Monitoring installation engineering fiber selection and laying method

In today's HD surveillance camera systems, fiber is one way to provide good bandwidth performance in all connections. When using a fiber-optic transmission system, the image quality of the system is limited only by the three factors of camera, environment and monitor, and the fiber-optic transmission system can transmit the image to a very distant place without any distortion of the signal. It does not detract from the sharpness or detail of the image. It can be said that the optical fiber transmission system is the lifeline of the entire monitoring system.

First, the type of fiber

Optical fibers are classified into indoor optical fibers, outdoor optical fibers, branched optical fibers, and wiring optical fibers depending on the application.

According to the laying method: self-supporting overhead fiber, pipe fiber, armored buried fiber and submarine fiber.

According to the fiber structure: beam tube fiber, layer twisted fiber, skeleton fiber, tight fiber, ribbon fiber, non-metal fiber and branch fiber.

According to the purpose: long-distance communication fiber, short-distance outdoor fiber, hybrid fiber and building fiber;

Optical fibers can be divided into single-mode and multi-mode according to the transmission mode, and single-mode optical fibers are generally used for monitoring.

Single-mode fiber: An optical fiber that transmits only one mode optical signal. Conventionally, G.652, G.653, G.654, and G.655 are classified into transmission classes. Single-mode optical fiber transmits hundreds of megabits of signals up to several tens of kilometers. Single-mode fiber, only the main mode is transmitted, that is, the light is transmitted only along the inner core of the fiber. Since the mode dispersion is completely avoided, the transmission band of the single-mode fiber is wide, so it is suitable for large-capacity, long-distance fiber-optic communication. The single mode fiber uses a light wavelength of 1310 nm or 1550 nm.

Multimode fiber: An optical fiber capable of transmitting multiple modes of optical signals, which is of the G.651 class. It is classified into OM1, OM2, and OM3 according to the optical mode, and the upper limit of the transmission distance of the multi-mode optical fiber transmission is 2 kilometers. Multimode fiber, in a certain working wavelength, there are multiple modes transmitted in the fiber. This fiber is called multimode fiber. Due to dispersion or aberration, this fiber has poor transmission performance and narrow transmission band. Smaller and shorter.

Second, fiber laying methods and requirements:

Conventional outdoor optical fibers are containers with a loose tube as the core, which is a common fiber core laying method; indoor optical fibers are usually tightly laid; the cores of large core fibers are also combined in a ribbon manner. core.

Fiber laying requirements: The bending radius of the fiber should be at least 15 times the outer diameter of the fiber, and should be at least 20 times during the construction process; when the fiber is laid, the fiber disk should be rotated synchronously with the deployment speed, and the speed of the fiber index is generally 15 meters per minute; when laying out the optical fiber, the optical fiber should be kept at a loose arc, and the buffering margin should be kept, and it should not be too much to avoid the back buckle of the optical fiber; the optical fiber has a reserved length of 5-10 meters at both ends. When laying the fiber, label the line and fill in the line record; all the fibers should not be exposed.

Third, the choice of optical core

The number of cores is the number of glass fibers contained in each fiber. The following small series introduces some methods to determine the number of fiber cores.

First, know the number of routing points in the layer, calculate the number of switches, and whether the connections between the switches are stacked or not. If the core switch is dual-system hot standby redundancy, 6 cores are sufficient (2 cores each use 2 cores and 2 cores redundant). If you do not stack a switch to 4 cores, multiply the number of switches by 4 plus 4 core redundancy, you can. (Note: Redundancy: as long as it is used more, the extra is called redundant active and standby: one used, the other one is the same as the standby; hot backup: at the same time in the working state; cold backup: the backup device is in standby mode.)

Experience: Each floor wiring closet (horizontal wiring cabinet), set up an optical fiber, generally six cores: two core use, two core spare, two core redundancy; also use eight core fiber. The minimum configuration of the specification is 2 cores per 48 points. Of course, 48 points can be selected as 4 cores, because the 2 core is the smallest unit of the fiber, and it is more appropriate to leave 2 cores as the backup.

The above is the introduction of the method for determining the number of cores of the fiber. You can find out. Backups can be selected for people, so the number of fiber cores that come out is much different. According to the specification, only one minimum selection and one backup core number can be guaranteed.

Fourth, pay attention to

In addition to the number of fibers and the type of fiber, the choice of fiber should be based on the use of the fiber to select the outer sheath of the fiber. Pay attention to the following points when selecting:

1. When the outdoor fiber is directly buried, the armored fiber should be selected. When the frame is empty, the fiber of the black plastic outer sheath with two or more reinforcing ribs can be selected.

2. The fiber used in the building should pay attention to its flame retardant, poison and smoke characteristics when it is selected. Generally, it is used in pipelines and forced ventilation. Flame retardant and smoked types can be used. Flame retardant should be used in exposed environment. , smokeless and non-toxic types.

When the vertical wiring in the 3rd floor is used, the layered fiber can be selected; for the horizontal wiring type, the branch fiber can be selected.

4. Optional multimode fiber with a transmission distance of less than 2km; relay or single mode fiber for more than 2km.

The above are a few issues that are considered from the application side, and they need to be flexible when implemented. In fact, the wiring environment is complex and diverse, and various problems may occur at any time. This requires us to strictly follow the wiring standards during planning and construction. If problems are encountered and flexible analysis is performed, it will be satisfactorily resolved.