The use of optical fibres for the measurement of ozone based on the optical absorption of visible light at 600nm is investigated and tested. Calculations based on the Beer-Lambert Law are presented to demonstrate the ability of the sensor to measure high concentrations over a wide range. Detecting ozone gas using optical sensors working in the visible region of the electromagnetic spectrum has not previously been demonstrated in an industrially suitable sensing device. Sensing in the visible region can enable the fabrication of low cost, easily applicable sensors due to the inexpensive nature of the components compared to UV components and thus may have a significant influence on ozone detection in industrial processes. © 2005 IEEE.