Observations of and applications for self-imaging in optical fibers

Experimental results of self-imaging in optical fibers are reported along with an analytical model that explains the observations. Some implications for sensor design are discussed.     

Pitchfork bifurcation and flip-flop operation with a coupled nonlinear system

A ring cavity system consisting of two hybrid Michelson interferometers coupled together with feedback is constructed. This system shows spatial bifurcation and can be utilized as an all-optical flip-flop device. We demonstrate experimentally a flip-flop operation by use of only a positive pulse in this system.     

Shift-invariant interpattern association neural network

A shift-invariant neural network that uses the translation-invariant property of the modulus Fourier spectra with the heteroassociation interpattern association memory is proposed. A binary encoding of a spectral sampling of the training set is used to preserve the main features. Computer simulations and experimental demonstrations are provided that show the shift-invariant property of the proposed optical neural network.     

Substrate-mode holographic polarization-division multi/demultiplexer for optical communications

Based on the diffractive properties of a transmission-type phase volume hologram, a new type of polarization-division multi/demultiplexer for optical communications is presented.     

Object illumination angle measurement in speckle interferometry

Errors in measurement of the object illumination angle affect fringe interpretation accuracies in speckle interferometry. To measure the object illumination angle we propose a method based on the moiré effect. The technique is easy to implement and was found to yield fast and accurate measurements.     

Thermal-stress-induced birefringence in bow-tie optical fibers

Birefringence induced by thermal stress in bow-tie optical fibers is studied in detail by the use of the finite-element method. Results of computer modeling show that a higher degree of birefringence can be obtained with the use of a larger cladding and larger stress-applying zones in the fiber.     

White-light reconstruction setup for shearograms using optical-fiber waveguides

A white-light reconstruction setup for shearograms using optical-fiber waveguides is presented. The setup is compact, is not susceptible to dust and scratches, and enables the two-dimensional fringe pattern on shearograms to be viewed directly under uniform and enhanced illumination with minimal image distortion.