The growth of long period fiber grating written in H2-loaded fiber within one hour immediately after fabrication was
measured and analyzed. Fast deepen on difference of refraction index was obviously observed in all the experiments,
but the peak wavelength to time and cross-coupling coefficient to time curves are fitted better in exponential decay
function than power function, and suggest a same variation pattern in difference of refraction index.
We propose a novel structure of single-polarization single-mode(SPSM) holey fiber designed based on resonant coupling
effect. The proposed fiber is able to achieve SPSM operation over an ultra-broad bandwidth as large as 920nm ranging
from 1.48μm to 2.4μm, within which only one polarization state of the fundamental mode can be effectively guided.
With the aid of six smaller holes around the central core, the effective mode area of the fiber is enlarged and the
chromatic dispersion curve is flattened. The numerical results indicate that the proposed fiber achieves nearly zero
ultra-flattened dispersion over a wide spectral range and the effective mode area is approaching ~78μm2 at 1550nm.
Moreover, the structure shows superiority in output beam quality owing to the symmetry of the central core region, and
also exhibits great modal compatibility with SMF.
The polarization sensitivities of demodulation techniques for tilted fiber Bragg Grating (TFBG) refractometer are
investigated theoretically with the complex mode based coupled mode theory. The use of perfectly matched layer (PML)
technique simplifies the radiation mode model. The numerical results show that both the normalized area detecting
technique and the power-referenced demodulation technique are highly polarization sensitive, the polarization sensitivity
increases with the grating tilted angle, thus, precise polarization control is essential in both of the demodulation
Time independent rate equations for fiber laser are solved accurately with numerical method under multipoint boundary conditions. A novel method based on genetic algorithm is firstly proposed to optimize distributed pump powers and fiber segment lengths of kilowatt YDDC fiber laser. The uniformity of temperature distribution is improved by using optimized method. The calculated results show that the lower operating temperature and better uniformity can be obtained through increasing the number of segments at the cost of decreased output signal power.