Low chromatic-dispersion flat-top arrayed waveguide grating filter

A low chromatic dispersion (CD) flat-top arrayed waveguide grating (AWG) filter with a novel parabolic waveguide horn is proposed, and a 100 GHz-spacing 16-channel flat-top AWG that reduces the CD from -20.9 to -3.2 ps/nm has been successfully fabricated.     

Bragg grating fast tunable filter for wavelength divisionmultiplexing

A Bragg grating fast tunable filter prototype working over a linear tuning range of 45 nm with a maximum tuning speed of 21 nm/ms has been realized. The tunable filter system is based on two piezoelectric stack actuators moving a mechanical device thus compressing an apodized fiber Bragg grating. The filter allows both traction and compression and can work in transmission and in reflection. It is designed to work with a channel spacing of 100 GHz according to the ITU specifications for wavelength division multiplexing systems     

复合光栅腔可调谐波导CO2激光器的研究

本文对一级输出方式的复合光栅腔可调谐波导CO2激光器进行了研究，在340mm的放电长度上，获得大于0．5W的谱线61条，其中10p（20）支线的基模功率为3．5W。我们用复合腔的理论说明了光栅一级输出的优越性。     

Widely tunable polymer long-period waveguide grating with polarisation-insensitive resonance wavelength

A long-period waveguide grating in a polymer channel waveguide, which consisted of a benzocyclobutene core and an epoxy cladding, has been fabricated. By changing the stress in the waveguide through etching of the cladding width, a polarisation-insensitive resonance wavelength thermo-tunable from 1520 to 1610 nm with a temperature range of only 8/spl deg/C was achieved.     

Etched cavity InGaAsP-InP waveguide Fabry-Perot filter tunable bycurrent injection

A short cavity Fabry-Perot (FP) tunable filter was fabricated by chemically assisted ion beam etching (CAIBE) of an InGaAsP-InP waveguide. The FP cavity mirrors were formed by high reflectivity dielectric coatings deposited onto the two etched facets of the cavity. High-speed (less than 3 ns) wavelength-tuning of the filter was achieved by current injection. A super-linear dependence on current injection was observed in the wavelength tuning. The filter was tunable over a continuous range of 4 nm by up to 50 mA current injection. The device had a free-spectral range of 9 nm and gave a contrast ratio of about 10 dB. A theoretical simulation of the filter was developed using a beam propagation method calculation to estimate the reflection efficiency at different mirror tilt angles. The calculated contrast ratio of the filter was in good agreement with the measured result. The calculations showed that 20 dB contrast ratio should be possible by having a facet reflectivity of over 90% and ensuring that the etched facets are off-vertical by less than 1.8     

MEMS tunable SOI waveguide Bragg grating filter with 1.3 THz tuning range for C-band 100 GHz DWDM optical network

A MEMS tunable integrated waveguide Bragg grating-based filter for C-band optical dense wavelength-division multiplexing (DWDM) network is presented and analyzed in this work. Waveguide Bragg grating being a notch filter in the transmission spectrum is used to realize a tunable filter by varying the applied voltages to the fixed–fixed beam loaded with this grating. The strain across the grating is enhanced by choosing MEMS beam configuration such that the metal electrode is the bottom-most layer of the composite fixed–fixed beam. Device dimensions are chosen to achieve a narrow full width half maximum of 0.77 nm, allowing filtering of adjacent channels of 100 GHz DWDM network. A large Bragg wavelength shift of 10.4 nm (1552.52–1562.92 nm) was achieved at 45.8 V actuation providing tuning for 14 DWDM channels with inter-channel cross talk below ? 21 dB, with tuning range of 1.3 THz.

     

Simultaneous interrogation of fiber Bragg grating sensors using anacoustooptic tunable filter

We describe a novel technique to provide demultiplexing of fiber Bragg grating sensors, interrogated using interferometric wavelength shift detection. Amplitude modulation of multiple radio frequency driving signals allows an acoustooptic tunable filter to provide wavelength demultiplexing. We demonstrated a noise limited strain resolution of 150 nanostrain/√(Hz) and a crosstalk better than -50 dB     

A nonreciprocal tunable waveguide directional filter using aturnstile open gyromagnetic resonator

The 4-port waveguide directional filter is a classic network in microwave engineering. The purpose of this paper is to describe one gyromagnetic version using an open gyromagnetic resonator in a dielectric-filled cavity. A property of the circuit is that it behaves as a 4-port circulator with one direction of circulation at one split frequency of the resonator and with the other direction for the other split frequency. An insertion loss between the coupled ports below 1.50 dB and an attenuation or isolation of typically 15 dB between the decoupled ports over most of the tuning range of the filter have been achieved. Its 3-dB bandwidth is typically 65 MHz. A typical tuning range of more than 1 GHz centered at about 10.5 GHz has been separately realized for each split branch     

声光可调谐滤波器中声波导的制作及性能测试

以LiNbO3晶体为基底,SiO2/In2O3为镀膜材料,设计并制作了用于准共线型声光可调谐滤波器(AOTF)的声波导及其叉指换能器(IDT),研究了制作工艺,实验测量了该声波导的传输性能。实验结果表明:在未加声吸收胶的声波导中,声表面波(SAW)来回反射,形成驻波,使能量叠加,影响了传输;而在加了声吸收胶的声波导中,SAW具有良好的传输特性,即射频频率在165~185MHz时,声波导传输的效率达到最高,符合AOTF滤波的中心频率范围。测试结果表明:该声波导能够满足声光滤波的要求,而且制作工艺简单、设计灵活,性能更高。     

基于可调谐FP滤波器的光纤光栅解调系统

为了进一步提高光纤光栅解调系统的性能,提出和研究了一种新颖的基于可调谐F-P(Fabry-Perot)滤波器的光纤光栅解调技术,并以此为基础构建了探测系统。系统使用一个固定波长的参考光纤光栅作为波长参考元件,通过对传感光纤光栅与参考光纤光栅的波长测量与差值运算,消除了可调谐FP滤波器腔长漂移对测量精度的影响。给出压电陶瓷电压对应的伸长量,有效地减小了压电陶瓷非线性对测量的影响,提高了光纤光栅波长的测量精度。在测量范围内,最大非线性偏差为0.5%。     

Efficient miniature fiber-optic tunable filter based on intracoreBragg grating and electrically resistive coating

An electrically tunable reflection filter based on a platinum-coated single-mode optical fiber that contains an intracore Bragg grating has been demonstrated. The device shows a dc tuning range of 2.15 nm with a corresponding electrical power of 0.54 W. Wavelength modulation (WM) has been observed at frequencies lower than 100 Hz. The wavelength shift depends linearly on the electrical input power. A maximum efficiency of 4.1 nm/W is obtained for dc tuning     

A tunable filter with collinear acoustooptical TE-TM modeconversion in a GaAs-AlAs multiquantum-well waveguide

We investigate theoretically an acoustooptic tunable filter (AOTF) based on TE-TM mode conversion by collinear acoustooptic interaction, using the high form birefringence that occurs in a GaAs-AlAs multiquantum-well (MQW) rib waveguide. Mode conversion is achieved using a transverse piezoelectric surface acoustic wave. We propose to use a piezoelectric layer (ZnO or AlN) of 6-mm symmetry, which can be deposited by plasma-enhanced chemical vapor deposition. The c axis is then parallel to the plane of the layer. Under this condition, a transverse piezoelectric surface acoustic wave excited by inderdigital electrodes can propagate within the GaAs-AlAs MQW optical waveguide. TE-TM conversion is then possible with a relatively low acoustic frequency (some tens of megahertz), yielding a high diffraction efficiency and a figure of merit 14 times higher than that of conventional LiNbO₃ filters based on AOTFs     

Resonant grating waveguide structures

Under certain conditions, a resonance phenomenon can occur in waveguide grating structures. Such structures have multilayer configuration, the most basic of which is comprised of a substrate, a thin dielectric layer or semiconductor waveguide layer, and an additional transparent layer in which a grating is etched. When such a structure is illuminated with an incident light beam, part of the beam is directly transmitted and part is diffracted and subsequently trapped in the waveguide layer. Some of the trapped light is then rediffracted outwards, so that it interferes destructively with the transmitted part of the light beam. At a specific wavelength and angular orientation of the incident beam, the structure “resonates”; namely, complete interference occurs and no light is transmitted. This paper reviews previous investigations on the resonance phenomena and presents analytic and numerical models for evaluating the resonance as a function of the geometric and optical parameters of the structures and incident radiation     

Spectral shape tunable band-rejection filter using a long-period fiber grating with divided coil heaters

We have developed a new type of tunable band rejection filter, which provides high spectral-shaping flexibility in a wide tuning range. The filter consists of a long-period fiber grating (LPFG) with divided coil heaters. Each of the divided coil heaters is controlled individually to adjust a temperature distribution along the LPFG and to modify the spectral shape of the LPFG filter. The tunable band rejection filter is demonstrated to function properly when applied as an erbium-doped fiber amplifier gain-flattening filter.     

Electro-optic tunable filter

Theoretical analysis of electro-optic tunable filters (EOTFs) using colinear and noncolinear interactions is presented. An effective electro-optic coefficient is derived for various classes of birefringent crystal. We propose to implement the EOTF using the nonlinear photorefractive effect. The photorefractive EOTF can be used for optical storage.     

Digitally tunable channel dropping filter/equalizer based onwaveguide grating router and optical amplifier integration

We demonstrate a novel and powerful device that permits individual and simultaneous control of all the wavelength channels in a WDM system. The device is based on the monolithic integration of two identical waveguide grating routers with semiconductor optical amplifiers. By biasing appropriately the individual amplifier, each WDM channel can be amplified, detected or modulated. The device exhibits a channel bandwidth of 60 GHz, a channel spacing of 195 GHz and a crosstalk of -19 dB     

FBG传感信号数字化可调谐F-P滤波器解调技术研究

为进一步提高光纤光栅(FBG)解调系统的性能,提出并实现了基于FPGA逻辑控制的可调谐F-P滤波(TFFP)FBG传感数字化解调系统.重点介绍基于TFFP解调技术的工作原理,并给出了此解调系统硬件设计的系统框图.解调实验结果表明,通过与光谱仪的测量数据比较,此解调系统达到了预期的目标,经标定后系统的分辨率达1 pm,动...     

Active semiconductor-based grating waveguide structures

Under certain conditions, a high-finesse resonance phenomenon can occur in a grating waveguide structure (GWS). By varying these conditions, a shift in the resonance wavelength can be achieved. Specifically, utilizing the high finesse property of the GWS, small changes in the refractive index can result in a tuning range larger than the resonance bandwidth. Here, we consider different electric-field and charge carrier mechanisms that can affect the refractive index in semiconductor materials, and exploit them in order to control the refractive index change and, therefore, the resonance wavelength in the GWS. The predicted results are verified experimentally with an active GWS formed with semiconductor materials and operated in a reverse voltage configuration     

Reflective arrayed waveguide grating multiplexer

A high-performance reflective arrayed waveguide grating multiplexer/demultiplexer designed for compatibility with silicon integrated circuit processing is described. The grating, folded by a flat reflecting surface, can be printed in a single-exposure field of a photolithographic stepper. Advanced plasma assisted deposition is used to prepare waveguides with very low loss and minimum birefringence. Multiplexers with 40 channels separated by 100 GHz show intrinsic insertion losses of -2.4 dB, channel uniformity less than 0.6 dB, and very low polarization dependent wavelength shift of 0.012 nm.     

Compact design waveguide grating routers

A novel generic design for waveguide grating routers is demonstrated in the InP-InGaAsP material system that reduces the chip size by 50%, while still maintaining relaxed processing tolerances. Experimental results confirm no degradation in device performance for the compact design when compared to conventional devices