Investigation of optical fibre buckling in loose-tube packaging

The use of a loose-tube packaging around an optical fibre offers a high degree of mechanical isolation but can cause severe buckling of the fibre if differential contraction of the packaging occurs. The formation of this buckled state is investigated and loss measurements made on buckled lengths of fibre.     

Dispersion-shifted convex-index single-mode fibres

The structural design of the single-mode fibre with a convex-index profile is described to achieve zero dispersion at 1.55 ?m. As a result of the fibre design, it is clarified that the bending loss of the convex-index fibre is the smallest among the losses of various index profile fibres such as step, triangular and Gaussian ones.     

Transmission loss characteristics of fluoride glass single-mode fibre

The transmission loss spectrum of a fluoride glass single-mode fibre as obtained with a new preform fabrication technique is shown. It is clearly confirmed on the loss spectrum that the obtained fibre is a single-mode waveguide in the minimum loss wavelength range (2?4 ?m). The minimum loss of this fibre is 8.5 dB/km at 2.2 ?m and the OH excess loss is 15dB/km at 2.85 ?m. This fabrication technique is effective in eliminating OH contamination.     

Wavelength-division-multiplexed optical transmission system with single-mode fibre and a dual-wavelength hybrid laser light source

Wavelength-division-multiplexed optical fibre transmission over a 45km single-mode fibre using a hybrid dual-wavelength InP CSBH laser light source emitting at 1.3 ?m and 1.5 ?m has been demonstrated. This simple and economic system provides two distinct optical data channels without requiring electronic or optical multiplexing. Optical crosstalk was unobservable while operating the separate optical channels at 1.5 Gbit/s and 90 Mbit/s, respectively. The use of a single light source eliminates multiple fibre-to-source alignments, reducing transmitter packaging costs.     

All-silica package for tapered couplers

The primary packaging of singlemode tapered couplers, by fusing the fibre leads with a negligible loss to a silica substrate, is reported. This procedure eliminates adhesive, and ensures matched coefficients of thermal expansion throughout.<>     

Ultra-low-capacitance flip-chip-bonded GaInAs PIN photodetector for long-wavelength high-data-rate fibre-optic systems

A novel GaInAs substrate illuminated photodetector structure is reported for the 1.0?1.7 ?m wavelength range with capacitance as low as 0.02 pF, packaging stray capacitance below 0.02 pF, 97% quantum efficiency and subnanoampere leakage current. The device is rugged, epoxy-free, does not use an integral fibre pig-tail and wire bonding to the detector chip is not required.     

Single-mode-fibre design for 4 ?m band operation

The splicing and cabling added loss are evaluated for 4 ?m-wavelength single-mode fibres. It is shown that splice offset and microbending losses are critical and that high index differences are required. Added losses are small as 0.01 dB/km can be obtained with careful fibre design and handling.     

Ultimate low-loss single-mode fibre at 1.55 ?m

A very low loss single-mode fibre with a minimum loss of 0.20 dB/km at a wavelength of 1.55 ?m is attained; this loss reaches the ultimate lower loss limit of silica-based optical glass fibre. The loss mechanism is also discussed.     

Return loss measurements of lensed fibre to semiconductor laser

Measurements have been carried out to investigate the relationship between coupling efficiency and return loss when light is coupled from a laser into a lens-ended optical fibre. To attain the values of return loss necessary for full duplex operation on a high split level (e.g. 32) passive optical network, a change to conventional packaging techniques will be necessary.<>     

Double crucible optical fibre for data link applications

A short distance, data link fibre has been made by the double crucible method. The fibre has a large core (175 ?m), high NA (0.4) and a minimum loss of 7.5 dB/km. By lowering the water content of the fibre the usable wavelength range has been extended to 1.3 ?m     

Transmission loss of UV-curable silicone-coated optical fibre

Transmission characteristics of UV-curable silicone-coated optical fibre were investigated in relation to the elastic property and the chemical structure of the coating. It was found that added loss of the coated fibre is less than ±0.06 dB/km in the range ?75 to 80°C. The infra-red loss increase of the UV-curable silicone-coated fibre was appreciably lower than that for thermally cured silicone-coated fibre at elevated temperatures.     

Detailed evaluation of an attainable repeater spacing for fibre transmission at 1.3 ?m and 1.55 ?m wavelengths

An attainable repeater spacing at 1.3 ?m and 1.55 ?m wavelengths using a step-index monomode fibre cable is given, after detailed consideration of total loss as well as total dispersion of an optical fibre. The longest attainable repeater spacing at 1 Gb/s is about 100 km at 1.55 ?m wavelength using a single-mode laser diode and a monomode fibre with a relatively small core-cladding refractive index difference, e.g. about 0.2%.     

Design and fabrication of dispersion-shifted depressed-clad triangular-profile (DDT) single-mode fibre

A new depressed-clad triangular-index-profile single-mode fibre with dispersion minimum shifted to the 1.55 ?m region is investigated. Fibres with high cutoff wavelength (?1.1 ?m) and low dispersion slope (?0.052 ps/km nm2) at their minimum dispersion wavelength (?1.55 ?m) were fabricated. Results from 226.7 km of fibre show an average loss of 0.241 dB/km at 1.55 ?m and 0.232 dB/km at the loss minimum.     

Ultralong multimode optical fibre fault location using Raman optical time domain reflectometry

The OTDR technique using the stimulated Raman scattering effect (ROTDR) is applied to ultralong multimode optical fibre fault location. In experiment, Stokes light pulses at 1.6 ?m wavelength, which are the most advantageous for fault location, are used. It is shown that the multimode fibre break, more than 80 km long, is locatable, and fibre loss at 1.6 ?m is measurable by the ROTDR technique.     

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.     

Transmission properties of 30.4 km v.a.d. fibre

A 30.4 km graded-index fibre has been fabricated by the vapour-phase axial deposition (v.a.d.) method. Optical-time-domain reflectometry was used to characterise the loss uniformity along the longitudinal direction of this fibre. Measured transmission loss and 6 dB bandwidth with good uniformity along this long fibre were 0.54 dB/km and 1200 MHzkm at the 1.3 ?m wavelength, respectively.     

Jointing loss in single-mode fibres

The jointing loss of single-mode fibres is mainly dependent on their numerical apertures, and is largely independent of normalised frequency and fibre diameter. The letter presents simple loss predictions as an aid for practical design work of single-mode fibre joints.     

Low-insertion-loss channel waveguides in LiNbO3 fabricated by proton exchange

We describe single-mode proton exchange waveguides in Z-cut LiNbO3 at the 1.32 ?m wavelength having low fibre/waveguide/fibre insertion loss.     

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.     

Transmission properties of 2.55 ?m fluoride glass fibre

Data transmission and bandwidth measurements have been performed on a fluoride glass fibre at the 2.55 ?m minimum loss wavelength of the fibre, using a colour centre laser and an external waveguide modulator. Fibre modal dispersion limited the fibre bandwidth to 360 MHz.