基于级联光纤环微波光子滤波器的微波倍频技术

为了得到高倍频的微波信号,实现获得了一种基于外调制技术与级联光纤环微波光子滤波器(FRMPF,fiber ring microwave photonic filters)的新型倍频微波信号光学产生技术。利用外调制的方法,采用大功率信号驱动马赫曾德尔调制器(MZM)得到了高阶谐波信号,再利用级联的FRMPF进行选频。理论计算与实验测试了FRMPF的滤波特性。通过调节每个FRMPF的环长,利用第1个FRMPF将基频信号与三阶谐波滤除,再通过第2个FRMPF将二阶谐波滤除,最终得到四倍频信号。研究结果表明,利用频率为2.018 3GHz的信号驱动MZM,得到了频率为8.073 2GHz的四倍频信号,信噪比(SNR)大于13dB。国家自然基金青年科学基金(61205059);教育部博士点基金(20120121120037);中央高校基本科研业务费(2010121059)资助项

Radio-over-Fiber System With Multiple-Optical-Source-Based Microwave Photonic Filter Performing as a Subcarrier Demultiplexer

National 863 Project [2008AA01Z221]A simple and cost-effective demultiplexing approach for a subcarrier multiplexed radio-over-fiber (RoF) system is proposed, analyzed, and experimentally demonstrated. A microwave photonic filter based on multiple optical sources is integrated into the RoF system, and by simply controlling the time delay in the remote antenna unit, the subcarrier with desirable frequency can be filtered out, and undesirable ones are suppressed. An experimental demonstration has been carried out by implementing a two-optical-source-based microwave photonic filter in an RoF downlink transmitting a 2.5-GHz subcarrier modulated with 150-Mb/s on-off keying (OOK) data, showing that it works well as a subcarrier demultiplexer. The proposed demultiplexing approach enjoys high flexibility, tunability, and cost-effectiveness and has good potential applications in the multiplexed RoF systems

Remote Wideband Microwave Frequency Measurement Based on a Single-Passband Microwave Photonic Filter

A new method for remote wideband microwave frequency measurement utilizing a single-passband microwave photonic filter is proposed, theoretically analyzed, and experimentally demonstrated. The frequencies of the input microwave signals can be measured by monitoring the maximum output microwave power while scanning the central frequency of the single-passband microwave photonic filter. The parameters of the filter have also been analyzed to optimize the frequency measurement performance. The proposed frequency measurement technique is easy to implement, capable of measuring frequencies of multiple microwave signals.Fundamental Research Funds for the Central Universities of Xiamen University [2010121059

Effects of grating characteristics to the performance of fiber-Bragg-grating delay line based microwave photonic filters

Fundamental Research Funds for the Central Universities [2010121059]In this paper, both theoretical investigation and experimental verification of microwave photonic filter based on a fiber-Bragg-grating (FBG) delay line and a broadband light source have been carried out, in which the effects of spectrum and dispersion characteristics of the FBGs on the frequency response of the microwave photonic filter have been taken into consideration. Theoretical and experimental results agree well, and both results show that FBG's characteristics affect not only the free spectrum range (FSR) of microwave photonic filter's response, but also results in the frequency dependent power degrading. (C) 2012 Elsevier B.V. All rights reserved

All-Optical Approach to Microwave Frequency Measurement With Large Spectral Range and High Accuracy

An all-optical approach for microwave frequency (MWF) measurement with a low-speed oscilloscope is proposed and experimentally demonstrated. In this scheme, an optical filter with a single and ultranarrow passband, together with a tunable laser and a low-speed photodiode is utilized to calculate the MWF by measuring the time delay between the sweeping optical carrier and its upper/lower sideband passing through the filter. Single-frequency and multifrequency measurements are experimentally demonstrated. The measurement recognition, accuracy, and resolution are below 0.1, 0.09, and 0.2 GHz, respectively. This proposed scheme can be easily upgraded to higher frequencies using a modulator with higher bandwidth proportional to the desired measurement range.National High Technology Research and Development Program 863 of China [208AA01Z221]; Fundamental Research Funds for the Central Universities [2010121059

An All-Optical Transformer From Differential NRZ Data to Ultra-Wideband Pulse Stream

National High Technology Research and Development Program (863) of China [208AA01Z221]We propose and experimentally demonstrate a compact and cost-effective scheme based on a fiber Sagnac structure to realize real time conversion from differential nonreturn-to-zero (NRZ) data to ultra-wideband (UWB) pulse stream. The proposed conversion system for the UWB signal generation consists of a single-wavelength laser, a phase modulator, several polarization controllers, and optical couplers. Due to the optical interference between the two phase-modulated light waves with slight phase difference in the Sagnac loop, two sharp optical pulses with opposite polarities are obtained. With proper time delay, a UWB monocycle pulse stream is generated from the original differential NRZ data. Our proposed method gives a reliable, easy, and low-cost transformer from differential NRZ signal to UWB pulse stream, and no high-speed arbitrary waveform generator (AWG) is required in this all-optical transformer

Liquid level sensor based on an excessively tilted fibre grating

We propose and demonstrate an optical liquid level sensor based on the surrounding medium refractive index (SRI) sensing using an excessively tilted fibre grating (ETFG). When the ETFG submerged in water, two sets of cladding modes are coupled, corresponding to air- and water-surrounded grating structures, respectively. The coupling strengths of the two sets of cladding modes evolve with the submerging length of the grating, providing a mechanism to measure the liquid level. Comparing with long-period fibre grating based liquid level sensor, the ETFG sensor has a much higher SRI responsivity for liquids with refractive index around 1.33 and a lower thermal cross sensitivity. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved

Transversal-load sensor by using local pressure on a chirped fiber bragg grating

A transversal-load sensor based on the local pressure-induced refractive index change in a chirped fiber Bragg grating (CFBG) is proposed. The local pressure induced refractive index change in the touch point can generate a main transmission peak and several subpeaks on the long wavelength side of the reflection band of the CFBG. The difference of the wavelength shifts for the main transmission peak and the first subpeak is used to measure transversal-load with temperature compensation capability

Design of an FBG Sensor Network Based on Pareto Multi-Objective Optimization

A novel scheme based on Pareto-based multi-objective optimization technology is proposed to design a wavelength-division-multiplexing (WDM) fiber Bragg grating (FBG) sensor network. Considering multiple objectives, which are minimizing the bandwidth of the optical source and minimizing the overlapping spectra, an elitist non-dominated sorting genetic algorithm is applied for obtaining the Pareto front. Simulation results show that our approach is effective in improving the multiplexing capability of the WDM network

Implementation and characterization of liquid-level sensor based on a long-period fiber grating Mach-Zehnder interferometer

An optical liquid-level sensor (LLS) based on a long-period fiber grating (LPG) interferometer is proposed and experimentally demonstrated. Two identical 3-dB LPGs are fabricated to form an in-fiber Mach-Zehnder interferometer, and the fiber portion between two LPGs is exposed to the liquid as the sensing element. The sensitivity and measurement range of the sensors employing different orders of cladding modes are investigated both theoretically and experimentally. The experimental results show good linearity and large measurement range. One of the significant advantages of such a sensing structure is that the measurement level is not limited to the length of the LPG itself. Also, the measurement range and sensitivity of the proposed LLS can be readily tailored for a particular applications