Lihui Feng

A Multi-Fork Z-Axis Quartz Micromachined Gyroscope

A novel multi-fork z-axis gyroscope is presented in this paper. Different from traditional quartz gyroscopes, the lateral electrodes of the sense beam can be arranged in simple patterns; as a result, the fabrication is simplified. High sensitivity is achieved by the multi-fork design. The working principles are introduced, while the finite element method (FEM) is used to simulate the modal and sensitivity. A quartz fork is fabricated, and a prototype is assembled. Impedance testing shows that the drive frequency and sense frequency are similar to the simulations, and the quality factor is approximately 10,000 in air. The scale factor is measured to be 18.134 mV/(°/s) and the nonlinearity is 0.40% in a full-scale input range of ±250 °/s.

Trellis-coded pulse amplitude modulation for indoor visible light communication

Trellis-coded pulse-amplitude modulation (TC-PAM) is applied in visible light communication (VLC) system using RGB-LED. Based on natural modulation, we propose a modified modulation to yield performance enhancement. Further, a decoding method of combing soft-decision Viterbi algorithm with most significant bit (MSB) decoding is developed. Finally, the results of Monte-Carlo simulation are presented to verify the best modulation and decoding method among the mentioned modulation and decoding techniques.

MMI power splitters based on the annealed proton exchange (APE) technology

The MMI optical power splitters which are based on the self-imaging effect (SIE) have been analyzed in the paper, and 1×4 MMI power splitter is designed. The designed device is simulated and optimized by Beamprop software, the simulation results are basically agreement with the designed effect, the excess loss induced by multimode interference is less than 0.04dB, uniformity is about 0.01dB.The low loss and fine uniformity MMI power splitter has been made by Lithium Niobate annealed proton exchange technology, and the experiment sample measurement results are achieved.

ANSYS simulation of the capacitance coupling of quartz tuning fork gyroscope

Coupling error is one of the main error sources of the quartz tuning fork gyroscope. The mechanism of capacitance coupling error is analyzed in this article. Finite Element Method (FEM) is used to simulate the structure of the quartz tuning fork by ANSYS software. The voltage output induced by the capacitance coupling is simulated with the harmonic analysis and characteristics of electrical and mechanical parameters influenced by the capacitance coupling between drive electrodes and sense electrodes are discussed with the transient analysis.

Study on digital correlation demodulation technology of micro quartz tuning fork gyroscope

A signal demodulation scheme for micro quartz tuning fork gyroscope based on digital correlation demodulation technology is proposed. In the operation of quartz gyroscope the reference signal should be in the resonance state with steady amplitude and the reference signal should be in-phase and has the same frequency with the driving signal. The quartz gyroscope signal processing platform is designed on the foundation of DEC6713 DSP development board successfully. The adaptive algorithm including the reference signal frequency tacking, the amplitude automatic gain controlling, the reference signal phase locking, and complex correlation demodulation are devised, and the algorithm is programmed. It is proved that the digital signal process scheme is feasible by means of experimentation.

Performance of optical DPSK and DQPSK in 40G bit/s transmission systems

We have simulated the OSNR sensitivity, filtering tolerance, chromatic dispersion tolerance, and nonlinear tolerance of optical DPSK and DQPSK formats with and without RZ carving in 40Gbit/s transmission systems. The results show that RZ-DPSK has the highest OSNR sensitivity, and is most robust against fiber nonlinearity in dispersion compensated systems with moderate channel spacing. The DQPSK systems have the highest filtering tolerance and dispersion tolerance, and is least affected by the reduction of the channel spacing. The simulations of long haul dispersion compensated systems show that RZ-DPSK has better performance in single channel system and WDM system with 100GHz channel spacing, while RZ-DQPSK has better performance in WDM system with 50GHz channel spacing.

10Gbit/s optical pulse wavelength conversion based on nonlinear optical loop mirror

All-optical wavelength conversion of 10Gbit/s optical pulse was realized by using nonlinear optical loop mirror composed by a dispersion-shifted fiber, the conversion wavelength range from 1520nm to 1558nm, the max wavelength span reach 38nm. Based on the Cross-Phase Modulation (XPM) in the NOLM, the control optical peak power and the polarization of two light were changed to achieve a large conversion wavelength range. And the converted optical spectrum was measured and the experiment results were discussed.

Weighted coupling to reduce sidelobe of the Integrated acousto-optic tunable filters

The Integrated acousto-optic tunable filter have the potential to perform the OADM or OXC functions, which play significant role in WDM optical network. The characteristic of the acousto-optic mode conversion is sinc2-like functions with high sidelobe intrinsic. The high sidelobe level lead to serious crosstalk in the WDM optical network. The theory of weighted coupling for IAOTF has been presented. And the filter response using four suggested weighted functions has been calculated with the matrix methods. Significant suppression of sidelobe level has been achieved by employing the techniques of weighted coupling. It is a valid approach to reduce the sidelobe of IAOTF by choosing propriety weighted function and a realized way.

Integrated optical TE/TM mode splitter using directional coupler

In the coming new general optical network, tunable filter is one of important optical devices, and can be used to compose dynamically optical add/drop multiplexer (OADM). Polarization independent integrated acousto-optic tunable filter (IAOTF) is one of devices which have most potential to perform the function[1][2]. Mode splitting and merging are realized by using two symmetrically directional couplers in the IAOTF. Mode polarization is converted by the acousto-optic mode converter when the condition of phase matching is met at the specifically light wavelength. The light wavelength passing the filter can be easily adjusted by changing the frequency of acoustic wave. The Ti diffused technology is adopted to fabricate the device on the X-cut Y propagation LiNbO3 slice. The relation of index difference in the X-cut Y propagation LiNbO3 waveguide with different diffusion conditions is computed in this paper. And the theory of coupling mode is utilized to analyze and design the directional coupler, in which TE/TM mode splitting can be realized. The designed structure is simulated by using BPM software. The extinction ratio of TE/TM mode can be reached 25. 1 dB and 24.9 dB respectively.