Multiwavelength optical fiber refractive index profiling

Fourier transform spectroscopy and interference microscopy are combined to provide the world's first multi-wavelength optical fiber refractive index profile (RIP) measurements. The RIP and its spectral dependence are obtained with submicron spatial resolution across an octave stretching from about 500 nm to the 1 micron operating band of Yb-doped fiber lasers and amplifiers. In contrast to commercial Refracted Near Field (RNF) technology, which measures at a cleave, the technique described here measures transversely through the side of an uncleaved fiber, enabling measurements of axial fiber RIP variations found in fiber gratings, physical tapers, and fusion splices.