Simplified Linear Configuration Model of 3X3 Single Mode Fiber Coupler using Matrix Transfer

In this paper, the performance analysis on hybrid plasmonic waveguide (HPW)-based symmetrical directional coupler (DC) is proposed, which contains two parallel arms. In this analysis, one HPW arm performs as an input port and bar (parallel) output port; another HPW arm doings as a cross output port. The principle of DC is satisfied by the coupling of transverse magnetic field (TM) from the bar port to cross port. In the proposed DC, the mode characteristic parameters such as normalized mode area and propagation length are calculated by finite element method (FEM), and performance of the device is analyzed by certain parameters such as propagation loss, cross-talk, insertion loss, and coupling ratio. Hence, the proposed DC is designed with low cross-talk, low insertion loss, low propagation loss, and high propagation length, which could be appropriate for ultra-dense photonic integrated circuits (PICs).KeywordsOptical waveguidesDirectional couplerFinite element method

Soliton propagation in a directional fiber coupler is investigated. By using Fourier series analysis technique (FSAT), the effects of radii ratio and intermodal dispersion on soliton switching have been investigated.

An analysis of four-arm symmetrical networks such as a branched directional double stub coupler or the hybrid ring (rat race) is presented. The input wave is broken into an even and an odd mode and the vector amplitude out the various arms is computed from the sums or differences of the reflection or transmission coefficients for the two modes. A zero decibel directional coupler is described and its possible use as a duplexer is proposed. The design of multiple stub directional couplers for any degree of coupling is discussed. A method of computing the bandwidth of all these couplers is outlined, and the bandwidth curves, the power out the various arms with respect to frequency of the zero decibel coupler, are computed. A tabulation is made for six different 3 db couplers (even-power split) and their standing wave ratio, evenness of power split and isolation of the fourth arm as a function of frequency assuming perfect performance at the band center.

Fiber directional couplers made of highly asymmetric twin-cores (ATC), one of which is doped with erbium, are designed to achieve an inherently gain flattened erbium doped fiber amplifier (EDFA). The refractive index profiles of the fibers as well as the spacing between the two cores were carefully designed to achieve a targeted gain with low gain excursions across the C-band. One of the designs yielded a theoretical median gain ~ 38 dB with an excursion within ±1 dB. In order to suite fabrication of such an inherently gain flattened EDFA by the MCVD fiber preform fabrication process, the design had to be modified and a more modest target of about 20 dB was set with excursion below ± 1.5 dB for metro-centric applications. It involved preparation of two independent preforms, which required selective polishing of the cladding from one side by a certain amount to meet the required nominal separation between the two cores set at the design stage of the fiber. Several intricate operations were required to implement the fiber drawing step from the two assembled preforms. Preliminary characterization of the fabricated fiber shows filtering of ASE peak through selective wavelength coupling from Er-doped core to un-doped core.

Fiber directional couplers made of highly asymmetric twin-cores (ATC), one of which is doped with erbium, are designed to achieve an inherently gain flattened erbium doped fiber amplifier (EDFA). The refractive index profiles of the fibers as well as the spacing between the two cores were carefully designed to achieve a targeted gain with low gain excursions across the C-band. One of the designs yielded a theoretical median gain ~ 38 dB with an excursion within ±1 dB. In order to suite fabrication of such an inherently gain flattened EDFA by the MCVD fiber preform fabrication process, the design had to be modified and a more modest target of about 20 dB was set with excursion below ± 1.5 dB for metro-centric applications. It involved preparation of two independent preforms, which required selective polishing of the cladding from one side by a certain amount to meet the required nominal separation between the two cores set at the design stage of the fiber. Several intricate operations were required to implement the fiber drawing step from the two assembled preforms. Preliminary characterization of the fabricated fiber shows filtering of ASE peak through selective wavelength coupling from Er-doped core to un-doped core.

As one of the key component of photonic crystal optical circuit devices, the directional coupler is investigated. We explain the reason the directional coupler consisting of an ordinary symmetric parallel waveguide cannot have a high extinction ratio and a small coupling length simultaneously. To realize both characteristics simultaneously, we propose a novel directional coupler structure. By numerical calculation, we show the possibility of a directional coupler with a high extinction ratio (-24 dB) and a small coupling length (18a).

Single-mode integrated-optic directional couplers on electro-optic substrates can be used to realize photonic space-division multiplexers/switches with low cross-talk level and switching voltage. This paper describes briefly the methods which have been used by the present authors to design 2x2 and 4x4 switch matrices oir LiNbO3 substrates. A computer-aided analytical model has been developed to obtain the two-dimensional distribution of Ti-concentration and refractive index profiles for arbitrary waveguide geometry, Ti-film thickness and processing conditions. The matrix method which is a simple analytical tool for layered structures has been employed to study the wave propagation through Ti indiffused LiNb03 waveguides and directional couplers. The data for refractive index profile required as the input for running the computer program implementing the matrix method were obtained from the above computer-aided analysis. The computed results of Ti-concentration, refractive index profiles and the critical coupling length of directional couplers were validated with available experimental data. Due attention has also been paid to reduce the radiation loss from waveguide bends and to incorporate the polarization dependence in the design of directional couplers. The electrode structure and its placement on Ti:LiNb03 waveguides have been optimized for a 5V switching voltage. The effects of buffer layer and I/O fiber-to-waveguide coupling have also been considered to estimate the total loss. Necessary data generation in appropriate format for electron beam masks for Ti-waveguides and electrode patterns has been completed, and the fabrication of masks is now in progress. A simplistic design of 8x8 switch matrix has also been included.

Wideband directional couplers are among the microwave components extensively used in electronic warfare, electronic countermeasures, and instrumentation. In this paper, a simple straight line coupling function is used to design a high-pass directional coupler. The ripple performance of a coupler using the linear coupling function is shown to be superior to couplers designed using the cosine type coupling function as reported in (5). In addition, the straight line coupling function is easier to visualize and implement in the design of directional couplers. Other coupling functions such as the Cos type (6) coupling variation provide further reductions in ripple level, but with added mathematical and process complexities.

In this work we present the study of step-index channel directional couplers which can be fabricated on a buffer planar guide in a such a way that they can be properly designed to support separable modal fields, though the index profile is non separable. The main advantage of this approach is the great simplicity in the analysis, design and fabrication of the directional couplers, or other different integrated strucutures, since it is possible to apply, for instance, the effective index method obtaining a quasi-exact solution for the modal fields. Analytical and numerical results will be presented to confirm that an accurate design of the operation properties of the directional coupler can be achieved.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A novel compact easy-to-manufacture design of 20 dB directional coupler has been proposed for a high power operation within frequency band 4-12GHz. In order to obtain the broadband frequency response a three-section asymmetric coupled strip-line directional coupler has been chosen. The periodic structures are introduced on the outer edges of coupled strip-lines to improve directivity and isolation of coupler. The successfully fabricated and tested coupler shows high electrical performances. The proposed 20 dB directional coupler provides within frequency band 4-12 GHz the coupling characteristic imbalance 0.5 dB, isolation 35 dB, directivity 15 dB and VSWR <; 1.35. The allowable input power of directional coupler is up to 100 W. The coupler dimensions are 39 × 35 × 26 mm.

Design method of novel multilayer, broadband six port microstrip directional coupler at VHF- UHF range for high power applications is given. Directional coupler is modeled and simulated with the method of moments based planar electromagnetic simulator on a two-layer Alumina substrate. It is shown that the high directivity and desired coupling level of the directional coupler are maintained within 300MHz of bandwidth using the proposed design method in this paper. Results of this work can be used in the design of broadband directional couplers for high power RF/Microwave applications.

This paper reports a new design of microstrip directional coupler with high directivity. This directional coupler uses corrugated coupled lines and floating conductor in the ground plane of microstrip to enhance coupling. Based on this structure, directional coupler having 4.4% bandwidth has been designed at 4500 MHz with 10 dB coupling and 35 dB directivity. The designed directional coupler has been fabricated and tested for the validity of the design. Measured results are presented in this paper.

As a kind of optical comb filter, double-ring resonator formed by a 3 x 3 fiber directional coupler can be used in optical communication system. By changing the parameters such as the coupling angle of the directional coupler, physical lengths ofthe double rings, loss, and gain factors. It behaves like a device with multi-function involving multichannel band-pass and band-stop filter, laser resonator or amplifier, optical all-pass filter and so on. In this paper, characteristics of double ring resonator formed by an equal triangle 3 x 3 fiber directional coupler is numerically analyzed in detail, for the double-ring resonator with equal lengths, a minor peak appears near every main resonant peak, they change in reverse dynamically with the increase of the gain coefficient for fixed loss. For unequal lengths case, active cavity brings about clear Vemier effect, and free spectral range (FSR) is increased. At last, applications of this component in the construction of flattop interleaver and dispersion compensator in FDM system are discussed.

Directional couplers based on antiresonant reflecting optical waveguides (ARROW) have been fabricated and tested. The exchange of power from one waveguide to the other could be well controlled by adjustment of geometrical parameters such as the coupling length and/or the etch depth of the rib ARROW waveguide. Simulations based on the beam propagation method yield good agreement with measurement data and has been found to be indispensable for accurate design and analysis of ARROW directional couplers. Owing to the ARROW structure, the directional couplers presented have the feature that they also perform the polarizing function.

This paper describes a design of microstrip rectangular disk quadrature directional couplers on the basis of a modified eigenfunction expansion method with consideration of frequency dependences of an effective width and an effective relative permittivity of a microstrip disk circuit. Using this approximate method, we can optimize the disk configuration of directional couplers in a reasonable computational time. The validity of the design method is examined by comparison with the numerical results by the FDTD method.