An electro-optical tunable filter comprised of two paralleled identical long-period waveguide gratings is proposed in this paper. The filter has one input port and two separate output ports, outputting band-pass and band-rejection light respectively. Using poled electro-optical polymer material to fabricate its waveguide cores enable the filter's tuning speed to approach nanosecond order. With the aid of long-period waveguide gratings, the tuning range of the filter is Λ times larger than the conventional electro-optical filters. We built up a model to design and simulate the proposed tunable optical filter. We investigate the relationship between the parameters of the long-period waveguide grating and the characteristics of the tunable filter, such as tuning range and FWHM. The simulation results show that the tunable optical filter can realize high-speed tuning in the wavelength range of 1530 nm to 1560 nm, and the FWHM width can reach 0.8 nm. Compared with the conventional optical filters, the results show that a high-speed widely tunable optical filter with narrow pass band can be achieved.

Single mode propagation is an important requirement for optical waveguide devices for use with single-mode fiber, it can reduce the coupling loss .In this paper , a technique is used for calculating the field distribution of the polymeric Y-junction rib waveguide. The technique is based on the combination of the effective index method(EIM) and the variational method(VM).it is mixed between the advantages of each method and avoided their disadvantages, where EIM can make the calculations procedures simple but it has some difficult to find the field distribution ,other wise ,VM can be used with very good accuracy to find the field distribution. An algorithm is implemented to study the effect of the structure parameters on the field distribution of the polymeric Y-junction rib waveguide . In our simulation, the core layer is PU-FTC (n=1.65@1.3µｍ)，the cladding layers were NOA73 (n=1.54@1.3µｍ) and Epoxylite9653 (n=1.54@1.3µｍ).The obtained single mode rid waveguide structure parameters are：the core thickness is 1.5µｍ，the rib height is 0.2µｍ， the rib width is 5µｍ.

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