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Distributed acoustic sensing for phase-sensitive OTDR technology

on October 14, 2019

1000px-Distributed_Acoustic_SensingThe sensing system is a fundamental device that presents data information about the features of the surrounding environmental conditions to electronic tools. The information obtained through distributed fiber sensing is used for analytical purposes or processed and employed to take specific actions. Herewith, today distributed sensors find widespread application since they are applied in most of the human daily used items.

For instance, distributed optical fiber sensors apply light to probe a kilometer-length optical fiber employed as the sensing system. Thus, distributed sensors allow for the detection of strain or temperature variations along the fiber length. The principle of distributed optical fiber sensor operation is based on “scattering processes happening along the optical fiber, either Rayleigh stimulated Brillouin or Raman scattering”.

The characteristics of various scattering processes offer different applications to distributed sensors. For example, distributed optical fiber sensors based on Raman technology are regarded as highly efficient temperature sensing devices. Recent developments in sensing technology enable to reach a better resolution, higher bandwidth or longer-range operation.

Nowadays new sensing technique to interrogate an optical fiber applying Rayleigh backscattering process is considered to be very advanced. Such distributed sensors are based on phase-sensitive optical time-domain reflectometry (OTDR) technology, herein, they use a train of linearly-chirped optical pulses resulting in a quite simple conventionally used methodology. Additionally, distributed acoustic sensing for phase-sensitive OTDR technology provides amazing robustness against laser phase noise and a record measured sensitivity.

The technology of distributed acoustic sensing for phase-sensitive OTDR has been experimentally demonstrated a couple of years ago, based on the application of a chirped-pulse as a probe, in an otherwise direct-detection-based standard setup: chirped-pulse (CP-)ΦOTDR. The benefits of DAS systems include intrinsic immunity to fading points and use of direct detection, therefore, distributed acoustic sensing offers reliable high sensitivity measurements.

Finally, DAS technology for OTDR finds its use in diverse applications that include seismology or civil engineering (monitoring of pipelines, train rails, etc.), and new applications based on distributed acoustic or temperature sensing appear everyday. Such a distributed optical fiber sensor can operate in up to 100 km with a low cost-setup, showing performances close to the attainable limits for a given set of signal parameters.

Optromix is a DAS system manufacturer that provides top of the line distributed acoustic sensing systems suitable for monitoring of commerce networks. If you have any questions or would like to buy a DAS system, please contact us at

editorDistributed acoustic sensing for phase-sensitive OTDR technology

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