What Are The Requirements For Fusion Splicing Of OPGW Optical Cables?

OPGW cable fusion splicing is a meticulous job, especially in the end face preparation, fusion splicing, fiber coiling and other links, requiring the operator to observe carefully, consider carefully, and operate in accordance with the specifications.

Specific steps and practical operation skills.

1. Preparation of the end face: The preparation of the optical fiber end face includes stripping, cleaning and cutting. A qualified optical fiber end face is a necessary condition for fusion splicing, and the quality of the end face directly affects the quality of fusion splicing.

Stripping of the optical fiber coating layer: To strip the optical fiber coating layer, you must master the three-character fiber stripping method of flat, stable and fast. "Flat" means holding the fiber flat. Pinch the optical fiber with the thumb and index finger of the left hand to make it horizontal. The exposed length is 5cm. The remaining fiber is naturally bent between the ring finger and the little finger to increase the strength and prevent slipping. "Stable" means that the fiber stripping pliers must be held steadily. "Fast" means stripping the fiber quickly. The fiber stripping pliers should be perpendicular to the optical fiber, tilted inward at a certain angle, and then the pliers should gently clamp the optical fiber in the right hand, and then apply force to push it out along the axis of the optical fiber. The whole process should be natural and smooth, and done in one go.

Cleaning of bare fiber:

Cleaning of bare fiber should be done in the following two steps:

1) Observe whether the coating layer of the stripped part of the optical fiber is completely stripped. If there is any residue, it should be stripped again. If there is a very small amount of coating that is difficult to strip, you can use a cotton ball to dip in an appropriate amount of alcohol, soak it and gradually wipe it.

2) Tear the cotton into small fan-shaped pieces with flat layers, dip a little alcohol (it is better to pinch it with two fingers without overflow), fold it into a "V" shape, clamp the stripped optical fiber, wipe it along the axis of the optical fiber, and strive to succeed once. A piece of cotton should be replaced in time after 2 to 3 uses. Use different parts and layers of cotton each time, so as to improve the utilization rate of cotton and prevent the double contamination of the probe.

Bare fiber cutting:

Bare fiber cutting is the most critical part of fiber end face preparation. Precise and excellent cutters are the basis, and strict and scientific operating specifications are the guarantee.

1) Cutter selection: There are two types of cutters: manual (such as Japan CT-07 cutter) and electric (such as Ericsson FSU-925). The former is simple to operate and has reliable performance. As the operator's level improves, the cutting efficiency and quality can be greatly improved, and the bare fiber is required to be shorter, but the cutter has higher requirements for the ambient temperature difference. The latter has higher cutting quality and is suitable for working in cold conditions in the field, but the operation is more complicated.

The working speed is constant and the bare fiber is required to be longer. It is advisable for skilled operators to use manual cutters for rapid optical cable splicing or rescue at room temperature; on the contrary, it is better to use electric cutters for beginners or when working in colder conditions in the field.

2) Operating specifications: Operators should undergo special training to master the essentials of action and operating specifications. First, clean the cutter and adjust the position of the cutter. The cutter should be placed steadily. When cutting, the action should be natural, stable, not heavy, and not hurried to avoid the generation of bad end faces such as broken fibers, bevels, burrs, and cracks. In addition, learn to "play the piano" and reasonably allocate and use your right hand fingers to correspond and coordinate with the specific parts of the incision to improve the cutting speed and quality.

3) Beware of end face contamination: The heat shrink sleeve should be inserted before stripping, and it is strictly forbidden to insert it after the end face is prepared. The cleaning, cutting and welding time of the bare fiber should be closely connected, and the interval should not be too long, especially the prepared end face, which should not be placed in the air. Handle it gently when moving to prevent it from rubbing against other objects. During the splicing, the "V" groove, pressure plate, and blade of the cutter should be cleaned according to the environment to prevent end face contamination.

2. Fiber splicing: Fiber splicing is the central link of splicing, so high-performance splicing machines and scientific operations during the splicing process are very necessary.

Selection of welding machine: According to the requirements of optical cable projects, welding equipment with appropriate battery capacity and precision should be equipped. According to experience, the Japanese FSM-30S arc welding machine has excellent performance, stable operation, high welding quality, and is equipped with dust and windproof cover and large-capacity battery, which is suitable for various large and medium-sized optical cable projects. The Siemens X-76 welding machine is small in size, simple to operate, equipped with a simple cutter, and the battery and host are combined into one, which is easy to carry. The accuracy is slightly worse than the former, and the battery capacity is small, which is suitable for small and medium-sized optical cable projects.

Welding procedure: Before welding, according to the material and type of optical fiber, set the best pre-melting main melting current and time, as well as the key parameters such as the amount of optical fiber fed. During the welding process, the "V" groove, electrode, objective lens, welding chamber, etc. of the welding machine should be cleaned in time, and the welding should be observed at any time for bubbles, too thin, too thick, virtual melting, separation and other undesirable phenomena. Pay attention to the tracking and monitoring results of the OTDR test instrument, analyze the causes of the above-mentioned undesirable phenomena in time, and take corresponding improvement measures. If the phenomenon of virtual melting occurs multiple times, check whether the materials and models of the two optical fibers to be welded match, whether the cutter and the welding machine are contaminated by dust, and check the oxidation status of the electrodes. If there are no problems, the welding current should be appropriately increased.

3. Fiber coiling: Fiber coiling is a technology and an art. Scientific fiber coiling methods can make the fiber layout reasonable, the additional loss is small, and it can withstand the test of time and harsh environment, and can avoid fiber breakage caused by extrusion.

Fiber coiling rules:

1) Coil the fiber as a unit along the loose tube or the branch direction of the optical cable. The former is applicable to all splicing projects; the latter is only applicable to the end of the trunk optical cable and has one input and multiple outputs. Most branches are small-log optical cables. The rule is to coil the fiber once after welding and heat shrinking one or several optical fibers in the loose tube, or the optical fiber in the optical cable in a branch direction. The advantage is that it avoids the confusion of optical fibers between loose tubes or between different branch optical cables, making it reasonably laid out, easy to coil, easy to disassemble, and more convenient for future maintenance.

2) Coil the fiber in units of heat shrink tube placement in the reserved tray. This rule is to coil the fiber according to the number of heat shrink tubes that can be placed in a small placement area in the reserved tray in the splicing box. This avoids the unevenness of the same bundle of optical fibers due to different placement positions, difficulty in coiling and fixing, and even sharp bends and small circles.

3) In special cases, such as when special devices such as optical splitters, up/down pigtails, and pigtail cables appear in the splicing, ordinary optical fibers must be fused, heat-shrunk, and coiled first. Then, the above situations are handled in sequence. For safety, separate coiling operations are often performed to prevent additional losses caused by extrusion.

Fiber coiling method:

1) First the middle and then the two sides, that is, first place the heat-shrinked sleeves one by one in the fixed groove, and then handle the remaining fibers on both sides. Advantages: It is conducive to protecting the fiber joints and avoiding possible damage caused by fiber coiling. This method is often used when the reserved fiber tray space is small and the fiber is not easy to coil and fix.

2) Start winding the fiber from one end, fix the heat shrink tube, and then process the remaining fiber on the other side. Advantages: The copper tube placement position can be flexibly selected according to the length of the remaining fiber on one side, which is convenient and quick, and can avoid sharp bends and small circles.

3) Handling of special situations, such as when individual optical fibers are too long or too short, they can be placed at the end and coiled separately; when there are special optical devices, they can be processed on another coil. If they are coiled together with ordinary optical fibers, they should be gently placed on ordinary optical fibers, and a buffer pad should be added between the two to prevent fiber breakage caused by squeezing, and the tail fiber of the special optical device should not be too long.

4) Use a variety of pattern winding fibers according to actual conditions. According to the length of the remaining fiber and the size of the reserved space, coil naturally, and do not pull hard. A variety of pattern winding fibers such as circle, ellipse, "CC", "~" (note that R ≥ 4cm) should be flexibly used to maximize the use of the reserved space and effectively reduce the additional loss caused by winding fibers.

4. Ensure the quality of optical cable splicing: Strengthening the monitoring of OTDR test instruments is of great significance to ensure the quality of optical fiber splicing, reduce the additional loss caused by fiber coiling and the damage that may be caused to the optical fiber by the sealing box. In the entire splicing work, the four monitoring procedures of the OTDR test instrument must be strictly implemented:

1) Real-time tracking and monitoring of each core optical fiber during the splicing process to check the quality of each splicing point;
2) After each fiber coiling, the coiled optical fiber is inspected to determine the additional loss caused by the fiber coiling;
3) Before sealing the splicing box, all optical fibers are uniformly measured to find out whether there are any missed measurements and whether the reserved space of the optical fiber squeezes the optical fiber and the connector;
4) After the box is sealed, all optical fibers are finally monitored to check whether the sealing box damages the optical fiber.
5. Conclusion: Optical fiber splicing is a meticulous work, especially in the end face preparation, splicing, fiber coiling and other links, requiring the operator to observe carefully, consider carefully, and operate in a standardized manner.

In short, we must cultivate a rigorous and meticulous work style and be diligent in summarizing and thinking in order to improve practical operation skills, reduce splicing losses, and comprehensively improve the quality of optical cable splicing.