Polarization dispersion of a 120-km long submarine optical cable has been experimentally shown to be approximately 1 psec. The length dependence of polarization dispersion is theoretically simulated with a simple model using structural fiber parameters. This reports clarifies how polarization dispersion grows along a fiber axis as a function of the birefringence perturbation mainly caused by core deformation, fiber twist and stress transversely acting on the fiber.

We have demonstrated crosstalk mitigation in single-mode MCFs using optical space coding. Four types of single-mode multicore fiber (MCF) models were evaluated by our scheme with the modified prime code and differential detection. Typically, intercore crosstalk was improved by 7-20 dB in 9-core fibers with an original crosstalk of 10-20 dB.

The longitudinal chromatic dispersion in single-mode fibers is investigated theoretically and experimentally. With a fabricated tapered fiber evaluation of longitudinal chromatic dispersion is clarified by using simple equation.

We have designed a novel fiber-optic light concentrator with scattering layers and evaluated the light concentration characteristics by ray-trace simulations as functions of the parameters of the incident light angle and wavelength, as well as the waveguide structure. Unlike well-known luminescent solar concentrators, in our models, illuminating light is directly captured through the proposed waveguide structure. The optical efficiency in our fiber-optic models is remarkably improved in long-length regions compared with that in simple slab waveguides. In addition, the waveguide length required to effectively collect light is extended to 300mm and 1.5m for optical fibers with 1- and 10-mm core diameters, respectively, which are ten times longer than those in slab waveguides with an equivalent scale. Because of the cylindrical structure of optical fibers, we have also evaluated the sensitivity of our models to surrounding light. Consequently, an obvious directional property containing single or three peaks of the sensitivity is clarified, and their widths can be tuned by changing the width of the scattering parts. These results suggest that our models are suited for sensor devices such as optical receiving antennas, rather than simple light concentrators. Finally, we model a fiber-optic probe as an application and evaluate the light concentration characteristics when the concentrator is serially concatenated with a normal optical fiber.

A short birefringent launching fiber is proposed to reduce the fluctuation of backscattering from single-mode fibers. The fluctuation is due to polarization-sensitive measurements. It is analyzed that the polarization direction of linearly polarized inputted light is required to make an angle of 27.4 with respect to the principal axes of the birefringent launching fiber. It is also clarified that degree of coherence should vanish at the group delay of τ and 2 τ where τ is the group delay difference of the orthogonal polarization modes in the birefringent launching fiber. Experiments reveal that the birefringent launching fiber of only 3-m length makes it possible to reduce the backscattered power fluctuation to less than 0.05 dB. Required properties of laser diodes are discussed by considering the coherency of the laser diodes with multi-longitudinal modes.

A 1-mm-diameter fiber-optic photoreceiver with a side-surface interface is proposed. By controlling the scattering part embedded in the fiber, the receiving sensitivity along the fiber's axis is successfully flattened over a 5-m-length. The simulation results suggest a potential for a large-area photo-detector of $sim$ 3-m-spherical diameter.