Optical fiber is characterized as being lightweight, flexible, lightning resistant, long life service, and explosion proof. It is mainly used for optical communications, however, when using it as a sensor the distribution of temperature, strain, and vibration can be measured over the entire length of a long optical fiber.
Yokogawa aims to use these properties of optical fiber sensors as a health diagnostic tool for social infrastructure including bridges, tunnels, and other large structures. As another application, Yokogawa is also aiming for the early detection of equipment failures and other breakdowns in petroleum and chemical plants.
Brillouin optical correlation domain reflectometry (BOCDR)
BOCDR can measure temperature, strain, and vibration with a centimeter spatial resolution (resolution in the longitudinal direction of an optical fiber). This technology uses the principle that the frequency of the Brillouin scattered light generated in an optical fiber depending on these parameters. Temperature, strain, and vibration over the entire length of an optical fiber can be quickly measured with high spatial resolution by connecting only one end of the optical fiber to a measuring device.
Advantages of measuring distribution and spatial resolution
Because the optical fiber itself is used as a distributed sensor, it is possible to measure a range of 1 km or more with no unmeasurable intervals (blankless). If a suspicious location appears, the spot can be analyzed in detail with a high spatial resolution.
Vision for the Future
Applications for social infrastructure
By deploying optical fiber in social infrastructure such as bridges and tunnels, and using it as a strain/vibration distribution sensor, Yokogawa aims to realize the following:
- The ability to improve safety by detecting damage or defects at an early stage, or by follow-up observations of trouble spots. It can also be used for the early health diagnosis of infrastructure after an earthquake.
- Reduced maintenance costs by narrowing down inspection points and cutting incidental work, such as disassembly/reassembly and setting up/tearing down of scaffolding.
Applications for plants
Plants have a complicated structure in which a large number of facilities are connected within a vast site; thus, either productivity decreases or accidents occur unless the facilities are properly maintained and managed. This solution aims to improve customer productivity by efficiently collecting temperature, strain, and vibration information by installing fiber optic sensors in plant facilities, and analyzing the data to improve health, safety, environmental friendliness, and maintainability.
Application in high-temperature measurement
Fine optical fiber sensors installed inside or outside the engines of large vessels, large distillation towers, and long pipes can be used to monitor temperature distributions, enabling the early detection of anomalies (such as combustion failure, piston seizure, temperature irregularity, overheating, and thinning of pipes). In this way, the operation can be optimized, product quality improved, and accidents prevented.
* BOCDR was invented by the Hotate Laboratory at the University of Tokyo. A portion of this research and development was conducted by entrusting it to the Japan Science and Technology Agency (JST), Adaptable and Seamless Technology Transfer Program through Target-driven R&D (A-STEP).