Optical　filter　based　on　microring　resonator　usually　has　drawbacks　such　as　narrow　bandwidth　and　larger　radius　of　curvature.　An　ultra-compact　optical　filter　consisting　of　rectangular　ring　resonator　incorporated　with　two　Mach-Zehnder　interferometers　is　proposed　and　optimized,　and　the　device　is　formed　by　trench-based　nanophotonic　frustrated　total　internal　reflection　couplers　and　total　internal　reflection　mirror-based　90o　bends　waveguide.　The　performances　such　as　transfer　function,　quality　factor,　and　transmission　characteristic　are　analyzed　by　using　statespace　representation　and　finite　difference　time　domain　(FDTD)　methods.　The　dependence　of　filtering　features　on　both　different　coupling　coefficients　and　loss　coefficients　is　calculated　with　state-space　representation　method.　The　FDTD　simulation　results　show　the　device　exhibits　an　asymmetric　wavelength　interleaver　filtering　effect　with　the　different　ratios　of　pass-band　and　stop-band　bandwidths　when　the　coupler　reflection　coefficient　is　close　to　the　coupler　transmission　coefficient.　The　quality　factor　of　about　3120　and　the　free　spectral　range　up　to　50.6　nm　are　observed　in　such　small　25　μm　×8　μm　chip　area　when　the　coupler　reflection　coefficient　is　far　larger　than　the　coupler　transmission　coefficient.　The　compact　configuration　of　device　layout　is　beneficial　to　the　extension　at　two-dimensional　directions　for　highly　dense　photonic　integrated　circuits.　©,　2015,　Chinese　Optical　Society.　All　right　reserved.