What are the difficulties and steps of optical fiber fusion splicing? Fiber splicing is mainly divided into four steps: stripping, cutting, melting, and protecting. The so-called stripping: refers to the stripping of the optical fiber core in the optical cable, which includes the outermost plastic layer, the middle steel wire, the inner plastic layer and the color paint layer on the surface of the optical fiber.
The so-called cutting: refers to cutting the end faces of the optical fibers that have been stripped and prepared for fusion splicing with a "cutter".
The so-called fusing: refers to fusing two optical fibers together in a "fusion splicer".
The so-called protection: refers to the protection of the spliced optical fiber joints with "heat shrinkable tubes".
Decomposition of specific steps of optical fiber fusion splicing technology
Fiber end face preparation
The preparation of the fiber end face includes stripping, cleaning and cutting. A qualified fiber end face is a necessary condition for fusion splicing, and the quality of the end face directly affects the quality of fusion splicing.
(1) Stripping of optical fiber coating
Familiar with the flat, stable, fast three-character fiber stripping method. "Ping" means keeping 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 strength and prevent slipping. "Steady" means that the fiber stripping pliers should be held firmly. "Fast", that is, stripping the fiber should be fast. The fiber stripping pliers should be perpendicular to the fiber, and the upper direction should be inclined at a certain angle. Be natural and fluid, in one go.
(2) Cleaning of bare fibers
Observe whether the coating layer of the stripped part of the optical fiber is completely stripped off. If there is any residue, it should be stripped again. If there is a very small amount of coating layer that is not easy to peel off, use a cotton ball dipped in an appropriate amount of alcohol, and wipe it off gradually while dipping. A piece of cotton should be replaced in time after being used for 2-3 times, and different parts and layers of cotton should be used each time, which can not only improve the utilization rate of cotton, but also prevent the double pollution of the fiber probe.
(3) Cutting of bare fiber
Cleaving is the most critical part in the preparation of optical fiber end faces. A precise and excellent cutter is the foundation, and strict and scientific operating specifications are the guarantee.
Choice of Cutter There are two kinds of cutters, manual and electric. The former is easy to operate and reliable in performance. With the improvement of the operator's level, the cutting efficiency and quality can be greatly improved, and the bare fiber is required to be shorter, but the cutter has higher requirements on the ambient temperature difference. The latter has higher cutting quality and is suitable for working under 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 fast optical cable splicing or emergency rescue at room temperature; on the contrary, beginners or when working in colder conditions in the field, use electric cutters directly.
Operating specifications Operators should undergo special training to master the essentials of action and operating specifications. First of all, clean the cutter and adjust the position of the cutter. The cutter should be placed stably. When cutting, the movement should be natural and stable. Don’t be heavy or anxious to avoid broken fibers, bevels, burrs, cracks and other bad end faces. In addition, learn to "play the piano", rationally allocate and use your right hand fingers, so that they correspond and coordinate with the specific parts of the cutter, and improve the cutting speed and quality.
Beware of contamination on the end surface. The heat shrinkable sleeve should be inserted before stripping, and it is strictly forbidden to penetrate after the end surface is prepared. The time of cleaning, cutting and welding of bare fibers should be closely connected, and the interval should not be too long, especially the prepared end faces should not be placed in the air. Handle with care when moving to prevent rubbing against other objects. During the splicing, the "V" groove, pressure plate and blade of the cutter should be cleaned according to the environment, and the end surface should be prevented from being polluted.
Fiber splicing
Fiber splicing is the central link of the splicing work, so high-performance fusion splicing machines and scientific operations during the splicing process are very necessary.
(1) Selection of welding machine
The selection of the fusion splicer should be equipped with fusion splicing equipment with appropriate battery capacity and precision according to the requirements of the optical cable project.
(2) Parameter setting of fusion splicer
According to the material and type of optical fiber before welding, set the key parameters such as the optimal pre-melting main melting current and time, and the amount of fiber feeding. During the welding process, the "V" groove, electrode, objective lens, welding chamber, etc. of the welding machine should be cleaned in time, and any bad phenomena such as bubbles, too thin, too thick, virtual melting, separation, etc. should be observed during the welding at any time, and attention should be paid to the tracking and monitoring results of OTDR. Analyze the causes of the above adverse phenomena in a timely manner and take corresponding improvement measures. If virtual fusion occurs many times, check whether the materials and models of the two optical fibers to be welded match, whether the cutter and the fusion splicer are polluted by dust, and check the oxidation status of the electrodes. If there is no problem, the fusion current should be increased appropriately.
Disc fiber
Disk fiber is a technology, but also an art. The scientific fiber coiling method can make the optical fiber layout reasonable, the additional loss is small, can withstand the test of time and harsh environment, and can avoid the phenomenon of fiber breakage caused by extrusion.
(1) Disk fiber rules
The fiber is coiled in units along the loose tube or the branching direction of the optical cable. The former is applicable to all splicing projects; the latter is only applicable to the end of the main optical cable, and has one input and multiple outputs. Most of the branches are small logarithmic optical cables. The rule is to reel the fiber once after splicing and heat-shrinking one or several fibers in loose tubes, or fibers in a split direction cable. Advantages: It avoids the confusion of optical fibers between loose tubes of optical fibers or between different branch optical cables, making it reasonable in layout, easy to reel and dismantle, and easier to maintain in the future.
(2) The method of disk fiber
First the middle and then both sides, that is, first place the heat-shrinkable sleeves in the fixing groove one by one, and then process the remaining fibers on both sides. Advantages: It is beneficial to protect the fiber joints and avoid possible damage caused by the fiber coil. This method is often used when the space reserved for the optical fiber is small and the optical fiber is not easy to coil and fix.
According to the actual situation, a variety of graphic disk fibers are used. According to the length of the remaining fiber and the size of the reserved disk space, it will be coiled naturally according to the trend. Do not pull it forcefully. You should flexibly use various graphics such as circle, ellipse, "CC" and "~" (note that R≥4cm), and make the fiber as large as possible. Maximize the use of reserved disk space and effectively reduce the additional loss caused by disk fiber.
Quality Assurance of Optical Cable Connection
It is of great significance to strengthen the monitoring of OTDR to ensure the quality of optical fiber fusion, reduce the additional loss caused by the fiber coil and the possible damage to the optical fiber caused by the sealing box. During the entire follow-up work, the OTDR four monitoring procedures must be strictly implemented:
(1) Real-time tracking and monitoring of each core fiber during the fusion splicing process to check the quality of each splicing point;
(2) After each fiber reel, conduct a routine inspection of the reeled fiber to determine the additional loss caused by the reel;
(3) Before sealing the splicing box, conduct a unified test on all optical fibers to find out whether there is any missing test and whether there is any extrusion on the optical fiber and the connector between the reserved optical fiber discs;
(4)After sealing the box, perform a final inspection on all optical fibers to check whether the sealing box has damaged the optical fiber.
