NTT achieves efficient urban monitoring with IOWN all-photonics network

By applying this configuration to multiple routes of optical fibre for communication already laid underground (in the service area of NTT WEST in Osaka City), NTT demonstrated that it is possible to grasp area-wide traffic trends using optical fibre sensing, and to visualise and analyse traffic conditions in real time.

Optical fibre sensing in the IOWN APN enables low-cost, prompt, and flexible areal expansion of urban monitoring. In the future, NTT will promote R&D and co-creation activities toward the establishment of more advanced optical fibre sensing that will contribute to solving social and regional issues by implementing optical fibre sensing in society and exploring usage scenarios based on these results.

Background

Optical fibre sensing, which enables the use of optical fibre for communication as a sensor, is expected to create new social value as demonstration tests and introduction of technologies for detecting construction vibration, supporting road snow removal decisions, and improving the efficiency of communication facility maintenance and operation progress. The combination of IOWN and optical fibre sensing enables advanced data analysis by taking advantage of the high-speed transfer of large amounts of data by APN, and is thought to promote the use of sensing data. Furthermore, by using the optical path selection function of the APN-Gateway (APN-G) 2, which composes APN, a single optical fibre sensing device can measure multiple existing communication optical fibres connected to APN-G. Thus, optical fibre sensing in conjunction with the IOWN APN has the potential to realise low-cost, prompt, and flexible areal urban monitoring, and these advantages are described in the IOWN Global Forum publication.

With the aim of social implementation of optical fibre sensing using IOWNs, the four companies constructed a connection configuration that enables optical fibre sensing via APN-G, and conducted wide-area and aerial traffic flow monitoring on open roads. Several examples of traffic flow monitoring using optical fibre sensing have been reported, but this is the first case of wide areamonitoring along multiple open roads.

Point of the technology

Construction of a connection configuration that can add optical fibre sensing functions to the APN-G

Since optical fibre sensing is measured using the round trip propagation of light, it is necessary to connect the optical fibre sensing instrument in a configuration that avoids devices (such as optical amplifiers) placed on the optical path of the APN that transmit light only in one direction. For this reason, NTT devised and constructed a connection configuration between the APN-G and an optical fibre sensing device that uses a directional-coupler (optical circulator) to avoid a device (optical amplifier) that transmits light only in one direction of the APN-G and to extract the round trip sensing light.

• Utilising optical fibre for communication installed in underground pipelines

Since the measurement is possible without any modification to the communication optical fibre cable or underground conduit, it is possible to obtain sensing data from a wide area by effectively utilising existing facilities.

• Optimised vehicle speed analysis for open roads

Unlike long straight roads such as expressways, the partnership conducted an analysis so that the speed and number of vehicles can be detected on short straight roads such as open roads with many intersections.

Results of the joint experiment

Five vibration sensing devices were connected to the APN-G to simultaneously measure surface vibration on five routes (Wiring totaling 37km, covering 8km in four directions) of existing optical fibre communication cables (laid underground on roads in Osaka City). By analysing this traffic vibration with a vehicle speed analysis algorithm, they were able to visualise in real time the average vehicle speed of vehicles on open roads, the amount of traffic on the road and its changes over time in a 200m mesh granularity. In addition, it was confirmed that the results of the analysis of vehicle speed and number of vehicles tended to agree with the correct data measured at five sites. (Demonstration period: December 2023 to January 2024: Data measurement; February to July 2024: Analysis and verification of usefulness).

Traffic flow meters on ordinary roads are installed at intervals of several kilometres only on major lines, requiring the permanent installation and operation of a huge number of sensors. However, optical fibre sensing linked to APN-G can flexibly monitor arbitrary points on optical fibre routes that extend to every corner of a city. It is expected to be used as a new social infrastructure, such as traffic congestion detection and prediction using traffic information collected from a wide area and application to urban traffic planning. The connection configuration of the optical fibre sensing device to the APN-G used in this study was adopted in the IOWN Global Forum publication.

Role of each company

• NTT: devising and constructing a connection configuration to provide sensing functions to IOWN APNs
• NTT EAST: calibration of vehicle speed and vehicle count position
• NTT WEST: selection of traffic vibration monitoring sites and selection and provision of facilities for demonstration tests
• NEC: provision of APN-G and implementation of optical fibre vibration measurement and vehicle speed analysis

Outlook

Based on these achievements, NTT will continue developing the optical fibre sensing market using APNs collaborating with other companies, including discussions at the IOWN Global Forum. In addition, along with the nationwide expansion of APN, NTT aims to realise low-cost, wide-area, and aerial urban monitoring that enables flexible sensing at arbitrary locations as long as it is connected with optical fibre, and does not require the installation and construction of permanent outdoor devices. In the future, NTT will promote R&D and co-creation activities aiming to solve social and regional issues through the social implementation of optical fibre sensing, with a perspective of various applications through urban monitoring, such as infrastructure monitoring, disaster prevention, and the realisation of infrastructure design incorporating nature in urban planning.