Branch Waveguide Research Articles

Y-Type Branch Waveguide Used in Resonant Micro-Optic Gyro

Resonant Micro-Optic Gyro (RMOG) is a kind of optical sensors measuring angular velocity via Sagnac Effect, which yields different central resonant frequency between the clockwise (CW) and counterclockwise (CCW) light path of a ring-resonator when rotating. In this paper, Y-type branch waveguide is put forward to replace K-type coupler in RMOG to reduce the influence of splitting ratio asymmetry due to fabrication errors and temperature drift. Y-type branch waveguide based on silicon-on-silica is designed and analyzed. Simulation results show that Y-type branch waveguide performs better fabrication tolerance than K-type coupler, which reduces the nonlinear Kerr-Effect induced noise excited by power nonuniformity of the counter-propagating beams, therefore the detection sensitivity of RMOG can be improved.

도파관 슬롯 커플러용 비대칭 복합 아이리스에 의해 급전되는 중심 종방향 션트-시리즈 결합 슬롯에 관한 연구

본 논문에서는 도파관 슬롯 배열 안테나 설계 시 분기 도파관 내에서 결합 슬롯과 복사 슬롯 간의 원하지 않는 고차 모드 결합을 줄일 수 있는 슬롯 커플러용 결합 요소를 제안하였다. 제안된 소자는 수직 교차하는 두 도파관이 공유하는 도파관 광벽에 위치한 중심 종방향 션트-시리즈 결합 슬롯과 이를 여기시키는 비대칭 복합아이리스로 구성된다. 먼저 HFSS를 사용하여 커플러 구조의 산란 계수를 구하고, 결합 슬롯의 T - 회로망 등가 회로의 파라미터를 추출하였다. 또한, 소자의 구조적인 치수를 변화시키면서 공진 길이 및 정규화 어드미턴스와같은 공진 특성을 분석하였다. 결합 슬롯으로부터 <TEX>${\lambda}_g/4$</TEX> 떨어진 단락 블록을 갖는 커플러를 설계 제작하여 측정한 실험 결과는 모의실험 결과와 잘 일치하였다. This paper proposes a new coupling element of microwave slot coupler for designing waveguide slot array which can reduce the effect of undesired higher order mode coupling between coupling and radiating slots in the branch waveguide. The proposed device is composed of a centered longitudinal shunt-series coupling slot at the center of broad wall shared by two crossed rectangular waveguides and an asymmetric compound iris that excites the coupling slot. We first have obtained scattering parameters for the proposed coupler by use of EM S/W tool HFSS and then extracted the parameters of T- network equivalent circuit for the coupling slot. We also have analyzed the resonant properties such as resonant length and normalized admittance by changing the geometrical dimensions. The measured results for the fabricated coupler with short-circuited block <TEX>${\lambda}_g/4$</TEX> away from the coupling slot are well agreed with the simulated ones.

Design of branch line coupler loaded capacitively with interdigitated fingers by using microstrip fed coplanar structures (L-shaped conductor backed asymmetric CPS and U-shaped conductor backed CPW)

In this letter, L-shaped conductor backed asymmetric coplanar stripline (LSCBACPS) and U-shaped conductor backed coplanar waveguide (USCBCPW) branch line coupler fed by microstrip transmission line have been investigated for the miniaturization. The number of interdigital finger unit cells located at the branch and through lines of the conventional branch line coupler is used to provide a desired miniaturization. The proposed branch line couplers in which all ports are formed by microstrip line have been constructed in two different configurations depending on the placement of the capacitively loaded fingers. The effects of the change of the cell number located at the branch and through lines on the center frequency and the propagation velocity are investigated. These effects are expressed by a simple formula depends on the cell number to use in the theoretical model obtained from the even-odd mode analysis of LSCBACPS and USCBCPW configurations. Proposed couplers are designed, fabricated, and tested for the experimental verification to compare with the simulation and theoretical results. Measured, theoretical, and simulation results are in a very good agreement. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:816–820, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27442

Design of Double Y Branch Waveguide in Acceleration Seismic Geophone

Dual M-Z interferometer is the sensitive element of three-component acceleration seismic geophone, while Y branch waveguide is the basic optical components composed of dual M-Z interferometer, so the design of Y branch waveguide directly affects the performance of three-component acceleration seismic geophone. Firstly, branch waveguide and S-shaped bent waveguide are introduced, and symmetrical double Y branch S-shaped bent waveguide is designed based on this. Secondly, the bending loss of the branch waveguide is analyzed and calculated. The transmission of 1/2Y branch waveguide and 1/4Y branch waveguide , and the bending loss changes with the length of 1/2Y branch waveguide and 1/4Y branch waveguide is simulated by MATLAB. The result shows that the maximum bending loss of 1/2 Y branch waveguide is the 0.156dB, and the bending loss is close to 0 after L >320μm; the maximum bending loss of 1/4 Y branch waveguide is 0.058dB, and the bending loss is close to 0 after L >200μm. The design of double Y branch meets the requirement of low loss. Thirdly, the optical power conversion of branch waveguide in 3dB coupler is simulated and analyzed. Finally, proton exchange and Ti diffusion technique are compared; the advantages of proton exchange technology are summarized; the principle of proton exchange is introduced; and a good proton exchange annealing condition is summarized.

Optimization of the Mach–Zehnder modulator using polymer asymmetric rib waveguide

In order to shorten the branch length of Mach–Zehnder modulator, the asymmetric rib waveguide was researched in Mach–Zehnder electro–optic polymer modulator. Full vector finite difference beam propagation method was applied to analyze systematically their transmission loss with different parameters. The structure was optimized by choosing optimal design solution such as the rib width w=4μm, the branch height g=11μm, the outer slab width of core layer in bending waveguide s=2μm and the length of the sine-bending waveguide L1=350μm. The results show that if symmetric rib waveguide is replaced by asymmetric rib waveguide, the length of branch waveguide could be reduced by 30% under the same conditions of transmission loss. The results will have a certain reference value to the design of polymer optical waveguide in M–Z modulator.

Ultracompact 1×4 TM-polarized beam splitter based on photonic crystal surface mode

We provide an improved surface-mode photonic crystal (PhC) T-junction waveguide, combine it with an improved PhC bandgap T-junction waveguide, and then provide an ultracompact 1×4 TM-polarized beam splitter. The energy is split equally into the four output waveguides. The maximal transmission ratio of each output waveguide branch equals 24.7%, and the corresponding total transmission ratio of the ultracompact 1×4 beam splitter equals 98.8%. The normalized frequency of maximal transmission ratio is 0.397(2πc/a), and the bandwidth of the ultracompact 1×4 TM-polarized beam splitter is 0.0106(2πc/a). To the best of our knowledge, this is the first time such a high-efficiency 1×4 beam splitter exploiting the nonradiative surface mode as a guided mode has been proposed. Although we only employed a 1×4 beam splitter, our design can easily be extended to other 1×n beam splitters.

Optimization of T-shaped waveguide branches in two-dimensional photonic crystals

The interval and the radius of a pair of defect dielectric rods in waveguide channels near the branching region of a T-shaped waveguide branches are simultaneously varied, and their effects on the transmission properties are investigated using the finite-difference time-domain (FDTD) method. Numerical results show that there is an optimized region where the relative bandwidth of high-transmission (total transmittance >0.95) band of the branches is larger than 17%, which is higher than that of the existing same structures (11.60%) with fixed interval. These results provide for engineering application of simple T-shaped waveguide branches with high transmission.

Design of T-shaped nanophotonic wire waveguide for optical interconnection in H-tree network

Nanophotonic wire waveguides play an important role for the realization of highly dense integrated photonic circuits. The miniaturization of optoelectronic devices and realization of ultra-small integrated circuits strongly demand compact waveguide branches. T-shaped versions of nanophotonic wires are the first stage of both power splitting and optical-interconnection systems based on guided-wave optics; however, the acute transitions at the waveguide junctions typically induce huge bending losses in terms of radiated modes. Both 2D and 3D finite-difference time-domain methods are employed to monitor the efficient light propagation. By introducing appropriate combinations of dielectric posts around the dielectric-waveguide junctions within the 4.096μm×4.096μm region, we are able to reduce the bending losses dramatically and increase the transmission efficiency from low values of 18% in the absence of the dielectric posts to approximately 49% and 43% in 2D and 3D cases, respectively. These findings may lead to the implementation of such T-junctions in near-future high-density integrated photonics to deliver optical-clock signals via H-tree network.

A simple broadband T-shaped waveguide branch in photonic crystals

A simple broadband T-shaped waveguide branch in photonic crystals is constructed only by introducing three dielectric rods into the waveguide channels near branch region. Numerical results indicate that the bandwidth of high transmission (the total transmittance is larger than 95%) is over 415 nm centered at 1550 nm. Owing to its simple structure and broad enough bandwidth, this waveguide branch is expected to be applied to highly dense photonic integrated circuits.

Low crosstalk waveguide intersections in honeycomb lattice photonic crystals forTM-polarized light

We present the design of a low crosstalk, high throughput waveguide intersection fortransverse-magnetic-polarized light. The design is based on two orthogonal photonic crystalwaveguides and a resonant photonic crystal cavity in honeycomb lattice geometry. Theresults of our numerical simulation validate the concept of the design and demonstrate acrosstalk smaller than 0.1% and throughput transmission of more than 80% for bothorthogonal waveguide branches.

Compact Orthomode Transducer Using Single-Ridged Triangular Waveguides

We present a compact L-band orthomode transducer (OMT) with a new waveguide junction consisting of a quad-ridged square waveguide and four single-ridged triangular waveguides. Quad-ridged square and single-ridged triangular waveguides of various sizes were numerically analyzed to estimate the cutoff frequencies and characteristic impedances of the waveguides. An optimum junction structure for the OMT with a low cutoff frequency and specific characteristic impedance was found based on the numerical simulation. The junction has a relatively small size without waveguide branches, and provides good impedance matching with a 50 Ω coaxial feed line. In addition, Klopfenstein and linear tapers were employed to design waveguide ridges for minimizing mismatches at the OMT junction. Measurement showed a bandwidth of about 400 MHz from 1.0 to 1.4 GHz and an isolation level below -40 dB in the frequency range. The cross section of the OMT was reduced to 62% of the standard waveguide cross section, and the total length is only 56 cm (2.24 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) at 1.2 GHz.

Design of surface mode photonic crystal T-junction waveguide using coupled-mode theory

We design a photonic crystal T-junction waveguide on the basis of the nonradiative surface mode and further optimize the transmission ratio of our surface mode photonic crystal T-junction waveguide with the guide of coupled-mode theory. Compared with a traditional bandgap photonic crystal T-junction waveguide, our surface mode T-junction waveguide can obtain almost zero reflectance and good transmission. Better still, its size is just half of the size of bandgap photonic crystal waveguide branches. To the best of our knowledge, it is the first time that such a high-efficiency T-junction waveguide that uses the surface mode as the guided mode is proposed.

Design of a Planar Slotted Waveguide Array Antenna for X-band Radar Applications

A planar slotted waveguide array antenna has been designed at 9.37 GHz for X-band radar applications. The antenna consists of multiple branchline waveguides with broadwall radiating shunt slots and a main waveguide to feed the branch waveguides through a series of inclined coupling slots. The antenna feed point is located at the center of the main waveguide. Element weights in the array have been calculated bysampling a continuous circular Taylor aperture distribution at the 25 dB sidelobe level in both the E and Hplanes. A commercially available electromagnetic (EM) simulation tool has been used to characterize the individual isolated slot and that data hassubsequently been used to design the planar array. The array is finally analyzed in a CST Microwave studio and the measured and simulated results have been found to be in good agreement.

Novel Triplexer Chip Design Combination of an Asymmetric Y Branch Waveguide and a Multimode Interference

A novel triplexer chip based on an asymmetric Y branch waveguide and a multimode interference is presented in this paper. Using the novel triplexer chip, a 1310nm channel is multiplexed and 1490nm and 1550nm channels are demultiplexed for FTTH using. The asymmetric Y branch waveguide is used to separate the 1310nm channel from the 1490nm and 1550nm channels. Then the multimode interference is used to demultiplex the 1490nm from 1550nm channel. The simulated spectra show the bandwidths of three response wavelengths are 100nm, 20nm and 10nm, respectively, which can meet the demand of ITU.984 completely. The isolation for 1310nm is more than 48dB, and the isolation between 1490nm and 1550nm is more than 37dB.

Polarization-Splitting Waveguide Devices Incorporating Perfluorinated Birefringent Polymers

Low-loss perfluorinated polymers with a controllable optical birefringence were synthesized for the purpose of fabricating polarization-splitting waveguide devices, which have become an essential part of polarization-multiplexed coherent optical communications. The birefringent polymer was embedded on one branch of the asymmetric Y-branch waveguide to produce polarization-dependent mode evolution due to the effective birefringence. The device with a branch angle of 1/300 rad and birefringence of 0.007 showed a crosstalk of -25 dB and an insertion loss of 1.5 dB from fiber to fiber. The polarization splitters based on adiabatic mode evolution exhibited negligible wavelength dependence and large tolerance in waveguide dimension.

Engineering the light propagating features through the two-dimensional coupled-cavity photonic crystal waveguides

This paper studies the propagating characteristics of the electromagnetic waves through the coupled-resonator optical waveguides based on the two-dimensional square-lattice photonic crystals by the finite-difference time-domain method. When the traditional circular rods adjacent to the centre of the cavities are replaced by the oval rods, the simulated results show that the waveguide mode region can be adjusted only by the alteration of the oval rods' obliquity. When the obliquity of the oval rods around one cavity is different from the obliquity of that around the adjacent cavities, the group velocities of the waveguide modes can be greatly reduced and the information of different frequencies can be shared and chosen at the same time by the waveguide branches with different structures. If the obliquities of the oval rods around two adjacent cavities are equal and they alternate between two values, the group velocities can be further reduced and a maximum value of 0.0008c (c is the light velocity in vacuum) can be acquired.

Optimization design of optical waveguide in Mach-Zehnder electro-optical polymer modulator

In order to reduce transmission loss of the optical waveguide in Mach-Zehnder (M-Z) electro-optical (EO) polymer modulator, the basic iterative formula of semi-vector finite-difference beam propagation method (FD-BPM) is obtained from the scalar wave equation. The transition waveguide is combined with S-type bend branch waveguide for the M-Z EO modulator in the branch waveguide. The effects of structure parameters such as ridge width, length of the branch waveguide and interferometer spacing on the transmission loss are systematically studied by using the semi-vector FD-BPM method. The structure is optimized as an S-sine bend branch waveguide, with rib width w=7 μm, length of branch waveguide L=1200 μm and interferometer spacing G=22 μm. The results show that the optimized structure can reduce transmission loss to 0.083 dB, which have a certain reference value to the design of optical waveguide in M-Z polymer modulator.

光纤到户用单纤三向复用器芯片的研究

A triplexer was fabricated based on asymmetric Y branch waveguides Cascade Multimode interference(MMI) for fiber to the home(FTTH).The simulation results of spectral response show that output optical fields are clearly.And the demultiplexing function for download 1 490 nm and 1 550 nm and multiplexing function for upload 1 310 nm were achieved.The simulation results of finited different beam propagation method(FD-BPM) show that insertion loss is less than 1.49 dB;the bandwidths of three response wavelengths meet the demand of ITU.984 completely;the isolation for 1 310 nm is more than 47 dB;the isolation for between 1 490 nm and 1 550 nm is more than 29 dB.

COMPACT AND HIGH PERFORMANCE STEPPED TRUNCATED-CIRCULAR WAVEGUIDE BRANCHING ORTHO-MODE TRANSDUCER (STCWB-OMT)

This paper reports design and development of an innovative compact Stepped Truncated-Circular Waveguide Branching Ortho-Mode Transducer (STCWB-OMT) operating at 4.5{4.8GHz for horizontal and vertical polarizations. STCWB-OMT is derived by introducing branch waveguide via coupling slot on a stepped truncated- circular waveguide. This conflguration possesses inbuilt rectangular- to-circular transition; therefore it does not require any additional square-to-circular transition to combine it with horn antenna. The challenge in the design incorporated is to obtain a mechanically compact design with low mass while compliant with the specifled electrical performances; since this device is developed for space-borne application. Achieved return losses at both direct and coupled ports are > 17dB, insertion losses 40dB with the OMT length = 1:98‚ at center frequency and weight = 250gm The agreement between measured and computed results provides a validation of the proposed OMT conflguration.

Si wire waveguide wavelength filter using asymmetric width waveguide branch coupler and Bragg grating

The design for a Si wire waveguide wavelength filter using Bragg grating and a coupler composed of branching asymmetric width waveguides is reported. The coupler is tolerant against waveguide width deviation and shows wide working wavelength range. The device is designed for optical network units used in fibre to the home systems.