More and more feature-rich services are being created, and people's
expectations for quality of experience (QoE) are increasing. The
predominant broadband access solutions deployed today are the digital
subscriber line (DSL) and community antenna television (CATV) / (cable
TV) based networks. However, both of these technologies have limitations
because they are based on infrastructure that was originally built for
carrying voice and analog TV signals, respectively; but their
retrofitted versions to carry data are not optimal. Currently deployed
blends of asymmetric DSL (ADSL) technologies provide 1.5Mb/s of
downstream bandwidth and 128kbits/s of upstream bandwidth at best.
Although variations of DSL such as very-high-bit-rate DSL (VDSL), which
can support up to 50Mb/s of downstream bandwidth, these technologies
have much more severe distance limitations. Passive optical networks
(PONs) have evolved to provide much higher bandwidth in the access
network. It is a point-to-multipoint, fiber to the premises network
architecture in which unpowered optical splitters are used to enable a
single optical fiber to serve multiple premises.