The Design of Fiber Core and Cladding

An optical fiber consists of two different types of highly pure, solid glass, composed to form the core and cladding. A protective acrylate coating (see Figure 1) then surrounds the cladding. In most cases, the protective coating is a dual layer composition.

A protective coating is applied to the glass fiber as the final step in the manufacturing process. This coating protects the glass from dust and scratches that can affect fiber strength. This protective coating can be comprised of two layers: a soft inner layer that cushions the fiber and allows the coating to be stripped from the glass mechanically and a harder outer layer that protects the fiber during handling, particularly the cabling, installation, and termination processes.

Single-Mode and Multimode Fibers
There are two general categories of optical fiber: single-mode and multimode (see Figure 2).

Single Mode cable is a single stand of glass fiber with a diameter of 8.3 to 10 microns that has one mode of transmission. Single Mode Fiber with a relatively narrow diameter, through which only one mode will propagate typically 1310 or 1550nm. Carries higher bandwidth than multimode fiber, but requires a light source with a narrow spectral width. Synonyms mono-mode optical fiber, single-mode fiber, single-mode optical waveguide, unimode fiber.

Single-mode fiber gives you a higher transmission rate and up to 50 times more distance than multimode, but it also costs more. Single-mode fiber has a much smaller core than multimode. The small core and single light-wave virtually eliminate any distortion that could result from overlapping light pulses, providing the least signal attenuation and the highest transmission speeds of any fiber cable type.

Single-mode optical fiber is an optical fiber in which only the lowest order bound mode can propagate at the wavelength of interest typically 1300 to 1320nm.

In most fiber optic systems, optical fiber and waveguides are coupled to and from bulk optical devices, creating hybrid optical devices. In this tutorial article, the authors explain in detail how to successfully collimate, focus, and align hybrid optics, including polarizing and polarization maintaining optics.

Glossary
Mode field diameter (MFD): A measure of the intensity profile of light traveling within a fiber. In Gaussian optics, this diameter is measured at the point where the light intensity drops to 13.5% (1/e2) of the peak intensity. In single-mode fibers, it is typically about 15% larger than the actual core size.

Numerical Aperture (NA): A measure of the maximum angle at which a given optical system can receive light. If a system can receive light within a cone having a half angle q, then the NA of that system is equal to sin q.

SECURITY TIPS

• lock your device with a password. If possible use a “strong alphanumeric” password that utilizes a combination of upper and lower case letters, and special symbols (see below for Dell Axim).
• try not to put too much private information on your device, e.g. credit card numbers, social security numbers, passwords to this kind of information.
• if you do need to put passwords and usernames for various accounts on your device, consider using password management software in addition to locking your device. Recommended software includes: RoboForm http://www.roboform.com/ or SplashID http://www.splashdata.com/splashid/
• turn off your wireless when you’re not using it, especially Bluetooth. Bluetooth is used to set up short-range networks – connecting multiple devices like PDAs, laptops, cell phones, etc. with one another. Leaving it on in public places could allow unscrupulous users to access your data on your mobile device.

PASSWORD PROTECTING THE DELL AXIM

Windows Mobile is Microsoft’s embedded operating system for battery-operated mobile devices including smartphones, PDAs, enterprise mobile computers (handheld scanners), and many other device types. While much of its OS core is shared with Windows Embedded CE (previously called Windows CE), Microsoft has added a common shell, UI enhancements, better phone features and a common application interface.

A large number of OEMs building very different devices choose Windows Mobile for its strong enterprise integration (Microsoft Exchange server for email), legendary flexibility, huge application developer ecosystem, streamlined SDK for developing apps, and the support that Microsoft provides for development, marketing and sales. These attributes have given Windows Mobile strong growth over the last four years, with several OEMs making devices that sold well over a million units.

Reinstall your operating system
If the previous step failed to clean your computer, the most effective option is to wipe or format the hard drive and reinstall the operating system. Although this corrective action will also result in the loss of all your programs and files, it is the only way to ensure your computer is free from backdoors and intruder modifications.

Many computer vendors also offer a rescue partition or disc(s) that will do a factory restore of the system. Check your computer’s user manual to find out whether one of these is provided and how to run it.

Before conducting the reinstall, make a note of all your programs and settings so that you can return your computer to its original condition.
It is vital that you also reinstall your antivirus software and apply any patches that may be available. Consult “Before You Connect a New Computer to the Internet” for further assistance.