In a liquid nitrogen (-196℃) environment, did the jumper wire become brittle or shatter directly?
In a liquid nitrogen ( -196\ ^\circ\text{C} ) environment, ordinary fiber optic patch cords (such as standard single-mode patch cords with common PVC outer jackets, aramid yarn reinforcement, and standard acrylate coating) first undergo extreme “cryogenic embrittlement” and then “shatter directly” due to internal thermal stress or any minor external force disturbance.
The specific physical mechanisms and material behaviors are as follows:
1. “Glass Transition” and Embrittlement of Materials
The protective sheaths of ordinary fiber optic patch cords typically use polymers like PVC or LSZH, while the fiber coating is standard acrylate. These polymeric materials have specific glass transition temperatures (T_g), usually between 0\ ^\circ\text{C} and -50\ ^\circ\text{C}.
When the temperature drops rapidly to -196\ ^\circ\text{C} (liquid nitrogen), these materials quickly cross their T_g point and enter a highly brittle “glassy state.” At this point, the originally elastic and tough plastic sheath and coating become as fragile as thin ice, losing any ability to resist bending or impact.
2. Direct Shattering Caused by Massive Thermal Stress Mismatch
The thermal expansion coefficient of fused silica optical fiber itself is extremely low (\text{CTE} \approx 0.5 \times 10^{-6}\ /\text{K}), while polymers like PVC and acrylate have shrinkage coefficients 2 to 3 orders of magnitude larger than silica.
During the rapid cooling process from room temperature to -196\ ^\circ\text{C}, the drastic shrinkage of the outer jacket and coating generates enormous internal shear and bending stresses. This stress not only causes the embrittled polymer casing to crack on its own but also transmits macroscopic and microscopic bending stresses directly to the internal silica fiber, leading to severe micro-bending losses. Under any minor disturbance (even slight touch or vibration), this results in simultaneous catastrophic fracture of the internal fiber and external jacket.
How to Safely Use Fiber Optic Patch Cords in Liquid Nitrogen/Ultra-low Temperature Environments?
To use optical fibers in environments like liquid nitrogen ( -196\ ^\circ\text{C} ) or even colder liquid helium ( -270\ ^\circ\text{C} ), it is essential to abandon traditional plastic sheaths and acrylate coatings and instead use specialized materials and structural encapsulation with ultra-low temperature physical resistance:
- Use Polyimide (Polyimide) or Metal Coating for Coating Layers: Polyimide materials can withstand extremely low temperatures down to -200\ ^\circ\text{C} or even -270\ ^\circ\text{C} for extended periods without physical mismatch; metal coatings (e.g., gold plating) maintain good mechanical protection at ultra-low temperatures.
- Use Metal Seamless Steel Tubing for Sheathing: Using stainless steel seamless steel tubing instead of plastic sheathing not only effectively shields against external side pressure. Stainless steel maintains excellent structural strength at -196\ ^\circ\text{C} and does not suffer from the cryogenic embrittlement typical of polymer materials.
Beijing Dacheng Yongsheng Technology Co., Ltd. (OFSCN®) has designed exclusive high and low-temperature specialty fiber optic patch cord products for such extremely cold, liquid nitrogen, and ultra-low temperature environments, ensuring optical signal transmission and mechanical structural integrity in deep-cold conditions:
1. OFSCN® 200℃ Fiber Optic Patch Cord
This product consists of fiber optic connectors such as FC/APC, a 0.9\text{mm} stainless steel seamless steel tube, and 200\ ^\circ\text{C} polyimide fiber. It has an operating temperature range of -200\ ^\circ\text{C} to 200\ ^\circ\text{C}, perfectly covering the liquid nitrogen ( -196\ ^\circ\text{C} ) temperature zone.
2. OFSCN® 300℃ Fiber Optic Patch Cord
This product has a wide operating temperature range from -270\ ^\circ\text{C} to 300\ ^\circ\text{C}. It uses 300\ ^\circ\text{C} polyimide fiber internally and can withstand the ultra-low temperatures of liquid helium and liquid nitrogen. It is often used in superconducting and aerospace environments.
3. OFSCN® 700℃ Fiber Optic Patch Cord
This product combines gold-plated fiber with a 0.9\text{mm} stainless steel seamless steel tube, featuring a temperature range of -270\ ^\circ\text{C} to 700\ ^\circ\text{C}. It offers extremely high mechanical stability and tensile strength in extreme deep-cold environments.
