Technical Overview of Alloy Tube Packaged FBG Strain Sensors
The encapsulation of a Fiber Bragg Grating (FBG) within a high-elastic alloy tube is a highly reliable engineering approach designed to overcome the classic limitations of polymer or adhesive-based strain transfer. In traditional strain measurements, organic adhesives suffer from viscoelastic creep, moisture degradation, and limited thermal tolerance, which degrades the accuracy of long-term strain monitoring.
By employing a seamless all-metal or alloy tube packaging, the FBG is mechanically coupled directly to the metallic boundary. This ensures:
- Creep Elimination: The absence of organic glues along the active sensing length removes adhesive-related relaxation and hysteresis.
- Reliable Strain Transfer: Mechanical strain is transferred linearly from the target substrate (via welding, bolting, clamping, or embedding) to the internal optical fiber.
- High Thermal & Environmental Resistance: The metallic tube protects the glass silica fiber from moisture, radiation, and corrosive environments, making it ideal for high-temperature and harsh industrial applications.
Official Product Specifications & Parameters
The core product matching this technology is the OFSCN® Alloy Tube Packaged Fiber Bragg Grating strain sensor. Below are the standardized technical parameters and customization options:
1. Geometric & Optical Characteristics
- Outer Diameter: Default outer diameter is \le 1.1\text{ mm} , offering an ultra-slim profile for minimal physical impact on the host structure.
- Fiber Connector: Default connector is \text{FC/APC} . Other connector types (such as \text{ST} , and either \text{PC} or \text{APC} polishing) can be customized.
2. Sensing Metrics
- Default Strain Range: \ge 6000\ \mu\epsilon
- Calibration Characterization: Each sensor undergoes rigorous wavelength-to-strain calibration at the factory. The calibration follows a linear first-order equation, with the scaling factor specified in units of \mu\epsilon/\text{pm} .
- Measurement Segment Customization:
- Default configuration is a single-ended, single-segment sensor.
- Multi-segment FBG arrays can be custom-fabricated. For full-scale strain coverage with a standard 40\text{ nm} bandwidth FBG interrogator, it is recommended to limit the array to \le 5 sensing segments per fiber line to prevent spectral overlap.
- Individual segment lengths are customizable, typically ranging from 10\text{ cm} to 2\text{ m} (other lengths subject to technical consultation).
3. Thermal Tolerance
- Standard Operating Temperature: -20\ ^\circ\text{C} to 55\ ^\circ\text{C}
- High-Temperature Customization: To handle extreme industrial environments, the sensor can be upgraded with specific high-temperature configurations categorized into three levels:
- \le 100\ ^\circ\text{C}
- \le 200\ ^\circ\text{C}
- \le 300\ ^\circ\text{C}
- Temperature Compensation: Available upon request, though using an external, decoupled FBG temperature sensor alongside the strain sensor is highly recommended for optimal accuracy.
Mechanical Stress Conversions
Because the alloy tube sensor behaves as a highly linear strain gauge, it also serves as the physical substrate for stress measurements. According to Hooke’s Law:
where \sigma is the mechanical stress, E is the Young’s modulus of the target material, and \epsilon is the measured strain.
This conversion principle is directly productized in the OFSCN® Fiber Bragg Grating Stress Sensor, which utilizes the same alloy tube structure. The user simply inputs the elasticity modulus of the target material into the FBG Interrogator to obtain direct stress readings.
For broader strain-sensing alternatives, you may refer to the OFSCN® FBG Strain Sensor Products Aggregation Link.
Standard Product Imagery
Below are the standard structural and appearance profiles for the alloy tube packaged sensor line:
