Wavelength Division Multiplexing

Wavelength conversion is an essential function in wavelength-division-multiplexing (WDM) optical networks, as it enables better utilization of bandwidth and reduces blocking probabilities. This work presents, for the first time, a fully integrated transceiver solution to wavelength conversion in which all microwave signals are confined on a single InP chip. This device architecture, referred to as a photocurrent-driven wavelength converter (PD-WC), is particularly attractive due to the potential for low power dissipation, high bandwidth, data regeneration, and no optical output filtering requirement unlike many all-optical implementations [1]. The PD-WC approach consists of an interconnected receiver and transmitter such that photocurrent from an optically pre-amplified receiver is used to drive a modulator, which functions to translate the signal onto any output wavelength within the range of a widely tunable laser. Previous widelytunable PD-WC demonstrations have required high speed probes, bias-T's, and in some cases complex bias circuitry [1]. In this work, a termination resistor and DC-blocking capacitor are integrated with an electroabsorption modulator (EAM) based PD-WC such that only DC biases are necessary for device operation and no microwave signal must travel off the chip. This widely-tunable device demonstrates error free 10 Gb/s conversion and utilizes both a simple, single-regrowth fabrication and a simple bias configuration. The PD-WC is essentially a monolithically integrated transceiver within a compact footprint of 3.1 by 0.5 mm. The transmitter ridge consists of a widely tunable sampled grating (SG) DBR laser followed by semiconductor optical amplifier (SOA) and a 400 m long EAM. The receiver ridge consists of two SOAs followed by a p-i-n quantum well photodetector (QW-PD). The ridge width of the second SOA is flared (3 to 9 m) to achieve a 3-dB saturation power greater than 15 dBm. The QW-PD is 20 m long with a tapered ridge (9 to 7 m) to prevent saturation at the front end while minimizing the total capacitance [2]. Benzocyclobutene (BCB), a low-k dielectric, is defined underneath the QW-PD and EAM electrodes for reduced parasitic capacitance and a 75 m long microstrip line above the BCB connects the QW-PD to the EAM electrode in a traveling wave configuration. The EAM is terminated with a 35 NiCr resistor followed by a large (~30 pF) on-chip parallel-plate capacitor in series, providing an RF path to ground. An additional chip capacitor is added in parallel on the submount to provide a low impedance ground path for frequencies less than 500 MHz. The device was fabricated on a dual quantum well (DQW) base structure with a semi-insulating Fedoped InP substrate. The DQW consists of a set of 7 offset quantum wells ( PL =1542 nm) above the waveguide layer, for gain in laser and amplifier regions, and 8 shallow quantum wells ( PL =1455 nm) centered in the waveguide for modulation efficiency. The offset wells were selectively etched from all passive and modulation regions before the p-type InP cladding was grown. Wavelength conversion experiments at 10 Gb/s in the non-return to zero (NRZ) format demonstrated open eye diagrams with output extinction ratios ranging from 8.0 to 6.6 dB for output wavelengths from 1527-1553 nm. Bit error rate measurements achieved 10 Gb/s error free wavelength conversion over the same 25 nm output wavelength tuning range. In this tuning range, the power penalty of wavelength conversion ranged from 1.5 -2.5 dB compared to back to back transmission. The input power for these measurements was -4.5 dBm neglecting coupling losses. DC characterization experiments showed the receiver SOA gain to be greater than 18 dB and QW-PD output to be linear up to 25 mA of photocurrent. The EAM demonstrated peak DC extinction slope efficiencies from 10 to 20 dB/V for wavelengths from 1527 to 1553 nm.

This study aims to evaluate the effectiveness of selected color filter film for demultiplexer construction where only signals with certain wavelengths are allowed to pass through the demultiplexer while the other signal that carrying different wavelengths are absorbed. Characterization testing and analysis is done based on recorded data. Demultiplexer components are characterized by the Same Source at Different Filters (SSDF) and performance of transmitted signal are measured. The developed demultiplexer is effective in short range communication, using low cost components and simple techniques. Communication range for short range communication is maximized by combining wavelengths and send through a single strand of fiber by means of Wavelngth Division Multiplexing (WDM). Only signals with certain wavelengths are allowed to pass through the multiplexer. The rest are absorbed. Several measures are made to ensure efficiency, such as testing and measurement on parametres contributing to loss. Best filters are selected based on their ability to block certain wavelengths while letting others ro pass through efficiently. The blocking feature is important to avoid phenomena of crosstalk occurs in the system.

We demonstrate 32.5 Tbit/s 16QAM Nyquist WDM transmission over a total length of 227 km of SMF-28 without optical dispersion compensation. A number of 325 optical carriers are derived from a single laser and encoded with dual-polarization 16QAM data using sinc-shaped Nyquist pulses. As we use no guard bands, the carriers have a spacing of 12.5 GHz equal to the Nyquist bandwidth of the data. We achieve a high net spectral efficiency of 6.4 bit/s/Hz using a software-defined transmitter which generates the electrical modulator drive signals in real-time.

Mobile network operators are facing ever-increasing traffic demands because of the numerous data-hungry applications used by subscribers nowadays. As a result, technologies that support high bandwidth and network availability have become essential. One such technology is dense wavelength division multiplexing (DWDM). This study investigated the evolution of an optical add/drop multiplexer (OADM), which is one of the key components of DWDM technology. The goal of this research was to investigate how the evolution of an OADM has contributed to network survivability and bandwidth enhancement in DWDM optical networks. A thorough search of the literature on an OADM was undertaken using data sources like Google Scholar, Elsevier, ResearchGate, ScienceDirect, Springer, and DWDM vendor manuals. The study found that in order to address present and future DWDM optical network demands, a reconfigurable optical add/drop multiplexer (ROADM) deployed over flexgrid spectrum is essential. The most advanced iteration of a ROADM supports colorless, directionless, contentionless, and flex-grid functionalities, resulting in the most robust, flexible, and future-proof DWDM optical network. The study further found that flex-grid technology supports uplinks with high line rates and has superior spectral efficiency.

We present a numerical simulation study on the effect of the linewidth enhancement factor (α) of semiconductor laser and dispersion management methods of optical fibers on the performance of 40-Gb/s directly-modulated fiber links and their application in WDM systems. The dispersion management methods include the use of non-zero dispersion-shifted fiber (NZ-DSF), dispersion-compensating fiber (DCF), and fiber Bragg grating (FBG). The optimal values of the α-parameter and the best dispersion management method are applied to design and simulate a four-channel × 40-Gb/s WDM fiber system. The obtained results show that the increase in the α-parameter and/or fiber length reduces the performance of both the 40-Gb/s optical link and the WDM system. Regarding the 40-Gb/s optical link, when α = 1, using-NZ-DSF or + NZ-DSF, DCF with SSMF, and FBG with SSMF work to increase the transmission length from 1.6 km of a standard single-mode fiber (SSMF) to 7.2, 26.5, and 40 km, respectively. Whereas at α = 3.5, the maximum transmission length reaches 1.2 km when using SSMF,-NZ-DSF, or + NZ-DSF, while it increases to 13 and 35 km when using DCF with SSMF, and FBG with SSMF, respectively. In the designed WDM system, the use of FBG with SSMF is predicted as the most effective method for dispersion management. The maximum transmission length reaches 25 km when α = 1, but reduces to 12 km when α = 3.5.

In scheduling the transmission of messages in a WDM network, we are facing not only the channel assignment problem but also message sequencing problem In this paper, we propose and evaluate a new reservationbased message scheduling algorithm for single-hop, WDM passive star lightwave network which addresses both the assignment aspect and the sequencing aspect of the problem. We compare the performance of the algorithm which only addresses the channel assignment issue with the performance of our new algorithm theoretically and experimentally and demonstrate that our new algorithm has significant improvement over the performance of a WDM network with a scheduling algorithm that does not consider the message sequencing problem. As a result, we anticipate that this research can open new directions into the problem of message scheduling on WDM networks.

Message sequencing and channel assignment are two important issues that need to be addressed in scheduling vuriable-length messages in a Wavelength Division Multiplexing (WDM) network. Channel assignment addresses the problem of choosing an appropriate data channel via which a message is transmitted to a node. This problem has been addressed extensively in the literature. On the other hand, message sequencing which addresses the order in which messages are sent, has rarely been addressed. In this papel; we propose a set of scheduling techniques for single-hop WDM passive star networks which address both the sequencing aspect and the assignment aspect of the problem. In particulal; we develop two priority schemes for sequencing messages in a WDM network in order to increase the overall performance of the network. We evaluate the proposed algorithms, using analytical modeling and discreteevent simulations, by comparing their performance with state-of the-art scheduling algorithms that only address the assignment problem. We find that signijkant improvement in perj5ormance can be achieved using our scheduling algorithms where message sequencing and channel assignment are simultaneously taken into consideration.

Microring resonator modulators (MRM) alongwith four-level pulse amplitude modulation (PAM4) can efficiently scale to higher data-rates on a single channel when combined with CMOS chips. In this work, we present an all-silicon ringbased optical transmitter (TX) which consists of a two-segment MRM heterogeneously integrated over wirebonds with a CMOS IC implemented in 28nm CMOS process. The MRM device characteristics are modeled in Verilog-A which enables efficient co-simulation. The CMOS TX consists of individual PAM2 AC-coupled pulsed-cascode high-swing voltage-mode drivers for MSB/LSB segments. The drivers achieve a 3.42 Vppd swing and offer independent level-tuning, edge-rate control, and asymmetric post-cursor pre-emphasis on rising and falling edges. The proposed TX operates at 80 Gb/s PAM4 with a power efficiency of 3.66 pJ/bit.

Using optical add-drop multiplexer/remover multiplexer (OADM), it is possible to add or remove wavelengths and change or route them through the various nodes and networks. At this moment, key problems in add-drop multiplexer (ADM) are the bandwidth, modulation format, and reuse wavelength. In this article, the Optisystem software simulation is used as a platform to design, test, and verify the method applied to the current work; the OADM is proposed based on the metro network to get distribution between nodes over a transmission link; OADM analysis was presented with four channels (193.1, 193.2, 193.3, and 193.4 THz) at total bandwidth of 1.6 Tb/s, none-return-to-zero (NRZ), and return to zero coding types. Experiment one shows that the average output power is -17.997 dBm, the average drop power is -17.997 dBm, and the average add power is -18.338 dBm, the average gain is -0.0429 dB, the average noise figure is 0 dB, the average power input signal is 10.679 dBm, the average of power output signal is 10.633 dBm, and the average output optical signal-to-noise ratio (OSNR) is 0 dB, However, the second experiment shows that the average output power is -24.238 dBm, the average drop power is -24.288 dBm, and the average add power is -24.753 dBm, the average gain is -0.0417 dB, the average noise figure is 0 dB, average power input signal is 7.691 dBm, average of power output signal is 7.677 dBm, and the average output OSNR 0 dB. The system supports four input channels, four add channels, four output channels, and four drop channels. The results are acceptable after three spans of Solitons fiber with 600 km length, 200 km for each span. Nonetheless, it is believed that it is well justified to adopt these schemes in the current optical network with a low cost for overall expenditure.

A single-longitudinal-mode multiwavelength fiber ring laser is proposed and demonstrated. The single-longitudinal-mode operation is realized using a fiber loop mirror with a saturable absorber. The fiber loop mirror acts as a passive self-tracking narrow multiband optical filter. Single-longitudinal-mode multiwavelength lasing is generated by using either a Lyot-Sagnac filter or a fiber grating array.

This study presents a comprehensive numerical and experimental approach to map the nonlinear electro-optic behavior of nematic liquid crystal (LC) cells, with a particular focus on refractive index changes (birefringence) under applied voltage across different cell thicknesses. A numerical simulation program, based on the Oseen-Frank equations, accurately determines the voltage required for birefringence in liquid crystal molecules for varying LC thicknesses and maps the nonlinear refractive index changes over time. Simulations using 5CB liquid crystal at different thicknesses (75, 100, and 125 µm) are validated with experimental results obtained from a liquid crystal-based interferometer utilizing a low finesse polarization-based Fabry-Perot interferometer. This research emphasizes the importance of cell thickness as a critical design parameter and provides a reliable method for characterizing electro-optic phenomena in next-generation liquid crystal devices.

Fibre optic has the key to telecommunication of the future, hence it is among the major building block of telecommunication infrastructure due to its high bandwidth capabilities and low attenuation characteristics that make it ideal for gigabit transmission and beyond. However, it is bottle neck by an important characteristics that often cause incorrect transmission of information at it receiving end known as dispersion, characterized by pulse broadening which hinder the amount of information that can be conveyed as well as distance of transmission. This study carryout measurement of dispersion for 650nm to 1800nm wavelength employing Erbium doped fiber amplifier (EDFA) and collating the result obtained with that acquired without EDFA, the collation however gives impressive result in favour of EDFA technique. The results were further validated with simulation analysis and thus, authenticate the technique employed in the study.

Pulse position modulation (PPM) is introduced downstream of the reflective semiconductor optical amplifier (RSOA)-based single-fiber full-duplex bidirectional wavelength division multiplex passive optical network (WDM PON) to suppress the interference brought by the remodulation effect in the RSOA, Rayleigh backscattering, and reflection of the connection devices. In addition, because of the powerefficient characteristic of the PPM-encoded signals, the power budget shows clear improvement. As the experimental tests indicate, with ∼6 dB extinction ratio (ER) in the downstream signal, the receiving sensitivity of the PPM-encoded channel is ∼2.6 and ∼3 dB higher than that of the NRZ (Non-return to zero)-encoded channel in the downlink and uplink, respectively.

We present the performance analysis of 112 Gb/s × 4 wavelength division multiplexing (WDM) 100 GHz channel spacing polarization division multiplexed-differential quadrature phase shift keying (PDM-DQPSK) optical label switching system with frequency swept coherent detected spectral amplitude code labels. Direct detection is chosen to demodulate the payload by applying a polarization tracker, while 4-bits of 156 Mb/s spectral amplitude code label is coherently detected with a scheme of frequently-swept coherent detection. We optimize the payload laser linewidth as well as the frequency spacing between the payload and label. The label and payload signal performances are assessed by the eye-diagram opening factor (EOF) and bit-error rate (BER) at 10 -9 as a function of the received optical power (ROP) and the optical signal to noise ratio (OSNR). The payload could well be demodulated after 900 km at a bit error rate of 10 -3 using forward error correction (FEC).

Routing and Wavelength Assignment (RWA) is one of the key tasks for the optical network, due to its information transparency and wavelength reuse characteristics. This paper presents heuristic algorithm that can be used for routing and wavelength assignment for All-Optical WDM networks under dynamic arising of calls. We have considered All-Optical Networks (AON) without wavelength conversion and dynamic RWA scheme which is based on the distributed Dijkstra's routing algorithm and first-fit wavelength reservation with a set of 64 wavelengths in random topology and for 500 calls the Call Blocking Ratio (CBR) is 0.55 and simulation time is 5 sec.For different arrival of calls the performance is analysed in terms of blocking probability as well as the simulation time of the heuristic algorithm and has been studied through simulation.

In civil engineering quasi-distributed optical fiber sensors are used for reinforced concrete monitoring, precast concrete monitoring, temperature monitoring, strain monitoring and temperature/strain monitoring. These quasi-distributed sensors necessarily apply some multiplexing technique. However, on many occasions, two or more multiplexing techniques are combined to increase the number of local sensors and then the cost of each sensing point is reduced. In this work, a signal analysis and a new signal demodulation algorithm are reported for a quasi-distributed optic fiber sensor system based on Frequency Division Multiplexing/Wavelength Division Multiplexing (FDM/WDM) and low-precision Fabry-Pérot interferometers. The mathematical analysis and the new algorithm optimize its design, its implementation, improve its functionality and reduce the cost per sensing point. The analysis was corroborated by simulating a quasi-distributed sensor in operation. Theoretical analysis and numeric...

Injection locked quantum-dash laser diode-based comb source is employed in wavelength-division multiplexed (WDM) optical transmission covering ∼1610 nm L-band optical telecommunication window. An aggregate data rate of 192 Gbits/s (3 × 32 GBaud-QPSK reaching 7% FEC overhead) is demonstrated over three 50 GHz separated channels in coherent transmission over a 10 km-long single mode fiber. A thorough investigation of the radio-frequency (RF) characteristics of all channels is carried out in terms of the linewidth, phase, and frequency noises, showing minimum values of 44 kHz, -80 dBc/Hz, and 5.2 × 10 11 Hz 2 /Hz, respectively. Also, an integrated average relative intensity noise of ∼-132 dB/Hz is reported for the central channel. To the best of our knowledge, this constitutes the first report and demonstration of a dense WDM (DWDM) in an extended L-band regime using a comb source.

A homodyne coherent receiver for ultra-dense WDM-PON with off the shelf components is presented. It consists of a conventional DFB, phase switched clock signal, an optical coupler instead of a 90º hybrid, balanced photodetectors and digital signal processing. The phase swing for a DBPSK signal was optimized and the performance was experimentally evaluated in terms of the sensitivity for several laser linewidths. The acceptable frequency offset and clock time delay was also assessed. The results exhibit a sensitivity of -48 dBm at a BER of 10 -3 and indicate a high tolerance to phase noise. OCIS codes: (060.0060) Fiber optics and optical communications; (060.1660) Coherent communications.

Current optical fiber communication is increasingly limited by bottlenecks such
as channel utilization or hardware limitations, highlighting the need for more
efficient systems. Manipulating the information system by encoding the infor-
mation in higher-order bases (binary to hexadecimal) and using permutations
and several properties of tunable lasers, such as phase and wavelength, can pro-
duce higher data transmission speeds. We propose a solution through phase
and chromatic modulation by tuning laser frequencies and laser drive currents
along with permutation encoding. Signals are decoded by spectroscopes, which
detect phase and color after being corrected. Most importantly, this system
operates under the limit established by Shannon’s theorem for noisy channels.
This multi-dimensional approach provides a terabit-scale throughput depending
on the number of lasers in the array (6 Tb/s to 230 Tb/s, or 27 to 32 bits per
symbol per laser). This system gives higher data rates than current telecom
technology. It also offers a higher information density with reduced energy and
cost.

Data: 24 de Maig de 2011 Resum L'objectiu principal plantejat en aquest projecte ha estat optimitzar el pla de control d'un prototipus de xarxa de Commutació de Ràfegues Òptiques (OBS, Optical Burst Switching) del qual ja se'n disposava d'un disseny inicial realitzat en el marc d'un projecte nacional finançat pel Ministeri de Ciència i Tecnologia, juntament amb el projecte Machine de la Fundació i2CAT. En aquests tipus de xarxes, les dades d'usuari s'ensamblen en ràfegues de major longitud en els nodes frontera d'ingrés, i es transmeten passat un temps d'offset. Aquest temps d'offset permet que un paquet de control realitzi la senyalització i reserva de recursos òptics per a que la ràfega pugui commutarse des del node frontera d'origen al node destí, on es realitzarà el desensamblatge de la ràfega en les seves unitats de dades originals. El Pla de Control governa la senyalització del camí entre origen i destinació pel qual la ràfega viatjarà. Per la seva realització s'ha fet un estudi del protocol de reserva de recursos ja implementat en el prototipus OBS, al mateix temps que s'han analitzat les possibles alternatives de mecanismes de reserva de recursos que existeixen en la literatura per aquest tipus de xarxes de commutació òptiques. Derivat d'aquests estudis s'ha proposat un nou mecanisme de reserva de recursos, així com també el seu disseny i implementació, en dues etapes. Finalment s'han dut a terme les proves necessàries per verificar el correcte funcionament de tots els nous elements implementats sobre el prototipus OBS. La implementació del Pla de Control s'ha realitzat sobre unes plaques de desenvolupament hardware/software que integren una FPGA Virtex-4 de Xilinx. La realització del projecte ha implicat part de disseny hardware (VHDL) i part de programació del software de control (en C). Com a resultat s'ha obtingut un prototipus de xarxa OBS molt més estable i robust, no només en les seves transmissions sinó també en altres aspectes com són el seu rendiment i throughput. Amb les següents paraules m'agradaria agrair a totes aquelles persones que han fet possible, en menor o major mesura, que aquest projecte es pogués dur a terme, ja que com normalment es diu això no és només feina d'un. "En el pla personal m'agradaria agrair a Oriol Riba Grifell, personal de suport a la recerca del Departament ENTEL, per la seva col•laboració, ajuda, suport, i com no, paciència que m'ha demostrat. A més agrair-li, en especial, l'assessorament tècnic que m'ha donat, ja que sense els seus consells el projecte no hagués assolit la magnitud a la qual ha arribat. Igualment agrair al departament d'enginyeria telemàtica de la UPC per permetre'm utilitzar un dels laboratoris de l'EETAC, així com també els seus recursos i materials. Agrair també a tots els meus companys d'universitat, principalment a aquells amb qui he compartit el laboratori del departament durant el transcurs del projecte, des de Robert i Aus, fins a Javier o Álvaro, entre d'altres. Ells també han aportat el seu granet de sorra. I finalment, i no per això en menor mesura, a la meva directora del projecte, Cristina Cervelló, no tan sols per la seva ajuda, sinó també per confiar en mi a l'hora d'oferir-me la possibilitat de realitzar aquest projecte. Gràcies a tots.

A reconfigurable optical add-drop multiplexer as well as a 1x4x4 reconfigurable λ router, designed for use in the second telecom window, are demonstrated. The devices that each have a footprint less than 2 mm 2 are based on thermally tunable vertically coupled microring resonators fabricated in Si 3 N 4 /SiO 2 .

In this paper, we present the design, fabrication, and characterization of two monolithically InP-based integrated electro-optically tunable filters. The combination of these filters can be used to achieve a filter with a narrow passband and a large free spectral range. These filters are designed to be used in an integrated tunable laser source in the 1600-1800 nm wavelength region using active-passive integration technology. The fact that these filters worked successfully shows that this integration technology, originally designed to be used around 1550 nm wavelength, can also be used successfully in the 1600-1800 nm wavelength region without a large penalty in performance. The two filters, a high-resolution arrayed waveguide grating-type filters and a low-resolution multimode interferometer-tree-type filter are made tunable using 5 mm long electro-optic phase modulators in the arms of the waveguide arrays. Measurements show that these filters can be tuned over a wavelength range of more than 100 nm with an accuracy of 0.1 nm (1% of the free spectral range) for the high-resolution filter and an accuracy of 9 nm (4% of the free spectral range) for the low-resolution filter.

In this paper a distributed routing management solution is described that takes into consideration statistical Quality of Service (QoS) information about the state of network links. The goal is to offer dynamic metrics to the routing algorithm based on the current resource utilization, i.e. the routing metrics will depend on the traffic load and the delay measured on individual links in real-time. Identification of congested areas allows situation-aware path selection, enhancing the global capacity of the network by determining optimal routes. Streszczenie. W artykule przedstawiono sposób zarz dzania routowaniem, w którym wzi to pod uwag parameter QoS na temat stanu linków w sieci. G ównym celem by o zastosowanie dynamicznej metryki do algorytmu routowania, opartej na informacji o bie cym wykorzystaniu zasobów. Identyfikacja rejonów przeci enia pozwala na polepszenie dzia ania i pojemno ci sieci poprzez optymalizacj cie ki routowania. (Kontrola przeci enia w routowaniu QoS).

Abstract—This paper presents the design principles and the practical implementation of a routing management solution which takes into account statistical cross-layer Quality of Service information regarding the state of the network. Link monitoring and ...

Fiber-to-Home (FTTH) networks face important challenges with signal pilots, especially over long distances. The purpose of this research is to develop an innovative solution to increase the performance of the FTTH network and reduce signal loss using advanced optical engineering techniques and network design strategies. The research method involves studying the most important factors affecting the signal LOS, including CAR, spreading and no -lines -intervention, followed by optical transmission enhancement technology as optical signal amplifiers (EDFA, Raman Vamlephire), different techniques for the use of spreading, spreading, compensation. The first results indicate that the signal LOS can be significantly reduced to the Raman amplification with advanced modulation forms such as OFDM and continuous signal regeneration with the transmission area. In addition, findings suggest that the use of automated error improvement techniques on high networks can increase the signal stability over long distances. The study conclusion that improvement of network optimization under circumstances for improving the FTTH network requires integration of extended optical hardware, advanced software and artificial intelligence techniques. This research contributes to the development of fiber optic networks to meet high speed and meet the increasing demand for reliable communication.

The Centralized Radio Access Network (C-RAN) provides a valid solution to overcome the problem of traditional RAN in scaling up to the needed processing resource and quality expected in 5G. The Common Public Rate Interface has been defined to transport traffic flows in C-RAN and recently some market solutions are available. Its disadvantage is to increase by at least 10 times the needed bandwidth and for this reason its introduction will be gradual and will coexist with traditional RAN solutions in which Ethernet traffic is carried towards the radio base stations. In this paper, we propose an Xhaul optical network architecture based on Optical Transport Network (OTN) and Dense Wavelength Division Multiplexing (DWDM) technologies. The network allows for a dynamic allocation of the bandwidth resources according to the current traffic demand. The network topology is composed of OTN/DWDM rings and the objective of the paper is to evaluate the best configuration (number of rings and number of wavelengths needed) to both to minimize the cost and to provide an implementable solution. We introduce an analytical model for the evaluation of the number of wavelengths needed in each optical ring and provide some results for 5G case studies. We show how, although the single ring configuration provides the least cost solution due to the high statistical multiplexing advantage, it is not implementable because it needs switching apparatus with a too high number of ports. For this reason, more than one ring is needed and its value depends on several parameters as the offered traffic, the number of Radio Remote Units (RRU), the percentage of business sub-area and so on. Finally, the analytical model allows us to evaluate the advantages of the proposed dynamic resource allocation solution with respect to the static one in which the network is provided with a number of wavelengths determined in the scenario in which the radio station works at full load. The bandwidth saving can be in the order of 90% in a 5G traffic scenario.

Wavelength conversion has been shown as one of the key techniques to improve blocking performance in a wavelength-routed all-optical network. Given that wavelength converters nowadays remain very expensive, how to make effective use of a limited number of wavelength converters becomes an important issue. In this paper, we propose Sparse-Partial Wavelength Conversion (SPWC) network architecture with the inherent flexibility that can facilitate network carriers to migrate the optical backbone to support wavelength conversion. We demonstrate that this network architecture can significantly save the number of wavelength converters, yet achieving excellent blocking performance. Theoretical and simulation results indicate that, the performance of a wavelength-routed WDM network with only 1-5% of wavelength conversion capability is very close to that with Full-Complete Wavelength Conversion capability.

This report is a preprint of a paper intended for presentation at a conference. Because of changes that may be made before formal publication, this preprint is made available with the understanding that it will not be cited or reproduced without the permission of the author. This report is a formal draft or working paper, intended to solicit comments and ideas from a technical peer group.

Free Space Optic (FSO) merupakan sistem komunikasi yang memanfaatkan atmosfer sebagai media propagasi. Dengan itu perlu dilakukan penelitian pengaruh kondisi atmosfer terhadap kualitas dari sistem komunikasi FSO. Penelitian ini melakukan analisa kinerja transmisi FSO di model kanal Kim dan Kruse menggunakan teknik modulasi 16-Quadrature Amplitude Modulation, On-Off-Keying (OOK)-RZ, dan OOK-NRZ di sisi pengirim dan APD photodetector sebagai penerima. Parameter yang diamati yaitu Bit Error Rate (BER) terhadap perubahan visibility 1-6 km, daya 1-5 watt, dan jarak link 1-10 km pada panjang gelombang 850 nm, 1310 nm, dan 1550 nm. Hasil dari simulasi menunjukan bahwa kanal Kim dan Kruse dapat bekerja pada link yang jauh dengan memadukan panjang gelombang dan daya kirim. Perbandingan menunjukan bahwa OOK-RZ memiliki kinerja lebih baik dari 16-QAM dan OOK-RZ sehinngga OOK-RZ dapat menempuh link lebih jauh.

Ferreira e Simão Brandão as minha desculpas por todas as vezes que vos interrompi o raciocínio para vos por as minhas dúvidas, sem o vosso know-how isto não tinha a mesma piada. À Associação Juvenil de Ciência o espaço a que dediquei mais tempo da minha juventude, tempo esse muito bem empregue. A todas as pessoas que lá conheci, que me orientaram e que eu orientei. Em especial ao Gonçalo Pimentel, o meu melhor amigo que eu ainda hoje não consegui perceber completamente e que por isso mantém a mesma piada desde o momento que o conheci. Podia-te agradecer por muita coisa, mas principalmente pelas decisões que tomaste para me proteger e eu não percebi. Para chegar a esta tese, cinco anos de curso ficaram para trás e é sem dúvida que de pessoas se fazem as recordações. Começo por agradecer primeiro a quem me deixou no final da licenciatura Maria Beatriz Ferreira. Escusado será dizer que te agradeço pela ajuda ao longo deste percurso. Quero sim deixar público aqui que muito do que sou hoje academica, pessoal e profissionalmente o devo a ti. Foi um orgulho poder partilhar três anos de estudo e diversão contigo, muitas estórias e muitos sorriso ainda estarão para se desenlaçar.

The combination of Spatial Division Multiplexing (SDM) with flexi-grid WDM enables optical transceivers to provide super-channels exploiting both spectral and spatial dimensions. In this paper we extend the SDM-WDM transceivers to support sliceability for the first time, and make an effective use of spatial and spectral resources. The proposed architecture provides multiple independent spectral-spatial super-channels (i.e., slices) sharing the same transceiver and exploiting different spectrum/core/ mode resources. The proposed architecture also enables to monitor the BER of the provisioned slices in order to detect any signal quality degradation due to the provisioning of additional slices. On the other hand, there is a general trend towards the disaggregation of the optical networks. In this paper we also propose the first open API based on YANG data model and NETCONF protocol for SDN-enabled sliceable SDM-WDM transceivers. The proposed transceiver is experimentally validated in a joint testbed between CTTC and KDDI research.

New paradigms are being proposed to cope with the increasing traffic demand in the access networks. One alternative is to leverage cost-efficient VCSEL-based Sliceable Bandwidth Variable Transceivers (S-BVTs) near the edge. In this work, we investigate the adoption of optical S-BVTs for the transport of cellular traffic. A dynamic and decentralized orchestration algorithm is proposed to achieve an optimal user association and resource allocation of the access network's resources while considering the load-balancing and availability of the underlying optical infrastructure. Two association and resource allocation techniques are explored in a two-tier heterogeneous network featuring different radio access technologies. The results show that the decentralized solution outperforms the coverage mapsbased association and exhibits load balancing capabilities without the need of a centralized coordination, which can be leveraged by the S-BVT's adaptive capabilities.

Medium distance transmission is absolute for the application of high-power signal transmission where multimode fiber (MMF) is a more cost-effective choice over single-mode optical fiber. This study presents an optimized approach that successfully demonstrates a state-of-the-art technology known as multi-level multiplexing, which combines wavelength division multiplexing and mode division multiplexing for a mediumdistance communication scheme over multimode fiber spanning 100km. The system achieved a transmission capacity of 5.4Tbps using 40 WDM channels while preserving signal quality and optimal power levels in the output. The goal is to demonstrate a new strategy that can considerably improve transmission capacity while maintaining signal quality. Bit error rate, Q factor, and eye diagram are discussed for concluding and comparing the transmission quality.

We report the fabrication of widely tunable ridge waveguide distributed Bragg reflector (DBR) lasers with InGaAsP butt-joint as grating material. The shape of the butt-joint interface is found to have significant effect on the properties of the lasers. It is shown that irregular mode jumps during wavelength tuning can be avoided by a V-shaped butt-joint interface. From the fabricated device, 23 channels with 0.8 nm spacing and greater than 35 dB side mode suppression ratios are obtained. The different tuning characteristics of the ridge waveguide and the previously reported buried ridge stripe DBR lasers are discussed. Combined with the wide tuning range and the simple structure, the ridge waveguide DBR lasers are promising for use in wavelength division multiplexing passive optical networks (WDM-PONs).

In this work, we have demonstrated using a pair of in-fiber Fabry-Perot interferometer (FPI) with matched Bragg wavelength and free spectral range (FSR) for elastic wave detection based on matched filter interrogation configuration. The cavity lengths of the FPI structures are deliberately made long to achieve small FSR to enhance their sensitivity to elastic wave pressure. It is found that the sensitivity of sensor to elastic wave pressure is linearly proportional to the FPI cavity length. This finding is in agreement with the theoretical analysis.

We propose a new design scheme of resilient Wavelength Division Multiplexing (WDM) networks by extending and reshaping pre-configured protection tree (p-tree) structures. The resulting protection scheme relies on optimized pre-cross connected structures that span all previously proposed protection patterns. p-Tree-based protection schemes offer the advantages of scalability, local restoration capabilities, and failure impact restriction, but at the same time suffers from capacity inefficiency. While keeping these advantages, we propose an extension (reshaping) of the p-tree protection pattern that imposes no restriction on the shapes of the protection building blocks. Not only the resulting protection scheme remains scalable and highly flexible, but it also leads to pre-configured protection structures that improve much further on capacity efficiency and recovery delay. We establish some new integer linear programming models, and use large scale optimization tools, namely column generation (CG) to solve them. Our CG-based solution method is highly scalable as it does not require an a priori explicit enumeration of the protection structures, but an efficient dynamic enumeration of only the most promising ones. Comparison are made with three other protection schemes, i.e, simple and non-simple p-cycles (fully pre-cross connected structures) as well as p-trees. Results show a clear advantage of the proposed extended-tree scheme with respect to flexibility, capacity efficiency, and restoration delay.

We propose a new design scheme of resilient Wavelength Division Multiplexing (WDM) networks by extending and reshaping pre-configured protection tree (p-tree) structures. The resulting protection scheme relies on optimized pre-cross connected structures that span all previously proposed protection patterns. p-Tree-based protection schemes offer the advantages of scalability, local restoration capabilities, and failure impact restriction, but at the same time suffers from capacity inefficiency. While keeping these advantages, we propose an extension (reshaping) of the p-tree protection pattern that imposes no restriction on the shapes of the protection building blocks. Not only the resulting protection scheme remains scalable and highly flexible, but it also leads to pre-configured protection structures that improve much further on capacity efficiency and recovery delay. We establish some new integer linear programming models, and use large scale optimization tools, namely column gen...

Four-wave mixing (FWM) in silicon waveguides is considered to be a promising effect to realize the wavelength conversion function for wavelength-division-multiplexing optical communication systems. Compared to the degenerate FWM with a single pump, the nondegenerate FWM with two pumps shows more flexibility in phase-matching condition and has more opportunities to acquire broader conversion bandwidth. The bandwidth enhancement is theoretically analyzed for the two-pump FWM and an enhancement of 25% is experimentally demonstrated. Also, an ultra-broadband wavelength conversion is presented based on two-pump FWM by fixing one pump near the signal and scanning the other pumps.

This paper studies the physical layer's impact on the blocking probability and energy consumption of wide-area dynamic elastic optical networks (EONs). For this purpose, we consider five network configurations, each named with a network configuration identifier (NCI) from 1 to 5, for which the Routing, Modulation Level, and Spectrum Assignment (RMLSA) problem is solved. NCI 1-4 are transparent configurations based on all-EDFA, hybrid Raman/EDFA amplifiers (with different Raman gain ratio R ), all-DFRA, and alternating span configuration (EDFA and DFRA). NCI 5 is a translucent configuration based on all-EDFA and 3R regenerators. We model the physical layer for every network configuration to determine the maximum achievable reach of optical signals. Employing simulation, we calculate the blocking probability and the energy consumption of the different network configurations. In terms of blocking, our results show that NCI 2 and 3 offer the lowest blocking probability, with at least 1 and 3 orders of magnitude of difference with respect to NCI 1 and 5 at high and low traffic loads, respectively. In terms of energy consumption, the best performing alternatives are the ones with the worst blocking (NCI 1), while NCI 3 exhibits the highest energy consumption with NCI 2 R = 0.75 following closely. This situation highlights a clear trade-off between blocking performance and energy cost that must be considered when designing a dynamic EON. Thus, we identify NCI 2 using R = 0.25 as a promising alternative to reduce the blocking probability significantly in wide-area dynamic EONs without a prohibitive increase in energy consumption. INDEX TERMS Elastic optical networks, resource assignment, translucent configuration, transparent configuration.

We present a heuristic method to optimize the capacity of a WDM mesh network assigning working and protection capacity to a set of static optical-connection requests under the linkdisjoint constraint. The method can be applied to networks supporting either dedicated or shared path-protection. Routing and fiber and wavelength assignment (RFWA) are jointly performed for all the lightpaths with the aim of minimizing the number of fibers in the network. The employment of multiple prioritized heuristic criteria and an efficient link disjoint paths search algorithm are proposed. With less computational effort, the proposed heuristic approach allows to obtain good suboptimal results compared to the exact integer-linear-programming optimization. After introducing our design approach, we discuss the optimization of particular case-study networks under various condition and compare the results.

In this paper a new solution for the routing, fiber, wavelength and time slot assignment problern (RFWTA) is proposed for a static WDM network. A set of electronic requests characterized by different bit-rates are groomed on lightpaths by a TDM-scheme, designing the logical topology so that the lightpath bandwidth is efficiently exploited. An efficient TDM-based mapping of low granularity electronic connection requests achieves savings in fiber deployment to accommodate a given static traffic. Our analysis comprises two different network layers. First, all the electronic requests are mapped on the logical topology and groomed to obtain the set of lightpath connection requests. Secondly, such requests are routed and fibers and wavelengths are jointly assigned. We adopt the concept of Multihop Lightpath to constrain the number of Time Slot Switching (TSS) operations for each connection request. After introducing our design approach, we discuss the optimization of two case-study networks under various conditions and we analyze the results.

Failure-protection ofWavelength Division Multiplexing networks is a hot researchtopic today. In this paper we focus on optical path protection in multifiber mesh networks. We present a heuristic method to assign working and protection capacity to a set of static optical-connection requests under the path-disjoint constraint. Routing, fiber and wavelength assignment are jointly perfmmed for all the lightpaths with the aim of minimizing the number of fibers in the network The proposed heuristic approach allows to obtain good suboptimal results compared to the exact integer-linear-programming optimization. We discuss the optimization of particular case .. study networks in order to analyze the influence of different link-disjoint-path search algorithms on the final results and of various design critelia.

Efficient planning and optimization of wavelength division multiplexing networks is an important issue today. Integer Linear Programming (ILP) is the most used exact method to perform this task. In this paper we propose a new ILP formulation that allows to solve optimization with less computational effort compared to other ILP approaches. This formulation applies to multifiber mesh networks with or without wavelength conversion, when either the total fiber number or the total fiber length is the cost function to be minimized. After presenting the formulation we discuss the results we obtained by exploiting it in the optimization of two case-study networks. O PTICAL networks based on Wavelength Division Mul- tiplexing (WDM) are the main characters today of the transport infrastructure evolution towards high capacity and high reliability. They are being deployed at an extremely rapid rate for wide-area transport applications as well as in the metro and regional areas. These networks, based on switching and routing of optical circuits in space and wavelength switching domains, exploit the most advanced photonic technology that is available on the market and are therefore evolving with a similar fast pace as WDM transmission and switching equipment. Recently, on the switching equipment side, Optical Cross Connects (OXC) systems have become available, beside the more mature Optical Add-Drop Multiplexers. This opened up the road to the possibility of deploying complex WDM networks based on the mesh topology, while in the past single ring or overlaid multi-ring were the most used architectures for WDM. The increase in WDM complexity brought the need for suitable network planning strategies into foreground. Problems such as optimal dimensioning routing and resource allocation for optical connections must be continuously solved by new and old operators, to plan new installations or to update and expand the existing ones. These problems can no longer be manually solved in complex network architectures, as it usually happened in the earlier experimental WDM installations. Computer-aided planning tools and procedures are needed for the future which can achieve an efficient utilization of network resources in a reasonable computational time. Research on optical network since some years ago has been investigating design and optimization techniques in order to provide operators the most efficient and flexible procedures to solve the network design problem. The various proposed solutions can be classified into two main groups: heuristic methods M. Tornatore and G. Maier are with CoreCom,