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FIBER OPTIC CABLES

2008-01-28T17:00:00.000-08:00

FIBER OPTIC CABLE.

Multimode fiber

The propagation of light through a multi-mode optical fiber.Fiber with large (greater than 10 μm) core diameter may be analyzed by geometric optics. Such fiber is called multimode fiber, from the electromagnetic analysis (see below). In a step-index multimode fiber, rays of light are guided along the fiber core by total internal reflection. Rays that meet the core-cladding boundary at a high angle (measured relative to a line normal to the boundary), greater than the critical angle for this boundary, are completely reflected. The critical angle (minimum angle for total internal reflection) is determined by the difference in index of refraction between the core and cladding materials. Rays that meet the boundary at a low angle are refracted from the core into the cladding, and do not convey light and hence information along the fiber. The critical angle determines the acceptance angle of the fiber, often reported as a numerical aperture. A high numerical aperture allows light to propagate down the fiber in rays both close to the axis and at various angles, allowing efficient coupling of light into the fiber. However, this high numerical aperture increases the amount of dispersion as rays at different angles have different path lengths and therefore take different times to traverse the fiber. A low numerical aperture may therefore be desirable.

FOC

An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length. Fiber optics is the overlap of applied science and engineering concerned with the design and application of optical fibers. Optical fibers are widely used in fiber-optic communication, which permits transmission over longer distances and at higher data rates than other forms of communications. Fibers are used instead of metal wires because signals travel along them with less loss, and they are immune to electromagnetic interference. Optical fibers are also used to form sensors, and in a variety of other applications.

Light is kept in the "core" of the optical fiber by total internal reflection. This causes the fiber to act as a waveguide. Fibers which support many propagation paths or transverse modes are called multimode fibers (MMF). Fibers which support only a single mode are called singlemode fibers (SMF). Multimode fibers generally have a large-diameter core, and are used for short-distance communication links or for applications where high power must be transmitted. Singlemode fibers are used for most communication links longer than 200 meters.

Joining lengths of optical fiber is more complex than joining electrical wire or cable. The ends of the fibers must be carefully cleaved, and then spliced together either mechanically or by fusing them together with an electric arc. Special connectors are used to make removable connections.

Special-purpose fiber

Some special-purpose optical fiber is constructed with a non-cylindrical core and/or cladding layer, usually with an elliptical or rectangular cross-section. These include polarization-maintaining fiber and fiber designed to suppress whispering gallery mode propagation.

Photonic crystal fiber is made with a regular pattern of index variation (often in the form of cylindrical holes that run along the length of the fiber). Such fiber uses diffraction effects instead of or in addition to total internal reflection, to confine light to the fiber's core. The properties of the fiber can be tailored to a wide variety of applications.

Singlemodefiber

A typical single-mode optical fiber, showing diameters of the component layers.Fiber with a core diameter less than about ten times the wavelength of the propagating light cannot be modeled using geometric optics. Instead, it must be analyzed as an electromagnetic structure, by solution of Maxwell's equations as reduced to the electromagnetic wave equation. The electromagnetic analysis may also be required to understand behaviors such as speckle that occur when coherent light propagates in multi-mode fiber. As an optical waveguide, the fiber supports one or more confined transverse modes by which light can propagate along the fiber. Fiber supporting only one mode is called single-mode or mono-mode fiber. The behavior of larger-core multimode fiber can also be modeled using the wave equation, which shows that such fiber supports more than one mode of propagation (hence the name). The results of such modeling of multi-mode fiber approximately agree with the predictions of geometric optics, if the fiber core is large enough to support more than a few modes.

• SPEED: Fiber optic networks operate at high speeds - up into the gigabits
• BANDWIDTH: large carrying capacity
• DISTANCE: Signals can be transmitted further without needing to be "refreshed" or strengthened.
• RESISTANCE: Greater resistance to electromagnetic noise such as radios, motors or other nearby cables.
• MAINTENANCE: Fiber optic cables costs much less to maintain.

HEBREW 13:5

Keep your lives free from the love of money and be content with what you have, because God has said,
"Never will I leave you;
never will I forsake you."

Assignment lng dW

2008-01-18T17:56:00.000-08:00

Ability to focus the resources

Focusing IT staff, money, and technology resources on key priorities of the company is essential to achieving success. The technology resources must be focused on initiatives that are in sync with company needs and objectives, and they must deliver in a productive, cost-effective manner. Career-minded people at any level understand the need for strong focus.

Resources are a strategic business-consulting firm that has commercialization as its middle name. You know your product, technology, or service. We know business.

Focus is our strategy and our purpose. We work with new, early stage and established businesses on ensuring that the business operations – processes, activities, and infrastructure – are appropriate and adequate to support the financial performance and strategic objectives of our clients.

Everything a business does and doesn’t do is reflected in the financial performance – the bottom-line. It isn’t enough to grow revenues. You must also be able to grow profits and generate cash. How you generate financial results is a measure of your…

Imagine that success is like gaining entrance to a vault of riches with three locks to open. Now these locks aren't like the usual padlocks, door locks, or other real life, tangible mechanisms opened with traditional keys (or brute force). These locks are more like those portrayed in the science fiction adventures. You know the ones that require solving a riddle, navigating narrow ledges with chasms and torment all around, and then finding the combination of symbols on tiles or buttons to maneuver. Solve the puzzle, make the right moves, and Voila! You are there! The treasure is yours. Of course, on the way out you have the challenge of keeping it away from bandits and opportunists (and the part they never show the tax man), but that is the subject of another story.

Ability to build the team

Teamwork is essential for competing in today's global arena, where individual perfection is not as desirable as a high level of collective performance. In knowledge-based enterprises, teams are the norm rather than the exception. A critical feature of this team is that they have a significant degree of empowerment, or decision-making authority. There are many different kinds of teams: top management teams, focused task forces, self-directed teams, concurrent engineering teams, product/service development and/or launch teams, quality improvement teams, and so on.

The quality of your work is a measure of the quality of yourself. We all derive pride and self-esteem from accomplishing tasks in an excellent fashion. Successful completion of a worthy task means that it was not only attempted, but it was completed to certain standards of performance or better. Worthy means it was something that needed doing whether it was typing of a document or diagnosis of an illness. It was a task that somebody had to do and do correctly.

High levels of remuneration and job security are dependent upon three keys; what you do, how well you do it and how difficult it is to replace you. Accordingly, our highly competitive employment market only pays superior rewards to recipients who render worthy superior performances.

Your goal at work should therefore be to get good, get better and to be the best possible, to such a point where you seemingly become indispensable to the organisation. Here are ten concepts to help you improve your levels of quality and excellence at work:

Organisations that are continually productive and profitable incessantly strive for quality and excellence. Acknowledging that your customers are not prepared to accept an attitude of "that's good enough," how does your organisation's quality standards rate as against its competitors? How do your own personal levels of excellence and quality rate against your current and potential competitors in the employment market? If you don't know the answer/s to these questions, then resolve to find them out immediately. The longer you delay, the larger the gap may be growing between you and your competition!

Assignment

2007-11-22T22:29:00.000-08:00

What is the difference between CSMA/CD and CSMA/CA?

The flaw in the IEEE 802.11 MAC is CSMA/CA, (Carrier Sense Multiple Access with Collision Avoidance). CSMA/CA operates on the principles of the ALOHA system developed by Abramsom (1973,1977) and others at the University of Hawaii. The ALOHA system has been studied and proven to have a maximum throughput of only about 33% of the available bandwidth. Further, the ALOHA system and CSMA/CA protocols are inherently unstable. That is, as the amount of network traffic increases, the actual throughput may be far below the theoretical 33% maximum.
CSMA/CD is a highly efficient, stable improvement over CSMA/CA. The main difference between CSMA/CD and CSMA/CA is collision detection. Devices on a wired network can detect when their transmissions collide with other devices. Unfortunately, devices on a wireless network, due to radio frequency transmission power issues, can not detect when their transmissions collide with other devices. Therefore, as attractive as CSMA/CD is, it simply can't be used in wireless networks.

What is IP address?
An identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination. The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, 1.160.10.240 could be an IP address.
Within an isolated network, you can assign IP addresses at random as long as each one is unique. However, connecting a private network to the Internet requires using registered IP addresses (called Internet addresses) to avoid duplicates.
The four numbers in an IP address are used in different ways to identify a particular network and a host on that network. Four regional Internet registries -- ARIN, RIPE NCC, LACNIC and APNIC -- assign Internet addresses from the following three classes.
Class A - supports 16 million hosts on each of 126 networks
Class B - supports 65,000 hosts on each of 16,000 networks
Class C - supports 254 hosts on each of 2 million networks
The number of unassigned Internet addresses is running out, so a new classless scheme called CIDR is gradually replacing the system based on classes A, B, and C and is tied to adoption of IPv6.

What is Media Address Control?

In computer networking a Media Access Control address (MAC address) or Ethernet Hardware Address (EHA) or hardware address or adapter address is a quasi-unique identifier attached to most network adapters (NICs). It is a number that acts like a name for a particular network adapter, so, for example, the network cards (or built-in network adapters) in two different computers will have different names, or MAC addresses, as would an Ethernet adapter and a wireless adapter in the same computer, and as would multiple network cards in a router. However, it is possible to change the MAC address on most of today's hardware, often referred to as MAC spoofing.
Most layer 2 network protocols use one of three numbering spaces managed by the IEEE: MAC-48, EUI-48, and EUI-64, which are designed to be globally unique. Not all communications protocols use MAC addresses, and not all protocols require globally unique identifiers. The IEEE claims trademarks on the names "EUI-48" and "EUI-64". (The "EUI" stands for Extended Unique Identifier .)
MAC addresses, unlike IP addresses and IPX addresses, are not divided into "host" and "network" portions. Therefore, a host cannot determine from the MAC address of another host whether that host is on the same layer 2 network segment as the sending host or a network segment bridged to that network segment.
ARP is commonly used to convert from addresses in a layer 3 protocol such as Internet Protocol (IP) to the layer 2 MAC address. On broadcast networks, such as Ethernet, the MAC address allows each host to be uniquely identified and allows frames to be marked for specific hosts. It thus forms the basis of most of the layer 2 networking upon which higher OSI Layer protocols are built to produce complex, functioning networks.

Difference between client and server?

The client drops all references to an object, after which the ORB local to the client then can clean up all of its data structures related to that object, and
The server can decide that the object needs to be destroyed, and it then does the job of deactivating the object (so that the POA can know not to answer any more queries to that object) and freeing associated resources, etc.