NTT Group and NEC demonstrate wide area traffic flow monitoring in urban areas

The NTT Group (NTT Corporation, NTT East Corporation, and NTT West Corporation) and NEC jointly developed a connection configuration that incorporates optical fiber sensing in the IOWN APN. By employing the configuration to existing communication optical fibers across multiple routes in Osaka City, the NTT Group and NEC demonstrated that it is possible to identify traffic trends across a wide plane using optical fiber sensing and visualize and analyze traffic conditions in real time. Through this, optical fiber sensing incorporated in the IOWN APN enables low-cost, prompt, and flexible urban monitoring across a wide plane. The four organizations will continue to explore application scenarios based on the results of this study. Toward social implementation of optical fiber sensing that will contribute to solving social and regional issues, they will promote R&D and co-creation activities to establish more advanced optical fiber sensing systems and aim to expand the market for the IOWN APN with optical fiber sensing.

Traffic flow meters are installed only on major roads at intervals of several kilometers. They require the permanent installation and operation of numerous sensors, which pose challenges such as high costs and difficulty of rapid and flexible operation. Optical fiber sensing utilizes existing communication optical fibers as sensors and is a low-cost, prompt, and flexible monitoring technology. Demonstration tests and the introduction of the technology to detect construction vibrations, assistance in making decisions about snow removal from roads, and improvement of the efficiency of communication equipment maintenance and operation are under progress. The technology is expected to create new social value.

Optical fiber sensing combined with the IOWN APN provided by the NTT Group will enable advanced data analysis by leveraging the IOWN APN's capability of high-speed transfer of large amounts of data. It is expected that this development will promote the utilization of sensing data. Utilizing the optical path selection function of the APN-Gateway (APN-G) that constitutes the IOWN APN, a single optical fiber sensing device can measure multiple existing communication optical fibers connected to the APN-G. Therefore, optical fiber sensing in conjunction with the IOWN APN has the potential to realize low-cost, prompt, and flexible urban monitoring across a wide plane.

The four organizations have now established a connection configuration that enables optical fiber sensing via the APN-G and have conducted a wide-area traffic flow monitoring on public roads across a wide plane. Although several examples of traffic flow monitoring systems based on optical fiber sensing have been reported in the past, this is the first case of a wide-area monitoring system for multiple public roads across a wide plane. Optical fiber sensing is a measurement technique that uses light propagating back and forth through an optical fiber.

However, in the IOWN APN, devices (such as optical amplifiers) that pass light only in one direction are placed in the optical fiber path and cannot be used for measurement as they are. The organizations devised and constructed a connection configuration incorporating the APN-G and optical fiber sensing devices that can extract round-trip sensing light using a directional-coupler (optical circulator), avoiding devices that allow light to pass only in one direction.

Five vibration sensing devices were connected to the APN-G and traffic vibrations were simultaneously measured for five routes across a wide plane with existing optical fiber communication cables laid under the roads in the Osaka city. The routes are 37 kilometers long and cover an area of 8 kilometers in four directions. By analyzing the traffic vibration measurement data using a vehicle speed analysis algorithm, it was possible to visualize in real time-with a fine granularity of 200-meter mesh-the average speed of vehicles traveling on the roads, amount of traffic on the roads, and traffic change over time. The analysis results of vehicle speed and the number of vehicles showed a trend consistent with that of the actual data obtained at the five routes.