Photonic generation of microwave signals using dual-wavelength single-longitudinal-mode fiber lasers

Photonic generation of microwave signals is demonstrated with a dual-wavelength single-longitudinal-mode erbium-doped fiber ring laser. Microwave signal with a frequency of 21.07 GHz is obtained by aligning the reflection band of a uniform fiber Bragg grating to the two transmission peaks within a fiber Bragg grating-based Fabry-Perot filter. Stable dual-wavelength single-longitudinal-mode operation is guaranteed by means of the combined filtering effect of a saturable absorber and the Fabry-Perot filter. This approach provides an effective solution to the photonic generation of high-frequency microwave signals.     

Single-longitudinal-mode fiber ring laser using fiber grating-based Fabry-Perot filters and variable saturable absorbers

A single-longitudinal-mode (SLM) fiber ring laser is demonstrated by incorporating a fiber Bragg grating (FBG)-based Fabry-Perot (F-P) filter and a variable saturable absorber in a fiber ring cavity. An ultra-narrow bandpass filter is established by the combined mode filtering of the FBG-based F-P filter and the variable saturable absorber. No accurate control for cavity length is required, and stable single longitudinal-mode operation without mode hopping is conveniently achieved.     

Photonic generation of microwave signal using a dual-wavelength single-longitudinal-mode distributed Bragg reflector fiber laser

In this paper, a novel all-optical microwave generation technique based on a dual-wavelength single-longitudinal-mode (SLM) distributed Bragg reflector (DBR) fiber laser is proposed and demonstrated. By exploiting spatial hole burning (SHB) effect, this laser could provide stable dual-wavelength SLM operation with a wavelength separation of 0.088 nm corresponding to the microwave signal at 10.484 GHz with a 3 dB bandwidth of 28 kHz. By appropriately adjusting the pump power, dual-wavelength oscillation could be maintained at different temperatures. We have theoretically analyzed the mechanism for microwave generation of the proposed DBR laser, and the calculated microwave frequency is in good agreement with our experimental results. Furthermore, experimental observation shows both of the laser wavelengths and generated microwave signals have good stability at room temperature.     

Photonic generation of microwave arbitrary waveforms

In this paper, techniques to generate microwave arbitrary waveforms based on all-fiber solutions are reviewed, with an emphasis on the system architectures based on direct space-to-time pulse shaping, spectral-shaping and wavelength-to-time mapping, temporal pulse shaping, and photonic microwave delay-line filtering. The generation of phase-coded and frequency-chirped microwave waveforms is discussed. The challenges in the implementation of the systems for practical applications are also discussed.     

A tunable and switchable single-longitudinal-mode dual-wavelength fiber laser incorporating a reconfigurable dual-pass Mach-Zehnder interferometer and its application in microwave generation

A tunable and switchable single-longitudinal-mode (SLM) dual-wavelength fiber laser incorporating a reconfigurable dual-pass Mach-Zehnder interferometer (MZI) filter was proposed and demonstrated, which can be applied in microwave generation. By incorporating a high extinction ratio (ER) dual-pass MZI into an erbium-doped fiber ring cavity, SLM dual-wavelength lasing can be achieved even using a MZI with relatively little free spectrum range (FSR), and by beating the two wavelengths at a photodetector, a 9.76 GHz microwave signal with a 3-dB bandwidth of less than 10 kHz is obtained. Moreover, by direct linking the two outputs of the MZI, the high ER dual-pass MZI is easily reconfigured as a half FSR dual-pass MZI. Using this structure, switchable SLM dual-wavelength lasing can be conveniently realized.     

光纤激光陀螺线宽压缩技术中滤波器的结构设计与分析

研究了光纤激光陀螺系统中滤波器对激光光谱线宽压缩的影响。在理论分析的基础上,提出了用于光纤激光陀螺的Fabry Perot腔滤波器的方案,并进行了结构设计。试验证明FP腔滤波器可以达到满意的滤波效果。     

Photonic generation of a microwave signal by employing a microfiber ring resonator

A novel approach to generate microwave signals is presented by employing a microfiber ring resonator. The microfiber ring resonator is assembled with a microfiber fabricated by heating and drawing standard single-mode fiber. By cascading microfiber ring resonator acted as a comb filter with a tunable bandpass filter, a wavelength-tunable dual-wavelength single longitudinal-mode laser is achieved. A microwave signal at 15.57 GHz with the linewidth of less than 21 kHz is demonstrated by beating the two wavelengths at a photodetector.     

An investigation of quantum-chaotic signals generation using a fiber ring resonator and an add/drop multiplexer

We successfully generate the double security using a fiber ring resonator incorporating an add/drop device, whereas the quantum-chaotic encoding of light in a single fiber ring resonator is constructed. In the experiment, the nonlinear Kerr effects in the fiber ring resonator induced the chaotic wave form within the fiber ring resonator, which could be used to scramble or encode into the original signals. The laser input power used was 15 mW, with a fiber ring radius of 50 cm. We found that the double security can be formed, where the randomly polarized photons could be controlled by using the polarization controller and observed.     

Tunable erbium-doped fiber ring laser for applications of infrared absorption spectroscopy

We fabricate a low noise erbium-doped fiber ring laser that can be continuously tuned over 102 nm by insertion of the fiber Fabry-Perot tunable filter (FFP-TF) in the ring cavity with a novel cavity structure and the optimal gain medium length. As an application of this fiber ring laser, we performed the absorption spectroscopy of acetylene (¹³C₂H₂) and hydrogen cyanide (H¹³C¹⁴N) and measure the absorption spectra of more than 50 transition lines of these gases with an excellent signal to noise ratio (SNR). The pressure broadening coefficients of four acetylene transition lines are obtained using this fiber ring laser and an external cavity laser diode.     

High frequency microwave signal generation using dual-wavelength emission of cascaded DFB fiber lasers with wavelength spacing tunability

A dual-wavelength fiber laser source based on two cascaded phase-shifted fiber Bragg gratings is presented. The gratings are written in an erbium-doped fiber, each configuring the cavity of a distributed feedback fiber laser. The spacing between lasing modes is controlled dynamically by the use of piezoelectric actuators. A continuous tuning range of 5-724 pm of the wavelength difference, which is equivalent to a photodetected 0.72-92 GHz range, is obtained. Efficient generation from the L to the W microwave and millimeter bands has been achieved by heterodyne photodetection of the dual-wavelength optical signal.     

虚阴极振荡器中微波产生的解析理论

 用解析方法研究了虚阴极振荡器中微波产生的机理, 给出了小信号增益公式和饱和功率的标度。由此得到的结论是: 虚阴极振荡器的辐射一般情况下是由相位受到RF场调制的从虚阴极反射的电子束流产生的, 当注入电流稍大于第一临界电流时，有最高辐射增益区，但反射电流较小；当注入电流稍大于第二临界电流时，有较高辐射增益区，反射电流也较大。     

虚阴极振荡器中微波产生的解析理论

用解析方法研究了虚阴极振荡器中微波产生的机理, 给出了小信号增益公式和饱和功率的标度。由此得到的结论是: 虚阴极振荡器的辐射一般情况下是由相位受到RF场调制的从虚阴极反射的电子束流产生的, 当注入电流稍大于第一临界电流时,有最高辐射增益区,但反射电流较小;当注入电流稍大于第二临界电流时,有较高辐射增益区,反射电流也较大。     

Photonic generation of ultrawideband signals by exploiting gain saturation of dark pump pulse with double undershoots in a highly nonlinear fiber

We have proposed and theoretically demonstrated an alternative photonic scheme to generate ultrawideband (UWB) doublet pulses based on gain saturation effect in one piece of highly nonlinear fiber (HNLF). A flexible format swap between UWB doublet and monocycle pulses can be successfully realized by properly tuning the optical tunable delay line (ODL). Moreover, the key parameters for UWB pulse, including the center frequency (Fc), 10 dB bandwidth (BW_10dB), and fractional bandwidth (FBW), are also investigated with Fc being Einstein shift when the doublet pulse transforms into the monocycle pulse. Finally, our proposed scheme exhibits good performance that the obtained UWB pulse can have a FBW of > 100% at the Fc of ~ 7 GHz and UWB-over-fiber technology is also implemented without dispersion management.     

Control of microwave signals using bichromatic electromechanically induced transparency in multimode circuit electromechanical systems

We theoretically investigate the tunable delay and advancement of microwave signals based on bichromatic electromechanically induced transparency in a three-mode circuit electromechanical system, where two nanomechanical resonators with closely spaced frequencies are independently coupled to a common microwave cavity. In the presence of a strong microwave pump field, we obtain two transparency windows accompanied by steep phase dispersion in the transmitted microwave probe field. The width of the transparency window and the group delay of the probe field can be controlled effectively by the power of the pump field. It is shown that the maximum group delay of 0.12 ms and the advancement of0.27 ms can be obtained in the current experiments.