According to the different use occasions, the optical cable is divided into indoor optical cable, outdoor optical cable, branch optical cable and distribution optical cable. Optical fiber can be divided into single-mode and multi-mode according to the transmission mode, so single-mode optical fiber is generally used for monitoring.
Fiber type
According to the different use occasions, the optical cable is divided into indoor optical cable, outdoor optical cable, branch optical cable and distribution optical cable. Optical fiber can be divided into single-mode and multi-mode according to the transmission mode, so single-mode optical fiber is generally used for monitoring.
Single mode optical fiber: the optical fiber that transmits only one mode optical signal. There are transmission level classifications such as G.652, G.653, g.654 and G.655 in general. The 100m signal distance of single mode optical fiber can reach tens of kilometers.
Multimode optical fiber: the optical fiber that can transmit multiple modes of optical signals, which is g.651 grade. According to the optical mode, it can be divided into om1, om2, OM3. The farthest transmission distance of multimode optical fiber is 2km.
Optical fiber laying mode
Conventional outdoor optical cable is the container with loose tube as the core, which is the most common way to lay optical fiber core.
The indoor optical cable is usually laid in a tight sleeve way.
The fiber cores of large number of fiber optic cables are also combined and laid in the form of ribbon.
cable structure
1. The most common structure of optical cable is stranded optical cable, which is generally used for more than 12 core optical cable. The cavity of optical cable can accommodate multiple loose tubes. Each loose tube can accommodate 6-12 core optical fiber cores. Stranded optical cable is the central reinforcement component, and the loose tube is surrounded by the central reinforcement core. For practical application, the core needs to be covered with different colors, 12 in total The number of loose tubes of layer stranded optical cable is generally less than 12, so the number of cores of layer stranded optical cable is generally from 12 cores to 144 cores.
2. Generally, the structure of outdoor optical cable below 12 cores is the central bundle tube type. This type of optical cable contains a central loose tube inside, which can contain 1-12 cores, and the outer sheath contains two parallel wires.
3. Ribbon cable, also known as frame groove structure, is generally used as the cable structure with a large number of cores.
Optical fiber supporting equipment
Fiber distribution frame (box): fiber terminal box is used to protect fiber and pigtail, and pigtail is used to connect fiber transceiver, fiber switch or optical terminal.
Optical fiber terminal box (junction box or fiber melting disk): the optical fiber junction box is to fuse two optical fibers together.
Pigtail: one end of the optical fiber pigtail is fused with the optical fiber, and the other end is connected with the optical fiber transceiver or optical fiber switch and other equipment.
ODF optical fiber distribution frame and optical coupler: in some large and medium-sized monitoring projects, equipment such as ODF optical fiber distribution frame and optical coupler may be used. ODF optical fiber distribution frame is mainly used in machine room, which can make many optical fibers more regular and convenient for maintenance.
Fiber optic transceiver: also known as photoelectric converter, it is a device that converts optical port and electric port, and is used in pairs. The electric port is connected with the switch, and the optical port is connected with the fiber pigtail.
Optical fiber module: the optical fiber module is mainly used in the optical fiber switch. Through the optical fiber module, the optical fiber pigtail can be directly connected to the switch, eliminating the optical transceiver, but the price of the optical fiber switch is relatively high.
Optical fiber knowledge
1. The tensile strength of optical fiber is very high, close to the tensile strength of metal;
2. The ductility of optical fiber (1%) is worse than that of metal (20%);
3. When there are cracks, bubbles or sundries in the optical fiber, it is easy to break under certain tension;
4. The fiber rain is easy to break and the cutting loss is greatly increased;
5. At low temperature, the loss increases with the decrease of temperature;
6. Optical fiber needs to be protected with enhanced mechanical performance and waterproof protection to ensure transmission performance.
Wavelength: communication window of optical signal for optical fiber communication, among which 8501310nm is multimode optical fiber communication window, which is short wavelength window; 131015501640nm is single-mode optical fiber communication window, which is long wavelength window.
Simplex: in communication, the signal can only be received or not sent, and one-way communication is understood as only receiving optical signal or only sending optical signal on a core optical fiber.
Duplex: it can receive and send signals, which are divided into half duplex and full duplex. Half duplex can be understood as a core optical fiber. After receiving the signal, it can send and feedback the signal through the same core optical fiber, but at this time, it can only send and cannot receive the signal; while full duplex still uses a core optical fiber, When receiving the signal, it can continuously send the signal. Receiving and sending two kinds of communication do not interfere with each other, which are generally realized by frequency division multiplexing, time division multiplexing and wavelength division multiplexing.