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2 Optica Applicata

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Generation of chirped microwave signal with any central frequency based on a nonuniformly spaced finite impulse response filter

100%

Chen D. , Wang R. , Pu T. , Xiang P. , Fang T. , Zheng J. , Xiong J.

Optica Applicata

2016

tom Vol. 46, nr 3

399--408

A novel optical approach to generating a chirped microwave signal by using a nonuniformly spaced finite impulse response filter is proposed and demonstrated. In this scheme, a narrowband Gaussian pulse is used as the original chirped-free signal, which is easy to be acquired. To eliminate the need of a wideband chirped-free signal, a mixer and a radio frequency signal are used to up-convert the spectrum of the original Gaussian signal. Therefore, the required frequency response can be calculated and reconstructed by a finite impulse response filter with nonuniformly spaced taps. Besides, a dual drive Mach–Zehnder modulator is used to realize single sideband modulation of the chirpedfree signal. Thus, the transfer function induced by the fiber dispersion is eliminated and the chirped microwave signal with any central frequency can be generated. In this paper, a design example of a filter with a central frequency of 10GHz is provided, and generation of the target chirped microwave signal is also demonstrated by numerical simulations.

Dispersion-compensating en/decoder for a time-spreading/wavelength-hopping optical code-division multiplexing (OCDM) system

84%

Zheng J. , Wang R. , Pu T. , Lu L. , Fang T. , Su Y. , Li L. , Yang Q. , Chen X.

Optica Applicata

2013

tom Vol. 43, nr 3

485--495

A novel dispersion-compensating fiber Bragg grating (FBG)-based en/decoder is proposed to compensate both the out-band and in-band dispersion in a time-spreading/wavelength-hopping (TS/WH) optical code-division multiplexing (OCDM) system. The experimental realization of such en/decoders only needs a uniform-pitch phase mask and a sub-micrometer precision moving stage. Such an en/decoder pair with the ability of compensating the dispersion of transmission in 20-km single mode fiber (SMF) is simulated and experimentally fabricated. Both the simulation and experimental results show that the decoded pulse can be recovered without any distortion owing to the elimination of dispersion.