Performance analysis of metro WDM network based on an optical cross connects and arrayed waveguide grating demultiplexer

In this paper, we have demonstrated the quality-of-service offered by the metropolitan area network which is based on optical cross connect (OXC) and arrayed waveguide grating (AWG) demultiplexer operating at 10 Gb/s with 0.1 nm channel spacing for NRZ signal transmission. The data is successfully transmitted to a distance of 40 km with a reasonably good BER of 2.388 × 10⁻³⁵. The OXC and AWG demultiplexers in the proposed architecture allow incremental expansion in terms of the number of wavelength channels to be transmitted. Dispersion and crosstalk are the main signal-degrading factors arising from the operation of the OXC and the effectiveness of each factor is individually investigated.     

Single AWG based clock extraction from WDM signals with mixed formats and mixed bit-rates

A simple and flexible simultaneous clock extraction for WDM signals with mixed modulation formats and bit-rates is proposed and demonstrated using a single commercial arrayed waveguide grating (AWG), which acts both detuned multi-channel filter and demultiplexer for the input signals. By using an AWG with 100 GHz spacing, clock extraction from transmitted multi-channel nonreturn to zero (NRZ) and NRZ differential phase shift keying (NRZ-DPSK) signals at mixed bit-rates from 10 to 40 Gb/s with 200 GHz spacing is achieved simultaneously. By cascading a clock recovery module, clock signal can be easily recovered from the preprocessed signals with enhanced clock tones.     

A concise design of 16 × 16 polymer AWG with low insertion loss and crosstalk

In this paper, a 16-channel arrayed waveguide grating multiplexer (AWG) has been designed using polymer materials with 1.5% refractive index difference. Certain important parameters are optimized using the coupling mode theory and Beam Propagation Method. The factors that affect the insertion loss and the crosstalk are analyzed in this paper. In our design we introduced the parabolic taper structure and evaluated the suitable number of the arrayed waveguide, obtaining a total insertion loss of 2.19 dB. For obtaining a low crosstalk we evaluate the pitches of adjacent input/output waveguides ΔX and arrayed waveguides d as different values. We chose the value of ΔX about 2.5 times of d by enlarging the pitches of adjacent input/output waveguides. The crosstalk of the designed AWG is lower than −40 dB.     

Pulse-width tunable multi-channel NRZ-to-RZ conversion with duplicate output

We demonstrate multi-channel non-return-to-zero (NRZ) to return-to-zero (RZ) conversions with tunable output pulse-width and single-to-dual function, using a phase modulator and an array waveguide grating (AWG), which acts both detuned multi-channel filter and demultiplexer. Four-channel NRZ signals after transmission can be converted to eight-channel RZ signals with timing jitter and extinction ratio improvement. Further transmission and bit error ratio (BER) measurements for the converted RZ signal show a good performance compared with conventional one.     

Comparative investigation and suitability of various data formats for 10 Gb/s optical soliton transmission links at different chirps

This paper presents the comparative investigation and suitability of various data formats for optical soliton transmission links at 10 Gb/s for different chirps (−0.7 to 0.7). Here the investigations focused on data formats: NRZ, RZ soliton, RZ raised cosine and RZ super Gaussian. The comparative results and suitability of data formats is based on various performance measures such as Q-factor, eye opening, BER and jitter. It has been indicated that RZ super Gaussian yields the highest value of Q (34.08 dB), good eye opening and lowest BER.     

小尺寸低折射率差硅基二氧化硅阵列波导光栅

随着AWG型器件在光通信系统中的大规模应用,对低成本AWG芯片的需求越来越多。在各种降成本方案中,减小AWG芯片的尺寸是最有效的方法之一。本文介绍了一种新型小尺寸低折射率差硅基二氧化硅阵列波导光栅（AWG）的设计。在该AWG中,输入波导/输出波导与平板波导连接的部分制作成两侧为空气槽的高折射率差波导,所以在与输出平板波导连接处的相邻输出波导间距较小,这样可以在设计上缩短平板波导的长度、减少阵列波导的数量,实现较小的AWG芯片尺寸。该AWG的其它部分,如输入/输出波导与光纤耦合的部分、阵列波导光栅等均采用常规的低折射率波导工艺,所以就同时具有与常规的低折射率波导AWG相同的优点：如低耦合损耗、较好的串扰以及光学特性等。根据这个原理,设计了一种40通道100 GHz频率间隔的低折射率差硅基二氧化硅AWG,其芯片尺寸只有23.88 mm?10.5 mm,是传统相同材料制作的AWG尺寸的1/6。     

Modeling of arrayed waveguide grating for wavelength interrogation application

We have proposed and discussed a design of arrayed waveguide grating (AWG) for the application of wavelength interrogation. The spectral responses of a silica-based 16 channel AWG with channel spacing 1.6 nm have been simulated when different receiver waveguide spacing are used. It was found that the 3-dB bandwidth is reduced about 50% as the receiver waveguide spacing increasing from 20 μm to 30 μm. The effect of bandwidth of the spectral response on wavelength resolution of AWG based interrogator has been estimated and discussed.     

基于多模干涉耦合器的阵列波导光栅设计研究

研究了基于多模干涉(MMI)耦合器的阵列波导光栅(AWG).通过模式传输分析方法,分析了多模干涉耦合器及阵列波导;并给出在硅基底上的二氧化硅波导上四通道100 GHz-AWG普通结构和紧凑结构的设计结果.     

A novel wavelength dispersive device with a dispersive element based on staircase-like straight and parallel arrayed waveguides

We propose a new type of arrayed waveguide grating (AWG) multiplexer/demultiplexer based on modified group refractive index. This device is composed by an array of straight and parallel waveguides of equal length and each waveguide consist of two sections with different width. The length of the two sections are changed from a waveguide to the adjacent one following a linear dependence resulting in a wavelength dispersive waveguide array. An example of the device design for silicon-on-insulator (SOI) platform is provided and numerical simulations have been carried out for various arrayed waveguide parameters. We demonstrate that the group index modification can be used for tailoring device dispersion properties, and that it can also result in new dispersion characteristics predicted numerically not observed in conventional AWGs. Additional advantages are that the demultiplexer does not necessarily require bending waveguide sections as in a conventional AWG (de)multiplexers, and thus yields highly compact devices with potentially very low insertion loss. Channel spacing of 1 nm have been predicted for sub-micron waveguides sizes. In this paper it is also proposed a novel wavefront converter based on waveguide array lens-like element with waveguides broadened sections. Numerical results for different input/output geometries are analized.     

A novel fiber Bragg grating interrogating sensor system based on AWG demultiplexing

A fiber Bragg grating (FBG) interrogating technique based on the relative intensity-demodulating and the demultiplexing of an arrayed waveguide grating (AWG) is presented in this paper. The analytical simulation and the experiment validate the feasibility of this setup. Both theoretical and experiment results show that the shift of the Bragg wavelength of the FBG sensors can be precisely interrogated by the relative intensity reading of two-adjacent-channels of the AWG-based demultiplexer. Errors caused by the light source fluctuation and micro-band losses can be reduced with the relative technique. This technique potentially offers a low-cost, compact, and high-performance solution for the interrogation of FBG distributed sensors.     

阵列波导光栅的简便模拟方法及应用

结合等效折射率方法并利用高斯光束近似给出了一种简便的模拟计算阵列波导光栅方法,可实现AWG锔模拟模拟计算结果与理论公式计算结果吻合利用这种模拟方法,模拟了一个阵列波导光栅(AWG)实例,并考察了阵列波导条数对器件性能的影响,最后分析了制造工艺误差对器件性能的影响     

阵列波导光栅解复用器输入/输出波导结构串扰的数值分析

本论文采用Marcatili方法分析矩形波导的模场特性,在此基础上计算了AWG波分复用/解复用器串扰与输入/输出波导间隙参数(dr/w),波导结构参数V的变化关系.计算了串扰值一定时,选取V参数与dr/w的关系曲线.分析了在不同折射率差波导中,串扰与偏振的相关性,为器件的整体优化设计提供了参考数据.     

AWG中波导间耦合造成的相位畸变的分析

用(1,1)阶Pad啨近似的广角BPM计算了阵列波导光栅(AWG)中由于阵列波导间耦合造成的相位畸变以及由于相位畸变引起的相位误差分别考虑了光从中心/非中心输入波导入射两种情况结果表明,波导间的耦合会造成显著的相位畸变,但由此引起的相位误差却很小,光从中心输入波导入射时对应的相位误差10-3rad,从非中心输入波导入射时的相位误差约为10-2rad针对波导阵列边缘效应引起的相位畸变,设计AWG结构时,在阵列部分两侧增加了边缘辅助波导结构,从而消除了边缘效应,使得边缘阵列波导对应的相位误差从10-1rad量级减小为10-3(10-2)rad量级.     

用Stigmatic Points法设计高性能80通道阵列波导光栅器件

采用Stigmatic Points方法改进传统的罗兰圆结构设计方法,给出一个实用化、高性能80通道阵列波导光栅器件设计方案.对采用这两种设计方法得到的器件性能结果进行了比较分析,指出了传统设计方法在设计大通道数阵列波导光栅器件中存在的问题以及Stigmatic Points方法对器件性能的改进.     

Optimization of Optical Add-Drop Multiplexers Based on Arrayed Waveguide Gratings with Fabrication Errors for Transparent Optical Networks

A transparent optical network (TON) composed by optical add-drop multiplexers based on arrayed waveguide grating (AWG) with fabrication errors is optimized for 10 Gbit/s per channel and channel spacing of 25 GHz. The optimization takes into account the effect of inter-symbol interference, amplified spontaneous emission noise accumulation, and coherent and incoherent homodyne crosstalk. Numerical results reveal that AWG fabrication errors can have a high influence on the TON performance; however, in all investigated situations, they do not affect the AWG parameters values corresponding to the optimum AWG frequency response. This surprising behavior is due to the fabrication errors affect mainly the AWG response outside the passband for the required AWG crosstalk level. It is shown that the optimum AWG frequency response is a flat-top response with a mean amplitude response outside the passband lower than ?30 dB and the switch isolation should exceed 30 dB.     

A Flattened AWG Demultiplexer with Low Chromatic Dispersion

A design method is introduced to obtain a flat-top arrayed-waveguide grating (AWG) demultiplexer with low chromatic dispersion. A multimode interference (MMI) section is connected at the end of the input waveguide, and a tapered waveguide is connected at the entrance of each output waveguide of the AWG demultiplexer. The design procedure is presented. A design example is given and shown to have a much better performance than the conventional flat-top design using only an MMI section. The insertion loss of the designed AWG demultiplexer is also reduced.     

An Efficient Technique for Analyzing Transmission Characteristics of Arrayed Waveguide Grating Multiplexers

An efficient technique is presented for analyzing transmission characteristics of arrayed waveguide grating (AWG) multiplexers. As an example, calculations using this technique are performed for a polymer 33 × 33 AWG multiplexer around the central wavelength of 1.55 m with the wavelength spacing of 0.8 nm. Computed results show that this technique possesses high accuracy for analyzing the power profile, diffraction efficiency, transmission spectrum, free spectral range and crosstalk of the AWG multiplexer.     

Crosstalk analysis of silicon-on-insulator nanowire-arrayed waveguide grating

The factors influencing the crosstalk of silicon-on-insulator(SOI) nanowire arrayed waveguide grating(AWG) are analyzed using the transfer function method. The analysis shows that wider and thicker arrayed waveguides, outsider fracture of arrayed waveguide, and larger channel space, could mitigate the deterioration of crosstalk. The SOI nanowire AWGs with different arrayed waveguide widths are fabricated by using deep ultraviolet lithography(DUV) and inductively coupled plasma etching(ICP) technology. The measurement results show that the crosstalk performance is improved by about 7 d B through adopting 800 nm arrayed waveguide width.     

Optimization of Optical Add-Drop Multiplexers Based on Arrayed Waveguide Gratings with Fabrication Errors for Transparent Optical Networks

A transparent optical network (TON) composed by optical add-drop multiplexers based on arrayed waveguide grating (AWG) with fabrication errors is optimized for 10 Gbit/s per channel and channel spacing of 25 GHz. The optimization takes into account the effect of inter-symbol interference, amplified spontaneous emission noise accumulation, and coherent and incoherent homodyne crosstalk. Numerical results reveal that AWG fabrication errors can have a high influence on the TON performance; however, in all investigated situations, they do not affect the AWG parameters values corresponding to the optimum AWG frequency response. This surprising behavior is due to the fabrication errors affect mainly the AWG response outside the passband for the required AWG crosstalk level. It is shown that the optimum AWG frequency response is a flat-top response with a mean amplitude response outside the passband lower than -30 dB and the switch isolation should exceed 30 dB.     

Temperature dependence of low loss polymeric AWG

We investigate on the variation of loss and temperature dependence of a polymeric arrayed waveguide grating (AWG) depending on its substrate, by fabricating 16-channel polymeric AWGs with various substrate conditions. Insertion loss for a polymeric AWG on a silicon substrate is measured as low as 3.1 dB. The temperature-dependent wavelength shift for a polymeric AWG detached from the substrate is maintained within 0.1 nm from 20 to 80 °C. But we observe a degradation of insertion loss and a little instability in wavelength characteristics both for the detached polymeric AWG and for a polymeric AWG on a polymer substrate. We investigate on those optical properties of the polymeric AWGs based on measured thermal expansion properties of the polymers.