Low-loss joints between dissimilar fibres by tapering fusion splices

A technique is reported for reducing the splice loss between dissimilar or similar fibres. The technique involves tapering a fusion splice to produce a mode transformer which converts the fundamental mode of one fibre to that of the other with negligible loss. Results of theoretical calculations are presented which show the fundamental mode field shape at the splice junction and the estimated joint loss between two dissimilar fibres as a function of the splice diameter. Initial experiments are reported which have achieved splice loss reductions from 1.5 dB to 0.56 dB and 0.7 dB to 0.15 dB between dissimilar and similar fibres, respectively, at 1.3 ?m.     

Reduced loss in extruded soft glass microstructured fibre

The fabrication of small core high-NA soft glass microstructured optical fibres with propagation loss as low as 0.6 dB/m at 1100 nm is reported. Advances in soft glass preform extrusion and fibre fabrication have allowed the first demonstration that extrusion does not significantly contribute to the fibre loss.     

Moulded multifibre connectors using rectangular multirod arrangement

Moulded demountable compact multifibre connectors have been constructed which have a rectangular arrangement of precision rods within the plug mouldings to locate the fibres in its interstices and to align pairs of plugs. The samples of 10-fibre connector tested so far have exhibited average insertion loss of 0.37 dB for step-index fibre 60 ?m in core diameter. Connectors for an arbitrary number of fibres can be made from the same mould and parts by using this method.     

Single-polarisation operation of highly birefringent bow-tie optical fibres

Experimental results show that bow-tie fibres with high levels of stress-induced birefringence can be operated such that they support only a single linearly polarised mode. Under these conditions the loss of the fibre is 5 dB/km for the guided mode and 55 dB/km for the suppressed mode For short-length operation as a polariser, extinction ratios as high as 50 dB/m have been obtained.     

Polarisation-maintaining fibre couplers with low excess loss

Polarisation-maintaining fused fibre couplers with excess loss of less than 0.1 dB have been fabricated by using polarisation-maintaining and absorption-reducing (PANDA) fibres with matched-index stress-applying parts. The couplers show polarisation crosstalk of less than ?30 dB.     

Monomode fibre fusion splicing with CO2 laser

Monomode fibres have been spliced with a CO2 laser. The average splice loss for 50 splices was 0.18 dB. The average breaking stress of the splices was 1 GPa. Splice loss lower than 0.4 dB was possible with bad fibre ends (breaking angle about 4°) or with core eccentricity as large as 4 ?m.     

Early morphological changes in the rat soleus muscle induced by tenotomy and denervation

Early morphological changes of the rat soleus muscle induced by tenotomy were examined by scanning and thin-section electron microscopy. The potassium hydroxide (KOH) and collagenase treatment was successfully used to remove extracellular materials and to examine the surface of muscle fibres with a scanning electron microscope. Morphological changes in the fibre surface appeared as early as 12 h after tenotomy, showing wrinkling of the sarcolemma in localized areas. At 24 h post-operative, transverse folds and grooves were conspicuous along the entire length of muscle fibres. Tenotomized muscles which were denervated simultaneously or within 24 h of tenotomy did not show any appreciable changes in the fibre surface. Thin-section electron microscopy revealed that the earliest change inside muscle fibres was the occurrence of focal or segmental areas of an irregular alignment of myofibrils representing myofibril disorganization with occasional disintegrated Z lines at 24 h after tenotomy. Segmental myofibril breakdown was occasionally found to extend obliquely from the fibre periphery to the central area. Such myofibril disorganization became more conspicuous along muscle fibres, especially in the central area, at 2 days after tenotomy, showing the loss of thick filaments within myofibrils and the disintegration of Z lines. Such myofibrillar disorganization can be correlated with the morphological changes in the fibre surface in view of the clinical implication.     

Low-loss multifibre connectors with plug-guide-grooved silicon

Low-loss interchangable multifibre connectors have been developed using plugs consisting of large guiding grooved and fibre-fixing V-grooved silicon chips. Guiding grooves etched on silicon chips accomplish extremely small average fibre offset less than 2 ?m. A 6-fibre connector plug pair selected from the same wafer exhibits 0.14 dB average connection loss. Connector plugs from different wafers exhibit 0.17 dB and 0.24 dB average connection losses.     

Fabrication of low-loss Al2O3-doped silica fibres

This letter is concerned with the alternative dopant of Al2O3 for VAD silica-based optical fibres. In order to clarify basic loss characteristics of Al2O3-doped silica glass fibres, single-mode fibres were made. The fabricated single-mode fibre shows an ideal step-index profile and a low transmission loss of 0.65 dB/km at 1.56 ?m.     

Low-loss fibre-pigtailed 256 channel arrayed-waveguide gratingmultiplexer using cascaded laterally-tapered waveguides

A fibre-pigtailed 25 GHz-spacing 256 channel arrayed-waveguide grating (AWG) module has been fabricated. The module was composed of an AWG chip with a Δ of 1.5%, a fan-out planar lightwave circuit (PLC) with a A of 0.75%, an input fibre and two 128 fibre arrays. To improve the coupling loss of the 256 output fibres, a new PLC-fibre connection using cascaded laterally-tapered waveguides was developed. The fibre-pigtailing loss is reduced to only 1.1 dB and a multiplexer with a low insertion loss of 1.9-3.9 dB is realised     

Metal-assisted coupling to hollow-core photonic crystal fibres

Selective coupling to the fundamental mode of short hollow-core photonic bandgap fibres without exciting cladding modes is improved by gold-coated fibre end facets. Cladding modes are suppressed by 20-30 dB for single-and multimode fibre launch, respectively, while in-band power loss is 3-8 dB.     

26 km-long polarisation-maintaining optical fibre

The letter describes the development of a long-length and large-diameter preform for polarisation-maintaining optical fibres. The preform was 470 mm in length and 48 mm in diameter. As a result, a 26 km-long PANDA fibre is developed. This fibre achieves crosstalk of ?22 dB, corresponding to h = 2.4 × 10-7m-1 and a transmission loss of 0.3 dB/km at a wavelength of 1.56 ?m. These fibres will be useful for future high-speed and medium-span coherent optical communications.     

Effect of dopants on transmission loss of low-OH-content optical fibres

We formerly developed very-low-OH-content optical fibres consisting of a borosilicate cladding and a phosphosilicate core. The transmission loss of the fibre was 0.47 dB/km at 1.2 ?m. We have further investigated the effects of dopants in pure silica on the losses of fibres. The letter clarifies the effects of dopants on the loss in the near-infrared region.     

Characteristics of laser-diode modules using thermally-diffused expanded core fibres

0.8 mu m band laser-diode modules have been developed for coupling to fibres with a relative refractive-index difference ( Delta ) as high as 2.3%. A coupling loss of 3.1 dB, fibre output power over 35 mW, and excellent temperature stability in the range from -10 to 60 degrees C were realised using a thermally-diffused expanded core fibre.<>     

Microbending loss of multimode square-law fibres: a ray theory

Using a simple ray theory, we show that the steady-state microbending loss of multimode square-law fibres is equal to 8?/? dB/m. We have defined ? = ?n/n, and ? is the power-spectral density of the fibre axis curvature in any meridional plane at the natural frequency of ray oscillation, expressed in reciprocal metres. The steady-state irradiance distribution in the fibre core is also given.     

Optical-fibre coupling to high-silica channel waveguides with fibre-guiding grooves

A practical coupling technique between high-silica multimode channel waveguides and optical fibres has been demonstrated using guiding grooves formed simultaneously with waveguides on a substrate. The fibre-waveguide (15 mm long)-fibre insertion loss was 1.23 dB.     

Transmission loss in low grade SiCl4 v.a.d. fibres

The transmission loss of v.a.d. fibres made from various grade raw materials has been studied. It has been found that low loss spectra are obtained in v.a.d. fibre fabricated from the raw material of low grade silicon tetrachloride (99.17%). The transmission loss of the fibre is 0.60 dB/km at 1.55 ?m.     

New star coupler compatible with single multimode-fibre data links

A star coupler for optical data links for use with a single multimode fibre, as opposed to fibre bundles, was realised in the form of a multiport directional coupler assembled from bicorical tapers of multimode fibres. The insertion loss above furcation loss of the 4-paired-port coupler was measured to be 2.8 dB.     

Ceramic capillary splices for optical fibres

A simple technique for splicing optical fibres is reported. The technique utilises a self-aligning ceramic capillary with inner dimensions slightly larger than the optical fibre. An average loss of below 0.1 dB is obtained for splices in graded-index and single-mode fibres with a 50 and 10 ?m core diameter, respectively.     

Single-mode fibre connectors

A low-loss detachable connector has been fabricated for single-mode optical fibres. It consists of a pair of plugs accommodating fibres to be joined and a sleeve provided with ball-bearing arrays to align the plugs. The average connecting loss is reduced to as low as 0.5 dB, including fibre end reflection.