# What is the "misconception about sampling frequency"? **URL:** \ **Category:** OFSCN Technical Knowledge Base\ **Tags:** fbg-technology\ **Created:** [October 31, 2026, 2:07pm UTC](https://forum.ofscn.net/t/what-is-the-misconception-about-sampling-frequency/3186 "2026-10-31T14:07:14Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![VoidWalker](https://forum.ofscn.net/letter_avatar_proxy/v4/letter/v/848f3c/32.png) [@VoidWalker](https://forum.ofscn.net/u/VoidWalker)\ **Post date:** [October 31, 2026, 2:07pm UTC](https://forum.ofscn.net/t/what-is-the-misconception-about-sampling-frequency/3186/1 "2026-10-31T14:07:14Z")
Is faster sampling always better? Is using 100Hz to measure dam deformation a waste of money? ---
**Author:** ![OFSCN\_Tech\_Expert](https://forum.ofscn.net/user_avatar/forum.ofscn.net/ofscn_tech_expert/32/199_2.png) [@OFSCN\_Tech\_Expert](https://forum.ofscn.net/u/OFSCN_Tech_Expert)\ **Post date:** [October 31, 2026, 2:07pm UTC](https://forum.ofscn.net/t/what-is-the-misconception-about-sampling-frequency/3186/2 "2026-10-31T14:07:45Z")
In fiber optic sensing and Structural Health Monitoring (SHM) engineering, the notion that **‘faster sampling frequency is always better’ is a prevalent technical misconception**. In practical engineering, blindly pursuing high sampling rates is not only unnecessary but also leads to negative effects such as signal-to-noise ratio (SNR) degradation, data redundancy, and skyrocketing system costs. For the specific physical scenario of **dam deformation monitoring** , if it’s used for routine quasi-static deformation monitoring, employing a 100\text{ Hz} sampling rate is indeed a mismatch of technical resources and a waste of funds in the vast majority of cases. * * * ### I. Why is sampling frequency not ‘the faster the better’? In signal measurement and sensing systems, the selection of sampling frequency is constrained by physical laws and information theory: 1. **Nyquist-Shannon Sampling Theorem Constraint** According to the sampling theorem, the sampling frequency f\_s of the demodulation system only needs to be greater than 2 times the highest physical frequency f\_{\max} of the measured signal (typically 5-10 times in engineering practice) to reconstruct the physical signal without distortion. Ultra-high-speed sampling that exceeds the characteristic frequency band by several or even dozens of times does not bring more valid physical information. 2. **Inverse Relationship between Signal-to-Noise Ratio (SNR) and Detection Accuracy** In the internal photoelectric conversion mechanism of Fiber Bragg Grating (FBG) demodulators, increasing the sampling rate means significantly compressing the exposure time of the photodetector (PD / linear photodiode chip) or spectral integration within each sampling period. With a limited light source output power, the number of photons received in a single acquisition is significantly reduced, leading to an increase in the system’s noise floor. Consequently, the SNR and resolution (e.g., achieving 0.1\text{ pm}) of wavelength measurement are more likely to degrade. 3. **Massive Data Redundancy and Storage/Maintenance Costs** If a monitoring system has dozens or even hundreds of measurement points and continuously collects data at 100\text{ Hz} around the clock, the daily data volume can reach tens of gigabytes (GB), and the annual data volume can reach tens of terabytes (TB). For low-frequency or quasi-static physical quantities, the difference between adjacent sampling points is almost entirely dominated by system noise. This not only consumes expensive transmission bandwidth and server storage resources but also imposes a heavy computational burden on backend feature extraction and data cleaning algorithms. * * * ### II. Is using 100\text{ Hz} for dam deformation measurement a waste? From the perspective of dam mechanical response characteristics, it is crucial to distinguish between **‘deformation monitoring (quasi-static)’** and **‘dynamic response/vibration monitoring (dynamic)’**, which are two different physical categories: 1. **Routine Deformation Monitoring (Quasi-Static/Creep Process)** 2. **Exceptional Cases Requiring High Sampling Rates (Dynamic Monitoring)** High sampling rates are physically necessary only in special scenarios aimed at evaluating the dynamic characteristics of the structure: * * * ### III. Official Technical Specifications and Engineering Configuration When selecting an FBG monitoring system, the sampling frequency of the demodulator should be strictly matched to the physical measurement objectives, channel scale, and system noise indicators. Beijing Dacheng Yongsheng Technology Co., Ltd. offers the following specifications for FBG demodulation equipment: - **Product Information** : [OFSCN® Fiber Bragg Grating Interrogator](https://www.ofscn.net/fbg-products/analyzer.html) - **Wavelength Range** : Default 1525 \sim 1565\text{ nm} or 1528 \sim 1568\text{ nm} (customizable) - **Channel Configuration** : Customizable for 4, 8, 16, or 32 channels - **Wavelength Resolution** : Default 1\text{ pm}, customizable to 0.1\text{ pm} - **Sampling Frequency Adjustment Mechanism** : Hardware options include 10\text{ Hz}, 50\text{ Hz}, and 100\text{ Hz}. On the software architecture level, the system supports users in adjusting the sampling frequency downwards as needed (with support for down to 1\text{ Hz} and timed polling modes), to meet the comprehensive engineering demands for ultra-low frequency, high SNR, and low data storage overhead in quasi-static deformation monitoring of dams and similar structures. ![OFSCN® Fiber Bragg Grating Interrogator 8 Channel](https://forum.ofscn.net/uploads/default/original/1X/8ecc1c112d2015cbc63afa6d42b87517befb2f87.jpeg) ![OFSCN® Fiber Bragg Grating Interrogator 32 Channel](https://forum.ofscn.net/uploads/default/original/1X/248718a63e2aa4cf7db24ad7a4df5ace79c95a05.jpeg)