Optical Dense Wavelength Division Multiplexing Research Articles

Optical label-based cost-effective DWDM optical network performance monitoring using low-bandwidth PD with novel SRS mitigation DSP

Large-scale dense wavelength division multiplexing (DWDM) multi-channel performance monitoring is one of the indispensable technologies for the flexible optical networks. The existing Labelbased monitoring scheme requires expensive optical demultiplexing components/equipment to avoid the influence of stimulated Raman scattering (SRS), which is not only costly and bulky, but also could not monitor the wavelength channels simultaneously. In this paper, a low-cost, high-accuracy monitoring scheme based on Optical Label Method is proposed for DWDM networks, where the optical channel power and node identification (ID), as the main monitoring targets that both can indicate or evaluate the channel connection status, could be efficiently monitored. In the scheme, a novel digital signal processing (DSP) method of SRS mitigation is proposed and demonstrated, and an asynchronous code-division multiple access (A-CDMA) based digital label encoding and decoding method is adopted to distinguish the node ID so that channel initial added node can be accurately verified, thereby wavelength connection status can be reliably monitored by combining the channel power and node ID information. The simulation results show that each wavelength channel power and node ID can be accurately monitored only by low bandwidth photoelectric detector (PD) under the condition of 80 wavelengths and 10 spans at C-band.

Performance analysis and selection of wavelength channels based on the FWM effect influence in optical DWDM systems

A deployment of the Dense Wavelength Division Multiplexing (DWDM) in long-haul and metropolitan networks is becoming a reality, its extensive operation is also expected in future next-generation passive optical networks in a short time. This paper is focused on the DWDM technique and its effective utilization in real optical systems and networks. Within this context, an attention is paid to the Four Wave Mixing (FWM) effect that presents the most prominent nonlinearity that can limit the available transmission capacity in the given optical DWDM system. A realized simulation model of the 15-channel DWDM system that can exactly analyze the FWM influence on transmitted wavelength channels in the optical transmission path is presented. Based on executed performance analyses of the FWM influence, possibilities for selection of wavelength channels suitable for practical utilization in the DWDM communication system are introduced.

1.71 Tb/s Single-Channel and 56.51 Tb/s DWDM Transmission Over 96.5 km Field-Deployed SSMF

We report an industry leading optical dense wavelength division multiplexing (DWDM) field trial with line rates per channel <inline-formula> <tex-math notation="LaTeX">$\ge 1.66$ </tex-math></inline-formula> Tb/s using 130 GBaud dual-polarization probabilistic constellation shaping 256-ary quadrature amplitude modulation (DP-PCS256QAM) in a high capacity data center interconnect (DCI) scenario. This research trial was performed on 96.5 km of field-deployed standard single mode G.652 fiber infrastructure of Deutsche Telekom in Germany employing Erbium-doped fiber amplifier (EDFA)-only amplification. A total of 34 channels were transmitted with 150 GHz spacing for a total fiber capacity of 56.51 Tb/s and a spectral efficiency higher than 11bit/s/Hz. In the single-channel transmission scenario 1.71 Tb/s was achieved over the same link. In addition, we successfully demonstrate record net bitrates of 1.88 Tb/s in back-to-back (B2B) using 130 GBaud DP-PCS400QAM.

Intra-Datacenter Interconnects With a Serialized Silicon Optical Frequency Comb Modulator

Powerful warehouse-scale datacenters form the fabric of cloud computing. Efficient computing requires intra-datacenter interconnects with large capacity, low energy consumption, and high scalability. These unique goals present brand new scientific and technological challenges for short-reach optical communications. Silicon photonics (SiP) modulators are promising for intra-datacenter interconnects for its low energy consumption, with the superiority of low cost, small footprint, and complementary metal-oxide-semiconductor (CMOS) compatibility. While currently, the main research focus is to increase the modulation speed of a single SiP modulator for a large interconnect capacity, parallel schemes exhibit better scalability. In this article, we propose intra-datacenter interconnects using dense wavelength-division multiplexing (DWDM) techniques with a single SiP optical frequency comb modulator (OFCM) to achieve potential large capacity and high scalability. The SiP-OFCM consists of serially cascaded microring modulators (MRMs). The MRM based SiP-OFCM is intrinsically compatible with DWDM, performing simultaneously data modulation for multiple optical carriers, DWDM demultiplexing and multiplexing functionalities. We demonstrate an interconnect line rate of 400 Gbit/s with a PAM 4 modulation format using the SiP-OFCM. All four DWDM channels exhibit bit-error ratios below the 33% hard-decision forward-error correction threshold after 2-km single-mode fiber transmission.

MEMS tunable SOI waveguide Bragg grating filter with 1.3 THz tuning range for C-band 100 GHz DWDM optical network

A MEMS tunable integrated waveguide Bragg grating-based filter for C-band optical dense wavelength-division multiplexing (DWDM) network is presented and analyzed in this work. Waveguide Bragg grating being a notch filter in the transmission spectrum is used to realize a tunable filter by varying the applied voltages to the fixed–fixed beam loaded with this grating. The strain across the grating is enhanced by choosing MEMS beam configuration such that the metal electrode is the bottom-most layer of the composite fixed–fixed beam. Device dimensions are chosen to achieve a narrow full width half maximum of 0.77 nm, allowing filtering of adjacent channels of 100 GHz DWDM network. A large Bragg wavelength shift of 10.4 nm (1552.52–1562.92 nm) was achieved at 45.8 V actuation providing tuning for 14 DWDM channels with inter-channel cross talk below − 21 dB, with tuning range of 1.3 THz.

Demonstration of 1.72 Tbit/s Optical Data Transmission Under Worst-Case Turbulence Conditions for Ground-to-Geostationary Satellite Communications

Optical dense wavelength division multiplexing (DWDM) can provide multiple Tbit/s throughput in the future geostationary satellite communications. In this letter, the proof-of-concept demonstration of this technology under worst case atmospheric channel conditions for satellite communications in geostationary orbit is presented. The highest-to-date throughput of 1.72 Tbit/s was transmitted over 10.45 km distance with passive transmitter pointing and active receiver tracking with active single-mode fiber coupling. This throughput was achieved by modulating 40 DWDM channels with uncoded 43.01824 Gbit/s rate per channel. Direct bit-error-rate and signal fluctuations measurements were carried out to assess the link performance. No forward error correction was used.

Investigation on the influence of intensity scintillation and beam wander in space optical uplink DWDM communication system

Dense wavelength division multiplexing (DWDM) has been widely applied in ground optical communication. However, the technology of DWDM is still not mature enough in the space optical communication system. In order to further advance the use of DWDM into space optical communication, the probability density function (PDF) and the bit-error rate (BER) performance of DWDM is investigated in uplink communications under the influence of atmospheric turbulence, consisting of intensity scintillation and beam wander caused by atmospheric turbulence. Numerical results show that the atmospheric turbulence has a great impact on BER and PDF, and wavelength, divergence angel, and other relevant parameters should be carefully considered in this DWDM system. This work can be conducive for improving DWDM design of space optical uplink communication systems.

The Impact of NICTBB in Facilitating the E-Services and M-Services in Tanzania

—ICT services are a key element of communications and important for socio-economic development. In recognition of the importance of this, the Tanzanian Government started to implement a National ICT Broadband Infrastructure Fibre Optic Backbone (NICTBB) in 2009; this development was planned to be implemented in four phases using an optical dense wavelength division multiplexing (DWDM) network technology in collaboration with the Chinese Government through the Chinese International Telecommunications Construction Corporation (CITCC) under a bilateral agreement. This paper briefly explores the NICTBB network technologies implementation, operations and Internet bandwidth costs. It also provides an in depth assessment of the delivery of ICT services such as e-services and m-services in both urban and rural areas following commissioning of the NICTBB system. Following quantitative and qualitative approaches, the study shows that there have been significant improvements in utilization efficiency, effectiveness and the reliability of the ICT service such as e-services and m-services the NICTCBB was commissioned.

Applying PTF/VTF routing policies in multilayer IP/MPLS-based ASON/GMPLS multi-domain networks

The IP/MPLS-based ASON/GMPLS hybrid network architecture enables the interaction between the IP layer and the optical dense wavelength division multiplexing (DWDM) layer. This architecture makes it possible to transfer huge amounts of traffic data on DWDM networks, while supporting Internet Protocol (IP)-based service applications. Additionally, this architecture provides a unified routing scenario, which allows the dynamic routing in both the IP layer and/or optical layer. Cross- layer routing has been addressed in single domain networks scenarios, where the routing policies Physical Topology First (PTF) and Virtual Topology First (VTP) have been proposed and applied. However, applying cross-layer routing using both routing topology policies PTF and VTF has not been investigated in a multi-domain networks scenario yet. In this study, we address this issue and propose a routing scheme to establish traffic connections in the optical WDM layer and the IP layer, which makes the applicability of PTF and VTF in multilayer multi-domain network feasible.

Efficiency of Adaptive and Mixed-Line-Rate IP Over DWDM Networks Regarding CAPEX and Power Consumption [Invited

Optimization of IP over dense wavelength division multiplexing (DWDM) networks is studied under the constraints of energy and cost minimization. Realistic IP traffic mapped to the optical DWDM layer together with leased lines form the basic traffic load, which is expanded by factors of 33 and 100 for a 10-year projection. The DWDM core network (USA 66) is analyzed for mixed-line-rate (MLR) and reach/bandwidth-adaptive scenarios; the latter is realized by optical orthogonal frequency division multiplexing. Both scenarios are studied for flat and hierarchical network approaches and for different channel grid configurations. Network optimization due to capital expenditure and power consumption yield no significant differences for the IP layer regarding different scenarios (flat and hierarchical) or network approaches (MLR and adaptive network). In contrast, the wavelength division multiplexing layer shows benefits for the hierarchical network regarding cost and power and for the adaptive approach regarding the total number of transponders and fibers used. We show that elastic and MLR networks can achieve comparable performance levels using a 12.5 GHz grid. This article is a more detailed version of Klekamp et al., OFC, 2012, OTh3B.1, and extends previous studies in a German network&#x00A0;[J. Lightwave Technol., vol. 30, p. 215, 2012], now comparing the techniques in a US network under different conditions regarding distances and topology.

Analysis of significant factors in DWDM optical communication systems

PurposeThe current generation of light wave systems benefit from increased transmission distance by using optical amplification and increased capacity by using dense wavelength division multiplexing (DWDM) technology. The reach of present systems is limited by the noise contributed by the used amplifiers, combined with nonlinear effects from transmission. This paper aims to address these issues.Design/methodology/approachThe nature and extent of degradations in the optical DWDM systems due to these limiting factors have been discussed in this paper.FindingsIt has been learnt that stimulated Raman scattering (SRS), four wave mixing (FWM) and amplified spontaneous emission (ASE) are the important factors in optical DWDM systems. These factors limit the system capacity of the transmission systems drastically.Originality/valueIt can be concluded from the discussion that while designing an efficient DWDM system, an optimization of the channel separation and the amplifier separation is required to minimize the nonlinear effects (FWM and SRS) along with the ASE noise introduced by inline optical amplifications.

Impact of fibre nonlinearities in optical DWDM transmission systems at different data rates

The impact of major fibre nonlinearities, like stimulated Raman scattering (SRS) and four wave mixing (FWM), in cascaded amplifier dense wavelength division multiplexing (DWDM) transmission system, has been studied at different data rates. SRS has been calculated considering pulse walk off effect. Analysis has been carried out to evaluate signal to noise ratio (SNR) considering the combined effect of SRS and FWM in the presence of amplified spontaneous emission (ASE) noise to achieve minimum noise at different data rates.

THEORETICAL INVESTIGATIONS TO MINIMIZE BIT ERROR RATE BY OPTIMIZING SYSTEM PARAMETERS IN OPTICAL DWDM TRANSMISSION SYSTEMS AT DIFFERENT DATA RATES

The amplifier separation and channel separation has conflicting effects on the noise generated due to the fiber non-linear effects (Stimulated Raman scattering SRS and Four wave mixing FWM) and the Amplified spontaneous emission (ASE) noise introduced by inline optical amplifications. While designing an efficient Dense Wavelength Division Multiplexing (DWDM) system, optimization of the channel separation and amplifier separation are required to minimize the non-linear effects (FWM and SRS) along with the ASE noise. In this paper, theoretical investigations of the optical DWDM systems have been presented to minimize the bit error rate (BER) by optimizing inter-channel separation and inter-amplifier separation at different data rates considering the combined effect of SRS, FWM, ASE, receiver and beat noises.

Investigations on the Effects of Limiting Factors in Optical DWDM Transmission Systems

The current generation of light wave systems benefit from increased transmission distance by using optical amplification and increased capacity by using dense wavelength division multiplexing (DWDM) technology. The reach of present systems is limited by the noise contributed by the used amplifiers, combined with nonlinear effects from transmission. The nature and extent of degradations in the optical DWDM systems due to these limiting factors have been discussed in this paper. Methods to minimize the degradations due to these factors have been proposed.

Using VDSL2 over copper in the vertical string

The described system can be used in a sub-marine Very Large Volume neutrino Telescope where data are transported from Optical Modules (OM), arranged in vertical strings, into the on-shore data acquisition system using copper twisted pairs for the short runs and fiber optics for the long distance connection. All data communication, timing and timing calibration between the Shore Station and the OMs as well as the distribution of power is done via a single Master Module (MM) in the vertical string. VDSL2 provides more than 100 Mbps bandwidth via a single copper twisted pair to transport all the data from an OM to the MM. The same twisted pair is also used to transport power and timing to the OM. A single channel of the long distance fiber optical Dense Wavelength Division Multiplexing (DWDM) system provides the data communication from a MM to the Shore Station. Reliability is a design issue; a large part of the system uses common infrastructure. Each vertical string has two separate paths to the Shore Station via separate junction boxes. Destructive single point failures in the common infrastructure divide the system into two parts, but each part is independently fully functional.

Dense wavelength-division multiplexing dispersion compensators based on chirped and apodized Fibonacci structures: CA-FC(j,n)

Chromatic dispersion compensation is an essential feature of high speed dense wavelength-division multiplexing (DWDM) systems. We propose a dispersion compensator structure whose characteristics meet the optical DWDM system requirements. The proposed structure is based on Fibonacci quasi-periodic multilayer structures composed of layers with large index differences. Studying the dispersive properties of Fibonacci structures with generation numbers j=3 and 4, and calculating group delay (GD) and group velocity dispersion (GVD) of their reflection bands, we have demonstrated that to have a smooth GD and almost a constant GVD in each band of a DWDM system, one needs not only to suitably chirp the structure refractive index profile, but also must properly apodize it. We also demonstrate the possibility of achieving high slope GDs and large GVDs by means of high order Fibonacci structures with thicker layers. Finally, by varying the layer dimensions and refractive indices as well as Fibonacci's order, one can design DWDM dispersion compensators suitable for distances as long as 220 km.

Metro optical networking

Today's telecommunication networks support an ever-increasing mixture of statistical and deterministic data traffic. Current networks rely on time division multiplexing (TDM) hierarchy, originally invented to be the most efficient multiplexing technique possible for 64-kb/s voice, but this architecture is not particularly suited to statistical data traffic. A router or ATM switch can connect into a dense wavelength division multiplexing (DWDM) transport network by mapping packets or cells directly onto a wavelength without the intervening use of a SONET or SDH TDM. In effect, a TDM can be replaced with an optical DWDM, which can increase bandwidth utilization, facilitate networking, and reduce cost. DWDM can defer or completely eliminate the need for extra fiber, which is especially significant for providers who have a fiber-exhaustion problem, and it can easily coexist with today's SONET/SDH networks or with older fiber-optic terminals (FOTs) operating on asynchronous protocols. DWDM has already revolutionized the telecommunication industry by providing the infrastructure for long-haul optical networks. As the DWDM revolution moves into the metropolitan interoffice (IOF) and access networks, it will rely on the optical add/drop multiplexer (OADM) as its fundamental network element for metro optical networking. In this paper, we examine the market needs for metro optical networking; introduce the concept, network topology, and architectures for metro optical rings; and describe the key requirements that address the needs of service providers. We also discuss the components of the network and review the general requirements that will enable the next step in the evolution — extending the DWDM ring architecture to business access customers. Metro optical networking represents a unique opportunity for service providers to begin deploying a data-centric high-bandwidth services infrastructure.

Surviving a disaster [optical communications

The next-generation optical communications network, not surprisingly at all, will be as optical as it can be. Only optical dense wavelength-division multiplexing can provide the bandwidth elasticity that new emerging communications services demand. This is well understood, and despite an apparent slowdown in the world economy, multibillion-dollar commitments have been made to upgrade existing networks to next-generation DWDM. The next optical network is expected to be massive, yet flexible and ubiquitous. Current DWDM technology supports 160 wavelengths (in the C+L bands) per fiber; at 10 Gb/s this amounts to an astonishing 1.6 Tb/s aggregate bandwidth per fiber. Research has also demonstrated that ultra dense WDM (UDWDM) is possible, and it is a matter of time until 320 wavelengths (and a little later 640) will be multiplexed in a single fiber. As a consequence, we examine what the next optical network should be like, and proactively identify some areas that require special attention. One of the critical areas is service and network survivability not only when a node and/or link fails, but also when a cluster of nodes and/or links fail; that is, avoiding a disaster. Disaster avoidance has also become more important for both natural disasters and geo-political unrest.