To satisfy the ever-increasing data traffic growth associated with a considerably diversified and unprecedented range of emerging network applications and services as well as reduce CAPEX and OPEX [1, 2], Cloud accessnetworks have recently been proposed which seamlessly integrate traditional opticalaccessnetworks, metropolitan opticalnetworks and 4G/5G mobile fronthaul/backhaul networks. As discussed in Chapters 1-2, it is greatly advantageous if CANs not only have strong adaptability to highly dynamic traffic with arbitrary bandwidth granularity, but also simultaneously accommodate various major network design features including, for example, signal modulation format, signal detection scheme, WDM grid, multiple access technique, as well as network topology. In addition, CANs are also envisaged to be equipped with a wide diversity of SDN functionalities to dynamically provide flexible and fast on-demand connections/services with elastic bandwidth granularities at wavelength, sub-wavelength and sub-band levels. In this thesis, numerical and experimental investigations have been undertaken to explore the feasibility of practical implementation of three novel techniques essential for future CANs from device to network architecture level: i) software reconfigurable optical transceivers with channel multiplexing/demultiplexing in the digital domain without involving any extra analogue hardware, ii) DSP-switched O-E-O conversion-free flexible ROADMs, and iii) DFMA PONs with DSP-enabled software reconfigurability.
The network can also be modelled as a three-layered architecture as shown in Fig- ure 3.1. The application layer resides on top of the architecture including all types of services, e.g., voice, video, and data. The intermediate layer encapsulates data from the application layer with various protocols based on electronic switching and multiplexing techniques. The traffic of the electronic layer is aggregated into the optical layer, where they are carried by wavelengths. Form the viewpoint of customers, an end user’s YouTube videos or business data of a company are first generated in the application layer and then passed to the electronic layer. Hundreds of such small data streams are integrated into one optical wavelength and transmitted through the network towards their destinations. Note that it is possible for the application layer to directly access the optical layer [41, p. 7], as illustrated by opticalaccess service in Figure 3.1. This capacity is independent of the specific protocol in the electronic layer and, thus, offers great transparency and
trust-free QKD immune to measurement attacks, were mostly insensitive to the positions of their measurement modules, but could suffer harshly from the background noise generated in the indoor environment. If immunity to measurement attacks was not required, we could simply collect QKD signals at the ceiling and couple them into optical fibers along with other data channels. With decoy-state techniques, we showed that we could tolerate up to 30 dB of coupling loss in such a setting, provided that full alignment is achieved. At long distances, the Raman noise induced by the data channels would also take its toll on the maximum secure distance, limiting it to tens of kilo- meters. Both Raman noise and the background noise due to the artificial light source in the indoor environment could be orders of magnitude larger than the static dark count of single-photon detectors. We also showed that in the low-coupling-loss regime, CV-QKD could offer higher rates and more resilience to back- ground noise than DV-QKD systems. But, overall, DV-QKD schemes could offer a more stable and flexible operation adapt- able to a wider range of scenarios. In short, using our analytical results, we can identify the winner in realistic setups that enable high-rate wireless access to future quantum networks.
system needs little or no upgrade whenever changes in the modulation format of the RF signal occur . The transmitter configuration is extremely simple and cost effective but its performance is severely limited by the laser modulation impairments. The frequency chirp, significant non-linearities and high RIN cause poor frequency stability and transmission integrity. In terms of the energy consumption, although a prior it is low because a single component is used, the low capacity makes the consumption per bit ratio (Joules per bit) quite high . RoF systems using direct microwave intensity modulation of a laser diode are commercially available up to limited radio frequencies (up to about 2 GHz, for wireless services such as GSM and UMTS). Therefore, the major drawback of this technique is that the operation at higher microwave frequencies is prohibited by the restricted modulation bandwidth of the laser diode and by the fiber dispersion, which causes fading of the two modulation sidebands. Such microwave frequencies may only be handled by sophisticated very high frequency optical analog transmitters and receivers, and careful fiber dispersion compensation techniques . Another disadvantage of this technique is the changing of the wavelength with the laser bias current. This chirp of the resulting pulses, where the carrier frequency of the transmitted pulses changes with time, produces a broadening of the optical spectrum relative to the bandwidth and possesses very poor dispersion limits. Serious degradation of the system will appear if the operating wavelength does not lie close to the zero-dispersion wavelength . The simplicity of direct modulation of semiconductor lasers has proved attractive for many applications and following early work on modulation characteristics. Rapid progress has been made in reducing electrical parasitics of laser structures and optimizing laser parameters for high-speed operation . Applications of direct analogue laser modulation include cable TV, base station links for mobile communication, and remote antenna.
There have been extensive studies on protection schemes to handle faults in opticalnetworks [46, 47]. Mostly, the proposed schemes consider single link failures (SLF) only. Path Protection and link protection are most popular schemes used to handle faults, since they provide guaranteed fault recovery and fast recovery time . For path protection, two techniques have been studied widely - Dedicated Path Protec- tion (DPP) and Shared Path Protection (SPP) [10, 48–52]. Under dynamic traﬃc scenario and using path protection, when a new request for communication from S to D is received, the objective to make provisions for two lightpaths - a primary lightpath from S to D and a backup lightpath (also from S to D), using routes that are fiber-disjoint. If the system is able to handle the request for communication (i. e., the search is successful), the primary lightpath is set up and used unless there is an edge failure in the path used by the primary lightpath. Depending on the type of path protection (e.g., 1+1 dedicated path protection, 1:1 dedicated path protection or shared path protection), the backup lightpath is set up at the same time as the primary lightpath or is set up if needed. If the path used by the primary lightpath is aﬀected by a faulty component, the communication is resumed, using the backup lightpath [51, 52].
A key part of the review will be the consideration of the contribution that different means of meeting demand might make. This includes DG, flexible demand and storage but also the sorts of interventions addressed by the “FlexibleNetworks” project, e.g. dynamic network reconfiguration, real time thermal ratings and improved voltage management. Any new standard should make clear that these are all viable options the adoption of which should depend on their cost relative to other options and their feasibility throughout a ‘typical’ year of operation. That is, the ability of ‘smarter’ network interventions to contribute to meeting demand (or, for that matter, facilitating generation) depends on prevailing conditions and, in the case of network configuration, the coincidence of particular conditions in neighbouring groups. Any risks associated with such interventions should also be part of an option evaluation and should include a realistic assessment of both the probability and the consequences of, for example, real-time continuous ratings being exceeded. In the latter case, as was discussed above, exceedance of a continuous rating does not necessarily that an asset’s critical temperature would be reached or a circuit would be switched out. Moreover, the extent of exceedance, its duration and the probability of occurrence may be such that any acceleration of ageing of the affected asset is insignificant.
Shown in figure 1A is a photograph of a nanowire film on a PET substrate. This was prepared by depositing 28 mg/m 2 of AgNWs onto a cellulose membrane by vacuum filtration. The film was then attached to the PET substrate using heat and pressure (see methods) and the cellulose dissolved in acetone. It is clear from this image that the film appears to be of very high optical quality. While this is generally true, we note that the films appear very slightly milky due to light scattering from the nanowires 28 . We can test the optical uniformity of these films by taking a transmission scan of the deposited film. This involves measurement of the local white light transmittance with a spatial resolution of 4µm, measured over an area of 2mm×2mm. We can characterise the uniformity of the transmittance by calculating the standard deviation of the transmittance over all pixels, ∆T. This worked out to be ∆T=1.8% for the film shown in figure 1A, demonstrating the optical quality of these films. When normalised to transmittance, this gives ∆ T / T = 2.1% . We will use this technique below to investigate the film uniformity as a function of film thickness.
Along with the emergence of IP as a main network layer resource, there have been a lot of technological advancements in optics as a transmission medium. The view of optical layer as only the transmission medium is changing because of the huge difference of bandwidth between traditional copper cables and fiber optics plus the quick and effective reconfiguration potential of optical layer cross connects (OLXCs). Use of opticalnetworks can provide opportunities to those applications that require huge bandwidth. It can also increase the number of services that a network may host, but at the same time the high speed reconfiguration and an enhanced number of optical channels can complicate the organization of resources (optical). Simple opticalnetworks that are currently in operation use protocols and algorithms that are not resilient enough to incorporate IP. These need to be changed in order to enable it to keep up with the connectivity and capacity that is changing dynamically between network nodes. They should be robust enough to cope with the unavoidable network fluctuations that current day Internet can stand.
A social network site is a web site that Acts as a destination hub for individuals to establish relationships with co-workers and by doing so, enable them to jointly build, or expand, their professional and social networks. It includes different tools for people to interact with each other, contribute information to the site, participate in different site activities, and build a sense of community in an informal and voluntary manner. It allows the user to define an online profile (or personal) , list their connections (e.g., friends and colleagues) , receive notifications on the activities of those connections participate in group or community activities , control permission, preference and privacy settings We define social network sites as webbased services that allow individuals to do the Following  construct a public or semi-public profile within a bounded system  articulate a list of other users with whom they share a connection, and  View and traverse their list of connections and those made by others within the system. The nature and nomenclature of these connections may vary from site to site .
We present spectral amplitude coding, optical code division multiple access technique in free space optical network utilizing multi-wavelength laser source. Using the simulation software, the system performance is analyzed while the impact of the turbulence is also considered. The simulation is implemented using modified double weight (MDW) code and for 3 users. The results show that using receiver aperture diameter D = 4 cm and beam divergence θ = 1 mrad, transmission distance 2.8, 2.45 and 2.25 km is achievable for weak, moderate and strong turbulence respectively. This distance can be improved if bigger D or smaller θ were utilized. Moreover, it is shown that the increment of turbulence increases jitter, which downgrades system performance.
– A set of access rules define the relations among Administrative Domains and are used to combine credentials and obtain new Domains and are used to combine credentials and obtain new roles for the same subject in Administrative Domain to which he does not belong.
In this paper, we discuss and analyze an optical code division multiple access for multiple user system. Media access control implementation has been considered. For fulfilling the huge need of bandwidth services, technolo- gy tends to move to opticalnetworks and three major optical systems come into existence. Code division of the optical network is most used and real concept interacted with users up to this time. Optical code division mul- tiple access provides complete spectrum to each and every user for the time of accessing the channel. In the pa- per, we have proposed network architecture with optical encoder and decoder along with optical code translator which is supporting multiple user systems. We integrate the code translator with encoding and decoding of opti- cal code to use the optical network at full extent and present the simulation validation results of 6 Gb/s 3-hop transmission by use of proposed architecture. Further, we have implemented experimentation with 6 users 3 Gb/s optical code division multiple access network. Through simulation structure, it is shown that the combina- tion of encoding with EDFA in multiple user environment system provides improvement in bit error rate and also improves the multiple access interference. With increase of users in the network, MAI value increases and our proposed scheme controls interference in the network.
As mentioned earlier, we considered two separated IoT networks connected to a PON access network. Each IoT network consisted of 50 IoT objects, 25 relays, one coordinator and one gateway. In addition, each IoT network connected to an ONU, both ONUs are connected to one OLT. The IoT objects, relay elements and the coordinator in each IoT network are distributed through 30m×30m area. The gateway is placed 100m away from the coordinator. The distribution of IoT objects is random and uniform while the position of each relay element is at every 6m distance. All devices in the IoT network communicate through using the Zigbee protocol. On the other hand, the gateway is connected to the ONU through Gigabit Ethernet link and the ONU is connected to the OLT through an optical fiber. We only consider uplink direction as it carries the highest amount of traffic. Consequently we do not allow the traffic to pass from one IoT network to another through the OLT. Our model accounts for the traffic induced power consumption in PON entities as well as in the receiving and transmitting components of the IoT network (including propagation losses and the power amplification) . VMs in different layers are hosted by a CPU with an average power consumption of 5.5W . The CPU utilization of the VMs belonging to a certain type is assumed to be independent of both the number of served IoT objects and the different traffic reduction percentages.
Cisco IOS Flexible NetFlow is the next generation in flow technology, allowing optimization of the network infrastructure, reducing operation costs, and improving capacity planning and security incident detection with increased flexibility and scalability. The Supervisor Engine 8-E is the first Cisco Catalyst supervisor engine to provide optimized application visibility with FNF with a capability of 128,000 FNF entries. The Supervisor Engine 8-E, with a custom-built ASIC, delivers next-generation flow technology with superior flexibility and comprehensive visibility extending from Layer 2 (MAC and VLAN) to Layer 4 (TCP, User Datagram Protocol [UDP] flags, etc). The flow data collected by FNF can be exported to an external collector for analysis and reporting, or tracked by the EEM. The Cisco Catalyst 4500E Supervisor Engine 8-E can enable powerful, on-box, and customizable event correlation and policy actions with EEM, allowing the switches to trigger customized event alarms or policy actions when the predefined condition is met. With no external appliance required, customers are able to use existing infrastructure to perform traffic monitoring, making traffic analysis economical even on a large IP network. Details about Cisco Flexible NetFlow are available at
Abstract—The technology involves a new type of compact device based on magneto-optics in a fiber micro modulator. This type of modulator allows the user to inter manipulate and control the propagation of the incoming light. The operation mechanism uses external magnetic field to manipulate Fe micro particle in order to cause modulation of an optical signal that propagates along an optical waveguide. This paper has presented yttrium iron garnet (YIG) and lithium niobate (LiNbO3) which are examined for use as a wideband magneto-optic modulator. A wideband YIG modulator has recently been developed which represents a great improvement over other magneto -optic modulators.
For interference coordination among optical wireless cells, the medium access control (MAC) frame is divided into data and BB slots. Data transmission is carried out during the data slot and the BB is transmitted during the BB mini slot. Each receiver must transmit a BB to announce its presence to other APs so that they may autonomously determine whether or not they can reuse the reserved chunk. To this end, it is assumed that UE μ has transmitted a BB after receiving data during its data slot. The busy burst signal transmitted by UE μ propagates through the optical channel and is received both at APs a and b. The received signal at the serving AP a informs the transmitter that the minimum SINR target has been met. Furthermore, additional informa- tion can be piggybacked to the BB signal for feedback and control purposes. By contrast, the received BB sig- nal at AP b makes it aware of the amount of CCI it potentially causes to the active receiver μ if it were to reuse the reserved resource. By measuring the signal power received during the BB slot, the AP b decides autonomously whether or not it may reuse the reserved chunk so as to limit the interference to a threshold value. To this end, the received BB signal at AP b can be written as
Present communication links requires high bandwidth, good channel capacity, and minimum errors with physical security. Free space optical (FSO) communication is the way by which we can achieve these characteristics simultaneously. A FSO is the communication system where air is used as a medium to transmit light wave signals to another location. These links are mainly characterized by geometric or atmospheric attenuation. The geometric attenuation can be controlled by changing the parameters like transmitter diameter, divergence angle and link distance. The atmospheric attenuation depends on weather conditions like fog and rain . The main advantage of optical communication is that optical signals do not leak through walls nor interfere with delicate wireless equipment. Thus providing security from intruders. Optical wireless networks can be used in many network applications including structural health monitoring within a fixed infrastructure; real-time performance feedback from sensors placed inside airplanes; and rapid upload/ download links within various terminals in settings, such as indoor offices, houses, airplane cabins, connection of avionic systems  and shallow-water sensor networks .
Erbium Doped fibre Amplifier (EDFA) is one of the critical technologies used in optical fibre communication system. In the future better technologies to enhance EDFA performance will be developed. In order to increase the gain bandwidth of EDFA better gain equalization technology for high accuracy optical amplification will be developed. Also, in order to achieve a higher output power, and a lower noise figure high power pumping lasers that posses excellent optical amplification Characteristics with outputs of more than +20dBm and very low noise figure are envisioned to exist in the near future.