AP Sensing
AP Sensing is a German manufacturer of distributed fiber optic sensing (DFOS) technology, headquartered in Böblingen and tracing its origins to Hewlett-Packard’s optical measurement business via Agilent Technologies, before becoming an independent company in 2007.
The company builds three sensing technologies in-house: Distributed Acoustic Sensing (DAS), Distributed Temperature Sensing (DTS), and Distributed Temperature and Strain Sensing (DTSS).
All three use optical time domain reflectometry (OTDR), turning a standard fiber optic cable into a continuous sensor along its full length.
For structural health monitoring, DTSS is the relevant technology. It applies Brillouin-based OTDR to track temperature and strain simultaneously along the fiber, detecting mechanical stress, structural shifts, and thermal anomalies in real time.
Application in rail infrastructure
AP Sensing positions DTSS for monitoring bridges, tunnels, and track structures, with the aim of catching risks such as landslides, track deformation, and tunnel instability before they escalate.
Its DAS systems are also used for railway applications including track condition monitoring, rail defect detection, and a “Below Ballast Scan” that assesses ballast and subgrade conditions to depths of 50 meters.
Both DAS and DTS/DTSS data feed into SmartVision, the company’s asset visualization and data management software, which consolidates sensor output for network operators.
A distinguishing feature of the fiber-based approach is that it requires no trackside power or electronics, since the sensing element is the cable itself.
Market position and activity
AP Sensing operates internationally, with a presence in Europe, Asia, and North America, and its fire detection systems have achieved SIL-2 (Safety Integrity Level) certification for use in safety-relevant monitoring applications.
In the rail sector, the company has run trials with Deutsche Bahn on cable theft detection using DAS.
Its most direct rail research activity is FOSSIL 4.0 (Fibre Optic Sensing for Safety Integrity Level), a project run with the Technical University of Darmstadt and DB Netz, partly funded by the German Federal Ministry for Digital and Transport, evaluating whether a fiber-based digital twin can support real-time train integrity verification as an alternative to point-based axle counters.
