What should be paid attention to when wiring optical cables in buildings


In new buildings, there is usually a shaft along which fiber optic cables are laid through various floors, and fire protection measures need to be provided. So, people often ask the editor, what should we pay attention to when wiring optical cables in buildings? What are the particulars of optical cable wiring?


Building Fiber Optic Cabling

1. What should be paid attention to when wiring optical cables in buildings

In many older buildings there may be shafts with large slots. Pipes are usually installed in these shafts for laying cables such as gas, water, electricity, air conditioning, etc. When using such shafts to lay optical cables, the light must be protected all day long. The fiber optic cable can also be fixed to the corner.


There are two methods of laying fiber optic cables in shafts:

Lay down the fiber optic cable.

Pull the cable upwards.

It is usually easier to hang down than to pull up. But if it is difficult to move the fiber optic cable reeling machine to the upper floor, it can only be pulled from the bottom to the top. Pay attention to the following points when wiring.

fiber optic cable

1) Before laying the optical cable, check whether the optical fiber has any breakpoints, indentations and other damages.


2) Select the length of the optical cable according to the construction drawings, and avoid the sprinkling ditch, traffic arteries and other obstacles when distributing the panel.


3) The bending radius of the optical cable should not be less than 20 times the outer diameter of the optical cable. The optical cable can be pulled, and the ends should be properly treated. The pulling sum should be added to the reinforcing core. min, the length of one traction should not exceed 1Km.


4) The reserved length of the optical cable connector should not be less than 8m.


5) After laying a section of the optical cable, check whether the optical cable is damaged or not, and conduct a sampling test for the laying loss of the optical cable.


6) The optical cable connection should be operated by specially trained personnel, and the optical power meter or other instruments should be used to monitor the connection to minimize the connection loss. After the connection, the connection protection should be done, and the optical cable connector sheath should be installed.


7) The end of the optical cable should be wrapped with plastic tape, and the coil should be placed in the optical cable reserved box and fixed on the pole. The underground optical cable leads to the pole and must be threaded into the metal pipe.


8) When the optical cable is laid, the total loss of the channel needs to be measured, and the optical time domain reflectometer is used to observe the attenuation characteristic curve of the entire waveguide of the optical fiber channel.


9) The connection points and terminals of optical cables shall be permanently marked.


The steps to hang down the optical cable are as follows:

1) Place the optical cable reel at 1-1.5m away from the slot on the building layer (the optical cable is usually wound on the cable reel, not in the cardboard box), so that the optical cable can be controlled when the reel rotates. The cable spool is placed on the platform to remain vertical at all times, the spool is placed with the end of the cable on top of it, and the cable is pulled from the top of the spool.


2) Start the fiber optic spool to turn, and only when it turns, pull the fiber optic cable out of the top of it. When pulling the cable, make sure that the minimum bending radius and maximum tension are not exceeded.


3) Guide the optical cable into the slot. If it is a small hole, first install a plastic guide plate to prevent the optical cable from being damaged due to friction with the concrete side.


If the cable is to be lowered through a large opening, install a pulley on the center of the hole and pull the cable out of the wrapped wheel.


4) Slowly pull the fiber optic cable from the fiber optic cable reel until the person on the floor below can guide the fiber optic cable into the next slot.


5) Make a wire clip every 2m or so.


2. What are the emphasis on optical cable wiring

1 The choice of fiber

At present, the specifications of integrated cabling products in the market are rich and varied. The choice of optical fiber is the first problem we face. We should consider the following aspects:


1) According to the performance requirements, select the suitable fiber for the application

Optical fibers can be divided into single mode (SMF) and multimode (MMF) according to the transmission mode of light in them.


The core diameter of the multimode fiber is 50 or 62.5 μm, and the outer diameter of the cladding is 125 μm, which is expressed as 50/125 μm or 62.5/125 μm. The core diameter of the single-mode fiber is 8.3 μm, and the outer diameter of the cladding is 125 μm, which is expressed as 8.3/125 μm. A multimode fiber has a thicker core and can transmit light in multiple modes. However, its modal dispersion is large, which limits the frequency of transmitting digital signals, and it will become more serious with the increase of distance. Therefore, the distance of multimode fiber transmission is relatively short, generally only a few kilometers.


The central glass core of the single-mode fiber is relatively thin, the core diameter is generally 9 or 10 μm, and the outer diameter of the cladding is 125 μm, which is expressed as 8/125 μm, 9/125 μm, 10/125 μm, and can only transmit light of one mode. Therefore, its intermodal dispersion is very small, which is suitable for long-distance communication, but its chromatic dispersion plays a major role, so the single-mode fiber has higher requirements on the spectral width and stability of the light source, that is, the spectral width should be narrower and the stability should be better. .


2) Choose high quality fiber according to standard grade

Because traditional multimode fiber can only support 10 Gigabit transmission for several tens of meters, ISO/IEC 11801 has formulated a new multimode fiber standard grade, namely the OM3 category, for new optical transceivers used for 10 Gigabit applications. OM3 fiber is optimized for both LED and laser bandwidth modes and is subject to rigorous DMD testing and certification. The optical fiber cabling system using the new standard can support at least 10 Gigabit transmission to 300 meters in multimode mode, and can reach more than 10 kilometers in single mode mode (1550nm can support 40 kilometers transmission).


3) Select the most economical transmission frequency window from the perspective of cost performance

The working wavelengths of optical fibers are short-wave 850nm, long-wave 13l0nm and 1550nm. The fiber loss generally decreases with the increase of wavelength. The loss of 850nm is generally 2.5dB/km, the loss of 1.31μm is generally 0.35dB/km, and the loss of 1.55μm is generally 0.20dB/km, which is the lowest loss of optical fiber. The loss tends to increase for wavelengths above 1.65 μm. The main parameters of the 1310nm conventional single-mode fiber are determined by the International Telecommunication Union ITU-T in the G652 recommendation, and l310nm is just a low-loss window of the fiber.


Therefore, this fiber is also called G652 fiber. G.652.D is the latest index of single-mode fiber, the most stringent index among all G.652 levels, and is fully backward compatible. If only G.652 is specified, it generally means the performance specification of G.652.A, which should be paid special attention.


American CommScope SYSTIMAX Solutions has rich experience in the field of optical fiber cabling. After years of research and experiments, SYSTIMAX laboratory has analyzed the cost of the complete optical fiber system and came to the conclusion that optimizing the application of 850nm on multimode fiber will benefit users. The most, followed by the application of 1300nm on single-mode fiber.


4) In addition to the number of optical fibers and the type of optical fibers, the selection of optical fibers should also be based on the use environment of the optical cable to select the transmission distance within 2km. Multi-mode optical fibers can be selected. More than 2 km can be relayed or single-mode optical fibers can be selected. Optical fibers used in buildings should pay attention to their flame retardant, toxic and smoke characteristics when selecting them.


Generally, the type of flame retardant but smoke can be used in the pipeline or forced ventilation; if it is in an exposed environment, the type of flame retardant, non-toxic and smoke-free should be used. When the outdoor optical cable is directly buried, the armored optical cable should be selected. When overhead, an optical fiber with a black plastic outer jacket with two or more reinforcing ribs can be used.


Based on the above analysis, regardless of single-mode or multi-mode, users should invest in the best performance at the lowest price by considering various factors from the perspective of application, transmission distance, forward-looking, and cost.


2 Laying of fiber optic cables

Optical cables are divided into 4 cores, 6 cores, 8 cores, 12 cores, etc. according to the number of cores; they are divided into two types: overhead and direct buried according to the laying method; according to the supported distance, they are divided into multi-mode (within 2 kilometers), single-mode (2 kilometers) to dozens of kilometers). The enterprise local area network usually uses underground trenches, heating pipe trenches or buried outdoor multi-mode fibers in the park, and overhead single-mode fibers are considered in long-distance areas.


In fiber optic cabling, signal attenuation is also inevitable. There are two reasons: internal and external: the internal attenuation is related to the optical fiber material, and the external attenuation is related to the construction and installation, so it should be noted that:


1) The first thing that should be done is that the termination and maintenance of the optical fiber should be carried out by technical personnel who have received strict training, and the operation should be carried out according to the construction specifications of the optical fiber.


2)) There must be complete design and construction drawings for convenient and reliable construction and future inspection. During construction, be careful not to make the optical cable under heavy pressure or punctured by hard objects; in addition, the traction force should not exceed the maximum laying tension.


3) When the fiber is to be turned, its turning radius should be greater than 20 times the diameter of the fiber itself. When the optical fiber passes through the wall or floor, a protective plastic pipe with a mouth guard should be added, and the pipe should be filled with flame retardant filler. A certain amount of plastic pipes can also be pre-laid in the building.


4) When the optical fiber is used in the backbone network, at least 6-core optical cable should be used in the wiring room of each floor, and 12-core optical cable should be used for advanced applications. This is considered from three aspects: application, backup and expansion.


5) The most important thing for long-distance fiber laying is to choose a suitable path. The shortest path is not necessarily the best, but also pay attention to the right to use the land, the possibility of erection or burial, etc.


3 Design principles of integrated wiring system

1) Systematic cabling system

Information ports in any area of ​​the building eliminate the need for rewiring when reconnecting or relocating workstation terminals


2) Standardization of integrated wiring system

The information ports and corresponding supporting cables of the system must be unified so as to connect all types of networks and terminals smoothly, and at the same time, the flexibility of system maintenance and reconfiguration can also be realized.


3) The advancement and continuity of the integrated wiring system

The system must remain obsolete over a long period of time and not lose manufacturer support due to advancements. (Full consideration of system development and upward compatibility)


4) High performance price ratio of integrated wiring system

The selected wiring system has a reasonable structure, and the selected raw materials, media, connectors, and electrical equipment have good physical and electrical properties, and the price is moderate.


5) Practicality of integrated wiring system

The designed system should fully meet the current needs and development needs of users.


6) The integrated wiring system is flexible and convenient

The structural design should be easy to wire, the information port should be set reasonably, and it should be plug and play.


7) Integrated wiring system can be managed

Use standard building block connectors for wiring management.


8) The integrated wiring system has good scalability

The system is designed according to standard specifications, and the structure and connectors that are easy to expand are adopted to ensure easy expansion and replacement.


4 Optical fiber terminal box installation and wiring scheme

The fiber optic terminal box is a terminal connector of an optical cable. One end of it is an optical cable and the other end is a pigtail, which is equivalent to a device that splits an optical cable into a single optical fiber. The user optical cable terminal box installed on the wall, its function is to provide Fusion splicing of optical fibers and optical fibers, fusion splicing of optical fibers and pigtails, and handover of optical connectors.


It also provides mechanical protection and environmental protection for the fiber and its components, and allows for proper inspection to maintain the highest standards of fiber management. The terminal box is usually installed on a 19-inch rack and can accommodate a relatively large number of fiber optic cable ends.


What should be paid attention to when wiring optical cables in buildings

Regarding what should be paid attention to when cabling optical cables in buildings, today Xiaobian will answer here for you first. In fact, optical fibers are favored by integrated cabling of enterprise local area networks because of their large transmission frequency bandwidth, large communication capacity, and especially immunity from electromagnetic interference.

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