MEMS Fabry-Perot tunable filter is obviously notable because of its mass production and easy integration. Membrane is the key portion of the filter as its structure directly affects the filter's performance and fabricating difficulty. In this paper, some typical membrane structures with different dimensions are simulated. Through making finite element analysis to these simulations and comparing of the results, we find out useful information such that foldaway and spiral cantilevers can achieve longer length in the same membrane area; the longer cantilevers are, the smaller electrostatic force is needed, accordingly the bias voltage is lower and the membrane curvature is smaller, etc. Then we use the information to analyze some important factors affecting membrane's physical and optical performance and make an optimization design.

In the paper, a weighted-coupling scheme of a SiO2 film-loaded Ti:LiNbO3 quasi-collinear integrated acousto-optic mode converter is reported, in which an angular offset between the acoustic and optical waveguides is introduced to implement an optimized Hamming weighted function for realization of ultralow sidelobe level. Acoustic wave guiding properties have been investigated for films such as SiO2, ZnO on LiNbO3 firstly. SiO2 film on LiNbO3 was selected as acoustic waveguide. With the mode analysis of the acoustic wave guide and the theory of coupling mode the limit of the width, weighted coupling coefficient and the characteristics of the conversion of acousto-optic modes are obtained. As the angle between acoustical and optical waveguides guides is 0.45ο, the worst sidelobe level is −16.8dB and the theoretical values of bandwidths of−3dB and −10dB is 1.37nm and 2.31nm respectively, which have excelled the domestic reported level.

The acousto-optic tunable filter (AOTF) for wavelength division multiplexing (WDM) applications has attracted much attention. The important reason is that it may realize the multi-wavelength optical cross-connect. This enables the AOTF to become a promising optical component in the future intelligent optical communication networks. The TeO2 AOTF has a specific structure with the capability of both functions of wavelength division and space division. This feature will lead to TeO2 AOTF's lower crosstalk. In this paper, the coupling equations with multiple acoustic waves traveling simultaneously are presented. The analytic solution of the diffraction efficiency for the two acoustic frequencies is given, and its impact on the device performances is analyzed. The crosstalk of the TeO2 AOTF as an OADM in WDM system is discussed, which shows that it is superior to the IAOTF on crosstalk.

In the paper the electric controlled optical tunable filter as a MOEMS device based on the FP resonant cavity on silicon, which will be potentially used in the dense wavelength division multiplexing (DWDM) system, is introduced. It can be used mainly as a wavelength division multiplexer in a DWDM system, and can be used as a optical add-drop multiplexer (OADM) in an all-optical switch system. Its basic operation principle is that one of the two mirrors is made into an elastic membrane structure, then the cavity length is varied under the driving of the electric field force, and the wavelength tuning be realized. The parameters of its characters, the working principle and the basic structure of the device are analyzed and calculated, including the optical properties, for instance, the tunable spectral range, the 3 dB bandwidth, the finesse, and the insertion loss, the structural properties, for instance, the deformation of the elastic membrane under the electric field force, the mechanics property and the couple performance, for instance, the electromechanical couple between the membrane of the FP cavity and the applied electric field. According to the required performances of the device and the subsystem, the preliminary design is performed combining the technique condition. From the analyzed results, the advantages of minuteness volume, low insertion loss, and high adjustment precision are clearly known.

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.