Fiber To The Home (FTTH) Principles
As copper cable prices continue to rise and optical cable costs continue to decline, Fiber To The Home (FTTH), which can provide bandwidth far higher than metallic wire access, is becoming the focus of ISP (broadband operator) promotion this year, and high-speed broadband entering ordinary households in the near future will no longer be a dream.
I. A Comprehensive Look at Fiber To The Home ([FTTH](
Optical fiber communication (FTTx) has long been regarded as the broadband access method with the greatest market prospects following DSL broadband access. Unlike common twisted-pair communication, it features higher operating frequencies, larger capacity (can be upgraded to 10-100Mbps dedicated bandwidth according to user needs), lower attenuation, immunity to strong electrical interference, strong resistance to electromagnetic pulses, and good confidentiality.
Optical fiber broadband communication (FTTx) includes multiple access forms, such as the common 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), etc.
Fiber To The Home ([FTTH](
For the many household users, FTTH is the best choice. This form can connect optical fiber and Optical Network Unit (ONU) directly to the home, making it the fiber access form closest to users among various fiber broadband access methods, except for FTTD (Fiber To The Desk). With the generalization of fiber broadband access forms, it should be noted that current FTTH broadband access no longer refers solely to fiber to the home, but broadly refers to various fiber-to-the-home access forms such as FTTO, FTTD, FTTN, etc.
In addition, readers should distinguish FTTH from the common "FTTx+LAN (fiber + LAN)" broadband access solution. FTTx+LAN is a broadband access solution that uses fiber + Category 5 twisted pair to achieve "100Mbps to the community or building, 1-10Mbps to the home" — the community switches and central office switches are connected to the Optical Network Unit (ONU), and Category 5 twisted pair integrated cabling is used within the community, allowing users to access the Internet at speeds of 1-10Mbps. Unlike FTTH, which provides dedicated bandwidth to a single household, FTTx+LAN bandwidth is shared by multiple users or households. When there are many shared users, the broadband bandwidth or network speed is difficult to guarantee.
II. Fiber To The Home ([FTTH](
At present, ADSL2+FTTH with dedicated bandwidth has become the mainstream trend for future broadband development. In terms of FTTH technology, following APON (ATMPON), there are currently two competing standards: GPON (Gigabit PON) developed by ITU/FSAN, and EPON (Ethernet PON) developed by the IEEE 802.3ah working group.
GPON technology is a new generation broadband passive optical integrated access standard based on ITU-T G.984.x standards, with an available bandwidth of approximately 1111Mbit/s. Although its technical implementation is complex, it offers advantages such as high bandwidth, high efficiency, large coverage, and rich user interfaces, and is regarded by some European and American operators as a relatively ideal technology for broadbandizing access networks.
The EPON solution has good scalability and can implement multiple fiber-to-the-home methods
EPON (Ethernet Passive Optical Network) is also a new type of fiber access network technology, with an effective upstream transmission total bandwidth of 1000Mbit/s. It adopts a point-to-multipoint structure and passive optical transmission, and can provide multiple services over Ethernet. It combines the advantages of PON technology and Ethernet technology, featuring low cost, high bandwidth, strong scalability, good compatibility with existing Ethernet, and convenient management. It is widely used in Asian regions such as China and Japan.
Regardless of the type, any PON optical fiber system consists of three main parts — OLT (Optical Line Terminal), POS (Passive optical splitter/coupler), ONU (Optical Network Unit) — along with its network management system. These components are installed by ISP installation personnel during deployment, and household users generally do not have the conditions to set them up themselves.
III. Fiber To The Home ([FTTH](
In terms of specific functions, the OLT is placed at the ISP central office and is responsible for controlling the connection, management, and maintenance of control channels. The maximum transmission distance between OLT and ONU can reach over 10-20km. The OLT has a ranging function to test the logical distance between each ONU and the OLT, and based on this, directs the ONU to adjust its signal transmission delay so that signals sent by ONUs at different distances can be accurately multiplexed together at the OLT. OLT equipment generally also has bandwidth allocation functions, allowing the OLT to allocate specific bandwidth according to ONU needs. Furthermore, OLT equipment has point-to-multipoint hub characteristics — one OLT can support 32 ONUs (and can be expanded later). All ONUs under each OLT share 1G bandwidth through time-division multiplexing, meaning each ONU can provide a maximum upstream and downstream bandwidth of 1Gbps.
The POS passive optical splitter, i.e., optical splitter or divider, is a passive device connecting the OLT and ONU. Its function is to distribute the input (downstream) optical signal to multiple output ports, allowing multiple users to share a single optical fiber and thus share bandwidth. In the upstream direction, it time-division multiplexes optical signals from multiple ONUs into a single optical fiber.
The ONU generally has 1-32 Fast Ethernet ports and can connect various network terminals
The ONU is a device at the user end used to connect end users or building switches. It uses a single optical fiber through a passive splitter to time-division multiplex data from multiple ONUs into one OLT port. Due to the point-to-multipoint tree topology, investment in aggregation equipment is reduced, and the network hierarchy is clearer. Most ONU devices themselves have certain switching functions. Their upstream interface is a PON interface, connected to the interface board of the OLT device through a passive splitter. The downstream side uses 1-32 Fast Ethernet or even Gigabit RJ45 ports to connect different data devices, such as switches, broadband routers, computers, IP phones, set-top boxes, etc., enabling rapid point-to-multipoint deployment.
IV. How to Set Up a Home Network
Generally, FTTH ONU equipment at the user end provides at least 4 Fast Ethernet RJ45 interfaces. For users with four computers in the home using wired network cards, this can already meet the needs of multi-machine shared Internet access in the household. In addition, for FTTH networks using dynamic IP, users can also connect switches or wireless APs as needed to expand wired and wireless networks.
Current broadband routers can perfectly support Fiber To The Home ([FTTH](
For FTTH terminals with a fixed IP that provide only one Fast Ethernet RJ45 interface, expansion can be achieved through a broadband router or wireless router. During configuration, simply find the "WAN port" option in the router's WEB settings interface, select "Static IP" as the WAN port connection type, and then enter the IP address, subnet mask, gateway, and DNS address provided by the ISP in the interface below.
In addition, for users who have already purchased a broadband router or wireless router, when using Fiber To The Home ([FTTH](
Since fiber access can provide unlimited bandwidth, Fiber To The Home ([FTTH](