Abstract
In this paper, a novel photonic scheme for the generation of square and triangular waveforms is proposed and experimentally demonstrated by using a dual-drive Mach–Zehnder modulator (DDMZM) without any optical signal processing. By properly setting the modulation index of the DDMZM, the square and triangular microwave waveforms could be easily achieved in conjunction with a 90° hybrid coupler. Furthermore, the modulation index of the DDMZM could be tuned for a low radio frequency (RF) signal power requirement by tuning the phase difference of the RF signals applied to the two arms of the DDMZM. The proposed scheme for the photonic generation of microwave waveforms is theoretically analyzed and experimentally demonstrated. The periodical triangular and square waveforms with repetition rates of 5 GHz, 8 GHz, and 10 GHz are successfully obtained. The root-mean-square errors between the generated and theoretical triangular and square waveforms with a repetition of 5 GHz are 0.042 and 0.053, respectively.
Highlights
The photonic generation of a microwave waveform signal has become a quite attractive research area in recent years
The Mach–Zehnder modulator (MZM), a push-pull intensity modulator, which meant the input radio frequency (RF) signals loaded on the two arms had a π phase difference, was operated at the quadrature bias point to effectively suppress the even-order harmonics at a high input power
The optical signal from the TLS (NKT, E15) with the wavelength of 1549.955 nm, and the power of 8 dBm was sent to the dual-drive Mach–Zehnder modulator (DDMZM) (EOSPACE, 40 GHz)
Summary
The photonic generation of a microwave waveform signal has become a quite attractive research area in recent years. In paper [20], a MZM and a hybrid coupler were employed to generate triangular and square waveforms In this scheme, the MZM, a push-pull intensity modulator, which meant the input RF signals loaded on the two arms had a π phase difference, was operated at the quadrature bias point to effectively suppress the even-order harmonics at a high input power. We propose and experimentally demonstrate a simple photonic method for the simultaneous generation of square and triangular waveforms without any filtering or dispersive elements with a low RF signal power requirement This scheme only requires a sinusoidal RF source, a DDMZM, a RF power splitter in conjunction with a phase shifter, a photodetector (PD), and a 90◦ hybrid coupler. The pulse trains with repetition rates of 5, 8, and 10 GHz are successfully achieved, which guarantees the feasibility of the scheme
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