Introduction to Automatically Switched Optical Network (ASON)

Optical backbone networks which based on SDH/SONET and WDM technologies are designed mainly for voice applications. However, it gradually fails to satisfy current needs triggered by rapid growth of data traffic. Thus, resources available to users often cannot be allocated properly because of the inherent inflexibility of manually provisioned large-scale optical networks. While with the advances in optical component technology, a significant amount of attentions are attached to the emerging technology of Automatically Switched Optical Networks (ASON), which enables more dynamic and diversified networking that may change the network characteristics dramatically.

Definition of ASON

As its name indicates, an Automatically Switched Optical Network (ASON) is an “intelligent” optical network that can automatically manage the signaling and routing through the network. However, in traditional network backbone, it was rather necessary to configure cross-connections in the network elements, an optical switch for example, to create a new traffic path for a customer. ASON is an optical transport network with dynamic connection capability, and this capability is achieved by using a control plane that performs the call and connection control functions. ASON aims to automate the resource and connection management within the network.

ASON uses the Generalized MPLS (GMPLS) signaling protocol to set up and monitor edge-to-edge transport connections. Switching technologies used in ASON range from single fiber switching to wavelength switching and to optical packet switching. And the components required for the switching are optical cross connects (OXCs), wavelength converters and optical add/drop multiplexers (OADMs).

Importance of ASON in Optical Network

In an optical network which is not based on ASON technology, when it comes to the need for more bandwidth, a new connection may be required. Thus the service provider must then manually plan and configure the route in the network, which is proved to be time-consuming. Moreover, it would waste a lot of bandwidth thus to cause inevitable problems to the whole network since bandwidth is increasingly becoming a precious resource. And the optical networks in the near future bear expectations to efficiently handle resources. ASON can fulfill some of these requirements for optical networks, which are listed below:

• Fast and automatic end-to-end provisioning
• Fast and efficient re-routing
• Support of different clients, but optimized for IP
• Dynamic set up of connections
• Support of Optical Virtual Private Networks (OVPNs)
• Support of different levels of quality of service

What should be noticed is that these requirements are not restricted to optical networks but can be applied to any transport network.

Architecture of an ASON

The layered transport plane, also referred to as data plane, represents the functional resources of the network which conveys user information between location. Transfer of information are either bi-directional or unidirectional. The transport plane can also provide transfer of some control and network management information.

Basically, the logical architecture of an ASON can be divided into 3 planes: transport plane, control plane and management plane.

The transport plane contains a number of switches, and these switches can either be optical switch or other types. Which are responsible for transporting user data via connections. These switches are connected to each other via physical interface (PI).

The control plane is responsible for the actual resource and connection management within an ASN network. It consists of a series of optical connection controllers (OCC), interconnected via network to network interface (NNIs). These OCCs have the following functions:

• Network topology discovery (resource discovery)
• Signaling, routing, address assignment
• Connection set-up/tear-down
• Connection protection/restoration
• Traffic engineering
• Wavelength assignment

The management plane, on the other hand, is responsible for managing the control plane. Its responsibilities include configuration management of the control plane resources, routing areas, transport resource in control plane and policy. It also provides fault management, performance management, accounting and security management functions. The management plane contains the network management entity which is connected to an OCC in control plane via the network management interface for ASON control plane (NMI-A) and to one of the switched via network management interface for the transport network (NMI-T).

Conclusion

To sum it up, ASON can help to meet user requirements on a more realistic economical basis without resource consuming over-provisioning. Moreover, it also contributes to offering a good platform to realize a more cost-effective networking environment. I hope what presented above would help you to have a better understanding of ASON.

First published: http://www.fiber-optic-components.com/introduction-to-automatically-switched-optical-network-ason.html

Fundamentals of FTTx Network

The telecommunication industry nowadays has ushered in various new and advanced services that changed human life dramatically. With the demand for higher bandwidth consistently on the rise, an increasing number of service providers endeavored to provide a one-stop shopping service to cater to customer’s requirements. FTTx technology has proved to be viable and effective network solution.

Definition of FTTx Network

FTTx is a general term referring to describe fiber-based access networks, and the x could be H (home) if the fibers are terminated at the home of the subscriber; x could also be B (business), if the fibers are terminated at an office building. In addition to these two types, there also exist common ones like FTTC (Fiber-to-the-Curb) and FTTN (Fiber-to-the-Neighborhood).

It is generally accepted that compared to copper or digital radio, fiber features higher bandwidth and lower attenuation. FTTx technology enables users to get more extensive bandwidth and enjoy more diversified services at home by installing optical fiber all the way to subscriber. It is hence natural that FTTx technology is rather prevalent throughout the world.

Deployment Scenarios of FTTx Network

Just as what we have mentioned above, the fiber can be terminated at the user’s premises, a block of apartments or offices in a FTTx network. In some scenarios the optical fiber can be laid all the way to the subscribes’ premises such as FTTH, whereas in others, fiber optics may be terminated at either a place or node close to groups of subscribers, which depends on several factors. In this part, we will explain some common deployment scenarios.

FTTH (Fiber-to-the-Home)

In FTTH deployment, the fibers are being laid from the central office (CO) to each house or apartment. As a house or a home is usually occupied by a family, it is frequently referred to as a single dwelling unit (SDU). The following picture shows the FTTH deployment scenario.

FTTB (Fiber-to-the-Building)

Likewise, FTTB is a deployment scenario where the fiber is laid directly from the CO to an office or private apartment with multiple business tenants or homes. And the term Multiple Tenant Unit (MTU) is frequently used to those tenants or apartment units. The ONT in this scenario is often connected to an Ethernet switch that used to link all the tenants within the same building. Moreover, while in FTTB deployment, there is no need to replace the existing copper LAN cables in the building for optical fibers.

FTTC (Fiber-to-the-Curb)

In FTTC deployment scenario, however, the fiber is laid from the CO to an optical network unit (ONU) or optical network termination (ONT) that is located within 300 m from office building or home. Instead of optical fiber, in FTTC scenario we often use transmission medium such as twisted pair cable or coaxial cable to achieve connection to the subscribers.

FTTN (Fiber-to-the-Neighborhood)

FTTN is a deployment scenario where fiber from the CO is terminated at a communication switch located within 1 km from office buildings or homes. FTTN can contribute to save a significant amount of cost since one can use the existing coaxial or twisted pair infrastructure to provide the final physical connection to the end users.

FTTx Network Application

FTTx effectively and efficiently provide users triple play, which is a standard mix of traffic types known as voice,video and data. Traditional subscribers must connect to three different networks and service providers for their phone service, video broadcast and the Internet. However, once adopting FTTx, all of these types can be integrated into a single fiber network just by using different wavelengths. Hence, on the basis of triple play service, the FTTx network can thus be applied to IP telephony, video on demand (VOD), IPTV, interactive games, telepresence, video conferencing, and externally monitored home security. To this end, service providers need to offer bandwidths of 50 to 100 to enable subscribers using these services.

Conclusion

In conclusion, FTTx network is a popular tendency in current telecommunication industry since it offers a better networking experience and more convenience for subscribers. The article simply describes some rudiments of FTTx technology, for more information concerning the FTTx solution, visit Fiberstore at www.fs.com. We provide professional FTTx solutions and tutorials for your infrastructure.

First published: http://www.china-cable-suppliers.com/fundamentals-of-fttx-network.html

MEMS Optical Switch Analysis

With the increasing prevalence of the Internet and modern communications around the world, fiber optics, which signifying a significant information revolution in the telecommunication industry—are racing to keep up. The rapid growth of data transmission worldwide is driven by the existing demand for high quality Internet service. Meanwhile, software developers and users are constantly employing applications that take up more and more bandwidth in order to enhance the speed of information delivery, which, without doubt, placing heavy burdens on fiber networks. So carriers are looking for innovative ways to push more data through existing fiber.

To this end, there come various vital advancements in network communication that efficiently exploiting and extending the capacity of current fiber optic systems in significant ways, and optical switching captures an essential position among them.

What Is Optical Switching?

The backbone of telecommunications and networking today is the “all-optical network”, which means every communication would remain an optical transmission from start to finish. However, a certain amount of networking equipment today is still based on electronic signals, that is to say, the optical signals have to be converted to electrical ones, then to be amplified, regenerated or switched, and reconverted to optical signals. This process is referred to as an “optical-to-electronic-to-optical” (OEO) conversion. Which is considered to be a significant bottleneck in transmission. Therefore, huge amount of information traveling around an optical network needs to be switched through various points known as nodes.

Optical switching functions by replacing existing electronic network switched with optical ones, making no need for OEO conversions. It contributes to lower cost and physically smaller switches as well. However, optical switching technology currently is still immature, thus several ideas have been proposed as to how to implement light switching between optical fibers, among which the most common technique is that of the tiny movable mirrors known as micro-electro-mechanical systems (MEMS).

Introduction to MEMS

While the widely use of micro-electro-mechanical systems (EMES) in some other industries is nothing new, its adoption for telecom applications is relatively recent.

Conventional MEMS works by reflecting the beam of light from the surface of a tiny mirror. MEMS systems have moving parts, and the speed at which the mirror moves is limited. By applying more current, the mirror can move faster, but there's a limit to how much current can be sent into the array of mirrors. If this weren't bad enough, it seems that the speed and angular displacement terms in the calculation of the required current have integer powers of around 4 or 5, and so the bottom line is that we have to put a lot of current into the array for a small improvement in speed. By changing the mirror design so that the angle through which light is bent is smaller, it's possible to achieve faster switching speeds. This technique is known as "fast MEMS."

MEMS Switches Overview

MEMS optical switch is a micro-optical switch that made of the semiconductor material, which is generally used as movable micro-mirrors that can deflect optical signals from input to output fibers. It embraces the advantages as compact, lightweight and easy to expand. Besides, it shares the merits of both the mechanical optical switch and wave guide optical switch. Since EMES combines the electrical, mechanical and optical integration as a whole, it can apparently transmit different rates and different business services. MEMS switches feature good scalability. Two-dimensional arrays with size 32x32 are already available and can be used as basic building blocks, in single-stage architecture, to scale up to 256 ports.

Conclusion

Although MEMS still persists some drawbacks—too slow for optical burst switching or optical packet switching applications, the technique of it is under improving and progressing. Since it seems to have a monopoly on the high port-count optical switch market for the moment, a huge amount of investment is going into the implementations and into solving the basic problems.

First published: http://www.fiber-optic-solutions.com/mems-optical-switch-analysis.html

Fiber Optic Termination Overview

When installing a fiber optic network, appropriate fiber optic termination is considered to be an extremely important part since it can affect the performance and reliability of the whole network. It is hence natural that much attention should be necessarily attached to this area nowadays. Besides, an increasing number of products concerning fiber optic termination are appearing on the market to make the termination task easier and more accurate. The article will make an overview of fiber optic termination.

What Is Fiber Optic Termination

Generally speaking, fiber optic termination acts as the connection of fiber or wire to a device, the device can be something like a wall outlet or equipment that allows for connecting the cable to other cables or devices. Based on this, fiber optic termination enables fiber cross connection and light wave signal distribution. Proper fiber optic termination is able to meet the demand for protecting the fibers from dirt or damage while in use and preventing excessive loss of light as well, which also contribute to smooth and efficient performance of the network.

Preparing for Fiber Optic Termination

Before performing fiber optic termination, one should get well-prepared to ensure a smooth and successful process of termination. The preparation for fiber optic termination involves several steps: gathering the supplies you need, stripping the outer jacket, cutting the kevlar, and stripping the buffer or coating. For supplies, you’ll need safety glasses, a fiber disposal bin, connectors, fiber optic cable, epoxy and syringes (or anaerobic adhesive), and polishing film. Tools used in fiber optic termination usually include fiber stripper, scribe, aramid yarn scissors, adjustable cable jacket stripper, polishing puck, polishing glass plate, and a rubber pad to polish the PC connectors, especially for single mode termination. Besides, You’ll also need to test equipment such as a power meter, FO tracer, reference test cables, a LED light source and a microscope to view the connector.

Methods of Fiber Optic Termination

It is commonly believed that fiber optic termination is often time-consuming and highly specializes. However, due to the continuous advancement in termination technology, fiber termination systems currently demand less training and produce higher quality fiber connections in less time.

Basically, three widely adopted fiber termination methods are available to operators: pre-polished connectors, epoxy and polish fiber termination and pigtail connectors.

Pre-polished Connectors

Pre-polished connector has a short length of fiber already installed into the ferrule by the manufacturer of the connector. Moreover, the manufacturer also polished the ferrule end face thus there is no need to carry out this step on-site. The fiber to be terminated must be prepared using a specialist cleave tool and inserted into the rear of the connector where an index matching gel is often used to bridge the gap between the two fibers. The terminated fiber is held in place using some form of crimp or locking mechanism on the rear of the connector.

Epoxy and Polish Fiber Termination

This type of connector requires the application of some form of epoxy (glue) between the fiber and the connector ferrule that firmly bonds the two elements together once the epoxy has dried. There are a number of different types of epoxy available:

Heat Cured Epoxy — uses some form of “oven” to cure the epoxy, which can be selected for the optimum performance within pre-determined temperature ranges. The epoxy may either need to be injected in to the ferrule by the technician or the connectors may be supplied with the epoxy already injected by the connector manufacturer.

Ambient Temperature Epoxy— cures at room temperature without the need for any power, making it suitable for on-site terminations.

Fast Acting (Anaerobic) Adhesive — use an accelerant to speed the curing time. It can cause problems if the technician is unable to complete the insertion of the fiber into the ferrule before the epoxy cures.

Pigtail Connectors

Splice-on connectors are an alternative to either the pre-polished connector systems or the epoxy method of termination. A pigtail is a short length of 900 micron buffered fiber that has been factory terminated with a fiber optic connector. Thus it eliminates the need for any on-site termination or polishing of the connector. Splicing the end of the fiber of the pigtail to the end of the fiber of the cable, the pigtail is then attached to the cable. Fusion splicing is a preferred splicing method, where the two fibers are melted together using a high powered electric arc, forming one, single, continuous strand of glass.

Fusion splicing often requires the use of precision fiber cleaving tools and a fusion splicing machine. The fusion splice machine is used to align the two fiber end faces automatically and fuse the two together to create a very low loss joint.

Conclusion

Since fiber optic termination is an indispensable part of the optical network installation, we should always keep in mind the importance of it and get fully prepared before performing the task. Moreover, selecting a proper and efficient termination method could also help to ensure the excellent performance of the network.

First Published: http://www.fiber-optic-components.com/fiber-optic-termination-overview.html

Introduction to Optical Add-Drop Multiplexer (OADM)

There exist several different channel routing technologies in the field of optical communications. However, the evolution of single wavelength point-to-point transmission lines to wavelength division multiplexed optical networks has introduced a demand for wavelength selective optical add-drop multiplexers (OADM) to separate or route different wavelength channels. This article provides some fundamentals relevant to OADM.

What Is OADM?

Optical add-drop multiplexer (OADM) is a device used in wavelength-division multiplexing (WDM) systems. "Add" and "drop" is a capability device to add one or more new wavelength channels to an existing multi-wavelength WDM signal or to drop, which means to remove one or more channels, passing those signals to another network path. OADM can be used at different points along the optical link to insert, remove or route selected channels thus to increase the network flexibility. OADM is particularly important in metropolitan WDM light wave services where offices or sited can be connected by different add-drop channels.

A traditional OADM consists of three stages: an optical demultiplexer, an optical multiplexer, and between them a method of re-configuring the paths between the demultiplexer, the multiplexer and a set of ports for adding and dropping signals. The demultiplexer separates wavelengths in an input fiber onto ports. The reconfiguration can be achieved by a fiber patch panel or by optical switches which direct the wavelengths to the multiplexer or to drop ports. The multiplexer multiplexes the wavelength channels that are to continue on from demultiplexer ports with those from the add ports, onto a single output fiber.

The Functions of OADM

As we have mentioned above, the main function of an optical multiplexer is to couple two or more wavelengths into the same fiber. If place a demultiplexer and properly aligned it back to back with a multiplexer, there would exist two individual wavelength in the area between them. Then, this offers a chance for an enhanced function that individual wavelengths could be removed and inserted as well. The function would be called an optical wavelength drop and add demultiplexer/multiplexer—to make it briefly, optical add-drop multiplexer.

The model of an OADM is clearly shown in the picture below, where F1 signifies a filter selecting wavelength λ1 while passing through all other wavelength, and M1 signifies a multiplexer that multiplexes all wavelengths.

An even better view of OADM function is shown in the following picture. This function is often employed in WDM ring systems as well as in long-haul with drop-add features.

Types of OADM

There are two main types of OADM that can be used in WDM optical networks: fixed OADMs that are used to drop or add data signals on dedicated WDM channels, and re-configurable OADMs that have the ability to electronically alter the selected channel routing through the optical network.

The fixed optical add-drop multiplexer (FOADM) is a traditional wavelength arrangement scheme that can only input or output a single wavelength via the fixed port. FOADMs have pre-assigned channels at static nodes and allowed adding and dropping of individual or multiple wavelength channels from a DWDM.

The re-configurable optical add-drop multiplexer (ROADM), on the other hand, is a dynamic wavelength arrangement scheme, allows for dynamic wavelength arrangement scheme using a wavelength selective switch (WSS). The 8-dimensional cross-connect provided by the WSS enables quick service start-up, remote cross-connect and WDM mesh networking. The ROADM scheme can also achieve inputting/outputting a single wavelength or wavelength group via the fixed port. ROADM can add, block, pass or redirect modulated infrared (IR) and visible light beams of various wavelengths in a fiber optic network. Which featured by providing flexibility in rerouting optical streams, bypassing faulty connections, allowing minimal service disruption and the ability to adapt or upgrade the optical network to different WDM technologies.

Conclusion

To summarize, OADM plays a vital role in improving and optimizing the network performance and reliability. And it is fully compatible with both local area network (LAN) as well as long haul networks. Moreover, OADM also serves as an essential device to meet the requirement of the rapidly developed network.

First published: http://www.china-cable-suppliers.com/introduction-to-optical-add-drop-multiplexer-oadm.html

Local Area Network (LAN) Analysis

Networks can be defined as a collection of independent computers and other devices interconnected by a communication medium. A network usually consists of two or more computers that are linked in order to share resources like printers and CDs, exchange files, or allow electronic communications. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams. There exist various types of networks, including Local Area Network (LAN), Wide Area Network (WAN), Metropolitan Area Networks (MAN), Wireless LAN (WLAN), or Wireless WAN (WWAN). Among them the LAN and WAN are the most common types. This article will give a basic introduction of LAN.

What Does LAN Mean?

A local-area network (LAN) is a computer network that spans a relatively small area. It is a group of computers and associated devices that share a common communications line or wireless link to a server. Typically, a LAN encompasses computers and peripherals connected to a server within a small geographic area. Computers and other mobile devices can share resources such as a printer or network storage. Most often, a LAN is confined to a single room, building or group of buildings.

LANs can be distinguished from other networks because of their short distance. The total coverage may be from 1 km to 10 km. The data transmission speed of LANs is much higher than in other types of networks. Besides, the error rate in data transmission is slow because of the shorter distance between the equipment. Since LANs are within a single building or a smaller area, they are owned by the specific organization. This localized control provides greater flexibility in LANs than other types of networks.

Components of LAN

Each workstation of the LAN can be a microcomputer, but they are connected to a central controlling unit, through which they can exchange data, share software or hardware with other workstations of the network. Though each workstation can act independently, they are not capable of controlling the activities of other stations of the network. Then, let’s just take a look at the basic components of a LAN which are shown in the following picture.

• Communication medium: there is some kind of medium to connect all the workstations and other equipment together.
• File server: a computer dedicated to providing shared access to a main storage device.
• Print server: a computer dedicated to providing shared printing facilities.
• Gateway: a computer providing access to other networks.
• Workstation: a user’s computer or any other equipment.

Types of LAN

Based on their topology and communication media, LAN can be divided into two categories. And according to topology, LAN can take several forms but three of them can be identified as core forms. The picture below shows these three main types of LAN.

Bus—A main channel to which nodes or secondary channels are connected in a branching structure. A transmission from any computer can be received by any other computer like in the ring type. Hence there is no sufficient data security in these types.

Ring—In which each computer is connected to two neighbouring computers to form a closed circuit. Data has to pass some other computers to reach its destination.

Star—In which each computer is linked directly to a central computer and only indirectly to one another. Communication between two computers has to be done through this central controller. A particular station which wants to communicate with another station builds up a connection, through the central controlling center, with the destination. Once this connection is established data can be communicated from one to the other station.

Advantages of LAN

LAN is most often adopted for the purpose of sharing resources. Thus expensive hardware like laser printers and CD/ROM drives can be shared by several users when they are connected to a network. Further, purchasing a network version of software cuts the costs of purchasing them for each and every computer.

In addition, central control of equipment and data makes administration much more easier. When it comes to the need of changing the system, better data security and more flexibility are surely guaranteed. And instead of purchasing a multi-user system, the available equipment from different vendors can be connected together using a network.

Conclusion

Featured by its private ownership, high speed and low error rate, LANs have gained more attention as well as popularity in the field of networking. Housekeeping applications, educational services, resource sharing, and office administration are the major area in which LANs can be applied. Hope what we presented above can help you get a better understanding of LAN.

First published: http://www.fiber-optic-solutions.com/local-area-network-lan-analysis.html

Introduction to Fiber Optic Cleaving

Optical fiber has brought changes to the telecommunication industry throughout the world, therefore, it is essential for us to learn some skills necessary for working with optical fiber. It is known to all that when adopting or splicing a fiber, clean ends should be assured. And cleaving serves as one of the basic and important steps to ensure fiber ends clean and smooth, thus the significance of cleaving process cannot be underestimated. This article aims at providing some basic knowledge about cleaving and introducing common tools for cleaving.

Basics of Fiber Optic Cleaving

Fiber optic cleaving is one of the several processes in the preparation for a fiber splice operation. The purpose of cleaving is to prepare the end of the fiber so that it makes a very nearly perfect right angle with the body of the fiber and that this end face is nearly perfectly smooth. With a well-performed cleaving operation, a clean and flat endface was created perpendicular to the length of the fiber, with no protruding glass on either end. Besides it can also help to achieve a successful low loss splice of an optical fiber.

The technique of Fiber Optic Cleaving

A general strategy involved in the technique of fiber optic cleaving is known as the scribe-and-tension or scribe-and-break strategy. With the use of cutting tool made from materials such as diamond, sapphire or tungsten carbide, this process involves the introduction of a crack in the fiber, then followed by the application of tensile stress in the vicinity of the crack.

However, the specific implementations of the cleaving can be various thus lead to cleaves of different qualities. Some implementations may apply the tensile force uniformly across the cross section of the fiber while others might bend the fiber around a curved surface, causing excessive tensile stress on the outside of the bend. Besides, the crack in the fiber may also be generated in different ways: the crack may be introduced at a single point on the circumference or it may be generated all along the circumference of the fiber prior to the application of the tensile force. The circumferential introduction of the crack often allows fibers of considerably large diameters to be cleaved while maintaining high quality of the cleave.

Common Cleaving Tools

Basically, there are two kinds of cleaving tools which are commonly employed in fiber optic cleaving: pen-shaped scribe and mechanical cleaver.

Pen-shaped scribe looks like a ballpoint pen, but with a small wedge tip made of diamond or other hard material that is used to scratch the fiber manually. After scratching the fiber, the operator pulls the fiber to break it. In essence, both the scribing and breaking process are under manual control, making it more dependent on operator technique and less predictable as they require operators to exert force manually for breaking the fiber. So, an experienced operator is required to produce good cleaves.

And the other tool is mechanical cleaver, which is widely used because it can produce nicer and more repeatable cleaves. This cleaver is much easier to use thus the specific training is not essential. Just clamp the fiber in the correct position into the cleaver. Then, a force is applied and the fiber gives a nice break at the scribe.

Conclusion

Since fiber splicing requires mating two fiber ends together, any defect of the ends would impact the performance of fiber splicing. So in order to achieve good fiber optic splices or terminations, it is extremely important to cleave the fiber properly. And a good cleaver can help better finish the whole cleaving process.

First published: http://www.fiber-optic-components.com/introduction-to-fiber-optic-cleaving.html