Hi Ankita,
A PON system utilizes a passive splitter that takes one input and splits it to “broadcast” signals downstream to many users. This reduces the cost of the system substantially by sharing one set of electronics and an expensive laser with up to 32 homes. Upstream, the passive splitter acts as a combiner to connect all users to the same shared PON port. An inexpensive laser is used for the home to send signals back to the FTTH system in the central office.
Different technologies of GPON are:
BPON, or broadband PON, was the most popular PON application in the beginning. BPON uses ATM as the protocol. ATM is widely used for telephone networks and the methods of transporting all data types (voice, Internet, video, etc.) are well known. BPON digital signals operate at ATM rates of 155, 622 and 1244 Mb/s.
Downstream digital signals from the CO through the splitter to the home are sent at 1490 nm. This signal carries both voice and data to the home. Video on the first systems used the same technology as CATV, an analog modulated signal, broadcast separately using a 1550 nm laser which may require a fiber amplifier to provide enough signal strength to overcome the loss of the optical splitter. Video could be upgraded to digital using IPTV, negating the need for the separate wavelength for video. Upstream digital signals for voice and data are sent back to the CO from the home using an inexpensive 1310 nm laser. WDM couplers separate the signals at both the home and the CO.
Thanks,