Parallel-cascaded semiconductor microring resonators for high-order and wide-FSR filters

We demonstrate an optical channel dropping filter (OCDF) using three parallel-cascaded vertically coupled microrings with improved rolloff, bandpass flattening, and wide free spectral range (FSR) compared to a single-ring OCDF using single-mode tightly confined waveguides in both GaAs-AlGaAs and GaInAsP-InP. We achieve FSRs of 30 nm for GaAs-AlGaAs and 40 nm for GaInAsP-InP devices, which are three and four times greater, respectively, than those for single rings. The rolloff is 2.8 times faster than that for a single ring.     

Tunable acoustooptic filters and equalizers for WDM applications

We describe a high performance acoustooptic tunable filter for add-drop application and for signal equalization in WDM telecommunication crossconnects. It results from a thorough investigation in TeO/sub 2/ of bulk collinear interaction, the geometry of which, particularly the direction of propagation of the acoustic wave, has been chosen in order to obtain the best compromise between the spectral resolution of the device and the acoustooptic figure of merit. Less than 40 mW of electric power is needed either to deviate 100% of a selected light wavelength /spl lambda/ at resonance, or to induce a 30-dB attenuation of its intensity. The sidelobes practically vanish for this configuration and the resolution is equal to 0.75 nm (or 94 GHz) for /spl lambda/=1.55 /spl mu/m. Polarization splitters combined with half-wave plates allow to completely get rid of polarization sensitivity problems. The use of optical fibers to collect the signal at the filter outputs, actually contributes to the high performance of the device as a whole. Experiments have been performed by multiplexing three signals in the input fiber, separated by 4, 2, and 1 nm. The transmission of the filter has been examined through the bar and cross state.     

Apodizable integrated filters for coarse WDM and FTTH-type applications

A dual-channel integrated multiplexer, based on holographic Bragg reflector (HBR) devices and exhibiting flat-top, 4-nm-wide channels is demonstrated. Theory calibrated by the achieved performance indicates that HBR waveguide grating devices can be implemented to provide fully integrated and high-performance multiplexer solutions for CWDM and FTTH applications.     

General IIR optical filter design for WDM applications usingall-pass filters

A general design algorithm is presented for infinite impulse response (IIR) bandpass and arbitrary magnitude response filters that use optical all-pass filters as building blocks. Examples are given for an IIR multichannel frequency selector, an amplifier gain equalizer, a linear square-magnitude response, and a multi-level response. Major advantages are the efficiency of the IIR filter compared to finite impulse response (FIR) filters, the simplicity of the optical architecture, and its tolerance for loss. A reduced set of unique operating states is discussed for implementing a reconfigurable multichannel selection filter     

Compact microring notch filters

Microresonator filters reported so far have been all-pole-type filters. We report two experimental realizations of zero-type (notch) filters using GaAs-AlGaAs microring resonators. The first is a ring coupled to one side of a Mach-Zehnder interferometer, the Y-branch of which has an effective splitting angle of 50° with 0.5-dB loss. The second is a ring whose loss exactly matches the coupling to the input/output waveguide with an extinction greater than 20 dB     

Free-standing all-polymer microring resonator optical filter

Free-standing all-polymer microring resonator optical filters as prototypical elements in flexible integrated lightwave circuits are demonstrated. The fabrication and measurement methods are discussed. The measured spectrum shows good agreement with theoretical expectations. The crucial 'critical' coupling condition is achieved, resulting in a measurement limited -27 dB extinction of the filter output on resonances     

SoI基微环谐振可调谐滤波器

采用电子束光刻和ICP刻蚀等工艺制作出绝缘体上Si(SoI)基纳米线波导微环谐振(MRR)滤波器,波导截面尺寸为300 nm×320 nm,微环半径为5 μm.测试结果表明,器件的自由频谱宽度(FSR)为16.8nm,1.55μm波长附近的消光比(ER)为18.1 dB.通过对MRR滤波器进行热光调制,在21.4～60...     

Design of high isolation benzocyclobutene microring resonator

We report the design of benzocyclobutene microring resonator of symmetric coupling made of a readily available polymer with a higher isolation of 43.8 dB, a finesse of 34, and a Q value of 1.5×105. The FDTD method predicts a drop efficiency of almost 80% for a gap of 0.55μm.     

Ultra-small microring resonator based on sub-micrometer fiber

The transfer function of the microring resonator is deduced,and the effects of the normalized loss,coupling coefficient and surrounding media on the resonance performance are investigated thoroughly.Utilizing the improved fused tapering tech-nique and ingenious self-coiling coupling method,a high-quality microring resonator(radius of about 500μm)with larger extinction ratio(>10 dB)and sharper resonance is designed and fabricated by a segment of continuous sub-micrometer fiber.The microring resonator constructed in this way demonstrates extremely small connection loss with communication fiber in contrast to the planar waveguide technology.     

Vertically coupled glass microring resonator channel droppingfilters

Air-clad glass microring resonators vertically coupled to buried channel waveguides are experimentally investigated. Ring radii of 10 μm, and channel drop bandwidths of 5 nm are reported. Vertical coupling eliminates the need for the etching of fine features, and relaxes the alignment of the resonator with respect to the input and output bus waveguides     

On the performance of advanced integrated microring filters for switching applications in next-generation elastic optical networks

We investigate the use of integrated advanced microring resonator-based sum-difference all-pass optical filters for switching applications in circuit-switched elastic optical networks. A practical design taking into account optical losses accordingly to typical reported values for strip waveguides in silicon-on-insulator technology is considered. By incorporating tuning elements (i.e., standard phase shifters), three different synthetized elliptic filters are emulated in the same physical structure showing the potential in terms of bandwidth configurability of the architecture. Practical filter design rules for standard silicon-on-insulator single-mode strip waveguides are also discussed. Beside possible advantages in terms of reduced fabrication costs, simulations performed on Nyquist PM-QPSK signals with different channel capacities over 50, 37.5 and 25 GHz frequency slots suggest that the proposed structure can achieve similar or better performance than commercial spectrum selective switch filters.     

Surface-acoustic-wave resonator filters

This paper presents an overview of surface-acoustic-wave (SAW) resonator filter technology. Given the current state of the art, these filters promise reproducible low-loss (≲6 dB) narrow-bandwidth (500 ≲ f/Δf ≲ 50 000) responses in the VHF and UHF ranges. Devices that contain one or a number of sections, each consisting of a resonant cavity between two grating reflectors and an input and output coupling mechanism, are considered. The initial discussion describes the layout, theoretical characteristics, and typical experimental responses of singlesection two-port filters. The subsequent discussion focuses on multisection devices using any of various intercavity coupling techniques. A generalized analysis and design formalism based on wave-scattering theory is reviewed, and experimental results from a number of device prototypes are given. Finally, practical design and fabrication trade-offs and performance ranges are summarized for a number of configurations.     

Integrated-optic acoustically-tunable filters for WDM networks

The background needed to understand the integrated-optic collinear acoustically tunable optical filters (ATOFs) and the fabrication and performance of both simple and multielement acoustooptic tunable filters is presented. The most important sources of crosstalk between channels simultaneously selected by a single device are discussed. ATOFs have the combined virtues of narrow passband (subnanometer bandwidth), broad tuning range (hundreds of nanometers have been demonstrated), and simultaneous independent multiple-channel filtering. The theory and practice of collinear integrated optic acoustooptic filters is presented. Devices which involve higher-order integration are discussed, including multiple-state filters for enhanced sidelobe suppression and polarization-independent configurations. Various sources of interchannel crosstalk are derived and demonstrated in multiwavelength filtering experiments     

Current-mode high-order OTA-C filters

A new way to implement current-mode continuous-time filters is presented which uses operational transconductance amplifiers (OTAs). Based on the simulation of a signal flow graph on the all-pole lowpass transfer function, the two current-mode realizations of high-order OTA-C filters are obtained.     

竖直耦合型微环谐振器的特性分析

By using the coupled mode theory and the transfer matrix technique,the optical transfer function is presented for analyzing the size of the waveguide,radius of the microring,free spectral range and amplitude coupling ratio of the vertical coupling microring resonator.Under the central wavelength of 1550 nm,optimization and simulation are performed when the central deviation between the ring and the channel is 0,0.5,1μm,respectively, the 3-dB bandwidth of the spectral response is about 0.21,0.09,0.03 nm,and the intensity of the nonresonant light is below—30,—40,—50 dB,respectively.     

基于SOI结构的1×8阵列上下载微环滤波器

利用193 nm深紫外曝光的方法应用CMOS技术,在SOI片上加工制作了1×8阵列上下载微环滤波器,微环半径分别为21.0、20.5、20.0和19.5μm。通过测量直通端的透射光谱,在1 540～1 560 nm的波段上观测到微环阵列谐振波长的透射谱凹陷,对应的消光比均大于15dB,在谐振波长1559.5 nm处的消光比高达35 dB。在半径为20.5μm的微环下载端,测得的波长为1 542.6、1 546.7、1 551.0、1 555.2和1 559.3 nm的下载峰,对应的自由谱宽为4.2 nm。     

Acoustooptic tunable filters in narrowband WDM networks: systemissues and network applications

The system issues and network applications of acoustooptic tunable filters (AOTFs) are discussed. AOTFs are thought to be attractive system components in dense wavelength-division multiplexed (WDM) networks because of their broad continuous electronic wavelength tunability and narrow filter bandwidth. Their unique multiwavelength filtering capability adds a greater dimension of flexibility to network design. The characteristics of the AOTF are reviewed from a system viewpoint and the performance and capabilities of bulk-devices, integrated-optic devices, and fiber-based devices are discussed and compared. Three network applications using the acoustooptic tunable filters are described. The first application is as wavelength-tunable receivers or taps for local users in a subscriber loop distribution network. The second is as multiwavelength tunable receivers in a broadcast local-area cross-connect for packet communication with very-high-throughput data rate. The third is as wavelength-selective space-division switch fabric for routing and cross-connect between central offices. Future prospects and various issues for future research are also discussed     

Passive CCD resonator filters

Novel passive recursive CCD bandpass filters have been realized using standard two-level-polysilicon gate NMOS technology. A Chebyshev bandpass (w/SUB rel,/ /SUB 3/ /SUB dB/=3.1 percent) and a fully integrated CCD signal filter with an extremely narrow 3 dB bandwidth of 97 Hz (Q=1350) at 131.85 kHz center frequency were implemented by means of cascaded CCD resonators. The latter chip contains the necessary clock generation and biasing circuitry realized with dynamic circuit techniques to achieve low power consumption (40 mW per filter). Performing all filtering operations exclusively in the charge domain ensures filter passivity. An extremely stable center frequency and a bandwidth independently controlled by a capacitance ratio are the special advantages of such filters.     

Rectangular optical filter based on high-order silicon microring resonators

The rectangular optical filter is one of the most important optical switching components in the dense wavelength division multiplexing (DWDM) fiber-optic communication system and the intelligent optical network. The integrated high-order silicon microring resonator (MRR) is one of the best candidates to achieve rectangular filtering spectrum response. In general, the spectrum response rectangular degree of the single MRR is very low, so it cannot be used in the DWDM system. Using the high-order MRRs, the bandwidth of flat-top pass band, the out-of-band rejection degree and the roll-off coefficient of the edge will be improved obviously. In this paper, a rectangular optical filter based on high-order MRRs with uniform couplers is presented and demonstrated. Using 15 coupled race-track MRRs with 10 μm in radius, the 3 dB flat-top pass band of 2 nm, the out-of-band rejection ratio of 30 dB and the rising and falling edges of 48 dB/nm can be realized successfully. This work has been supported by the National Natural Science Foundation of China (No.61205062), the Scientific Research Project of Hubei Education Department (No.B2015191), and the Project of Hubei Province Universities Outstanding Youth Scientific Innovation Team (Nos.T201431 and T201633). E-mail:onlyfish@126.com      

A novel self-coupled dual-mode ring resonator and its applications to bandpass filters

A novel dual-mode ring resonator with self-coupled segments, called a self-coupled ring resonator, is proposed. The self-coupling between ring segments provides the same mode perturbation effect as the conventional methods of adding stub, cutting notch, or varying line impedance on the ring resonator. The mode perturbation and transmission-zero generation due to the self-coupling effect are analyzed with the even-odd mode theory. The self-coupled ring resonator can have the capacitive or inductive perturbation simply by controlling the impedance ratio and coupling coefficients of self-coupled sections. For both perturbation cases, the transmission zeros exist at even multiples of the passband center frequency, resulting in wide stopband range. Also, only for the capacitive perturbation case, two transmission zeros are found on both sides of the passband, which brings a pseudo-elliptic bandpass response. In comparison with the regular uniform ring resonator, the self-coupled ring resonator takes shorter ring length, giving the compact size feature when applied to a bandpass filter design. A 2.45-GHz low-temperature co-fired ceramic bandpass filter based on the self-coupled ring resonator was designed to verify the proposed theory.