An efficient silicon three-waveguide spot size converter (SSC) featured by 180nm silicon photonic process node is proposed to deal with the butt coupling between InP-based quantum well laser diode (QW LD) and silicon on insulator (SOI) chip. With two sets of overlapped Si nanotapers employed at input facet of SSC, followed by a central Si waveguide tapered down to 450-nm-wide and 220-nm-high output facet, the coupling efficiency (CE) of mode conversion in transverse electric (TE) mode for a wavelength of 1342nm is calculated. The best coupling loss is 1.18dB at zero deviation and the tolerance of misalignment up to 1-dB loss increase are ±0.6μm for X axis and ±0.4μm for Y axis, respectively. The relatively low-loss transformation achieved by this structure shows less dependance of SiP process node better than 180nm. We also confirm that the coupling loss of three-waveguide SSC will be lower than 0.5dB if 140-nm-wide tip is allowed by more advanced process.
A system for detecting leakage of water pipeline is built based on the Raman distributed optical fiber sensing technique. Feasibility of the system is experimentally studied and a program for automatical alarm is developed. The results demonstrate that when the leakage of water causes a temperature variation no less than 1°C relative to the surrounding, the distributed optical fiber sensors are able to detect and locate the leakage. To some extent the water leakage spreading range can be shown, and when there are two or more leaks spaced by no less than 1m, the system can successfully identify the number of leaks.
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