Reconfigurable OADM and OXC designed by a new optical switch

A new dynamically selective optical add/drop multiplexer (OADM) and optical cross-connect (OXC) configuration for dense wavelength division multiplexed (DWDM) networks are proposed. The selective devices are based on fiber Bragg gratings (FBGs), single-sided micro-mirror optical switches (OSWs), and optical circulators (OCs). They are flexible, expandable, and high capacity in DWDM networks if the basic units are cascaded in series. In this paper, fiber collimators in coupling are analyzed in order to characterize the insertion loss and output power equalization in OADM and OXC. “Off-the-shelf” DWDM communication products are used for analysis; as a result, the main insertion loss in the system comes from circulators while the maximum insertion loss deviation comes mainly from FBGs and micro-mirrors. As compared to the other existing reconfigurable OADMs and OXCs, the number of mirrors in the optical switch could be dramatically reduced. The reliability of optical switch operation, therefore, can be enhanced.     

Microoptic grating multiplexers and optical isolators for fiber-optic communications

As new optical devices for increasing further the utility of and to expand the application of fiber-optic communications, grating multiplexers and isolators have been developed for 0.8 μm band employing microoptic approach. The development of these devices is the subject of this paper. The devices have desirable features of small size, compactness, high optical performances, and high reliability. The grating multiplexer consists of a graded-index rod, a blazed reflection grating replicated onto the graded-index rod slanting facet or a wedge facet, and an input-output fiber array. Simple calculations have been done to determine necessary element parameters for a given channel spacing. Experimental results are presented for five-channel multiplexers devised using a SELFOC^®lens. Around 3 dB insertion loss and less than -30 dB crosstalk have been obtained for about 35 nm channel spacing in overall device size of18 times 13 times 50mm. Faraday rotation optical isolators for 0.8 μm band have been miniaturized by employing an efficient paramagnetic glass Faraday rotator, a magnet with a through hole and a folded optics in the Faraday rotator. The path number in the folded optics has been optimized in terms of trading-off between the magnet size and the insertion loss. A 0.9 dB insertion loss including fiber coupling loss and 36 dB isolation have been obtained in overall device size of24 times 24.5 times 42mm. Results on the temperature and wavelength dependence of the isolation are also presented. In addition, fundamental properties of optical circulators for 0.8 μm band and optical isolators and circulators both for 1.3 μm band, developed as extended modifications of the optical isolators for 0.8 μm band, are briefly described.     

Circulators using coplanar waveguide

Bosma's method of analysing stripline circulator operation is modified to suit circulators using coplanar waveguide. One of the circulators designed in this way shows a maximum isolation of 19.1 dB, insertion loss 0.8 dB and VSWR 1.3 or less at a centre frequency of 9.56 GHz.     

双向波长上下路光分插复用器

通过对科技文献的归纳总结和分析比较,介绍了四种实现双向波长上下路的光分插复用器结构和工作原理,它们是：（1）基于FBG和多口光环形器;（2）基于波导光栅路由器和FBG;（3）基于阵列波导光栅（AWG）;（4）基于解复用器／复用器对和光开关的OADM结构。     

OTDR in optical transmission systems using Er-doped fiber amplifiers containing optical circulators

Fault location in optical amplifier transmission systems is described. Optical time-domain reflectometry (OTDR) cannot be used for an optical transmission line containing traditional Er-doped fiber amplifiers (EDFAs) because they contain optical isolators. The authors propose an OTDR scheme that uses new EDFAs containing optical circulators and return transmission lines. The new EDFAs support both OTDR and digital signal transmission. A 280.9 km transmission line containing three of the proposed EDFAs was constructed and tested. Experimental results demonstrated the feasibility of OTDR fault location and 1.8-Gb/s digital signal transmission.<>     

Torus结构的芯片上光互连网络损耗分析和优化

基于硅基波导、十字状波导交叉和基于波导微环的光交换器件的损耗特性,对 Torus结构的芯片上光互连网络建立了损耗模型,利用该模型来对芯片上光互连网络进行光器件级、光路由器级和网络级的损耗特性分析,同时建立芯片上光互连网络损耗自动分析系统。依据该系统可以得到不同网络规模下的最大损耗,并分别分析了基于crossbar、cygnus和crux路由器的torus结构网络的损耗特性。可以得到,传输损耗随着网络规模的扩展而增加,最小的传输损耗出现在M=N时。同时,可以得到采用Crux路由器构成的芯片上光互连网络的传输损耗最小,小于Cygnus构成的芯片上光互连网络约5dB。     

一种基于光纤Bragg光栅的全光纤分/插复用器

研制了用于ＷＤＭ全光网的全光纤型分／插复用器,由两个相同的光纤环行器和串接其间的光纤Ｂｒａｇｇ光栅组成。其中光纤Ｂｒａｇｇ光栅是用紫外光直写方式在普通单模光纤上制成。文中给出了该复用器的上／下路端口隔离度和信道插入抽耗等主要测量结果。其特点是结构简单,可实现信道波长再利用,从而提高网络的灵活性。     

Dissipative Parameters in Ferrites and Insertion Losses in Stripline Y Circulators Below Resonance (Letters)

Extensive microwave loss measurements have been performed at the frequency of 1.3 GHz on below resonance stripline Y circulators loaded with aluminum doped YIG. Extemal x' have been measured on the same compositions. Also, dielectric loss measurements have been carried out. A relation is found which correlates insertion loss in stripline circulators with loss parameters x' and tan /spl delta/.     

Performance Limitations of Lossy Circulators (Correspondence)

For lossy circulators which are not too far from the ideal circulator important necessary inequalities for the insertion loss which constitute interesting performance limitations are derived approximately. The case of semi-ideal circulators is discussed briefly and the validity of the approximations is estimated.     

微流控光脉冲调制器

为了解决常见光调制器偏振依赖或结构复杂的问题,本文基于微流控光学提出一种可控光脉冲调制器。利用基于T形结产生的离散液滴和全反射原理的微流控光开关,将连续光变换成数字脉冲信号,并通过调节液滴的长度和生成速率调制光脉冲的宽度和频率。所提微流控光脉冲调制器具有结构简单、插入损耗低、消光比高、易集成的优点。微流控光脉冲调制器的流场与光场特性被分析,结构被优化。研究结果显示：该光脉冲调制器的消光比为17.74 dB,插入损耗为0.49 dB。     

Design of a High-Power CW Y-Junction Waveguide Circulator

A junction circulator appears inferior in average power-handling capability, although it is compact and light-weight and has good performance. A new type of 100-kW CW waveguide Y-junction circulator is realized by dividing the junction of the circulator into four equal unit junctions in a so-called "multilayer structure," which is water-cooled easily. This circulator has an insertion loss of 0.18 dB and an isolation of 20 dB, and it is compact and economical to build. The design of 30- and 100-kW CW waveguide Y-junction circulators is presented in this paper, which discusses determination of ferrite dimensions and air gap, considers heat generation in the ferrite, and the influence of dc magnetic-field distribution on its performance. The ferrite dimensions and air gap are determined very easily by using this design method, and these have been confirmed by experiment. It was found that a uniform distribution of internal dc magnetic fieId, obtained by considering the demagnetizing dc magnetic field, gives optimum performance. This is a significant design factor for high-power circulators which require minimum insertion loss.     

误差自愈型高隔离度准四端口光环形器的研究与设计

针对现有光环行器内部元件之间存在的角度误差、各种同类异构光环行器不能消除半波片光轴取向误差所导致的隔离度降低、隔离度不一致以及安装调试繁琐等弊端,提出了一种减小或消除误差的双半波片光轴非对称结构方式,设计了一种误差自愈型高隔离度准四端口光环行器,通过理论分析、琼斯矩阵运算和数学软件MATLAB模拟,其插入损耗可达到已有光环行器最小性能指标,而隔离度可以提高5～8 dB.     

New polarisation-control scheme for optical heterodyne receiver using two Faraday rotators

A new state-of-polarisation (SOP) control scheme using two Faraday rotators is proposed. It features low optical insertion loss and quick response. Experiment shows that the receiver output is stable regardless of drastic SOP changes in the signal.     

Novel field installable optical fiber splice and connector for optical access networks

We have developed two types of field installable connection techniques. One is mechanical splicing, which is used to connect coated optical fibers without the need for stripping or cleaning procedures. The other is a field assembly connection technique, which employs a new type of field installable connector that makes it possible to realize a physical contact connection with chamfer grinding. Mechanical splicing is achieved by precisely aligning and directly connecting coated fibers with a capillary. The assembled splice is installed with 1.3-μm single-mode fibers that have an 80-μm cladding and a 125-μm coating and they exhibit good optical performance with a low average insertion loss of 0.2 dB. Connection is achieved with our developed field installable connector by using a chamfered fiber endface and the compression force of the buckled fiber. The assembled connectors achieve physical contact with the chamfered fiber endface, which provides good optical performance with a low insertion loss of 0.11 dB.     

光纤光栅和环行器构成的多路光分插复用器

讨论由光纤光栅和光环行器构成的光分插复用器的结构,性能和特点,提出采用一段刻有多个光纤布拉格光栅的光纤,两个光环行器,WDM复用器和解复用器等器件,构造能够对WDM的多个信道实施分插操作的光分插复用器,该光分插复用器的插入损耗要比简单地把多个单路的光分插复用器进行级联时小得多,波分复用全光网络中的光分插复用技术,是实现波分复用网络的关键技术之一。     

差分环行器的研究进展

基于时空调制(STM)的单端环行器因其输入信号和调制信号的混合,在接近所需频带处将受到互调产物(IMP)的影响,这些IMP不仅会对相邻通道造成干扰,还会限制调制参数。差分环行器通过匹配两个单端环行器,以180°相位差的调制信号分别调制两个单端环行器,从而消除IMP,有效地改善了环行器的插入损耗、带宽及功率容量等指标,提高了环行器的性能,并降低了对调制信号的要求。该文描述了差分环行器的基本原理,对差分环行器的电路结构、调制方式及测试方法进行了总结。对比分析表明,差分体声波(BAW)环行器在插入损耗、隔离度及功耗等方面表现出优异的性能,有望取代大多数商业系统中的铁氧体环行器。     

A new Faraday rotator using a thick Gd:YIG film grown by liquid-phase epitaxy and its applications to an optical isolator and optical switch

A new Faraday rotator using a thick garnet film grown by liquid-phase epitaxy (LPE) has been proposed and film growth technology for the rotator has been investigated. The new Faraday rotator had good features of very low cost and small size, due to high productivity of the LPE-grown film and low magnetic saturation field, respectively. By using the new Faraday rotator, an optical isolator and magnetooptic switch for single-mode fiber systems have been developed. The optical isolator featured 0.8-dB insertion loss and 25-dB isolation at 1.3-μm wavelength. The magneto-optic 1 × 2 switch was independent of light polarization and featured 1.3-1.7-dB insertion loss, -25-dB crosstalk, and 30-μs switching time at 1.3-μm wavelength. Minimum switching voltage was ±5 V. Magneto-optic devices using the new Faraday rotator is practical for use in1.2-1.7-mum wavelength fiber-optic systems, because of good optical properties, compactness, and low cost.     

Parallel-stage-based reconfigurable optical add-drop multiplexer for WDM optical transport networks

This letter proposes a simple and flexible reconfigurable optical add-drop multiplexer (ROADM) based on parallel-stage configuration using Mach-Zehnder-based fiber gratings, 1/spl times/2 optical switches, and Y-model combiners. The proposed ROADM with four-stage parallel configuration is designed and experimentally investigated to show its performance in full wavelength selection and advantages in reducing the discrepancy of the insertion loss between channels and upgrading.     

Non-blocking four-port optical router based on thermo- optic silicon microrings

By using silicon-on-insulator(SOI) platform, 12 channel waveguides, and four parallel-coupling one-microring resonator routing elements, a non-blocking four-port optical router is proposed. Structure design and optimization are performed on the routing elements at 1 550 nm. At drop state with a power consumption of 0 m W, the insertion loss of the drop port is less than 1.12 d B, and the crosstalk between the two output ports is less than-28 d B; at through state with a power consumption of 22 m W, the insertion loss of the through port is less than 0.45 d B, and the crosstalk between the two output ports is below-21 d B. Routing topology and function are demonstrated for the four-port optical router. The router can work at nine non-blocking routing states using the thermo-optic(TO) effect of silicon for tuning the resonance of each switching element. Detailed characterizations are presented, including output spectrum, insertion loss, and crosstalk. According to the analysis on all the data links of the router, the insertion loss is within the range of 0.13—3.36 d B, and the crosstalk is less than-19.46 d B. The router can meet the need of large-scale optical network-on-chip(ONo C).     

Microwave phase shifter using optical waveguide structure

A microwave phase shifter with an integrated optics structure with high efficiency is discussed. The structure and the performance of the device are discussed. Microwave phase shifting was carried out using the fabricated phase shifter of titanium diffused LiNbO₃ optical waveguides. The measured voltage to obtain halfwave phase shift for a 800 MHz microwave signal was 7.0 V. The input microwave power was 21 dBm, and the detected output microwave power was -24 dBm, so the microwave insertion loss was calculated to be approximately -45 dB. The optical insertion loss of the device was -12 dB