A Fibre Bragg Grating based Reed switch for intrusion detection

We show the implementation of an optical Reed switch, for intrusion detection systems. The Reed switch uses a novel transducer to convert the magnetic field into a strain, which is then converted into an optical signal by an optical fiber Bragg grating. The transducer works by using the magnetic field, to cause a ferromagnetic layer to be drawn towards a diamagnetic layer. The fiber Bragg grating is located between the two layers, such that when the magnetic field is present, the fiber is compressed, transversely. This results in a change in the Bragg gratings optical properties, specifically its spectral response, which can then be measured by the intrusion detection system.