# What is "fiber embrittlement"?

**URL:** <https://forum.ofscn.net/t/what-is-fiber-embrittlement/3142>\
**Category:** OFSCN Technical Knowledge Base\
**Created:** [October 23, 2026, 5:09am UTC](https://forum.ofscn.net/t/what-is-fiber-embrittlement/3142 "2026-10-23T05:09:21Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![VoidWalker](https://forum.ofscn.net/letter_avatar_proxy/v4/letter/v/848f3c/32.png) [@VoidWalker](https://forum.ofscn.net/u/VoidWalker)\
**Post date:** [October 23, 2026, 5:09am UTC](https://forum.ofscn.net/t/what-is-fiber-embrittlement/3142/1 "2026-10-23T05:09:21Z")

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Will optical fibers become as brittle as cookies and break upon touch after long-term use in a 300-degree environment?

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**Author:** ![OFSCN\_Tech\_Expert](https://forum.ofscn.net/user_avatar/forum.ofscn.net/ofscn_tech_expert/32/199_2.png) [@OFSCN\_Tech\_Expert](https://forum.ofscn.net/u/OFSCN_Tech_Expert)\
**Post date:** [October 23, 2026, 5:10am UTC](https://forum.ofscn.net/t/what-is-fiber-embrittlement/3142/2 "2026-10-23T05:10:36Z")

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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:

1. **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.
2. **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.
3. **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:

- [OFSCN® 300℃ SM Polyimide Optical Fiber](https://www.ofscn.org/optical-fibers/polyimide-coated-sm-300.html)

**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

 ![OFSCN® 300℃ SM Polyimide Optical Fiber](https://forum.ofscn.net/uploads/default/original/1X/ce90be3e4b9bb517d521f23c595dfb4d1985b218.jpeg)  
 ![OFSCN® 300℃ SM Polyimide Optical Fiber](https://forum.ofscn.net/uploads/default/original/1X/57868fea66e7d6acd9987d1446decaffc6e49e6c.jpeg)