The spatial resolution of a 30km distributed optical fiber sensor
is optimized to 3m. Two methods to measure the spatial
resolution of distributed optical fiber sensor were demonstrated.
The lower limit of the spatial resolution of the system is
determined by the width of the input laser pulse. The bandwidth of
optoelectronic receiving system and the electronic system also
affect the spatial resolution of the system. The bandwidth of the
electronic system shall be matched with the pulse width of the
laser. The spatial resolution of system can be measured directly
or evaluated indirectly by the half width of the Fresnel
reflection at the end of the fiber. The spatial resolution of the
system reached 3m after the optimization.
Photosynthesis of plants is to absorb the special wavelength of sunlight by the chlorophylls. According to the absorption spectrum of chlorophylls, we managed to make a LED lamp for the growing of green plants, and the relative energy spectrum distribution of the lamp match with the absorbing spectrum of green plants. Because the absorption wavelength range of chlorophylls are respectively 390~420nm, 430~460nm and 650~680nm, we choose different peak wavelength LEDs which are respectively at 400nm, 450nm, 655nm. By calculation, the general energy ratio of the three types of LEDs is 22:46:33, which corresponds to the absorption spectrum of chlorophylls. The illuminance of lamp for the growing of green plants on plants away 0.5 meter is 80lx by measuring. The LEDs lamp can be used to complement light and increase the efficiency of photosynthesis in cloudy, in door or at night. In another word, the photosynthesis is more powerful, and the more carbohydrates are synthesized, supplying enough material and energy for the growing of green plants.
The Raman spectra intensity can be enhanced in liquid core optical fiber (LCOF) .The total Raman power emitted by the LCOF is a function of the following parameters: LCOF length, LCOF loss coefficients at the laser and Raman wavelengths, the concentration of analyte and input laser power. The attenuation of the light in CS2 is small in the range from 1400nm to1700nm. We dissolved liquid CCL4 into CS2 and got different solutions of different concentrations. When the analyte concentration was changed, the analyte molecules and the numerical aperture of the LCOF were also changed, so there is an optimum concentration at which the maximum Raman spectrum can be obtained. Our experiment result is in good agreement with the calculated results. Backward Raman scattering is superior to forward Raman scattering in our experiment. Raman intensity first increases to a maximum with fiber length, then decrease because the fiber attenuation becomes dominant. Therefore, there exists the optimum fiber length. In our experiment, we find that higher Raman intensity can be obtained when the fiber length is 2m. The Raman intensity becomes powerful when the input pump power becomes larger. Raman linewidth becomes narrow when the concentration decreased. Our experiment also approves it.