A passive optical network (PON) is a telecommunications network that uses point-to-multipoint fiber to the end-points in which unpowered optical splitters are used to enable a single optical fiber to serve multiple end-points. A PON consists of an optical line terminal (OLT) at the service provider's central office and a number of optical network units(ONUs) or Optical Network Terminals (ONTs), near end users. A PON reduces the amount of fiber and central office equipment required compared with point-to-point architectures. A passive optical network is a form of fiber-optic access network. In most cases, downstream signals are broadcast to all premises sharing multiple fibers. Encryption can prevent eavesdropping. Upstream signals are combined using a multiple access protocol, usually time division multiple access (TDMA).