gh as 100 Mbits/s, both plastic core and PCS are used with LEDs in a LAN environment. We can note the general operational characteristics of multimode and single-mode fiber by examining their general level of attenuation, oper- ating rate, and bandwidth, as well as the general environment in which they are used. Thus, let's do SO. Today multimode fiber is used primarily in a LAN environment. This is because such fiber has an attenuation level between -3 and 1 dB/km, which is relatively high in comparison to that of single-mode fiber. The bandwidth capability of multimode fiber is between 160 and 500 MHz/km, which permits a data transmission rate of approximately 25 to 50 percent that of Gigabit Ethernet to be supported at a distance of one kilometer. This explains why, when multimode fiber is used in that LAN environment, the transmission distance is significantly less than 1 km. Although both lasers and LEDs can be used with multimode fiber in a LAN environment, less costly LEDs are used. When LEDs are used, a light source of 850 nm is employed, while the use of lasers results in a light source with a wavelength of 1300 nm. In comparison to multimode fiber, single mode has an attenuation rate a fraction of multimode. The attenuation rate of single-mode fiber Chapter Three is between - -0.35 and 0.20 dB/100 km, which makes it more suitable for use in a carrier's backbone infrastructure Lasers operating at 1310 or 1550 nm are commonly used with single-mode fiber, enabling band- width of up to 10 GHz/100 km to be obtained today, which is expected to increase to 40 GHz/100 km in a few years. Table 3.2 compares the pri- mary operational characteristics and utilization of multimode and sin- gle-mode fiber. Types of Cable Today there are literally hundreds to thousands of different types of fiber-optic cables. Some cables contain hundreds of fibers, while other cables may contain a single fiber or two, four, or more pairs of fibers. The popularity of cable with two or more fibers dates to the early use of fiber optics.