A multi-period-delayed feedback (MPDF) photonic circuit constructed by a Sagnac ring and two coupled rings was designed. By coupling a distributed feedback (DFB) laser diode (LD) with the MPDF, a narrow linewidth semiconductor laser was demonstrated. The linewidth of the DFB-LD with MPDF was narrowed to be around 2 kHz, which is reduced by three orders of magnitude, and the linewidth reduction capability could be maintained when the wavelength of the DFB-LD was tuned in a range wider than 3 nm. The laser frequency stability can also be improved using the proposed technique, and the frequency fluctuation was reduced for nearly 8 times in comparison with the DFB-LD.
A novel optical frequency-hopping system based on distributed feedback laser integrated with an electroabsorption modulator is proposed and demonstrated. In the proposed system, a user's data are split into segments and modulated onto multiple optical frequency shift keying carries, therefore, a single wavelength of optical carrier only carries partial user's data. By this way, the security of optical communication system is improved. In this paper, we demonstrate an error free transmission through 32-km single mode fiber and 8-km dispersion compensation fiber with 2.5 Gb/s hopping rate and 10 Gb/s data rate. Meanwhile, we also compare and analyze the performance of the proposed system with different hopping rate and data rate.
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