Flexible Optical Waveguide Bent Loss Attenuation Effects Analysis and Modeling Application to an Intrinsic Optical Fiber Temperature Sensor

The temperature dependence of the bending loss light energy in multimode optical fibers is reported and analyzed. The work described in this paper aims to extend an initial previous analysis concerning planar optical waveguides, light energy loss, to circular optical waveguides. The paper also presents à novel intrinsic fiber optic sensing device base on this study allowing to measure temperatures parameters. The simulation results are validated theoretically in the case of silica/silicone optical fiber. A comparison is done between results obtained with an optical fiber and the results obtained from the previous curved optical planar waveguide study. It is showed that the bending losses and the temperature measurement range depend on the curvature radius of an optical fiber or waveguide and the kind of the optical waveguide on which the sensing process is implemented.

Evaluation of the Bending Loss of the Hollow Optical Fiber for Application of the Carbon Dioxide Laser to Endoscopic Therapy

Since carbon dioxide laser is excellent for incision, hemostasis, coagulation, and vaporization of soft tissues, it has been widely applied in clinical treatments as the laser knife. In these days, flexible thin hollow optical fibers transmitting mid-infrared light have been developed, and the application of carbon dioxide laser to endoscopic therapy has become possible. However, it is expected that the irradiation effect is influenced by the change in the laser power at the tip of the hollow optical fiber due to the change in the transmittance by the bending loss. The purpose of this research is to quantitatively evaluate the change in the output power and therapeutic effect by bending the hollow optical fiber in a gastrointestinal endoscope. The change in the transmittance of the hollow optical fiber due to the insertion of the fiber into the endoscope and bending of the head of the endoscope was measured. Then, the relationship between the irradiated laser power and the incision depth for a porcine stomach was investigated. As the results, the most significant decrease in the transmittance of the hollow optical fiber was caused by the insertion of the fiber into the instrument channel of the endoscope, and bending of the head of the endoscope with the angle of 90° decreased the output laser power and incision depth by 10% and 25%, respectively. Therefore, it was confirmed that the bending loss of the hollow optical fiber due to the bending of the head of the endoscope had no significant influence on the endoscopic therapy using the carbon dioxide laser.

Influences of polishing on return loss of optical fiber connectors

With Al2O3 and SiO2 as polishing medium, under different polishing conditions, e.g. with different polishing pressure, polishing time and polishing fluid, the influences of polishing treatment on the return loss of optical fiber connectors were investigated. The return loss of optical fiber connectors is 32CD*238dB before polishing. The results show that dry polishing（i.e. no polishing fluid） with Al2O3 has less influence on return loss of optical fiber connectors, while dry polishing with SiO2 reduces return loss to about 20dB because of the end-face of optical fiber contaminated. The wet polishing（i.e. using distilled water as polishing fluid） with Al2O3 or SiO2 can increase return loss to 45CD*250dB, but wet polishing with Al2O3 may produce optical fiber undercut depth of 80CD*2140nm. Wet polishing with SiO2 should be preferentially selected for optical fiber connectors and polishing time should be controlled within 20CD*230s.

Research on Additional Loss of Guidance Optical Fiber

The factors which cause additional losses of guidance optical fiber in wound state were analyzed.A mathematical model used to analyze the macro-bend losses in the cross region producing in the precision winding process was established.For an actual guidance optical fiber,the measured data of the fiber's additional losses under low temperature and the loss curves with radius were given in the paper.The simulation results were compared with the test data.It shows that the additional losses of optical fiber caused by bending and low temperature can meet the actual requirements of the fiber optical guidance system.The established model can be used to predict the change trend of fiber losses in the winding process with a certain tensile force.

Retinal thickness and vascular parameters using optical coherence tomography in Alzheimer's disease:a meta-analysis

Examining the retinal tissue has the potential to provide a unique method and technique to quantify Alzheimer’s disease-related changes in participants at various stages of the disease.In this metaanalysis,we aimed to investigate the association of various optical coherence tomography parameters with Alzheimer’s disease and whether retinal measurements can be used to diffe rentiate between Alzheimer’s disease and control subjects.Scientific databases including Google Schola r,Web of Science,and PubMed were systematically searched for published articles that evaluated retinal nerve fiber layer thickness and retinal microvascular network in Alzheimer’s disease and control subjects.Seventy-three studies(5850 participants,including 2249 Alzheimer’s disease patients and 3601controls) were included in this meta-analysis.Relative to controls,Alzheimer’s disease patients had a significantly lower global retinal nerve fiber layer thickness(standardized mean difference [SMD]=-0.79,95% confidence intervals [CI]:-1.03 to-0.54,P <0.00001) as well as each quadrant being thinner in Alzheimer’s disease versus controls.Regarding macular paramete rs,values measured by optical coherence tomography were significantly lower in Alzheimer’s disease than controls for macular thickness(pooled SMD:-0.44,95% CI:-0.67 to-0.20,P=0.0003),foveal thickness(pooled SMD=-0.39,95% CI:-0.58 to-0.19,P <0.0001),ganglion cell inner plexiform layer(SMD=-1.26,95% CI:-2.24 to-0.27,P=0.01) and macular volume(pooled SMD=-0.41,95% CI-0.76 to-0.07,P=0.02).Analysis using optical coherence tomography angiography parameters revealed mixed results between Alzheimer’s disease and controls.Superficial vessel density(pooled SMD=-0.42,95% CI:-0.68 to-0.17,P=0.0001) and deep vessel density(pooled SMD=-0.46,95% CI:-0.75 to-0.18,P=0.001) were found to be thinner in Alzheimer’s disease patients whereas the foveal avascular zone(SMD=0.84,95% CI:0.17-1.51,P=0.01) was larger in controls.Vascular density and thickness of various retinal laye rs were decreased in Alzheimer’s disease patients compared to controls.Our results provide evidence for optical coherence tomography technology having the potential to detect retinal and microvascular changes in patients diagnosed with Alzheimer’s disease and aid in monito ring and early diagnosis methods.

2.4Gb/s,50Km Optical Fiber Transmission Using Ti:LiNbO_3 External Modulator

2.488 Gb/s optical fiber transmission experiment using a domestic Ti.LiNbO3 externalmodulator was demonstrated for the first time in China.A receiver sensitivity of -30.3dBmwas obtained at a BER of 10-10after transmission through 50.7 km conventional single modefiber.

Research on Special Optical Fiber under Radiation

The variation of optical spectrum of some special fibers under radiation is studied in this paper. We discuss the loss of optical fiber under the influence of radiation. It shown that the colourated positive ions in the silica fiber core is harmful(i.e. Fe, Cr, Mn, Cu, Co, Ni). In the visible band and near area(0.35μm～0.85μm), the spectral distribution of the common silica fiber is dependent on the radiation total dose and spectral curves of the particular double clad optical fiber is unchanged after the radiation.

OPTIMIZATION OF WDM OPTICAL PACKET SWITCHES WITH SPARSE WAVELENGTH CONVERTERS AND NON-DEGENERATE FIBER DELAY-LINES

This paper investigates the untraditional approach of contention resolution in Wavelength Division Multiplexing (WDM) Optical Packet Switching (OPS). The most striking characteristics of the developed switch architecture are: (1) Contention resolution is achieved by a combined sharing of Fiber Delay-Lines (FDLs) and Tunable Optical Wavelength Converters (TOWCs); (2) FDLs are arranged in non-degenerate form, i.e., non-uniform distribution of the delay lines; (3) TOWCs just can perform wavelength conversion in partial continuous wavelength channels, i.e., sparse wavelength conversion. The concrete configurations of FDLs and TOWCs are described and analyzed under non-bursty and bursty traffic scenarios. Simulation results demonstrate that for a prefixed packet loss probability constraint, e.g., 10-6, the developed architecture provides a different point of view in OPS design. That is, combined sharing of FDLs and TOWCs can, effectively, obtain a good tradeoff between the switch size and the cost, and TOWCs which are achieved in sparse form can also decrease the implementing complexity.

Sn-Zn合金包覆PAN基碳纤维/聚六氟丙烯有机光纤材料的制备

采用Sn-Zn合金包覆聚丙烯腈(PAN)基碳纤维,以聚六氟丙烯为载体制备塑料光纤(POF)皮层材料,并将POF皮层材料与聚苯乙烯光纤芯材进行匹配,研究了材料在力学性能、传输损耗性、光场强度方面的变化。结果表明:Sn-Zn合金表面包覆PAN基碳纤维与聚六氟丙烯结合紧密,作为POF皮层材料的效果良好,在最常见的650 nm波长、100 m内,传输低于100 Mb/s速率数据信息的能力符合要求,光信号基本环绕着光纤芯材传播,没有过多的光信号因为皮层材质的缘故而散失,表明该皮层材料与聚苯乙烯光纤芯材的匹配性较高。

基于外部气相沉积的S+C+L波段低色散斜率大有效面积非零色散位移光纤的设计与制备

针对现有光纤无法满足宽带光密集波分复用系统传输和S+C+L波段粗波分复用的要求,设计了一种具有中心凹陷的三角形芯+环形的折射率剖面,利用外部气相沉积工艺制备了一种非零色散位移光纤,并通过调整第一芯层的相对折射率和第二芯层与第一芯层的半径比,探究了其对光纤衰减、色散斜率和有效面积等参数的影响。研究发现,当第一芯层的相对折射率逐渐增大且第二芯层与第一芯层半径比逐渐减小时,零色散波长和有效面积逐渐减小。当第一芯层的相对折射率在0.52%~0.53%,芯层半径比在2.6~2.7时,光纤的有效面积接近70μm^(2),零色散波长在1420 nm附近,在1550 nm波段的色散系数大于8 ps·nm^(-1)·km^(-1),色散斜率为0.059 ps·nm^(-2)·km^(-1),可以较好地抑制传输过程中光非线性效应,满足长途干线网与城域网的使用要求。

Optimization of highly nonlinear dispersion-flattened photonic crystal fiber for supercontinuum generation

A simple type of photonic crystal fiber （PCF） for supercontinuum generation is proposed for the first time. The proposed PCF is composed of a solid silica core and a cladding with square lattice uniform elliptical air holes, which offers not only a large nonlinear coefficient but also a high birefringence and low leakage losses. The PCF with nonlinear coefficient as large as 46 W-1 · km-1 at the wavelength of 1.55 um and a total dispersion as low as ±2.5 ps. nm-1 · km -1 over an ultra-broad waveband range of the S-C-L band （wavelength from 1.46 um to 1.625 um） is optimized by adjusting its structure parameter, such as the lattice constant A, the air-filling fraction f, and the air-hole ellipticity η. The novel PCF with ultra-flattened dispersion, highly nonlinear coefficient, and nearly zero negative dispersion slope will offer a possibility of efficient super-continuum generation in telecommunication windows using a few ps pulses.

Stem Cell Ophthalmology Treatment Study (SCOTS)： bone marrow-derived stem cells in the treatment of Leber＇s hereditary optic neuropathy

The Stem Cell Ophthalmology Treatment Study （SCOTS） is currently the largest-scale stem cell ophthal- mology trial registered at ClinicalTrials.gov （identifier： NCT01920867）. SCOTS utilizes autologous bone marrow-derived stem cells （BMSCs） to treat optic nerve and retinal diseases. Treatment approaches include a combination of retrobulbar, subtenon, intravitreal, intra-optic nerve, subretinal, and intravenous injection of autologous BMSCs according to the nature of the disease, the degree of visual loss, and any risk factors related to the treatments. Patients with Leber＇s hereditary optic neuropathy had visual acuity gains on the Early Treatment Diabetic Retinopathy Study （ETDRS） of up to 35 letters and Snellen acuity improvements from hand motion to 20/200 and from counting fingers to 20/100. Visual field improvements were noted. Macular and optic nerve head nerve fiber layer typically thickened. No serious complications were seen. The increases in visual acuity obtained in our study were encouraging and suggest that the use of autolo- gous BMSCs as provided in SCOTS for ophthalmologic mitochondrial diseases including Leber＇s hereditary optic neuropathy may be a viable treatment option.

Mitochondrial variants may influence the phenotypic manifestation of Leber's hereditary optic neuropathy-associated ND4 G11778A mutation

We report here the characterization of a five-generation Han Chinese family with Leber＇s hereditary optic neuropathy （LHON）. Strik- ingly, this Chinese family displayed high penetrance and expressivity of visual loss. The average age-of-onset of vision loss was 18 years in this family. Nineteen （11 males/8 females） of 29 matrilineal relatives in this family developed visual loss with a wide range of severity, ranging from blindness to normal vision. Sequence analysis of mitochondrial genome in this pedigree revealed the presence of the ND4 G 11778A mutation and 44 other variants belonging to Asian haplogroup M7b. The G 11778A mutation is present at homoplasmy in matri- lineal relatives of this Chinese family. Of other variants, the C01 G6480A, ND5 T12811C and Cytb A15395G located at highly conserved residues of corresponding polypeptides. In fact, these variants were implicated to be involved in other clinical abnormalities. Here, these variants may act in synergy with the primary LHON-associated Gl1778A mutation. Thus, the mitochondrial dysfunction caused by the primary ND4 G11778A mutation may be worsened by these mitochondrial variants. The results imply that the G6480A, T12811C and A15395G variants might have a potential modifier role in increasing the penetrance and expressivity of the primary LHON-associated G11778A mutation in this Chinese family.

Bruch's membrane opening-minimum rim width and visual field loss in glaucoma:a broken stick analysis

AIM：To determine the Bruch＇s membrane opening-minimum rim width（BMO-MRW） tipping point where corresponding visual field（VF） damages become detectable.METHODS：A total of 85 normal subjects and 83 glaucoma patients（one eye per participant） were recruited for the study.All of the patients had VF examinations and spectral-domain optical coherence tomography to measure the BMO-MRW.Total deviation values for 52 VF points were allocated to the corresponding sector according to the Garway-Heath distribution map.To evaluate the relationship between VF loss and BMOMRW measurements,a ＂broken-stick＂ statistical model was used.The tipping point where the VF values started to sharply decrease as a function of BMO-MRW measurements was estimated and the slopes above and below this tipping point were compared.RESULTS：A 25.9% global BMO-MRW loss from normative value was required for the VF loss to be detectable.Sectorally,substantial BMO-MRW thinning in inferotemporal sector（33.1%） and relatively less BMO-MRW thinning in the superotemporal sector（8.9%） were necessary for the detection of the VF loss.Beyond the tipping point,the slopes were close to zero throughout all of the sectors and the VF loss was unrelated to the BMO-MRW loss.The VF loss was related to the BMO-MRW loss below the tipping point.The difference between the two slopes was statistically significant（P≤0.002）.CONCLUSION：Substantial BMO-MRW loss appears to be necessary for VF loss to be detectable in patients with open angle glaucoma with standard achromatic perimetry.

200 Gbit/s SR4光收发模块的研究与设计

针对互联网的高速发展,现代数据中心寻求一种高速率、高带宽的信息传输方式。光纤通信因其大容量以及低损耗的特点脱颖而出。光收发模块是光纤通信系统中完成光电信号转换的关键部件。该文重点分析了200 Gbit/s SR4光收发模块的基本原理,主要阐述了模块的发射单元、接收单元、管理单元及数字处理芯片4个部分。测试了200 Gbit/s SR4光收发模块的主要指标,测试结果表明,模块可以满足协议的各项要求。

高阶轨道角动量传输光纤设计及传输特性研究(内封底文章)

为解决一般轨道角动量传输光纤传输轨道角动量模式数量少、质量差的问题,提出了一种基于正六边形空气孔排列的新型光子晶体光纤结构。该光纤引入了空气填充率高的矩形空气孔以及采用高折射率材料填充环形传输区域,能够有效提高环形传输区域和包层间的折射率差,且正六边形排列空气孔有利于提高模间有效折射率差。经过结构优化得到最优光纤结构,有限元法的分析结果表明,最优结构下,该光纤在常用波段S+C+L+U波段上能够支持142种轨道角动量模式的传输,最高阶数达到36阶。且所提出光纤具有良好的传输特性,本征模式的最高限制性损耗为10−9 dB/m量级,与典型轨道角动量传输光子晶体光纤相比至少降低了一个数量级;最大有效模场面积能够达到206.18μm^(2),最小非线性系数低至0.397 W^(−1)∙km^(−1);色散平坦且最小色散变化低至1.4578 ps/(nm∙km);所有本征模式纯度均在93.4%~96.8%范围内。且该光纤具有较好的制备可行性,对制造精度要求不高。因此,该光纤在基于轨道角动量光纤的复用系统中具有广阔的应用前景,为提高通信容量提供了一种有效手段。

Improved all-optical OR logic gate based on combined Brillouin gain and loss in an optical fiber

Improved all-optical OR gates are proposed, using a novel fiber nonlinearity-based technique, based on the principles of combined Brillouin gain and loss in a polarization-maintaining fiber （PMF）. Switching contrasts are simulated to be between 82.4%-83.6%, for two respective configurations, and switching time is comparable to the phonon relaxation time in stimulated Brillouin scattering （SBS）.

Excess Loss of the Coupling System to Double-Function Optical Circulators Utilizing Lens Twice and Two-Fiber Tips

A new type of double function optical circulator for double fibers is proposed in this paper. Two fiber tips and lens twice are employed in this kind of device as the coupling system for what is believed to be the first time. Because two fiber tips and lens twice are used, the function of optical circulator is duplicated in comparison with conventional optical circulator with single fiber tip. Thus the optical circulator has a low cost and a small volume comparatively. Excess loss of the coupling system and the misalignment of the lens twice in angular error and the position error to the developed circulator are analyzed and discussed by using Gauss wave and double integral in theory. The analysis results show that the excess loss is zero when each distance is equal to f between every adjacent： fraction and without misalignment error in the coupling system. In addition, the excess loss is increasing with increment of the distance error and the angular error. The errors of the angular of the optical axis to lens and the distance between the SL to lens are the main source of the excess loss. The higher the errors are, the higher the excess loss is. It＇s very important for reducing the misalignment errors in the coupling system with high ratio of coupling to achieve low excess loss. Details of design and excess loss in the coupling system of this circulator are presented.

低损耗阶跃型塑料光纤(SI-POF)工艺的研究

介绍一种用高分子材料研制低损耗阶跃型塑料光纤 ( SI- POF)的新型工艺流程 ,采用甲基丙烯酸甲酯 ( MMA)与其他高分子材料共聚合成一种阶跃型折射率分布塑料光纤 ( SI-POF) .该光纤采用含氟树脂包层 ,可以降低损耗 .原料的精馏提纯、聚合反应、拉丝等整个工艺过程都处在一个密闭系统中 .探讨聚合反应方式对塑料光纤导光性能的影响 ,从而获得性能优异的塑料光纤 ,光纤的使用距离为 5 0～ 1 0 0 m,其导光性能为 :光损耗小于 2 0 0 d B/ km;数值孔径为 0 .35～ 0 .5

面向单纤100Tbit/s容量的光传输技术

随着信息社会对通信需求的急剧增长,运营商对骨干网传输容量进行扩展的需求日益迫切。首先对单纤100 Tbit/s容量的光传输技术的背景进行了简单介绍;接着对近年来国内外超大容量单模单纤光传输实验进行了比较;之后详细分析了实现单纤100 Tbit/s容量光传输系统的技术路线,并重点介绍了在国内首次实现的C/L波段100.2 Tbit/s超大容量双偏振DFT-S 128QAM OFDM信号传输80 km G.652光纤的系统实验;最后,对面向单纤100 Tbit/s容量的光传输技术的研究前景进行了展望。