T-II- these are keyed and spring-loaded, push-in and twist-type connectors Understanding Optical Fiber where P1 is the power measured before insertion of a connector and P2 is that measured after insertion. SMA connectors, which represent the first generation of connection products, have insertion losses ranging from 0.60 to 0.80 dB. The second generation of connectors, represented by biconic and ST types, have an insertion loss of approximately 0.50 dB. Third-generation connectors, such as the LC and SC, have an insertion loss as low as 0.20 dB. The EIA/TIA 568 Standard The performance requirements for installed optical fiber within a building were addressed by the Electronic Industry Association (EIA) and the Telecommunications Industry Association (TIA) in a joint publi- cation, the EIA/TIA-568-B.1 Commercial Building Telecommunications Cabling Standard. This standard defines both the maximum level of opti- cal attenuation and the maximum transmission distance for horizontal, backbone, and centralized optical fiber cabling connections. As noted earlier, optical attenuation represents a reduction in light power or intensity as it flows through a cable, cable connections, and splices. Thus, optical attenuation represents insertion loss on an end-to-end basis. The actual attenuation permitted under the EIA/TIA 568-B.1 specifi- cation depends on several factors, such as the type of fiber used, the number of connections used to mate one fiber to another, the number of splices, the optical wavelength of the transmitter, the cable length and whether cabling is horizontal, backbone, or centralized. Horizontal cabling represents the cabling between the telecommunications outlet in a work area and the horizontal cross-connect. In comparison, backbone cabling represents cabling between telecommunications rooms, while central- ized cabling represents cabling from a work area to a centralized cross- connect via the use of pull-through cables, a splice, or an interconnect in a telecommunications room. Table 3.4 summarizes E