Fiber Cleaving and Stripping Technique — Electronics / Telecom Technician

Objective. Students will strip, clean, and cleave multimode and singlemode fiber to produce a flat, perpendicular end-face with no hackle, lip, or chip, verified by microscope inspection.

Why End-Face Quality Matters

In a fiber optic link, light travels from core to core across every splice and connector. Any imperfection at the fiber end-face scatters or reflects light, adding insertion loss and return loss to the link. A fiber that is poorly cleaved before splicing or termination will degrade the entire channel, sometimes enough to fail a loss budget test. Producing a flat, perpendicular, defect-free end-face every time is one of the most fundamental hands-on skills an installer must master.

The Strip–Clean–Cleave Sequence

The sequence never varies. Skipping or reversing steps is a leading cause of defects.

Step 1 – Jacket Stripping. The outer jacket (usually 900 µm tight-buffer or 3 mm distribution cable) is removed first using a jacket striper sized for the cable. Hold the cable firmly, close the striper jaws, and pull toward the fiber end in one smooth motion. Avoid rocking or twisting, which can nick the buffer beneath.

Step 2 – Buffer Stripping. The 250 µm acrylate coating (primary buffer) is removed with a Miller-style buffer striper. Set the striper to the correct aperture for 250 µm coated fiber. Strip in short, overlapping pulls of about 25–30 mm. Do not angle the tool; keep it perpendicular to the fiber axis. The bare glass cladding is 125 µm in diameter—thinner than a human hair—and will fracture if bent or pinched.

Step 3 – Cleaning. Fold a lint-free wipe once and dampen one section with 99% isopropyl alcohol (IPA). Grip the bare glass between the dampened section and the dry section, then draw the fiber through in a single pass from coated end toward the tip. Never reuse the same wipe surface or wipe back and forth, as this re-deposits contamination. Allow one second for the IPA to evaporate. Contamination on bare glass is a leading cause of poor cleaves and splice failures.

Step 4 – Cleaving. Place the cleaned fiber in the precision blade cleaver. Multimode fiber (50/125 µm or 62.5/125 µm) and singlemode fiber (9/125 µm) both use the same basic technique, though cleaver tension settings may vary by manufacturer. Score the glass by lowering the blade lightly onto the fiber surface—this creates a controlled fracture initiation point. Apply the specified tension (consult the cleaver's manufacturer guide) and allow the fiber to fracture completely. The controlled tensile break propagates the crack across the entire cross-section, producing a flat mirror surface when done correctly.

Recognizing Acceptable and Defective Cleaves

Inspect every cleave under a calibrated fiber inspection microscope at sufficient magnification to see the 125 µm cladding clearly. An acceptable cleave shows:

A mirror-flat surface with no surface texture
An angle of ≤ 1° from perpendicular (cleaver specifications typically state the angle tolerance)
No chips, cracks, hackle, or lips

Hackle – A rough, river-pattern texture caused by the fracture running out of control. Causes: insufficient cleave tension, contamination, or a worn cleaver blade.

Lip – A protruding ledge at the edge of the end-face. Causes: too little tension or a dull blade.

Angle – The end-face tilts from perpendicular. Causes: fiber not seated flat in the cleaver groove, or uneven blade contact.

Chip – A piece of glass missing from the edge. Causes: blade impact angle too steep, contamination, or excessive tension.

Crack – A subsurface fracture that extends back into the fiber. Causes: bending stress during cleaving or a contaminated scoring point.

When a defect is identified, strip back past the damage, re-clean, and recleave. Never attempt to re-cleave a fiber end that is already cleaved—stripping and starting over is the correct response.

Safety Rules for This Lab

Fiber slivers are the primary hazard. Bare glass offcuts are nearly invisible, extremely sharp, and can penetrate skin and eyes with little force. Follow these rules without exception:

Wear safety glasses at all times from the moment any stripping begins.
Never touch bare cleaved fiber with bare fingers.
Place every cleaved offcut and defective fiber piece immediately into the designated sharps container. Never place offcuts on the workbench, on clothing, or in a trash can.
No food or drink in the lab. Fiber slivers can contaminate food and cause internal injury if swallowed.
IPA is flammable: keep it away from open flame and heat sources; ensure adequate ventilation.
Log all cleaves and pass/fail results on your lab sheet as you work. This is your record and your instructor's verification tool.

Key terms8

End-faceThe flat, polished or cleaved tip of the optical fiber through which light enters or exits; quality directly affects insertion loss.

Primary buffer (coating)The 250 µm acrylate layer applied directly over the 125 µm glass cladding to protect the fiber from microbending and moisture.

Precision cleaverA tool that scores a controlled initiation point on the glass surface and applies tension to propagate a flat fracture across the fiber cross-section.

HackleA rough, branched texture on the cleaved end-face caused by an uncontrolled fracture, indicating insufficient tension or a worn blade.

LipA small protruding ledge at the perimeter of the cleaved end-face, caused by insufficient cleave tension or a dull cleaver blade.

Insertion lossThe reduction in optical power caused by a connector, splice, or other discontinuity in the fiber link, measured in decibels (dB).

Cleave angleThe deviation of the cleaved end-face from a perfect 90° perpendicular to the fiber axis; typically must be ≤ 1° for acceptable splicing.

Sharps containerA puncture-resistant, labeled disposal container used exclusively for fiber offcuts and other sharp glass waste to prevent injury.

In class: Step-by-step instructor demonstration of the strip–clean–cleave sequence using a jacket striper, buffer striper, lint-free wipes, isopropyl alcohol, and a precision cleaver; students observe and take notes before handling tools. · Supervised practice: each student performs 10 complete strip-clean-cleave cycles on 250-µm coated fiber, inspecting each cleave under the scope and recording pass/fail on a tally sheet; instructor provides real-time corrective feedback. · Defect analysis exercise: instructor presents six pre-cleaved fiber ends (hackle, lip, angle, crack, chip, good) under the scope; students identify the defect name, probable cause, and corrective technique on a worksheet.
Materials: 250-µm coated fiber spool (multimode and singlemode), jacket striper, Miller buffer striper, precision fiber cleaver (blade-style), lint-free wipes, isopropyl alcohol, fiber inspection scope, sharps container, lab log sheets
Check: Student produces 3 consecutive acceptable cleaves (flat, perpendicular, defect-free under scope inspection) without assistance; instructor signs lab sheet confirming pass.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.