A fiber optical measuring device for measuring a magnetic or electric field comprises an optical modulator influenced by the field. The optical properties of the modulator are dependent on the magnetic or electric field acting on the modulator. The optical property which is made use of is the field dependence...http://www.google.com.au/patents/US4356448?utm_source=gb-gplus-sharePatent US4356448 - Apparatus for measuring electrical or magnetic fields by absorption spectrum change
