常用合成食品色素荧光光谱研究

分析合成食品色素的分子结构特点,根据荧光与分子结构的关系,理论上推断合成食品色素是荧光物质。应用SP-2558多功能光谱测量系统,测得胭脂红、苋菜红、柠檬黄、日落黄、亮蓝等五种最常用的合成食品色素标准溶液的三维荧光光谱。结果表明,胭脂红在波长330～430 nm的光激发下,产生较强荧光,荧光峰值波长为621 nm,最佳激发波长为376 nm;苋菜红在波长300～440 nm的光激发下,产生较强荧光,荧光峰值波长为643 nm,最佳激发波长为370 nm;柠檬黄在波长280～380 nm的光激发下,产生很强荧光,荧光峰值波长为565 nm,最佳激发波长为315 nm;日落黄在波长310～410 nm的光激发下,产生较强荧光,荧光峰值波长为592 nm,最佳激发波长为348 nm;亮蓝在波长320～390 nm的光激发下,产生较强荧光,荧光峰值波长为456 nm,最佳激发波长为350 nm。进而对这五种合成食品色素的荧光光谱进行了分析讨论。结果可为食品色素检测和食品安全提供帮助。     

分布式光纤Bragg光栅波长校准方法

提出了一种利用标准参考光谱进行波长校准的方法。实验中利用由宽带光源和光纤可调谐滤波器组成的可调谐光源分别扫描了参考光谱和传感光栅的光谱。在参考通道,ITU标准参考模块的输出是具有固定波长的梳状光谱。利用高斯拟合算法计算出由标准参考透射谱峰值输出的对应的驱动电压,通过样条插值函数获得了滤波器输出波长与驱动电压的关系。计算光栅反射谱峰值对应的驱动电压,利用上面获得的滤波器输出波长与驱动电压的关系式可以计算出传感光栅的Bragg波长。实验结果表明,在较大的波长范围内实现了对多个传感光栅的波长校准,减小了由滤波器非线性输出造成的测量误差,具有较高的重复性。     

Czerny-Turner型双光栅单色仪的波长驱动与波长校准研究

单色仪在实际光谱测量前需要进行波长校准。文中分析了波长驱动原理,并推导了Czerny-Turner双光栅单色仪出射波长与步进电机脉冲数的关系式。在此基础上进行了波长校准实验。使用低压汞灯作为校准光源,在紫外波段和可见波段蓝端,扫描多条低压汞灯特征谱线,得到单色仪的指示波长与信号强度的关系数据。计算出单色仪出射这些谱线时使用的波长修正量。最后使用曲线拟合方法得到250 nm～450 nm光谱范围内单色仪出射任意波长时对应修正量的计算式。波长校准保证了单色仪的波长准确性。     

共振波长对导模共振生物传感器灵敏度的影响

导模共振生物传感器由于具有微型化、免标签、高通量和实时检测等优势被广泛研究。利用严格耦合波理论分析了该生物传感器对样品折射率和厚度的灵敏度随共振波长的变化规律。当样品厚度和共振波长一定时,其折射率灵敏度恒定;随着共振波长的增大,折射率灵敏度显著提高。当样品折射率和共振波长一定时,厚度灵敏度随着厚度的增加而降低,最后趋近于0;当共振波长增加时,厚度灵敏度明显提高,厚度测量范围增大。结果表明:选取较长的共振波长有利于样品的检测和分析。     

用于光纤光栅解调的波长敏感光纤耦合器

为了拓宽光纤耦合器的使用范围,开发光纤耦合器的新功能,采用熔锥技术制作波长敏感耦合器,该耦合器在分光的同时对波长敏感。通过耦合理论验证实验结果,实验数据与理论值相符合。实验中得到波长灵敏度最大值为17.86%/nm的耦合器。采用拉锥工艺制作波长敏感耦合器工艺简单,耦合比峰值对应波长控制易于实现。该耦合器可用于光纤光栅布拉格波长漂移解调。令待解调光纤光栅布拉格波长与耦合器波长灵敏度最大值对应的波长一致,当波长发生漂移时,耦合器输出耦合比发生变化。自制的波长敏感耦合器实现了对布拉格波长为1566.71 nm光纤光栅波长漂移的解调,波长漂移1.80 nm,耦合比变化20.34%。此种解调方式具有光路简单,易于与光纤匹配的优点,可以应用在大型建筑中光纤光栅的健康监测。     

Broadband gain-clamped linear quantum dash optical amplifiers

The linear optical gain of gain-clamped quantum dash semiconductor optical amplifiers (GCSOAs) has been investigated using the rate equation model. The gain spectrum of GCSOA for different wavelength detuning and different doping has been studied. Our analysis shows that the linear gain can be increased as the laser wavelength is detuned to high wavelength where the peak of the optical gain, which is found at wavelengths below the ground state wavelength, is shifted to lower wavelength as the laser wavelength is increased. We find that doping the dashes by either N-type or P-type enhances the linear optical gain and shifts the gain peak to lower wavelength. Moreover, we found that GCSOA with lightly N-type doping demonstrates large separation between the laser and the amplifier wavelength. Also we find that small inhomogeneous line broadening enhances the linear gain peak, shifts the gain peak to wavelength lower than the GS wavelength and widens the gain spectrum.     

A reconfigurable multiwavelength fiber laser with switchable wavelength channels and tunable wavelength spacing

We report the experimental demonstration of a reconfigurable multiwavelength fiber laser source with switchable wavelength channels and tunable wavelength spacing by spectrum slicing a broadband light source using a tunable comb filter. The tunable comb filter is based on a thermally-induced linearly-chirped fiber Bragg grating (LCFBG). As an example to demonstrate the effectiveness of the method, two wavelength channels with various wavelength spacings and eight wavelength channels with ∼1.6 nm wavelength spacing were experimentally demonstrated. All the wavelength channels have rejection ratios of greater than 20 dB, and very small 3-dB linewidths of ∼10 pm. The multiwavelength optical source has such unique advantages as simple all-fiber structure, switchable wavelength channels, tunable wavelength spacing, very narrow linewidths, and stable room-temperature operation.     

基于光纤中SRS效应的全光波长转换

提出利用光纤中非线性效应受激喇曼散射（stimulated Raman scattering, SRS）实现波长转换的原理方案和相应的理论分析模型,并进行实验验证,将经过放大后的信号光和连续探测光同时注入光纤,在光纤中进行SRS放大,实现信号之间的转换。结果表明:利用SRS可实现波长转换,可实现跨几个THz的波长之间的转换。得到最大转换效率和消光比分别为-17.3 dB和15.7 dB。通过改变探测光的波长,可实现相隔几个THz光信号的全光波长转换和可调谐波长转换。     

膜厚监控系统的光谱宽度对窄带滤光片性能的影响

讨论了膜厚监控系统的光谱宽度对波分复用窄带滤光片特性的影响,分析了监控过程中所出现的信号异常现象,其主要原因是控制光光谱宽度以及控制波长与滤光片中心波长不一致,所以控制光光谱分辨率必须小于单个法布里-珀罗滤光片最后2层膜折转点波长宽度的一半,即对100GHz的滤光片,监控系统的光谱宽度必须小于0．2nm。一旦产生中心波长偏离,就必定产生厚度控制误差。讨论了高折射率膜和低折射率膜的信号变化规律,发现当中心波长比监控波长长时,虽然信号变化规律正确,但判读到极值时的膜厚变薄。中心波长偏离越长,厚度将越薄。而当中心波长比监控波长短时,信号将出现反转。中心波长越短,反转量越大。最后指出了监控误差对滤光片Tmax和半峰全宽的影响。     

基于指示克立格法的最佳激发波长和最佳发射波长的确定

激发波长和发射波长是分子荧光光谱测量的重要参数,它的选择影响分子荧光光谱的测量以及其后续研究的精确度。由于如HITACHI F-4500 荧光分光光度计等一些光谱仪器的测量精度达不到一些光谱分析技术的要求以及测量数据的有限,在实际工作中,利用已测量的光谱数据,通过插值生成所需要的光谱数据,就成为一种有效的解决方法。因此,文章使用指示克立格法对一定体积分数的乙醇溶液的最佳激发波长和最佳发射波长的确定进行了研究。基于指示克立格法求取的最佳激发波长和最佳发射波长分别是226.9和337.1 nm,经验证其值是准确的。此外,文章采用相对标准偏差对插值结果进行了评价。结果表明在分子荧光光谱测量中基于指示克立格法确定最佳激发波长和最佳发射波长是可行的,这为最佳激发波长和最佳发射波长的确定提供了一种新的方法。     

光纤零色散波长的精确测量

提出了一种测量单模光纤零色散波长的新方法,即让可调谐的连续波（波长λｓ）和波长λｐ位于光纤正常色散区的泵浦脉冲串在光纤中共同传输,交叉相位调制与群速度色散的相互作用可使得连续波的强度得到调制。对连续波λｓ进行调谐,若连续波被调制成亮脉冲,则表明λｓ位于光纤负色散区;若连续波被调制成暗脉冲,则表明λｓ位于光纤正色散区;若连续波的强度不能被调制,则表明λｓ位于光纤的零色散波长λ０附近。利用这一方法对长度为０．９８ｋｍ的色散位移光纤的零色散波长进行了测量,测量精度可达０．５ｎｍ。     

Wavelength conversion in multihop wavelength division multiplexed transport networks

In this paper, we have analyzed the wavelength conversion for a multihop wavelength division multiplexed (WDM) transport networks to minimize the blocking probability. The analytical model is presented for a static-routing for a multihop paths wavelength conversion. The results have been validated for three cases, without wavelength conversion, with wavelength conversion and limited wavelength conversion. We show that by using wavelength conversion, there is significant improvement in performance of these transport networks. Each of the three cases of wavelength conversion is discussed for different degrees of conversions. It is observed that the higher the degree of conversion is, the lower is the blocking probability. Also as the degree of conversion is increased further, the curve for limited range conversion moves towards the no conversion.     

Experimental observation of lasering behavior in wavelength-switchable fiber laser with arrayed waveguide grating

A simple and wavelength-switchable fiber laser consisting mainly of an Erbium-doped fiber amplifier (EDFA) which provides the optical gain and an 1 × 40 (1 input channel to 40 output channels) arrayed waveguide grating (AWG) that supports wavelength selection is reported. The lasering behavior in wavelength-switchable fiber laser is investigated experimentally. One can obtain wavelength-switchable single-longitudinal-mode (SLM) single wavelength laser with different wavelength by changing different channel of the AWG as the wavelength selection element. Lasering wavelength hopping in dual wavelength laser operation for low pump power is experimentally observed. The wavelength hopping and the output power of the laser is controlled by using a variable optical attenuator (VOA). The wavelength hopping operation is eliminated for high pump power. One can obtain switchable dual wavelength laser with different wavelength by selecting different two channels of the AWG. The output laser exhibits a good performance having a high sidemode suppression ratio (SMSR), narrow line-width and symmetrical spectrum.     

探测光波长漂移对能见度测量的影响

为了研究探测光波长的漂移对能见度测量的影响。从Koschmieder经验公式的定义出发,根据实验测得400 nm~1 100 nm波段的气溶胶透过率,分析研究探测光波长漂移对能见度测量结果的影响。结果表明,能见度测量的相对误差与探测光波长和波长的漂移范围以及气溶胶消光特性有关,能见度测量的相对误差随着探测光的波长漂移范围线性增大,随着波长漂移范围的增大,各个波长的能见度测量相对误差线性增大的速率不同,对于相同的波长漂移范围,使用不同的探测光波长产生的能见度测量相对误差不同。对于某一大气环境,使用特定的波长而且中心波长稳定的光作为探测光可以明显减小由于探测光波长漂移引起的能见度测量相对误差。     

High-Speed Optical Packet Switch with an Optical Digital-to-Analog Conversion-Type Header Processor

We describe a novel type of an optical packet switch with an optical header processor based on optical signal processing and wavelength routing architecture. It consists of an optical digital-to-analog conversion-type header processor, wavelength selection portion with an electrically tunable laser, a wavelength converter based on a semiconductor optical amplifier (SOA), and wavelength routing by use of an arrayed waveguide grating (AWG), which is called a wavelength label switch (WLS). Wavelength switching of an electrically tunable laser, and wavelength conversion were successfully achieved within a few nanoseconds after recognition of an optical header using a two-bit optical header processor and a FPGA-based wavelength table. High-speed transfer performance of less than a few tens of nanoseconds and BER of less than 10^-10 were verified in the wavelength routing operation among three assigned wavelengths.     

波长漂移对近红外光谱PLSR分析模型的影响

在近红外光谱分析过程中,单台仪器在不同时间的波长变化及多台仪器间的波长一致与否会对化学计量学定标模型的校正及传递效果产生影响,上述问题可以统一为波长漂移对定标模型的影响。以分析小麦粉中粗蛋白含量为例,首先结合不同谱区光谱数据,利用偏最小二乘回归（PLSR）方法建立了两个定标模型。再由计算机生成不同类型、不同幅度的波长漂移信息,并叠加至验证集样品光谱中,使新光谱相对于定标集光谱产生波长漂移信息。通过考察原定标模型对新光谱的预测与校正情况,研究了波长漂移对PLSR定标模型的影响。结果表明：相对于定标集样品光谱,验证集光谱中无波长漂移信息时,模型的预测标准差（RMSEP）不超过0.3%,预测相关系数不小于0.98;验证集样品光谱在不同波长处的波长漂移信息为一恒定值时,模型的RMSEP会随波长漂移幅度的增大而增大,波长漂移量为-32 cm-1时对应RMSEP为3.69%,预测相关系数变化不大;当验证集样品光谱在不同波长处的波长漂移信息随机变化时,基于长波区光谱所得原始模型的预测结果几乎不受影响;当含有不同波长漂移信息的一系列样品光谱加入到定标集对长波区PLSR分析模型进行校正时,校正后模型的RMSEP为0.3%,几乎不受波长漂移信息的影响,但模型的回归因子数从3显著增大到8,其稳健性变弱;总的来说,当仪器存在波长漂移且幅度不大时,模型预测相关系数几乎不受影响,可通过对预测结果的校正来改善RMSEP,以保证分析结果的准确性。该研究为确定仪器设计参数及分析方法的操作规程,提高近红外光谱分析结果的可靠性提供了实验依据。     

基于对称广义Fibonacci光子晶体结构的电光可调谐滤波器

本文构建了含有电光材料LiNbO3的一维对称广义Fibonacci光子晶体结构,提出并设计了一种基于该结构的可调谐滤波器,并利用传输矩阵法对设计的滤波器的可调谐滤波特性进行了理论研究.数据模拟结果表明:保持对称广义Fibonacci光子晶体的几何结构不变,通过改变电极所在处施加在电光介质(LiNbO3)层上的外加电场,...     

基于双通构型的和频、差频可变波长路由方案及其应用

提出了双通构型的基于“和频”和“差频”级联二阶非线性效应的可变波长路由方案,通过调节两个抽运源的频率,可以从一个WDM(wavelength division multiplexing)链路中取出任意一个信道,然后将其转换为任意一个波长并插入到另一个WDM链路中去.实现了可调谐波长转换和光波长路由的结合.通过小信号分析,给出了相位匹配情况下,输入信号光在波导中功率变化的表达式和输出转换光功率变化的表达式,并给出了提高系统效率的对两个抽运光功率的优化方案.数值计算表明,只要信道间隔大于02nm(25GHz 关键词： 光波长路由 光波长转换 光交换 PPLN     

WDM波长路由光网络的波长分配算法

由于WDM网络中的传输和交换是以波长为粒度进行的。因此波长分配算法就成为光网络的研究热点。有效的算法可大大提高波长的利用率，并可充分挖掘WDM的带宽资源。介绍了WDM全光网络中静态和动态波长分配算法，尤其是结合大型网孔网络详述了几种动态波长分配算法。针对波长变换器在全光网络中的应用。提出了一种可以解决任意类型光网络的分层图算法，它可以一次性解决路由选择和波长分配问题，大大提高了该算法的效率。是未来光网络中非常有前景的一种波长分配算法。     

A Practical Detection System of Multiplexed Wavelength Fiber Bragg Gratings

A practical demodulation of multiplexed wavelength FBGs is proposed. The detection wavelength of adjacent FBGs and the wavelength resolution are discussed. Experimental results show the wavelength resolution is 0.01nm and strain resolution is 8.27 ×10-6 .