Showing papers on "Wavelength-division multiplexing published in 2020"

Lightwave Technology: Telecommunication Systems

Abstract: Preface. 1. Introduction. 2. Optical Signal Generation. 3. Signal Propagation in Fibers. 4. Nonlinear Impairments. 5. Signal Recovery and Noise. 6. Optical Amplifier Noise. 7. Dispersion Management. 8. Nonlinearity Management. 9. WDM Systems. 10. Optical Networks. Appendix A: System of Units. Appendix B: Software Package. Appendix C: Acronyms. Index.

Assessment on the Achievable Throughput of Multi-Band ITU-T G.652.D Fiber Transmission Systems

Abstract: Fiber-optic multi-band transmission (MBT) aims at exploiting the low-loss spectral windows of single-mode fibers (SMFs) for data transport, expanding by $\sim\!11\times$ the available bandwidth of C-band line systems and by $\sim\!5\times$ C+L-band line systems’. MBT offers a high potential for cost-efficient throughput upgrades of optical networks, even in absence of available dark-fibers, as it utilizes more efficiently the existing infrastructures. This represents the main advantage compared to approaches such as multi-mode/-core fibers or spatial division multiplexing. Furthermore, the industrial trend is clear: the first commercial C $+$ L-band systems are entering the market and research has moved toward the neighboring S-band. This article discusses the potential and challenges of MBT covering the ITU-T optical bands O $\rightarrow$ L. MBT performance is assessed by addressing the generalized SNR (GSNR) including both the linear and non-linear fiber propagation effects. Non-linear fiber propagation is taken into account by computing the generated non-linear interference by using the generalized Gaussian-noise (GGN) model, which takes into account the interaction of non-linear fiber propagation with stimulated Raman scattering (SRS), and in general considers wavelength-dependent fiber parameters. For linear effects, we hypothesize typical components’ figures and discussion on components’ limitations, such as transceivers,’ amplifiers’ and filters’ are not part of this work. We focus on assessing the transmission throughput that is realistic to achieve by using feasible multi-band components without specific optimizations and implementation discussion. So, results are meant to address the potential throughput scaling by turning-on excess fiber transmission bands. As transmission fiber, we focus exclusively on the ITU-T G.652.D, since it is the most widely deployed fiber type worldwide and the mostly suitable to multi-band transmission, thanks to its ultra-wide low-loss single-mode high-dispersion spectral region. Similar analyses could be carried out for other single-mode fiber types. We estimate a total single-fiber throughput of 450 Tb/s over a distance of 50 km and 220 Tb/s over regional distances of 600 km: $\sim\!10\times$ and 8× more than C-band transmission respectively and $\sim\!2.5\times$ more than full C+L.

GNPy: an open source application for physical layer aware open optical networks

Abstract: In this paper, we describe the validation of GNPy. GNPy is an open source application that approaches the optical layer according to a disaggregated paradigm, and its core engine is a quality-of-transmission estimator for coherent wavelength division multiplexed optical networks. This software is versatile. It can be used to prepare a request for proposal/request for quotation, as an engine of a what-if analysis on the physical layer, to optimize the network configuration to maximize the channel capacity, and to investigate the capacity and performance of a deployed network. We validate GNPy by feeding it with data from the network controller and comparing the results to experimental measurements on mixed-fiber, Raman-amplified, multivendor scenarios over the full C-band. We then test transmission distances from 400 up to 4000 km, polarization-multiplexed (PM) quadrature phase shift keying, the PM-8 quadrature amplitude modulation (QAM) and PM-16QAM formats, erbium-doped fiber amplifier (EDFA) and mixed Raman–EDFA amplification, and different power levels. We show excellent accuracy in predicting both the optical signal-to-noise ratio and the generalized signal-to-noise ratio (GSNR), within 1 dB accuracy for more than 90% of the 500 experimental samples. We also demonstrate the ability to estimate the transmitted power maximizing the GSNR within 0.5 dB of accuracy.

Mode-division multiplexed transmission of wavelength-division multiplexing signals over a 100-km single-span orbital angular momentum fiber

Abstract: We experimentally demonstrate mode-division multiplexed (MDM) transmission using eight orbital angular momentum (OAM) modes over a single span of 100-km low-attenuation and low-crosstalk ring-core fiber (RCF). Each OAM mode channel carries 10 wavelength-division multiplexing (WDM) signal channels in the C band, with each WDM channel in turn transmitting 16-GBaud quadrature phase-shift keying signal. An aggregate capacity of 2.56 Tbit/s and an overall spectral efficiency of 10.24 bit/(s · Hz) are realized. The capacity-distance product of 256 (Tbit/s) · km is the largest reported so far for OAM fiber communications systems to the best of our knowledge. Exploiting the low crosstalk between the OAM mode groups in the RCF, the scheme only requires the use of modular 4×4 multiple-input multiple-output processing, and it can therefore be scaled up in the number of MDM channels without increasing the complexity of signal processing.

10.66 Peta-Bit/s Transmission over a 38-Core-Three-Mode Fiber

Abstract: We demonstrate transmission of 368-WDM-38-core-3-mode × 24.5-GBaud 64- and 256-QAM signals over 13 km. Record data-rate and spectral-efficiency of 1158.7 b/s/Hz were enabled by a low DMD 38-core-3-mode fiber with high uniformity amongst cores.

Wavelength division multiplexing techniques based on multi transceiver in low earth orbit intersatellite systems

Abstract: System performance, which depends on the data transmission rates and propagation distances between two satellites in low Earth orbit (LEO) based on wavelength division multiplexing (WDM) techniques, is thoroughly studied. This study demonstrates the effect of WDM techniques on multi transceiver inter-satellite wireless optical communications. The system performance parameters with propagation distance at a multiple transceiver system are discussed using two previous models. The system performance parameters are investigated with 250 Gb/s transmission bit rates and 5000 km propagation distances for 16 transceiver systems. The maximum quality factor (Q factor), light peak signal per noise ratio, and signal peak per noise ratio are the primary important performance parameters in this study.

Influence of dense wavelength division multiplexing (DWDM) technique on the low earth orbit intersatellite systems performance

Abstract: This work discusses the effect of wavelength division multiplexing on performance of intersatellite link. Intersatellite optical wireless communication (IsOWC) system is simulated by using OptiSystem software. Number of multiplexing channels involve on system performance. Bit rate is an operating parameter that determines the quality of the signal. Also, wavelength and distance between satellite transmitter and satellite receiver determine the system performance. In this article, the max Q factor, received power, and optical signal/noise ratio are the major leading performance parameters.

Linear and Nonlinear Frequency-Division Multiplexing

Abstract: Two signal multiplexing schemes for optical fiber communication are considered: Wavelength-division multiplexing (WDM) and nonlinear frequency-division multiplexing (NFDM), based on the nonlinear Fourier transform. Achievable information rates (AIRs) of NFDM and WDM are compared in a network scenario with an ideal lossless model of the optical fiber in the defocusing regime. It is shown that the NFDM AIR is greater than the WDM AIR subject to a bandwidth and average power constraint, in a representative system with one symbol per user. The improvement results from nonlinear signal multiplexing.

A WDM PAM4 FSO–UWOC Integrated System With a Channel Capacity of 100 Gb/s

Abstract: A wavelength-division-multiplexing (WDM) four-level pulse amplitude modulation (PAM4) free-space optical (FSO)–underwater wireless optical communication (UWOC) integrated system with a channel capacity of 100 Gb/s is proposed and attainably demonstrated. Analytic results reveal that 1.8-GHz 405-nm blue-violet-light and 1.7-GHz 450-nm blue-light laser diodes (LDs) with two-stage light injection and optoelectronic feedback techniques are competently adopted for 100 Gb/s PAM4 signal transmission through a 500-m free-space transmission with 5-m clear ocean underwater link. Combining dual-wavelength WDM scenario with PAM4 modulation, the channel capacity of FSO–UWOC integrated systems is significantly enhanced with an aggregate transmission rate of 100 Gb/s (25 Gbaud PAM4/wavelength × 2 wavelengths). With doublet lenses in FSO, laser beam reducer and transmissive spatial light modulator in UWOC, a sufficiently low bit error rate of 10−9 and acceptable PAM4 eye diagrams are acquired. This demonstrated 100 Gb/s PAM4 FSO–UWOC integrated system with a WDM scenario is advantageous for the enhancement of a high-speed optical wireless link with long-reach transmission.

Advanced optical access technologies for next-generation (5G) mobile networks [Invited]

Abstract: Fixed optical transport is the predominant fronthaul technology for 4G mobile access networks, carrying the traffic between the central office and subtended antenna sites. With the new functional splits and related standards introduced in 5G, new capacity and quality-of-service requirements are imposed on optical transport. In this paper, we discuss low-cost high-capacity optical fronthaul solutions enabled by advanced modulation formats and wavelength-agnostic passive wavelength division multiplexing (WDM) technology. As the key component, a low-cost remotely tunable WDM transceiver is introduced, specifically designed on a hybrid InP-polymer platform. We also explain why an Ethernet-based 5G fronthaul solution requires additional means to improve the latency and timing performance of the conventional packet forwarding and multiplexing. We review the recent standardization effort on time-sensitive networking in support of 5G fronthaul and present an FPGA-based implementation providing low latency and low packet delay variation following the latest IEEE 802.1CM specification. These advanced technologies can facilitate an effective packet-optical transport for 5G.

Performance evaluation and enhancement of the modified OOK based IM/DD techniques for hybrid fiber/FSO communication over WDM-PON systems

Abstract: In this paper, we have studied the performance evaluation and enhancement of a wavelength-division-multiplexing (WDM) for the passive optical network (PON) in the hybrid fiber/free-space optical (HFFSO) communication system using the modified on–off keying (OOK) based intensity modulation and direct detection (IM/DD) techniques. This work describes the design and analysis of the 8-channels WDM based on the PON-HFFSO transmission system at 2.5 Gbps under different atmospheric turbulence (AT) conditions. Inter-channel crosstalk (ICC), fluctuation, amplified spontaneous emission noise, AT, and impairments are investigated in the paper. A hybrid fiber/WDM-FSO over the PON structure using IM/DD and OOK significantly improves reliability link and accessibility as well as data rate, also improves the system capacity; hence the proposed model will reduce power consumption while maintaining system efficiency. Both impairments and ICC are investigated here and the results are presented in the form of bit-error-rate (BER), transmission distances, the required optical power, and electrical signal-to-noise ratios (SNRs). The system uses the modified OOK based on IM/DD to implement adaptive and electrical SNRs detection thresholds. Numerical results show that the SNR gap between the electrical-SNR-optimized detection system and adaptive detection system is 2.2 dB and 4.2 dB at a BER of 10−5 without a state offset ξ = 0 and ξ = 0.21, respectively. The proposed model enhances performance in terms of BER and electrical SNRs. An improvement in the power penalty of 2.0–4.0 dB at a BER of 10−12 can be potentially achieved using the modified OOK technique when impaired by the weak turbulence.

Software-Defined WDM Optical Transport in Disaggregated Open Optical Networks

Abstract: Transparent optical networks operated by WDM coherent optical technologies for data transport are moving-on towards the implementation of the openness paradigm. In such a context, disaggregated network elements and subsystems can be abstracted to manage and control propagation of WDM optical data transport. It enables the application of the software-defined paradigm down to the physical layer, with optical transport fully summarized by a quality of transmission estimator.

A Study on the Effect of Ultra-Wide Band WDM on Optical Transmission Systems

Abstract: In the optical communication, ultra-wide band (UWB) wavelength division multiplexing (WDM) transmission systems have been gathering considerable attention because it is becoming rapidly difficult to increase capacity per optical fiber within conventional limited bandwidths. Our aim is to extend the wavelength for UWB WDM systems from the widely used C or L bands to additional bands such as the S, E, and O bands. For these wavelengths to be used in a practical manner, it is necessary to study how repeater configurations such as multiplexer and optical amplifiers and inter-channel interference caused by stimulated Raman scattering (SRS) will impact optical transmission systems. We study these problems through two UWB WDM experiments. In the first, we demonstrate the first ever 5-band WDM transmission and devise a format for allocating wavelength adaptive modulation to exhaustively use wavelength dependent optical signal-to-noise ratio (OSNR). The experiment setup includes 5 channel signals each allocated in each band and 5-band WDM repeater constructed of WDM coupler, 3-dB couplers, and four type of optical amplifiers. In the second, we investigate the inter-channel interference effect from SRS between 35-channel S- and 40-channel L-band 16QAM signal transmission over 210 km. The experimental results show that there is only optical power transition between S and L bands and that no nonlinear crosstalk interference is observed.

Multiwavelength membrane laser array using selective area growth on directly bonded InP on SiO2/Si

Abstract: The cost and power consumption of optical transmitters are now hampering further increases in total transmission capacity within and between data centers Photonic integrated circuits (PICs) based on silicon (Si) photonics with wavelength-division multiplexing (WDM) technologies are promising solutions However, due to the inefficient light emission characteristics of Si, incorporating III-V compound semiconductor lasers into PICs via a heterogeneous integration scheme is desirable In addition, optimizing the bandgap of the III-V material used for each laser in a WDM transmitter becomes important because of recent strict requirements for optical transmitters in terms of data speed and operating temperature Given these circumstances, applying a direct-bonding scheme is very difficult because it requires multiple bonding steps to bond different-bandgap III-V materials that are individually grown on different wafers Here, to achieve wideband WDM operation with a single wafer, we employ a selective area growth technique that allows us to control the bandgap of multi-quantum wells (MQWs) on a thin InP layer directly bonded to silicon (InP-on-insulator) The InP-on-insulator platform allows for epitaxial growth without the fundamental difficulties associated with lattice mismatch or antiphase boundaries High crystal quality is achieved by keeping the total III-V layer thickness less than the critical thickness (430 nm) and compensating for the thermally induced strain in the MQWs By carrying out one selective MQW growth, we successfully fabricated an eight-channel directly modulated membrane laser array with lasing wavelengths ranging from 12723 to 13105 nm The fabricated lasers were directly modulated at 56-Gbit/s with pulse amplitude modulation with four-amplitude-level signal This heterogeneous integration approach paves the way to establishing III-V/Si WDM-PICs for future data-center networks

Enabling Techniques for Optical Wireless Communication Systems

Abstract: We summarized the recent progress of enabling techniques for the optical wireless communication (OWC) and visible light communication (VLC). Besides, we reported two high data-rate laser-diode (LD) based VLC systems. Several application scenarios using VLC were also discussed.

Performance analysis of high speed backward compatible TWDM-PON with hybrid WDM–OCDMA PON using different OCDMA codes

Abstract: In this paper, a backward compatible bidirectional 160/40 Gbps time and wavelength division multiplexing-passive optical network with hybrid wavelength division multiplexing optical code division multiple access PON (WDM–OCDMA PON) has been proposed. Six OCDMA codes have been used to enhance the security and users’ ability to access shared bandwidth of an optical network. In this “pay-as-you-grow” supported system, the fiber impairment effects have been effectively reduced. The performance of the proposed system has been analyzed for variable input power (4–19 dBm) and transmission distance (10–70 km) supporting 120 active users under the influence of fiber nonlinearities, attenuation, dispersion and noise. Based on the numerical calculations, the proposed system using modified quadratic congruence (MQC) code is shown to provide better performance compared to multi diagonal, hadamard, zero cross-correlation (ZCC), shift ZCC and flexible cross-correlation codes. To validate the numerical analysis, the simulation of the proposed system at 160/40 Gbps data rate for 70 km downstream and greater than 70 km upstream fiber link transmission at 10−9 BER limit for 68 active users have been successfully demonstrated. Also, it has been shown that MQC code provides optimum results at 10 dBm input power over 55 km distance and supports more than 120 active users with high gain of − 1.97 dB and low noise figure of 2 dB. Further, the comparative performance of the proposed system with the previous latest works in literature reveals a superior performance of the system.

An enhanced WDM optical communication system using a cascaded fiber Bragg grating

Abstract: In this paper, a cascaded fiber Bragg grating (FBG) system is proposed to reduce the dispersion in the optical signal in single mode optical fibers. This consequently enhances the system performance, which is evaluated by the bit error rate (BER) and quality factor (Q-factor). The proposed model consists of four uniform cascaded FBGs connected at the transmitter to get narrow linewidth, Δλ, of the optical signal, which is a major cause of the delay. The Optisystem7 is used to simulate the proposed model in a WDM system with and without the model for distance 200 km. The system parameters are investigated showing an enhanced performance with 12%, including eye diagram, Q-factor and BER. A 10−6–10−10 BER is achieved with a quality factor in the range 7–14, including the effects of fiber length, input power and FBG length.

Control and Calibration Recipes for Photonic Integrated Circuits

Abstract: This article presents the key ingredients and the best practices for implementing simple, effective and robust control and calibration procedures for arbitrary photonic integrated circuit (PIC) architectures. Three main features are presented and discussed: a technique to cancel out the effects of mutual crosstalk among thermal tuners, the exploitation of labelling to identify different optical signals, the use of input modulated signal to automatically reshape the frequency response of the device. Examples of application are then illustrated to show the validity and generality of the approach, namely a cross-bar interconnect matrix router, a variable bandwidth filter and third order coupled microring filter. Further, the automatic and dynamic generation of the lookup table of add/drop hitless filters operating on a dense wavelength division multiplexing grid is demonstrated. The lookup table achieved with the proposed approach can dynamically update itself to new conditions of the chip or new requirements of operation, such as variations in channel modulation format or perturbation induced by neighboring devices due to a change in their working point.

Performance of chip-scale optical frequency comb generators in coherent WDM communications.

Abstract: Optical frequency combs have the potential to become key building blocks of wavelength-division multiplexing (WDM) communication systems. The strictly equidistant narrow-band spectral lines of a frequency comb can serve either as carriers for parallel WDM transmission or as local-oscillator (LO) tones for parallel coherent reception. When it comes to highly scalable WDM transceivers with compact form factor, chip-sale comb sources are of particular interest, and recent experiments have demonstrated the viability of such devices for high-speed communications with line rates of tens of Tbit/s. However, the output power of chip-scale comb sources is generally lower than that of their conventional discrete-element counterparts, thus requiring additional amplifiers and impairing the optical signal-to-noise ratio (OSNR). In this paper, we investigate the influence of the power and optical carrier-to-noise ratio (OCNR) of the comb lines on the performance of the WDM link. We identify two distinctively different regimes, where the transmission performance is either limited by the comb source or by the link and the associated in-line amplifiers. We further investigate the impact of line-to-line power variations on the achievable OSNR and link capacity using a soliton Kerr frequency comb as a particularly interesting example. We believe that our findings will help to compare different comb generator types and to benchmark them with respect to the achievable transmission performance.

Using machine learning in an open optical line system controller

Abstract: The reduction of system margin in open optical line systems (OLSs) requires the capability to predict the quality of transmission (QoT) within them. This quantity is given by the generalized signal-to-noise ratio (GSNR), including both the effects of amplified spontaneous emission (ASE) noise and nonlinear interference accumulation. Among these, estimating the ASE noise is the most challenging task due to the spectrally resolved working point of the erbium-doped fiber amplifiers (EDFAs), which depend on the spectral load, given the overall gain profile. An accurate GSNR estimation enables control of the power optimization and the possibility to automatically deploy lightpaths with a minimum margin in a reliable manner. We suppose an agnostic operation of the OLS, meaning that the EDFAs are operated as black boxes and rely only on telemetry data from the optical channel monitor at the end of the OLS. We acquire an experimental data set from an OLS made of 11 EDFAs and show that, without any knowledge of the system characteristics, an average extra margin of 2.28 dB is necessary to maintain a conservative threshold of QoT. Following this, we applied deep neural network machine-learning techniques, demonstrating a reduction in the needed margin average down to 0.15 dB.

CAPEX Savings Enabled by Point-to-Multipoint Coherent Pluggable Optics Using Digital Subcarrier Multiplexing in Metro Aggregation Networks

Abstract: Acknowledging the predominantly hubbed traffic profile in the metro, we apply digital subcarrier multiplexing techniques to 400Gb/s coherent pluggable optics, enabling a point-to-multipoint architecture which shows TCO savings of 76% over a five-year period compared to a traditional architecture based on ROADMs and point-to-point transponder

Wavelength Division Multiplexing of 194 Continuous Variable Quantum Key Distribution Channels

Abstract: We demonstrate the first continuous variable quantum key distribution (CV-QKD) system with fully digital phase and polarization tracking, enabling the first wavelength division multiplexing experiment for CV-QKD. We transmit 194 × 0.5 GHz channels with 25 GHz channel spacing, demonstrating an aggregate estimated asymptotic secret key rate of 172.6 Mbit/s over 25 km.

Low-noise high-order Raman fiber laser pumped by random lasing.

Abstract: Raman fiber lasers (RFLs) have been widely utilized in long-haul optical transmission systems as pump sources for distributed Raman amplification (DRA) to increase transmission distance and capacity. However, RFLs with relatively large temporal intensity fluctuations would deteriorate signal quality due to the transfer of relative intensity noise (RIN). In this Letter, a low-noise high-order RFL common cavity pumped by an ytterbium-doped random fiber laser (YRFL) is proposed and demonstrated for the first time, to the best of our knowledge. Stable 4th-order random Raman lasing operating at 1365 nm is generated with 8.9 W of output power, without use of a multi-stage master oscillation power amplification system. Thanks to the YRFL common-cavity pumping where a wavelength division multiplexer (WDM)-assisted fiber-loop mirror is used to generate stable 1090 nm ytterbium-doped random lasing and cascaded random Raman lasing simultaneously, the RIN of the 1365 nm RFL is suppressed as low as -120dB/Hz without any peak over a 0-100 MHz span. Furthermore, the output power and lasing wavelength of this RFL can be flexibly tuned by adjusting the laser diode pump power, high-reflectivity fiber Bragg grating center wavelength, and single-mode fiber length. Hence, such a low-noise high-order RFL paves a way for the development of novel tunable RFLs with stable temporal output, leading to potential replacement of conventional RFLs for DRA in long-haul optical transmission systems to achieve better performances.

Four-Channel CWDM (de)Multiplexers Using Cascaded Multimode Waveguide Gratings

Abstract: A silicon-based four-channel coarse wavelength- division multiplexing (CWDM) (de)multiplexer working in the O-band is proposed and realized. The present on-chip four-channel CWDM (de)multiplexer is composed of four cascaded optical filters with flat-top spectral responses, which are realized by combining a multimode waveguide grating (MWG) and a two-channel mode (de)multiplexer. For the realized flat-top CWDM (de)multiplexer with a ~18-nm channel-spacing, the measured 1-dB bandwidth is as large as 15 nm, which is ~75% of the channel spacing. The thermal sensitivity is also reduced from ~85 pm/°C to 46 pm/°C by introducing the compensation provided by an SU-8 upper-cladding with a negative thermo-optic coefficient.

56-m/3.31-Gbps underwater wireless optical communication employing Nyquist single carrier frequency domain equalization with noise prediction.

Abstract: We propose and experimentally demonstrate an underwater wireless optical communication (UWOC) system using a 520-nm laser diode (LD) and 32-quadrature amplitude modulation (32-QAM) single carrier signals. To mitigate the inter-symbol interference (ISI), a frequency domain equalizer combined with a time-domain decision feedback noise predictor is employed at the receiver. However, this structure cannot apply channel coding conjunctively. Therefore, an interleaver/deinterleaver pair is applied to handle the decoding delay, and thus systematic Reed-Solomon (RS) code can provide reliable feedback signals. With a 3-dB bandwidth of 200 MHz, the proposed system with the frequency domain equalization and noise prediction (FDE-NP) scheme can achieve a maximal net data rate of 3.48 Gbps, which is 17.2% higher than that of orthogonal frequency division multiplexing (OFDM) scheme. At a net data rate of 3.31 Gbps, we have successfully achieved a transmission distance up to 56 m. To the best of our knowledge, this is the first time to employ FDE-NP in UWOC where OFDM conventionally plays a prevailing role for high-speed transmission.

Modeling and mitigation of fiber nonlinearity in wideband optical signal transmission [Invited]

Abstract: The adoption of open optical networks (OONs) requires the development of open and effective network planning tools, enabling the use of multi-vendor or white-box transport solutions. Such tools for studying and planning optical networks must be able to take into account the physical layer impairments, including fiber nonlinearity. The use of wideband wavelength division multiplexing in OONs, with channel frequencies extending across the short, conventional, and long bands and beyond, offers a pathway to increasing data rates through the installed fiber infrastructure. However, achievable information rates are limited by the resulting signal distortion due to fiber nonlinearity as signal bandwidths are increased, in particular, inter-channel stimulated Raman scattering (ISRS). In this paper, we describe the nonlinear effects observed in wideband transmission systems, and review recently developed analytical tools, based on the Gaussian noise (GN) model of nonlinear interference with the inclusion of ISRS. Using the ISRS GN model, we assess the impact of fiber nonlinearity on the achievable information rates in transmission systems with bandwidths of up to 12 THz. We demonstrate the use of the model in the optimization of launch power spectral profiles for a variety of dynamic gain equalizer arrangements in a 1000 km standard single-mode fiber link, using particle swarm optimization and the steepest descent algorithm. Such nonlinear models and optimization methods could be applied in OON planning tools, for example, in optical link emulators to estimate quality-of-transmission and data throughput, and in impairment-aware software-defined network control and management.

Band-Division vs. Space-Division Multiplexing: A Network Performance Statistical Assessment

Abstract: We compare the networking merit of two possible multiplexing techniques on top of wavelength division multiplexing to enlarge transmission capacity: the band division multiplexing (BDM) that aims at using up to all the U-to-O low-loss transmission bands available on the G–652.D fiber and the spatial division multiplexing (SDM) implemented by activating additional fibers, used on the C-band only. We use the statistical network assessmemnt process (SNAP) to derive the networking performance as blocking probability vs. the total allocated traffic normalized with respect to the multiplexing cardinality. We analyze two network topologies: the German regional network and the US-NET continental network. In case dark fibers are available, SDM upgrades are always the best solution, enabling up to 12% and 17% of extra traffic at blocking probability equal to $10^{-3}$ on top of the multiplication by the multiplexing cardinality ( $N_{\text{M}}$ ) of 12, for the German and US-NET topology, respectively. BDM solutions present worse performance, but mixed BDM/SDM solutions display quite limited penalties with respect to the pure SDM solution, up to the use of 16 THz per fiber. So, mixed BDM/SDM implementation seems the most convenient solution in case of limited availability of dark fibers. Pure BDM solutions occupying a bandwidth larger than 16 THz display an increasingly and considerable gap in the allocated traffic with respect to the pure BDM, therefore, their use must be considered only in case of total absence of available dark fibers.