PhD defence by Mads Vandborg

PhD defence by Mads Vandborg

When

07. feb 13:30 - 16:30

Where

Building 341, auditorium 21

Host

DTU Electro

PhD defence by Mads Vandborg

Temperature and Strain Measurements using Brillouin OTDR

Abstract

Whenever you drive across a bridge or through a tunnel, or when you receive gas from a gas pipeline or electricity from subsea high voltage cables, you most likely want to be confident about the structural health of those large structures. Maybe you even take for granted that those essential elements in the infrastructure do not fail. To ensure the health of these structures, structural health monitoring is needed. One of the sensing principles with great success for monitoring large structures is distributed optical fiber sensors.

In this project, we have investigated the use of sensor type “Brillouin optical time domain reflectometry (BOTDR)”. BOTDR allows for densely measuring the temperature and strain along large structures, currently up to a range of 100 km with a spatial resolution of 10 m. This corresponds to having 10,000 single sensors evenly distributed along the length of the cable. However, a range of 100 km is often not sufficient if operators want to monitor long cables, such as subsea high voltage cables connecting offshore windmill farms.

In this project, we have demonstrated how using amplifiers (of type Raman and Erbium) allow forincreasing the range up to 250 km. In addition, we have developed a model for predicting the signal-tonoise ratio in BOTDR sensors. The model is crucial when optimizing the different parameters of a BOTDR sensor. In addition to this, we have also investigated the use of multimode optical fibers in BOTDR to allow for better discrimination between temperature and strain in the measurements.

Supervisors

  • Principal supervisor: Professor Karsten Rottwitt, DTU Electro, Denmark
  • Co-supervisor: Senior Reseacher Lars Søgaard Rishøj, DTU Electro, Denmark
  • Co-supervisor: Research Specialist Lars Grüner-Nielsen, DOFI, Denmark

Evaluation Board

  • Professor Emmanuel Marin, Laboratoire Hubert Curien, University Saint-Etienne, France
  • Associate Professor Peter Horak, University of Southampton, UK

Chairman

  • Associate Professor Francesco da Ros, DTU Electro, Denmark

Master of the Ceremony

  • Associate Professor Henrik Wessing, DTU Electro, DTU, Denmark

Contact

Karsten Rottwitt

Karsten Rottwitt Group Leader, Professor