Manufacturers design fiber-optic cables for specific applications. For example, is the cable buried underground or hung from telephone poles? Is the cable snaked through cableways, submerged in water, or just laid on the ground? Is the cable used in industrial, telecommunication, utility, or military applications? Each type of application may require a slightly different cable design.
Agreement on standard cable designs is difficult. Cable design choices include jacket materials, water- optic cables. Some fiber-optic cables are used in commercial applications, and others are used in military applications. Standard commercial cable designs will develop over time as fiber-optic technology becomes more established.
A fiber-optic data link sends input data through fiber-optic components and provides this data as output information. It has the following three basic functions:
To convert an electrical input signal to an optical signal
To send the optical signal over an optical fiber
To convert the optical signal back to an electrical signal
A fiber-optic data link consists of three parts: transmitter, optical fiber, and receiver. Figure 6-8 is an illustration of a fiber-optic data-link connection. The transmitter, optical fiber, and receiver perform the basic functions of the fiber-optic data link. Each part of the data link is responsible for the successful transfer of the data signal. A fiber-optic data link needs a transmitter that can effectively convert an electrical input signal to an optical signal and launch the data-containing light down the optical fiber. Also, fiber-optic data link needs a receiver that can effectively transform this optical signal back into its original form. This means that the electrical signal provided as data output should exactly match the electrical signal provided as data input.
A fiber-optic splice is a permanent fiber joint whose purpose is to establish an optical connection between two individual optical fibers. System design may require that fiber connections have specific optical properties (low loss) that are met only by fiber splicing. Also, fiber-optic splices permit the repair of optical fibers damaged during installation, accident, or stress. System designers generally require fiber splicing whenever repeated connection or disconnection is unnecessary or unwanted.
Mechanical and fusion splicing are two broad categories that describe the techniques used for fiber splicing. A
mechanical splice is a fiber splice where mechanical fixtures and materials perform fiber alignment and connection. A fusion splice is a fiber splice where localized heat fuses or melts the ends of two optical fibers together. Each splicing technique seeks to optimize splice performance and reduce splice loss. Low-loss fiber splicing results from proper fiber end preparation and alignment.
A fiber-optic connector is a device that permits the coupling of optical power between two optical fibers or two groups of fibers. Designing a device that allows for repeated fiber coupling without significant loss of light is difficult. Fiber-optic connectors must maintain fiber alignment and provide repeatable loss measurements during numerous connections. Fiber-optic connectors should be easy to assemble (in a laboratory or field environment) and should be cost effective. Also, they should be reliable. Fiber-optic connections using connectors should be insensitive to environmental conditions, such as temperature, dust, and moisture. Fiber-optic connector designs attempt to optimize connector performance by meeting each of these conditions.
Figure 6-8. - Parts of a fiber-optic data link.Continue Reading