“Yarı dağıtık algılama” nedir?

OFSCN Global Teknik Merkezi OFSCN Teknik Bilgi Bankası
1

Bunun, her yerde ölçüm yapabilen dağıtık algılama (Distributed Sensing - DTS) sistemlerinden farkı nedir?

2

Fiber optic sensing engineering field, Quasi-Distributed Sensing and Fully Distributed Sensing (usually refers to DTS technology etc.), while both use optical fiber as a transmission medium, their underlying physical mechanisms, spatial continuity, and application scenarios have fundamental differences.

Here is a core technology comparison and physical analysis of the two:

1. Core Differences in Concept and Spatial Continuity

  • Fully Distributed Sensing (e.g., DTS)
    • Principle: The entire optical fiber is both the transmission medium and a “continuous sensor”.
    • Characteristic: Every point (everywhere) on the optical fiber participates in the measurement of physical quantities.
    • Localization Mechanism: Utilizes Optical Time Domain Reflectometry (OTDR) or Optical Frequency Domain Reflectometry (OFDR) technology. It determines the specific spatial location of a physical quantity change based on the time difference or frequency difference of light propagation in the fiber. It achieves measurement by collecting intrinsic backscattered light (such as Raman scattering, Brillouin scattering, or Rayleigh scattering) generated by lattice vibrations or density fluctuations within the fiber.
  • Quasi-Distributed Sensing (e.g., FBG)
    • Principle: Sensors are only distributed at “specific discrete points” on the optical fiber; the fiber itself does not participate in sensing.
    • Characteristic: Typically, multiple Fiber Bragg Gratings (FBGs) are written at specific locations on a single optical fiber, forming a “sensor string/array”. Temperature, strain, etc., data can only be obtained at these points where gratings are written (measurement points). The ordinary fiber sections between two gratings have no sensing capability (they are blind spots).
    • Localization Mechanism: Primarily utilizes Wavelength Division Multiplexing (WDM) technology, assigning each grating a different initial reflection wavelength \lambda_B = 2 n_{eff} \Lambda . The demodulator distinguishes the position of each measurement point by identifying different spectral wavelengths.

2. Technical Specifications and Performance Comparison

Indicator Dimension Quasi-Distributed Sensing (using FBG system as an example) Fully Distributed Sensing (using Raman-DTS / OFDR as an example)
Physical Signal Mechanism Narrowband reflection of Fiber Bragg Gratings (extremely strong signal) Intrinsic backscatter of the optical fiber itself (extremely weak signal)
Spatial Continuity Discrete multiple points, with measurement blind spots between measurement points Spatially completely continuous, theoretically no measurement blind spots
Measurement Speed (Sampling Rate) Extremely fast. Data sampling frequencies are typically from 10\text{ Hz} to 100\text{ Hz} , or even at the \text{kHz} level, extremely suitable for dynamic vibration or transient process measurements. Relatively slow. Since backscattered signals are usually below -50\text{ dB} , a large amount of optical pulse accumulation and signal averaging is required. A single complete scan usually takes several seconds to minutes (except for special DAS).
Maximum Measurement Points per Channel Limited by the wavelength bandwidth of the demodulator’s light source (typically 40\text{ nm} bandwidth from 1525\text{ nm} to 1565\text{ nm} ). To prevent overlap of wavelengths between adjacent measurement points, a single optical fiber is generally limited to 5 to 10 measurement points. Almost unlimited. A 10\text{ km} optical fiber with a spatial resolution of 1\text{ m} is equivalent to having 10,000 continuous measurement points.
Accuracy and Signal-to-Noise Ratio Reflectivity is typically above 10\% to 99\% . The reflection spectrum is steep, providing extremely high signal-to-noise ratio, wavelength resolution, and measurement accuracy. Signal is weak and easily interfered with by noise and long-distance fiber attenuation. Complex algorithms are needed to extract weak signals.

3. Da Cheng Yong Sheng (OFSCN®) Related Products and Applications

Da Cheng Yong Sheng (OFSCN®) provides high-performance, high-reliability packaged sensors, sensing cables, and demodulation systems for both types of technologies:

A. Quasi-Distributed Sensing System Related Products

If you need multi-point, high-speed, high-precision local discrete physical quantity monitoring, we recommend our quasi-distributed sensor strings and demodulators based on Fiber Bragg Gratings (FBG):

  1. OFSCN® 300°C Fiber Bragg Grating Temperature Sensor

  2. OFSCN® 500°C Fiber Bragg Grating Temperature Sensor

    • Technical Advantages: Supports multi-point series design, providing excellent wavelength stability in extreme high-temperature environments. It is recommended not to exceed 5 measurement points within a single sensor.

  3. OFSCN® Polymer-encapsulated Fiber Bragg Grating Strain Sensor (0.7mm/1.2mm diameter)

    • Technical Advantages: Specifically designed for quasi-distributed strain monitoring, customizable with multiple measurement segments.

  4. OFSCN® Fiber Bragg Grating Interrogator

B. Fully Distributed Sensing System Related Products

If you are using a complete set of fully distributed sensing equipment based on “Raman Scattering DTS” or “Rayleigh Scattering OFDR”, Da Cheng Yong Sheng (OFSCN®) provides special seamless steel tube distributed sensing cables to provide stable physical protection for your long-distance, fully continuous measurements:

  1. OFSCN® 200°C Distributed Fiber Temperature Sensor

  2. OFSCN® 85°C Distributed Fiber Temperature Sensor

  3. OFSCN® 300°C Distributed Fiber Temperature Sensor

  4. OFSCN® 700°C OFDR Micro All-Metal Strain Sensor

4. Summary and Selection Guide

  • When you need to measure “global trends” (such as overall dam leakage, long-distance oil pipeline leakage, tunnel fire monitoring): Fully Distributed Fiber Sensing (DTS) is the only feasible solution, as you cannot predict where the leak will occur within a meter.
  • When you need to measure “local high-frequency, precise details” (such as local temperature rise of battery electrodes, force monitoring during medical device insertion, vibration monitoring of high-speed bridges or wings): Quasi-Distributed Fiber Sensing based on FBG, due to its extremely high signal-to-noise ratio and very fast physical response speed, is a superior engineering choice.