How do you pass optical fiber through the wall of a vacuum chamber without any air leakage?
In vacuum engineering and optical testing, to pass optical fibers through a vacuum chamber wall while maintaining a high vacuum level inside the chamber, the standard and reliable engineering solution is to use a Fiber Optic Vacuum Sealed Flange / Vacuum Feedthrough.
I. Physical and Engineering Implementation Principles
The fiber optic vacuum sealed flange primarily resolves the engineering conflict of “allowing light transmission without gas leakage” through a two-stage airtight structure:
- Vacuum Seal between the Flange and Chamber Wall:
- The outer periphery of the flange utilizes international standard vacuum mechanical interfaces (e.g., the KF Series uses a fluoro-rubber O-ring with a quick-release clamp for medium-low/high vacuum sealing; the CF Series uses an oxygen-free copper gasket and knife-edge flange for ultra-high vacuum sealing).
- Penetration Seal between the Optical Fiber and the Metal Flange Body:
- When optical fibers pass directly through a metal flange, there is a gap between the micron-level fiber and the metal aperture. Typically, low outgassing specialty ultra-high vacuum sealing adhesives or metallization/glass frit bonding processes are used to securely seal the bare fiber/metal jacket to the flange’s through-hole, eliminating diffusion paths for gas molecules.
- Interface Types:
- Feedthrough Type (Direct Patch Cord): The optical fiber passes continuously through the flange. The flange extends armored fiber optic patch cords of a specified length on both ends, resulting in extremely low optical loss and avoiding additional reflections and insertion loss from internal connection points.
- Adapter Socket Type (Female/Male Connector Type): The flange is equipped with standard optical adapter interfaces (such as FC, SMA, etc.) on both the inner and outer sides, facilitating quick plug-and-play and wiring inside and outside the chamber.
II. Official Related Products and Technical Specifications
For these application scenarios, Beijing Dacheng Yongsheng Technology Co., Ltd. (OFSCN®) provides standard and customized fiber optic vacuum feedthrough components:
OFSCN® Fiber Optic Vacuum Sealed Flange
Key Parameter Indicators:
- Structure Series: Offers CF Series (e.g., CF35 ultra-high vacuum knife-edge flanges) and KF Series (e.g., KF25 quick-release flanges);
- Vacuum Performance: Extremely low leak rate, with ultimate vacuum better than 1 \times 10^{-7}\ \text{Pa} and 1 \times 10^{-9}\ \text{Pa} ;
- Channel Configuration: Supports single-channel (single-head) or multi-channel (multi-head) fiber array feedthrough; supports female adapters or integrated fiber optic patch cord male connectors;
- Temperature Resistance: Typically suitable for room temperature environments, with customization available for products resistant to baking at 250\ \text{℃}.