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Abstract: A type of Mach–Zehnder modulator based on optical bias method which use organic polymer DR1/PMMA as the ridge waveguide material is designed. Variations of the relations between effective indexes and the structure parameters include the width, height and thickness of ridge waveguide and the upper and lower cladding thicknesses are analyzed by the effective index method (EIM). A single microstrip electrode and the ridge waveguide have been used in this modulator to achieve velocity-match between light wave and microwave. The optical field and power are simulated by BPM using the above optimized parameters of the structure. The initial phase difference between the two arms achieves 89.8° and the extinction ratio achieves 27dB in this organic polymer Mach–Zehnder modulator. [Copyright &y& Elsevier]

Abstract: In order to shorten the branch length of Mach–Zehnder modulator, the asymmetric rib waveguide was researched in Mach–Zehnder electro–optic polymer modulator. Full vector finite difference beam propagation method was applied to analyze systematically their transmission loss with different parameters. The structure was optimized by choosing optimal design solution such as the rib width , the branch height , the outer slab width of core layer in bending waveguide and the length of the sine-bending waveguide . The results show that if symmetric rib waveguide is replaced by asymmetric rib waveguide, the length of branch waveguide could be reduced by 30% under the same conditions of transmission loss. The results will have a certain reference value to the design of polymer optical waveguide in M–Z modulator. [Copyright &y& Elsevier]

Abstract: Based on the extended nonlinear Schrödinger equation in an optical fibre with cubic–quintic nonlinearity, evolutions of the frequency chirps, shapes and spectra of Gaussian pulses are numerically investigated in the normal dispersion regime of an optical fibre. And the approximate analytical descriptions for the developing chirps are presented by adopting two methods. The distances of wave breaking are correspondingly obtained as well. The results show that, the positive (negative) quintic nonlinearity increases (decreases) the chirp amount and the fine structures and then makes the optical wave-breaking phenomena appear earlier (later). [Copyright &y& Elsevier]

Based on the principle and fabrication of the optical waveguide laser, and through the configuration of the energy level of Er3+/Yb3+ co-doped system, the time-dependent rate equations are formed and then solved by Runge-Kutta algorithm. The dynamic characteristic of the waveguide laser pumped unidirectionally by 980 nm LD is analyzed. The curves of the relaxation oscillation are drawn, showing that the photon number and inverted population vary alternately. The attenuation characteristic of the peak power is studied. It is gained that time constant changes with pump power, length of waveguide and the reflectivity of output mirror. Furthermore, the impact of the above three parameters on the frequency and end-time of relaxation oscillation is discussed. The frequency of relaxation oscillation is proportional to the pump power. Under high reflectivity conditions, the length of waveguide has a weak impact on the frequency. The end-time decreases as the three parameters increase. These features and results provide a theoretical basis for designing the Er3+/Yb3+ co-doped phosphate optical waveguide laser. [ABSTRACT FROM AUTHOR]

Based on the extended coupled nonlinear Schrödinger equations in an optical fiber with quintic nonlinearity (QN), the approximate analytical frequency chirps and the critical distances for the cross-phase modulation induced optical wave breaking (OWB) are discussed for the initial Gaussian optical pulses. Evolutions of the frequency chirps, shapes and spectra of pulses are numerically calculated in the normal dispersion regime. It is shown that, the approximate analytical frequency chirps accords well with the numerical ones at the initial evolution stages of the pulses. And the calculated approximate critical OWB distances accord well with the numerical ones only for the traditional OWB. In addition, for the positive QN and the negative one but with small absolute values, the traditional OWB can be observed. While for the negative QN with large absolute values, non-traditional OWB may occur. Namely, soliton pulse trains may develop during the pulse propagation. [ABSTRACT FROM AUTHOR]

An efficient and high-precision single parameter variational effective index method is proposed to investigate the polarization dispersion characteristics of polymer optical rib waveguides. The transverse distribution of the effective refractive index of the waveguide is calculated by using effective index method (EI), and the distribution of optical field is approximately expressed as piecewise functions in each sub-region. The optical field with high precision is obtained by variational effective index method (VEI), and the effective index of polymer rib waveguide is computed by scalar variational formula taking the improved piecewise functions as the accurate optical field distribution. Based on the vector wave equation that governs the guided modes, the effective index is modified by perturbation method (PM) to obtain more accurate dispersion characteristics. The dispersion characteristics and transverse field distributions of the fundamental and higher order modes are analyzed in polymer multimode rib waveguides with different structure parameters and dimensions. The method has advantages such as high precision, low calculation cost and high efficiency, which provides an analytical method for the fabrication of polymeric electro-optic devices. [ABSTRACT FROM AUTHOR]

Abstract: The novel optical coding scheme for all-optical analog-to-digital conversion has been proposed, in which asymmetrical Y-branch waveguide structures have been introduced to achieve the desired optical power splitting. The optical performance has been simulated by using finite-difference beam propagation method (FD-BPM), which shows that the designed component exhibits good coding performance. Experimentally, the optical coding component has been fabricated and measured. The optical power contrast between bit code 1 and 0 at output port is more than 37 dB, and measured imbalance of output power is less than 1.5 dB for bit code 1. [Copyright &y& Elsevier]