Method of measuring a large current using a glass fiber current sensor

A method for measuring a magnitude of an exceptionally large current of up to about 200 kA, the method comprising the steps of:

• providing a glass fiber current sensor having a core glass composition composed predominantly of zirconium fluoride and containing up to about 3 mole % lead fluoride, the glass fiber current sensor further having a low Verdet constant at a wavelength used for the measurement and being capable of causing an angular rotation of polarized light less than 0.45° per kA per pass at the wavelength;
• providing a conductor;
• passing the current through the conductor to create a magnetic field surrounding the conductor;
• positioning the glass fiber current sensor within the magnetic field;
• propagating a polarized light into the glass fiber current sensor;
• measuring the angle of rotation of the polarized light in the glass fiber current sensor;
• and
• determining the magnitude of the current from the angle of rotation of the polarized light.