An alternative test to check the validity of convergence results

This paper presents a simple method for identifying distributional dynamic properties of economies using the ideas of concordance and discordance. It can be employed to examine the strength and validity of the results of other methods. The method has the advantage of comparing distributions at two points without relying on intermediary data between the two time points. We present results that suggest there is more ‘strong-divergence’ than ‘strong-convergence’ in GDP between countries over the time period 1960-2000 although the distribution exhibits both convergent and divergent characteristics

Photoelastic in-fibre birefringence modulator operating at the fundamental transverse acoustic resonance

A Highly efficient photoelastic in-fiber birefringence modulator is demonstrated. It operates at the acoustic frequency ~23MHz which corresponds to the fundamental transverse acoustic resonance of a 125µm diameter silica fiber. Using an analyzer at the output end of the fiber we obtained ~90% amplitude modulation for an RF power of 0.7 W

Acousto-optic in-fibre modulator using acoustic focusing

A new efficient in-fibre acousto-optic phase modulator is demonstrated in which the acoustic wave is focused onto the fibre by reflection from a cylindrical surface. The device exhibits a phase modulation of 2.63 radians at the light wavelength of 1550 nm, using an RF frequency of 86 MHz and a power of 1W

Low power acousto-optic device in tapered single-mode fibre

We report a new acousto-optic device based on tapered single-mode fibre. Since the overlap between acoustic and optical waves is complete, very little acoustic power (less than 1 microwatt) is required

Cavity dumping of neodymium-doped fibre lasers using acousto-optic modulator

We report high-repetition-rate pulses obtained by cavity dumping of a neodymium-doped phosphate glass fibre laser operating at 1053 nm using a specially constructed acoustooptic modulator. With 27 mW absorbed pump power at 812 nm we obtained stable trains of output pulses with repetition rate in the range 0.5 to 8MHz having corresponding pulse widths in the range 127 to 19 ns without significant sacrifice in the average output power of 8 mW

High-performance four-port acousto-optic frequency shifter at 1.55µm using standard single-mode telecommunications fibre

If a four-port fused-taper coupler is constructed from dissimilar fibers, the maximum splitting ratio can be close to zero over a broad spectral band. As previously shown, such a null coupler can be used to form an effective four-port acousto-optic frequency shifter. In Ref. 1, two dissimilar nonstandard fibers were used. Here we report the successful construction of a null coupler made by using standard telecommunications fiber. The procedure involves pretapering one of an identical pair of fibers to provide the necessary dissimilarity. In this way the device can be constructed entirely from one fiber type with four identical ports, and it can be made compatible with any existing network. Our present device used standard 125µm single-mode telecommunications fiber throughout, for operation at a wavelength of 1.55µm

Acousto-optically Q-switched fibre laser source of high peak power and short duration pulses for fibre sensor applications

We report on a fibre laser source which emits high peak power (>0.7 kW) and short (2.8 ns) Q-switched pulses at 1.06 µm suitable for distributed fibre sensor applications using an absorbed pump power of 13 mW and miniature acousto-optic modulator

Fibre-optic laser doppler velocimetry]

SIGLEAvailable from British Library Document Supply Centre- DSC:DX84402 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Field statistics modelling of beat noise in an optical amplifier

The authors present a rigorous and self-contained noise analysis of an optical amplifier based on the statistics of the input source field and the amplified spontaneous emission field of the amplifier. The method enables us to obtain the frequency dependence of the output electrical noise power, which has not been derived in previous studies of optical amplifier noise based on the photon statistics master equation. The authors characterise for the first time the noise of an optical amplifier in combination with a super-fluorescent source, taking into account the frequency dependence of the gain and the presence of optional optical filters

Remote state-of-polarisation control in polarisation-maintaining fibre

By monitoring the state of polarization of light transmitted and reflected back through a length of polarization-maintaining fibre. the output is actively controlled in a non-eigenstate. Control is effected bia a single variable, namely the temperature of a short section of fibre. In addition to the normal eigenstate outputs, the controlled output may be electronically tuned between quadrature states