Detailed explanation of the laying and testing of optical cable networks


With the maturity of the optical fiber transmission technology of laser cutting machine and the sharp decline in the price of optical fiber, the traditional coaxial transmission is less and less suitable for the development trend of today's optical Internet, and it is used as a carrier for disseminating information content. Optical fiber has the advantages of low transmission loss, long transmission distance, wide working frequency band, and strong anti-interference, making it the most ideal dissemination carrier for optical Internet.


The fiber is made of very pure calcite. Only single-mode optical fiber is used in optical fiber CCTV, the diameter of the insulating layer is 125 μm, the diameter of the buffer layer is 250 μm, and the core diameter of the light-transmitting part can only be 8~10 μm. Matters that should be considered in the laying and engineering of optical cables are basically the same as those in cable engineering projects.


However, the optical fiber has poor anti-support force and anti-side pressure characteristics, and it is very easy to break. Therefore, the technical standards for engineering construction methods, processing technology regulations, and process steps are relatively high, and the requirements for testing instruments, small machine tools, and auxiliary materials are high. Accuracy, dry cleaning, and also require that the actual operating staff have high technical expertise and professional skills. The construction of optical cable engineering is roughly divided into the following two steps: preparation in advance → router engineering project → optical cable laying → optical cable connection → project completion acceptance.


Laying and Testing of Optical Cable Networks

1. Prepare in advance

(1) Check whether the design and design materials, raw materials, small tools and equipment for engineering construction are complete, and the equipment for optical fiber fusion splicing shall be undertaken by the manufacturer, which may not be considered for the time being.

(2) Establish a high-quality construction staff. This is especially important, because the construction of optical fiber engineering is much stricter than the construction regulations of cable engineering, and all the carelessness on the construction site will lead to the expansion of optical fiber loss and even the broken core.


2. Router project

(1) Before laying the optical cable, you must first carefully survey the routers that the optical cable has passed through, master the local road engineering and overall planning, and avoid potential safety hazards such as pits, threshing farms, and gas stations as much as possible. After the router is identified, make specific and precise measurements of its length, accurate to within 50m. It is also necessary to add the natural bending and various pre-embedding lengths at the time of release. Various pre-embedding also include the insertion of the hole wall bending, the pre-embedding on the rod, the pre-embedding on both sides of the connector, and the inclination of the sea level. Lift and other unique preloads. In order to make the optical cable continue when it breaks, a necessary allowance should be left at every 100 meters. The length of the allowance is usually 5%~10%, which is purchased according to the specific necessary length and marked when winding.

fiber optic cable

(2) Draw relative path construction drawings. On the pre-planted telephone poles, draw the relative path construction drawings, and indicate the number of each telephone pole or underground drainage pipe entrance and exit poles and the length of the pipeline, and determine the length and location of the margin that must be vacated. . In this way, the length of the optical cable can be reasonably used, the flow is reasonable, and the melting point can be avoided as much as possible.


(3) It is best to add the two optical fiber joints at a location with flat terrain and solid geology, bypassing ponds, rivers, canals and roads, and preferably at the entrance and exit of utility poles or pipelines. It falls 0.5 to 1m up and down next to the utility pole, which is called "distribution plate" in this work. Effective panning reduces melt junctions. Another point should be indicated on the construction drawings. When the optical cable breaks, it is helpful to quickly find the breakpoint with instruments and equipment to carry out maintenance.


3. Optical cable laying

(1) The optical fibers of the same batch number have the same mode field diameter. After the optical fiber is broken at a certain point, the mode field between the two sides can be regarded as the same. impact is minimized. Therefore, it is stipulated that optical cable manufacturers use bare fibers of the same batch number, and continue to produce them according to the specified length of optical cable. In each disk, the serial number is sequentially marked, and the A (bright red) and B (emerald green) ends are marked respectively, and no number skipping is allowed. When building the optical cable, it should be distributed according to the serial number along the definite router sequence, and ensure that the B end of the optical cable in the front coil is connected to the A end of the optical cable in the latter coil, so as to ensure that the diameter of the inner hole mode field of the two fibers is consistent during the continuation, so that the welding loss will be lost. The value exceeds the minimum.


(3) Seven 2.2mm galvanized steel strands can be used as cables for suspension cables. Cables and optical cables should have excellent grounding devices, lightning protection and anti-electricity measures, as well as the physical properties of anti-freezing and anti-sand. The horizontal and vertical distance between the empty frame cable and the power line should be about 2m, the minimum height-width ratio from the road should be 5m, and the minimum distance from the roof should be 1.5m. There are 3 types of hanging types of air-frame optical cables: cable-supporting type, cable-wound type and self-supporting type. The self-supporting type does not require steel strands, the optical cable is loose, and the wind load is weak, so the hanging type is common.


(4) Empty optical cable distribution. Because the length of the reel of the optical cable is much longer than that of the cable, the length will reach several kilometers, so it is subject to the limit of the allowable rated tensile force and bending half warp. On the construction site, it is necessary to pay attention not to yank and kink. . Generally, the allowable tensile force of the optical cable is about 150~200kg. The bending semi-diameter of the optical cable should exceed or be equivalent to 10-15 times the diameter of the optical cable, and the bending semi-diameter should exceed or be equivalent to 20 times when the project is released. In order to prevent the optical cable from being placed in the middle of the road, about 20m away from the utility pole, build it in opposite directions, build the first half of the roll first, then release the second half of the optical cable from the reel, and place it on the soil according to the "8" method. , and then distributed.


(5) When the optical cable is issued, it is forbidden to make a small circle, fold and distort the optical cable, and then configure the wireless walkie-talkie with the necessary number of radios. Note that the force is even, the driving force does not exceed 80% of the allowable optical cable, and the maximum driving force does not exceed 100% in an instant. On the other hand, when building, a full-time person should be responsible for the turn of the optical cable or the complex terrain, and the car is not allowed to roll.


Use pulleys to distribute optical cables from empty racks. Hang moving pulleys (usually 1 moving pulley every 10~20m) on the rack rods and cables in advance, and reduce the sag at the places where the optical cable leads to the moving pulleys and lowers the moving pulleys to reduce the support force. Then put the traction rope between the moving pulleys, the traction rope is tied to the traction head of the optical cable, and the optical cable is allowed to climb up the pole with the necessary driving force and hang on the cable.


The distance between the hooks of the optical cable is 40cm, the hasp orientation of the hook on the pull wire should be the same, there should be a convex water seepage ditch at each pole, and the length of the pole plus 3m should be reserved at the interface of each cable to facilitate the connection. The actual operation of the road surface welding, and there must be a necessary reserve every 500 meters.


4. Optical cable connection

(1) The common optical cables are layered, skeleton diagram and management center bundled and tubular optical cables. The color of the core is divided into cost, orange, green, brown, gray, white, black, red, yellow, purple, Pink, green, this is called the full chromatographic analysis of the core tone, some optical cable manufacturers use "blue" to replace a certain tone in the chromatographic analysis. The multi-core optical fiber cable puts the optical fibers of different hues into one group in the same bundle tube, so that there will be many bundle tubes in a multi-core optical fiber cable. Facing the cross section of the optical cable, the red bundle tube is regarded as the first bundle tube of the optical cable, and the clockwise direction is successively white one, white two, white three... The last one is the green bundle tube. For fiber continuation, the standard that should be followed is: when the number of cores is the same, the matching color optical fibers outside the same bundle are connected.


(2) The whole process and process of optical fiber continuation:

a. Strip the optical cable and fix the optical cable into the splice box.

b. Splitting the fiber across the heat shrink tube. Separate fibers with different bundles and different hues. Go over heat shrink tubing. Fiber optic stripped coatings are sensitive, use heat shrink tubing to maintain fiber splices.

c. Turn on the switching power supply of the fusion splicer, and select a suitable fusion splicing procedure. Before each application of the fusion splicer, the fusion splicer should be placed in the fusion splicing environment for at least 15 minutes, and the dust in the fusion splicer should be removed immediately after the application, especially the fumes from the fixtures and the mirror glass type tanks. and fiber debris.


d. Make the inner hole of the optical fiber. The quality of the optical fiber inner hole will immediately affect the continuation quality, so it is necessary to make a qualified inner hole before welding.

e. Place the fiber. Put the fiber into the V-shaped groove of the fusion splicer, carefully press the fiber bender and the fiber fixture, set the position of the fiber in the bender according to the length of the fiber laser cutting, and close the sand-proof cover.


f. Continue the fiber, press and hold the start button, the fiber will move in the same way. During the whole process of moving, carry out pre-heating, charging and discharging to soften the inner hole. Due to the effect of interfacial tension, the inner hole of the fiber becomes round, and the inner hole of the fiber is deepened and points to the management center, and moves The fiber, when the gap in the middle of the fiber inner hole is suitable, the fusion splicer terminates the same movement, set the original gap, the fusion splicer accurately measures, and displays the information laser cutting angle. After the original gap setting is performed, the core or insulation layer is pointed at the beginning, and then the fusion splicer reduces the gap, and the electric isolation caused by high voltage charging and discharging will splicing the two fibers together. Finally, the central processor estimates the loss and displays the marked value. Information is on the display.


g. Remove the fiber and heat the heat shrinkable tube with a hot air furnace. Open the sand-proof cover, remove the optical fiber from the fusion splicer, put the heat shrinkable tube in the bare fiber management center, put it in the hot air furnace to heat, remove the optical fiber from the electric heater after the end, and wait for water cooling.

h. The fiber is coiled and fixed. Coil the continuous fiber into the fiber receiving tray. When coiling the fiber, the larger the semi-longitude of the coil, the greater the inclination, and the smaller the loss of the entire route. Therefore, it is necessary to maintain the necessary semi-longitude to keep the laser in the fiber. When conveying in the core, it prevents unnecessary wear and tear.

i. Tightness and Offline. Suburban extension boxes must be well sealed to avoid water leakage.


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