Adiabatic fused tapered couplers

Pre-fattening of one fibre is shown to be a vehicle for achieving wavelength independent adiabatic fused tapered couplers. Compared with the conventional pre-tapered fused tapered coupler, this adiabatic coupler has a significant improvement in its ease of manufacture     

Power exchange in tapered optical couplers

The power exchange between nonparallel optical waveguides or tapered couplers is analyzed by the coupled-mode theory based on local modes of the individual waveguides (local waveguide modes). A self-consistent nonorthogonal coupled-mode formulation is presented and transformed into an orthogonal form which is equivalent to the coupled-mode equations for the local modes of the coupled waveguides (local array modes). The coupled-mode equations are then solved numerically and the effect of the taper on the power exchange between the two guides is studied     

Optical wavelength filter with tapered couplers

Optical wavelength filters based on tapered directional couplers are analyzed by nonorthogonal coupled-mode theory. The nonorthogonal coupled-mode formulation in general yields more accurate results than the conventional orthogonal coupled-mode theory. The focus is on the novel features of the tapered couplers used as wavelength filters. It is demonstrated that, in addition to reducing the crosstalk and suppressing the sidelobes, the tapered structure can also make the filtering response independent of the device length beyond a critical coupling length,.<>     

Variational analysis of fused tapered couplers

A variational technique is used to evaluate the coupling ratio of a fused coupler. The technique can be used for both strongly and lightly fused couplers. Simple formulas are presented for use in regions of high V-value and are shown to be in agreement with the more lengthy beam propagation calculations. The importance of the fibre core in determining the field shape is highlighted. A realistic coupler model containing a gradual taper is presented and the strong wavelength response of the coupling ratio is confirmed by numerical means.     

Fabrication of wavelength-flattened tapered couplers usingpolishing for cladding removal

Wavelength-flattened fused tapered couplers have been fabricated with low loss using a new technique. The asymmetry between the constituent fibres is induced by the rapid removal of a small amount of the cladding of one of the fibres with a polishing wheel     

Perturbation analysis of fused tapered single-mode fibre couplers

By treating a fused tapered single-mode fibre coupler as a perturbation of the same coupler with the fibre cores ignored, simple analytical expressions are derived for the coupling coefficients of the coupler. These new expressions highlight the effects of the fibre cores on the characteristics of the coupler.     

Star couplers using fused biconically tapered multimode fibres

We report the fabrication and testing of 4-, 7-and 19-fibre fused biconical taper transmissive star couplers for use with single multimode fibres. Overall insertion losses on six couplers range from ?1.3 dB to ?2.6 dB. Losses are nearly independent of N, the number of fibres, but dispersion of the powers in the output fibres increases significantly with N.     

Fabrication of tapered couplers in GaAs/GaAlAs rib waveguides

Tapered couplers have been fabricated in GaAs/GaAlAs single-mode rib waveguides. A new etching technique has been used to fabricate transitions of 1 μm over lengths of approximately 160 to 300 μm. Losses for the TE and TM fundamental modes have been measured at a wavelength of 1.3 μm     

Polarisation analysis of strongly fused and weakly fused tapered couplers

The polarisation properties of both strongly fused and weakly fused single-mode tapered fibre couplers have been analysed. A comparison with experimental results shows excellent agreement with our analysis.     

Variable-ratio, polarisation-insensitive, 3*3 fused biconical tapered couplers

The authors present a polarisation-insensitive, 3*3 fused biconical tapered coupler with a variable screw gauge that can change the coupling ratios from a splitting percentage of 11%-44%-45% to a uniformity of 33%-33%-34%, with excess loss maintained below 1.1 dB. The fabrication and packaging methods are described and wavelength tunability of the coupler is demonstrated.<>     

Completely fused tapered couplers: comparison of theoretical and experimental results

Completely fused single-mode fibre couplers, characterised by an almost circular cross-section at the waist, have been fabricated. An analytic model which takes into consideration the taper and variable aspect ratio of the coupler has been developed. Good agreement is obtained between the theoretical and experimental values.     

All-silica double-pass StCtL band EDFA

The possibility to extend the erbium-doped fibre amplifier bandwidth from S- to L-band through all-silica erbium-doped fibres has been experimentally demonstrated. An amplifier with a parallel configuration for the S-, C- and L-bands and a double-pass scheme is proposed. The amplifier exploits the depressed-cladding fibre bending loss to obtain amplification in S-band     

硅基槽波导级联多模干涉耦合器型偏振分束器

提出了一种基于硅基槽波导的级联多模干涉(MMI)耦合器型偏振分束器,由锥形及矩形结构MMI耦合器构成.级联结构使器件长度无需为两偏振模自镜像长度的公倍数,不仅能有效减小器件尺寸,而且提高设计灵活性.同时,利用槽波导的高双折射特性及MMI耦合器的锥形结构,可进一步缩短器件尺寸.分析结果表明,所提器件能够有效实现偏振束分离,两级MMI工作区总长度仅为42μm,准TE与准TM模的偏振消光比分别为29.8和31.4d B,1.55μm波长下的插入损耗分别为0.395和0.699 d B,偏振消光比大于20 d B时光带宽为43 nm,覆盖整个C波段.最后,详细分析了器件关键参数的制造误差对器件性能的影响.     

A generalized theory of tapered transmission line matchingtransformers and asymmetric couplers supporting non-TEM modes

A general Fourier transform pair for the analysis and synthesis of tapered transmission lines supporting a non-TEM (transverse electromagnetic) mode is presented. The Fourier transform pair first pointed out by F. Bolinder (1950) for TEM lines is shown to be a special case of the present transform pair. The transform pair is mathematically rigorous and simple enough to implement on a desktop computer for the design of dispersive transmission line tapers. A step-by-step synthesis method is described for exact designs of matching transformers and asymmetric couplers. The theory is verified with the design of two Ka-band finline tapers and a C-band microstrip coupler     

Helix couplers for linear-beam devices

In this paper the interaction between electron beams and coupled helices is studied and generalized to include the effects of 1) space chargeQC; 2) finite circuit lossd; 3) finite values of gain parameterC; 4) an unrestricted coupling parameterk, and 5) the effect of having a large positive value of the velocity parameterbsuch that the propagation constants are purely imaginary. A general determinantal equation including all these factors is derived from the coupled-circuit equations and the stream equation. Curves of the propagation constants for a variety of operating parameters are shown. Attention is called to the fact that a region of growing wave is found for large positivebfor extremely tight coupling. The extent to which the "growing-wave island" is affected by the various operating parameters is also illustrated. Equations for the outer and inner helixr-fvoltages are derived and from which curves of the propagatingr-fpowers along the helices are computed and plotted. Positions for maximum transfer of energy between the helices can be deduced and the extent to which they are affected by the various Parameters is discussed.     

Milled-groove method for fiber-to-waveguide couplers

We report a simple milled-groove process integrated with a two-step ion-diffused waveguide fabrication for efficient coupling between single-mode fibers and integrated optical waveguides andY- branches. We demonstrate such a coupling technique using a) a multimode transition to single-mode waveguide coupler, and b) an integrated optical 3-dB branching waveguide coupler from a single-mode fiber to silver/sodium ion-enchanged waveguide components. The coupling loss was about 1-2 dB over a propagation length of 2 cm at an operating wavelength of 633 nm.     

Finite-element analysis for fused couplers

By using the finite-element method we show that the polarisation beam splitting property of realistic fused optical couplers is well modelled by an elliptical cross-section, but differs substantially from a rectangular cross-section.     

Ultra-thin pocket embedding package for system in package

Proposed is a new type of packaging technology, `pocket embedding package', using selectively anodised aluminium substrate. In this technology, chips can be embedded inside aluminium substrate so that an ultra-thin and compact type of package can be achieved. A monolithic microwave integrated circuit dice with 120 mum thickness has been successfully embedded inside the substrate with a tolerance of less than 5 mum, and 300 mum of total thickness can be achieved with excellent thermal dissipation     

Design data for interdigital directional couplers

The letter presents graphical information relating the performance of interdigital microstrip directional couplers to the geometrical parameters of the circuit. The theoretical background is summarised, and a comparison is made with reported experimental results.     

Small-hole couplers

A proof is provided of the fact that the formulas for the coupling due to a small hole, obtained by Bethe, correctly apply even to structures which do not exhibit the symmetry, in the plane of the hole, postulated by Bathe.