We demonstrate theoretically and experimentally a novel in-fiber Mach-Zehnder interferometer (MZI) with piecewise interference spectrum. The interferometer is constructed by splicing a short section of single eccentric hole-assisted dual-core fiber (SEHADCF) to two single mode fibers (SMFs) with a lateral-offset. Due to the offset splicing and the small distance between cores, different core modes in two cores of the SEHADCF can be excited to form interference at the different wavelength ranges. The discontinuous region of the interference spectrum can be employed as a mark to identify the order of the interference valley. The in-fiber MZI is experimentally investigated as a refractive index sensor, the sensitivity of 353.9 nm/RIU is obtained in the RI range of 1.335 ~1.395. The in-fiber MZI with a high sensitivity has a great potential in biological and chemical applications. Especially, due to the ability to identify the order of interference valleys by the discontinuous region, the proposed in-fiber MZI can improve the reliability of fiber sensors in remote monitoring applications.
To improve the performance of the synchronization in OFDM systems in the presence of interference, a new synchronization algorithm based on scrambling sequence is proposed in this paper, which redesigns the training sequence with the constant amplitude zero auto-correlation (CAZAC) sequence and an extra scrambling operation. Compared with the traditional scrambling sequence-based algorithm, the simulations carried out both in AWGN and COST 207 4-path rural area (RA) channel show that the proposed synchronization algorithm can still maintain the sharper correlation peak, and achieve accurate symbol timing estimation and carrier frequency offset (CFO) estimation in the interference environment, with a lower out-of-band energy of the spectrum due to a new scrambling sequence. Furthermore, owing to the particularity of the component elements from the scrambling sequence, a low complexity implementation structure is presented here to realize the correlation function of the proposed algorithm with fewer hardware resources.
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