Sharing direct fiber channels between protection and enterprise applications using wavelength division multiplexing

This chapter is an introduction of the Wavelength-division multiplexing (WDM) technologies (such as Dense WDM and coarse WDM) and their recent applications in optical networks. WDM is used to multiplex multiple optical carrier signals on a single optical fibre by using different wavelengths of laser light to carry different signals. This allows for a multiplication in available bandwidth and, in addition, makes possible to perform bidirectional communications over one strand of fibre. We present the optical components used in WDM and review some of the most important applications of the technology.

As Fibre Channel (FC) becomes the protocol of choice within corporate data centers, enterprises are increasingly deploying SANs in their data central. In order to mitigate the risk of losing data and improve the availability of data, more and more enterprises are increasingly adopting storage extension technologies to replicate their business critical data to a secondary site. Transmitting this information over distance requires a carrier grade environment with zero data loss, scalable throughput, low jitter, high security and ability to travel long distance. To address this business requirements, there are three basic architectures for storage extension, they are Storage over Internet Protocol, Storage over Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) and Storage over Dense Wavelength Division Multiplexing (DWDM). Each approach varies in functionality, complexity, cost, scalability, security, availability , predictable behavior (bandwidth, jitter, latency) and multiple carrier limitations. Compared with these connectiviy technologies,Coarse Wavelength Division Multiplexing (CWDM) is a Simplified, Low Cost and High Performance connectivity solutions for enterprises to deploy their storage extension. In this paper, we design a storage extension connectivity over CWDM and test it's electrical characteristic and random read and write performance of disk array through the CWDM connectivity, testing result show us that the performance of the connectivity over CWDM is acceptable. Furthermore, we propose three kinds of network architecture of SAN extension based on CWDM interface. Finally the credit-Based flow control mechanism of FC, and the relationship between credits and extension distance is analyzed.

Elastic optical network (EON) is a promising candidate for the next generation optical transport network because of its high spectrum efficiency and flexible spectrum allocation. However, to migrate from today’s dense wavelength division multiplexing (DWDM) network to EON, optical nodes such as reconfigurable optical add/drop multiplexers (ROADMs) should be replaced with the ones with expensive flexi-grid wavelength selective switches (WSSs). Thus, whether and how today’s optical network will be evolved to EON is still under debate. Meanwhile, with the technical maturity of optical super-channels that transmit bit rates at the level of 1 Tb/s, super-channels are expected to dominate the future optical transport network because of their attractiveness of high spectrum efficiency and superior cost effectiveness. In this paper, we propose a new quasi-coarse wavelength division multiplexing (Quasi-CWDM) optical network architecture that is compatible to today’s WDM network in spectrum operation, while still maintaining the flexibility of adaptation between the bit rate and the transparent reach of an optical super-channel, but not requiring expensive flexi-grid WSSs. Specifically, the Quasi-CWDM optical network employs large fixed frequency grids, whose spacing falls between the traditional CWDM and DWDM, e.g., 200 GHz or 400 GHz. To maintain the flexibility between the bit rate and the transparent reach of an optical super-channel, different modulation formats are chosen according to channel physical distances. To minimize network hardware cost and maximize carried user traffic demand, we develop a mixed integer linear programming (MILP) model and a heuristic algorithm that can efficiently groom upper-layer IP traffic onto the optical layer by optical super-channels. We compare the design based on the Quasi-CWDM network to those based on the DWDM network and the advanced EON. It is found that the proposed Quasi-CWDM network has a much lower hardware cost than the other two types of networks, while achieving spectrum efficiency close to EON.

There is a rapidly increasing data flow between sensors and on-board processors in avionic platforms. Electro-optic (EO) sensors are moving to hyperspectral and radar to phased array to enable precision targeting, wide field of view surveillance and navigation. These trends call for next generation optical network technology which has to provide increasing high speed data transmission under harsh conditions. Recent developments go beyond simple point-to-point fiber links towards establishing optical distribution networks to deal with the data traffic [1]. A flexible and potentially low-cost implementation is the passive optical network (PON) which scales easily to increasing needs simply by upgrading the peripheral units without need to change the fiber connections and infrastructure. PONs are well established in the commercial access market with the increasing push to fiber-to-the-home (FTTH) technologies which has led to the development of a variety of low-cost devices for these networks. A key enabler in our development of an avionics PON is the reflective semiconductor optical amplifier (RSOA) which combines amplification and modulation into a single device [2]. The RSOA is a non-resonant device, thus wideband with the potential for ruggedness, especially high temperature operation with small or no need for cooling. At higher data rates up to 20 Gbps a related device, the reflective electro-absorption modulator with integrated amplification (R-SOA-EAM) can be used instead. To complete the adaptation we replaced the laser, commonly used to provide optical input power in a PON architecture with another non-resonant device, the superluminescent LED (SLED). To create upgrade flexibility we utilized wavelength division multiplexing (WDM) which allows addition and subtraction of channels without changing hardware. Coarse WDM (CWDM) was chosen over Dense WDM (DWDM) for two reasons: the large channel width (20nm) of CWDM reduces cost by relaxing fabrication tolerance and renders the use of temperature control unnecessary, thereby increasing reliability. The concept and current state of development of our optical network is described in this paper.

A trend of high speed computing and communication has demonstrated incredible performance increase, 1000x in every 10yrs. Such enhancements have been realized partly due to Moore’s law based and parallelism based progresses [1]. To keep up such a trend for future, we have to integrate photonics on a chip, i.e., Si photonics, especially on-chip WDM (wavelength division multiplexing) architecture [2]. In the history of the fiber optics, WDM has brought significant increase in bandwidth of optical communication and currently the channel spacing in WDM is as small as 0.8 nm and will soon be 0.4 nm. However, Si photonics has used coarse WDM where the channel spacing is as large as 10nm. The reason for the large spacing is a large TO (thermooptics) coefficient of Si. Due to chip temperature fluctuation on a chip, wavelength is changed widely, malfunctioning WDM. This is the fundamental limit in shrinking the wavelength spacing. In other words, the key challenge to implement on-chip WDM is to lock its channel wavelength within a given channel spacing. In this talk we will focus on silicon nitride based Si photonics, i.e., medium index contrast optics, MiDex Si photonics to lock the channel wavelength within the current dense WDM (DWDM) in optical fiber communication, i.e., 0.8nm spacing [3]. Fig. 1 shows bending radii of various waveguides vs. index difference between the core and cladding of the waveguide. Generally, Si waveguide and SiO2 cladding have been used in Si photonics, where index difference is 2.0. The materials set has a high index contrast, i.e., here we will refer it to as HiDex (high index contrast). The advantage is a sharp bending of the waveguide, which reduces device footfprints and allows high density integration of optical devices on a chip. Althougt the disadvantage is large light propagation loss, Si process technology allows to minimize the roughness of waveguide to reduce the loss to ~1dB/cm. It is known however that Si has a large TO coefficient, i.e., temperature dependence of refractive index. It has been reported that chip temperature has changed about 50˚C during its operation. Thus, on-chip temperature fluctuation changes wavelength, malfunctioning of WDM. To avoid it, a large channel spacing, i.e., 10nm has been chosen. We have been focusing a slightly smaller index contrast system in the following two reasons: When we choose SiNx waveguide and SiO2 cladding, the minimum bending radius is 10 µm which is still small enough and the TO coefficient of SiNx is ~1/10 of that of Si. This indicates this materials system should be robust against temperature fluctuation on a chip. Of course Planar Lightwave Circuit based on silica fiber technology has smaller TO coefficient, here we refer it to as LoDex (low index contrast), but the bending radii should be ~1cm. Thus, we have proposed MiDex Si photonics instead of current HiDex Si photonics. SiNx (0.6-0.8 µm thick) can be deposited on SiO2 (2µm thick) using a physical vapor deposition (PVD) technique. Chemical vapor deposition techniques have widely been used, but CVD SiNx contains N-H bonds that absorb 1520nm, that is in optical communication wavelength range of 1550nm. To dissociate H from SiNx, CVD SiNx should be annealed at high temperature such as 1100˚C. To avoid such high temperature annealing, we have chosen PVD SiNx, which should be free from N-H bonds. We have demonstrated SiNx without such absorption. The present report has verified the advantage of PVD SiNx over CVD SiNx, temperature stability of filter characteristics of ring based resonators, and athermalization using polymer materials.

In wavelength division multiplexing (WDM) systems, such as the fiber-to-the-home (FTTH) service (e.g., wavelength 1.31/1.55/1.49 mm in the EPON and wavelength 1.31/1.545/1.5x mm in the APON), coarse and dense WDM are two key technologies. In general, it takes two steps to accomplish this mixing (coarse/dense) WDM functions. In order to make the WDM device compact and low loss, it is necessary to integrate these two WDM functions into one step. In this paper, we propose two typical designs of the coarse/dense multiplexers, which multiplex the coarse/dense-WDM (C/D-WDM) signals simultaneously. We believe that, although their operation principle is simple, the proposed structures simplify the design of integrated photonic devices and will be needed in future WDM systems, specially for the WDM filter in the FTTH service. The proposed devices consist of a grating-assisted symmetrical or asymmetrical Mach-Zehnder interferometer with the wideband coupler (WBC) and/or the 3dB coupler. Depending on different operation principles, the WBC coupler operates as a 3dB coupler in two wavelength bands or operates as a 3dB coupler in one wavelength band and a cross-state coupler in another one. In this paper, firstly, the operation principles of the proposed C/D-WDM Multiplexers are demonstrated though an example of multiplexing three signals (l1/l2/l3) in two wavelength bands, where l1 (e. g., 1.31mm) belongs to the first band and l2/l3 (e. g., 1.55/1.5x mm) belong to the second band. Then, the design procedure and simulation results of those C/D-WDM multiplexers and related components such as the WBC coupler and planar gratings, which are based on the silica material, are given. Finally, some related issues such as polarizatin dependence and material dispersion are discussed.

In this study, the design and characterization of a photonic crystal fiber (PCF) as a light source for a mid-infrared supercontinuum generation (SCG) is presented. This PCF is based on a highly nonlinear chalcogenide $${\text{As}}_{40}{\text{Se}}_{60}$$ As 40 Se 60 background material with a hexagonal structure arrangement of air-holes rings. The PCF parameters such as the chromatic dispersion (D), the effective refractive index ( $${n}_{eff}$$ n eff ) and the nonlinear coefficient (γ) have been investigated. We study the stimulated SCG in two types of dispersion regimes: anomalous and all-normal dispersion (ANDi). We initiate the study by sending a 28.4 fs wide optical pulse with a peak power of 10 kW and a central wavelength of 2.8 µm through a 2 cm long PCF. In the anomalous dispersion, we demonstrate the generation of coherent and broadband SCG spectrum spanning the wavelength region from 1.6 to 7.8 µm. While, in the ANDi regime we demonstrate the generation of a broad, ultra-flat-top and highly coherent SCG spectrum extending from 2 to 4 µm at 6 dB spectral flatness. Thus, we achieve ultra-flat SCG spectrum source with a bandwidth as wide as 2400 nm within only 2 cm propagation length of the proposed PCF. This spectrum range is very suitable for variety of applications in mid-infrared region such as optical metrology, frequency comb generation, and optical coherence tomography (OCT). Results further demonstrate that with an applied pump power of 15 kW through the ANDi regime, a flat spectral bandwidth of 380 nm (wavelengths ranging from 1260 to 1640 nm) at just 3 dB spectral flatness is achieved. This band covers the five-telecommunication optical bands O-, E-, S-, C- and L-bands that comply with ITU-T-compliant wavelengths for wavelength division multiplexing (WDM) applications like coarse WDM (CWDM) and dense WDM (DWDM).

The ever increasing demand for higher data rates and minimum latency has resulted in a widespread growth of optical fiber communication over the last decade. Dense Wavelength Division Multiplexing (DWDM) technique is one of the most important techniques used to establish a long-distance link with higher data rate transmission. However, when the requirement is to transmit the data inside a metropolitan (shorter range) city, DWDM has certain limitations like wideband change, more power consumption, and high-cost factor for lower channels. CWDM (Coarse Wavelength Division Multiplexing) can easily overcome these disadvantages. In this paper, the performance of 8 channel optical transmission link for Coarse Wavelength Division Multiplexing based optical network has been analyzed and compared. Here we’ve compared the performances in terms of Q-factor (Quality factor), BER (Bit Error Rate), and eye height in the eye diagram. For experimental setup and simulation, Optisystem-18 software is used.KeywordsCWDMBitrateAPD photodetectorLow pass filterQ-factor

In designing the backbone network for the province of East Kalimantan using Dense Wavelength Division Multiplexing (DWDM) and Optical Transport Network (OTN) devices which cover 10 districts and cities consisting of 34 segments, of which 34 segments consist of 10 OTN DWDM sites and 16 Optical Land Amplifier sites ( OLA). From the results of the design and simulation of the backbone network, it was found that the value of the Optical Link Power Budget (OLPB) < 50 dBm where this value is the ideal value in deploying a DWDM OTN backbone network, and the range of the Optical Signal Noise Ratio (OSNR) is between 20 dBm < OSNR < 40 dBm, which is the ideal value for OSNR, and has an Optical Rise Time Budget (ORTB) < 60 ps, and also has a segment margin system of > 7 dB.

In designing the backbone network for the province of East Kalimantan using Dense Wavelength Division Multiplexing (DWDM) and Optical Transport Network (OTN) devices which cover 10 districts and cities consisting of 34 segments, of which 34 segments consist of 10 OTN DWDM sites and 16 Optical Land Amplifier sites ( OLA). From the results of the design and simulation of the backbone network, it was found that the value of the Optical Link Power Budget (OLPB) < 50 dBm where this value is the ideal value in deploying a DWDM OTN backbone network, and the range of the Optical Signal Noise Ratio (OSNR) is between 20 dBm < OSNR < 40 dBm, which is the ideal value for OSNR, and has an Optical Rise Time Budget (ORTB) < 60 ps, and also has a segment margin system of > 7 dB.

Coarse Wavelength Division Multiplexing (CWDM) technologies are being widely deployed internationally in metropolitan and access networks due to the increased demand for delivering more bandwidth to the subscriber, created by the need of enhanced services, (Koonen, 2006). For metro, and mainly for access networks applications, an increment in capacity may be achieved with a cost-effective multiplexing technology without the need for the high channel counts and closely spaced wavelengths typically used in long haul networks. A channel space of 20 nm, as proposed in the G. 694.2 ITU Rec., can be used relaxing the processing tolerances and potentially lowering the cost of components. CWDM technology reaches those requirements and it has been proposed for these applications. It is in this context that holographic optical devices have a potential use. This chapter describes the theory, design, and experimental results of a generic multipurpose device that can operate as a tunable wavelength filter, wavelength multiplexer and wavelength router. This device could be especially useful in optical network applications based on both Coarse and Dense Wavelength Division Multiplexing technology (CWDM/DWDM). The enabling component is a Ferro-electric Liquid Crystal (FLC) Spatial Light Modulator (SLM) in which dynamic holograms are implemented in real time. As a consequence, the device will be able to carry out different functions according to the hologram recorded on the SLM. The great advantage of this device is polarization insensitivity in the region of operation, allowing low cross-talk and simple handling. As hologram management is the basis for this device, some topics in the Computer Generated Hologram (CGH) design process are commented on and general guidelines are also considered. Laboratory experiments have demonstrated the capability of a phase FLC-SLM, with the great advantage of polarization insensitivity operation, to diffract the incident light according its wavelength and hologram patterns, for the use in the former applications. Two typical applications of this technology are described: the first one is a design of an equalized holographic Reconfigurable Optical Add-Drop Multiplexer ( ROADM), where this device can address several wavelengths at the input to different output fibers, according to the holograms stored in a SLM (Spatial Light Modulator), all the outputs being equalized in power; the second one is dealing with the design of an holographic router with loss compensation and wavelength conversion whose main application is in Metro networks in the interconnection nodes. This device uses a SOA (Semiconductor Optical Amplifier), in the non linear region, to do the wavelength conversion and, in addition, to supply the gain in order to compensate for the intrinsic losses of the holographic device.

With the launch of 5G services, new networks are constantly required to increase data traffic and eliminate bottlenecks. Accordingly, the optical communication network for 5G needs to continuously evolve to a high-speed, high-capacity, infrastructure to provide high-quality service. However, due to the limited number of fiber cables, the maximum capacity extension that can be transmitted is limited. To solve this problem, a new optical transport network configuration solution must be studied. Therefore, the adoption of DWDM(Dense Wavelength Division Multiplexing) scheme, which is most advantageous for increasing the data capacity among the various optical communication network technologies proposed to date, is rapidly increasing.[1] However, because DWDM is advantageous in capacity, but requires a large number of wavelengths, DWDM SFP optical module inventory per channel can accumulate, leading to an increase in inventory costs. In order to solve this problem, we applied wavelength tunable SFP(T-SFP) which can realize more than 16 channels with one SFP module and summarized the results of study on tunable SFP.

The volume of traffic carried on the Optical Transport Network (OTN) is continuously growing, not only due to the increase of new services, new applications, and the number of both connected users and smart devices, but also owing to the rapidly growing Data Center Interconnect (DCI) market. As a result, telecom operators need to upgrade their transport networks to cope with these new traffic requirements. This tremendous increase in bandwidth demand will also introduce energy bottlenecks in OTNs. The telecommunication networks' significant Greenhouse Gas Emissions (GGE) is another challenge that must be addressed in OTN design and planning policies. Thus, energy-efficient OTN architectures are currently attracting the attention of telecom operators. The candidate OTN architectures are: (1) the conventional Dense Wavelength Division Multiplexing (DWDM) fixed grid with high Single Line Rates (SLRs); (2) the conventional DWDM fixed grid adopting Mixed Line Rates (MLRs); and (3) the Elastic Optical Network (EON) or flexigrid-based architecture which is enabled by the Optical Orthogonal Frequency Division Multiplexing (O-OFDM) technique. This paper evaluates the power consumption of the abovementioned OTN architectures under different traffic loads and patterns, as well as different network physical topologies. In order to perform the evaluation, new heuristic algorithms are specifically developed for the green design and planning of data center optical interconnects.

40-Gbit/s ETDM Channel Technologies for Optical Transport Network

As the importance of the Internet increases, developing technologies for data transmission at higher bit rates became as important as challenging. Optical Transport Networks (OTN), based on Wavelength Division Multiplexing (WDM), emerged to meet this need. ITU has standardized OTN, including its management functions. Network elements in OTN store performance monitoring information as time series of performance events, which could be explored to enable more efficient preventive maintenance and better resource provisioning. With the use of time series forecasting models, faults could even be avoided, along with Service Level Agreement breaches. In this work, we propose the use of time series forecasting in performance monitoring of OTN, investigating how three forecasting methods behave in scenarios of stability and degradation in network performance and how the number of monitoring intervals affects their accuracy. In accordance with results we state recommendations for application of tested time series forecasting methods in managing OTN.