Bingkun Zhou

Efficient, frequency-stable laser-diode-pumped Nd:YAG laser

We have designed and tested a laser-diode-pumped monolithic Nd:YAG oscillator. The electrical-to-optical slope efficiency was 6.5%. The frequency jitter was less than 10 kHz over a 0.3-sec period, the best frequency stability reported for a Nd:YAG laser to date.

Highly Linear Radio-Over-Fiber System Incorporating a Single-Drive Dual-Parallel Mach–Zehnder Modulator

We propose a highly linear radio-over-fiber system with low intermodulation distortion (IMD) using a single-drive dual-parallel Mach-Zehnder modulator (SD-DPMZM). The optical carrier is modulated in one of the two parallel modulators, while remaining unmodulated in the other one. There exists optimal working points for SD-DPMZM that makes its two kinds of origins of third-order IMD (IMD3) have opposite phase and equal intensity, and cancel each other; hence the output IMD3 is suppressed dramatically. Experimental results show that the proposed scheme can achieve a spurious-free dynamic range of up to 122.9 dB · Hz2/3, which is in agreement with the theoretical analysis. It is about 20 dB more than a conventional MZM. The error vector magnitude of the proposed scheme, for a 16-QAM 10-MSym/s signal centered at 4 GHz, is 1.94%.

Compensation of dispersion-induced power fading for highly linear radio-over-fiber link using carrier phase-shifted double sideband modulation.

A carrier phase-shifted (CPS) double sideband (DSB) modulation technique in radio-over-fiber (RoF) system is proposed and experimentally demonstrated. By tuning the biases in a single-drive dual parallel Mach-Zehnder modulator (SD-DPMZM), the optical carrier in the DSB spectrum acquires additional phase shift. The transmittance response of a dispersive RoF link is thus being controlled and shifted in the frequency domain. Experiments successfully turned the maximum transmission frequency to 10 GHz and 15 GHz for both 25 and 39 km fiber links. This is also a highly linear scheme, of which a spurious-free dynamic range (SFDR) of 111.3 dB·Hz2/3 is experimentally obtained.

Highly efficient acoustooptic tunable filter based on cladding etched single-mode fiber

The efficiency enhancement of an acoustooptic tunable filter on cladding etched single-mode fiber (SMF) is investigated experimentally. When the fiber diameter is etched down to 30 /spl mu/m, the acoustooptic coupling efficiency from the LP/sub 01/ core mode to the LP/sub 11/ cladding mode was increased by an order of magnitude, and the RF power consumption was reduced by two orders of magnitude. A highly efficient 8-cm-long 25-/spl mu/m-thick AOTF on cladding etched SMF with an insertion loss of <0.2 dB, and RF power as low as 1.1 mW was demonstrated.

Potential for coherent Doppler wind velocity lidar using neodymium lasers

Existing techniques for the frequency stabilization of Nd: YAG lasers operating at 1.06 μm, and the high-gain amplification of radiation at that wavelength, make possible the construction of a coherent Doppler wind velocity lidar using Nd:YAG. Velocity accuracy and range resolution are better at 1.06 μm than at 10.6 μm at the same level of the SNR. Backscatter from the atmosphere at 1.06 μm is greater than that at 10.6 μm by ~2 orders of magnitude, but the quantum-limited noise is higher by 100 also. Near-field attenuation and turbulent effects are more severe at 1.06 μm. In some configurations and environments, the 1.06-μm wavelength may be the better choice, and there may be technological advantages favoring the use of solid-state lasers in satellite systems.

Postcompensation for nonlinearity of Mach-Zehnder modulator in radio-over-fiber system based on second-order optical sideband processing.

A postcompensation technique for nonlinearity of a Mach-Zehnder modulator in a radio-over-fiber (ROF) system is proposed and experimentally demonstrated based on second-order optical sideband processing and optical carrier band attenuation. The phase of the second-order optical sideband is shifted to suppress the third-order intermodulation distortion (IMD3) in a direct detection ROF link. The optical carrier band is attenuated to make two kinds of origins of IMD3 have equal intensity and cancel each other out. A spurious-free dynamic range of 124.8 dB·Hz(2/3) is achieved, which is about 25 dB more than that without compensation.

Highly reconfigurable microwave photonic single-bandpass filter with complex continuous-time impulse responses

We propose a novel structure of complex-tap microwave photonic filter (MPF) employing an incoherent broadband optical source (BOS) and a programmable optical spectrum processor. By tailoring the optical spectral amplitude and phase, arbitrary complex continuous-time impulse responses of the MPF can be constructed. Frequency responses with a single flat-top, highly chirped, or arbitrary-shape passband are demonstrated, respectively. The passband center can also be tuned in a wide range only limited by the opto-electrical devices. To the best of our knowledge, it is the first demonstration of an incoherent-BOS-based MPF which is single-bandpass, widely tunable, and highly reconfigurable with complex taps.

Architecture of high-order all-fiber birefringent filters by the use of the Sagnac interferometer

Several high-order all-fiber birefringent filters were built by using of Sagnac interferometer. These filters included the narrow bandpass filter, the narrow bandstop filter, the rectangular filter, and the triangular filter. All these filters can be changed into each other by adjusting only the wave plates inside the Sagnac loop. The corresponding architecture theory for these kinds of filters is proposed and verified in experiments.

Analysis and Compensation of Third-Order Dispersion Induced RF Distortions in Highly Reconfigurable Microwave Photonic Filters

A scheme to perform high-quality-factor (Q) reconfigurable microwave photonic filtering with the optical third-order dispersion (TOD) induced radiofrequency (RF) distortions compensated is demonstrated. A detailed investigation of the TOD induced RF distortions is presented both theoretically and experimentally. By programming the optical spectrum in one arm of the Mach-Zehnder structure, the distortions can be completely eliminated, giving rise to ideal RF transfer function which can achieve very high Q factors. The experimentally demonstrated Q factors are 634 and 76 when the RF center is tuned to 18 GHz and the passband shape is configured to be sinc-shape and flat-top respectively, the highest values ever reported for a single-bandpass, complex-tap, and reconfigurable microwave photonic filter.

Impact of group delay ripples of chirped fiber grating on optical beamforming networks

The impact of group delay ripples of chirped fiber gratings (CFG) on the performance of optical beamforming networks (OBFN) is investigated. The paper theoretically analyzes the quantified relations among the amplitude and period of CFG, the optical angle frequency interval at the inter-element arrays and the beampointing shift. The wavelength instability of the optical source is also investigated. This instability-induced phase jitter of RF signal has been verified experimentally. The theoretical models are proposed to analyze the performance of CFG-based OBFN systems.