Fusion Splice Loss Evaluation

For fusion splice loss assessment, some fusion splicers use a cross-section alignment system that images the fiber and measures geometric parameters. Depending on the splice and its loss estimation algorithm, the resulting splice loss may differ considerably from the actual splice loss.

Using an Optical Time Domain Reflectometer (OTDR)

Optical Time Domain Reflectometer (OTDR: Optical Time Domain Reflectometer), also known as backscattering instrument, its principle is: when transmitting light pulses into the optical fiber, due to the trace light scattered in the optical fiber, after returning to the light source side, the time base can be used To observe the degree of reflected light return.

Since the mode field diameter of a fiber affects its backscatter, the fibers on either side of the splice may backscatter differently, masking the true loss of the splice. If the loss of the joint is measured from two directions, and the average value of these two results is obtained, the human factor error of the one-way OTDR measurement can be eliminated.

However, in most cases the operator only measures the splice loss in 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 larger than the intrinsic splice loss itself.

Fiber Splice Loss

How to reduce fiber splicing loss

1. Try to use the same batch of high-quality brand-name bare fibers on a line. For the same batch of optical fibers, the mode field diameters are basically the same. Splicing at this break point minimizes the effect of mode field diameter on fiber splice loss.

Therefore, optical cable manufacturers are required to use the same batch of bare fibers to produce continuously according to the required length of optical cable, number them sequentially on each reel and distinguish A and B ends, and do not skip numbers. When laying optical cables, they must be laid out along the determined routing sequence according to the number, and ensure that the B end of the front optical cable is connected to the A end of the next optical cable, so as to ensure that the connection can be welded at the disconnection point, and the fusion loss value can be reached. minimum.

2. Optical cable erection is carried out according to the requirements. In the construction of optical cable laying, it is strictly forbidden to make small circles, folds and twists on optical cables. More than 80 people must be employed for 3km optical cables, and more than 100 people must be employed for 4km optical cables, and 6-8 walkie-talkies should be equipped; The method of laying the cable forward and then with the heel on the shoulder" can effectively prevent the occurrence of back buckle.

The traction force should not exceed 80% of the allowable optical cable, and the maximum instantaneous traction force should not exceed 100%, and the traction force should be added to the strength member of the optical cable. The laying of the optical cable should strictly follow the construction requirements of the optical cable, so as to minimize the probability of damage to the optical fiber 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. Most of the splicing is automatic splicing by fusion splicing machines, but the level of splicing personnel directly affects the size of the splicing loss. Splicing personnel should perform splicing in strict accordance with the optical fiber fusion splicing process flow chart, and during the splicing process, use OTDR to test the splicing loss of the splicing point while splicing. Those that do not meet the requirements should be spliced again. For the point with a large splice loss value, the number of repeated splices should be 3-4 times.

4. The optical cable connection 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 optical cable connection parts, tools and materials should be kept clean, and the optical fiber connector must not be damp. The optical fiber to be cut must be clean and free of dirt. thing. After cutting, the optical fiber should not be exposed to the air for too long, especially in a dusty and humid environment.

5. Choose a high-precision optical fiber end face cutter to prepare the end face of the optical fiber. The quality of the end face of the optical fiber directly affects the size of the fusion loss. The cut optical fiber should be a flat mirror surface without burrs and defects.

The axial 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 the fusion splices that cannot be tested by OTDR (that is, the blind spots of OTDR test) and the maintenance and repair of optical fibers.

6. The fusion splicer should be used correctly. The function of the fusion splicer is to fuse two optical fibers together, so the correct use of the fusion splicer is also an important measure to reduce the loss of optical fiber splicing. Correctly and reasonably set the fusion splicing parameters, pre-discharge current, time and 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 clamps, mirrors and V-shaped grooves Removal of dust and fiber debris inside.

Before each use, the fusion splicer 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 indoors and outdoors in winter), according to the air pressure, temperature, humidity and other environmental conditions at that time , reset the discharge voltage and discharge position of the fusion splicer, and reset the v-groove driver.