One method of stripping the desired wavelengths from the unwanted ones involves Bragg grating (see diagram). Bragg grating can be thought of as small lines etched across the core of the fiber. With the lines etched at specific distances from one another, wavelengths of light can be reflected back toward the input. A blazed grating is also etched into the core at an angle that reflects the light coming back on the grating out of the core and onto a receiver. By placing several combinations of Bragg and blazed gratings in a fiber, you can separate all the wavelengths out to waiting receivers.
Care and Feeding
Data would never get from Point A to Point B without the fiber itself. Fiber-optic cable comes in a variety of lengths with different connector types. Connectors are probably the most difficult part of the fiber-optic setup. That's because the names of the various connectors--FC, SC, LC, ST and MT--can be confusing, and remembering which one is which can be difficult. Most people remember connector types by giving them names that reflect how they work: FC (finger cramp, because fingers are easily cramped while trying to screw the connector tight); SC (stab click--the connector is stabbed into the socket until it clicks); LC (little click--a smaller version of SC); ST (stab twist--the connector is stabbed into the socket and then turned about a quarter turn to lock); and MT (mighty tiny--the smallest of the connectors). For more on connector types, see workshop, "10 GIG Can't Wait to Interoperate").
While today's fiber is more resilient than its predecessors, care should still be taken when handling it. Fiber should never be tightly bent or curved, and though you're used to walking on the copper pairs strewn around your computer room, fiber-optic cable should be treated like glass--don't step on it. Any change in the diameter of the core can cause great changes in dispersion, resulting in the fiber losing its transmission qualities.
The fiber-optic speeds are incredible. With today's fiber systems, you can transmit the entire contents of a CD-ROM in about one half of a second. And the technology is not standing still. The Optical Internetworking Forum is working to complete the interface standards for OC-768, which will increase bandwidth to 40 Gbps. That's the entire content of eight CD-ROMs, or 5 GB of data, transmitted every second.
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