Why can’t fiber optic cables be cut with scissors?
In the fields of optical engineering and fiber optic communications, “why fiber optic cables cannot be cut with scissors” is a fundamental question involving material physics and fracture mechanics.
1. Conflict Between Material Properties and Mechanical Performance
The primary component of optical fibers is high-purity fused silica glass (i.e., silicon dioxide, chemical formula \text{SiO}_2), which typically has a Mohs hardness between 5.5 and 6.5. Fused silica glass belongs to the category of typical brittle materials.
Ordinary scissors are designed to cut ductile materials like paper, fabric, plastic, or some ductile metals. When the two blades of scissors close, they apply intense shearing force to the target object.
- Consequences of Using Scissors：Attempting to cut a silica optical fiber with scissors will not result in a clean break. The powerful localized compression and shear forces will cause the silica glass to undergo irregular shattering, chipping, and generate numerous microcracks. This not only fails to produce a usable fiber end face but also instantly dulls or damages the metal blades of the scissors.
2. Different Fracture Mechanics Mechanisms: Shearing vs. Stress Propagation from Scratching
To obtain a high-quality fiber end face for optical communication or fiber optic sensing, specialized “Fiber Cleavers” must be used, which operate based on the “Scribe and Cleave” mechanism in fracture mechanics:
- Step 1 (Scratching)：The cleaver uses an extremely hard blade (typically made of diamond or tungsten carbide) to create a very slight, micron-level scratch perpendicular to the fiber surface.
- Step 2 (Applying Tension/Bending)：The cleaver’s mechanical structure applies axial tensile stress to the fiber, or bending stress via a bending pad. The previously created scratch acts as a stress concentration point, allowing a transverse crack to propagate uniformly across the entire fiber cross-section in an extremely short time.
- Result：The resulting end face is an almost perfect mirror finish, perpendicular to the fiber axis (typically with a cleaving angle less than 0.5^\circ).
3. Impact on Optical Transmission
The core diameter of single-mode optical fibers is extremely small. For example, in standard single-mode fibers, the silica cladding diameter is 125\ \mu\text{m}, while the core diameter, through which the optical signal transmits, is only about 9\ \mu\text{m}.
If scissors are used, resulting in a broken, uneven, or angled end face:
- Fusion Splicing Failure：During fiber splicing, the splicer will report an error because it cannot align the fiber end faces. Furthermore, the broken fragments will contaminate the splicer’s electrodes and V-groove.
- Extremely High Loss：Due to the uneven end face, the optical signal will experience severe insertion loss and return loss when passing through this interface, preventing normal optical signal transmission or rendering precision devices like Fiber Bragg Gratings inoperable.
OFSCN® Technical Tip
It is important to clarify that common scissors, wire strippers, and fiber cleavers are general fiber preparation tools and are not part of Beijing Dacheng Yongsheng Technology Co., Ltd.'s (OFSCN®) core product line.
However, as a professional manufacturer specializing in Fiber Bragg Grating (FBG) sensitization and optical cable structure design, Beijing Dacheng Yongsheng Technology Co., Ltd. offers a variety of high-quality fused silica optical fiber products. When performing end-face treatment or splicing on these fibers, it is essential to use a professional fiber cleaver to ensure end-face quality:
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OFSCN® G.652D Optical Fiber：This is a standard single-mode fiber with a cladding diameter of 125\ \mu\text{m} and a coating diameter of 255\ \mu\text{m}.
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OFSCN® 120℃ SM High-temperature Optical Fiber：This is a single-mode fiber resistant to high temperatures up to 120^\circ\text{C}. It also features a standard 125\ \mu\text{m} cladding, with an outer layer coated in high-temperature-resistant polyacrylate. For such specialty optical fibers, precise cutting with a professional cleaver is also required for end-face treatment to ensure excellent transmission and splicing performance.
