Abstract
An approach to generating triangular-shaped waveform with variable symmetry based on two single-drive Mach-Zehnder Modulator is proposed and analyzed. By setting the bias state of modulators, the rotation angle of polarization controller, phase shift of phase shifters and the modulation index of modulators properly, triangular-shaped waveforms with different symmetry can be synthesized in time-domain. The detailed theoretical analysis and simulation are given. Triangular-shaped waveforms with different symmetry factor (0%–100%) are obtained in simulation. Compared with previous scheme for generating triangular-shaped waveforms with different symmetry, the generated triangular-shaped waveform in this paper is more similar to the ideal waveform.
Highlights
Generation of triangular-shaped waveform which is widely used in communication field, radar field and signal processing field [1]–[4] has been the hot research topic in the past decades
The researchers have proposed lots of schemes to generate symmetrical triangular waveform based on electronics solution or photonics solution, but the traditional electronics solution is not suitable for future development due to the disadvantages of low repetition rate, narrow bandwidth and not immune to the electromagnetic interference for generated waveform
A large number of schemes for symmetrical triangular waveform generation based on this method have been reported in the past decades, such as based on a single-drive Mach-Zehnder Modulator [7], modulator combined with dispersive fiber [8], [9], modulator combined with filter [10], [11], modulator combined with polarization devices [12], [13], stimulated Brillouin scattering [14] and optoelectronic oscillator [15]–[16]
Summary
Generation of triangular-shaped waveform which is widely used in communication field, radar field and signal processing field [1]–[4] has been the hot research topic in the past decades. The main thought of this method is to utilize external modulation to make optical intensity of generated signal approximately equal to the Fourier series expansion of ideal triangular waveform. The thought is to make the optical intensity of generated signal by external modulation approximately equal to the first three terms of Fourier series expansion of the ideal triangular-shaped waveform by adjusting phase shift of phase shifter and the DC bias voltage of modulator properly. Compared with the previous proposed scheme [20], the generated triangular-shaped waveform in this paper is to utilize optical intensity of the generated signal to be approximately equal to the first four terms of the Fourier series expansion of the ideal triangular-shaped waveform, which make the generated waveform is more similar to the ideal waveform
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