Monitoring fiber optic engineering, fiber selection
First, the type of fiber
Optical fibers are divided into indoor optical fibers, outdoor optical fibers, branch optical fibers, and distribution optical fibers according to different use occasions.
According to the laying method: self-supporting overhead optical fiber, pipeline optical fiber, armored buried optical fiber and submarine optical fiber.
According to the fiber structure, it is divided into: bundled fiber, layered fiber, skeleton fiber, tightly hugged fiber, ribbon fiber, non-metallic fiber and branchable fiber.
According to the purpose: optical fiber for long-distance communication, short-distance outdoor optical fiber, hybrid optical fiber and optical fiber for building;
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: Optical fiber that transmits only one mode of optical signal. There are conventional transmission grade classifications such as G.652, G.653, G.654, and G.655. Single-mode fiber can transmit 100M signals over a distance of dozens of kilometers. Single-mode fiber only transmits the main mode, that is to say, the light is only transmitted along the inner core of the fiber. Since mode scattering is completely avoided, the transmission frequency band of single-mode fiber is very wide, so it is suitable for large-capacity, long-distance fiber optic communication , the wavelength of light used by single-mode fiber is 1310nm or 1550nm.
Multimode fiber: fiber that can transmit multiple modes of optical signals, G.651 grade, divided into OM1, OM2, OM3 according to the optical mode, multimode fiber transmits 100M signals with a maximum transmission distance of 2 kilometers. Multimode fiber, at a certain working wavelength, there are multiple modes transmitted in the fiber, this fiber is called multimode fiber, due to dispersion or aberration, so the transmission performance of this fiber is poor, the frequency band is relatively narrow, and the transmission capacity Smaller and shorter distance.
Monitoring fiber optic engineering
2. Optical fiber laying methods and requirements:
Conventional outdoor optical fibers use loose tubes as the core container, which is the most common fiber core laying method; indoor optical fibers are commonly laid in tight-sleeve form; the cores of large-core fibers are also combined and laid in ribbon form. core.
Optical fiber laying requirements: the bending radius of the optical fiber should be at least 15 times the outer diameter of the optical fiber, and it should be less than 20 times during the construction process; when laying the optical fiber, the rotation of the optical fiber reel should be synchronized with the laying speed, and the speed of the optical fiber indexing is generally 15 meters per minute; when laying out the optical fiber, keep a slack arc at the outlet of the optical fiber, and keep the buffer margin, but not too much, to avoid the back buckle of the optical fiber; the reserved length of the optical fiber at both ends is 5-10 meters ; When laying optical fibers, labels should be made and the payout records should be filled in; all optical fibers should not be exposed.
3. The choice of optical core
The number of cores is the number of glass fibers contained in each fiber. The following Fnet will introduce some methods to determine the number of fiber cores.
First of all, clearly know the number of wiring points in this layer, calculate the number of switches, and whether the connections between switches are stacked or not. If the stack is stacked and the core switch is dual-machine hot standby redundancy, 6 cores are enough (2 cores each use 2 cores, and 2 cores are redundant). If you do not stack a switch to 4 cores, multiply the number of switches by 4 plus the redundancy of 4 cores, and you will be fine. (Note: Redundancy: as long as there are more than the ones used, the extra ones are called redundant master and backup: one is used, and the other is exactly the same as backup; hot backup: both are in working state at the same time; cold backup: the backup device is in standby mode.)
Experience: In the wiring room (horizontal wiring cabinet) of each floor, there is one optical fiber, generally six cores: two cores are used, two cores are reserved, and two cores are redundant; there are also eight-core optical fibers. The specification's minimum configuration is 2 cores per 48 points. Of course, 4 cores can be selected for 48 points, because 2 cores are the smallest unit of optical fiber, it is more appropriate to leave 2 more cores as backup.
The above is an introduction to the method of determining the number of fiber cores, you can understand. The backup can be selected according to the person, so the number of fiber cores produced varies greatly. According to the specification, it is only necessary to ensure a minimum selection plus a number of backup cores.
Fourth, pay attention
The selection of optical fibers depends not only on the number of optical fibers and the type of optical fibers, but also the outer sheath of the optical fibers according to the use of the optical fibers. Pay attention to the following points when selecting:
1. When the outdoor optical fiber is directly buried, the armored optical fiber should be selected. When overhead, the optical fiber with black plastic outer sheath with two or more reinforcing ribs can be selected.
2. When selecting optical fibers used in buildings, attention should be paid to their flame retardant, toxic and smoke characteristics. Generally, in pipes and forced ventilation, flame retardant and smoke types can be selected, and flame retardant should be selected in exposed environments. , smoke-free and non-toxic types.
3. For vertical wiring in the building, stranded optical fibers can be used; for horizontal wiring, branch optical fibers can be used.
4. Multi-mode fiber can be selected for transmission distances within 2km; relay or single-mode fiber can be selected for more than 2km.
The above are just a few issues that are considered from the application aspect, and need to be flexibly mastered during implementation. In fact, the wiring environment is complex and diverse, and various problems may appear at any time. This requires us to strictly follow the wiring standards during planning and construction. If problems are encountered, they will be satisfactorily solved by flexible analysis.