Fibre bundle comprising nineteen optical fibres drawn from the double crucible

A new technique of simultaneously drawing nineteen optical fibres from a double crucible is presented. Rotation of the crucible around its axis allows the fibres to be stranded during the drawing process. The fibres coated in-line with a silicone resin showed good cross-sectional symmetry and optical losses similar to those obtained in the single-fibre drawing process.     

Chirped gratings produced in photosensitive optical fibres by fibredeformation during exposure

A technique for writing chirped-period gratings by UV holographic exposure in photosensitive optical fibres is reported. Results are presented for gratings produced in boron-germania codoped fibres, hydrogen-loaded high-germania fibres, and hydrogen-loaded standard telecommunications fibres, with performance parameters ranging from 99% reflectivity with 7.5 nm bandwidth, to ~5% reflectivity over >17 nm bandwidth     

Technique for jointing small-core optical fibres

A simple technique for making permanent joints between optical fibres is described. The technique is suitable for small-core fibres, as well as those in which the core is not well centred in the cladding. Because the precision components required to make the alignment are reused, the cost per joint is low.     

Optical tap array using distributed-index planar microlens

The letter describes a novel optical tap array by using a two-dimensional array of planar microlenses. The present device is used to monitor a part of light which is transmitted through optical fibres. Planar microlenses to focus the light have been monolithically fabricated by the use of the electromigration technique; the focal length is 3 mm and NA is 0.15. The coupling efficiency of the initial device was 52% for coupling multimode graded-index fibres.     

1 × n optical fibre switch

A variety of techniques to realise optical fibre switching using multimode fibres have been reported in the literature. Most of these techniques, however, either exhibit high insertion losses or are limited in switching configurations to 1 × 2 or 2 × 2 structures. In the letter we report a mechanical 1 × 8 optical fibre switch with maximum insertion losses of 1 dB with 50 ?m-core fibres. The switching technique described is suitable for expansion into larger 1 × n configurations.     

Photosensitivity measurement in optical fibre with Bragg grating interferometers

A new technique based on two low-finesse fibre Bragg grating Fabry-Perot interferometers to study photosensitivity in optical fibre is presented. Phase evaluation using the Fourier spectra allows precise determination of the evolution of the refractive index with accumulated fluence. Results are given for different germanium/boron codoped fibres and for hydrogen-loaded fibres.     

Self-aligned flip-chip packaging of tilted semiconductor opticalamplifier arrays on Si motherboard

An optical self-aligned flip-chip packaging technique for tilted semiconductor optical amplifier arrays is reported. It uses a Si motherboard with V-grooves for self-alignment between the tilted SOA array and angle polished fibre arrays. Fibre-to-fibre gain of 14±1 dB and ripple ±0.1 dB without antireflection coating on the fibres have been achieved     

Measurement of strain relief in an experimental optical fibre cable

Optical cables made by helically winding loose-tubed fibres around a central member can be designed to tolerate different amounts of axial strain before the fibres are strained. Here an optical technique is used to measure the strain relief achieved in an experimental cable incorporating fibres tubed under different conditions. The results are in good agreement with the strain relief predicted from the cable geometry.     

Recording of efficient high-order Bragg reflectors in opticalfibres by mask image projection and single pulse exposure with anexcimer laser

A technique using high resolution mask projection for creating efficient Bragg grating reflectors in optical fibres by single excimer laser pulse exposure is described. Using a deep UV projection system with a large image field size and micrometre resolution, gratings with periods between 1 and 6 μm have been recorded in Ge-doped fused silica fibres that produce high order Bragg reflections in the wavelength range 1.43-1.65 μm     

Subpicosecond measurement of response of optical fibres

A novel technique is described for measuring the impulse response of short samples of monomode and multimode optical fibres, with a resolution better than 0.1 ps. The times of arrival of the modes of a multimode fibre are resolved.     

Cutoff wavelength determination in single-mode optical fibres by measurement of equalisation wavelength

A simple interferometric method for indirectly determining a value for the cutoff wavelength of single-mode optical fibres is described. The technique is accurate and no stringent requirements are placed on the experimental equipment.     

Elastic profile measurements of optical fibres via reflection acoustic microscopy

The concentration of dopant materials which are responsible for the variation of the dielectric profile of the fused SiO2 host material for optical fibres also changes the elastic properties. This change has been observed by an acoustic microscope operated at 450 MHz. Acoustic micrographs of single-mode, multimode graded-index and multimode step-index optical fibres are given. This technique may be applicable to the study of fibre acoustic waveguides.     

Solution-doping technique for fabrication of rare-earth-doped optical fibres

A solution-doping technique is reported for the reproducible fabrication of low-loss optical fibres containing up to 4000 parts in 106 of rare-earth ions. The method produces excellent dopant uniformity and is sufficiently versatile to allow codoping with different ions.     

Characterisation of single-mode fibres by near-field measurement

A new technique for the determination of the refractive-index profile of single-mode optical fibres from a simple near-field measurement is proposed. This permits one to deduce accurately all the important parameters of the fibre.     

Low-loss Y-coupler for multimode single fibres

A technique for making low-loss 3dB Y-couplers in multimode single fibres was developed and evaluated. The couplers were obtained by the fusion of two optical fibres by means of a neated Kantal wire. A set of fifty samples using a Pilkington step-index fibre showed an average excess insertion loss of about 0.7dB.     

Fibre refractive-index profiling by modified near-field scanning

A modified bounded-mode near-field scanning method for determining the refractive-index profiles of optical fibres is described. The technique is simple to implement and allows the fibre numerical aperture and geometry to be measured.     

Loss measurements of microstructured optical fibres with metal-nanoparticle inclusions

Optical losses of measured optical fibres (MOFs) with silver nanoparticle inclusions are measured when visible light is guided in the core. The high pressure chemical deposition technique used to deposit the metal offers good control of the particle sizes allowing for varying transmission properties. The low losses demonstrate the potential for the silver impregnated MOFs to be integrated with conventional optical fibre devices.     

Temperature desensitisation of delay in optical fibres for sensor applications

We demonstrate a significant reduction in delay sensitivity against temperature in optical fibres, using a novel tight jacketed fibre structure. This technique has the cabability of producing fibre in which the optical delay is insensitive to temperature. This has potential in the field of sensors and fibre devices.     

Spectral losses of low-OH-content optical fibres

Very-low-OH-content optical fibres consisting of borosilicate-cladding phosphosilicate-core have been produced by a chemical vapour deposition technique. One of the fibres, whose transmission loss was less than 1 dB/km between 0.95 and 1.37 ?m, showed a minimum loss of 0.47 dB/km at 1.2 ?m.     

Polarisation optical time domain reflectometry

A proposed new optical fibre technique will allow measurement of the spatial distribution of physical fields, and will also allow location of anomalous features in single polarisation state monomode optical fibres such as are under discussion for very high bandwidth communication.