Technical issues in connection of Single-Mode Optical Fiber

A Single-Mode Optical Fiber transmits only a single base mode optical fiber at a given working wavelength. It does not have mode dispersion, so the single-mode optical fiber has a very wide transmission band, used for long distance, large capacity transmission. The core of a single-mode optical fiber is very fine. The diameter of the core is only 8-10 μm, and the diameter of the package layer is 125 μM. It can be made for a long time. However, for the convenience of manufacturing, transportation and construction, the factory length of the optical cable is usually 1-6 bytes. The transmission loss of single-mode optical fiber is now as low as 1.55 dB/μs), and the optical fiber connection length is not less than 2 Gb/s.

There are many optical fiber connection methods. At present, the arc welding method is the most superior and most widely used. The arc welding method fuses the optical fiber with the high-temperature melt performance and the high-temperature arc principle generated by high-voltage tip discharge. Currently, image processing technology is used to automatically set the position of the optical fiber end face. The Automatic Centering and automatic fusion of Single-Mode Optical Fiber. By switching the video tube screen, you can observe the centering and fusion of the optical fiber in two vertical and horizontal ways. The connection loss can also be estimated and displayed based on the deviation and inclination of the core shaft.

During optical fiber connection, follow these steps:

(1) heat shrinkable sleeve tubes with steel wires that are pre-mounted to the optical fiber cables;

(2) Remove the coating layer, use the vertical Clamp of the coated clamp to quickly remove the 20-30mm long coating and secondary coating layer, and use the cotton balls or mirror paper soaked in alcohol to try the optical fiber, clean the core, and note that there should be no cracks and scratches on the surface of the optical fiber.

(3) cutting the optical fiber and making the end face. In the optical fiber connection, the preparation of the optical fiber end face is the most critical process. One of the important reasons for optical fiber connection loss is the improvement of the optical fiber end face. It requires that the end face after preparation be flat, no Burr, no defect, and perpendicular to the axis to present a smooth and flat mirror area, and keep clean to avoid dust pollution. There are three methods to prepare the end face. One is the marking method. A mechanical cutting tool is used to draw a path mark perpendicular to the optical fiber on the surface with a diamond knife. The face is 10 Gbit/s away from the coating layer and can be easily touched, the optical fiber breaks naturally at the mark position. The second is the cutting clamp method, which uses a self-made hand-held simple clamp for cutting. Third, the ultrasonic electric cutting method. These three methods, as long as the appliance is good, the operation is proper, the preparation of the end face is very good.

(4) add the two optical fiber cables to the splicer for fusion. The splicer automatically operates the splitters.

⑸ Use an OTDR meter to evaluate the connection performance test. After the connection indicators are met, reinforce and protect the connection parts, that is, heat-Melt Heat-shrinkable Tubes with steel wires.

Finally, after all the fiber cores are connected, the OTDR instruments will be used in the receiving inventory for re-testing, and those with different cells will be re-accepted or re-connected until they are qualified.

The loss index of single-mode optical fiber connection is usually set to 0.08dB. During construction, the index can be specified according to the actual situation, but generally not greater than 0.08dB.

Optical Fiber Connection loss is caused by imperfect connection points. There are many factors that affect the imperfect connection points. There are two categories, namely, external and internal factors. Internal factors refer to the imperfect optical fiber, which cannot be reduced by improving the connection process. They include core diameter mismatch, refractive index distribution mismatch, poor fiber concentricity, and Mode Field Diameter mismatch, therefore, in the connection test, the connection loss value may be large and negative. Multiple connections can only reduce the unidirectional value and the average value tends to be zero, but the positive and negative phenomena cannot be avoided. The positive and negative phenomena have a certain impact on the Optical Fiber Transmission Loss. In the project, the same batch of factory optical cables should be used as much as possible when configuring the optical cable tray. The A and B ends should correspond to each other as much as possible, and the connection process should be improved manually to reduce connection loss.

External factors refer to the non-optical fiber itself is not perfect, but the connection process is poor, including the horizontal, vertical, Axial Angle Deviation of the core position, optical fiber end face pollution, this is because the connection loss is too large due to human factors such as untimely maintenance and improper operation of the melting machine during the connection process.

Next we will mainly discuss the common problems and preventive measures in connection. Taking the Japanese Fujiko automatic melting machine as an example, the horizontal deviation, vertical deviation, and Axial Angle Deviation of the core position are due to the discomfort of the electrode position, the Mode Field experiment can be performed before the connection starts, and the mode suitable for connecting to the optical fiber and various parameters can be selected. Then, perform various maintenance inspections on the melting machine menu, such as driver Recovery Program maintenance, adjusting the focus of the melting machine; dust inspection and maintenance, so that the melting machine lenses, electrodes and other dust pollution cleaning; discharge experiments on the electrode position to adjust the proper electrode position.

The discharge time, discharge intensity, and push volume are three important factors that cannot be ignored during the optical fiber fusion process. They directly affect the mechanical strength and loss of the optical fiber joint, the discharge duration is proportional to the strength of the optical fiber joint. However, if the discharge duration is too long, the optical fiber may become aging due to high temperature. Therefore, the discharge duration is usually 2-5 seconds. The discharge intensity should also be appropriate. If the discharge intensity is too strong, the optical fiber will be aging. If the discharge intensity is too weak, the optical fiber connection is poor, affecting connection loss. The discharge intensity is usually determined based on the actual situation, generally between 45-65. The amount of push refers to the amount of push that must be pushed along with the fusion of the optical fiber when the optical fiber is put into the melting machine for fusion. A large amount of push will make the Optical Fiber Joint thicker and smaller, and the connector thinner. Generally, the push volume is controlled in the range of 15--20 μm. By selecting appropriate values, we can reduce the connection loss.

Second, the connection personnel should be strictly required, and the connection should be carried out in strict accordance with the Operation Specifications and operating procedures. If the position of the optical fiber is properly placed, the optical fiber cannot be connected when the position is too large or too small from the electrode. When the position of the optical fiber connection is completed, the optical fiber must be removed after the screen is restored to standby; in addition, after the hot melt and heat shrinkable tube, you must wait for it to be removed after cooling and so on.

Finally, it is worth noting that the heat shrinkable tube should also be clean, clean, and dust-free. Otherwise, there will be damage to the dust connection points during hot melt, resulting in increased losses. When receiving data to the storage tray, try to make a large harvest to avoid the loss caused by small circles. The optical fiber should be fixed with tape in the receiving tray, so it cannot appear on the bullet trend to avoid future damage.

1. Diamond knives show their skills in Single-Mode Optical Fiber Connection
2. Several Single-Mode Optical Fibers