A coaxial dual-waveguide structured optical fiber with an annular waveguide layer (CDOF) is designed and its
preparation method is provided thereof. The responding preform is fabricated by MCVD technique and then is drawn by
a custom-made fiber drawing tower. The optical fiber has a common fiber core and an annular waveguide layer on the
outer surface of the optical fiber. The refractive index profile is measured by a refracted near-field technique and a
standard cutback technique. The fiber can be applied in a novel optical fiber device or an optical fiber sensor, for
example, in-fiber integrated Michelson or Mach-Zehnder interferometer.
A series of Sc:Ce:Cu: LiNbO<sub>3</sub> crystals with various level of Sc doping were prepared using the Cz equipment with a
resistance furnace. The crystal storage properties with optical damage resistance ability, sensitivity and dynamic range
were measured by means of two-beam coupling light path. The defect structure is also discussed, accounting for the
optical damage resistance. Based on optimal one of these crystals as storage medium, one thousand of holograms were
recorded in a public coherent volume of 0.082 cm<sup>3</sup>. The result shows that storage density arrives10 Gbits/cm<sup>3</sup> and the
crystal has potential application in the future high density storage.
The mode field characteristics of eccentric optical fibers are investigated theoretically. The eccentric optical fiber is
converted to be a concentric three-layered optical fiber through the conformal representation and the corresponding field
distribution is given by solving eigenvalue equation of a general three-layered optical fiber waveguide. The method
should be proved a simple solution for optimizing the configurations of special optical fibers.
Based on the specialty designed linear-core-array fiber, a laser beam shape convertor has been
proposed and demonstrated. The experimental and theoretical results shown that a multi beam with the peak
power distributed in a linear array have been obtained at the end of the linear-core-array fiber and the output
beam shape depend on the coupling condition and the supermodes propagation distance along the
linear-core-array fiber. This device transfers the laser shape from a Gaussian beam to a controlled linear array
beam. It could be used in industry for manufacturing or medicine applications.
We propose and fabricate a twin-half hollow elliptical core polarization maintaining fiber. The shape of the core in the
polarization maintaining fiber is designed to be elliptical for generating a geometry birefringence. In the cladding, two
half-hollows are symmetrically distributed with respect to the elliptical core for producing a stress birefringence.
Therefore, the birefringence in such a polarization maintaining fiber is the mixed effect of the geometry and stress
birefringence. The birefringence generating mechanism is analyzed in detail and a theoretical formula depicting the
birefringence is built up. The simulation results for the twin-half hollow elliptical core fiber at different structural
parameters are obtained by using finite element method. Through adjusting the structural parameters of the fiber, the
relationships between the birefringence and the core diameter as well as the width of the core bridge are discussed.
A novel sinusoidal phase modulating optical fiber interferometers is described. The surface profile of an object can be
measured by grating modulating optical fiber interference fringes. The ± first-order beams diffracted by the grating are
coupled in two fibers and in optical fiber output two coherent point light source are generated. The two coherent point
light sources have the same intensity so as to high contrast interference fringes are got. When piezoelectric ceramic
vibrates with the grating, the position of ± first-order beams diffracted by the grating does not change but the phase of
optical fiber output field interference fringes change periodic. By using sinusoidal phase modulating method can detect
the phase variations of interference fringes and the surface profile of an object can be measured. Detail description about
the optical principle, optical path design and phase modulating and demodulation are researched. The experiment shows
that this measurement method can overcome fluctuate of light source intensity and wavelengths at the same time have
the characteristic of high precision and large non-contact measurement range.
By using spherical designed three-core fiber, a micro structured light pattern generator for sensing of 3-D object shapes
has been demonstrated. The square or hexagon grid interferometric fringe pattern formed by the fiber optic
interferometric grid generator is projected on an object's surface. The deformed grid pattern containing information of
the object's surface topography is captured by a CCD camera and is analyzed using a 2-D Fourier transforming
profilometry. The use of fiber optic grid interferogram technique greatly simplifies the holographic interferometry system
and the carrier grid interferogram can be conveniently generated without the use of excessive auxiliary components or
sophisticated experimental devices, and moreover, the three-core fiber can be used in very narrow places due to its small
size. Finally, the square or hexagon grid interferometric fringe pattern provides a data fusion ability, which could further
improve the accuracy of the 3-D shape sensing results.
A fiber optic bending sensing system that uses twin-core fiber as the sensing element has been proposed and
demonstrated. The twin-core fiber act as a two-beam interferometer in which phase differences is a function of the
curvature, and it can be demodulated by the shift of the unique identification spectrum. By way of FFT analysis of the
white light interferometric spectrum, the variation of bending can be measured. The relationship between the bending
curvature and the shift of the unique identification spectrum has been given and the experimental results were also
In order to calibrate structured light depth image object surface profile measurement binocular vision system, a calibration mathematical model and calculation method is given. Special gauge head is fixed on precision automatic platform, and then moved by standard space length in two-dimension measured section. Every orthogonal point's gauge head image is collected by subsystem. All orthogonal point coordinate values form a virtual grid field. The whole measurement section is divided into standard square region. From system coordinate transformation, the orthogonal point coordinate values in subsystem are one-to-one correspondence with real object coordinate values in the binocular vision measurement system. In every standard square region, the real object coordinate values are calculated and calibrated by segment linear interpolation. Detailed calibration algorithm principle and error analysis are given. The results show that a group of orthogonal grid point can calibrate the whole system measurement section. The systematic measurement errors are less than 0.15 mm within 100mm depth measurement range.