# What is a "fiber optic feedthrough"?

**URL:** <https://forum.ofscn.net/t/what-is-a-fiber-optic-feedthrough/2980>\
**Category:** OFSCN Technical Knowledge Base\
**Tags:** fbg-technology\
**Created:** [October 10, 2026, 7:48am UTC](https://forum.ofscn.net/t/what-is-a-fiber-optic-feedthrough/2980 "2026-10-10T07:48:12Z")\
**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 10, 2026, 7:48am UTC](https://forum.ofscn.net/t/what-is-a-fiber-optic-feedthrough/2980/1 "2026-10-10T07:48:12Z")

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How can fiber optics be routed out of a high-pressure oil tank without oil leakage?

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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 10, 2026, 7:48am UTC](https://forum.ofscn.net/t/what-is-a-fiber-optic-feedthrough/2980/2 "2026-10-10T07:48:37Z")

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“Fiber Optic Feedthrough” (commonly known in English as **Fiber Optic Feedthrough** or **Fiber Optic Hermetic Penetrator** , also referred to as fiber optic sealed penetrators) is a specialized airtight connection component designed for the lossless penetration of optical fibers across sealed boundaries such as high-pressure vessels, high-low temperature chambers, vacuum chambers, or engine cylinders, while maintaining a reliable fluid barrier.

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### I. Engineering Physics Challenges of Fiber Optic Extraction from High-Pressure Oil Tanks

When extracting internal optical fiber sensors to external demodulation systems in high-pressure oil tanks, transformer oil tanks, or downhole pressurized vessels, direct use of traditional clamps or packing seals typically encounters the following failure mechanisms:

1. **Stress Concentration and Fiber Micro-bending/Shear** :  
The quartz fiber body typically has a diameter on the order of 125\ \mu\text{m} and is mechanically fragile. Traditional mechanical bolt tightening can easily form stress concentrations at the contact surfaces, leading to a drastic increase in optical loss or even fracture.
2. **Micro-pore Seepage and Capillary Effect** :  
In high differential pressure environments (such as high-pressure oil phases), microscopic gaps within the fiber’s protective coating and between the fiber and its outer protective tube can easily form leakage pathways.
3. **Temperature Resistance and Medium Corrosion** :  
Sealing materials must withstand long-term immersion and erosion by hot oil, insulating oil, or chemical media, while also maintaining matching coefficients of thermal expansion during thermal expansion to prevent cracking of the sealing interface.

The standard engineering solution to this problem is to install a **Fiber Optic Feedthrough/Sealed Flange** component at the opening of the container wall. Such components utilize specialized high-temperature airtight potting, glass/metal fusion, or metallization welding processes to permanently seal one or more optical fibers within a pressure-resistant metal body. This allows the optical path to withstand the strong pressure difference across the container without medium leakage, while maintaining low insertion loss.

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### II. OFSCN® Official Matching Products and Technical Specifications

Within the OFSCN® (Beijing Dacheng Yongsheng Technology Co., Ltd.) product line, the standard component for resolving fiber optic sealing and penetration between the inside and outside of containers is:

[OFSCN® Fiber Optic Vacuum Sealed Flange](https://www.ofscn.org/connectors/fiber-optic-sealed-flange.html)

 ![OFSCN® Fiber Optic Vacuum Sealed Flange](https://forum.ofscn.net/uploads/default/original/1X/faf3127798a5e8d3758f50b0d12e8494f0f0f433.jpeg)  
 ![OFSCN® Fiber Optic Vacuum Sealed Flange](https://forum.ofscn.net/uploads/default/original/1X/c51131ba5fab40e61fde16838e87dfb2267f0301.jpeg)

#### Key Technical Parameters and Specifications:

- **Structural Form** :  
Available in CF and KF standard interface series;
- **Interface Type** :  
Supports male (patch cord output) and female (fiber optic adapter flange type); supports single-channel and multi-channel;
- **Sealing and Vacuum Performance** :  
Vacuum better than 1 \times 10^{-7}\ \text{Pa} and 1 \times 10^{-9}\ \text{Pa};
- **Temperature Range** :  
Standard use at room temperature, with options for products resistant to 250\ \text{℃} high temperatures;
- **Compatible Optical Fibers** :  
Can be used with single-mode, multi-mode, or high-temperature resistant polyimide fibers, suitable for stringent sealing and pressure-resistant penetration applications.