The gigabit passive optical network (GPON) is an outcome of the full service access network (FSAN) alliance and is specified in the ITU-T G.984.x series of recommendations, which were finalized in February 2004. GPON extends the capabilities of its two predecessors, asynchronous transfer mode (ATM) PON, also known as APON, and broadband PON (BPON). Compared with its predecessors, GPON provides larger splitting ratios, higher up- and downstream data rates, longer reach, improved privacy and security through the use of the Advanced Encryption Standard (AES) algorithm, and a new GPON encapsulation method (GEM) to carry synchronous voice services and data services such as Ethernet in a bandwidth-efficient manner (Shumate [2008]). These extended capabilities of GPON are explained in greater detail in the following.

Architecture

Figure 3.1 shows the architecture of a GPON network (Effenberger et al. [2007]). GPON deploys two different wavelength channels for upstream and downstream communication. The upstream and downstream wavelength channels operate at 1310 nm and 1490 nm, respectively. Several upstream and downstream data rates are specified for GPON, with a maximum data rate of 1.244 Gb/s in the upstream direction and 2.488 Gb/s in the downstream direction. The reach of a GPON network can be as high as 60 km, whereby the differential reach between optical network units (ONUs) must not exceed 20 km. The ITU-T recommendations for GPON allow for a splitting ratio of up to 128.