If the central glass core is very thin and can achieve long-distance, high-quality signal transmission, you can definitely think of single-mode fiber. And what is the difference between single-mode fiber and multi-mode fiber, we have all understood, then, how to connect single-mode fiber?
How to connect single-mode fiber
1. A heat-shrinkable tube with a steel wire is used to reinforce the connection part of the optical cable in advance;
2. Remove the coating layer, clamp the optical fiber vertically with the coating pliers, and quickly strip off the 20mm--30mm primary and secondary coating layers. Wipe the optical fiber with a cotton ball soaked in alcohol or lens paper. Wipe the fiber core clean to avoid cracks and scratches on the fiber surface.
3. Cut the optical fiber to make the end face. In the fiber connection, the most critical process is the production of the fiber end face. The perfection of the fiber end face determines the loss of the fiber connection. The fiber end face not only needs to be flat, but also presents a smooth and flat mirror area, free of burrs, defects, and perpendicular to the axis. The end face must be kept clean to avoid dust pollution.
There are three methods for making the end face: One is the notching method. Using a mechanical cutting knife, use a diamond knife to make a score on the surface in a direction perpendicular to the optical fiber, 10 mm away from the coating layer, lightly flick it, and the fiber naturally breaks at this score position. The second is the cutting pliers method, which uses a homemade hand-held simple pliers for cutting operations. The third is the ultrasonic electric cutting method. As long as these three methods have excellent equipment and proper operation, the effect of preparing end faces is very good.
4. Put the two optical fibers to be connected into the fusion splicer, and the fusion splicer will automatically splice.
5. Use the OTDR instrument to test and evaluate the connection performance. After the connection index is met, the connection part is reinforced and protected, that is, the heat shrinkable tube with steel wire is fused.
6. Finally, after all the fiber cores have been spliced, they should be put into the containment tray and retested with an OTDR instrument. Those that are unqualified must be re-contained or reconnected until they are qualified. The splice loss index of single-mode fiber is generally 0.08dB. During construction, the index can be specified according to the actual situation, but it is generally not greater than 0.08dB.
Optical fiber splice loss is caused by imperfect splice points. There are many factors that affect imperfect splice points, which can be summarized into two categories, namely, external and internal.
The internal cause refers to the imperfection of the fiber itself, and the loss cannot be reduced by improving the splicing process. It includes core diameter mismatch, refractive index distribution mismatch, poor fiber concentricity, and mode field diameter mismatch. So in the splicing test, splice loss The value will appear large positive and negative. Through multiple connections, the one-way value can only be smaller, and the average value tends to zero, but the positive and negative phenomena cannot be avoided. The positive and negative phenomena have a certain influence on the optical fiber transmission loss. In the project, the same batch of factory optical cables should be selected as far as possible when the optical cable is matched with the reel, and the A and B ends should be one-to-one as far as possible, which can reduce the connection loss to a certain extent.
External factors are not the imperfection of the optical fiber itself, but the poor connection technology. External factors have strict requirements on the connection personnel. The deviation of the core position in the horizontal, vertical, and axial angles of the fiber, and the contamination of the fiber end face, are caused by human factors such as untimely maintenance and improper operation of the fusion splicer during the splicing process.
Finally, it should be noted that the heat shrinkable tube should also be clean, clean, and dust-free, otherwise the dust will damage the connection point during heat melting, causing increased loss. When storing into the containment tray, try to harvest as large as possible to avoid increased loss caused by small circles. The optical fiber should be fixed with tape in the containment tray, and there should be no tendency to bounce to avoid future damage.
