Photonic Generation Of Microwave Waveforms Research Articles

A Simple Photonic Generation of a Microwave Waveforms Scheme Based on a Dual-Polarization Dual-Drive Mach-Zehnder Modulator

In this paper, a simple scheme for the generation of sawtooth, triangular, and square waveforms using an integrated dual-polarization dual-drive Mach-Zehnder modulator (Dpol-DDMZM) is proposed. By properly setting the working point and the modulation index of the Dpol-DDMZM, the desired microwave waveforms are easily obtained after photodetection. The proposed scheme for the photonic generation of microwave waveforms is analyzed both by simulation and experiment. The periodical sawtooth, triangular, and square waveforms with repetition rates of 8 GHz are successfully generated. The root-mean-square errors (RMSE) are 0.190, 0.168, and 0.135, respectively. The system features flexible tunability.

A Simple Scheme for Photonic Generation of Microwave Waveforms Using a Dual-drive Mach–Zehnder Modulator

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.

Simple and Flexible Photonic Microwave Waveform Generation With Low RMSE of Square Waveform

A simple and flexible photonics-assisted approach based on an integrated polarization-division multiplexing Mach–Zehnder modulator (PDM-MZM) and a balanced photodetector (BPD) to generating microwave waveform is proposed. The sub-MZMs of PDM-MZM are biased at peak and null points. Square and trapezoid waveforms are generated by controlling the PC and driven sinusoidal signal power. Triangle and sawtooth waveforms are also obtained with the help of a 90° microwave phase shifter (MPS). The proposed approach features simple structure, flexible frequency tunability, and easy implementation. Moreover, the problem of high root-mean-square error (RMSE) of square waveform is solved by this approach for the first time. An experiment is conducted to verify the approach. Different waveforms with the repetition rates of 3 and 5 GHz are generated. The RMSE of square waveform is reduced from 0.3328 to 0.2048 which is the lowest RMSE to the best of our knowledge.

Photonic microwave waveform generation based on dual-wavelength time domain synthesis technology

<sec>Microwave waveforms, such as square waveforms, sawtooth waveforms and triangle waveforms are widely used in radar communication, electronic measurement and medical imaging and so on. Using photonic microwave technology to generate arbitrary microwave waveforms has been a research hotspot.</sec><sec>In this paper, a photonic microwave waveform generation scheme based on dual-wavelength time domain synthesis is proposed and experimentally demonstrated. Used in this scheme mainly are two lasers, two single-drive Mach-Zehnder modulators, a wavelength division multiplexer and a tunable optical delay line. The two Mach-Zehnder modulators are respectively biased at different operating points. When two beams with different wavelengths are superimposed in the time domain, different microwave waveform outputs can be generated. Therefore, by adjusting the bias voltage and modulation depth of the modulator, the phase and amplitude of the modulated optical signal can be controlled, and finally the photonic microwave waveform is generated.</sec><sec>At first, the generation mechanism of square waveform, sawtooth waveform and triangle waveform are analyzed, and the comparisons among ideal square waveform, sawtooth waveform, triangle waveform and their third-order waveforms are made through the simulation analysis. It is verified that third-order waveforms become close to the ideal waveforms. Since the proposed scheme produces higher-order components, and the waveforms of the first three orders are the same as the ideal waveforms, so the scheme has good waveform generation capability. And then square waveform, sawtooth waveform and triangle waveform with a repetition rate of 2.5 GHz are successfully generated experimentally. Thus, experimental results are well consistent with the theoretical analyses. In addition, the system also has good tunable characteristics. By changing the modulation frequency of the modulator, the frequency tuning of the output photonic microwave waveforms can be realized, and square waveform, sawtooth waveform and triangular waveform with a repetition rate of 5 GHz are also experimentally achieved. The repetition rate of the generated microwave waveform is mainly limited by the bandwidth of modulator and electrophotonic detector, so the devices with higher bandwidth can be used to generate arbitrary waveform with a higher repetition rate. Therefore, the scheme has good application prospects.</sec>

Photonic generation of microwave waveforms based on a dual-polarization quadrature phase-shift-keying modulator.

A novel microwave waveform generator based on a dual-polarization quadrature phase-shift-keying (DP-QPSK) modulator is proposed and experimentally demonstrated in this paper. The X-QPSK modulator is modulated by a local oscillator signal. For XI Mach-Zehnder modulator (MZM), odd sidebands are eliminated; for XQ-MZM, even sidebands are eliminated, while the Y-QPSK modulator is not modulated. Triangular or square waveforms can be generated by biasing the X-QPSK and adjusting the polarization controller properly. 3GHz and 6GHz triangular and square waveforms are successfully generated by experiment. The scheme does not need a high modulation index (m=1.25 in this paper). In addition, it features low cost and a simple structure without a filter or phase shifter.

Photonic generation of microwave waveforms based on a dual-loop optoelectronic oscillator

A novel photonic scheme of microwave waveforms generator based on a dual-loop optoelectronic oscillator (OEO) is experimentally verified. A 10-GHz microwave signal generated by OEO is modulated onto the directly modulated laser (DML) and the phase modulator (PM) simultaneously. By adjusting the driven power of the DML and the PM and the phase difference between the pulse signal inputted into the PM and the PM’s driven signal, the desired optical spectrum is obtained. By passing appropriate dispersion, the optical spectrum can be converted into desired waveform. In this experiment, a series of waveforms with the shapes of sawtooth/reversed-sawtooth, triangle, and pulse are generated.

Photonic Microwave Waveforms Generation Based on Frequency and Time-Domain Synthesis

In this paper, a novel photonic microwave waveform generation method with both frequency-domain synthesis (FDS) and time-domain synthesis (TDS) is proposed, for the first time to the best of our knowledge, by using cascaded modulation and an optoelectronic oscillator. By controlling the spectral lines in a polarization-modulated optoelectronic oscillator (P-M-OEO), a triangular waveform is generated according to the FDS, where a parallel part of the optimum modulation axis of the Mach–Zehnder modulator (MZM) executes carrier suppression in the P-M-OEO, while its orthogonal part is left unmodulated. A quasi-rectangular waveform is then generated by directly modulating another MZM at the quadrature point. Additionally, a sawtooth or reversed-sawtooth waveform with 50% duty cycle and 100% duty cycle can be generated in TDS. In the experiment, a 3-GHz triangular waveform, a 3-GHz high-quality microwave signal, a 6-GHz frequency doubling signal, a 3-GHz quasi-rectangular waveform, a 3-GHz 50% duty cycle sawtooth or reversed-sawtooth waveform, and a 100% duty cycle sawtooth or reversed-sawtooth with frequency doubling are obtained simultaneously. The results verify the feasibility of the proposed scheme, and it holds a potential candidate for applications in photonic microwave signals.

Photonic microwave waveform generation based on phase modulation and tunable dispersion.

Photonic generation of microwave waveforms is currently an interesting topic due to the advantages of large bandwidth and immunity to electromagnetic interference. In this paper, a photonic microwave waveform generator with tunable waveforms and repetition rates is proposed and experimentally demonstrated. A continuous-wave (CW) light is phase modulated by a local oscillator (LO) signal to generate optical sidebands. By locating the phase modulator (PM) in a Sagnac loop, we can control the intensity and phase of the carrier of the phase modulated signal. Then a compact tunable dispersion compensation module is used to introduce phase shifts to the optical sidebands. Thanks to the flexible controlling of the optical signal, the generation of microwave waveforms with tunable shapes and repetition rates can be realized. In the demonstration experiment, full-duty-cycle triangular and square waveforms with repetition rates of 5 and 10 GHz (bandwidths of 15 and 30 GHz) are successfully generated, respectively. The bandwidths are expected to be improved to above 120 GHz if larger-bandwidth measurement instruments are used. In addition to the flexible tunability, the proposed scheme also features the advantages of easy implementation and free from bias drift.

Photonic generation of microwave waveforms with wide chirp tuning range

We show analytically as well as demonstrate experimentally an approach to generate microwave waveforms with wide chirp tuning range. The approach is based on the interference of two temporally-stretched pulses which are time-delayed with respect to each other and having different frequency chirp. This approach is realized by an unbalanced Mach Zehnder Interferometer (MZI) incorporating a linearly-chirped fiber-Bragg-grating (LCFBG) whose group-delay-dispersion (GDD) can be tuned across a wide range. In general, tuning the GDD of the LCFBG changes the chirp rate of the generated microwave waveform and tuning the relative time-delay between the interferometer arms changes the center frequency of the generated microwave waveform. Balanced photodetection is also implemented to obtain DC-free microwave waveforms. Based on this approach, we demonstrate the generation of microwave waveforms with different center frequencies and with the chirp rates ranging from∼−126.7GHz/ns to ∼+120.8GHz/ns, including the zero-chirp case.