Impact of Fiber Non-linearity in High Capacity WDM Systems and in Cross-Connected Backbone Networks

The rapidly increasing data traffic volumes will demand for very high transmission capacity and network nodes throughput. Wavelength division multiplexing (WDM) technology will be asked to support many channels on the same fiber, both in point-to-point links and in WDM optical networks. The transmission of a high number of wavelength channels in all these systems is a key issue. This paper analyzes this topic, in both high capacity links and optical networks, highlighting the impact of fiber non-linearity, and addressing the main source of impairments. This is done through the use of a semi-analytical model recently upgraded to account for all the contributions deriving from Kerr effects, particularly four-wave mixing and cross-phase modulation. The analysis reveals that more than one hundred of channels at 2.5 Gbit/s can be transmitted in point-to-point links whose length can span until the order of 1000 km, and 32 channels per fiber, at the previous bit rate, can be handled in WDM networks, without dispersion compensation. For a higher number of channels (e.g., 64) dispersion compensation is needed.     

利用光纤熔接点精确计算光缆故障位置

由于目前光缆线路故障排除中依据"全程计算法"计算出的故障位置与实际故障位置有较大误差,因而提出利用中继段内的光纤熔接点来缩短故障计算区间,精确定位光缆故障点.     

Aggregation defragmentation algorithm based on channel density and minimum gap in elastic optical networks

Free-space optics (FSO) is a data relaying technology, which requires a direct line of sight between the transmitter and the receiver units for reliable transmission. FSO communication links have many merits such as high modulation bandwidth, high data transmission rates, low cost, and easy installation process. The performance of FSO link is affected by certain external parameters such as absorption, scintillation, and atmospheric attenuation due to different weather conditions. This paper reports the designing and simulative comparison of two wavelength division multiplexing-based FSO links under rain and snow weather conditions. The proposed system reports successful transmission of \(32\times 10\) Gbps of data along a link distance of 16.5 and 1.07 km under rain and snow weather conditions, respectively, with acceptable performance levels (\(Q\sim \) 6 dB and \(\hbox {BER} \le 10^{-9}\)).     

Fast Characterization of Dispersion and Dispersion Slope of Optical Fiber Links Using Spectral Interferometry With Frequency Combs

We demonstrate fast characterization ( $sim$1.4 $mu hbox{s}$) of both the dispersion and dispersion slope of long optical fiber links ( $sim$25 km) using dual quadrature spectral interferometry with an optical frequency comb. Compared to previous spectral interferometry experiments limited to fiber lengths of meters, the long coherence length and the periodic delay properties of frequency combs, coupled with fast data acquisition, enable spectral interferometric characterization of fibers longer by several orders of magnitude. We expect that our method will be useful to recently proposed lightwave techniques like coherent wavelength-division multiplexing and to coherent modulation formats by providing a real-time monitoring capability for the link dispersion. Another area of application would be in stabilization of systems which perform frequency and timing distribution over long fiber links using stabilized optical frequency combs.      

Detecting misbehavior in distributed wireless interference networks

The paper analyzes the case of K distributed interference coupled point-to-point links, which utilize a general power update algorithm, which converges monotonically. The channels are constant for the duration of the algorithm. In such a system we allow a set of links to have the ability to misrepresent their utilities, i.e. the receiver sends a misrepresented utility to its transmitter. It is shown that the system, i.e., the set of correctly behaving links, has the ability to detect such a behavior, if and only if G _Restricted is irreducible. Here G _Restricted is the restricted global dependency matrix, which captures the effect of interference coupling in the system. We then analyze the special case of the Foschini-Miljanic power update algorithm. After at most K ? 1 steps, all links are able to detect the misbehavior. Example interference networks are discussed to illustrate the results. Finally the applicability of the results to the practically relevant cases of concave, convex and log-convex interference functions is displayed.     

网状WDM网中支持区分可靠性的共享通路保护算法

光纤链路由于共享了某些物理资源(如光缆、管道、通路等),因此存在一定的故障相关性,术语“共享风险链路组(SRLG)”就是用于描述链路之间的这种风险共享关系的。SRLG分离成为保护设计的重要约束。该文研究了支持区分可靠性的SRLG分离共享通路保护设计问题。结合SRLG条件故障概率的概念,提出了部分SRLG分离的共享保护算法PSD-SPP(PartialSRLG-DisjointShared-PathProtection),有效地解决了SRLG分离约束下的区分可靠性设计问题。仿真结果表明该算法既满足了用户的区分可靠要求,又能有效利用资源。     

Integrated Transducer Modules, Connectors and Cable for Industrial Fiber Optic Data Links

Integrated, TTL compatible, point-to-point fiber optic data links have been developed to accommodate arbitrary data formats and provide data transmission over 1-1000 m at 0-15 Mbit/s NRZ data rate with fiber/cable having a bandwidth ≥25 MHz.km. The compact, low profile (0.79 cm) printed circuit board mountable, transmit and receive modules operate from a single +5 V supply and provide automatic link monitoring to simplify interfacing. Single fiber connectors of the ferrule type are described. They achieve attenuation ≤ 2.0 dB and are cost effective and easily installable. The connectors are mechanically terminated to reinforced single fiber cable to withstand a pull force ≥ 150N and multiple makes and breaks.     

光缆线路网的优化

文章通过对因光缆线路中的问题而造成的通信阻断或障碍进行了较全面地分析,提出了光缆线路网优化的必要性,并对如何避免、减少光缆线路障碍、缩短障碍历时、保证通信可靠传输等光缆线路具体的优化措施进行了探讨.     

A novel self-surviving architecture for next-generation OFDM passive optical network supporting colorless ONUs

In this paper, we propose a novel self-surviving architecture for next-generation orthogonal frequency division multiplexing (OFDM) passive optical network (PON) supporting colorless optical network units. The proposed scheme can protect distribution and feeder fiber simultaneously. Two different frequency bands are used in this proposed system for paratactic OFDM-PON. The disrupt signals can be restored via the fiber links of the neighboring OFDM-PON without special protecting fibers. We analytically and experimentally study the receiver sensitivity to downstream 10 Gb/s OFDM signals and upstream 2.5 Gb/s NRZ signals. The proposed architecture is designed mainly for next-generation PON systems.     

Giga-bit CMOS equalizers for high-speed data links

Consumer electronics are experiencing an explosive growth in bandwidth requirements. This growth is driven by demand for fiber-to-the-home Internet connections, the increasing capabilities of in-home consumer devices as well as the demands of multimedia recording and playback in mobile devices. However, traditional copper channels and previous generations of optical fiber experience dispersive effects at data rates above 1 Gbps, leading to inter-symbol interference (ISI). This paper presents a finite impulse response filter-based feed forward equalizer (FFE) to reduce the effect of ISI on these channels. The efficacy is of the FFE is demonstrated by measuring the eye diagrams of a 10 Gbps signal transmitted through an optical fiber as well as a copper backplane with and without FFE compensation. The proposed FFEs successfully compensate ISI for both the optical and copper backplane links. All circuits are fabricated using a 0.18 μm CMOS process.     

All-fiber sensor based on few-mode fiber offset splicing structure cascaded with long-period fiber grating for curvature and acoustic measurement

An all-fiber sensor based on a single-mode–few-mode–single-mode fiber offset splicing structure cascaded with long-period fiber grating is proposed and demonstrated for curvature and acoustic signal measurement. High-order mode is inspired in the few-mode fiber by the offset splicing structure and coupled into the LPFG, resulting in a splitting into two dips of LPFG attenuation band, which are more sensitive to the external environment change. The results of the curvature sensing experiment show that the intensity of the two resonant dips has a linear response to curvature in the range of 0.124–0.304 \({\hbox {m}}^{-1}\), and the sensitivity is about 93.01 \({\hbox {dB/m}}^{-1}\), which is one order of magnitude higher than congeneric curvature sensors demonstrated by other researchers before. Based on the curvature sensing mechanism, the sensor is also demonstrated for acoustic measurement in the range 110–230 Hz. The sensor shows a sensitivity of about 15 mV/Pa at 110 Hz and 4.5 mV/Pa at other frequencies. High sensitivity and easy fabrication make it a preferable candidate for curvature and acoustic sensing in the field of structural health monitoring.     

Pulse-Position Modulation for Transmission Over Optical Fibers with Direct or Heterodyne Detection

The best monomode optical fiber links have bandwidths orders of magnitude greater than that of the information currently transmitted over them. This excess bandwidth can be exploited using digital PPM to improve receiver sensitivity. This paper analyzes the receiver sensitivity of an optical PPM system over a slightly dispersive channel, i.e., where both "wrong slot" and "false alarm" errors are important. It is shown that receiver sensitivity of better than 100 photons per binary bit-time is theoretically possible using direct detection and uncoded PPM. Ideal heterodyne detection should reduce this to below 5 photons per binary bit-time. Timing extraction and a digital modulation method are discussed.     

Statistical analysis on stimulated Raman crosstalk in dispersion-managed fiber links

Power impairments due to stimulated Raman scattering (SRS) in dispersion-managed (DM) fiber links are evaluated theoretically. We extend previous work on the statistical analysis of SRS crosstalk to the case of multiple fiber segments. Closed-form formulas are derived, and the applicable range is presented by comparison with simulation results. The SRS crosstalk in DM fiber links is evaluated using derived formulas, and the preferable configuration of DM fiber links for suppressing SRS crosstalk is discussed. We also evaluate the exact power penalty induced by the SRS crosstalk in consideration of the log-normal waveform distribution due to SRS and non-Gaussian noise and clarify the system bounds in some typical DM fiber links. The developed approach provides a design rule for DM fiber links from the viewpoint of SRS crosstalk suppression.     

Transmission characteristics and reliability of pure-silica-core single-mode fibers

Transmission characteristics and reliability for pure-silica-core single-mode fiber with matched cladding are presented. On account of the "pure" silica core, without any additives, the fiber features the low attenuation and improved chemical stability under the existence of hydrogen and γ-ray radiation. High mechanical reliability and good splicing behavior of the fibers were also confirmed. More than 2000 km of pure-silica-core fiber have been fabricated, exhibiting median attenuation of 0.35 dB/km at 1.3 μm and 0.21 dB/ km at 1.55 μm. The achieved minimum attenuation was 0.154 dB/km at1.55-1.56 mum, which is the lowest attenuation ever reported.     

A wide-dynamic-range, high-transimpedance Si bipolar preamplifierIC for 10-Gb/s optical fiber links

A wide-dynamic-range, high-transimpedance preamplifier IC for 10-Gb/s optical fiber links was developed using a 0.3-μm Si bipolar process. The preamplifier with a limiting amplifier enables a wide dynamic range from 16 μApp to 2.5 mApp and a high transimpedance of 1 kΩ (2 kΩ in the differential output mode). Moreover, careful circuit design achieves a transimpedance fluctuation of 0.5 dBR and an average equivalent input noise current density of 12 pA/√Hz. This preamplifier IC has the highest transimpedance of any Si bipolar preamplifier for 10-Gb/s operation. Thus, the preamplifier is suitable for 10-Gb/s short-haul optical fiber links and can be used to provide a low-cost system     

光波-毫米波无线通信技术

就光波 -毫米波无线通信系统的结构、特点、关键技术和最新进展进行了较全面的论述。尤其是对于毫米波信号的产生、光电子器件的选择、光链路的结构及基站的设计等问题进行了较深入的讨论。     

Multimode optical fiber splice loss: Relating system and laboratory measurements

We examine the splice loss occurring along a multimode fiber regenerator span and compare the results to a "standard" laboratory test condition. Large variations in the splice loss sensitivity to transverse offset of a "reference" splice were seen 1) at the ends of 5 different 8.9-km fiber concatenations and 2) at various locations along one 8.9-km path. These data indicate that significant variations in the modal power distribution exist even at the receiver end of a regenerator span. This is explained by the long coupling lengths (long compared to splice spacing) of low loss fibers and the random amount of mode coupling introduced by the concatenation splices. Splice loss measurements made with an "overfilled" launch condition and a 3-turn 20-mm mandrel wrap mode filter (commonly used in fiber loss measurements) accurately approximated the average splice loss sensitivity along the span for offsets less than 4 μm. i.e., losses less than 0.2 dB. For offsets greater than 4 μm, the mandrel wrap mode filter configuration yields a pessimistic estimate, but is within 30 percent of the average "system" loss for most cases of interest. This demonstrates the usefulness of the mode filter in establishing splice measurement conditions that yield results representative of those seen in a regenerator span.     

用于下线间无线序光缆割接的旧路由光缆法

通过测试旧路由光缆,查找出旧路由光缆同机房侧光缆连接的光纤色谱线序信息,用于处理下线间无线序光缆割接难题。实践证明采用旧路由光缆法进行下线间无线序光缆割接可确保割接完毕后光路、线路直接通,两端光纤无需倒换,并且可按重要线路优先原则进行光缆路由变更。此外,旧路由光缆法还可用于处理光缆故障。     

Fiber-Distributed Indoor High Bitrate Optical Wireless System

In this paper, we describe a wideband Indoor Optical Wireless distribution system based on an infrared communication channel using a dedicated distribution architecture. The idea is to provide narrow line-of-sight indoor free-space optical cells at very high rates through an optical fiber network. The wavelength used is 1,550 nm for eye safety and optical power budget reasons. To validate the system performance using standard On-Off Keying modulation, we calculate the power budget and simulate the overall link, showing that an implementation with commercially available components can lead to 2.5 Gbps operational optical wireless links.     

Effects of Direct Current Bias-Drifting on Radio on Fiber Link

The effects of direct current (dc) bias-drifting on radio on fiber (RoF) links are quantitative investigated and simulated. Single sideband (SSB) modulation and carrier suppressed double sideband (CS-DSB) modulation RoF links are considered, power variation of targeted signal and harmonic suppression on account for bias-drifting are calculated and evaluated. Our results suggest that power variation can be maintained within 1.1 dB with dc bias drift ε less than 5% in the SSB modulation RoF link and the degradation of harmonic suppression is evident with ε exceed 2% in the CS-DSB modulation RoF link.