A passive optical network (PON) is a system, that brings optical fiber cabling and signals all or most of the way to the end user. Depending on where the PON terminates, the system can be described as fiber-to-the-curb (FTTC), fiber-to-the-building (FTTB), or fiber-to-the-home (FTTH).[boxads]
A PON consists of an Optical Line Termination (OLT) at the communication company’s office and a number of Optical Network Units (ONUs) near end users. Typically, up to 64 ONUs can be connected to an OLT PON port. The passive simply describes the fact that optical transmission has no power requirements or active electronic parts once the signal is going through the network.
All PON systems have essentially the same theoretical capacity at the optical level.
Many types of PONs have been defined:
- APON ATM PON
- BPON Broadband PON
- GPON Gigabit PON
- EPON Ethernet PON
- GEPON Gigabit Ethernet PON
- CPON Composite PON
- WPON WDM PON
APON (ATM PON) is the first PON system that achieved significant commercial deployment with an electrical layer built on Asynchronous Transfer Mode (ATM).
As we know, BPON (Broadband PON) is the enhanced sub sequence of APON, with the transmission speed up to 622Mb/s. At the same time, it added the dynamic bandwidth distribution, protection and other functions. APON/BPON systems typically have downstream capacity of 155 Mbps or 622 Mbps, with the latter now the most common.
GPON / 10GPON:[bodylink]
As one of the most competitive “The Best Last Mile Solution”, GPON (Gigabit PON) is based on the TU-TG.984.x standard for the new generations of broadband passive optical access. Compared with the other PON standards, GPON provides the unprecedented high bandwidth down link rate of up to 2.5 Gbit/s, the asymmetric features better adapt to the broadband data services market. It provides the QoS full business protection, at the same time carries ATM cells and (or) GEM frame, the good service level, the ability to support QoS assurance and service access. Carrying GEM frame, TDM traffic can be mapped to the GEM frame, 8kHz using a standard frame able to support TDM services. As a carrier-grade technology standards, GPON also provides access network level protection mechanism and full OAM functions. GPON is widely deployed in FTTH networks. It can develop into two directions which is 10 GPON and WDM-PON.
EPON / 10G-EPON:
EPON (Ethernet PON) is the rival activity to GPON which uses Ethernet packets instead of ATM cells. EPON/GEPON uses 1 gigabit per second upstream and downstream rates. It is a fast Ethernet over PONs which are point to multipoint to the premises (FTTP) or FTTH architecture in which single optical fiber is used to serve multiple premises or users. EPON is an emerging broadband access technology, through a single fiber-optic access system, to access the data, voice and video service, and it has a good economy.
WDM-PON uses multiple optical wavelengths to increase the upstream and/or downstream bandwidth available to end users. WDM-PON uses wavelength division multiplexing technology to access to the passive optical network. It has four programs as following:[bodyads]
- 1. Each ONU is assigned with a pair of wavelength, for uplink and downlink transmission, thereby providing the OLT to each ONU fixed virtual point-to-point bidirectional connections.
- 2. ONU uses tunable lasers, according to the needs of the ONU to dynamically allocate the wavelength, and each ONU can be shared the wavelength, the network are reconfigurable.
- 3. Using colorless ONUs, the ONU are independent from the wavelength.
- 4. Using a combination of TDM and WDM technology, Composite PON (CPON). CPON uses WDM technology in the downstream, and TDMA technology in the upstream.