Three-dimensional refractive index reconstruction with quantitative phase tomography.

Optical tomography based on quantitative phase microscopy is used to determine nondestructively and with high spatial resolution the three-dimensional (3D) refractive index distributions within optical fiber devices. After obtaining a series of phase images of the fiber as it is rotated around its longitudinal axis at regularly-spaced angular positions, filtered backprojection is used to reconstruct a 3D map of the refractive index. The 3D refractive index distribution of the join region between two fusion spliced optical fibers is reconstructed with accuracy better than 10(-3).

Analysis of changes in optical fibers during arc-fusion splicing by use of quantitative phase imaging.

A non-interferometric imaging technique in conjunction with Abel inversion is used to directly and quantitatively examine the changes in optical fibers due to the heating produced during arc-fusion splicing as a function of fusion arc parameters. Phase images in the vicinity of a fusion splice are obtained using Quantitative Phase Microscopy, allowing the refractive-index change to be reconstructed with high spatial resolution. This simple, nondestructive method confirms that, for a fixed arc current, while the fusion time increases, the refractive-index of both fiber cores within the fusion region decreases in magnitude, the core region broadens, and the axial gradient decreases.

Refractive index profiling of axially symmetric optical fibers: a new technique.

We present a new technique for determining the refractive index profiles of axially symmetric optical fibers based on imaging phase gradients introduced into a transmitted optical field by a fiber sample. An image of the phase gradients within the field is obtained using a new non-interferometric technique based on bright field microscopy. This provides sufficient information to reconstruct the refractive index profile using the inverse Abel transform. The technique is robust, rapid and possesses high spatial resolution and we demonstrate its application to the reconstruction of the refractive index profiles of a single-mode and a multimode optical fiber.

Orientation independent retardation imaging using quantitative polarized phase microscopy.

Simultaneous optical phase and retardation measurement of a birefringent specimen is demonstrated independently of a priori knowledge of the optic axis orientation. The two-dimensional retardation distribution in both magnitude and angle of the fast axis orientation is uniquely determined from transverse phase images recorded with a bright field transmission microscope using light polarized at a minimum of three different polarization orientations. This approach opens a new possibility for stain-free phase and orientation-independent retardation characterization of samples using only one polarizer without needing other additional optical elements traditionally used in polarimetric measurements.

Noninterferometric characterization of partially coherent scalar wave fields and application to scattered light.

We report on the application of a simple propagation-based phase-space tomographic technique to the determination of characteristic projections through the mutual optical intensity and the generalized radiance of a scalar, quasi-monochromatic partially coherent wave field. This method is applied to the reconstruction of the coherence functions of an initially spatially coherent optical wave field that has propagated through a suspension of polystyrene microspheres. As anticipated, we see that the field separates into a ballistic, or unscattered, component and a scattered component with a much shorter coherence length. Good agreement is obtained between experimental results and the results of a model based on a wave-transport equation.

Refractive-index profiling of optical fibers with axial symmetry by use of quantitative phase microscopy.

The application of quantitative phase microscopy to refractive-index profiling of optical fibers is demonstrated. Phase images of axially symmetric optical fibers immersed in index-matching fluid are obtained, and the inverse Abel transform is used to obtain the radial refractive-index profile. This technique is straightforward, nondestructive, repeatable, and accurate. Excellent agreement, to within approximately 0.0005, between this method and the index profile obtained with a commercial profiler is obtained.