Optimal Design of Thin Film Filters for IR Integrated Photonic Amplifiers

This paper addresses in the design of thin film filter for IR broadband integrated photonic amplifiers. A cascaded multilayer medium thin film filter structure is presented. This proposed filter consists of some different filtering unit cells with different central wavelength and bandwidth, and each cell can suppress certain peak gain at a specific wavelength. The intrinsical gain spectrum of amplifier is obtained by solving a set of rate and power propagation equations with finite difference time-domain(FDTD)-based overlapping integral-Runge Kutter(RK) method. The effect of transmittance spectrum of the proposed cascaded multilayer medium thin film filter on flattening gain is discussed. The transmission function of the cascaded multilayer medium thin film filter is obtained. Finally, a real device is fabricated, it is shown that the design is valid.     

Thin Film Filter for Broadband IR Integrated Waveguide Amplifiers

A new S-type of IR integrated waveguide amplifiers, based on erbium-ytterbium co-doped phosphate glass integrated with medium thin film filter, is proposed. The intrinsical gain spectrum of the proposed amplifier is obtained by solving rate and power propagation equations, a thin film filter flattening this intrinsical gain spectrum is designed by genetic algorithm, and fabricated. An average gain >10dB is obtained between 1530nm and 1560nm, and the average gain about 18dB between 1531nm and 1550nm with gain difference of <3dB is achieved.     

Design and Simulation of Broadband IR integrated Waveguide Amplifiers with Long - Period Waveguide Grating Filter

A novel broadband IR integrated Er-Yb codoped phosphate glass waveguide amplifier with a long-period waveguide grating is proposed. The long-period waveguide grating, which is used as a gain equalizer, is directly fabricated in the waveguide. The amplifier model is based on propagation and population-rate equations and includes both uniform and pair-induced up-conversion mechanisms. It is solved numerically by combining overlapping integral and Runge-Kutta(RK) algorithm. The intrinsical gain spectrum of the proposed amplifier is obtained by solving a set of rate and power propagation equations and, the deleterious gain peaking is reduced by the long-period waveguide grating filter. The effects of transmission spectrum of the proposed long-period grating on flattening gain are discussed. An average gain  ~ 20dB between 1532 nm and 1565 nm with gain difference of  < 3dB is achieved.     

基于全光纤M-Z干涉仪的ASE光源增益谱平坦滤波器研究

基于马赫-曾德尔干涉仪(MZI)结构,在Matlab软件中,利用优化的迭代算法、Least Pth-norm算法和AMPSO算法,提出一种用于平坦掺Er光纤(EDF)放大自发辐射(ASE)光源增益谱的级联MZI型全光纤滤波器的优化设计方法,并进行了实验研究。结果表明:采用该方法设计的级联MZI型全光纤滤波器可以有效改善ASE宽带光源输出光谱的平坦度,被平坦波段(1525～1540nm)范围内输出光谱的不平坦度小于±0.73dB,整个C波段光谱3dB带宽为36.344nm。     

Monolithic integration of multilayer filter on vertical surface ofsemiconductor substrate by a bias-sputtering technique

The selective formation of dielectric film on a vertical surface of a substrate by a bias-sputtering technique is discussed. Using this technique it has been possible to achieve the monolithic integration of a multilayer wavelength filter and waveguide photodetector on a vertical surface of a semiconductor substrate. The wavelength filter can be applied to an integrated demultiplexer and photodetector by fabricating an optical waveguide directly on the substrate     

Cascaded coupling: Realization and application to spectral maneuvering

In this paper, we analyze a scheme of three mode coupling referred to as cascaded coupling in an optical fiber by employing a pair of superimposed long period gratings. In the cascaded coupling process, interaction between two modes takes place via an intermediate mode. We show that cascaded coupling gives us an additional degree of freedom to tune the transmission spectrum to achieve desired spectral features by appropriate choice of grating parameters i.e. grating strength, length and wavelength of operation. Applications of the proposed design to achieve flat wavelength response and gain flattening filters for erbium doped fiber amplifiers are presented.     

长周期光纤光栅(LPG)均衡滤波器在光纤放大器中的应用

根据耦合模理论 ,给出了两级关联和非关联长周期光纤光栅的透射率表达式 ,从而指出在进行LPG均衡滤波器设计时 ,应采用非关联的光栅 ,可以构成灵活多变的透射谱 ,非常适合光纤放大器的不同增益谱对均衡滤波器传输特性 (透射谱 )的不同要求。以此为基础 ,设计和模拟计算了 LPG均衡光纤宽带放大器的增益及噪声谱。结果表明 ,采用均衡滤波方式是使光纤放大器增益平坦的有效方法     

Ka频段上变频模块设计

论述一种Ka频段上变频模块设计,对模块的杂散和相位噪声性能做了分析,根据分析结果,设计出合理的变频方案。滤波器采用Ansoft Designer和HFSS软件协同仿真,薄膜工艺制作,获得足够的杂散抑制度从而实现低杂散。应用取样锁相技术合成了相位噪声极低的27 GHz本振。对波导—微带过渡结构进行仿真,并给出仿真结果。从测试结果表明,模块设计实现了低杂散和低相位噪声。     

Synthesis method based on genetic algorithm for designing EDFA gain flattening LPFGs having phase-shifted effect

We propose a new synthesis method based on the genetic algorithm for the design of erbium-doped fiber amplifier gain flattening filters. Our genetic algorithm iterates starting with the long period fiber gratings structure constructed by inserting the phase-shifted long period fiber gratings in the middle of the structure, for the more accurately matched spectrum to the desired erbium-doped fiber amplifier gain flattening filter. To verify a synthesizing technique using the proposed algorithm, we have synthesized the long period fiber gratings structures according to the inverted gain spectrum of a commercially available erbium-doped fiber amplifier over the entire 1525–1570 nm range, theoretically. We have also obtained the synthesized structure was more accurate than the structure without phase-shifted section.     

Gain equalization multiwavelength lightwave systems usingacoustooptic tunable filters

An acoustooptic tunable filter is used to compensate for the gain spectrum variations in multiwavelength lightwave systems containing cascaded fiber amplifiers. Demonstrations of such systems using a circulating loop containing a fiber amplifier and an acoustooptic tunable filter have shown that differential gain compensations of up to 14 dB can be achieved for two arbitrary injected wavelengths     

一种模拟双折射可调谐密集波分复用滤波器的设计

提出了一种基于模拟双折射模块的可调谐偏振光干涉型密集波分复用滤波器(DWDM)的新结构。其由置于起偏和检偏器之间的若干个具有相同结构的模拟双折射模块级联构成。每个模拟双折射模块由两个分别用于分束和合束的双折射晶体、放置于其中的两个具有不同折射率的介质块和一个半波片构成。研究了该滤波器的中心频率的可调谐特性。研究表明，利用该结构的滤波器，在满足一定平坦化要求的情况下，如果小角度旋转模拟双折射模块单元，可以在获得大平坦宽度的通带和阻带以及高隔离度的同时简便地实现中心频率的微调谐。实验中，用单级模拟双折射模块验证了该结构的可行性。     

Modeling of Multi-Input Arrayed Waveguide Grating and Its Application to Design of Flat-Passband Response Using Cascaded Mach–Zehnder Interferometers

We present a theoretical model of a multi-input arrayed waveguide grating (AWG) based on Fourier optics and apply the model to the design of a flattened passband response. This modeling makes it possible to systematically analyze spectral performance and to clarify the physical mechanisms of the multi-input AWG. The model suggested that the width of an input/output mode-field function and the number of waveguides in the array are important factors to flatten the response. We also developed a model for a novel AWG employing cascaded Mach-Zehnder interferometers connected to the AWG input ports and numerically analyzed its optical performance to achieve low-loss, low-crosstalk, and flat-passband response. We demonstrated the usability of this model through investigations of filter performance. We also compared the filter spectrum given by this model with that given by simulation using the beam propagation method     

Single-mode Nd3+-doped graded-index polymer waveguideamplifier

The first graded index (GRIN) polymer waveguide amplifier working at 1.06 μm wavelength has been realized, using a Nd³⁺: photolime gel material combination. Throughput intensity of 3.8 mW at 1.06 μm, corresponding to 8.5 dB gain, was observed when employing a 40 mW pumping laser beam operating at 790 nm. The gain medium is a 2.2 cm waveguide active region with Nd³⁺ concentration of 1.03×10²⁰/cm³. The GRIN characteristic of the photolime gel thin film provides a universal means for implementing polymer-based photonic integrated circuits (PICs) on any substrate of interest     

18GHz场效应放大器的实用设计

本文叙述在17.5～18GHz频带工作的低噪声场效应晶体管放大器之实用设计及其性能.放大器包括三级级联微带放大电路和波导输入/输出端口,获得了4.5dB的噪声系数和17dB的总增益.     

用于S波段光纤拉曼放大器增益平坦的长周期光纤光栅设计

根据实际所测得的S波段光纤拉曼放大器的信号增益谱,通过对长周期光纤光栅具体参数的选定,由两个长周期光纤光栅级联滤波的组合,可以使增益图谱在50 nm(1485-1535 nm)带宽内,增益平坦度达到±0.6dB以内.由三个长周期光纤光栅级联滤波组合,可以使增益图谱在49 nm(1490-1539 nm)带宽内,增益平坦度达到0.5 dB, 55 nm(1485-1540 nm)带宽内,增益平坦度达到1 dB.这对扩大长周期光纤光栅增益平坦滤波器的运用范围,扩大单泵浦S波段光纤拉曼放大器的有效增益带宽有着积极的意义.     

Gain measurements on one, two, and three strained GaInP quantumwell laser diodes

We report on systematic investigations of the modal gain below threshold for one, two, and three compressively strained 680 nm AlGaInP quantum well lasers using the Hakki-Paoli method. Accurate values of the gain are obtained by carefully spacial filtering the light for the fundamental waveguide mode. Gain flattening and peak gain shifts are observed even at moderate pumping levels. It is shown that the gain scales very well with the number of quantum wells. We also observe that gain flattening starts at current densities per quantum well of 700 A/cm ²     

TiO2薄膜的宽光谱特性椭偏法研究

为了获得TiO2薄膜的光学常数,采用德国SENTECH生产的SE850宽光谱反射式光谱型椭偏仪,测量和分析了用光控自动真空镀膜机沉积在K9玻璃上的单层TiO2薄膜,得到了TiO2薄膜在300nm~2500nm宽谱上的光学常数曲线和薄膜厚度.根据TiO2的薄膜特性及成膜特点,考虑了表面粗糙层和界面层对薄膜性能的影响,建模时采用Cauchy指数模型和Tauc-Lorentz模型,对建立的各种模型测量得到的数据进行了分析和比较.结果表明,模型基底/Tauc-Lorentz模型/表面粗糙层可以得到最小的均方差为0.5544,得到的TiO2薄膜的厚度的测量值与TFCalc软件的计算值最接近.该研究结果对TiO2薄膜多层膜膜系设计和制备有参考价值.     

增益钳制掺铒光纤放大器特性研究

报道了一种新型基于环形激光腔的增益钳制掺铒光纤放大器。得到了较好的增益钳制效果和增益平坦度,利用980nm半导体激光器泵浦12m长掺铒光纤形成激光增益,观测到 30nm增益带宽。通过反馈1520nm 激光,在可变衰减器不同值测量了输入信号从- 40 ～10dBm的增益,其小信号增益被钳制在16dB。可为40个波分复用(WDM)信道波长提供增益钳制及平坦的放大功能。     

Standardizable low-pass voice band hybrid circuit filters for pulse code modulation (PCM) communication systems

A standardizable design approach to realize the voice band low-pass filters for a variety of pulse code modulation (PCM) communications systems is described. This design concept incorporates cascaded RC active filter sections, thick and thin film hybrid technologies, and functional tuning to allow the use of the same hybrid design for both transmit and receive filters, for a range of input and output requirements. Tuning, sensitivity analyses, and implementation tradeoffs are described. Thick film implementations, using NPO chip capacitors, with the new high stability resistor inks as well as thin film implementation, using the usual tantalum integrated thin film technology are presented. Very stringent requirements have been successfully met using state-of-the-art hybrid technologies.     

A study of green wavelength-division multiplexed optical communication systems using cascaded fiber bragg grating

This paper studies the performance analysis of wavelength-division multiplexed optical communication systems (WDM). First, flat-gain erbium doped fiber amplifiers (EDFAs) are seriously needed to obtain proper and equal amplification of all channels. Such amplifiers can be designed by intrinsically modifying the host material or extrinsically using proper filters. In this research, we benefit from both the intrinsic and extrinsic methods to achieve sharp flat EDFA output gain using cascaded fiber Bragg gratings (FBGs). Second, the performance of our technique has been evaluated through calculating the bit error rate (BER) and signal-to-noise ratio (SNR) of a WDM system embedded with the reported EDFA flattening system. The parametric simulations of the FWHM of FBGs, SNR, optical power and the transmission distance have shown a noticeable improved performance. Sending data via an optical WDM system will be proven from comprehensive simulations to achieve high quality signal transmission spectrums, increased transmission distances and low power consumption. By extension, the reported design using cascaded FBGs can also be generalized to equalize the gain of any arbitrary profile.