Miniaturized and low-cost optical gyroscopes are urgently required for emerging applications in consumer electronics market. In this paper, we proposed a theoretical analysis and preliminary experiment results for integrated interferometric optical gyroscope based on the silicon-on-insulator (SOI) platform for the first time. The gyroscope is based on the Sagnac effect and composed of coiled multimode waveguides to reduce propagation loss and the footprint. The sensitivity of the sensing part is fully investigated in terms of waveguide loss, gyroscope footprint, crossing numbers for coiled waveguides, as well as the waveguide cross section. The experimental results show that gyroscope sensitivity is 51.3 deg/s with a footprint of 600 μm × 700 μm.

Abstract. Nowadays, forensic on flash memories has drawn much attention. In this paper, a recovery method for SQLite database history records (I.e. updated and deleted records) form YAFFS2 is proposed. Based on the out-of-place-write strategies in NAND flash memory required by YAFFS2, the SQLite history recorders can be recovered and ordered into timeline by their timestamps. The experiment results show that the proposed method can recover the updated or deleted records correctly. Our method can help investigators to find the significant information about user actions in Android smart phones by these history recorders, although they seem to have been disappeared or deleted.

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The mode-division-multiplexing (MDM) technology has become an alternative solution to further increase the link capacity in optical communication systems. Ultralow loss waveguide crossings for multimode waveguides are requisite in on-chip MDM systems. We propose and demonstrate an ultralow loss silicon multimode waveguide crossing using a combination of fully etched and shallowly etched waveguides in the multimode-interference coupler region to reduce the imbalance for two transverse electric polarized (TE) modes. By engineering the geometries and the proportion of the two waveguides, the self-imaging positions for different modes can coincide exactly. Simulated results show that the insertion losses are 0.043 and 0.084 dB for the fundamental TE (TE0) mode and the first-order TE (TE1) mode at 1550 nm, while the experimental values are 0.1 and 0.12 dB, respectively. The measured crosstalk is less than -30 dB for both modes within a 75 nm wavelength span.