Loss occurs when light is transmitted in an optical fiber, and this loss is mainly caused by the transmission loss of the optical fiber itself and the splice loss at the optical fiber joint. So, how can we reduce the loss of fiber splicing? This is the question we need to investigate today! Let's go and find out together!
How to measure fiber splice loss
1. Evaluation of welding joint loss
Some fusion splicers use a section alignment system for imaging and measuring geometric parameters of optical fibers. By viewing the fiber from two perpendicular directions, the computer processes and analyzes the image to determine cladding shifts, core distortion, changes in fiber outer diameter, and other key parameters that are used to evaluate splice losses. The splice loss determined by the splice and its loss estimation algorithm may differ considerably from the true splice loss.
2. Use Optical Time Domain Reflectometry (OTDR)
Optical Time Domain Reflectometer (OTDR: Optical Time Domain Reflectometer) is also known as backscattering instrument. to see how much light is reflected back.
Since the fiber's mode field diameter affects its backscatter, the fibers on either side of the splice may experience different backscatter, obscuring the true loss of the splice. If the loss of the splice is measured from both directions, and the two results are averaged, the artifact of a unidirectional OTDR measurement can be eliminated.
However, in most cases the operator measures splice loss from only one direction, and the results are not very accurate, in fact, the loss due to fibers with mismatched mode field diameters can be 10 times greater than the inherent splice loss itself.
Fiber splice loss
How to reduce fiber splice loss
1. Try to use the same batch of high-quality brand-name bare fibers on a line. For the same batch of fibers, the mode field diameters are basically the same. After the fiber is disconnected at a certain point, the mode field diameters between the two ends can be regarded as the same, so Splicing at this break point minimizes the effect of the mode field diameter on the fiber splice loss.
Therefore, fiber optic cable manufacturers are required to use the same batch of bare fibers, continuously produce them according to the required length of the fiber optic cable, and sequentially number and distinguish the A and B ends on each reel, without skipping numbers. When laying the optical cable, it must be laid out according to the number along the determined routing sequence, and ensure that the B end of the optical cable in the front coil is connected to the A end of the optical cable in the next coil, so as to ensure that the connection can be spliced at the disconnection point, and the splice loss value reaches minimum.
2. Optical cable installation shall be carried out according to the requirements. During the optical cable laying construction, it is strictly forbidden to make small circles, fold and twist the optical cable. More than 80 people must construct the optical cable for 3km, and more than 100 people must construct the 4km cable, and be equipped with 6-8 walkie-talkies; The method of laying out the cable by walking forward and heel, and the shoulder of the optical cable can effectively prevent the occurrence of back buckle.
The traction force shall not exceed 80% of the allowable optical cable, and the maximum instantaneous traction force shall not exceed 100%. The traction force should be added to the strength member of the optical cable. The optical cable should be laid in strict accordance with the construction requirements of the optical cable, so as to minimize the probability of the optical fiber being damaged during the construction of the optical cable, and avoid the increase of the fusion loss caused by the damage of the optical fiber core.
3. Select experienced and well-trained optical fiber splicing personnel for splicing. At present, most of the fusion splicing is automatically spliced by the fusion splicer, but the level of the splicing personnel directly affects the size of the splicing loss. The splicing personnel should conduct splicing in strict accordance with the optical fiber splicing process flow chart, and during the splicing process, OTDR should be used to test the splice loss of the splicing point. Those that do not meet the requirements should be spliced again. For the point with a large splicing loss value, the number of repeated splicing should be 3-4 times.
4. The splicing optical cable should be carried out in a clean environment. It is strictly forbidden to operate in the open air in a dusty and humid environment. The splicing parts, tools and materials of the optical cable should be kept clean, and the optical fiber joints should not be damp. The optical fibers to be cut must be clean and free of contamination. thing. After cutting, the fiber must not be exposed to air for too long, especially in dusty and humid environments.
5. Use a high-precision fiber end face cutter to prepare the fiber end face. The quality of the fiber end face directly affects the size of the splice loss. The cut fiber should be a flat mirror surface, without burrs and defects.
The inclination angle of the fiber end face should be less than 1 degree. A high-precision fiber end face cutter not only improves the success rate of fiber cutting, but also improves the quality of the fiber end face. This is especially important for fusion splices that cannot be tested by the OTDR (ie, blind spots in the OTDR test) and fiber maintenance and repair.
6. The fusion splicer should be used correctly. The function of the fusion splicer is to splicing two optical fibers together, so the correct use of the fusion splicer is also an important measure to reduce the optical fiber splice loss. Correctly and reasonably set the splicing parameters, pre-discharge current, time, main discharge current, main discharge time, etc. according to the fiber type, and remove the dust in the fusion splicer in time during and after use, especially the fixture, mirrors and v-groove Removal of dust and fiber debris inside.
Before each use, the welding machine should be placed in the welding environment for at least fifteen minutes, especially in places where the placement and use environment are quite different (such as indoor and outdoor in winter). , reset the discharge voltage and discharge position of the fusion splicer, and reset the v-slot driver.
As for how to reduce the loss of optical fiber fusion, today Xiaobian will answer the questions for you first. Of course, the above are relatively basic optical fiber knowledge, and once the optical fiber cable is ordered, the transmission loss of the optical fiber itself is basically determined. The splice loss at the fiber optic connector is related to the fiber itself and on-site construction. Efforts to reduce the splice loss at the optical fiber joint can increase the optical fiber relay amplification transmission distance and improve the attenuation margin of the optical fiber link.
