Most Common Problems During Grinding & Polishing of Fiber Optic Connector

Why Grinding & Polishing?

As one of the most important optical passive components in optical fiber system, optical fiber connector requires lower insertion loss and higher return loss in performance to improve the reliability of optical fiber transmission system. To evaluate the quality of optical fiber connectors, it is necessary to measure the shape parameters of the connector pin body end face after grinding and polishing, including three important parameters: radius of curvature, vertex offset and core depression. Only by keeping the shape parameters of the end face within a certain range can the optical fiber maintain good physical contact; In addition, try to remove the deterioration layer on the end face of the optical fiber and test whether the end face of the optical fiber has scratches or other stains. Finally, the performance of low insertion loss and high return loss should be satisfied. Therefore, the grinding and polishing process of optical fiber connector is very important to improve its optical performance.

Problems May Happen During Grinding & Polishing

Fiber broken

Cause 1: The protective glue on the plug 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, resulting in brittle fracture.

Cause 2: The grinding machine rotates too fast or the grinding process is not smooth, and the stress on the optical fiber is too large and uneven, resulting in fiber cracking.

Black & white spots

Black spots and white spots are pits. Black spots are deep pits and white spots are shallow pits.

Cause 1: D1 abrasive paper cutting force is not enough, or the previous layer is too rough to repair.

Cause 2: There are large particles of impurities in D1 or polishing sheet, resulting in optical fiber damage and pits

Cause 3: D1 or polishing plate coating falls off and is mixed between the insert and abrasive plate. The optical fiber has pits due to excessive local stress

Cause 4: The grinding machine is not running smoothly, or impurities are mixed in the grinding process, resulting in pits in the optical fiber due to local excessive stress

Black border

The dark black ring appears at the connection between the optical fiber and the ceramic. In essence, the edge of the optical fiber and the epoxy adhesive are broken deeply, which should reflect different light and become black

Cause 1: D1 The grinding force is too large, which causes the fiber edge and epoxy adhesive to crack, and the polishing cannot be repaired

Cause 2: The powder of the D1 abrasive strip falls off seriously, resulting in rolling grinding, resulting in cracking of the edge of the optical fiber and epoxy adhesive, which cannot be repaired after polishing

Cause 3: D1 The grinding force is too weak, and the edge pits caused by the previous grinding cannot be completely repaired, nor can polishing be repaired.

Cause 4: Grinder speed is too fast or pressure is too high

Scorch

The end face of the plug is stuck with a thick layer of material (abrasive and rubber mixture), and the optical fiber is basically invisible

Cause 1: The grinding pressure is large, and the hardness of the rubber pad is high. Under the grinding pressure, the grinding plate is coated at the later stage of grinding. The abrasive on the surface of the layer is greatly reduced, and the cutting force is seriously reduced

Cause 2: The softening point of the coating is low, the adhesive is sticky under the action of abrasive force, and a large amount of abrasive debris is stuck on the surface of the coating, which is finally transferred to the end face of the insert, causing burning

Scratch

Black straight line or white straight line appears on the end face of the insert. The black straight line is a deep scratch, and the white straight line is a shallow scratch

Cause 1: There are abnormal large particles such as impurities in the abrasive plate, or the surface of the abrasive plate is uneven, resulting in large local stress on the optical fiber and large cutting depth, resulting in scratches

Cause 2: The grinding pressure is small, and the grinding machine operates unevenly, resulting in excessive local stress and large cutting depth, resulting in scratches

Cause 3: The lapping plate has the phenomenon of cutting edge, the surface is hard and not flat enough, resulting in excessive local stress and large cutting depth, resulting in scratches

Cause 4: Due to the abnormality of the polishing sheet, the silicon dioxide particles in the polishing sheet agglomerate, or the polishing sheet has no cutting force