This thesis consists of two parts. One is concerned with all fiber-optic polarizers utilizing surface plasmon resonance and the other deals with TEC (thermally expanded core) fibers. Surface plasmon is an electromagnetic surface wave propagating along the boundary between two dielectric media, one of which has negative real dielectric constant. In the geometry of a thin metal film coated on the polished side of a fiber, the surface plasmon supported by the film can be excited by the evanescent field of light propagating along the fiber. Since the surface plasmon has TM-polarization characteristics, only TM-polarized light can be coupled to the surface plasmon and lose its optical energy performing as a polarizer. For experimental demonstrations, Al thin films with various thicknesses were coated by sputtering method onto the 633 nm, 830 nm, and 1.3 $\mu$m single mode fibers. For a given film thickness, the extinction ratio was a senstive function of the overlay oil index as expected. The maximum extinction ratios were higher than 30 dB for almost all samples and the best result was 42 dB at $90\mbox{\AA}$ film thickness, with the 1.3 $\mu$m single mode fiber. The insertion losses measured by the cut-back method ranged from 0.2 dB to 1.5 dB. The use of the TEC fibers in hybrid fiber-optic components has an advantage of eliminating lenses for collimation and focusing. In between the two ends of the TEC fibers, thin micro-optic devices such as a modulator, an isolator as well as a polarizer whose thicknesses are less than a few hundred microns can be inserted without serious loss due to diffraction. An electric furnace was fabricated to heat the fibers locally up to $1300\,^\circ\!C$. Many difficulties arose in heating the fibers at such a high temperature where they react chemically with the surrounding contaminants. The fibers became brittle and often stuck to the surrounding wall. Nevertheless 1.3 $\mu$m single mode TEC fiber was obtained by maintaining it at $1250\,^\circ\!C$ for 10 hours. The MDF(mode field diameter) of the fiber was measured to be enlarged by 27\%. By improving the heat treatment techniques, the MDF's of the fibers could be enlarged up to 2 or 3 times the original sizes.
