A full-duplex radio-over-fiber system based on dual quadrupling-frequency

We proposed and simulatedly demonstrated a novel full-duplex radio-over-fiber system using an external modulator and an optical interleaver to generate dual quadrupling-frequency optical millimeter waves for carrying two base station downstream data and wavelength reuse for uplink connection. The simulation results reveal that the power penalties for the downstream and upstream signals of both base stations are less than 0.8 dB. In this new scheme, the configuration of the both base stations is simplified further because there is no additional laser at two base stations. The frequency of local oscillator signal is reduced due to frequency quadrupling. The cost of the new system is largely reduced.     

Remote fiber sensor based on cascaded Fourier domain mode-locked laser

We propose a high-speed remote fiber Bragg grating (FBG) sensor interrogation system based on a 1.3-μm cascaded Fourier-domain mode-locked (FDML) laser. It consists of multiple FBGs connected to an optical circulator in the laser cavity. The cascaded FDML laser with these multiple FBGs is operational when the scanning frequency of the fiber Fabry-Perot tunable filter matches the fundamental frequency of the laser cavity. Each FBG provides a separate laser cavity for the FDML laser. The scanning frequencies of each laser cavity are 30.5314, 31.5393, 32.7108, and 33.8023 kHz. Using the cascaded FDML laser, we measure the performance of the long-distance static strain FBG sensor interrogation system in both the time and spectral domains. The slope coefficients of the measured relative wavelength difference and the relative time delay from the static strain are found to be 0.95 pm/μstrain and 0.15 ns/μstrain, respectively. We also demonstrate the dynamic response of the interrogation system with 80-Hz modulation strain using the cascaded FDML laser. Thus, an FBG sensor interrogation system for high-speed and high-sensitivity long-distance monitoring systems can be realized using a cascaded FDML laser.     

Rapid wavelength scanning based on acousto-optically tuned external-cavity laser diode

High-speed, wide-range wavelength scanning is demonstrated using a laser diode with an antireflection coating and an external cavity employing an acousto-optic deflector. The narrow spectral width of 0.2 nm observed in the experiment indicates the availability of a highly coherent laser beam. The scanning range of 15 nm under rapid modulation is confirmed in the prototype system. A tuning rate of more than 100 kHz is achieved without any mode hops. To the best of our knowledge, no such high-speed wavelength tuning based on an acousto-optical configuration has been demonstrated thus far.     

Colorless gigabit WDM-PON link using injection locking and electro-absorption transceiver

In this paper, a novel colorless wavelength division multiplexing-passive optical network (WDM-PON) system using injection locking and electro-absorption transceiver (EAT) is proposed and demonstrated experimentally. This system has advantages, high data transmission, small downlink signal effect to uplink signal and less polarization sensitivity, compared to the system using reflective semiconductor optical amplifier (RSOA). Downlink signal modulates the right side carrier of the double side band signal by using injection locking. EAT functions as both photo detector in downlink signal and modulator for uplink signal, simultaneously. A possible cross absorption modulation effect from the EAT is analyzed experimentally. Bidirectional transmission of 1.25 Gbps and 622 Mbps for downlink and uplink, respectively, were verified through 23 km standard single mode fiber (SSMF).     

光网络中光纤光栅构成的波长分插复用器理论及进展

本文从光网络角度详细叙述、分析了各种光纤光栅构成的波长分插复用器技术的发展及理论 ,并指出了不同种类分插复用器各自适用的范围 ,表明了光纤光栅构成的波长分插复用器在光网络中的重要性。     

RMSECV曲线筛选光谱波段算法

提出了一种利用偏最小二乘回归系数矩阵筛选光谱波段的算法。该算法利用偏最小二乘回归系数作为筛选光谱波长的依据,参考(root-mean-squares error of cross-validation,RMSECV)曲线,使初选波长数大大降低。在此基础上通过循环选择将无效信息光谱波长剔除,同时增强了所建模型的预测精确性。通过生产过程的Raman光谱数据验证,该算法比传统的利用回归系数筛选波长的算法更好地提高了模型的精确性,同时降低了模型的复杂程度,是一种高效实用的算法。     

Crystal planes and reciprocal space in Clifford geometric algebra

This paper discusses the geometry of kD crystal cells given by (k+ 1) points in a projective space ?^{n+ 1}. We show how the concepts of barycentric and fractional (crystallographic) coordinates, reciprocal vectors and dual representation are related (and geometrically interpreted) in the projective geometric algebra Cl(?^{n+ 1}) (see (Die Ausdehnungslehre von 1844 und die Geom. Anal. Teubner: Leipzig, 1894)) and in the conformal algebra Cl(?^{n+ 1, 1}). The crystallographic notions of d‐spacing, phase angle, structure factors, conditions for Bragg reflections, and the interfacial angles of crystal planes are obtained in the same context. Copyright © 2011 John Wiley & Sons, Ltd.     

一种求解虚波长路径光网络波长资源优化问题的启发式算法

本文提出了一种虚波长路径光网络的启发式路由选择算法,它可以用来解决以最小化网络所需波长数目为目标的资源优化问题.该算法应用了基于最大概率路径的选路优化策略.对一个样例网络的数值分析结果表明该算法是有效的.     

超宽带可调谐SOA四波混频波长变换器的实验研究

基于半导体光放大器(SOA)光纤环形激光器中的双泵浦四波混频效应,构成超宽带并且完全透明的波长变换器,成功实现1550nm窗口2.5Gb/s信号的可调谐波长变换,变换效率在50nm范围内保持基本平坦,同时测出了SOA增益和自发辐射(ASE)噪音功率的关系.实验结果表明,在一定限制条件下,提高泵浦功率可以提高变换信号的信噪比.     

新型波长解调技术在干涉型光纤传感器输出解调中的应用

提出了一种改进型边缘滤波波长解调技术,解决干涉型或谐振型光纤传感器输出的干涉谱波长的快速解调问题。该波长解调技术基于啁啾光栅和长周期光栅的光谱特点,以啁啾光栅作为矩形滤波器,提取传感器输出干涉谱的一个干涉峰;以长周期作为边缘滤波器,将干涉峰的波长信息转化为光强信息进行检测。该波长解调技术波长解调范围为传感器输出干涉谱的一个自由光谱范围(FSR),解调速度快,克服了当前波长解调技术中存在的测量范围与测量速度难以同时提高的问题,同时还具有系统成本低 ,体积小,能够灵活多路扩展的特点。详细介绍了解调系统的工作原理以及系统结构,并将其实际应用于一种干涉型光纤电流传感器输出干涉谱的波长解调中。通过实验证明电流传感器工作在工频及脉冲电流(脉冲宽度25 μs)情况下,该解调系统对传感器输出干涉谱具有准确、快速的解调效果。该研究对推进干涉或谐振型光纤传感器的实际工程化水平的提高具有重要意义。