Measurement of phases and amplitudes of AWG by fitting interference intensities

We measured the phases and amplitudes of an arrayed waveguide grating (AWG) by fitting interference intensities via a frequency domain method. The intensities were recorded as a function of the laser frequency in an interferometer containing the AWG. We fit the theoretical intensity profile to the recorded data via the Monte-Carlo method after filtering out the low-frequency noise. The phases and amplitudes are the parameters in the fitting process, and hence, the values are determined from the final fit. The variations in the measured phase values with the change in the initial condition of the Monte-Carlo process were less than $0.1^\circ $ . The variations in the measured amplitude values were negligible. In order to verify our measurement, we calculated the transmission spectrum of the AWG using the measured phases and amplitudes and compared it with a directly measured spectrum. The calculated and measured spectrums are in good agreement with each other.     

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.     

Parameter optimization and structural design of polymer arrayed waveguide grating multiplexer

First some important parameters are optimized for the structural design of a polymer arrayed waveguide grating (AWG) multiplexer around the central wavelength of 1.55 μm with the wavelength spacing of 1.6 nm. These parameters include the thickness and width of the guide core, mode effective refractive indices and group refractive index, diffraction order, pitch of adjacent waveguides, length difference of adjacent arrayed waveguides, focal length of slab waveguides, free spectral range (FSR), the number of input/output (I/O) channels, and that of arrayed waveguides. Then the bent angles, radii and lengths of all the input/output channels and arrayed waveguides are determined. Finally, a schematic waveguide layout of this device is presented, which contains 2 slabs, 11 input channels, 11 output channels, and 91 arrayed waveguides.     

Design and fabrication of wavelength tunable AWGs based on the thermo-optic effect

In this Letter, a 16 channel 200 GHz wavelength tunable arrayed waveguide grating(AWG) is designed and fabricated based on the silicon on insulator platform. Considering that the performance of the AWG, such as central wavelength and crosstalk, is sensitive to the dimension variation of waveguides, the error analysis of the AWG with width fluctuations is worked out using the transfer function method. A heater is designed to realize the wavelength tunability of the AWG based on the thermo-optic effect of silicon. The measured results show that the insertion loss of the AWG is about 6 d B, and the crosstalk is 7.5 d B. The wavelength tunability of 1.1 nm is achieved at 276 m W power consumption, and more wavelength shifts will gain at larger power consumption.     

Experimental observation of lasering behavior in wavelength-switchable fiber laser with arrayed waveguide grating

A simple and wavelength-switchable fiber laser consisting mainly of an Erbium-doped fiber amplifier (EDFA) which provides the optical gain and an 1 × 40 (1 input channel to 40 output channels) arrayed waveguide grating (AWG) that supports wavelength selection is reported. The lasering behavior in wavelength-switchable fiber laser is investigated experimentally. One can obtain wavelength-switchable single-longitudinal-mode (SLM) single wavelength laser with different wavelength by changing different channel of the AWG as the wavelength selection element. Lasering wavelength hopping in dual wavelength laser operation for low pump power is experimentally observed. The wavelength hopping and the output power of the laser is controlled by using a variable optical attenuator (VOA). The wavelength hopping operation is eliminated for high pump power. One can obtain switchable dual wavelength laser with different wavelength by selecting different two channels of the AWG. The output laser exhibits a good performance having a high sidemode suppression ratio (SMSR), narrow line-width and symmetrical spectrum.     

Fast Tunable Wavelength Sources Based on the Laser Diode Array

We report a demonstration of a fast wavelength tunable source (TWS) based on the laser diode array coupled to the arrayed waveguide grating (AWG) multiplexer. The switching and optical characteristics of TWS make it a candidate for implementing the wavelength-division space switch fabric for an optical packet/burst switching.     

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.     

High-resolution liquid refractive-index sensor using reflective arrayed-waveguide grating

A high-resolution sensor for measuring the refractive index of liquids using a reflective arrayed-waveguide grating (AWG) is proposed. The refractive index of a liquid placed in the groove of the arrayed region is measured via the shift of the maximum intensity in the imaging plane of the AWG owing to the phase change in the region. The refractive index can be monitored in real time by measuring the power ratio between two output waveguides of the AWG with a narrow-band source. A mathematical model based on Fourier optics and wave optics is established. A fitting formula for the relationship between the power ratio and the refractive index of liquid is derived. The results of the study show that the proposed method can eliminate the effects of instability of the light source and the inner loss of the system and provide a refractive index resolution of 10⁻⁷.     

Stable dual-wavelength erbium-doped fiber ring laser with switchable spacing employing controllable channel loss

A stable dual-wavelength erbium-doped fiber ring laser with switchable spacing is proposed and experimentally demonstrated. An arrayed waveguide grating (AWG) incorporating two fiber optic switches (OS) is used to as the wavelength selector. The ring cavity is divided into two cavities by a 30:70 optical coupler. Equalized dual-wavelength outputs are achieved by controlling the variable optical attenuator (VOA) inserted in the lower loss cavity. The wavelength spacing can be tuned from 0.80 to 12.05 nm. The fiber laser has good optical quality with maximum power fluctuation of 1.5 dB and side mode suppression ratios (SMSRs) higher than 71 dB.     

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.     

High repetition rate femtosecond WDM pulse generation using direct space-to-time pulse shapers and arrayed waveguide gratings

For the application of high repetition rate wavelength division multiplexed (WDM) pulse train generation from a femtosecond modelocked fiber laser, the direct space-to-time pulse shaper and a properly designed arrayed waveguide grating (AWG) are equivalent. The analogy between the bulk optics and integrated configuration is explored for this application. The critical design parameters of the AWG are the free spectral range and the pathlength difference between adjacent guides in the array.     

快速计算阵列波导光栅波导耦合系数的修正重叠积分方法

提出了一种修正的重叠积分方法用以计算阵列波导光栅(AWG)波分复用器件中光从自由传输区域到阵列波导的耦合系数,并和光束传播法(BPM)数值方法计算得到的结果做了比较通过比较分析,得出结论:当波导中心距不是太小时,用修正重叠积分这一快速方法是合适的.     

高斯光束计算平板波导自由传输区远场分布及其修正

对近轴近似条件下求解亥姆霍兹方程得到的高斯光束显式传播公式做了分析，同时，基于基尔霍夫衍射理论，在菲涅耳近似的条件下给出了相应的高斯光束在远场的传播公式，在此基础上，对近轴近似条件做出了定量分析，给出了这个近似条件引入的误差，提出了一种计算高斯光束远场分布的修正方法，并采用有限差分-光束传播方法(FD-BPM)来检验各种方法的准确性。把这种修正方法应用到平面光集成波导器件，如阵列波导光栅(AWG)、蚀刻衍射光栅(EDG)等器件的设计和模拟中，可以大大降低工作的复杂性，同时可以得到精确的结果。     

All-optical clock recovery from 10-Gb/s NRZ data and NRZ to RZ format conversion

A non-return-to-zero (NRZ) to pseudo-return-to-zero (PRZ) converter consisting of a semiconductor optical amplifier (SOA) and an arrayed waveguide grating (AWG) is proposed, by which the enhancement of clock frequency component and clock-to-data suppression ratio of the NRZ data are evidently achieved. Alloptical clock recovery from NRZ data at 10 Gb/s is successfully demonstrated with the proposed NRZ-to-PRZ converter and a mode-locked SOA fiber laser. Furthermore, NRZ-to-RZ format conversion of 10 Gb/s is realized by using the recovered clock as the control light of terahertz optical asymmetric demultiplexer(TOAD), which further proves that the proposed clock recovery scheme is applicable.     

Suppression of Polarization Dependence in the Design of a 11×11 Polymer/Si Arrayed Waveguide Grating

In this paper we report an effective work of polarization independence in the design of a 11×,11 polymer arrayed waveguide grating (AWG) multiplexer. Theoretical analysis of the polarization properties is given by using Marcatili method. Numerical simulations are performed for independent polarization and single-mode propagation of a rectangular waveguide and bent waveguide with various geometries. The polarization dependence of the AWG device is successfully suppressed by controlling the relative index difference (Δn) between the core and the cladding, ratio between the core width and thickness (a/b), and bent radius of arrayed waveguides, considering practical technical error. The transmission characteristics of two AWGs for two parameter groups of Δn = 1%,a/b = 2 and Δn = 0.8%, a/b = 1.5, show the wavelength shift of 3.5 and 0.02 nm, respectively. The later group of data, which is used in our work, strongly supports the optimum design that we have identified for the birefringence suppression.     

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     

Polymeric 32-channel arrayed waveguide grating multiplexer using fluorinated poly (ether ether ketone)

In wavelength division multiplexing (WDM) systems, an arrayed waveguide grating (AWG) multiplexer is a key component. A polymeric AWG multiplexer has recently attracted much attention due to its low cost processing and a potential of integration with other devices. Fluorinated poly (ether ether ketone)(FPEEK) is excellent material for fabrication of optical waveguides due to its low absorption loss at 1.55-μm wavelength and high thermal stability. A 32-channel AWG multiplexer has been designed based on the grating diffraction theory and fabricated using newly synthesized FPEEK. During the fabrication process of the Polymer/Si AWG device, spin coating, vaporizing, photolithographic patterning and reactive ion etching (RIE) are used. The AWG multiplexer measurement system is based on a tunable semiconductor laser, infrared camera and a Peltier-type heater. The device exhibits a wavelength channel spacing of 0.8nm and a center wavelength of 1548 nm in the room temperature.     

A novel asymmetric arrayed waveguide grating with different lengths of input/output slabs

A novel arrayed waveguide grating (AWG) with asymmetric configuration is proposed. In this configuration, the length of the output slab region, the width and the spacing of the output waveguides are unequal to the corresponding parts of the input ones. Compared to a conventional symmetric AWG, the asymmetric AWG proposed in this paper has a smaller size without degrading its performance The analytic method used in a conventional symmetric AWG is extended to the asymmetric AWG. A design example of an asymmetric AWG with low insertion loss, low channel crosstalk and wide bandwidth is presented.     

Design and characterization of arrayed waveguide gratings using ultra-low loss Si3N4 waveguides

Planar waveguides with ultra-low propagation loss are necessary for integrating optoelectronic systems that require long optical time delay or narrowband optical filters. In this paper, we review an ultra-low loss planar waveguide platform that uses thin (<150 nm) Si₃N₄ cores and thick (>8 μm) SiO₂ cladding layers. In particular, we discuss the performance of arrayed waveguide gratings (AWGs) fabricated with the platform. We propose the use of a practical design method that takes the statistical nature of worst-case crosstalk into account. We also demonstrate the measurement of amplitude and phase error distributions in an AWG using an optical backscatter reflectometer. We show that the waveguides have phase errors small enough to achieve AWG crosstalk below ?30 dB, while crosstalk below ?40 dB should also be possible with optimization of the component design.