Fiber optic sensors IV : 13-14 March 1990, the Hague, the Netherlands : proceedings : ECO3, the congress of EPS--European Physical Society, EUROPTICA--the Eurpoean Federation for Applied Optics, SPIE--the International Society for Optical Engineering - Kersten, Ralf Th, 1947- (Proceedings of SPIE--the International Society for Optical Engineering, 1990)