Basic knowledge of fiber optic cables and their devices


1. FTTH cable

FTTH (FiberToTheHome), 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 advantages of FTTH are mainly 5 points:

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

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 fiber, 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.


2. Indoor optical cable

Indoor optical cables are classified according to the use environment of optical cables, as opposed to outdoor optical cables.

ftth cable

Indoor optical cable is a cable formed by optical fiber (optical transmission carrier) through a certain process. It is mainly composed of optical fiber (glass filament as thin as hair), plastic protective sleeve and plastic outer skin. There is no metal such as gold, silver, copper and aluminum in the optical cable, and generally has no recycling value.


Indoor optical cable is a kind of communication line in which a certain number of optical fibers form a cable core according to a certain method, which is covered with a sheath, and some are also covered with an outer sheath to realize optical signal transmission.


Indoor optical cables have low tensile strength and poor protective layers, but are also lighter and more economical. Indoor optical cables are mainly used for wiring in buildings and connections between network devices.


3. Outdoor optical cable

Outdoor fiber optic cable, used for outdoor fiber optic cable. The opposite is the indoor optical cable.


Outdoor optical cable is a communication line that realizes optical signal transmission. The cable core is composed of a certain number of optical fibers according to a certain method, and is covered with a sheath, and some are also covered with an outer sheath.


Outdoor optical cables are mainly composed of optical fibers (glass filaments as thin as hair), plastic protective sleeves and plastic outer skins. There are no metals such as gold, silver, copper and aluminum in the optical cables, and generally have no recycling value.


Outdoor optical cables have higher tensile strength, thicker protective layers, and are usually armored (that is, wrapped with metal skins). Outdoor optical cables are mainly used for interconnection between buildings and between remote networks.


4. Optical fiber jumper

Fiber optic patch cords (also known as fiber optic connectors) are used to make patch cords from equipment to fiber optic cabling links. Optical fiber jumpers have a thicker protective layer and are generally used for the connection between optical transceivers and terminal boxes. Commonly used fiber jumpers include: ST type, LC type, FC type, SC type.


Main categories:

Single-mode fiber jumper (Single-mode Fiber): Generally, the single-mode fiber jumper is represented by yellow, and the connector and protective sleeve are blue; the transmission distance is longer.


Multi-mode fiber jumper (Multi-mode Fiber): Generally, the multi-mode fiber jumper is represented by orange, and some are represented by gray, and the connector and protective sleeve are in beige or black; the transmission distance is short.


Fiber jumper connector explanation:

sc: square fiber connector, FC: round with thread, ST: similar to BNC, LC: separate structure for transceiver, MT-RJ: square, two fibers at one end, integrated transceiver


pc: direct contact, APC: 8-degree inclined contact surface, UPC: curved contact surface


5. Fiber coupler

Fiber optic couplers are also called fiber optic adapters, and fiber optic couplers (FiberAdapter) are used for the connection and coupling of fiber optic active connectors. Select the model according to the connector of the fiber optic connector. According to the structure of the connector, it can be divided into: FC, SC, ST, LC, MTRJ, MPO, MU, SMA, DDI, DIN4, D4, E2000 various forms, using good sintering technology to ensure excellent strength and stability (200~600gf Insertion force)


The scope of application of the coupler: Optical fiber communication network Optical fiber broadband access network Optical fiber CATV Optical fiber instrumentation Optical fiber local area network


6. Optical fiber terminal box

Optical cable terminal box (also known as optical fiber terminal box or optical fiber box) is a connection device between small-core optical cables and terminals.


7. Optical fiber fusion splicer

When two optical cables are connected, the optical fibers in the optical cables should be butted together, because the optical fibers are like glass filaments, and the two ends must be re-melted with special connectors, and then the connectors are clamped together so that the optical signal can pass.


When light is transmitted in an optical fiber, a loss will occur, and this loss is mainly composed of the transmission loss of the optical fiber itself and the splice loss at the optical fiber joint. Once the optical cable is ordered, the transmission loss of the optical fiber itself is basically determined, and the splice loss at the optical fiber joint is related to the optical fiber itself and on-site construction. Efforts to reduce the splice loss at the optical fiber joint can increase the optical fiber relay amplification transmission distance and improve the attenuation margin of the optical fiber link.


8. Optical fiber transceiver

Optical fiber transceiver is an Ethernet transmission media conversion unit that interchanges short-distance twisted-pair electrical signals and long-distance optical signals, and is also called a fiber converter in many places. The product is generally used in the actual network environment where the Ethernet cable cannot cover and must use optical fiber to extend the transmission distance, and is usually located in the access layer application of the broadband metropolitan area network; at the same time, it helps to connect the last mile of optical fiber to the metropolitan area. It also plays a huge role on the Internet and beyond.


9. Optical transceiver

Optical transceiver is an optical fiber communication device that prolongs data transmission. It mainly uses the characteristics of optical transmission to achieve the purpose of long-distance transmission through signal modulation, photoelectric conversion and other technologies. Optical transceivers are generally used in pairs and are divided into optical transmitters and optical receivers. The optical transmitter completes electrical/optical conversion and transmits the optical signal for optical fiber transmission; the optical receiver mainly restores the optical signal received from the optical fiber to Electrical signal, complete the light/electrical conversion. The function of the optical transceiver is to transmit data remotely.


There are many types of optical transceivers, such as telephone optical transceivers, network optical transceivers, etc., and video optical transceivers are commonly used (especially widely used in the security industry).


Optical transceivers are terminal equipment for optical signal transmission. Its essence is: photoelectric conversion transmission equipment; placed at both ends of the optical cable; one receive and one transmit, as the name suggests, the optical transceiver. Therefore, optical transceivers are used in pairs. Generally, when buying optical transceivers, it is said to buy several pairs, not several.


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