DTSX1 Fiber Optic Heat Detector

What Is Distributed Temperature Sensing?

Distributed temperature sensing (DTS) measures temperature distribution over the length of an optical fiber cable using the fiber itself as the sensing element. Unlike traditional electrical temperature measurement (thermocouples & RTD), the length of the fiber optic cable is the temperature sensor. Distributed temperature sensing can provide thousands of accurate and precise temperature measurements over a long distance. Compared to traditional electrical temperature measurements, distributed temperature sensing represent a cost effective method for obtaining accurate and high resolution temperature measurement.

Introducing Fiber-Optic Temperature Sensor, DTSX

Temperature monitoring throughout large plants without blank areas is difficult due to technical and cost issues and it is hard to comply with corporate HSE policies. DTSX measures temperature distribution over the length of an optical fiber cable using the fiber itself as the sensing element and it is ideal for temperature monitoring over long distances and wide areas. DTSX has been increasingly used in variety of applications such as fire detection, leak detection and preventative maintenance.


What Are the Advantages of Using DTS ?

  1. Cost
    When an application requires hundreds or thousands of sensors to be measured, it becomes very expensive to wire each individual sensor back to a data acquisition station. It is much more cost effective and beneficial to acquire accurate and high resolution temperature measurement using fiber optic cable.

  2. Long distance
    It is difficult to measure temperature over a long distance using traditional electrical measurement sensors. Not only can DTS fiber optic cable be deployed over a long distance but it also provides a high resolution profile of the area as well as accurate and precise temperature measurement over that distance.

  3. High electromagnetic noise environment
    DTS is isolated from electromagnetic noise because of its optical characteristics. Unlike traditional electrical measurement sensors (thermocouple & RTD) there is no electrical component within the optical fiber, therefore, it is immune to electromagnetic noise.
the advantages of using DTS


What Is DTSX1 Distributed Temperature Sensor ?

The DTSX1 not only addresses the needs for assets maintenance to avoid accidents caused by high-temperature heat, such as equipment abnormalities but also focuses on fire detection *1 applications. For example, it is introduced to detect fire in tunnels, cable trays, conveyor belts and more.
The DTSX1 measures temperature and detects heat using fiber optic cable It is similar to the traditional Linier Heat Detector (linear sensor of a fixed temperature detection type), but excels it in heat sensing ability. The DTSX1 allows for longer-distance measurement and provides a wider temperature range. By accurately detecting locations of multiple hot spots at the same time and giving alarms preset, it protects your important assets before temperature rises and results in a fire.
*1: Compliant with the European fire detection certification standard (EN 54-22)
       VdS certification number: G 220001

DTSX1 Distributed Temperature Sensor

About OpreX

OpreX is the comprehensive brand for Yokogawa’s industrial automation (IA) and control business and stands for excellence in the related technology and solutions. It consists of categories and families under each category. This product belongs to the OpreX Field Instruments family that is aligned under the OpreX Measurement category.


Measurement Principle

Operating Principle

Operating principle

Yokogawa DTSX1 measures temperature and distance over the length of an optical fiber using the Raman scatter principle. A pulse of light (laser pulse) launched into an optical fiber is scattered by fiber glass molecules as it propagates down the fiber and exchanges energy with lattice vibrations. As the light pulse scatters down the fiber optic cable, it produces stokes signal (longer wavelength) and anti-stokes (shorter wavelength) signal, of which both signals shifted from the launch of the light source. The intensity ratio of the two signals components depends on the temperature at the position where the Raman scatter is produced. This temperature can thus be determined by measuring the respective intensities of the stokes and anti-stokes signals. Furthermore, part of the scattered light, known as the backscatter, is guided back towards the light source. The position of the temperature reading can thus be determined by measuring the time taken for the backscatter to return to the source.


Raman Scattering

All light interacts with matter! For example, imagine standing in a pitch black garage with no external light source. Inside this garage is a bright red sports car. Needless to say, you cannot see the sports car or the color of the sports car itself. However, when you turn on the lights to the garage, you can immediately see the light source reflecting the bright red color off the car. The light that is bouncing off the red sports car is only bouncing off the "red" spectrum, therefore, your eyes see the sports car as, well, red.

Raman scattering

This phenomena is also true when you shoot a pulse of light (laser pulse) off of a molecule, in this case, the fiber glass molecule in the optical fiber cable. When the light source enters the optical fiber cable, most of the light bounces (backscatter) back unchanged (no change in wavelength). However, a small amount of that light shifted/changed. That shift/change from the light source is called Raman Scatter. Since Raman Scatter is thermally influenced by temperature, the intensity depends on temperature. Distributed temperature sensing is capturing the shift/change from the propagating light pulse and measuring the intensities between the two signal components (stokes and anti-stokes).


Types of Scattering Light

Yokogawa's distributed temperature sensors measure temperature distribution using Raman scattering light, which exhibits particularly good temperature sensitivity among the following types of scattering light.

Types of Scattering Light Features Field of Application
Rayleigh Scattering
  • Caused by fluctuations in the density inside the medium
  • Same frequency components as those of incident light
  • Optical fiber loss distribution
    (OTDR:Optical Time Domain Reflectometer)
Raman Scattering
  • Caused by the interaction with molecular vibration inside the medium
  • The intensity of anti-Stokes rays is mainly dependent on temperature.
  • Temperature distribution
    (DTS:Distributed Temperature Sensor)
Brillouin Scattering
  • Caused by the interaction with sound waves inside the medium
  • The frequency is dependent on strain and temperature.
  • Strain distribution
    (DSS:Distributed Strain Sensor)
  • Temperature distribution

Measurement Method

Single-Ended Measurement Method

  • This method launches optical pulses into only one end of the optical fiber for sensing. Easy to install, it is effective when the measuring target is long range.

Single-ended measurement method


Double-Ended Measurement Method

  • This method launches optical pulses into both ends of a looped optical fiber for sensing.
  • This method allows for continued measurement even if on place of the fiber optic cable is broken.

Double-ended measurement method


Comparison of Measurement Methods

Measurement Method Advantages Disadvantages
Single-Ended Measurement Method
  • Compared to the double-ended measurement, the fiber optic sensor cable can be easily installed.
  • No optical switch is required.
  • Even if the optical fiber is broken, it is possible to continue measurement at points before the broken section.
  • It is impossible to compensate for position-based optical fiber loss fluctuations.
  • The temperature calibration is more complicated than the double-ended measurement.
Double-Ended Measurement Method
  • The optical fiber loss distribution along the optical fiber is automatically canceled out.
  • Yokogawa's method reduces the influence such as darkening.
  • If the optical fiber is broken, the measurement method is automatically switched to the single-ended measurement.
  • The installation of fiber optic sensor cable must be looped.
  • An optical switch is required.
  • The actual maximum distance range for temperatuer measurement is a half that for the single-ended measurement method.

Types of Temperature Sensors


Types of Temperature Sensors and Their Features

Type Features
Fiber Optic Sensor An optical fiber, used as the temperature sensor, is suitable for monitoring temperatures over a long distance and wide area. It allows you to identify specific locations on a per sampling-interval basis along the fiber optic sensor cable and to monitor the temperature at each location.
Thermo Camera This instrument detects infrared radiant energy from objects to measure temperatures. Capable of measuring temperature distributions over a wide area in a non-contact manner, it is suitable for monitoring temperatures of industrial furnaces, solids of revolution, and so on.
Resistance Thermometer This sensor uses the characteristic of the electrical resistance of metal that changes almost in proportion to temperature. Capable of accurate temperature measurement, it is suitable for industrial precision temperature measurement.
Thermocouple When two different metals are connected to each other, the temperature difference between the metals develops electromotive force at the connection. This sensor uses this electromotive force. Capable of measuring temperature over a wide area at low cost, it is widely used as a temperature sensor for industrial use.
Radiation Thermometer This thermometer measures temperatures by measuring the intensity of infrared rays from materials. As a non-contact thermometer capable of remote measurement, it is suitable for measuring ultra-high temperatures.


Comparison among Temperature Monitoring Methods

  Fiber Optic Sensor
Fiber Optic Sensor
Thermo Camera
Thermo Camera
Point Sensor
Point Sensor (Thermocouple)
Description Wide-area monitoring based on a fiber optic sensor Surface temperature monitoring based on a thermo camera Multipoint monitoring based on discrete sensors
Detection Method Contact Non-contact Contact
Range of Temperatures Monitored -200 to 300 °C
(Based on a sensor cable)
Normal temperature to 2000 °C
(Range switching required)
-200 to 1000 °C
(Type K thermocouple)
Area Coverage of a very wide area
DTSX200: up to 6 km / ch
DTSX3000: up to 50 km / ch
DTSX1: up to 16 km / ch
Small viewing angle of 20° Wide area
Advantages Coverage of a very wide area and seamless monitoring Capability of a limited tiny area monitoring Capability of a limited tiny area monitoring
Disadvantages Restricted to small areas Non-seamless monitoring Non-seamless monitoring
Installation and maintenance of compensating lead wires

Types of cables

You can choose the most suitable type according to your intended use.

Normal Operating Temperature Applications Cable Type Cable Details Features
Normal Temperature
  • Conveyor Fire Detection
  • Cable Temperature Monitoring
  • Bus Duct Temperature Monitoring
  • Cable Tunnel Fire Detection
  • Warehouse Fire Detection
  • Hot Spot Detection
  • Cold Spot Detection
Standard Type Standard type Image Zoom Nonmetal, lightweight, and easy to install
EN 54-22 certified
Robust Type Robust type Image Zoom Resistant to crush and tension and less likely to break
EN 54-22 certified
Flexible Type Flexible type Image Zoom Thin and flexible and easy to install along the measurement targets
High / Low Temperature
  • Blast Furnace Monitoring
  • Drying Furnace Monitoring
  • LNG Leak Detection
  • Well Monitoring
Steel Tube Type Steel tube type Image Zoom Thin and flexible and easy to install along the measurement targets
Steel Armored Type Steel armored type Image Zoom Resistant to crush and tension and less likely to break

Simple System Construction Suitable for Fire Detection

In addition to the function of temperature monitoring, the DTSX1 provides functions to process temperature data (make zone and alarm settings and give warnings) and produce contact input / output, which allows for a simple system construction.

System Configuration Example

【Example of a Host System】
SMATRDAC+ (recorder and data logging software), CI server and CENTUM (integrated production control system)

Product Introduction

DTSX1 Overview

The DTSX1, which incorporates a heat detection function in a single box, can be used as a heat detector right away by simply connecting the fiber optic cable supplied as standard. It detects high heat over a wide area quickly and precisely. Also, the ability to configure the alarm display and sound individually to suit your applications enables rapid detection, localization, and identification of abnormalities.

The Advantages of DTSX1:

  • Rapid detection of fire over a wide area

    Temperature monitoring up to 16 km length along fiber optic sensor cable with 5 seconds minimum measurement time.
    Very wide area monitoring up to 4 routes (16 km x 4) with optical switch.

  • Human error reduction Human dependency prevention

    The continuance monitoring without blind spots doesn't miss abnormal temperature even if hazardous locations or hard-to-reach places.
    Identify abnormal point and allow for quick response with zoning monitor.

  • Time and effort reduction for building your system, etc.

    Package system with optic fiber cable and other accessories eliminates the time and effort needed to select them.
    Various host systems can get alarm easily via Modbus/TCP or relay output.

  • Running cost and warranty cost reduction

    The fiber optic cable will not break down as it has no mechanical elements, when the cable damages by external force it can replace only damage part.
    Assets insurance cost is reduced by integrating with fire extinguishing system.


On the Partner Portal Member Site, you can check the details of the specifications.
GS 39J06B35-01 : DTSX1 Fiber Optic Heat Detector


DTSX3000 Control Visualization Software (DTAP3000)

The DTSX1 needs to process temperature measurement data at multiple points from multiple channels.
The DTAP3000 is application software specifically designed to facilitate making settings of all DTSX products (DTSX3000 / 200 / 1) and indicating measurement data. With a variety of functions, such as setting and control of the DTSX1, indication of measurement results, analysis of changes in temperature, and setting and indication of alarms, the software provides you with information that helps you monitor temperature.


Refer to the General Specifications for detailed specifications.


Item Specifications
Measurement distance range 2km, 4km, 6km, 8km, 10km, 16km
Number of channels 1, 2, 4
Spatial resolution 1 m or less
Sampling resolution Measuring temperature at 0.5 - meter or 1 - meter intervals
Minimum temperature measurement time 5 sec
Measurement mode Single-ended, double-ended
Number of zones configured 1,000 (no overlapping)
Interface Optical output E2000 / APC 50 / 125 μm GI
LAN 10 BASE-T or 100 BASE-TX Modbus / TCP
Relay output 8, 64 ports, max 35 V / 1 A DC
Relay input 4 ports ON: 12 to 30 V / 5 mA DC
OFF: 3 V / 2 mA DC
Display POWER
(Displayed for each channel)
Switch RESET Alarm state reset
ACK Alarm acknowledgement
(Hold the alarm state)
Power supply Operating voltage 10 to 30 V DC
(Rated voltage: 12 or 24 V DC)
Power consumption 30 W (normally 15 W at 23 °C
ambient temperature)
Dimensions (W × H × D) 500 mm × 500 mm × 250 mm
Weight 28 kg
Mount type Wall mount


Category Standard
Fire detection EN 54-22
Laser safety IEC 60825-1
EN 60825-1
CE mark EMC EN 55011
EN 61000-6-2
General safety EN 61010-1
EN IEC 61010-2-201
RoHS Directive EN IEC 63000
Laser safety EN 60825-1
CSA mark General safety CSA C22.2
KC mark EMC Korean EMC standards
RCM mark EMC EN 55011

Note: Under EU legislation, the manufacturer and the authorised representative in EEA (European Economic Area) are indicated below:
Manufacturer: YOKOGAWA Electric Corporation (2-9-32 Nakacho, Musashino-shi, Tokyo 180-8750, Japan).
Authorised representative in EEA: Yokogawa Europe B.V. (Euroweg 2, 3825 HD Amersfoort, The Netherlands).


Fire Detection

Early fire detection to critical process and environment is an important component to any safety system. A blazing fire has devastating consequences to important assets, products and most importantly, human lives. Furthermore, the cost of downtime due to fire leads to lost opportunities and costly repairs. Discrete sensor technology often fails due to the surrounding environment conditions such as dust, humidity, heat and corrosion. In addition, it is expensive to maintain a conventional sensor technology due to constant repair. Yokogawa's DTSX1 is designed to detect fire in critical assets under the most extreme conditions and offers unmatched reliability, performance and cost savings.

Yokogawa's DTSX1 is designed to deploy in the following fire detection applications:

  • Conveyor belts carrying important goods
  • Tank farms
  • Cable trays
  • Underground tunnels
  • Pipelines (underground, above ground)
  • Nuclear facilities
  • Mining, Refinery
Feature Benefits
1m special resolution Identify the exact location of the fire
Up to 0.1°C temperature resolution Possible fire detection within the first 10 seconds of occurrence *
Fiber optic cable sensor Unlike discrete sensor or IR camera, fiber optic cable eliminates "blind spots"
Coated fiber optic cable Immune to dust, humidity, corrosion and dirt
Report and data analysis Access historical data using HTTP, SFTP or web browser
Wide range of communication protocols Connect to existing DCS, PLC, DAQ and wireless interface
6km optical fiber = 6,000 points! Cost effective way of measuring temperature compared to traditional sensor technology

* Assuming appropriate scan rate and data refresh intervals are used

Vehicle Lithium-ion Battery

Smart Monitoring of Manufacturing Process Shelves and Storage Shelves

Thermal runaway of lithium-ion batteries mounted on individual shelves is discovered at an early stage. This enables a quick initial response when an abnormality occurs to limit damage to a minimum.
(For details, refer to "Smart Monitoring of Manufacturing Process Shelves and Storage Shelves -In-vehicle Lithium-ion Battery Applications- ".)

Smart Monitoring of Manufacturing Process Shelves and Storage Shelves


Prevention of Fires in Exhaust Air Ducts in Battery Assembly Process

Fires or dust explosions in exhaust air ducts for preventing the contamination of aluminum dust in the assembly process of lithium battery batteries are monitored. Abnormalities are not overlooked as ducts extending over long distances in blind areas such as roof space are comprehensively monitored. (For details, refer to “Prevention of Fires in Exhaust Air Ducts in Battery Assembly Process -In-Vehicle Lithium-ion Battery Applications- ".)

Prevention of Fires in Exhaust Air Ducts in Battery Assembly Process


Monitoring of Soundness of Power Supply Bus Bar

The joints of the power supply bus bar are monitored.
Abnormalities are not overlooked as fiber optic cable is built into the bus duct and bus bars extending over long distances in blind areas such as roof space are comprehensively monitored.
(For details, refer to "Monitoring of Soundness of Power Supply Bus Bar -In-vehicle Lithium-ion Battery Applications-".)

Monitoring of Soundness of Power Supply Bus Bar


Fiber Optic Cable Visualizes In-furnace Temperature Distribution

The DTSX fiber optic distributed temperature sensor can monitor temperature distribution every meter along the path of the fiber optic cable.
Thermocouples, etc. are used for heater control as up till now, and by adding DTSX to them, it will be possible to visualize the temperature distribution inside the entire drying furnace.
Resolving heater and other problems by utilizing the result, and passing products through the furnace after setting the in-furnace temperature to the ideal temperature profile result in improved productivity.

Fiber Optic Cable Visualizes In-furnace Temperature Distribution

When attempts are made to measure multiple points by thermocouples, etc., wiring is complicated, construction costs escalate and periodic maintenance of each individual sensor is required. This is unrealistic when applying it to multiple drying furnaces.
As the DTSX system requires only laying fiber optic cable inside the furnace, both initial and running costs can be reduced.
Moreover, a single DTSX can cover multiple drying furnaces, which improves cost effectiveness.
The DTSX has also been put to use in monitoring the temperature distribution in tunnel furnaces.
(For details, refer to "Fiber Optic Cable Visualizes In-furnace Temperature Distribution".)


Yokogawa DTSX1 can protect the infrastructure of existing power line/cable and reduce cost by monitoring the thermal dynamics of the power transmission and distribution line. By measuring the temperature of the power line, power grid operators can maximize the usable capacity of the power current by avoiding power cable damage and extending the cable life by maintaining optical power current. More importantly, operators can identify hot spots, fire breakout and location of fire along the entire grid. DTSX1 minimizes the potential power grid network outages and streamlines preventative maintenance process. Because of its immunity to electromagnetic interference, DTSX1 is ideal for high voltage, high noise environment. DTSX1 is designed to deploy in the following environments:

  • Underground power cables
  • Subsea power cables
  • Overhead power lines
  • Distribution station
  • Substations
Features Benefits
Isolation from electromagnetic interference Fiber optic is isolated from electrical magnetic current
Real time temperature measurement and monitoring Measure and monitor real time power grid/cable temperature
Measure and monitor multiple power circuits/cables Up to 16 channels of optical switch can be connected
Report and data analysis Access historical data using HTTP, SFTP or web browser
Wide range of communication protocols Connect to existing DCS, PLC, DAQ and wireless interface
6km optical fiber = 6,000 points! Cost effective way of measuring temperature compared to traditional sensor technology

power image1power image2



What if you could detect signs of abnormalities in bus ducts (bus bars) quickly during maintenance and inspection work and respond to them at just the right time? Yokogawa DTSX monitoring solution constantly monitors connections that tend to deteriorate over time and contributes by pinpointing abnormality locations and reducing workload of maintenance personnel, helping to ensure stability in plant operations.


A belt conveyor fire detection solution employing the DTSX distributed optical fiber temperature sensor can greatly reduce crises that can threaten a company's survival.

Application Note

Temperature Monitoring Solution for 
Quick Detection of Fires in Fume Ducts


With industrial and economic development comes increasingly large and advanced power plants and factories. Nevertheless, we find many cases where the original cables, cable tunnels, and other components of the power infrastructure have languished under continuous operation.


Reactor/Furnace Wall Healthiness Monitoring with a Fiber Optical Temperature Sensor

Application Note

Temperature Monitoring Solution for Maximum VSD Operating Efficiency


Recently, several ARC Advisory Group analysts and management team members had a chance to sit down with the new Yokogawa President and COO, Mr. Takashi Nishijima, and several other top Yokogawa executives to discuss the company's burgeoning presence in the worldwide upstream and midstream oil & gas industry.

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