Jian Shui-sheng

Mode classification and degeneracy in photonic crystal fibers.

Based on supercell lattice method, a novel full vector model is presented to analyze the photonic crystal fibers (PCF). From symmetry analysis of modes of a waveguide, we classify the modes of PCF into nondegenerate or degenerate pairs according to the minimum waveguide sectors and its appropriate boundary conditions. We present the modes of PCF can be labeled by its step index fiber analogs, except the modes with the same symmetry as PCF. The doublet of the degenerate pairs in which both have the same symmetry as PCF will be split into two nondegenerate modes.

Supercell lattice method for photonic crystal fibers

A supercell lattice method, believed to be novel, deduced from the plane-wave expansion method and the localized basis function method, is presented for analyzing photonic crystal fibers (PCFs). The electric field is decomposed by use of Hermite-Gaussian functions, and the dielectric constant of PCFs missing a central air hole is considered as the sum of two virtual different periodic dielectric structures of perfect photonic crystals (PCs). The structures of both virtual PCs are expanded in cosine functions. From the wave equation and the orthonormality of the Hermite-Gaussian functions, the propagation characteristics of the PCFs, such as the mode field distribution, the effective area, and the dispersion property, are obtained. The accuracy of the novel method is demonstrated as we obtain the same results when the dielectric constant is split into two virtual ideal PCs in different ways.

Switchable Multi-Wavelength Erbium-Doped Fiber Lasers Based on a Mach–Zehnder Interferometer Using a Twin-Core Fiber

A switchable multi-wavelength erbium-doped fiber ring laser based on a compact in-fiber Mach–Zehnder interferometer comb filter at room temperature is presented. The comb filter is formed by splicing a section of twin-core fiber between two single mode fibers. By adjusting the states of the polarization controller appropriately, the laser can be made to operate in stable single-, dual- and three-wavelength lasing states. The operation principle is based on spectral hole burning induced by the saturated effect and polarization hole burning.

Performance of a 10-Gbit/s Transmission System over 1500 km G.652 Fibre Compensated by Cascaded Narrow-Band Chirped Fibre Bragg Gratings

We obtain the error-free transmission of an 8?10?Gb/s signal over a 1500?km G.652 fibre by means of significantly improving the quality of narrow-band chirped fibre Bragg gratings (FBGs). Asymmetric apodization is one of the powerful measures to improve the quality of gratings. Wavelength-dependent transmission performance is also observed. The experimental results indicate that the total in-band local dispersion deviation of the cascaded gratings in each channel could be a good indicator of the performance degradation tendency at different operating wavelengths, which further reveals the potential of local dispersion deviation as a performance evaluating indicator of chirped FBGs.

Loss properties due to Rayleigh scattering in different types of fiber

The effects of fiber structure on Rayleigh scattering were investigated in detail. Some step-index fibers such as GeO2- and F-doped silica-based fibers and total-internal-reflection photonic crystal fiber are examined. The Rayleigh scattering loss (RSL) depends on the fiber materials and index profiles, and different types of fiber have different dependencies on those parameters because of the different optical power confinement factors in every layer. On the basis of these results, the RSL can be optimized by adjusting the fiber structure or by selecting different materials.

Dependence of mode characteristics on the central defect in elliptical hole photonic crystal fibers

Some mode characteristics are obtained by the full vector supercell overlap method that has been developed to model triangular lattice elliptical hole photonic crystal fibers regardless of whether the light is guided by total internal reflection or a photonic bandgap mechanism. When the central defect hole is large enough, the modes are disordered. Birefringence (Deltan) dependence on the central defect is discussed in detail by numerical analysis.

Suppression of the interactions between fibre gratings used as dispersion compensators in dense wavelength-division multiplexing systems

Chirped fibre Bragg gratings (CFBGs) are required to be concatenated to compensate the fibre dispersion in the dense wavelength-division multiplexing (DWDM) systems. When the channel spacing is small, the performance of CFBGs is degraded, which restricts the usage of fibre gratings. The origin of the interactions between the gratings is analysed and methods of suppressing the interactions are also proposed.

Full-vectorial analysis of complex refractive-index photonic crystal fibers

We investigated the modal properties of complex refractive-index core photonic crystal fibers (PCFs) with the supercell model. The validity of the approach is shown when we compare our results with those reported earlier on a step complex refractive-index profile. The imaginary part of the electric field results in wave-front distortion in the complex refractive-index profile PCFs, which means that the power flows out or into the doped region according to the sign of the imaginary part of the refractive index. A simple formula is proposed for calculating the gain or loss coefficients of these fibers. The numerical results obtained by the approximation formula agree well with the full-vectorial results.

Anamorphic beam concentrator for linear laser-diode bar

An anamorphic beam concentrator for linear laser-diode (LD) bar is presented. It consists of a tapered SiO2-rod with skewed and curved surface. The principle and applicability of this device are numerically investigated by ZEMAX and experimentally illustrated for the specific example of the linear LD bar. Results show that a relative symmetrical output beam spot is produced at the output facet of the rod and the intensity and spatial fluctuations in the input beam are compensated at distance of 20cm from the output facet.

FTTH - a promising broadband technology

With the extraordinary increase of bandwidth requirement nowadays, service providers are compelled to push fiber deeper into the access networks in order to be able to offer the emerging services that customers are demanding. Fiber-to-the-home (FTTH) networks have always been the ultimate solution to a future broadband access network. In recent years, several technological developments have brightened the outlook on FTTH. The paper highlights these changes, and presents architectures that may be successfully deployed in the near future. The author estimates the value of FTTH and the foreground of its application and development in the world market.