Application of multiple-length-scale methods to the study of optical fiber transmission

It is natural to apply multiple-length-scale methods to the study of optical-fiber transmission because the key length scales span 13 orders of magnitude and cluster in three main groups. At the lowest scale, corresponding to micrometers, the full set of Maxwell's equations should be used. At the intermediate scale, corresponding to the range from one centimeter to tens of meters, the coupled nonlinear Schrödinger equation should be used. Finally, at the longest length scale, corresponding to the range from tens to thousands of kilometers, the Manakov-PMD equation should be used, and, when polarization mode dispersion can be neglected and the fiber gain and loss can be averaged out, one arrives at the scalar nonlinear Schrödinger equation. As an illustrative example of multiple-scale-length techniques, the nonlinear Schrödinger equation will be derived, carefully taking into account the actual length scales that are important in optical-fiber transmission.     

Extraordinary optical transmission brightens near-field fiber probe

Near-field scanning optical microscopy (NSOM) offers high optical resolution beyond the diffraction limit for various applications in imaging, sensing, and lithography; however, for many applications the very low brightness of NSOM aperture probes is a major constraint. Here, we report a novel NSOM aperture probe that gives a 100× higher throughput and 40× increased damage threshold than conventional near-field aperture probes. These brighter probes facilitate near-field imaging of single molecules with apertures as small as 45 nm in diameter. We achieve this improvement by nanostructuring the probe and by employing a novel variant of extraordinary optical transmission, relying solely on a single aperture and a coupled waveguide. Comprehensive electromagnetic simulations show good agreement with the measured transmission spectra. Due to their significantly increased throughput and damage threshold, these resonant configuration probes provide an important step forward for near-field applications.     

Direct image transmission through a multimode optical fiber

One-way transmission of a multipixel image through the multimode optical fiber based on the phase-conjugation principle is realized. Adistortion-compensating hologram for each pixel of an image to be transmitted is superposed on a photoplate. Each hologram is recorded with a reference beam of different beam incidence angle to provide proper wave-front correction for each pixel without any interference from other pixels. The reference beams are holographically generated from a photoplate in which small holographic lenslets are aligned in a matrix pattern. Images of up to 25 pixels are transmitted through the fiber experimentally.     

紫外激光传输用光纤的研制

对PCVD法制备的纯硅芯、掺氟硅芯、掺锗硅芯以及氟锗共掺硅芯光纤预制棒的芯区进行了紫外吸收谱测试，并考察了248nm紫外激光辐照及热处理后紫外吸收谱的变化。结果表明，纯硅芯深紫外区的强吸收尾部延伸至紫外波段，掺氟后使深紫外段的吸收限向短波方向移动，从而降低了其对紫外波段的影响，辐照后纯硅芯的紫外吸收增加而掺氟硅芯的吸收出现下降。掺锗硅芯、氟锗共掺硅芯中均在240nm附近出现了氧不足锗缺陷（GODC）引起的吸收峰，但后者吸收峰强度明显低于前者，因为氟能与GODC发生反应从而降低了GODC浓度，且氟同时还能愈合GeE’，辐照后氟锗共掺硅芯的吸收改变程度也要低于掺锗硅芯，表明掺氟能降低掺锗硅芯的紫外吸收。     

150m聚合物光纤125Mbps传输实验

根据阶跃型聚合物光纤的耦合长度分析了模式耦合对其带宽的影响,结果表明,由于聚合物光纤中存在较强的模式耦合,其传输带宽不是与传输距离成反比而是与传输距离的平方根成反比,从而其带宽得到了很大的提高。在此基础上,使用商用阶跃型聚合物光纤成功地进行了125Mbps·150m的局域网传输实验,对比了系统的发射和接收信号,得到了较好的通信眼图。实验结果显示,聚合物光纤完全可以进行较长距离的高速数据传输,改变了一般认为的聚合物光纤百兆速率传输距离在100m以内的状况。     

一种用HT协议实现光纤传输的数据转换结构

进行了将Hyper Transport(HT)协议用于处理器光纤互连系统的研究,针对现有的处理器互连协议接口不能直接连接光纤传输系统的问题,设计了一种可配置的数据转换结构。该结构通过特定的3B/4B编码模块和相应的并转串电路,将原HT协议数据格式转换成适用于光纤互连的数据格式。该结构的特点是数据格式可配置,编码简单,电路可复用,直流电流平衡性能高,对传输协议透明和适于高速逻辑实现。该结构的提出解决了处理器光纤互连过程中遇到的并行总线多、单路速率低、电流不平衡等问题,为处理器光纤互连提供了简捷的解决方案。采用此方案解决处理器光纤互连的数据格式问题尚属首次。     

Two-dimensional image transmission through a single optical fiber by wavelength-time multiplexing

Serial transmission of image data through an optical fiber is inefficient in the utilization of the channel capacity of the fiber. Parallel image transmission techniques, on the other hand, generally limit the transmission length to a few meters. A novel approach is introduced with which 2-D image data can be transmitted efficiently at high speed over a single optical fiber using wavelength-time multiplexing. Several system configurations designed for different types of input are presented.     

Dispersion-optimized optical fiber for high-speed long-haul dense wavelength division multiplexing transmission

Four non-zero-dispersion-shifted fibers with almost the same large effective area (A(eff)) and optimized dispersion properties are realized by novel index profile designing and modified vapor axial deposition and modified chemical vapor deposition processes. An A(eff) of greater than 71 μm(2) is obtained for the designed fibers. Three of the developed fibers with positive dispersion are improved by reducing the 1550 nm dispersion slope from 0.072 ps/nm(2)/km to 0.063 ps/nm(2)/km or 0.05 ps/nm(2)/km, increasing the 1550 nm dispersion from 4.972 ps/nm/km to 5.679 ps/nm/km or 7.776 ps/nm/km, and shifting the zero-dispersion wavelength from 1500 nm to 1450 nm. One of these fibers is in good agreement with G655D and G.656 fibers simultaneously, and another one with G655E and G.656 fibers; both fibers are beneficial to high-bit long-haul dense wavelength division multiplexing systems over S-, C-, and L-bands. The fourth developed fiber with negative dispersion is also improved by reducing the 1550 nm dispersion slope from 0.12 ps/nm(2)/km to 0.085 ps/nm(2)/km, increasing the 1550 nm dispersion from -4 ps/nm/km to -6.016 ps/nm/km, providing facilities for a submarine transmission system. Experimental measurements indicate that the developed fibers all have excellent optical transmission and good macrobending and splice performances.     

光纤频率传递的链路不对称性分析

基于光纤的频率传递在时频同步体系的构建与应用中占据着重要地位。为了在射频稳相传输系统中定量研究由于温度不对称和波长不对称所引入的延迟波动和色散残余等因素对系统稳定性的影响,使用光学仿真软件搭建了简易频率传递系统与3 000 km光纤链路进行10 GHz射频信号传递的仿真分析。通过分析发现链路中引入的温度不对称对系统频率稳定性影响较小,而波长不对称所导致的影响较大,随着正反向波长的差异增大,系统频率稳定性恶化量级在10^-13/ s以上。此研究分析对实际环境下的长距离光纤频率传递系统的建设及优化具有实际指导作用。     

Noise properties of a bidirectional optical fiber transmission system using Raman amplifers

Abstract

Noise properties of a bidirectional optical fiber transmission system using Raman amplification are analyzed. Analytical expressions for both forward and backward amplified spontaneous emission (ASE) noise are established in terms of system parameters. The signal to ASE noise ratio (SNR) and the achievable repeater length are discussed. Based on the results, we find that there exist optimum pump and initial power levels for the maximum SNR and repeater spacing. The maximum system transmission length and accumulated ASE noise for a multiple‐amplifier system are calculated. A maximum system transmission length up to 5,000 km with 12 dB SNR is then predicted.     

电子探针在有源光纤定量分析中的应用

为给有源光纤的工艺开发和性能研究提供有力支撑,该文利用场发射型电子探针EPMA-8050G对光纤纤芯的元素掺杂微区进行系统的定性定量分析,进一步研究石英基质的测试特点以及测试条件对样品烧蚀的影响.能谱仪(EDS)和波谱仪(WDS)的定性分析结果表明,分析含量较低的元素如稀土元素Yb和轻元素F时,WDS有明显的优势.状态...     

Spatial phase information transmission through an optical fiber by coherence function synthesis

Transmission of one-dimensional spatial phase information by low-coherence light through a single-mode optical fiber is experimentally demonstrated by use of space-time conversion at a 4-f Fourier coherence function shaper and time-space conversion with spectral holography. The dispersion during the fiber propagation can be automatically compensated for with spectral holography. However, space-time coupling caused by the transmitter limits the capacity of information transmittable with one coherence function shaping. A significant advantage in the space-time-space conversion with low-coherence light is that an infinite number of signal channels can be multiplexed with a newly invented delay-time division scheme, which can extend this analog transmission to two-dimensional spatial phase patterns.     

电力通信光传输网络优化的分析与应用

当前电力通信光传输网络技术的优化对于整个电力系统的建设和发展来讲均有着重大的意义,故应加强对问题的重视,加强对技术的分析。文章针对这一方面的内容展开论述,详细的分析了电力通讯光传输网络技术的发展和现状,同时对相关技术的优化措施和技术的整改路线进行了细致的研究,旨在不断促进相关技术的发展,保证光传输网络技术可以得到不断的创新改良。     

Application of thin-film optical filters to the temperaturecompensation of optical fiber grating-based devices

A major problem currently affecting the implementation of in-fiber refractive-index grating-based optical fiber devices is the drift in wavelength modulation due to the change in the ambient temperature. For accurate and reliable long-term operation of these devices, suitable temperature compensation techniques are a necessity. This paper presents a novel temperature compensation technique for in-fiber refractive index grating-based devices and components. The proposed technique is based on the temperature-dependent spectral characteristics of a dielectric multilayer thin-film interference filter fabricated on the endface of refractive-index grating impressed optical fiber. Temperature compensation is achieved by comparing the reflected intensities at the grating-reflected and the interference filter-reflected wavelengths. The proposed scheme also compensates for light source fluctuations and lead-in fiber bending losses     

Effects of mechanical stress on the transmission properties of optical fiber packaged in a composite structure

Optical circuit boards for system-level interconnection may be fabricated by bonding segments of optical fiber, in the configuration necessary for signal distribution, to a substrate such as a printed wiring board. To measure the effects of mechanical stress on optical transmission, a four-point bend test is applied to prototype optical circuit boards. The results show that flexing a board to a strain of approximately 0.3% leads to a decrease in loss of 0.012 ± 0.002 dB for multimode fiber. Flexing of a thin board, in two directions, around 40-in.- (101.6-cm-) bend-radius mandrels decreases fiber loss by almost 1 dB after 700 cycles. Single-mode fiber bonded to aboard, however, exhibits an increase in loss of 0.11 ± 0.05 dB under an induced strain of 0.3%, a change that is not significant relative to typical loss-per-line budgets in real systems.     

Compression of optical pulses spectrally broadened by self-phase modulation with a fiber bragg grating in transmission

We demonstrate experimentally the compression of optical pulses, spectrally broadened by self-phase modulation occurring in the rod of a mode-locked Q-switched YLF laser, with an unchirped, apodized fiber Bragg grating in transmission. The compression is due to the strong dispersion of the Bragg grating at frequencies close to the edge of the photonic bandgap, in the passband, where the transmission is high. With the systems investigated, an 80-ps pulse, which is spectrally broadened, owing to self-phase modulation, with a peak nonlinear phase shift of D? = 7, is compressed to approximately 15 ps, in good agreement with theory and numerical simulations. The results demonstrate that photonic bandgap structures are promising devices for efficient pulse compression.     

改进遗传单纯形混合算法在光纤对接中的应用

本文首先给出了纤端光场分布的3D模型并针对单模光纤与激光器的对接分析了错位、角度偏差等对接效率影响因素。通过与传统的爬山法进行比较,提出将遗传单纯形混合算法应用到光纤对接中。单纯形法是一种局部搜索方法,这种寻优方法收敛速度快,它与遗传算法组合起来可以改善单独使用遗传算法收敛速度慢的缺陷。同时,针对光纤对接要求初始种群小所造成的个体多样性差的缺点,改进了单纯形的反射、压缩系数,有效地避免了遗传操作的过早收敛,并通过仿真结果证明了混合算法可以在10代之内找到光纤对接的最佳耦合点。     

Helicons in an optical fiber

Solutions for nonlinear helical electric and magnetic waves and polarization modes in a quartz fiber are found. Parameters of these modes (the normal velocity of the wave front and the helix pitch) are calculated as functions of the fiber properties and the amplitude and frequency of the electromagnetic field.