1,720,984 research outputs found
An all-fibre polarising beamsplitter
No full textThe first fibre equivalent of a polarising beamsplitter is reported. The device is based on a fused-taper fibre coupler. Separation of the orthogonally polarised components of the input light can be accomplished to better than 17 dB
Thermal stress measurements in optical fibre preforms using preform profiling techniques
No full textAn analysis is presented of the effect of thermal stress on transverse refractive-index profiling of optical-fibre preforms. The theory leads to a new measurement technique for axial stress profiling
Fundamental limits to the transmission of linearly-polarised light by birefringent optical fibres
No full textExperimental results are presented which show that the fundamental mode in highly birefringent fibres is not plane-polarised, as is normally assumed, but has significant orthogonal field components. These components limit the maximum measurable polarisation intensity extinction ratio to ~40 dB. Implications for polarisation measurements and fibre gyros are outlined
All fibre wavelength filters using concatenated fused-taper couplers
No full textSuccessive fused-taper couplers are proposed as all-fibre wavelength filters. A low-loss narrowband filter constructed from two overcoupled couplers is demonstrated
Fabrication of polarisation-maintaining fibres using gas-phase etching
No full textA new fabrication technique for the production of high-birefringence fibres is described. The process is shown to produce fibres with a cross-sectional geometry which is close to the optimum predicted by stress analysis. As a result, fibres with extremely short beat lengths (0.55 mm at a wavelength of 633 nm) have been produced
Polarisation characteristics of fibres for coherent detection systems
No full textCoherent transmission systems utilising the optical heterodyning principle require a stable polarisation state for both the local oscillator and incoming signal waves. For a fixed input state the output polarisation of a single-mode fibre in general varies according to the prevailing environmental conditions. Efficient heterodyning can be obtained only by stabilising the output state. This may be accomplished by either (i) designing the fibre polarisation properties to be intrinsically immune to the environment, or (ii) by actively controlling the output to maintain the required state of polarisation at the detector. In this paper the design, manufacture and properties of fibres suited to both these approaches will be considered
Finite cladding effects in highly-birefringent fibre taper polarisers
No full textExperimental results show that the refractive index of the outside medium affects the performance of fibre polarisers made by tapering high-birefringent bow-tie fibres. Both narrowband and wideband polarisers have been constructed having extinction ratios of 35 and 26 dB, respectively
Three-dimensional stress profiling of highly birefringent optical-fibre preforms
No full textIn the fabrication of highly-birefrinqent, e.g. "Bow-Tie", optical-fibre it is required to maximise the stress, and hence the birefringence, within the core of the preform. Conversely, the stresses in other regions of the preform should be minimised to prevent the preforms shattering. This is particularly true for the so-called 'Stress-Guide' preforms in which the refractive index difference in the core is obtained by using the stress-optic effect, rather than by the more usual method of incorporatinq a dopant. The ability to measure the stress distribution within such preforms would therefore be extremely useful
Helical-core circularly-birefringent fibres
No full textA new type of circularly-birefringent fibre is demonstrated based on the optical rotation which occurs in a helical core fibre. The birefringence is an order of magnitude higher than that obtained with previous fibres
Endface index profiling of optical fibre preforms
No full textA new method of obtaining the refractive-index profile of an optical fiber preform is described. The technique is based on the refraction of light emerging from an endface cut normal to the preform axis. Two forms have been developed. In one, quantitative index data are obtained by a spatial-filtering method. The result is displayed as a 3-D graphic plot. The other uses a new type of spatial modulation which permits a direct display of the 3-D index profile in the form of a visual image
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