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Since the frequency offset estimation (FOE) must be implemented before the subcarrier de-multiplexing and chromatic dispersion compensation (CDC) for digital subcarrier multiplexing (DSM) signals, traditional FOE algorithms for single carrier transmission is no longer suitable. Here, we propose a hardware-efficient blind FOE solution for the DSM signals by monitoring spectral dips in the frequency domain. With the use of a smoothing filter, the estimation accuracy of FOE can be significantly increased. Moreover, we identify that the proposed FOE method is robust to various transmission impairments, including amplified spontaneous emission (ASE) noise, optical filtering, and fiber nonlinearity. The effective function of the proposed FOE method is numerically and experimentally verified under scenarios of both back-to-back (B2B) and the 2560 km standard single-mode fiber (SSMF) transmission, leading to a FOE error less than 100 MHz with a FFT size of 1024.

According the radial flutter extension structure problems in commonly used fire alarm system, a novel topology structure of fire alarm systems based-on holographic crystal forms was proposed. It was composed of multiple devices, including intelligent fire detectors, which can communicate with each other, record fire information and judge, alarms, security, evacuation lights etc. Each device can record all of the information so as to form the hologram. These devices on each floor level in buildings and decorated with vertical layout in the staircase, so that fire alarm system topology based-on holographic crystal forms was set up. The systems can ensure the normal operation of other devices in case that central control equipment failed in extreme cases. And then the automatic fire safety equipment continued to automatically control fire rescue and guide the staff in the correct escape route. Moreover, when a device or a line goes wrong, only failure equipment or system was cut off line, and others were still able to keep communications. Compared with other methods, this new system does not affect the normal equipment of the work.

SVPWM controller is an important part of three-phase inverter. The paper is introduced the realization process for SVPWM controller based on EP3C40Q240C8 FPGA chip. The experimental results show that the control method is valid and feasible.

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