Index An f or a t following a page number denotes a figure or a table, respectively. A1 and A2 bytes (SONET), 381, 382t AAL-1 adaptation layer, 805­806 AAL-5 adaptation layer, 805­806 absorption. See material absorption absorption of photons, 157, 165 acceptance angle, 54 access networks, 629­650 architecture, 631­636, 632f enhanced HFC systems, 636­638 fiber to the curb (FTTC), 638­639 PON evaluation, 648­649 add/drop multiplexers (ADMs), 20 carrier backbone networks, 709, 710f for ring interconnection, 530­532, 531f in SONET infrastructure, 387­388 admission control, 801, 806­807 ADMs. See add/drop multiplexers (ADMs); optical add/drop multiplexers AF (assured forwarding), 415 AGC. See automatic gain control agents, element management systems