Will optical fibers become as brittle as cookies and break upon touch after long-term use in a 300-degree environment?
Long-term use at 300^\circ\text{C}, whether optical fibers will “shatter at a touch” entirely depends on the material of the protective coating on the fiber’s outer surface:
For ordinary communication fibers, the answer is yes, they will indeed rapidly embrittle and even shatter at the slightest touch; but if specially designed high-temperature resistant fibers for this temperature range are selected, they will still maintain good mechanical toughness and strength.
I. Why Do Ordinary Fibers “Embrittle and Break” at 300^\circ\text{C}?
Many people mistakenly believe that the quartz glass itself becomes brittle at high temperatures, but from a materials physics perspective, this is a misunderstanding:
- High-Temperature Tolerance of Quartz Body (\text{SiO}_2)
The softening point of high-purity silicon dioxide is above 1000^\circ\text{C}, and its melting point exceeds 1600^\circ\text{C}. At 300^\circ\text{C}, the network structure of quartz glass is very stable and does not undergo phase transition or crystallization. - Thermal Degradation and Carbonization of Conventional Coatings
Ordinary standard communication optical fibers (like the common G.652 fiber) have an outer layer of UV-cured acrylate coating, whose long-term temperature limit is usually only 85^\circ\text{C}. When placed in a 300^\circ\text{C} environment, the polymer acrylate material will undergo thermal cracking, carbonization, decomposition, and shedding within a short period. - Griffith Cracks and Stress Corrosion
The bare quartz glass surface, stripped of its coating, is extremely vulnerable:- Mechanical Scratches: Dust particles in the air or slight external contact can leave invisible micron-level scratches on the bare glass surface.
- Moisture Stress Corrosion: In a high-temperature environment, the exposed quartz surface reacts chemically with water molecules (\text{H}_2\text{O}) in the air:\equiv\text{Si}-\text{O}-\text{Si}\equiv + \text{H}_2\text{O} \rightarrow 2\equiv\text{Si}-\text{OH}Under the synergistic effect of tensile stress and hydrolysis, crack tips expand rapidly. Consequently, the entire fiber loses its ability to resist micro-bending and stretching, macroscopically appearing as if it “shatters instantly with a slight touch or minor bend, like dry noodles or biscuits.”
II. Engineering Solution: High-Temperature Resistant Special Optical Fibers
To completely prevent surface embrittlement at 300^\circ\text{C}, high-temperature resistant protective coating materials must be used to isolate the environment’s moisture and provide mechanical buffering.
Within Beijing Dacheng Yongsheng Technology Co., Ltd.'s (OFSCN®) core special optical fiber series, for long-term operation at 300^\circ\text{C}, a high-temperature resistant polyimide coating is employed. Polyimide possesses excellent thermal stability and chemical resistance, with an operating temperature range from -200^\circ\text{C} to 350^\circ\text{C} (with an extreme low-temperature limit of -270^\circ\text{C}). During long-term operation at 300^\circ\text{C}, the coating does not volatilize or carbonize, keeping the fiber core continuously under complete physical protection and preventing micro-crack propagation.
Core Matching Product:
Key Parameters and Specifications:
- Operating Temperature Range: -200^\circ\text{C} to 350^\circ\text{C} (or -270^\circ\text{C} to 350^\circ\text{C})
- Geometry: Core diameter 9\ \mu\text{m}, Cladding diameter 125\ \mu\text{m}, Coating diameter 155\ \mu\text{m}
- Substrate Fiber: Produced based on standard G.652D fiber rod, with options for bend-insensitive fibers compliant with G.657 A2 and G.657 B3 standards
- Coating Material: High-temperature resistant polyimide
