Polarisation-scrambled Er-doped superfluorescent fibre source with improved mean-wavelength stability

A polarisation scrambling scheme is employed to reduce the pump-polarisation-dependent mean-wavelength change in the Er-doped superfluorescent fibre source for gyroscope application. A PZT-based fibre-optic polarisation modulation is used at the pump port for polarisation scrambling. Changes of mean wavelength owing to pump polarisation variation are suppressed below 1 ppm.     

Quadrature phase sampling of a fibre interferometer by input-polarisation switching

A technique for the generation of quadrature phase components at the output of a fibre interferometer using input polarisation modulation is described. This approach allows a passive path-balanced sensor interferometer to be remotely interrogated using a simple concept based on polarisation switching of the input state of polarisation coupled to the interferometer.<>     

Monomode fibre polarisation scrambler

A technique for the pseudodepolarisation of a long-coherence-length source is described, which is based on a simple polarisation modulation scheme. Using a length of high-birefringence fibre wound on to a piezoelectric transducer, a simple all-fibre polarisation scrambler can be constructed.     

New measurement method for polarisation dispersion in single-mode fibres employing frequency-modulated optical signal

A new measurement method for polarisation dispersion in a single-mode fibre, utilising the coherence property of frequency-modulated laser diode light, is proposed. Polarisation dispersion is determined exactly by selecting the modulation condition which gives depolarisation light at the fibre end.     

Acousto-optic phase modulator for single-mode fibres

A compact fibre-optic phase modulator with a single-mode fibre positioned along the axis of a cylindrical PZT acoustic transducer is investigated. The fibre is bonded inside a glass capillary tube, which is in turn epoxied inside the transducing cylinder to give a solid, mechanically stable structure. The maximum sensitivity of the phase shifter is 0.058 rad/V cm at 6.02 MHz. No polarisation modulation is observed.     

Characterisation of differential group delay of fibre devices with high resolution and enhanced immunity to environmental perturbation

By integrating a fibre polarisation scrambler with the modified phase shift modulation technique, differential group delay characterisation is demonstrated with high wavelength and delay resolution, and enhanced measurement immunity to environmental perturbation.     

Measurement of Kerr nonlinearity coefficient of fibres using nonlinear polarisation rotation

A simple and accurate method to measure the Kerr nonlinearity coefficient of optical fibres is proposed and demonstrated. The method is based on the nonlinear polarisation rotations caused by cross-phase modulation between two lightwaves of different wavelengths co-propagating in fibres. TheKerr nonlinearity coefficients of standard singlemode fibre and TrueWave^TM reduced slope fibre measured with this method are in good agreement with the published data.     

Polarisation properties of long-period grating inscribed in pure-fused-silica photonic crystal fibre

The first measurements of polarisation properties of a long-period grating inscribed in an endlessly singlemode photonic crystal fibre are reported. Strong modulation in the spectra of polarisation-dependent loss and differential group delay with periods of 2.6 and 1.3 nm, respectively, were found. As such an effect has not been observed in standard optical fibres, it is believed that this is due to the specific mode structure of the holey fibre used for grating fabrication     

640 Gbit/s DQPSK, single wavelength-channel transmission over 480 km fibre link

Error-free transmission of a 640 Gbit/s data signal over a 6/spl times/80 km dispersion-managed fibre link using the DQPSK modulation format, OTDM technology and polarisation multiplexing, is reported.     

Alignment of polarisation-maintaining fibres by temperature modulation

A novel nondestructive technique for rapidly aligning the input state of polarisation to a stress-effect polarisation-maintaining fibre has been implemented using temperature modulation. It can be applied easily on to a short length of fibre, gives alignment to better than 0.5°, and can identify the fast and slow axes.     

Polarisation-independent intensity modulator based on lithiumniobate

Broadband, polarisation-independent intensity modulation based on a lithium niobate phase modulator in a fibre Sagnac interferometer configuration is demonstrated. Residual polarisation dependence is found to be as low as <0.25 dB for low frequency operation, and <2 dB to frequencies of >20 GHz     

High-power 0.82 mu m superluminescent diodes with extremely low Fabry-Perot modulation depth

Superluminescent AlGaAs-GaAs diodes with 15 mW output power and 1% Fabry-Perot modulation depth and modules with 3 mW polarisation maintaining fibre output have been developed. At output powers of more than 8 mW the effect of saturation on power fluctuations was observed.<>     

Polarisation conservation in single-mode fibres

There exist proper orthogonal elliptical polarisation states, which are maintained over long fibre length without converting. When one of the proper polarisation states is excited, orthogonal polarisation less than ?40 dB is confirmed after 5 km single-mode fibre transmission. It is also proposed that twisted single-mode fibres show a high degree of polarisation for any incident polarisation state. The polarisation characteristics are hardly affected by external perturbations.     

High-extinction-ratio low-loss tightly bent PANDA fibre

The realisation of tightly bent PANDA polarisation maintaining fibre with minimal reduction of extinction ratio and throughput power is described for the miniaturisation of polarisation maintaining fibre circuits. After mechanically side-polishing the bare PANDA fibre, bend diameters as small as 1 mm have been achieved that preserve the fibre s extinction ratio ( 35 dB) with minimal loss ( 0.1 dB).     

Dynamic polarisation fluctuation characteristics of optical fibre submarine cable coupling under periodic variable tension

The dynamic polarisation fluctuation in optical fibre submarine cable coupling under periodic variable tension of 4?7 tons is presented. It is confirmed that the polarisation fluctuation of the optical fibre submarine cable coupling changes linearly with the periodic variable tension.     

Polarisation mode dispersion measurements in long single mode fibres

A new method to measure polarisation mode dispersion is described, in which the accuracy is more than 0.1 ps. 0.17 ps polarisation mode dispersion was obtained for about 1 km length of fibre. The result is compared with the retardation obtained for a short length of the fibre.     

Degree of polarisation in a birefringent single-mode optical fibre

We examine the evolution of the polarisation of a field propagating in a birefringent single-mode optical fibre. The explicit dependence of the degree of polarisation on pulse duration, coherence time of the source and chromatic delay of the fibre is derived.     

Polarisation tuning by micro-fluidic motion in air-silicamicrostructured optical fibre

The ability to manipulate the polarisation of light in an optical fibre by moving fluids within air channels that run along the length of the fibre-cladding region is demonstrated. A polarisation tuning of 2π phase change is achieved in a 4 cm length of fibre. The displacement of fluid in the channels measured against temperature is in good agreement with the theoretical predictions     

Multiwavelength erbium-doped fibre laser based on ahigh-birefringence fibre loop mirror

A novel multiwavelength fibre laser is proposed, which is based on a fibre loop mirror formed by a high-birefringence (HiBi) fibre, a polarisation controller, and a directional coupler. By setting the polarisation controller properly, the HiBi fibre loop mirror acts as a polarisation-independent wavelength filter. With this configuration, the wavelength spacing of the laser can be varied accurately by adjusting the length of the HiBi fibre. Experimentally, by cooling the erbium-doped fibre with liquid nitrogen to reduce its homogeneous linewidth, stable emission at 16 wavelengths with a spacing of 0.8 nm and an amplitude variation of <5 dB was achieved     

Fibre-polarimeter based on grating taps

The fabrication of novel tilted fibre Bragg gratings coupling light out of the fibre core into two different directions is demonstrated. These gratings in combination with a fibre based quarter waveplate are used to form a high-speed fibre polarimeter for real-time polarisation monitoring.