Ian Bassett

Microstructured polymer optical fibre

The first microstructured polymer optical fibre is described. Both experimental and theoretical evidence is presented to establish that the fibre is effectively single moded at optical wavelengths. Polymer-based microstructured optical fibres offer key advantages over both conventional polymer optical fibres and glass microstructured fibres. The low-cost manufacturability and the chemical flexibility of the polymers provide great potential for applications in data communication networks and for the development of a range of new polymer-based fibre-optic components.

Ring structures in microstructured polymer optical fibres

Recent developments in polymer microstructured optical fibres allow for the realisation of microstructures in fibres that would be problematic to fabricate using glass-based capillary stacking. We present one class of such structures, where the holes lie on circular rings. A fibre of this type is fabricated and shown to be single moded for relatively long lengths of fibre, whereas shorter lengths are multimoded. An average index model for these fibres is developed. Comparison of its predictions to the calculated properties of the exact structure indicates that the ring structures emulate homogeneous rings of lower refractive index resulting in the ring structured fibres behaving approximately as cylindrically layered fibres.

Recent progress in microstructured polymer optical fibre fabrication and characterisation

Recent progress in microstructured polymer optical fibre fabrication and characterisation will be presented. A wide range of different optical functionalities can now be obtained by modifications of the microstructure, as is demonstrated by the fibres presented here. Microstructured fibres that are single-mode, highly birefringent or show twin-core coupling are described, in addition to graded-index microstructured fibres and hollow core fibres, the latter case being where light is guided in an air core. Microstructured polymer optical fibres are an exciting new development, offering opportunities to develop fibres for a wide range of applications in telecommunications and optical sensing.

Elimination of polarization degeneracy in round waveguides

We show how to design a round optical fiber so that it is effectively single moded, with no polarization degeneracy. Such fibers would be free from the consequences of polarization degeneracy or near degeneracy - phenomena such as polarization fading in interferometry, and polarization mode dispersion - and so may offer an alternative to polarization maintaining fibers for the avoidance of these phenomena. The design presented builds on an earlier observation of polarization selective refection in Bragg fibers.

Microstructured optical fiber for single-polarization air guidance

An air-core microstructured fiber design that supports a single-polarization, circularly symmetric nondegenerate mode is presented. The fiber design is modeled directly, and the microstructured cladding is analyzed by use of band diagrams to elucidate the mechanism through which polarization nondegeneracy is achieved.

Electric field and voltage sensing using thermally poled silica fibre with a simple low coherence interferometer

The polarization dependence of the linear electro-optic effect in poled silica is used to measure electric fields applied transversely across the fibre core using a simple low coherence interferometer. The path imbalance arising through the inherent birefringence of the poled fibre is modulated by the applied electric field. The interferometer produces a spectral modulation, or interferogram, imposed on the background spectrum of the broadband light source used to illuminate the sensor. The interferograms are then recorded using a spectrometer and the small optical path imbalance is calculated by processing the interferogram in a computer using Fourier transforms. Experimental results for linearity, and an analysis of the methods used are presented.

Analysis of ring-structured Bragg fibres for single TE mode guidance

Ring-structured Bragg fibres that support a single TE-polarisation mode are investigated. The fibre designs consist of a hollow core and rings of holes concentric with the core, which form the low-index layers of the Bragg reflector in the cladding. The effects of varying the air fraction in each ring of holes on the transmission properties of the fibres are analysed and an approximate model based on homogenisation is explored. Surface modes and transitions thereof are also discussed.

Application of the NIMI technique to the 3/spl times/3 Sagnac fibre optic current sensor - experimental results

The NIMI technique has been proposed as a means to stabilize and improve the performance of the passive 3x3 Sagnac fibre optic current sensor. This paper reviews, and presents results of, the experiments carried out to investigate the performance of the NIMI technique.

A depolarized Er-doped superfluorescent fibre source with a 3-section Lyot fibre depolarizer

A 3-section Lyot fibre depolarizer was used to substantially reduce the degree of polarization of an Er-doped superfluorescent fibre source. The residual degree of polarization of this improved Er-doped superfluorescent fibre source is found to be 0.05% (−33 dB).

Lab Trials of an Electricity Transmission Line Voltage Sensor Based on Thermally Poled Silica Fibre

Voltage sensing using helically coiled lengths of thermally poled twin-hole silica optical fibre is presented. Lab accuracy test results showing good linearity and signal to noise performance are presented.