Fiber Optic Connector Polishing SOP 

Connector Types: SC, LC, FC, ST, MU (UPC & APC)
Fiber Type: Single-Mode and Multi-Mode
Standards: IEC 61755 / Telcordia GR-326

Objective:
Achieve high-quality ferrule end-faces with:

• Low Insertion Loss (IL ≤ 0.35 dB)

• High Return Loss (RL ≥ 50 dB for UPC, ≥ 60 dB for APC)

• Mirror-like surface finish (Ra ≤ 0.03 µm)

• Uniform fiber height and correct apex geometry

1️⃣ Tools & Consumables

Note: Rubber pads are slightly compliant, reducing the risk of ferrule edge chipping and ensuring uniform polishing across the ferrule face.

2️⃣ Polishing Workflow

Step 1 – Epoxy Removal & Initial Flattening

• Abrasive: SiC or coarse Diamond

• Grit / Micron: 30 µm

• Pad: Rubber Pad

• Lubrication: DI Water

• Goal: Remove epoxy flash, level ferrule end-face

• Target Ra: 0.8–1.2 µm

• Time: 30–60 sec

Inspection: Ferrule surface flush or slightly recessed; no epoxy beads.

Step 2 – Geometry Shaping & Apex Control

• Abrasive: Diamond or fine SiC

• Grit / Micron: 9–3 µm

• Pad: Rubber Pad

• Lubrication: DI Water

• Goal: Establish correct ferrule radius, apex, and fiber height uniformity

• Target Ra: 0.2–0.4 µm

• Time: 30–60 sec

Inspection: Apex symmetrical, minimal scratches, fiber height uniform across ferrule.

Step 3 – Intermediate Smoothing

• Abrasive: Diamond or Aluminum Oxide (Al₂O₃)

• Grit / Micron: 1–0.5 µm

• Pad: Rubber Pad

• Lubrication: DI Water or light slurry

• Goal: Remove residual scratches, prepare surface for final polish

• Target Ra: 0.03–0.05 µm

• Time: 30–60 sec

Step 4 – Final Optical Finish

• Abrasive: SiO₂ or CeO₂ sub-micron

• Grit / Micron: 0.05–0.5 µm

• Pad: Rubber Pad

• Lubrication: Slurry or DI Water

• Goal: Achieve mirror finish for optical-grade performance

• Target Ra: ≤0.03 µm

• Time: 30–60 sec

Inspection: Surface glossy, defect-free; ready for optical testing.

3️⃣ APC Connector Special Notes

• Final polish angle: 8°

• Fiber protrusion: Ensure proper angle with polishing jig

• Inspection: Check apex angle and RL ≥ 60 dB

4️⃣ Inspection Criteria

5️⃣ Troubleshooting Guide

6️⃣ Best Practices with Rubber Pad

• Rubber pad reduces risk of over-polishing edges compared to rigid glass/ceramic pads.

• Use light, consistent pressure; excessive force can deform pad and ferrule.

• Always clean pads, films, and ferrules between steps.

• Follow progressive micron sequence to prevent scratches.

• APC connectors require an 8° angled final polish.

• Record Ra, fiber height, IL, RL, and apex geometry for traceability.

7️⃣ Quick Reference Polishing Sequence (Rubber Pad)

✅ Outcome: Using a rubber pad ensures uniform ferrule polishing, reduced edge chipping, and optimized surface finish while maintaining compliance with IEC 61755 and Telcordia GR-326.