Measurement of Optical Fibers*
This chapter introduces typical measuring techniques employed when optical fiber cables are offered based on the first viewpoint. Measuring techniques on the principal specification items of optical fibers are outlined. The external cylindrical surface of the cladding is used as a reference surface for optical fiber axial alignment when fibers are spliced and is called the reference surface. A microscope is used generally for the measurement of fiber dimensions. Sometimes, video devices are coupled to the microscope. The optical intensity distribution method is a typical method to measure refractive index profiles. The Refracted near Field method measures the refractive index profile by detecting the light that is not trapped in the core. The far field pattern is the distribution of optical energy at a part somewhat away from the output end surface of the fiber. It is used in the measurement of NA.