The optical cable splice box permanently connects two optical cables together and has a protective connection part. The connection part of the optical cable, namely the optical cable joint, is the protective connection part of two or more optical cables through the optical cable connection sheath, which meets the requirements of transmission characteristics and mechanical performance.
The composition of the fiber optic cable splice box can be roughly divided into three parts:
1. Outer sheath and seal (shell)
The outer shell is the outermost layer of the joint box, mainly responsible for sealing function.
2. Sheath support component (bracket)
The supporting part of the sheath is the skeleton of the joint box, including brackets, cable fixing clips, fiber optic receiving trays, etc. They provide the splice enclosure with a certain mechanical strength to resist the influence of lateral stress on the optical fibers.
3. Connecting components (connectors) in cables
The internal connection part of the optical cable is some auxiliary components for docking services, such as metal sleeves or connection clamps for strengthening the core, bridge wires for connecting the aluminum sheaths of the optical cable at both ends of the joint, etc.
Performance requirements for optical cable splice box:
(1) There are many programs and laying methods applicable to connecting optical cables. The structural forms of joints are also diverse.
(2) Good sealing performance. Generally, it is required to effectively maintain waterproof, moisture-proof, and harmful gas penetration resistance within 20 years.
(3) Has a certain mechanical strength. When the fiber optic cable splice box is required to be pressed to 70% of its strength, the performance of the fiber optic cable is still not affected.
(4) Long term corrosion resistance. At present, the outer shell of the joint box is made of plastic products. In addition to ensuring the wear resistance, the anti-aging and insulation properties of materials should also be considered to meet the requirements of a 20-year service life.
(5) Detachable and reusable. In construction and maintenance, if the joint needs to be inspected, there is no need to cut off the optical cable. Simply open the joint sheath, package it after inspection, and use the remaining length of the optical fiber inside the sheath to quickly repair faults, save time and materials, improve economic efficiency, and ensure smooth communication. This is of great significance.
Accommodation and handling of remaining fiber length
After monitoring and evaluating the fiber optic connection and fiber optic connection loss, the remaining length of fiber optic cable is processed, and its storage method depends on the structure of the connection sheath of the fiber optic cable used. When winding optical fibers, attention should be paid to the curvature radius and stacking alignment. After leaving the long disk, it is generally necessary to retest the connection loss with an OTDR instrument. If it is found that the loss has increased, the cause should be checked and analyzed, and the fault should be eliminated before sealing the sheath.
1. The role of the remaining length of the optical fiber
(1) The need for reconnection;
(2) The need for transmission performance.
2. Adjustment method for remaining length of optical fiber
(1) Approximate direct method
(2) Rolling method
(3) Drum winding method
(4) Storage bag cylindrical winding method
3. Sealing treatment of fiber optic joint sheath
Different structures of connecting sheaths have different sealing methods. Before sealing, the sealing part of the optical cable should be cleaned and finely ground. Note that the sanding direction of sandpaper should be horizontal rotation, and it is not allowed to polish back and forth along the axial direction.
After packaging the optical cable, conduct air tightness inspection and photoelectric characteristic retest to confirm that the cable connection is good and the connection work is completed.
4. Install and fix the fiber optic cable joint box
The engineering design has determined the general installation and fixing methods. During construction, attention should be paid to implementing according to the design drawings, ensuring that the joint installation is standardized, neat, beautiful, and marked.
(1) Directly buried installation of optical cable splice box
The joint pit for buried optical cables should be located on the right side of the line. When it is necessary to be located on the left side of the route due to terrain restrictions, it should be marked on the route construction map. The bottom of the pit should be covered with 10 centimeters of fine soil or sand and should be solid. The top of the joint box should be covered with 20cm thick fine soil or sand, and then covered with cement board or red brick.
(2) Installation of overhead cable and optical cable joint box
The joints of overhead cables are generally installed next to the poles and should be bent. The reserved optical cables at both ends of the overhead cable joint should be placed on adjacent poles.
(3) Pipeline installation optical cable joint box
The joint box for laying optical cables in the pipeline should be installed at a higher position in the inspection well to prevent it from being soaked by accumulated water in the inspection well during the rainy season. The optical cable joint must be installed on the bracket of the optical cable joint box directly above the manhole. The remaining optical cable of the joint should be tightly attached to the manhole wall or manhole frame, coiled into an "O" ring, and fixed with binding wire. Note that the curvature radius of the "O" ring should not be less than 20 times the diameter of the optical cable.
