Self-calibration in a fiber optic sensing system using the walk-off compensation

We firstly present a concept of a self-calibration of the classical and quantum parameters’ measurement using a fiber optic system. The measurement of the change in phase of the optimum entangled states’ visibility is performed in terms of a walk-off length, i.e. birefringence. The applied physical parameters on the sensing fiber can be simultaneously measured and the self-calibration respecting the birefringence performed. The scheme of the entangled photons generation in fiber optic is reviewed and the walk-off on the polarization entangled states presented. The potential of self-calibration and simultaneous measurement using an interferometric sensing technique and fiber grating sensor are proposed and discussed. The walk-off on the entangled states in the thermal-controlled environment is presented and discussed.     

An investigation of the entangled photon walk-off compensation generated by a fiber ring resonator

We firstly present an experimental investigation of the entangled photon states’ recovery using a fiber optic ring resonator incorporating an erbium-doped fiber amplifier (EDFA). The weak light entangled photons can be recovered in both amplitude and states after the optical pumping and polarization control parts are used in the system. A new experimental result of the investigation of thermal effects on the entangled states’ walk-off and compensations has shown that the entangled photon walk-off compensation is achieved by using a pair of polarization control devices. The relationship between thermal effects and the entangled states’ phase shift is investigated and discussed. The walk-off compensation due to temperature changes from 30 to 80 °C is achieved. This shows that the changes in phase of the entangled photons can be negligible when the compensation is employed.     

Four entangled photons generation using weak light and an all fiber optic scheme for multi-entangled photons generation

This paper proposes a simple scheme of four entangled photons generation using a pulse of weak light input into a Mach-Zehnder interferometer (MZI) incorporating a fiber optic ring resonator (FORR) without any optical pumping components included in the system. After a pair of entangled photon has been generated by a four-wave mixing of weak light pulse in the FORR [P.P. Yupapin, S. Suchat, Entangled photon generation using fiber optic Mach-Zehnder interferometer incorporating the nonlinear effect in a fiber ring resonator, Journal of Nanophotonics (JNP) 1 (2007) 013504], four and eight entangled photons can be performed. In application, the multi-entangled states can be formed using the appropriated coupling ratios into a fiber coupler. The effect of the entangled state walk-off along the optical fiber is discussed.     

Entangled photon states generation and regeneration using a nonlinear fiber ring resonator

We propose a simple system of the entangled photon states generation and regeneration using a standard diode laser, a Mach Zehnder Interferometer (MZI) and a fiber optic ring resonator (FORR). Light from the diode laser is launched into an MZI and circulated in the FOOR, without any optical pumping components included in the system. The nonlinear light pulses are generated by a Kerr nonlinear effects type, while the resonance peaks are formed by the four-wave mixing of light pulses in the FORR. The entangled photons can be performed by using the polarization control device, and then detected by the avalanche photo-detectors, where the entangled photon visibility is plotted and seen. Similarly, the entangled photon states can be easily formed by using the appropriated coupling ratios into a fiber coupler, then into a ring resonator, i.e. without an MZI. The use of the entangled photons generation based on a fiber optic scheme for quantum teleportation, quantum key distribution via optical wireless link, and the system of the entangled photon states recovery by using a fiber ring resonator incorporating an erbium-doped fiber (EDF) have been investigated and discussed. The feasibility of dense coding using multi-entangled photons generation based on the fiber optic scheme and the effect of the entangled state walk-off along the optical fiber are also discussed, respectively.     

Entangled photon generation in a nonlinear microring resonator for birefringence-based sensing applications

This paper proposes a new concept of birefringence-based sensor using the entangled photon timing walk-off compensation. The superposition of nonlinear light known as four-wave mixing is introduced by the Kerr nonlinear effects type within the ring device. The possible two entangled photon pairs are randomly generated using the polarization control unit. Results obtained have shown that the entangled state walk-off of light traveling within the ring device can be compensated. This means the changes in walk-off parameters can be relatively measured to the changes in the applied physical parameters. The potential of using such a proposed system for birefringence-based sensor applications is plausible and discussed.     

Polarized soliton pulses generation using nonlinear micro ring resonators for multi- and long distance links

We propose a new concept of quantum soliton pulses generation using a soliton pulse in the micro ring resonators. Firstly, the chaotic soliton pulses are generated and circulated within the integrated micro ring resonators. Secondly, the specific second harmonic pulses are selected by using the appropriate ring parameters. The superposition of the second harmonic pulses within the micro ring devices introduces the randomly polarized photons within the micro ring device. The entangled photon visibility of the polarized photon is seen after passing the polarization control devices and projecting on the detectors. The optimum entangled photon visibility is obtained. The advantage of such a system is that the quantum repeater unit can be redundant for long distance quantum communication link, whereas the use of the system for multi-entangled photon sources and links is also available. The system degradation via the entangled photon states timing walk-off is also discussed.     

Long-gauge length embedded fiber optic ultrasonic sensor for large-scale concrete structures

A fiber optic ultrasonic sensor based on Fizeau interferometer has been developed and demonstrated. A helium–neon laser light source with wavelength 0.6328 μm is used in our experiment. A special feature is its Fizeau configuration, which enables one to eliminate much undesirable noise by combining both the reference arm and the sensing arm within the same length of fiber. The dynamic response model of photo-elastic effect of ultrasonic wave and optical fiber is established. The fiber optic ultrasonic sensor experimental results are obtained and compared with the convenient PZT transducer.     

克服闭环光纤陀螺输出信号中死区的实验

克服死区是闭环光纤陀螺设计中需要考虑的重要问题.实验表明本文采用的方法可以方便地克服死区.这是国内报道的首例克服闭环光纤陀螺输出信号中死区的实验.     

表面粗糙度光纤传感器研究

基于光在粗糙表面的散射原理,利用时间延迟技术,设计了一种快速、非接触测量表面粗糙度的光纤传感器。与同类传感器相比,成本低,系统误差小。     

锥形光纤中光波传输特性的蒙特卡罗模拟

为了分析锥形光纤中光子流的传输特性和空间分布特性,采用了蒙特卡罗算法对其进行了模拟仿真,得到了大量光子经过锥形光纤后的光子分布图.模拟实验结果表明,通过锥形光纤的大量光子集中在探测器中心,到达探测器某一位置的光子数随着该位置到探测器中心距离的增加而减少,并且在锥形光纤锥度比一定的条件下,改变锥形光纤长度,光强度随着长度的增加而下降,但通过锥形光纤的光子分布是一样的.这些研究结果对锥形光纤的设计和实际应用提供了重要依据.     

光纤移频分布式布里渊光纤传感技术

提出了一种利用布里渊光纤环形腔移频技术实现分布式光纤布里渊传感的方法.该方法基于布里渊光时域分析法原理,将一束单纵模运转激光器输出的激光分为两束|一束光入射布里渊光纤环形腔中产生窄线宽的受激布里渊散射光作为斯托克斯光,另一束光经过低频相位调制后作为泵浦光|斯托克斯光和泵浦光分别相向入射进入传感光纤,通过测量布里渊谱得到光纤温度或应变.利用该方法可将十几GHz的微波频率转化为兆赫信号频率进行探测处理,仅需一台激光器,因此系统结构简单、成本低,还可减小激光器频率波动对测量准确度的影响.实验验证了该方法的可行性.     

光纤Fabry-Perot谐振腔的精细度对相位灵敏度的影响

分析了光纤Fabry-Perot谐振腔的工作原理及其工作点的选择问题，推导了谐振腔的光学相位灵敏度与精细度的关系，给出了理论公式及曲线，并与光纤Math-Zehnder干涉进行了对比，指出了在相位灵敏度上两者的巨大差距，证明了光纤Fabry-Perot干涉的独特优点.介绍了光纤Fabry-Perot干涉的实验系统，提出了检测及计算Fabry-Perot谐振腔有效精细度的方法，实验结果与理论仿真基本吻合.     

光纤傅里叶变换光谱分析装置

报道了一种新的光谱测量方法-基于单模光纤Mach-Zehnder干涉仪(FMZI)结构的傅里叶变换光谱分析法。在传统傅里叶变换光谱仪( FTS ) 中,用光纤代替传统光路;用光纤耦合器取代传统分束器;用压电光程调制器取代传统移动镜;从而构建了光纤傅里叶变换光谱仪(FFTS)。利用该FFTS测量了LD在阈值以下的发射光谱并与光栅光谱仪测量结果进行了比较,结果表明测量结果是相互吻合的。初步的实验中由于光程调制有限,光谱分辨率为～7 cm-1,改造光程调制器可进一步提高光谱分辨率,证明了FFTS用于分析光谱的可行性。     

Spatial domain multiplexing: A new dimension in fiber optic multiplexing

A novel multiplexing technique for fiber optic communications has been developed that supports multiple channels of optical energy inside an optical fiber by confining each individual channel to a unique spatial location. These channels can operate at exactly the same wavelength as well as differing wavelengths. The basic operating principle and experimental results for spatial domain multiplexed fiber optic communication systems is presented here. This technique adds a new dimension to currently available multiplexing schemes and has the potential to increase the bandwidth of existing and futuristic optical fiber systems by multiple folds.     

谐振腔光纤陀螺光纤谐振环特性研究

对有限光源线宽情况下反射式光纤谐振环的响应特性进行了研究,得到了光纤谐振环各谐振特性参量的表示式.分析了特性参量与光源线宽和耦合器特性的关系,结合对方波调制谐振腔光纤陀螺极限灵敏度的分析,给出了设计高灵敏度谐振腔光纤陀螺光纤谐振环的要求和原则.进行了谐振腔光纤陀螺用光纤谐振环的实验研究,制作了适用于谐振腔光纤陀螺的高精细度和高谐振深度光纤谐振环.     

Pulse polarization entangled-photon generated by chaotic signals in a nonlinear micro-ring resonator for birefringence-based sensing applications

We propose a new concept of birefringence-based sensing using entangled-photon timing-walk-off compensation. Four-wave mixing within a micro-ring resonator is employed, which is introduced by the nonlinear Kerr effect. The two possible entangled photon pairs are randomly formed by using an external polarization control unit. Results obtained have shown that the entangled-photon walk-off state within the ring device can be compensated. This means that the changes in walk-off-state parameters can be measured in response to changes in the applied physical parameters. The experimentally determined relationship between temperature and the entangled-photon walk-off parameter is seen to be in good agreement with the theoretical predictions. The potential of using the proposed system for the development of birefringence-based sensing systems is discussed.     

Quantum key distribution via fiber optic, fidelity and error corrections

We propose an interesting scheme on photon states generation using a fiber optic Mach Zehnder interferometer incorporating a fiber optic ring resonator without any optical pumping parts including in the system, which is available for long-distance link. In principle, the state of a quantum bit, it is known, unknown, or entangled to other systems. The desired quantum states are generated and transmitted in the link via a fiber optic. The transmission quality in terms of quantum fidelity is analyzed, where a high fidelity to the noiseless quantum channel is achieved by adding an ancillary photon after the signal photon within the correlation time of the fiber noise and by performing the quantum parity checking method. The error correction is also analyzed. For simplicity, feature and robustness against path-length mismatches among the nodes make our scheme suitable for multi-user quantum communication networks.     

闭环光纤陀螺全数字式信号检测方法研究

研制成功基于阶梯波调制技术的闭环光纤陀螺全数字式信号检测系统.提出了闭环光纤陀螺几个重要参数的测试方法,并给出了实验结果.     

LOW COHERENCE PULSED DOPPLER LIDAR WITH AMPLIFIED REFERENCE BEAM STORAGE

In this paper, we have successfully developed a new low coherence pulsed Doppler lidar concept for wind speed measurements, in which a pulsed laser is used as the source for measurement and reference beam. A fraction of the transmitted pulse is stored in a fiber optic ring resonator with a path length longer than the pulse. The output of the resonator is a pulse train that is used as the reference beam and can be mixed with the Doppler shifted measurement signal. Because this reference has traveled a distance equivalent to the measurement beam’s path length, low coherence sources can be used. Inserting an erbium-doped fiber amplifier into the resonator ensures that the stored pulses do not decay in amplitude. Careful control of gain and amplified spontaneous emission is required to prevent laser oscillation while maintaining sufficient gain for the signal. Experiments prove that 16 reference pulses of sufficient amplitude and stability can be generated. Computer simulations suggest that 70 pulses should be achievable, which would be equivalent to a Doppler lidar measurement range of 2,550 m.     

一种测量高温中间包的蓝宝石光纤温度计

介绍了一种测量高温的蓝宝石光纤温度计.蓝宝石单晶光纤由于其极好的高温物理化学性能,适用于高温下光纤测温应用,可用作辐射型光纤温度传感器.蓝宝石光纤温度计采用激光加热小基座法生长出端部掺Cr3+的蓝宝石光纤荧光温度传感头.用激光加热小基座,把对荧光有温度反应的材料如红宝石晶体光纤生长在蓝宝石光纤上,制成具有结构紧凑,耐高温,功能稳定的传感探头.通过荧光寿命的检测,可以测量所对应的温度.根据表面温度,可以依据温度场得到内部温度,用于测量连铸炉中的中间包钢水温度,并给出了温度计的实验系统以及原始实验数据.实验数据表明,此结果精度高,可实现非接触测量.