VTT Developed An Optical Fiber Made of Cellulose (video) VTT Technical Research Centre of Finland Share Print E-Mail Loading video... Caption VTT developed an optical fibre made of cellulose. Light travels in the optical fibre made of cellulose, because the core is surrounded by cladding material with a lower index of refraction. Light is reflected back into the core from the interface of the core and the cladding. Credit VTT Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.