Ground Movement Detection Applying a Low-Cost OTDR with IoT Integration
Abstract
This study presents a low-cost landslide monitoring system that integrates Optical Time Domain Reflectometry (OTDR), ESP32-CAM–based digit recognition, LoRa communication, and a solar-powered IoT platform for real-time ground-movement detection. The system utilizes an OTDR (SGOT04) connected to fiber optic cables installed along the monitored slope, while the ESP32-CAM performs both OTDR data acquisition and numerical extraction from the device’s 7-segment display using a lightweight threshold-based segmentation method. The processed data are transmitted using LoRa RFM95 and visualized through a cloud dashboard for remote monitoring. System performance was evaluated through controlled laboratory and field-simulated tests. LoRa transmission demonstrated low packet loss across distances up to 150 m, with a 24-hour reliability test yielding only 1.08% data loss and 2.74% digit-recognition misreads. Comparative analysis between the SGOT04 and a reference OTDR (Yokogawa AQ1000) showed near-perfect linearity up to 5000 m, validating the accuracy of the low-cost device for cable-length measurement. A landslide simulation test using a droplet-loop fiber-breaking mechanism successfully triggered a detectable cable disruption at a slope angle of 36.9°, reflected by a sudden change in measured cable length from 1043 m to 1026 m. These results demonstrate that the proposed OTDR-IoT system provides accurate, stable, and cost-effective monitoring of ground movement and can serve as a promising early-warning solution for landslide-prone areas. Future improvements include advanced filtering, enhanced power optimization, and long-term field deployment.