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The spectral efficiency and bit-error-rate (BER) of phase encoding optical code division multiple access (OCDMA) systems is evaluated, coherent time-spreading (TS) and spectral phase encoding (SPE) OCDMA systems are considered. The results indicate that SPE-OCDMA has better tolerance to performance degradation due to receivers bandwidth limitation than TS-OCDMA system, while for the practical en/decoders with implementable longest code length, TS-OCDMA can yield a spectral efficiency advantage over SPE-OCDMA systems.

Three-port tunable optical filter is a key device in the all-optic intelligent switching network and dense wavelength division multiplexing system. The characteristics of the reflecting spectrum, especially the reflectivity and the isolation degree are very important to the three-port filter. Angle-tuned thin film filter is widely used as a three-port tunable filter for its high rectangular degree and good temperature stability. The characteristics of the reflecting spectrum are greatly influenced not only by the incident angle, but also by the wedge angle parameter of the non-paralleled wedge thin film filter. In the present paper, the influences of the wedge angle parameter to the reflectivity and the half bandwidth are analyzed, and the reflecting spectrum characterstics are simulationed in different wedge angle parameter and polarity. The wedge angle-tuned thin film filter with 0.8° wedge angle parameter is fabricated. The experimental results show that keeping the wedge angle the same orientation to the incident angle will worsen the reflectivity and the rectangular degree of the reflecting spectrum. However, keeping the wedge angle orientation reverse to the incident angle will enhance the reflectivity and decrease the bandwidth, which will give higher reflectivity and isolation degree to the three-port filter than that of high parallel degree angle-tuned thin film filter.

The relation between properties of strontium aluminate phosphor and Al/Sr ratio was investigated.A series of strontium aluminate phosphors with different Al/Sr ratios from 1.0 to 12.0 were synthesized by solid-state method.The samples were characterized by X-ray diffraction and photoluminescence spectra.The results reveal that single phases of SrAl2O4:Eu2+,Dy3+,Sr4Al14O25:Eu2+,Dy3+ and SrAl12O19:Eu2+,Dy3+ are obtained with Al/Sr ratios of 2.0,3.5 and 10.0 respectively.When Al/Sr selects other values,the final products are mixture.Moreover,the emission spectra of the samples shift to blue-ultraviolet short wavelength from yellow-green long wave with the increase of Al/Sr ratios,which result from change of products' composition.

Radiative intensity in 6,658 and 281 directions in the hemispheric space was provided by the distribution of ratios of energy scattered by the medium or reflected by the boundary surface method (DRESOR) at the boundary of a two-dimensional enclosure filled with isotropic and anisotropic scattering medium, respectively. The dimensionless radiative heat flux achieved by the DRESOR method agreed well with those by other methods in the literature. Besides the polar angle, the intensity at the boundary varies significantly with the azimuthal angle, especially for the points close to the emitting source. In the anisotropic scattering media, the largest boundary intensity occurs with the largest forward scattering capability.

In this paper we have proposed a photonic crystal structure to enhance the coupling efficiency between photonic crystal waveguide (PCW) and the conventional dielectric waveguide. The proposed waveguide characterized with employing the taper structure and varying the holes’ radius in the taper. Two-dimensional (2D) finite-difference time-domain (FDTD) method has been used to analyze the structure. The simulation results show that the coupling efficiency can be achieved as high as 81.6% at the wavelength of 1.55um.

Angle-tuned thin film filter is widely used in the DWDM system for its broad tunable wavelength range and high rectangular degree. The transmissivity and the half bandwidth is greatly influenced not only by the incident angle, but also by the wedge angle of the non-paralleled thin film filter. In the present paper, the influences of the wedge angle on the transmissivity and the half bandwidth were detailedly analyzed. The proper wedge angle and the orientation can greatly improve the characteristics of the transmittance spectrum. The angle-tuned thin film filter with 0.8 degrees wedge angle was also fabricated. The experimental results show that keeping the wedge angle with the same orientation to the incident angle will worsen the transmissivity and the rectangular degree of the transmittance spectrum. However, keeping the wedge angle orientation reverse to the incident angle will greatly enhance the transmissivity and the rectangular degree of the filter and its tunable wavelength range will broaden by 10 nm.

We report here in detail a polarization-insensitive arrayed-waveguide grating (AWG) with an all-optical polarization state controller (AOPSC). Only the TE0 mode can exist in this device; the TM0 mode will be cutoff. An eight-channel AWG using 100-GHz channel spacing is designed. Through simulation, we found that no polarization dependence was measured in the wavelength response. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 42–44, 2003

A time-dependent distribution of ratios of energy scattered by the medium or reflected by the boundary surfaces (DRESOR) method was proposed to solve the transient radiative transfer in a one-dimensional slab. This slab is filled with an absorbing, scattering, and nonemitting medium and exposed to a collimated, incident serial pulse with different pulse shapes and pulse widths. The time-dependent DRESOR values, representing the temporal response of an instantaneous, incident pulse with unit energy and the same incident direction as that for the serial pulse, were proposed and calculated by the Monte Carlo method. The temporal radiative intensity inside the medium with high directional resolution can be obtained from the time-dependent DRESOR values. The transient incident radiation results obtained by the DRESOR method were compared to those obtained with the Monte Carlo method, and good agreements were achieved. Influences of the pulse shape and width, reflectivity of the boundary, scattering albedo, optical thickness, and anisotropic scattering on the transient radiative transfer, especially the temporal response along different directions, were investigated.

We theoretically design a power-efficient ultra-wideband pulse generator by combining three monocycle pulses with different weights. We also experimentally demonstrate a feasible scheme to generate such power-efficient ultra-wideband waveforms using cross-phase modulation in a single semiconductor optical amplifier. The designed ultra-wideband pulse fully satisfies the requirements for the spectral mask specified by the Federal Communications Commission with high power efficiency. In the experiment, a power-efficient ultra-wideband waveform with a pulse duration of 310 ps is achieved, and the power efficiency is greatly improved compared with that of a single monocycle pulse or a mixture of two monocycles.

We experimentally demonstrate an all-optical temporal differentiator using a high resolution optical arbitrary waveform shaper, which is based on liquid crystal on silicon switching elements, and both amplitude and phase of the spectrum are programmable. By designing specific transfer functions with the optical waveform shaper, we obtain first-, second-, and third-order differentiators for periodic pulses with small average errors. We also theoretically analyze the bandwidth limitation of optical waveform shaper on the differentiator.

A simple design of l-to-2 photonic data distributor is proposed. A proof-of-concept experiment is performed at 40 Gbit/s employing four-wave mixing and cross gain modulation in a single semiconductor optical amplifier. Correct output logic signals with high extinction ratios (over 11 dB) and clear open eyes are obtained, without using any additional input light beam. The scheme would be a promising candidate for future ultrafast all-optical signal processing applications.