2016年5月10日星期二

Brief Introduction of FTTH



FTTx has been regarded as the most promising broadband access method after DSL. Different from DSL, FTTx has higher operating frequency, larger capability, smaller attenuation, anti – EMI, stronger anti-electromagnetic pulse capability, and better confidentiality.

FTTx is composed of several access forms, like FTTP (Fiber To The Premise), FTTB (Fiber To The Building), FTTC (Fiber To The Curb), FTTN (Fiber To The Neighborhood), FTTZ(Fiber To The Zone), FTTO (Fiber To The Office), FTTH (Fiber To The Home), and so on.




FTTH Is the Best Choice of Fiber Directly to the Home

To many homes, FTTH is the best choice that can link fiber and ONU (optical network unit) directly with houses. In addition to FTTD (Fiber To The Desk), it is the access method closest to users. With the formal generalization of fiber broadband access, it should be explained that FTTH broadband access is not only referred to fiber to the home, but also comprised of FTTO, FTTD and FTTN.

Moreover, the access plan -- 100Mbps into zone or building, 1-10Mbps to home -- is achieved by fiber + twisted pairs. FTTx + LAN is shared among many homes, which may not ensure the wideband bandwidth and network speed, while FTTH enables single home to enjoy broadband exclusively.

FTTH Technical Standard

At present, ADSL2+ and FTTH supporting exclusive broadband have become the main stream of future development. As for FTTH technology, besides APON (ATMPON), there are two standards competing: GPON (GigabitPON) set by ITU/FSAN, and EPON (Ethernet) set by IEEE802.3ah.

Based on ITU-TG.984.x, GPON is an integrated access standard for the new generation of broadband passive optical, whose bandwidth is 1111Mbit/s. Despite the difficult technology, it boasts many advantages like wide bandwidth, high efficiency, large covering range, and rich user interface, which makes it ideal to realize business network moving into broadband.

FTTH Arrangement Plan

OLT is put at the end of ISP centre to control the connecting, managing and maintaining of channels. The longest distance between OLT and ONU can reach 10-20km. OLT has function to measure the logic distance between every ONU and OLT, so as to manage ONU to adjust the time to send signal, which assures the signals sent from different ONUs can be received and multiplexed at OLT. Bandwidth allocation enables OLT to allocate the bandwidth in accordance with ONU demand. Meanwhile, OLT equipment has multipoint hub feature, which means one OLT is linked with 32 ONUs (open end), and all ONUs under one OLT share and multiplex 1G bandwidth, that is, each OLT can provide maximum 1Gbps uplink and downlink bandwidth. POS (passive optical splitter), which connects OLT and ONU, is a passive optical equipment that: allocates the input (downlink) optical signals to multi output ports so that multi users can share one fiber and bandwidth; multiplexes a plurality of ONU optical signals into one fiber.

ONU Generally Has 1-32 MB Ports to Connect a Variety of Network Terminals

ONU is the device at the client end to access the end user or corridor switches. It uses one fiber to achieve time division multiplexing of the signals from multi ONUs into one OLT port by one POS. Due to the multipoint tree topology, the convergence device investment is less and the network level is clearer. Most ONU has a certain switch function whose uplink port is the PON port connected to OLT by POS, while downlink combines 1-32 RJ45 ports of MB to GB with different data equipment, like switches, broadband routers, PCs, IP phones, set-top boxes, and so on, which fulfills the multipoint rapid deployment.



Build Up Network at Home

Generally, the ONU connecting FTTH to user end provides at least 4 RJ45 MB ports. For families with wired LAN connection within four computers, it fulfills the need to share Internet access. In addition, users using dynamic IP FTTH network are able to add switches or extend wired and wireless networks according to the demand.

In fact, the current broadband router can perfectly support FTTH access solution. For a fixed IP only providing one Mbps RJ45 interface FTTH terminal, it can be extended through a broadband router or wireless router. When set, the user simply need to find ‘WAN port’ option in the WEB setting interface of the router, select ‘Static IP’ of the WAN port connection type, and then enter the IP address, subnet mask, gateway, and DNS address provided by your ISP in the following interface.

Besides, those who purchase broadband router or wireless router should pay attention to the following if they want to use it as switch or wireless AP in FTTH network: the twisted pair plug from the ONU device should be directly inserted in any router LAN interface; the default DHCP server function should be closed in the router's administration page; the IP address of the router and the dynamic IP ONU device should be set as the same network segment.


FTTH is called ‘the King’ in broadband age thanks to its capability to provide unlimited bandwidth, and it is the ultimate goal of broadband development. FTTH will sharply boost the network speed that it only takes several seconds to download a 500MB movie, 10 times faster than the present ADSL. Furthermore, with the cost of FTTH construction reduced, FTTH is now coming to ordinary people's life.

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