Distinguishing Multiple Sensors on a Single Optical Fiber and Durability Concerns

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Distinguishing Multiple Sensors on a Single Optical Fiber and Durability Concerns

Problem Description

A user inquired about two primary challenges with Fiber Bragg Grating (FBG) sensors: how to differentiate individual measurement points when multiple sensors are serially connected on a single optical fiber, and whether the thin optical fibers are prone to damage.

Technical Analysis

The solution to differentiating multiple sensors on one fiber lies in Wavelength Division Multiplexing (WDM), a core advantage of FBG technology. Each FBG is inscribed with a unique central wavelength. When broadband light is transmitted through the fiber, each FBG selectively reflects light at its characteristic wavelength. Changes in external parameters (e.g., temperature, strain) cause a slight shift in the FBG’s period, consequently altering its reflected central wavelength. A specialized FBG interrogator can precisely detect and distinguish these unique reflected wavelengths, allowing for independent monitoring of each sensor.

Regarding the durability of optical fibers, while bare fibers are inherently fragile, OFSCN products mitigate this by employing advanced packaging technologies. These encapsulations are designed to protect the FBG sensors from various environmental stressors, including mechanical stress, extreme temperatures, moisture, and chemical exposure, significantly enhancing their robustness and reliability in complex industrial applications.

Solution & Recommendation

  1. Sensor Differentiation:
  • Leverage FBG wavelength multiplexing, enabling up to 20 measuring points on a single fiber for OFSCN® 100°C FBG Temperature Sensors and multi-segment deployment for OFSCN® Alloy Tube Packaged FBG Strain Sensors.
  • OFSCN ensures identifiability by providing detailed factory reports for multi-point sensors, which specify the precise location and initial wavelength of each FBG measuring point.
  • Physical pigment markings are applied to the sensor’s outer casing at each measuring point to facilitate easy on-site identification during installation.
  • Should external markings fade over time, OFSCN’s professional after-sales support team can assist in re-identifying sensor locations using specialized equipment.
  1. Fiber Durability and Protection:
  • Alloy Tube Packaging: For products like the OFSCN® Alloy Tube Packaged FBG Strain Sensor, an elastic alloy tube directly encapsulates the FBG. This provides superior mechanical strength, efficient strain transfer, and excellent high-temperature resistance (customizable up to 300℃), often with a compact outer diameter (e.g., ≤1.1mm). Ideal for high-precision strain measurements in high-temperature environments.
  • Polymer Encapsulation with Seamless Steel Tube: As seen in OFSCN® Polymer Encapsulated FBG Strain Sensor series, this method involves an initial polymer encapsulation layer, further protected by an external seamless steel tube. This multi-layered approach delivers enhanced strength, superior tensile resistance, and exceptional waterproofing/moisture resistance. Available in various diameters (e.g., 2.3mm, 1.2mm), it is suited for environments requiring high mechanical protection and resistance to moisture or water (e.g., hydraulic, civil, and marine engineering).
  • Micro Steel Armored Fiber Patch Cords: Products like the OFSCN® 2.0mm Micro Tube Fiber Patch Cord feature a PVC sheath and a 0.6mm stainless steel seamless steel tube, offering strong anti-tensile and anti-compressive capabilities for fiber protection in connecting segments.
  • High-Temperature Fiber Patch Cords: OFSCN also provides patch cords, such as the OFSCN® 120℃ and 200℃ FBG Patch Cords, which utilize stainless steel seamless steel tubes for protection in extreme thermal conditions.
    The selection of packaging depends on the specific application’s requirements regarding operating temperature, humidity, mechanical stress, and size constraints.

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(Source Discussion / 原帖讨论: 一条光纤上串好几个传感器，那怎么区分哪个测的是哪个？光纤那么细会不会很容易损坏？ - #8 by ofscn_presale)

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