A new photonic scheme for various waveforms generation has been proposed and demonstrated. In the scheme, two cascaded single-drive LiNbO₃ Mach-Zehnder modulators serve as pulse shaper and the polarization-dependent character of the modulators is fully exploited and utilized. By arranging the polarization states of the incident light, two different spectra are achieved on two orthogonal polarization components respectively. Finally, the desired waveforms can be obtained by superimposing the photocurrents of the two orthogonal signals on a photodetector. The detailed theoretical analyses and simulations are given. In the experiment, square-shaped waveform, triangular waveform and sawtooth (or reversed-sawtooth) waveform are obtained successfully. Furthermore, an approach to smoothing the sawtooth waveform with fewer harmonics is suggested and verified.

A photonic method of sawtooth waveform generation by using one single-drive Mach-Zehnder modulator is proposed and experimentally demonstrated. Depending on the polarization-sensitive characteristic of the modulator, the modulation sidebands and optical carrier can independently exist on two orthogonal polarization directions. Therefore, the required Fourier components can be manipulated on two polarization dimensions separately, and the superposition of the orthogonal optical envelopes synthesize a sawtooth waveform in time domain. The feasibility of the scheme is theoretically analyzed. In the experiment, sawtooth waveforms with full duty cycle at 3, 5, and 8 GHz are obtained, which agree with the simulation results well.

In this Letter, we propose a simple structure of an orthogonal type double Michelson interferometer. The orthogonal detection method overcomes the problems of uneven ranging sensitivity and the inability of traditional interferometers to determine the displacement direction. The displacement measurement principle and signal processing method of the orthogonal double interferometer are studied. Unlike the arctangent algorithm, the displacement analysis uses the arc cosine algorithm, avoiding any pole limit in the distance analysis process. The minimum step size of the final experimental displacement system is 5 nm, which exhibits good repeatability, and the average error is less than 0.12 nm.

We propose a weak radio frequency (RF) signal detection scheme based on single-mode optoelectronic oscillator (OEO). In this scheme, the phenomenon of injection locking is avoided by using the structure of phase-locked loop (PLL), which guarantees that the OEO works under the quasi-locked condition. The structure of PLL also stabilizes the gain provided to the RF signal under detection. Consequently, the maximum gain provided to the RF signal under detection is 59.49 dB and the detection sensitivity is -120 dBm.