相位凝固技术中干涉信号调制解调误差分析

为了进一步减小基于相位凝固技术的激光反馈干涉系统测量运动物体微位移时的测量误差,采用MATLAB数值仿真及曲线拟合的方法,对移相间隔和外腔反射面振动幅度引起的系统误差进行了理论分析。在系统实验中依据相位凝固原理对物体运动产生的干涉信号进行采样,获取多组光功率曲线,在光功率曲线上实时判向并标记特征点。根据特征点重构被测物体的微位移曲线,对重构得到的微位移台阶曲线进行多项式拟合以提高测量精度。结果表明,在固定移相间隔为/5、激光器波长为1550nm的情况下,测量分辨率优于/20(77.5nm),实际测量的绝对误差最大值为47.98nm,峰峰值误差平均值小于1nm。相位凝固技术调制解调干涉信号为微位移的方向辨识和高精度测量提供了新的解决方案。     

马赫-曾德尔外差干涉椭偏仪非线性误差分析

马赫-曾德尔外差干涉椭偏仪是一种重要的光偏振态实时测量技术。为了提高测量系统的精度、降低误差,采用外差干涉光路分析和数值模拟的方法,理论推导了透射式马赫-曾德尔外差干涉椭偏仪光路的误差公式。结果表明,光源偏振的椭圆化程度,偏振分光棱镜消偏比及倾斜都能引起测量误差;同误差参量下待测光束不同的椭偏比和s,p分量相位差得到的测量误差不同;马赫-曾德尔外差干涉仪的误差结果与迈克尔逊外差干涉仪相近。     

会聚偏振光干涉法测量波片相位延迟量

提出了会聚偏振光干涉法测量波片相位延迟量的新方法.会聚线偏振光透过待测波片时,不同的入射角对应着不同的相位延迟量,在接收屏上将形成强弱分布的干涉条纹.理论推导了偏振光干涉形成的干涉条纹到条纹中心的距离,与待测波片相位延迟量之间的关系式;利用MATLAB编程进行仿真计算,证实了会聚偏振光干涉法测量波片相位延迟量的理论计算是正确的,若干涉条纹到条纹中心的距离测量误差为0.01mm,则仿真计算的相位延迟量误差小于0.2920°;实验验证了该测量方法是可行的.     

用双频相位调制的干涉仪

本文在理论和实验上研究了适合于测量位移和监督波前的双频相位调制干涉法。对由颗粒噪声、压电陶瓷的滞后作用、已调波及其振幅偏离值之间的相位移动决定的误差进行了分析，表明在实际条件下可得到2π／180的相位测量误差。     

减小正弦相位调制菲佐干涉仪多光束干涉影响的方法

在利用正弦相位调制菲佐干涉仪进行测量时,由于菲佐板及待测物体表面对入射光的多次反射而产生多光束干涉,干涉信号的强度随相位变化不是严格的余弦分布.按照双光束干涉的算法进行相位信息提取,会引入一定的误差.以正弦相位凋制菲佐干涉仪纳米精度微小位移测量为应用背景,分析多光束干涉情况下该干涉仪信号解调算法的误差,进而对干涉仪的相关参数进行优化,并通过误差补偿对测量结果进行修正,有效减小了多光束干涉产生的影响.     

低相干光干涉法测量光子晶体光纤延时

对相位敏感型低相干光干涉(OLCR)法延时测量系统进行了理论分析,建立了相关数学模型,搭建了基于非平衡迈克尔逊干涉仪的OLCR测量装置,以掺铒光纤放大器(EDFA)自发宽谱光作光源,对光子晶体光纤(PCF)延时(1540～1560nm)进行测量,取得0.14ps左右的测量精度。利用该系统测量光学元件参数,多采用元件末端面反射光与参考光干涉,但对光纤等器件的延时参数进行测量时,利用透射光会更加方便。     

基于激光干涉式水听器的近海海洋环境噪声测量研究

在迈克尔逊干涉原理的基础上设计了激光干涉式水听器,通过跟踪补偿的方式提高了水听器的抗干扰能力。通过对水听器声压误差进行分析,认为振动膜是声压误差的主要来源,且可以通过振动膜材料的选择得到一定程度上的消除。在某近海海域获得的实测数据表明,水听器对噪声声压的测量精度较高,具有良好的频率响应能力,与理论模型的对比实验也一定程度上验证了数据的准确性。在近海海域,风成噪声和船只辐射噪声是海洋环境噪声测量的主要噪声源。在此,对3种风速下测得的海洋环境噪声谱级进行了计算,并与Knudsen曲线进行了比对,结果显示,测量数据与Kundsen曲线拟合度较好,经测量,船只辐射噪声主要集中在350~500Hz频率范围内。     

波片相位延迟的精确测量及影响因素分析

提出一种精确测量波片相位延迟的方法。将待测波片置于起偏器和检偏器之间,转动待测波片和检偏器至不同的位置并探测输出的光强,得到波片的相位延迟。采用光源调制技术和解调技术,抑制了连续光所无法克服的背景光干扰和电子噪声的干扰;将光路分为测量光路和参考光路,采用软件除法技术,消除了光源波动的影响,从而实现波片相位延迟的精确测量。详细分析了影响测量精度的误差因素,主要有光源波长变化、温度变化、入射角倾斜、转台转角误差和光源波动,计算了1064 nm波长时厚度为0.52 mm的λ/4多级结晶石英波片产生的相位延迟误差,其中光源波动的影响在作除法后有显著的改善,各误差因素的总测量误差为±1.58°。实际测量了该λ/4结晶石英波片的相位延迟为91.06°±1.78°,与理论分析相符。该测量和误差分析方法同样适合其他的波片。     

信道互耦和不平衡度对综合孔径微波辐射计复相关干涉测量的影响分析及其校准

本文分析了信道互耦和不平衡度对干涉式综合孔径微波辐射计复相关干涉测量的影响.分析表明干涉测量误差的主要来源是信道的相位不平衡度.实现信道中心频率的相位精度就可以保证干涉相位的精度,而通道内的残余相位差只会引起干涉相关度的降低.通过相干/不相干噪声校准,就可以对信道不平衡引起的干涉相关测量误差进行修正.     

基于相干包络解调的窄线宽测量算法研究

激光线宽对光学相干探测系统的探测范围、精度和噪声特性都有重要影响。为精确测量半导体激光器的线宽值,提出了通过解调短延时自外差的干涉谱来实现高精度窄激光线宽测量的新方法。搭建短延时的自外差干涉测量系统,得到半导体激光器的干涉谱,通过设计算法对干涉谱的相干包络进行解调,最终获得了严格的洛伦兹线型谱和相应的谱线宽度,通过理论分析、仿真和实验验证了该方法的可行性。该方法可以忽略因1/f频率噪声产生高斯展宽带来的影响,与传统线宽测量方法相比,该方法的测量结果更加精确。     

Optically Controlled Low-Distortion Delay of GHz-Wide Radio-Frequency Signals Using Slow Light in Fibers

Continuously tunable delay of broadband analog signals for microwave photonics applications is described and demonstrated, based on stimulated Brillouin scattering (SBS) in optical fibers. The optical spectrum of the pump laser is synthesized using chirp control, in order to obtain a broadened SBS "slow light" process, with long delay and low amplitude and phase distortions. The resulting SBS process is applied to delay 1-GHz-wide linear frequency modulated radio-frequency signals of arbitrary carrier frequency. Delays up to 230 ps are observed, with a worst-case sidelobe suppression ratio of -26 dB     

Generation and coherent characteristics analysis of laser phase modulation spectrum by cascaded phase modulators

Laser phase modulation spectrum with 25 frequency bands is generated by modulating a single frequency laser with two cascaded phase modulators (PMs) with driving voltage amplitudes at 3.2 V and 7.8 V, respectively. And the time delay self-heterodyne method is adopted to measure and analyze the coherent characteristics of the original single frequency laser light and the generated multi-frequency light from two phase modulation schemes. By comparison of laser linewidth, the experimental results show that the laser phase modulation does not change the coherent characteristics of each frequency band, and the laser phase modulation spectra benefit the performance optimization for the Rayleigh scattering based optical fiber sensing system.     

基于边缘滤波的FBG解调系统

实现了一种基于边缘滤波的FBG解调系统,系统采用宽带光源、隔离器、分束器、FBG、耦合器及边缘滤波器等光学元件,来采集变化的光信号,同时设计光电探测器进行光电信号转换及放大滤波处理,并采用NI USB-6361进行数据采集,将模拟信号转换为数字信号,最后采用Labview进行处理,最终得出所要测量值。     

Spectral Oscillation in Optical Frequency-Resolved Quantum-Beat Spectroscopy With a Few-Cycle Pulse Laser

Impulsive stimulated resonant Raman scattering was induced by a 5.7 fs visible pulse from a non-collinear optical parametric amplifier. The pulse duration corresponded to 2.8 cycles of the central wavelength of the laser spectrum at 610 nm. The induced spectral change was time-resolved with a 0.8 fs delay time step and the effective absorbance change $ Delta A(lambda,t) $ was calculated from the normalized transmittance change $ {{Delta T(lambda,t)}/T} $. The observed optical and vibrational 2-D spectrum was analyzed to separate the electronic and vibrational contributions to the transient difference absorption spectrum. The probe wavelength dependence of the vibrational amplitude was explained in terms of the coupling between the laser field, Stokes field, and the vibrational coordinates. Simultaneous measurement of both the time and wavelength dependence of the vibrational amplitudes clearly showed that the broadband spectra of the components corresponding to the laser and Stokes lights are oscillating in $ pi $ out of phase with the corresponding vibrational frequency. The probe delay time and probe wavelength dependence of the oscillation in the absorbance change induced by the femtosecond laser were fully analyzed. The results were explained by the imaginary and real part of the third-order susceptibility, respectively.      

Group delay and α-parameter measurement of 1.3 μmsemiconductor traveling-wave optical amplifier using the interferometricmethod

The group delay dispersion and the linewidth broadening factor (α-parameter) are measured for a 1.3-μm semiconductor traveling-wave optical amplifier (TWA) using a newly developed interferometric method. By Fourier transforming an interferometric cross-correlation signal, both the optical phase and the gain are simultaneously obtained in the entire gain bandwidth. The group delay spectrum is evaluated from the frequency derivative of the phase, and by selecting an appropriate interval for the interferometer scan, a refractive index dispersion of ~ 3.2 fs/nm is separated from the dispersion caused by Fabry-Perot resonance. From the phase and gain change with injection current, the α-parameter spectrum is evaluated, and the results indicate a strong dependence on wavelength     

High-sensitivity detection of narrowband light in a more intense broadband background using coherence interferogram phase

This paper describes an optical interferometric detection technique, known as the interferogram phase step shift, which detects narrowband, coherent, and partially coherent light in more intense broadband incoherent background light using changes in the phase gradient with the optical path difference of the coherence interferogram to distinguish the bandwidth or coherence of the signal from that of the background. The detection sensitivity is assessed experimentally by measuring the smallest signal-to-background ratio or signal-to-clutter ratio (SCR), which causes a detectable change in the self-coherence interferogram phase. This minimum detectable SCR (MDSCR) is measured for the multimode He-Ne laser, resonant-cavity light-emitting diode (LED), narrowband-filtered white light, and LED signal sources in a more intense tungsten-halogen-lamp white-light background. The highest MDSCRs to date, to the authors' knowledge, are -46.42 dB for coherent light and -31.96 dB for partially coherent light, which exceed those of existing automatic single-domain techniques by 18.97 and 4.51 dB with system input dynamic ranges of 19.24 and 11.39 dB, respectively. The sensitivity dependence on the signal-to-system bandwidth ratio and on the relative offset of their central wavelengths is also assessed, and optimum values are identified.     

Microwave photonic bandpass filter based on spectrumslicing and phase modulator

A tunable microwave photonic bandpass filter with high mainlobe-to-sidelobe ratio (MSR) based on a phase modulator and a dispersive device is proposed. The multi-tap characteristics of the filter are realized by slicing a broadband source using a Mach-Zehnder interferometer (MZI) which results in a high MSR of 25 dB. The tunability of the filter is realized by an optical variable delay line (OVDL) in one arm of the MZI, which changes the wavelength spacing of the sliced broadband source and results in a tunable free spectrum range (FSR) of the filter. The central frequency of the bandpass filter is tunable from 10.7 GHz to 27 GHz by changing the wavelength spacing from 0.145 nm to 0.054 nm.     

Optical bistability in semiconductor lasers under intermodal lightinjection

Optical bistability in semiconductor lasers under intermodal light injection is predicted using small-signal analysis. The optical bistability is a special case of sidemode injection locking and originates from the strong gain nonlinearity introduced by external light injection. The theory can be applied to the optical bistability under both intramodal and intermodal light injection. And the difference of the optical bistabilities between intermodal and intramodal light injection is discussed. Expression for the bistable loop width is presented. Optical frequency-bistability and power-bistability in semiconductor lasers can be realized by intermodal light injection, which imply that a small (a few GHz) change of the injected light frequency or a small (several μW) change of the injected light power will induce a large (up to THz) change of the laser emitting frequency. Besides, hybrid optical bistability can be achieved by varying the bias current (only a few mA) of the laser. Dynamic properties, such as turn-on and turn-off delay and carrier overshoot during switching are discussed and some consideration of the practical aspects of the optical switching is presented     

谐振式光纤陀螺调相谱检测技术中的光克尔效应

谐振式光纤陀螺(R-FOG)是基于Sagnac效应产生的谐振频率差来测量旋转角速率的一种新型光学传感器。信号检测技术和系统中存在的各种噪声对系统的检测精度有着重要的影响。基于调相谱检测技术的谐振式光纤陀螺系统中,除顺时针(CW)和逆时针(CCW)光路传播的光强不均匀会引入非互易相位差,使系统出现零漂外,顺时针和逆时针光路的调制系数也会引入系统零漂。光克尔效应引入的系统零漂与系统的真实旋转在测量时是无法区分的,因此成为主要的噪声之一。通过光波场叠加原理,推导得到调相谱检测方案下的谐振式光纤陀螺系统中,光克尔效应引起的系统零漂的解析表达式。依据光克尔效应产生的零漂不随陀螺转速的改变而变化,利用简单的开环系统,对光克尔效应引入的陀螺零漂进行了测试。