Optical fiber sensors that enable monitoring and measurement that was not previously possible

Passive sensors that do not require a power source, and monitor or detect over extensive areas

Optical fiber is being used in various scenes and applications and is not limited to cables for the high speed internet. One of those applications makes the optical fiber itself the sensor and by doing things like combining it with an electrical-type sensor, it becomes an optical fiber sensor that monitors a subject item or carries out detection or surveillance.

The sensor part is composed of glass and no electronic parts are used so no power feed is required (passive sensor). In addition, sensors can be connected at multiple points so it can be used in applications that extend over a wide area. Because passive sensors are durable over a long period and do not require auxiliary equipment, it is possible to construct a system that suppresses both introduction and running costs. For example, damage has occurred often in recent years due to sudden and unexpectedly strong rain. We commercialized and obtained certification from the Japan Meteorological Agency for an optical rain gauge as a product that can instantaneously detect the state of heavy rain across a whole district. For terror and crime prevention countermeasures, we are also commercializing things like intrusion prevention optical fence sensors as intrusion warning systems with little incorrect operation due to electrical noise.

At Furukawa Electric, we have provided many optical fiber sensing systems using the optical technology we have cultivated to this point (optical fiber, optical parts, semiconductor lasers, etc.) towards the realization of a safe and secure society. Things like wide area monitoring for natural disasters like wind and flood damage or earthquakes, and equipment diagnostic systems for structures and plant equipment fall into that category.

     

You can know about changes in the natural environment from a distance

Optical-fiber-powered cameras, which use optical fiber to provide a power source and can transmit images to a remote location about 10 km distant even during a power outage, can instantaneously detect natural disasters like concentrated torrential rain, avalanches of earth and rocks, and landslides even in places where there is no commercial power supply.

Apart from communications cables, conventional monitoring camera systems require power source equipment and image transmission equipment to be installed and there was a danger they would be affected by something like a power outage during a disaster, lightning strikes or a disconnection in the system. Optical-fiber-powered cameras can monitor a remote area just by connecting to optical fiber and no auxiliary equipment such as a power source or image transmission device is required. Passive sensors including optical rain gauges, optical wind gauges, optical water-level gauges and optical fence sensors are not affected by lightning strikes or power outages so they are resistant to natural disasters and highly reliable. You can monitor the state of damage across a subject area while reducing the introduction costs and the rate of breakdowns.

In addition, until now, power supply with batteries or the like was necessary to measure data continuously when measuring the water temperature or tide level in the sea. However, if you equip measuring devices with batteries replacement work will definitely have to be carried out periodically. Consequently, Furukawa Electric commercialized an optical water-level gauge that doesn’t require a power source, and an optical-fiber-powered system that enables power supply using optical fiber. In combination with electric-type sensors, we enabled stable long-term measurement in even harsh environments.

Currently, in addition to seawater temperature, it is also possible to monitor continuously from a remote location the results of water quality observation such as the concentration of hydrogen ions in seawater or the concentration of dissolved oxygen or salt. It has become possible to predict the impacts exerted on water quality by things like ocean currents, water temperature and weather conditions, and changes in water quality, and applications are expected in fisheries (farming) facilities and harbor facilities for a more efficient fishing industry, disaster prevention and disaster reduction.

Masahide Ogawa of Furukawa Electric’s FITEL Products Division Access Network Department talked as follows about the future development of optical fiber sensors.
“In the past, we configured outdoor and wide area monitoring systems by combining various types of electronic devices and insulated the connections between various electric sensors and communications devices by connecting them with optical fiber as a countermeasure against lightning strikes. As a result, it was necessary to attach power sources individually to each device and because the number of electronic parts, including communications devices, also increased electric sensor systems were fundamentally vulnerable to operation in harsh environments and to power outages and lightning strikes. Optical fiber sensors do not have these fundamental vulnerabilities. We would like to promote their application and diffusion in future too as solutions for things like the conversion to ICT and IoT of social systems including disaster prevention measures, and measures against the aging of structures.”