OPTICAL FIBER HAVING REFLECTION PREVENTING FILM AND ITS PRODUCTION

摘要

PURPOSE:To obtain the titled optical fiber prevented from cracks on its reflection preventing film by heating at least the end surface part of an optical fiber having polycrystal state to remove grain boundary due to the polycrystal bodies and then forming the reflection preventing film on the end surface part. CONSTITUTION:The whole polycrystal optical fiber 20 is heat treated to remove all grain boundaries due to the polycrystal bodies and then the reflection preventing film 21 consisting of a single layer is formed on the uniform end surface 22 free from the grain boundaries by vapor deposition or the like. Or, only the end surface 34 of the polycrystal optical fiber 30 is heated to remove only the grain boundaries around the end surface 34 and then the reflection preventing film 21 consisting of a single layer is formed on the uniform end surface 34. Thus, the long-life infrared ray energy transmitting optical fiber provided with the reflection preventing film is obtained. In case of the optical fiber consisting of TlBr/TlI mixed crystal, the grain boundaries can be removed by >=150 deg.C heat processing.