Optical cable construction is roughly divided into the following steps: preparation → routing project → optical cable laying → optical cable splicing → project acceptance.
1、Preparation work
(1) check the design information, raw materials, construction tools and equipment are complete.
(2) Set up a high-quality construction team. This is crucial, because fiber optic construction than cable construction requirements are much more stringent, any negligence in construction will likely cause increased fiber loss, or even broken core.
2, routing engineering
(1) fiber optic cable laying before the first to do a serious survey of the route through the cable, to understand the local road construction and planning, try to avoid ponds, wheat farms, gas stations and other such potential hidden dangers. After the route is determined, the actual measurement of its length is done, accurate to within 50m. Also add the natural bending and various reserved lengths during deployment. Various reservations also include insertion of bending in the hole, reservation on the pole, reservation at both ends of the joint, and other special reservations such as increased curvature of the horizontal plane. In order to make the fiber optic cable in the event of a break and then splice, there should be a certain margin at each hundred meters, the margin length is generally 5% to 10%, according to the actual length needed to order, and in the winding plate when indicated.
(2) Draw path construction drawings. Numbering on the pre-planted poles, draw the path construction diagram, and state the number of each pole or underground pipe outlet pole and the length of the pipe, and set the length and location of the margin that needs to be left. This can effectively use the length of the fiber optic cable, reasonable configuration, so that the fusion splice point is minimized.
(3) two fiber optic joints are best placed in a flat, geologically stable location, avoiding ponds, rivers, ditches and roads, preferably located at the exit of the pole or pipe, overhead fiber optic cable joints should fall next to the pole 0.5 ~ 1m or so, this work is known as "matching plate". Reasonable distribution plate can reduce the fusion point. In addition, the construction drawings should also indicate the location of the fusion point, when the fiber optic cable breakpoint, it is easy to quickly find the breakpoint with the instrument for maintenance.
3, fiber optic cable laying
(1) the same batch of optical fiber, its mode field diameter is basically the same, the fiber at a point of disconnection, the mode field between the two ends can be regarded as the same, and thus in this disconnection point fusion splicing can make the mode field diameter of the fiber fusion loss to a minimum. So require the cable manufacturer with the same batch of bare fiber, according to the requirements of the cable length continuous production, in each tray on the sequence of numbers, and are marked a (red), b (green) end, no jump number. Erection of fiber optic cables need to be placed in order along the route determined by the number, and to ensure that the b end of the previous tray of fiber optic cable to be connected to the a end of the next tray of fiber optic cable, so as to ensure that the splicing of the two fiber end face mode field diameter is basically the same, so that the fusion loss value to reach a minimum.
(2) overhead fiber optic cable available 72.2mm galvanized steel stranded wire for hanging cable. Hanging wire and fiber optic cable to be well grounded, to have lightning protection, electrical protection measures, and shockproof, windproof mechanical properties. Overhead hanging wire and power line horizontal and vertical distance to more than 2m, from the ground to a minimum height of 5m, from the roof to a minimum distance of 1.5m. Overhead fiber optic cable hanging type there are three kinds: hanging wire hanging bracket hanging type, hanging wire winding type and self-supporting type. Self-supporting type without steel stranded hanging wire, cable sagging, poor wind load, so commonly used hanging type.
(3) overhead fiber optic cable placement. Due to the length of the reel than the cable, the length may reach several kilometers, it is limited by the allowable rated tension and bending radius, special attention in the construction can not be pulled and the occurrence of kink phenomenon. General fiber optic cable can be allowed to pull about 150 ~ 200kg, cable bending radius should be greater than or equal to 10 ~ 15 times the outside diameter of the cable, the construction of the bending radius should be greater than or equal to 20 times the deployment. In order to avoid the fiber optic cable placed in the middle of the road, about 20m away from the pole, erected in the two opposite directions, first erect the first half volume, in the second half volume of fiber optic cable from the plate down, according to the "8" way on the ground, and then deployment.
(4) in the cable placement, forbid the cable playing small circles and folding, twisting, and to be equipped with a certain number of walkie-talkies, "walk before and after, the cable on the shoulder" method of cable placement, can effectively prevent the occurrence of back buckle, but also pay attention to the uniform force, traction force does not exceed 80% of the cable allowed, the maximum instantaneous traction force does not exceed 100%. In addition, when erecting, in the bend of the cable or more complex terrain should be responsible for the vehicle is strictly prohibited to crush. Overhead deployment of fiber optic cable using pulley car, pre-hanging pulleys on the frame rod and hanging line (generally every 10 ~ 20m hanging a pulley), in the fiber optic cable leading up to the pulley, leading down to the pulley to reduce the drape, reduce the tension. Then wear a good traction rope between the pulleys, traction rope tied to the traction head of the cable, with a certain traction to let the cable climb up the rack pole, hanging on the hanging line. Fiber optic cable hook spacing of 40cm, hook in the direction of the hitch on the hanger line to be consistent, each pole at the convex drip gutter, each tray of fiber optic cable in the joint should be left with a rod length plus 3m margin, in order to connect the box ground fusion operation, and every few hundred meters to have a certain amount of disk stay.
4、Fiber optic cable splicing
Common fiber optic cable laminated, skeleton and center bundle tube cable, the color of the core in the order of Lan, orange, green, brown, gray, white, red, black, yellow, purple, pink, powder blue, which is known as the core color of the full color spectrum, some fiber optic cable manufacturers use "this color" to replace the color spectrum of a color. Multi-core fiber optic cable to different colors of fiber in the same bundle of tubes to become a group, so a multi-core cable may have several bundles of tubes. The cross-section of the fiber optic cable, the red bundle tube as the first bundle of fiber optic cable, clockwise for the white one, white two, white three ...... last is the green bundle tube. Fiber optic splicing, the principle should be followed: the number of cores is equal, the same bundle of the corresponding color fiber butt, the number of cores is different at the same time, in order to first connect the core of the larger, then the core of the smaller.
