Distributed temperature sensing (DTS) uses an optical fibre as the sensor itself: one instrument reports temperature at closely spaced points all the way along the fibre, rather than only at the places where individual sensors have been installed.
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Call +86 130 4890 6506 to discuss selection and site conditions Email usDistributed temperature sensing (DTS) is a measurement method in which a single optical fibre serves as both the transmission medium and the sensing element. An interrogator launches short pulses of light into the fibre and analyses the small fraction of light that scatters back towards it.
Two properties of the returning light are used together:
Combining the two produces a distance–temperature profile: a curve of temperature against position along the fibre. The fibre is often installed along a cable, in a duct, or through a tunnel, so the profile is read as the temperature distribution along that route.
The practical consequence is the one worth remembering: measurement locations are not something you install. You install one fibre and the instrument reports at whatever interval its design provides.
Point temperature sensing is the alternative it is usually compared with. Thermocouples, resistance temperature detectors and wireless sensor pucks each measure one location, and the coverage you get is decided by how many devices you buy and where you put them. DTS covers the whole fibre route, and the spacing between reported measurements is a property of the instrument rather than of how many sensors were purchased.
Raman scattering is the physical effect DTS exploits. It is the mechanism, not the method.
OTDR (optical time domain reflectometry) uses the same time-of-flight idea as DTS, but for a different purpose: it characterises loss and reflections along a fibre, for installation testing and fault location. It measures the fibre, not the temperature.
DAS (distributed acoustic sensing) is a sibling technique. It uses the same arrangement — an interrogator plus a fibre — but detects acoustic and vibration signals rather than temperature. The two answer different questions and are sometimes deployed on separate fibres in the same route.
"It measures every millimetre." It does not. Each reported value is an average over a finite length of fibre, and the spacing between reported values is a separate parameter. A hot spot shorter than that averaging length is smeared into a smaller, cooler-looking rise. This is the single most common source of disappointment in DTS projects.
"One fibre channel equals one cable." A fibre laid along a route may pass many cables, joints and sections. Turning distance into an asset name — which joint, which cable, which phase — is a mapping task that someone has to build and maintain. It is not a property of the instrument.
"It is a thermometer, so it gives absolute temperature." It gives a temperature profile, and how close that profile sits to absolute truth depends on the device, its calibration and its installation. Detecting a change above a site's normal behaviour is far more robust than quoting an absolute figure, which is why condition monitoring leans on relative behaviour.
"Better software makes the measurement more accurate." It does not. Accuracy is a property of the sensing device and the installation. Software decides what to do with a profile — how to filter it, how to alarm on it, how to keep evidence — and that is where monitoring projects actually succeed or fail, but it does not improve the underlying physics.
"It replaces point sensors." Not universally. For a single critical bearing or one accessible location, a dedicated point sensor is often simpler and cheaper. DTS earns its place where the route is long, the locations are many, or the places you need to see are not places you can reach.
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It tends to fit when many locations must be watched over a long distance, when the route is hard to access for manual inspection, or when continuous coverage matters more than individual point accuracy — cable tunnels and ducts, buried cables, and long process routes are the usual cases.
It fits less well when there are only a few isolated points to watch, when the span is short enough that point sensors are simply simpler, or when the requirement is control at millisecond timescales — spontaneous Raman backscatter is very weak, so averaging over a useful length of fibre takes time. DTS is a monitoring method; it is not a substitute for fast protection or control functions.
Distributed temperature sensing. The word that carries the meaning is "distributed": the temperature is measured along the length of a fibre, rather than at a set of discrete points.
An interrogator sends short light pulses into a fibre and measures the light that scatters back. The intensity of one scattering component depends on the local temperature, and the round-trip travel time tells the instrument where along the fibre that light came from. The result is a temperature profile against distance.
No. Both use time-of-flight along a fibre, but OTDR is a fibre-testing instrument that reports loss and reflections, while DTS reports temperature. They are different measurements that happen to share a physical principle.
A point sensor measures one location, so coverage is whatever you buy and install. DTS measures continuously along a fibre route, and the spacing between reported values is set by the instrument. Point sensors remain the better answer for a small number of specific, accessible locations.
The fibre is the sensor, so it must be suitable for the installation — mechanically and thermally — and it must be continuous over the route being monitored. Which fibre construction suits a given route is a project decision, and it is one of the things worth settling before the instrument is chosen.
Often yes. If an existing device exposes a usable interface with a documented register map, the monitoring layer can frequently be added without replacing the sensing hardware. Whether that is possible depends on the specific device, so it is a question to raise with the device's details in hand rather than to assume.
No, and it should not be asked to. It is a monitoring method. Where fast tripping or control is required, the specification should say so explicitly and the responsibility should sit with equipment designed for it.
If you are working out whether distributed temperature sensing fits your route, tell us the span, what you need to see, and what you already have installed. We will say which parts of the problem DTS solves — and which parts it does not.
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