阵列波导光栅的研究进展

综述了阵列波导光栅的研究进展,分析了其多功能和多应用的特性,展示了它在未来波分复用通信网中巨大的应用前景。     

阵列波导光栅技术及其研究进展(本期优秀论文)

分析了AWG器件的基本原理,并介绍了近年来人们在研制小尺寸AWG、增加器件信道数量,改善器件的损耗、串扰、偏振敏感性和温度相关性等性能,以及AWG与其他器件集成等方面的最新研究进展.     

Modeling and design of arrayed waveguide gratings

The purpose of this paper is twofold. First, a simple but comprehensive and powerful arrayed-waveguide grating (AWG) field model is presented which, based on Fourier optics, borrows some principles of that developed by Takeouchi and coworkers [see, Opt. Express, vol. 6, p. 124, 2000] for the analysis of reflective-type AWGs for optical signal processing, but at the same time adds more features, such as the calculation of device losses and the refinement of the mathematical model to obtain a simple expression for the output field for any input-output waveguide configuration where the meaning of the different high-level parameters of the AWG becomes very clear to the reader. Second, we elaborate on the model developed to present an useful design procedure of the AWG based on two steps illustrated by design flowcharts     

Temperature insensitive arrayed waveguide gratings on InPsubstrates

A temperature insensitive arrayed waveguide grating (TI-AWG) with an InGaAsP-InP material system is proposed. Less than 0.1 Å/°C temperature dependence for all eight channels was achieved for the first time even though we used the InGaAsP-InP material system. This novel characteristic is in good agreement with the design principle of the TI-AWG     

Low-loss flat-top passband arrayed waveguide gratings realised byfirst-order mode assistance method

A novel method of flattening the passband of an arrayed waveguide grating with a small excess loss is described, which employs a new concept that uses the assistance of the weak first-order mode. A 16-channel 100 GHz-spacing demultiplexer with a fibre-to-fibre loss of less than 3.6 dB and a flattened excess loss of 1.85 dB is demonstrated. The 1 dB down passband is widened 2.2 times     

Wavelength-tolerant optical access architectures featuringN-dimensional addressing and cascaded arrayed waveguide gratings

This paper describes two- and three-stage wavelength routed optical access networks, which offer wavelength tolerance by using coarse passband-flattened arrayed waveguide grating routers. An N-dimensional addressing strategy enables 6912 customers to be bidirectionally accessed with multi-Gb/s data using only 24 wavelengths and 1.6 nm spacing. These architectures are designed to map onto standard access network topologies, allowing elegant upgradability from legacy passive optical network (PON) infrastructures at low cost     

一种减小聚合物阵列波导光栅光谱漂移的有效方法

报道了一种在工艺制作过程中减小聚合物阵列波导光栅(AWG)器件光谱漂移的有效方法,通过调整波导芯层的旋涂转速来控制芯层的厚度进而可以有效地减小器件的光谱漂移.AWG器件的设计中心波长为1550.918 nm,制作的AWG器件的实际中心波长为1550.85 nm,即利用该方法使传输光谱的漂移减小到0.07nm,远远小于波长间隔0.8 nm,改善了器件的解复用功能.     

Control of higher order leaky modes in deep-ridge waveguides and application to low-crosstalk arrayed waveguide gratings

In a lightwave circuit using a strongly confined waveguide, higher order leaky modes must be suppressed to obtain ideal characteristics, especially in arrayed waveguide gratings (AWGs). Propagation loss for higher order leaky modes in InP-based deep-ridge waveguides was investigated by simulation and experiment. A highly sensitive loss measurement method based on optical low-coherence reflectometry was used to determine the loss, and the relationship between the loss for the higher order mode and AWG crosstalk was investigated. Optimizing the deep-ridge waveguide parameters, especially the core thickness, the refractive index of the core, and the etch depth under the core, significantly reduced the propagation loss for the higher order leaky mode. The effective elimination of the higher order modes will enable fabrication of low-crosstalk AWG routers.     

偏振控制法紫外写入Bragg光纤光栅的特性分析

结合目前常用光纤布喇格光栅制作方法,详述了一种更加灵活、简单而又有效的制作光纤布喇格光栅的方法,即偏振控制法。该方法是基于:在紫外光s和p偏振方向诱导而成的两个折射率调制剖面之间形成一个π相移,通过改变两个偏振方向上光强比例,就能够控制调制量和诱导相移。它的优点是写入的光栅具有多相移和不均匀切趾剖面的特点,其应用前景广泛。     

Crosstalk reduction in N×N WDM multi/demultiplexers bycascading small arrayed waveguide gratings (AWG's)

This paper shows a new scheme which improves the crosstalk performance of large optical multi/demultiplexers, a key component in wavelength division multiplexing (WDM) systems. This scheme uses arrayed waveguide gratings (AWG's) of various sizes and requires no additional equipment. It is well known that a large multi/demultiplexer can be constructed by cascading small multi/demultiplexers. We have studied the impact of the number and size of AWG stages on crosstalk performance. This paper proves that to obtain a multistage multi/demultiplexer with minimum crosstalk, the total channel number of each AWG stage must be minimized. For example, cascading 10-channel AWG's and 11-channel AWG's improves the crosstalk performance of a 110-channel multi/demultiplexer by about 7.5 dB. Furthermore, the crosstalk performance degradation due to fabrication error is theoretically investigated taking channel bandwidth into account. Optimum design parameters of multistage AWG's are introduced: When the AWG suppression ratio is 30 dB and the ratio of channel bandwidth to channel spacing is about 0.24, the degradation in crosstalk performance due to fabrication error is minimized. The tradeoff between the crosstalk performance and the efficiency in terms of hardware and wavelength are also discussed. It is discovered that this simple scheme can yield a crosstalk-free WDM router. Crosstalk reduction obtained by this scheme allows the realization of flexible multiwavelength networks based on wavelength routing     

Wavelength–time optical CDMA scheme adopting commercial 2m × 2m arrayed waveguide gratings

One new code family with asymptotically optimal cardinality is proposed for high-speed OCDMA networks. This code family has short code lengths and can adopt commercial 2^m × 2^m arrayed waveguide gratings for coder implementation (m is positive integer). The performance analysis shows that the proposed code family has improved spectral efficiencies as compared to wavelength/time codes generated from other coding schemes with asymptotically optimal cardinalities.     

Polarization dependent loss and temperature fluctuations effect on degree of orthogonality in polarization multiplexed arrayed waveguide grating based distribution networks

We analyze the effect of arrayed-waveguide grating (AWG) polarization dependent loss (PDL) on the orthogonality between polarization multiplexed channels in a cascaded AWG-based access network topology. For a single AWG, with 0.5-dB PDL, we find an experimental degradation in polarization multiplexing orthogonality to be a maximum of 0.9/spl deg/, in good agreement with theory. In addition, experimental, and numerically simulated maps of orthogonality degradation versus input states of polarization (SOP) are investigated and found to agree well. Consequently, we analyze the effect of cascaded AWGs and again find that the experimental result of maximum 2.9/spl deg/ degradation in polarization multiplexing orthogonality closely matches theoretical predictions. Thermal variations are also found to have similar effects for all SOPs, with a measured degradation in orthogonality of up to 2.5/spl deg/ for a temperature range between 20/spl deg/C and 55/spl deg/C. Overall, this indicates the robustness of polarization multiplexing, making it applicable for appropriate deployment in bandwidth/user-enhanced access networks based on cascaded AWGs.     

Optical delay line employing an arrayed waveguide grating in fold-back configuration

A novel optical delay line (ODL) using an arrayed-waveguide grating (AWG) in fold-back configuration is proposed and experimentally demonstrated. This fold-back configuration offers crosstalk reduction and loss-imbalance as compared with previously reported loop-back AWG-based ODL. The experimental results show that different highly accurate delays can be obtained with a single AWG over a huge modulation bandwidth (2-18 GHz).     

一种抑制波导窄边缝隙阵列天线交叉极化的方法

为了抑制波导窄边缝隙阵列天线交叉极化电平,采用一种在波导外壁开非倾斜缝隙、在波导内壁开倾斜缝隙的方法。利用电磁仿真软件HFSS进行仿真,得到孤立缝隙与阵中单个缝隙的电导函数。设计了一个47单元X波段波导窄边缝隙均匀直线阵列,与常规缝隙阵列相比,天线交叉极化电平降低了6.8 dB。     

阵列波导光栅在二维光CDMA系统中的应用研究

分析了二维光CDMA系统及系统中采用的地址码的特点,介绍了阵列波导光栅(AWG)的功能,给出了三种基于AWG的二维光CD MA编解码器的结构及其工作原理。最后以二维光正交码为例,分析了采用AWG编解码器的二维系统的性能.结果表明,AWG编解码器可以实现多波长二维光CDMA系统中地址码的快速编解码功能,使系统容量达到Tbit/s量级。     

连续调节激光脉宽的新方法

从理论上预言并在实验上证实,用改变三束入射光之间相对延迟的方法,可以连续地缩短后向波的脉冲宽度。并对影响这一过程的诸因素作了分析、讨论。     

Generation of ultrafast pulse sequences with arrayed waveguide grating multiplexers subjected to modulated external stress

We demonstrate a novel approach to generation of sequences of ultrafast pulses in which external stress is applied to arrayed waveguide grating multiplexers using a corrugated pattern. Stress applied to the grating region modifies the free spectral range resulting in modulation of the response spectrum with the corresponding sequence of ultrafast pulses at each output channel of the device. The repetition rate, number, and width of the pulses within the sequence are determined by the corrugation length and the period of the pattern.     

Polarization dependent loss in polymeric rib channel waveguide

Large polarization dependent loss (PDL) as high as 15 dB was observed in the rib-type channel waveguide fabricated using a birefringent polymer. The PDL mechanism was explained by the mode-mode coupling between the TM mode of a rib and the TE mode of a slab waveguides. This TM-TE mode conversion is due to nonuniform off-diagonal component of the dielectric susceptibility tensor which is generated by a thermal stress during the curing process.     

Low switching threshold using nonlinearities in stopband-tapered waveguide Bragg gratings

We numerically study the nonlinear switching characteristics in a waveguide grating with a linearly tapered stopband. This type of design shows promising results in decreasing the threshold switching power, while simultaneously preserving a significant extinction ratio. We find that the switching threshold changes linearly with the tapering coefficient. The physical explanation for these phenomena is discussed. Potential applications for this type of device include all-optical switches and isolators.