Brief Introduction of PON

WDM Optical Network

What is Passive Optical Networks

A PON is a fiber network that only uses fiber and passive components like splitters and combiners rather than active components like amplifiers, repeaters, or shaping circuits. Such networks cost significantly less than those using active components. The main disadvantage is a shorter range of coverage limited by signal strength. While an active optical network (AON) can cover a range to about 100 km (62 miles), a PON is typically limited to fiber cable runs of up to 20 km (12 miles). PONs also are called fiber to the home (FTTH) networks.

FTTx - Fiber to the x

The term FTTx is used to state how far a fiber run is. FTTx deployments cover varying amounts of that last distance.

  • FTTH for fiber to the home
  • FTTB for fiber to the building
  • FTTC for fiber to the curb or fiber to the cabinet
  • FTTN for fiber to the node or fiber to the neighbourhood
  • FTTP for fiber to the premises

The typical PON arrangement is a point to multi-point (P2MP) network where a central optical line terminal (OLT) at the service provider’s facility distributes TV or Internet service to as many as 16 to 128 customers per fiber line (see the figure). Optical splitters, passive optical devices that divide a single optical signal into multiple equal but lower-power signals, distribute the signals to users.

In the basic method of operation for downstream distribution on one wavelength of light from OLT to ONU/ONT, all customers receive the same data. The ONU recognizes data targeted at each user. For the upstream from ONU to OLT, a time division multiplex (TDM) technique is used where each user is assigned a timeslot on a different wavelength of light. With this arrangement, the splitters act as power combiners. The upstream transmissions, called burst-mode operations, occur at random as a user needs to send data. The system assigns a slot as needed. Because the TDM method involves multiple users on a single transmission, the upstream data rate is always slower than the downstream rate.

PON is the acronym for Passive Optical Network is a point-to multipoint network. A PON consists of optical line terminal at the service provider’s central office and many number of optical network units near end users. The goal of PON is to reduce the amount of fiber.

There are two standards of PON:

  • GPON
  • EPON or GEPON

GPON (Gigabit PON) is the evolution of broadband PON (BPON) standard. The protocols used by GPON are ATM, GEM, and Ethernet. It supports higher rates and has more security. GPON uses optical wavelength division multiplexing (WDM) so a single fiber can be used for both downstream and upstream data. A laser on a wavelength (λ) of 1490 nm transmits downstream data. Upstream data transmits on a wavelength of 1310 nm. If TV is being distributed, a wavelength of 1550 nm is used.

EPON or GEPON (Ethernet PON) is the IEEE standard that uses Ethernet for sending data packets. Based on the Ethernet standard 802.3, EPON 802.3ah specifies a similar passive network with a range of up to 20 km. It uses WDM with the same optical frequencies as GPON and TDMA. The raw line data rate is 1.25 Gbits/s in both the downstream and upstream directions. You will sometimes hear the network referred to as Gigabit Ethernet PON or GEPON.

GPON ONT and EPON ONU Solution

Current and future demands for Internet access bandwidth have led to extensive deployment of FTTH technologies. Of these technologies, GPON and EPON provides the flexibility and cost advantages that service providers need to deliver services profitably to their subscribers. To support the increasing deployment of GPON and EPON in access networks worldwide, Fiberstore has developed full-featured ONT/ONU devices that can deliver a range of services. ONT is located at the customer premise, and ONU is located outside the home. EPON ONU can be working in different temperature and weather conditions. GPON ONT connects the PON to TV sets, telephones, computers, or a wireless router. More information about GPON ONT equipment please visit the fiberstore official website.