1,720,964 research outputs found
Fibre-taper devices
No full textIn this paper I will review recent work at Southampton on tapered single mode optical fibre devices. In particular I will describe our recent work on single mode beam expanders and fused fibre couplers. It is well known that a gap of up to 100 µm in a single mode fibre results in about 1dB loss. By tapering the fibre so that the field expands into an LP cladding mode with increased spot size it is possible to introduce a larger gap of about one mm. This will allow the insertion of small electro-optic devices, such as a liquid crystal cell. By overjacketing the fibre with a silica capillary, or combination of Vycor and silica capillaries it should be possible to achieve a beam diameter of several hundred microns. This would allow a gap of about 1 cm and this would allow the insertion of a very wide range of optical devices, such as acousto optic modulators. Considerable progress has been made recently in the fabrication and analysis of long fused-taper 4-port directional couplers. This has resulted in several important devices, including polarization beam splitters, wavelength division multiplexers, optical fibre filters, and wavelength selective ring resonator
Crosstalk in polarisation-maintaining fibres
No full textWe show that internal geometric imperfections have a negligible effect on polarisation cross-talk in a birefringent fibre. This is contrary to popular opinion and has considerable implications for the way in which polarisation maintaining fibres are specified
Polarisation analysis of strongly fused and weakly fused tapered couplers
No full textThe 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
Modelling fused single-mode fibre couplers
No full textThe fused single mode tapered coupler is successfully modelled by assuming that the neck section of the coupler can be represented by a rectangular dielectric waveguide. Guidance is provided at the glass to air (or external medium) boundary and the cores are neglected. The mechanism of field detachment from the cores is outlined and the coupler characteristics are derived from the interference between the two lowest order modes of the large waveguide
Practical single-mode fibre-horn beam expander
No full textA new design and implementation technique for the single-mode fibre-horn beam expander is outlined. This new design is more practical, both in its fabrication technique and in its application, than the previous approach. The field evolution along the beam expander has been measured and the fundamental limits to the rate of tapering examined
The behaviour of single-mode taper and its gap-device application
No full textBeam expanders are required for in-line fibre devices such as connectors and power splitters. Such expansion has generally relied on a lens to achieve the necessary beam size. In this letter we demonstrate a rugged alternative approach which is based on the expansion of the field when a monomode fibre is tapered
Tapered-beam expander for single-mode optical-fibre gap devices
No full textA simple practical and controllable beam expander can be constructed from a single-mode optical fibre which has been overjacketed in a capillary of lower refractive index and then tapered. The properties of such an expanded beam in a gap device are also investigated
Dependence of fused taper couplers on external refractive index
No full textWe present the results of an experimental and theoretical investigation into the dependence of fused taper couplers on changes in the external refractive index. We show that it should be possible to fabricate long couplers which are insensitive to changes in the external refractive index
Gain equalization of a six-mode-group ring core multimode EDFA
No full textWe propose a 6-mode-group ring core multimode erbium doped fiber amplifier (RC-MMEDFA) capable of providing almost identical gain among the six mode groups within the C band using either core- or cladding-pumped implementations
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