model that can be applied to different resonator types with minor modifications. We have derived tolerances for the coupler polarization crosstalk, splice alignment, and input polarization mode purity necessary for optimum operation of each type. A fringe shape stabilization system has been constructed, for use with fibre ring resonators with power exchange between the birefringent axes. The system works by keeping the depth of successive resonant dips equal, through a feedback electronic servo system, that controls the fibre birefringence. Two schemes for controlling the fibre birefringence are investigated