Overview
IEC 61757-3-2:2022 is an international standard developed by the International Electrotechnical Commission (IEC) that specifies requirements for distributed fibre optic acoustic sensing and vibration measurement systems. Focusing on the phase-sensitive coherent optical time-domain reflectometry (ϕ-OTDR) method using Rayleigh backscatter and phase detection, this standard establishes terminology, characteristic performance parameters, test and calculation methods, and recommended test equipment for interrogation units in distributed acoustic sensing (DAS) systems. It does not cover quasi-static and low-frequency operation modes.
By providing a clear framework for performance assessment, IEC 61757-3-2:2022 facilitates reliable characterization, comparison, and quality assurance of distributed fibre optic acoustic sensors used in a variety of industries.
Key Topics
Terminology and Definitions
- Distributed fibre optic acoustic sensing systems (DAS)
- Interrogation units (IU) and their roles
- Essential measurement concepts like spatial resolution, measurement range, sample points, sample rate, and Nyquist frequency
Performance Parameters
IEC 61757-3-2:2022 identifies core parameters for comprehensive system evaluation:
- Dynamic Range: The range of vibration or acoustic signals that can be measured accurately.
- Frequency Response: The ability of the DAS to detect signal frequencies within specified limits.
- Fidelity: Optional parameter assessing the faithful reproduction of signal waveforms.
- Self-Noise: The inherent noise floor of the sensing system.
- Spatial Resolution: The minimum distance between two locations that can be distinguished as separate.
- Crosstalk: The degree to which a signal from one channel or location interferes with another.
- Loss Budget: The total allowable optical loss in the system.
- Sensor Reflection Robustness: The system's immunity to reflections within the sensing fibre.
Test Procedures and Equipment
The standard describes procedures and recommended setups for each performance metric, such as:
- Use of a simulated fibre sensor comprising delay coils and fibre stretchers
- Requirements for signal generation instrumentation and isolation chambers
- Approaches for data collection, processing, and reporting
Applications
Fibre optic distributed acoustic sensing, as described in IEC 61757-3-2:2022, plays a critical role across multiple sectors:
- Oil & Gas: Pipeline monitoring for leaks, intrusions, and mechanical faults using real-time distributed vibration sensing.
- Power & Utilities: Monitoring of transmission lines, substations, and critical infrastructure for vibration or acoustic anomalies.
- Transport: Railway and roadway asset monitoring for security and preventative maintenance.
- Security: Perimeter intrusion detection leveraging the high spatial resolution of DAS systems.
- Civil Engineering: Structural health monitoring in bridges, tunnels, and buildings to identify vibrations and potential mechanical issues.
Standardized definitions and test methods help ensure interoperability and performance transparency, supporting procurement, certification, and quality control processes in distributed acoustic fibre sensing deployments.
Related Standards
IEC 61757-3-2:2022 is part of the broader IEC 61757 series on fibre optic sensors. Key related standards include:
These documents collectively establish a comprehensive framework for specifying, testing, and comparing diverse types of distributed fibre optic sensors, supporting global adoption and innovation in fibre optic sensing technologies.
By adhering to IEC 61757-3-2:2022, manufacturers and end-users ensure reliable, repeatable, and standardized evaluation of distributed fibre optic acoustic sensing systems, fostering confidence in their deployment for advanced monitoring and security applications.
Open preview (PDF)Fibre optic sensors - Part 3-2: Acoustic sensing and vibration measurement - Distributed sensing
