Installation and maintenance of fiber optic cabling


In a wiring system, the transmission medium is like a road or bridge in a transportation network. The safe operation of all networks and the mutual transfer of information between various parts must be based on the safe, stable and reliable basis of the wiring system, which is crucial.


Like copper cables, optical fibers are used as a transmission medium, and their correct termination, installation and construction are related to the operation of the network. How to properly install optical fiber, a very special medium? What problems should be paid attention to during the installation process? At the same time, as a user, what problems exist in the later maintenance? What are the requirements for the pre-design of the optical fiber cabling system for convenient maintenance?


Optical fiber is an abbreviation for optical fiber, which is composed of thin glass filaments with a diameter of about 0.1 mm. It is transparent and slender, and although thinner than a human hair, it has a waveguide structure that encloses light in it and propagates it in the axial direction. At present, the wavelength range of light waves used in optical communication is in the near-infrared region, with wavelengths ranging from 0.8 to 1.8um; it can be divided into short wavelength bands (0.85um) and long wavelength bands (1.31um and 1.55um). Optical fiber communication has the following advantages: wide transmission frequency, large communication capacity; low loss; no electromagnetic interference; thin wire diameter, light weight; abundant resources.


Today, there are two main international popular wiring standards, one is the North American standard EIA/TIA-568A; the other is the international standard ISO/IECIS 11801. EIA/TIA-568A and ISO/IECIS 11801 recommend using 62.5/125um multimode fiber optic cable, 50/125um multimode fiber optic cable and 8.3/125um multimode fiber optic cable.

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Single-mode fiber and multi-mode fiber can be easily distinguished from the size of the core. The core of single-mode fiber is very small, about 4-10um, and only transmits the main mode. In this way, modal dispersion can be completely avoided, so that the transmission frequency band is very wide and the transmission capacity is large. This fiber is suitable for large-capacity, long-distance fiber-optic communications. It is the inevitable trend of the future development of optical fiber communication and light wave technology.


Multimode fiber is further divided into multimode abrupt fiber and multimode graded fiber. The former has a larger core diameter and more transmission modes, so the bandwidth is narrower and the transmission capacity is smaller. Wide and larger transmission capacity, the latter is generally used at present.


fiber optic cabling

First, the choice of fiber

The selection of optical fiber is not only based on the number of fiber cores and the type of optical fiber, but also according to the use environment of the optical cable. for example:

1. If the transmission distance is less than 2km, you can choose multi-mode fiber. If it exceeds 2km, you can use relay or single-mode fiber.


2. When selecting optical fibers used in buildings, attention should be paid to their flame retardant, toxic and smoke characteristics. Generally, the type of flame retardant but smoke can be used in pipes or forced ventilation; if it is in an exposed environment, the type of flame retardant, non-toxic and smoke-free should be used.


3. 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.


Second, the construction of fiber optic wiring

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:


The first thing that should be done is that the termination and maintenance of the fiber should be performed by highly trained technicians.


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


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.


The length of one laying should not be too long (usually 2KM). When wiring, it should be pulled from the middle to both sides.


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


The most important thing for long-distance fiber optic 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.


When laying in mountainous areas and high-voltage power grid areas, attention should be paid to the reliable grounding of metal objects in the optical fiber. Generally, there should be 3 grounding points per kilometer, or non-metallic optical fibers should be selected.


The methods mainly include permanent connection, emergency connection and active connection.


1. Permanent optical fiber connection (hot melt):

This type of connection is to use the method of electric discharge to melt and connect the connection points of the optical fibers together. Generally used in long-distance connection, permanent or semi-permanent fixed connection. Its main feature is that the connection attenuation is the lowest among all connection methods, with a typical value of 0.01~0.03dB/point. However, when connecting, special equipment (fusion machine) and professionals are required to operate, and the connection point also needs to be protected by a special container.


2. Emergency connection (cold melting):

The emergency connection mainly uses mechanical and chemical methods to fix and bond the two optical fibers together. The main feature of this method is that the connection is fast and reliable, and the typical attenuation of the connection is 0.1~0.3dB/point. However, the long-term use of the connection point will be unstable, and the attenuation will increase greatly, so it can only be used for emergency use in a short time.


3. Active connection:

Active connections are a method of connecting sites to sites or sites to fiber optic cables using various fiber optic connection devices (plugs and sockets). This method is flexible, simple, convenient and reliable, and is mostly used in computer network wiring in buildings. Its typical attenuation is 1dB/connector.


3. Optical fiber detection

The main purpose of optical fiber inspection is to ensure the quality of system connection, reduce fault factors and find out the fault point of optical fiber. There are many detection methods, mainly divided into manual simple measurement and precision instrument measurement.


1. Manual measurement:

This method is generally used to quickly detect the on-off of optical fibers and to distinguish the fibers made during construction. It uses a simple light source to inject visible light from one end of the optical fiber, and observe which one emits light from the other end. Although this method is simple, it cannot quantitatively measure fiber attenuation and fiber breakpoints.


2. Precision instrument measurement:

Using an optical power meter or an optical time domain reflectometry (OTDR) to quantitatively measure the optical fiber, the attenuation of the optical fiber and the attenuation of the joint can be measured, and even the position of the breakpoint of the optical fiber can be measured. This measurement can be used to quantitatively analyze the causes of fiber optic network failures and evaluate fiber optic network products.


Let's discuss the installation and maintenance of fiber optic cabling. Modern IT technology is affecting the business and office models of the traditional financial industry. From business planning, staffing to enterprise architecture, changes have taken place with the development of IT deployment. The data center composed of core systems, peripheral applications, network communication, information security and IT infrastructure has become the "lifeline" of financial enterprises while providing stable and strong support for the business of the financial industry. Disaster backup has become a theme for the financial industry to deal with risks.


Since 2002, the State-owned Commercial Banks of Industry, Construction, Communications, and China have successively built national-level South and North data centers in Shanghai and Beijing in accordance with the idea of ​​large-scale data centralization. National financial institutions such as Agricultural Bank, UnionPay, China Merchants Bank, Futures Exchange, and Industrial Bank have also successively built their own national-level data centers. The construction of large data centers is still in the ascendant. How to build the wiring system of large data center in the financial industry and facilitate future maintenance has become an important topic in the field of wiring.


Data center wiring system planning method and comparison

To plan the wiring system, you must first understand the equipment that needs to be connected by the wiring system in the data center environment. Although financial enterprises have different business platforms, no matter whether a closed system or an open system is adopted, the active IT equipment to be connected to their data centers mainly includes core servers (mainframe or high-end minicomputers), peripheral application servers (low-end minicomputers, PC servers) ), storage, peripherals (tape drives, tape libraries, printers), communications (routers, switches), etc.


The interfaces of these devices are mainly optical fibers, and also have electrical ports (mainly distributed in PC servers). There are relatively many types of device interface channels in the host environment, including ESCON with a half-duplex transmission rate of 17MB/s, FICON with a full-duplex transmission rate of 100MB/s, MTRJ, SC, LC, ST, etc.; Mode and Multimode. In the minicomputer environment, the device interface types are relatively simple, mainly LC and SC, but the devices are relatively scattered.


The easiest way to connect the above devices is to connect them directly. That is, the optical fiber interfaces on different devices are directly connected by two-core optical jumpers, and the interconnection between various interface types is completed through the connectors at both ends, such as: ESCON duplex- ESCON duplex, SC-LC, LC-LC, etc. In small-scale fiber optic cabling systems, direct connection is the most cost-effective way to plan. But for large data centers with hundreds, or even thousands, of Fibre Channels to connect, the situation changes.


The development of modern information systems is getting faster and faster, and the updating and expansion of IT equipment are becoming more and more frequent. At the same time, with the rapid development of China's economy, the business of financial enterprises continues to grow, which also makes the scale of information systems continue to expand and update. In line with this, data center cabling systems are becoming more and more complex, and changes are becoming more frequent.


Taking a national data center with a national financial structure as an example, the direct-connected wiring method was adopted in the initial stage of construction. The investment in the wiring system in the computer room was more than 200,000 yuan, which is almost negligible compared to the investment of 100 million yuan in the connected IT equipment. Excluding. After being put into production, various business systems have been launched one after another, and system patches have been continuously improved during operation, and the wiring system has inevitably been added to the ranks of changes. The system operates during the day, and the change construction can only be scheduled to start at 12:00 in the middle of the night. Because of the direct connection, most of the work involves construction under the floor of the machine room. Faced with a criss-crossed and fragile two-core fiber in the bridge, I am worried that it will affect the normal working fiber. Therefore, whether it is the displacement of one end of the fiber or the replacement of the original fiber, a new two-core fiber is directly added. Optical fiber, the original one did not dare to pull out. Before long, used and discarded fibers fill the tray to the point where the cover plate can't cover it. Less than three years after it was put into production, the original equipment room wiring system had to be completely renovated, and the under-floor operations were reduced by using the backbone optical fiber and wiring cabinets. The investment in the wiring system renovation was an order of magnitude higher than the original construction investment.


In terms of maintenance, imagine hundreds of two-core fibers criss-crossing each other under a raised floor. It makes it more and more difficult to manage the equipment room, update and expand the equipment. When equipment needs to be replaced or added in the data center room, the various optical fibers under the raised floor make it very difficult and complicated to replace old optical fibers and lay new optical fibers. The whole body is affected by a single stroke, and a little carelessness will cause unexpected problems in the entire system.


Therefore, a more reasonable data center cabling system planning method should be to adopt a structured architecture, using backbone fibers and cabling cabinets to reduce under-floor operations. Although the connection points are added, the system architecture is more reasonable and the maintenance and management are more convenient. In recent years, major cabling manufacturers have launched fiber optic transmission systems (FTS), pre-terminated fiber optic cables and other solutions.


Data center wiring system planning, design and maintenance

With the rapid growth of the business of large financial institutions, the opportunity for equipment replacement and expansion will become more and more frequent. Therefore, it is very necessary to apply a flexible, structured, and easy-to-manage optical fiber connection system that makes the replacement and expansion of equipment simple and easy.

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