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Talk about fiber access

When it comes to FTTH, we must first talk about fiber access. Optical fiber access means that the optical fiber is used as the transmission medium between the central office and the user. Optical fiber access can be divided into active optical access and passive optical access. The main technology of optical fiber subscriber network is light wave transmission technology. At present, the multiplexing technology of optical fiber transmission is developing very fast, and most of them are already in practical use. According to the degree of fiber penetration into users, it can be divided into FTTC, FTTZ, FTTO, FTTF, FTTH, etc.

FTTH (Fiber To The Home), as the name suggests, is an optical fiber directly to the home. Specifically, FTTH refers to the installation of optical network units (ONUs) at home users or enterprise users, and is the optical access network application type closest to users in the optical access series except FTTD (fiber to the desktop). The significant technical feature of FTTH is that it not only provides greater bandwidth, but also enhances the transparency of the network to data formats, rates, wavelengths and protocols, relaxes the requirements for environmental conditions and power supply, and simplifies maintenance and installation.

The advantages of FTTH are mainly 5 points:

First, it is a passive network, from the central office to the user, basically passive in the middle;

Second, its bandwidth is relatively wide, and the long distance is just in line with the large-scale use of operators;

Third, because it is a business carried on optical fibers, there is no problem;

Fourth, because of its wide bandwidth, the supported protocols are more flexible;

Fifth, with the development of technology, including point-to-point, 1.25G and FTTH methods have developed relatively complete functions.

In the optical access family, there are FTTB (Fiber To The Building) fiber to the building, FTTC (Fiber To The Curb) fiber to the curb, FTTSA (Fiber To The Service Area) fiber to the service area and so on.

FTTB (Fiber To The Building): It means fiber to the building. It is a broadband access method based on the optimization of high-speed optical fiber local area network technology. It adopts the method of fiber to the building and network cable to the home to realize the broadband access of users. We call it FTTB. +LAN broadband access network (FTTB for short), which is the most reasonable, practical and cost-effective broadband access method. FTTB broadband access uses single-mode optical fiber high-speed network to achieve Gigabit to the community, LAN 100M to buildings, and 10M to users. Since FTTB is completely like a local area network in the Internet, there is no need to dial-up to use FTTB, and the FTTB dedicated line is connected to the Internet, and users can access the Internet as long as they are turned on. Of course, FTTB access to ISP will not be busy like ordinary dial-up Internet access. FTTB Internet access is only fast or slow, and there will be no busy access situation, and because FTTB Internet access does not access the Internet through the telephone exchange network, It only takes up broadband network resources and does not generate telephone charges when browsing the Internet with FTTB. FTTB, the hardware requirements are the same as those of ordinary LAN: computer and 10M Ethernet card, so the hardware investment for users is very small. FTTB high-speed private line users can not only enjoy all services on the Internet, inquiring information, seeking help, mail communication, e-commerce, stock and securities operations through the Internet, but also enjoy many broadband value-added services provided by ISPs, distance education, telemedicine, interactive Video (VOD, NVOD), interactive games, broadcast video, etc., and compared with HFC, FTTB can fully guarantee the bandwidth of each user, because the final 10M bandwidth of each user is exclusive.

The advantages of FTTB as a high-speed Internet access method are obvious, but we should also see the disadvantages. ISPs must invest a lot of money to lay high-speed networks in each user’s home, which greatly limits the promotion and application of FTTB. There is still a lot of work to be done that most netizens can afford.

(1) FTTN: Fiber To The Node, fiber to the node

(2) FTTZ: Fiber To The Zone, fiber to the cell

(3) FTTCab: Fiber To The Cabinet

(4) FTTC: Fiber To The Curb, fiber to the curb

(5) FTTB: Fiber To The Building

(6) FTTP: Fiber To The Premise, fiber to the customer premises

(7) FTTH: Fiber To The Home, fiber to the home

(8) FTTO: Fiber To The Office

In different application environments, the optical cables used also have structural differences to meet the special needs of different environments.

As shown above, in the traditional FTTX wiring environment. In the process of step-by-step distribution from the central office equipment network, various optical cables and optical fiber jumpers often need to be used alternately. When the central equipment room of the central office goes to the FTTC roadside or the junction box, the backbone cable generally uses the buried layer stranded outdoor armored optical cable with a large number of cores, such as GYTA, GYTS, etc.

Conventional outdoor multi-core optical cable & conventional outdoor cabinet

After the trunk cable enters the junction box, it passes through the first-level optical splitting, and then the outgoing second-level trunk cable is spliced with the pigtail in the ODF integrated module, and directly enters the FTTB fiber-to-building wiring environment. The secondary trunk cables at this stage generally use outdoor aerial or pipeline optical cables with a small number of cores, such as GYXTW.

Common outdoor central bundled fiber optic cable & common corridor fiber optic fiber distribution box

In the fiber distribution box or optical distribution box of the corridor, after the secondary trunk cable enters, it is split by the secondary optical fiber or directly spliced with the household pigtail fiber. the final terminal. In this environment, since most families are individual units and the wiring environment is complex, the optical cables used are butterfly-shaped leather cables with smaller cores and more flexible bending to ensure convenient construction. This is what we want today. Mainly introduced, FTTH home fiber jumper.

Before introducing the FTTH home optical fiber jumper, let’s briefly introduce the butterfly leather cable.

Leather cable is commonly known as indoor hanging wiring cable. It is to place the optical communication unit (optical fiber) in the center, place two parallel non-metallic reinforcement members (FRP) or metal reinforcement members on both sides, and finally, extrude black or colored polyvinyl chloride (PVC) or low-smoke halogen-free material (LSZH). , low smoke, halogen-free, flame retardant) sheathed. Because its cross section is a symmetrical butterfly shape, it is called a butterfly leather cable. The leather cable is mainly divided into two structures: outdoor self-supporting butterfly leather cable and indoor non-self-supporting butterfly leather cable.

Outdoor self-supporting butterfly leather cable & indoor non-self-supporting butterfly leather cable

In the traditional FTTH wiring, for the convenience of construction and quick connection, the method of leather cable + optical fiber quick connector has been widely used when entering the house, and the on-site end is completed and the wiring is fast. This method does not need to estimate the length of the jumper in advance, and does not need to use the optical fiber fusion splicer. The construction is really convenient and fast, and it was once the most widely used home access method in FTTH.

All kinds of fast fiber optic connectors

However, there are inevitable fatal flaws in optical fiber quick connectors.

One: Since the end of the fiber optic quick connector is connected quickly on site, the tensile force at the connector is not reliably guaranteed, and it is not as good as the fiber jumper with prefabricated ends.

Second: the loss of the optical fiber quick connector is not stable, and its loss is not only related to the quality of the optical fiber quick connector itself, but also has a great relationship with the quality of the fiber cutting by the builder. The fiber port is not flat, which will cause excessive fiber loss. And on-site construction personnel, not every constructor is professional and technically reliable.

Third: In the later stage, in order to solve the problem of uneven ports when the constructor cuts optical fibers, fiber matching paste is generally configured when using optical fiber quick connections to solve the problem of uneven optical fiber cutting ports. However, a new problem has arisen. Since the sealing performance of the quick connector itself is not very good, the optical fiber matching paste also has a service life. The optical fiber matching paste will fail in about 1 year, and the loss will be too large at the interface. In this case, it will cause a lot of trouble for the follow-up optical fiber maintenance.

Due to the above three reasons, the popularity of optical fiber quick connection gradually subsided after a period of time. In the current FTTH environment, only in temporary optical fiber repair and rapid wiring, optical fiber quick connection will be used as a short-term replacement for spare parts. use. And the market of prefabricated FTTH leather fiber patch cords, which were once suppressed by the heat of optical fiber quick connection, became popular again. Although the prefabricated fiber jumper requires the constructor and the buyer to budget the length and quantity of the fiber jumper in advance, its reliable stability has finally won the recognition of the market!

Conventional Indoor Leather Jumper & Conventional Outdoor Leather Jumper

2-core branched leather jumper & 4-core branched leather jumper

In recent years, there has been a new development of prefabricated patch cords. Most of the above conventional patch cords are only suitable for use in indoor environments. In the actual FTTX wiring environment, the fiber distribution box in FTTB, In many cases not in the corridor. Especially now that fiber-to-the-home has begun to spread in rural areas, in many rural wiring environments, FTTB is installed in an outdoor pole-mounted environment, and is pulled into the home overhead. In this environment, the patch cord must be waterproof, and the tensile strength of the interface must be more stringent. Conventional FTTH patch cords are no longer suitable for wiring construction in this environment. Therefore, a new batch of outdoor FTTH waterproof connector leather-to-home optical fiber jumpers came into being. Corning in the United States and Huawei in China have successively designed a batch of outdoor FTTH leather cable Mini-SC connectors.

MINI-SC for Huawei ports

MINI-SC for Corning Port

Waterproof optical fiber box with outdoor MINI-SC special waterproof adapter