Introduction
Hermetic feedthroughs are crucial components that allow signals to pass through sealed barriers without compromising the internal environment. They are broadly classified into electrical and optical hermetic feedthroughs, each designed for specific applications. Understanding the differences, advantages, and use cases of each type helps engineers select the right solution for aerospace, medical, industrial, or research applications.
1. Electrical Hermetic Feedthroughs
Electrical hermetic feedthrough allows electrical power or signals to pass through a sealed barrier. They use metal pins, ceramic or glass insulators, and airtight housings to maintain hermeticity while ensuring electrical isolation.
Applications:
- Aerospace electronics: Powering and controlling satellite or aircraft systems.
- Medical devices: Delivering signals to implantable or sterilized equipment.
- Industrial vacuum systems: Transmitting electrical signals into high-vacuum chambers.
Advantages:
- Supports high-voltage or high-current applications.
- Multi-pin designs allow numerous connections through a single seal.
- Provides robust electrical insulation and mechanical strength.
2. Optical Hermetic Feedthroughs
Optical hermetic feedthroughs allow fiber optic cables or light signals to pass through sealed barriers. They preserve the signal integrity of optical data while maintaining environmental protection.
Applications:
- Telecommunications: Ensuring fiber optic connections in sealed housings.
- Aerospace and defense: Transmitting data signals through vacuum or pressurized systems.
- Research laboratories: Protecting optical sensors or instruments in controlled environments.
Advantages:
- Maintains high-speed optical signal transmission.
- Resistant to electromagnetic interference (EMI).
- Ideal for systems requiring low signal loss and high data integrity.
3. Key Differences Between Electrical and Optical Feedthroughs
| Feature | Electrical Feedthroughs | Optical Feedthroughs |
| Signal Type | Electrical (power/data) | Optical (light/data) |
| Insulation | Ceramic, glass | Glass or optical fiber sealing |
| EMI Susceptibility | Can be affected by EMI | Immune to EMI |
| Multi-Signal Capability | Multi-pin designs available | Multiple fibers possible |
| Applications | Aerospace, medical, industrial | Telecom, optical sensors, research |
The primary difference is that electrical feedthroughs transmit electricity, while optical feedthroughs transmit light signals, requiring different materials, designs, and performance considerations.
4. Material and Design Considerations
Electrical feedthroughs often use metal pins, ceramics, and glass, designed to handle voltage, current, and thermal stress. Optical feedthroughs focus on fiber alignment, low attenuation, and minimal signal loss, often using fused glass or ceramic ferrules. Both types require hermetic sealing to protect internal components from moisture, gas, or contaminants.
5. Selecting the Right Feedthrough
The choice between electrical and optical feedthroughs depends on the signal type, system requirements, and environmental conditions:
- Use electrical feedthroughs when transmitting power, voltage, or analog/digital signals.
- Use optical feedthroughs when high-speed data, immunity to EMI, or fiber optics are required.
In some advanced systems, both types are combined to handle mixed electrical and optical signals in a single sealed housing.
Conclusion
Electrical and optical hermetic feedthroughs serve different but equally critical roles in sealed systems. Electrical feedthroughs provide robust power and signal transmission, while optical feedthroughs ensure high-speed, interference-free light-based data transfer. Selecting the right type ensures reliable performance, protection of sensitive components, and system longevity across aerospace, medical, industrial, and research applications.