Experimental demonstration of single-mode fiber coupling using adaptive fiber coupler

Coupling plane wave into a single-mode fiber （SMF） with high and steady coupling efficiency is crucial for fiber- based free-space laser systems, where random angular jitters are the main influencing factors of fiber coupling. In this paper, we verified a new adaptive-optic device named adaptive fiber coupler （AFC） which could compensate angular jitters and improve the SMF coupling efficiency in some degree. Experiments of SMF coupling under the angular jitter situation using AFC have been achieved. Stochastic parallel gradient descent （SPGD） algorithm is employed as the control strategy, of which the iteration rate is 625 Hz. In closed loop, the coupling efficiency keeps above 65% when angular errors are below 80/3tad. The compensation bandwidth is 35 Hz at sine-jitter of 15 ~rad amplitude with average coupling efficiency of above 60%. Also, experiments with simulated turbulence have been studied. The average coupling efficiency increases from 31.97% in open loop to 61.33% in closed loop, and mean square error （MSE） of coupling efficiency drops from 7.43% to 1.75%.

Wavelength dependent loss of splice of single-mode fibers

After reviewing three different definitions of mode field diameter of single-mode fibers, coupled efficiency calculation methods associated with lateral offset, longitude separation and wavelength, the effects produced by them, and the influences of splicing defects were discussed in detail. The regularities of the effects were studied according to the first order derivation of couple efficiency formula, and a simplified formula for couple efficiency calculation was presented under the circumstance of slight misalignment, with respect to wavelength, 2, and in a good agreement with the theoretical model. The simplified formula provides a new but simple approach to evaluate wavelength dependent couple efficiency of single-mode fibers. Theoretical analyses and numerical calculations show that, when those defects exist, the wavelength produces additional effects on the couple loss that growth of wavelength causes an increase on the couple efficiency for the lateral offset or longitude separation whereas lessens the couple efficiency due to angular misalignment or mode fields mismatching, and that the wavelength degrades the couple efficiency distinctly when λ≥2.5 μm whereas it distorts the couple slightly in range of λ≤2λ≤2 μm.

Single-mode antiresonant terahertz fiber based on mode coupling between core and cladding

Based on the index-induced mode coupling between the higher-order mode in core and the fundamental mode in cladding tubes,the single-mode operation can be realized in any antiresonant fibers(ARFs)when satisfying that the area ratio of cladding tube and core is about 0.46:1,and this area ratio also should be modified according to the shape and the number of cladding tubes.In the ARF with nodal core boundary,the mode in core also can couple with the mode in the wall of core boundary,which can further enhance the suppression of high-order mode.Accordingly,an ARF with conjoint semi-elliptical cladding tubes realizes a loss of higher-order mode larger than 30 dB/m;simultaneously,a loss of fundamental mode loss less than 0.4 dB/m.

FAST EVALUATION OF THE CHARACTERISTICS OF SINGLE-MODE OPTICAL FIBERS

This paper describes a method for fast engineering evaluation of the transmission characteristicsof single-mode optical fibers.A versatile microcomputer program is presented which can be utilized to ana-lyze mode field characteristics of single-mode fibers with arbitrary refractive index profiles.Our computationshows that the mathematical algorithm and the corresponding programs developeod in this paper are rela-tively simple and accurate enough for the engineenring design of single-mode fibers for optical communica-tion systems.

Single-polarization single-mode hollow-core negative curvature fiber with nested U-type cladding elements

Hollow-core negative curvature fibers(HC-NCFs)have become one of the research hotspots in the field of optical fiber because of their potential applications in the data and energy transmissions.In this work,a new kind of single-polarization single-mode HC-NCF with nested U-type cladding elements is proposed.To achieve the single-polarization single-mode transmission,we use two different silica tubes in thickness,which satisfy the resonance and anti-resonance conditions on the U-type cladding elements and the cladding tubes,respectively.Besides,the elliptical elements are introduced to achieve good single-mode performance.By studying the influences of the structure parameters on the propagation characteristics,the optimized structure parameters are obtained.The simulation results show that when the wavelength is fixed at 1550 nm,the single-polarization single-mode transmission is achieved,with the polarization extinction ratio of 25749 and minimum high-order mode extinction ratio of 174.Furthermore,the confinement loss is only 0.0015 dB/m.

Frequency-stabilized Yb：fiber comb with a tapered single-mode fiber

We demonstrate a stable Yb：fiber frequency comb with supercontinuum generation by using a specially designed tapered single-mode fiber, in which a spectrum spanning from 500 nm to 1500 nm is produced. The carrier-envelope offset signal of the Yb：fiber comb is measured with a signal-to-noise ratio of more than 40 dB and a linewidth narrower than 120 kHz. The repetition rate and carrier-envelope offset signals are simultaneously phase locked to a microwave reference frequency.

A tunable comb filter using single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop

A novel tunable comb filter composed of a single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop is proposed and experimentally demonstrated. The filter tunability is achieved by rotating the polarization controller. The spectral shift is dependent on rotation direction and the position of the polarization controller. In addition, the adjustable range achieved by rotating the half-wave-plate polarization controller is twice higher than that of the quarter-wave-plate one.

Stimulation of Rare Earths in Quartz Optical Fiber Surface Metallization by Electroless Plating and Electroplating

This research aims to use several kind of rare earth oxides, such as Nd2O3, Yb2O3, Ce2O3 and La2O3, to improve the electroless plating and electroplating processes for surface metallization of quartz optical fiber (silicon fiber) for its practical uses. The effects of the rare earth oxides on the deposition rate of Ni-P-B, the stability of the plating solution and the surface property of the film were investigated and the comparisons of their behaviours were made. The effects of rare earth oxide of La2O3 on the hardness and surface property of the Ni film prepared by electroplating process were studied. The surface morphonogies, compositions and hardness of the Ni-P-B and Ni films were characterized and analyzed by SEM, MSM, ICP and DIMHM, respectively. The experimental results showed that Ce2O3 with the concentration of 4 mg·L-1 was the best one among the four rare earth oxides with suitable concentrations in increasing the deposition rate, enhancing the stability of the electroless plating solution and improving the surface property of the Ni-P-B film. The improvements of the hardness and surface property of the Ni film prepared by electroplating with adding La2O3 were discovered. No obvious influences of Ce2O3 and La2O3 on the compositions of Ni-P-B and Ce free in the Ni-P-B film were found because of its much more nagative deposition potential than those of the used reducing agents in this experiment. The total diameter of the quartz optical fiber with deposited Ni-P-B film and Ni film was about 1.7 mm, which could be satisfactorily for the practical uses of quartz optical fiber in many fields.

Influence of masticatory fatigue on the fracture resistance of the pulpless teeth restored with quartz-fiber post-core and crown

To investigate whether masticatory fatigue affects the fracture resistance and pattern of lower premolars restored with quartz-fiber post-core and full crown, 44 single rooted lower premolars recently extracted from orthodontic patients were divided into two groups of 22 each. The crowns of all teeth were removed and endodontically treated and then restored with quartz-fiber post-core and full crown. Twenty-two teeth in one group were selected randomly and circularly loaded at 45° to the long axis of the teeth of 127.4 N at a 6 Hz frequency, and the other group was not delivered to cyclic loading and considered as control. Subsequently, all teeth in two groups were continually loaded to fail at 45° to the long axis of the teeth at a crosshead speed of 1 mm.min-1. The mean destructive force values were （733.88±254.99） and （869.14±280.26） N for the experimental and the control group, respectively, and no statistically significant differences were found between two groups （P〉O.05）. Bevel fracture and horizontal fracture in the neck of root were the major fracture mode of the specimens. Under the circumstances of this study, it seems that cyclic loading does not affect the fracture strength and pattern of the quartz-fiber post-core-crown complex.

Preparation and Characterization of Alumina-coated Hollow Quartz Fiber Reinforced Al_(2)O_(3)-SiO_(2) Aerogel Composite

Al_(2)O_(3)–SiO_(2)sols were synthesized by using aluminum chloride hex hydrate and tetraethoxysilane(TEOS)as precursors,deionized water and ethanol mixture as the solvent,and propylene oxide as the coagulant aids.Alumina coatings were prepared on the surfaces of hollow quartz filament fiber,then a new lightweight and thermal insulating material were successfully prepared by impregnatingAl_(2)O_(3)–SiO_(2)sol into a needle fabric made by coated hollow quartz filament fiber.The coated quartz fiber,aerogels and composites were characterized by Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),energy dispersive spectroscopy(EDS),nitrogen adsorption-desorption(BET),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and tensile tests.The effects of different fiber and calcination temperatures on the microstructures and properties ofAl_(2)O_(3)–SiO_(2)composite aerogels were investigated.The test results indicate that the mechanical properties of the aerogels are improved by introducing quartz filament fabrics and the introduction of alumina coating improves the thermal stability of the material.Compared to other fibers,Al_(2)O_(3)-coated hollow quartz fiber has significant advantages as reinforcement for composite,and their tensile strength is well retained after high temperature heat treatment.

The Loss of Optical Fiber with Pure Quartz Core and Fluorine—Doped Glass Cladding

The optical fiber with pure quartz core and Fluorine-doped glass cladding was made by POD (plasma outside deposition) technique in some corporations, while we used the creative technique of “overcladding F-doped tube onto quartz rod in high temperature” to make the optical fiber which has the same structure as that from POD, in order to research and compare the influence factors on the loss of the fiber, our research work includes contrast experiments on coating polymers with different refractive index and the concentricity error of the fiber core and cladding. The measurement results show us that there are great differences in the loss spectra between the different fiber samples. We made analysis of it.

Quartz Splint^(TM)高强度石英纤维夹板固定前牙的效果评价

目的:评价应用新型Quartz SplintTM高强度石英纤维夹板固定前牙的临床效果,为治疗牙周炎导致的牙齿松动提供临床依据。方法:应用Quartz SplintTM高强度石英纤维夹板对32例慢性牙周炎患者Ⅱ°、Ⅲ°松动前牙进行固定,观察固定前和固定后3、6个月牙周探诊深度(PD)、牙周附着水平(AL)和牙槽骨高度的变化。结果:松牙固定后3个月,患牙的PD由(4.39±1.26)mm减至(3.16±0.37)mm,差异有统计学意义(P<0.01);AL由(3.56±1.17)mm减至(3.34±1.03)mm,差异有统计学意义(P<0.05)。固定后6个月PD为(3.21±0.25)mm,与固定前比较差异有统计学意义(P<0.01);AL为(3.36±1.31)mm,与固定前比较差异有统计学意义(P<0.05),与固定3个月比较差异无统计学意义。X线显示所有患牙均无进一步的骨吸收,临床状况改善明显。结论:应用Quartz SplintTM高强度石英纤维夹板固定前牙可获得较满意的临床效果。

Quartz Splint^(TM)高强度石英纤维夹板在前牙正畸保持中的应用

目的:评价应用新型Quartz Splint TM高强度石英纤维夹板进行前牙正畸保持的临床效果,为选择适当正畸保持方法提供依据。方法:选择62例完成正畸常规治疗后需局部加强保持者,将患者按照随访时间分为3个月组、6个月组和12个月组。应用Quartz Splint TM高强度石英纤维夹板对前牙进行固定。目视和器械检查每个组保持器有无脱落位点,牙齿间隙及扭转错位有无复发同时检查保持器区域内牙周健康状况,即检查探诊深度(PD)、出血指数(BI)和菌斑指数(PLI),评价Quartz Splint TM高强度石英纤维夹板在前牙正畸保持中的应用效果。结果:62例患者中,60例患者Quartz Splint TM高强度石英纤维夹板均固位良好,无松脱及断裂且间隙及扭转,均未复发。仅有2例纤维夹板分别在第6个月和第12个月个别位点脱落但无断裂。随访期内Quartz Splint TM高强度石英纤维夹板总完好率为96.77%,且患者牙周状况健康。结论:应用Quartz Splint TM高强度石英纤维夹板对前牙区散在间隙或者扭转牙正畸后固定保持可获得稳定的临床效果。

Quartz splint^(TM)高强度石英纤维牙周夹板治疗重度慢性牙周炎的效果评价

目的:观察Quartz splint^(TM)高强度石英纤维牙周夹板治疗重度慢性牙周炎的临床效果。方法:选取重度牙周炎患者48例,随机分为两组,每组24例。A组:在洁治,刮治和根面平整12周后,比较治疗前后的牙周探诊深度和牙周附着丧失情况;B组:在在洁治,刮治,根面平整和Quartz splint^(TM)高强度石英纤维牙周固定后,12周后比较治疗前后的牙周探诊深度和牙周附着丧失情况。结果:两组治疗前后的牙周探诊深度和牙周附着丧失均比治疗前有明显减少,比较有统计学意义。两组治疗后比较,B组较A组减少明显,有统计学意义。结论:对于重度慢性牙周炎,洁治、刮治和根面平整后患者牙周状况会有明显改善,对松动明显的患牙再辅以Quartz splint^(TM)高强度石英纤维牙周夹板固定,牙周状况改善更加明显。

Quartz splint^(TM)高强度石英纤维和Super-Bond C&B粘结剂固定下前牙松动牙疗效比较

目的:比较Quartz splint^(TM)高强度石英纤维和Super-Bond C&B粘结剂固定慢性牙周炎下前牙松动牙的临床效果。方法:选取下前牙松动需要做牙周夹板松牙固定患者40例,随机分为两组。A组:在洁治、刮治和根面平整后,使用Quartz splint^(TM)高强度石英纤维做牙周固定;B组:在在洁治、刮治和根面平整后,使用Super-Bond C&B粘结剂做牙周固定。两组固定后即刻让患者对于固定物做出异物感评价。固定6个月后比较治疗前后的牙周探诊深度和牙周附着丧失情况。结果:两组治疗前后的牙周探诊深度和牙周附着丧失均比治疗前有明显减少,有统计学意义。组间比较,无统计学意义。固定后即刻异物感评价,B组优于A组,有统计学意义。结论:对于下前牙松动的患者,洁治、刮治和根面平整后使用Quartz splint^(TM)高强度石英纤维和Super-Bond C&B粘结剂牙周夹板固定,均可以使牙周状况明显改善。Super-Bond C&B粘结剂牙周夹板异物感小于Quartz splint^(TM)高强度石英纤维。

Self-starting all-fiber PM Er:laser mode locked by a biased nonlinear amplifying loop mirror

A compact all-fiber polarization-maintaining Er:laser using a nonlinear amplifying loop mirror is reported. Fundamental single-pulse mode-locking operation can always self start, with a cavity round-trip decreased from ~ 4.7 m to~ 1.7 m. When the pulse repetition rate is 121.0328 MHz, output pulse is measured to have a center wavelength/3-d B spectral bandwidth/radio frequency signal to noise ratio(SNR)/pulse width of 1571.65 nm/18.70 nm/80 d B/477 fs, respectively. Besides, three states including the exponential growth, damping state, and steady state are investigated through the build-up process both experimentally and numerically. Excellent stability of this compact Er:laser is further evaluated,demonstrating that it can be an easy-fabrication maintenance-free ultrafast candidate for the scientific area of this kind.

Polarization Characteristics of the Deformed Low-Mode Fiber Waveguides with Polarization Conservation

In this work the results of polarization researches of low-optical fiber waveguides with conservation of polarization are presented. Obtained results quite convincingly testify regarding a high sensitivity low-mode regime of work of an optical fiber to anisotropic external influences, in comparison with one-mode regime of work of the same fibre. This result, can represent a big practical value at the realization of high-sensitivity fiber-optical devices of different physical values.

Development of Optical Voltage Transducer Based on Dual-Mode Highly Elliptical-Core Polarization Maintenance Fiber

This paper describes an optical voltage transducer （OVT） for the 35 kV electric power system based on modular interference in dual-mode highly elliptical-core polarization maintenance fiber （E-Core PMF）. The temperature and environmental perturb- bation can be compensated automatically. In the scheme, a quartz crystal cylinder wrapped with highly elliptical-core fiber plays the role of voltage sensor head. The two interference output lobes＇ intensity from the E-core PMF is modulated with the converse piezoelectric effect of quartz crystal. A PZT wrapped with E-core PMF at ground potential serves as the static modular phase difference control and temperature compensation unit. The experiment results indicate that the OVT designed in this paper has satisfying performance and could successfully rejects the temperature perturbation.

石英光纤近红外波段γ辐照效应实验研究

为提高某光学干涉测量系统的耐辐射能力,开展耐辐射光纤选型实验。以剂量率为0.5 Gy·s^(-1)的稳态γ射线和剂量率为5.0×10^(9) Gy·s^(-1)、脉冲宽度约20 ns的瞬态强γ射线为辐照源,获得掺锗、掺氟耐辐射单模光纤和常规G.652光纤在工作波长1550 nm、注入光功率40 mW工况下的辐射感生损耗,结果表明,实验获得的在线辐射感生损耗数据真实可靠;在稳态γ射线作用下,掺锗和掺氟耐辐射光纤的性能差异不大,辐射感生损耗小于17 dB·km^(-1),随着辐射时间的增加,辐射损耗呈现饱和,耐辐射光纤的性能均优于常规单模G.652通信光纤;在瞬态强γ射线作用下,两个不同型号掺氟光纤的性能最优,辐射感生损耗峰值分别为471.5 dB·km^(-1)和608.6 dB·km^(-1),恢复通信时长约μs量级。掺锗光纤的瞬态辐照性能最差,辐射感生损耗峰值为2691.3 dB·km^(-1),在μs时间尺度维持感生损耗饱和状态。

基于QEPAS技术的痕量气体高灵敏度检测系统研究

搭建了一种用于乙炔痕量气体高灵敏度探测的全光式石英音叉增强型光声光谱系统。为了提高系统探测灵敏度,采用光功率放大技术提高激励光源功率,采用直角棱镜使激光束穿过两个共振管,采用光纤珐珀传感技术测量音叉叉股面外单向振动代替面内对称振动;同时利用自稳定技术提高系统的稳定性。采用有限元分析方法对传统商用石英音叉的振动进行了模拟和分析。在对激光调制深度、微共振管结构尺寸和激光输出功率等参数优化基础上,得到了2.9 ppb的系统检测极限,归一化等效噪声系数为2.4×10^(-9)cm^(-1)·W·Hz^(-1/2);二次谐波信号幅值与C_(2)H_(2)浓度呈现良好的线性关系,其线性相关系数达到0.999。最后经过1小时的连续实验验证了通过自稳定技术可以有效提高系统的稳定性。