(1) Schizofibrillation

Some or all of the optical fibers are deeply fractured, the fracture is neat and smooth, and the end detector shows large black block, as shown in Figure a.

  

The causes are as follows

A: The protective glue on the insert head is too large, too thick or too small, the whole piece falls off during grinding, and the local stress of the optical fiber is too large, which leads to brittle fracture.

B: If the grinding machine speed is too fast or the grinding process is not stable, the stress of the optical fiber is too large and uneven, leading to fiber cracking.

(2) Black and white spots

Black and white dots are pits, black dots are deep pits, and white dots are shallow pits, as shown in figures B and C.

  

The causes are as follows

A: D1 abrasive paper cutting force is not enough, or the last one is too rough to repair;

B: There are large particle impurities in D1 or polishing pad, leading to fiber damage and pits;

C: The coating of D1 or polishing pad falls off and is mixed between the insert and the grinding pad, and the optical fiber has pits due to excessive local stress;

D: The grinding machine does not run smoothly, or impurities are mixed in the grinding process, which leads to pits in the optical fiber due to excessive local stress.

(3) Black edge

The dark black ring appears at the joint of optical fiber and ceramic, which is actually due to the deep fracture of the edge of optical fiber and epoxy adhesive, the difference of reflection and blackening, as shown in Figure D.

  

A: D1 grinding force is too large, resulting in fiber edge and epoxy resin cracking, polishing can not be repaired;

B: The powder of D1 lapping plate fell off seriously, resulting in rolling lapping, causing the edge of optical fiber and epoxy resin cracking, and polishing can not be repaired;

C: D1 grinding force is too weak, the edge pits caused by the previous grinding can not be completely repaired, and polishing can not be repaired;

D: The speed of the grinder is too fast or the pressure is too high.

(4) Scorch

A thick layer of material (mixture of wear debris and glue) is stuck on the end face of the insert core, and the optical fiber can hardly be seen, as shown in Fig. E.

  

A: When the grinding pressure is large, the hardness of the rubber pad is high. Under the action of the grinding pressure, the abrasive on the coating surface is greatly reduced, and the cutting force is seriously reduced;

B: The softening point of the coating is low, the adhesive is sticky under the action of grinding force, and a large amount of wear debris is adhered on the surface of the coating, which is eventually transferred to the end face of the core insert, resulting in scorching phenomenon.

(5) Scratches

There are black lines or white lines on the end face of the insert. The black lines are deep scratches and the white lines are shallow scratches, as shown in Figure F.

  

A: There are abnormal large particles such as impurities in the lapping plate, or the surface of the lapping plate is not flat, which leads to large local stress and large cutting depth of the optical fiber, resulting in scratches;

B: Low grinding pressure and unstable operation of the grinder lead to excessive local stress and large cutting depth, resulting in scratches;

C: There is a phenomenon of edge cutting, the surface is very hard and not smooth enough, which leads to excessive local stress and large cutting depth, resulting in scratches;

D: It is caused by abnormal polishing, agglomeration of silica particles, or no cutting force.

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