Telecom | FTTH, PON, GPON

FTTH, PON, GPON

FTTH

Fibre communication for providing broadband services were being populated now a days. The optical fibre cable are being used for the last mile communication in telecommunication. 

Earlier the fibre optics were connected to BTS level (The Base Transceiver Station) or cluster towers and then through RADIO the signal is being transmitted. But presently technology gave the connectivity up to individual residential/ home level. So that a public individual can avail high speed data or voice service at home with affordable cost. FTTH (Fibre to the Home) is the technology for connecting the high speed fibre optic cables to the home/ building/ business points. The prime benefit of using fibre is achieving higher speeds over longer distances which in turn is very useful in streaming videos. 

Multiple methods of fibre connectivity is called FTTX. Several other terms used such as;

• FTTP: Fibre to the premises
• FTTH: Fibre to the Home
• FTTO: Fibre to the office
• FTTB: Fibre to the Building
• FTTT: Fibre to the terminal
• FTTA: Fibre to the amplifier
• FTTR: Fibre to the radio

Within FTTH architecture two types of technology used known as Active optical network (AON) and Passive optical network (PON).

AON

Active Optical Networks can be referred to as point-to-point network. In AON switching equipment like routers, switches and other devices which are electrically powered for managing signal distribution and transmitting direct signals to the receivers or subscribers. For AON a dedicated fibre connection may be used and as the active equipment’s were used the electricity cost may rise. Active optical devices include light sources (lasers), optical receivers, optical transceiver modules, optical amplifiers (fiber amplifiers and semiconductor optical amplifiers), etc.

PON

Passive Optical Network can be referred to as point-to-multipoint network and it does not have any electrically powered switching equipment. PON makes use of fiber optic splitters for directing traffic signals of different wavelengths. The optical splitters used in PON can separate and collect optical signals as they are transmitted through the network. PON networks can direct signals to 16, 32 and 64 customers at a time. A passive optical network includes an optical line terminal (OLT) and a set of supporting optical network units (ONUs) installed at the user end. The optical distribution network (ODN) between the OLT and the ONU contains optical fibers and passive splitters or couplers. 

Again PON is technically classified into three standards: APON (ATM PON) based on ATM, EPON (Ethernet PON) based on Ethernet, and GPON (Gigabit PON) based on General Frame Protocol.

Here lets know something about the advanced standard GPON or Gigabit PON. 

GPON

GPON is a point-to-multi point access technology and supports all types of ethernet protocols. The prime feature of GPON is the use of passive splitters in the fibre distribution network, enabling one single feeding fibre from the provider’s central office to serve multiple homes and small businesses. For security reason, GPON uses AES (Advanced Encryption Standard).

GPON network consists of mostly two active transmission equipment such as Optical Line Termination (OLT) and Optical Network Unit (ONU) or Optical Network Termination (ONT).

Due to the maximum use of internet and broadband services, GPON supports in following functions

• Longer Transmission distance
• Higher Bandwidth
• Better user experience
• Low cost with higher resource use

How it works

The primary optical transmitter, called as OLT (Optical Line Terminal) is located within the telecommunications operator building, the central office. A laser in the OLT injects the photons from the central office to a fibre-optic cable that ends at a passive optical splitter. The splitter breaks the single signal from the central office into several signals that may ultimately be distributed up to 64 customers. The OLT is connected to the optical splitter through a single optical fiber, and the optical splitter is then connected to ONU Different wavelengths are adopted in the upstream and downstream directions for transmitting data. 

During downstream transmission all data is broadcast to all ONUs from the OLT and during the upstream direction, each ONU can send data to the OLT only in the timeslot permitted and allocated by the OLT.

-DR