Dispersion compensation with SBS-suppressed fibre phase conjugator using synchronised phase modulation

204 km, 10 Gbit/s standard optical fibre transmission is successfully demonstrated using the mid-span spectral inversion technique with a stimulated Brillouin scattering suppressed fibre phase conjugator, proposed recently by Tani and Yamashita. Transmission performance has been improved compared with a conventional phase conjugator.     

Dispersion of Verdet constant in stress-birefringent silica fibre

The Faraday effect in stress-birefringent silica fibre is discussed theoretically and measured experimentally. In the red and infra-red spectral range, the Verdet constant is found to be VH = 2.0 × 10?35 v2 rad/A, where v is the optical frequency in hertz.     

Dispersion in a low-loss multimode fibre measured at three wavelengths

Short pulses from mode-locked lasers (neodynium/yttrium-iron-garnet and krypton) were used to measure mode and material dispersion in 20 m of a multimode fibre at 1060, 647 and 568 nm. Uniform illumination of the cone of acceptance at the input caused a 200 ps pulse to broaden to 400 ps.     

Dispersion compensation of 16 ps pulses over 100 km of step-indexfibre using cascaded chirped fibre gratings

The propagation of 16 ps data pulses over 100 km of step-index fibre using two cascaded chirped fibre gratings to achieve dispersion compensation is presented. At the output, the pulses are broadened slightly to 20 ps, indicating the potential for 50 Gbit/s operation     

Dispersion compensation over 270 km at 10 Gbit/s using anoffset-core chirped fibre Bragg grating

A 120 mm long fibre Bragg grating, adjustably chirped by an offset-core technique, compensates for dispersion in a 10 Gbit/s optical communication system operating at 1054 μm over 270 km of non-dispersion-shifted fibre. Simultaneous compensation of fibre dispersion and source chirp in a directly modulated system is also described     

Dispersion slope equalizer for dispersion shifted fiber using alattice-form programmable optical filter on a planar lightwave circuit

This paper reports an integrated-optic dispersion slope (third-order dispersion) equalizer for dispersion shifted fiber which employs a lattice-form programmable optical filter on a planar lightwave circuit (PLC). This dispersion slope equalizer consists of nine symmetrical interferometers interleaved with eight asymmetrical interferometers. The performance of the equalizer is evaluated numerically. We confirm experimentally that this equalizer is effective in reducing the pulse waveform deterioration caused by the dispersion slope. In addition, the equalizer improves the power penalty of a 200-Gb/s, 100-km, time-division multiplexed optical transmission experiment     

High-power cascaded Raman fibre laser using phosphosilicate fibre

A 13.2 W second cascade phosphosilicate cascaded Raman fibre using a 450 m phosphosilicate singlemode optical fibre is demonstrated. The lasing wavelength is 1539 nm and the conversion efficiency is 32.5%. This is the highest output power ever reported from a cascaded Raman fibre laser in the 1400-1600 nm range.     

Detection of TCM signals on severely distorted channels using survival path feedback equaliser

A new technique for detecting trellis code modulation signals in severely distorted channels is proposed. This technique is based on feedback of the survival paths from the Viterbi decoder and the equaliser uses these survival paths to update the branch metrics of the decoder. Simulation results clearly show that the system performance is significantly improved.<>     

Reduced complexity implementation of Bayesian equaliser using localRBF network for channel equalisation problem

The authors examine a method for reducing the implementation complexity of the RBF Bayesian equaliser using model selection. The selection process is based on finding a subset model to approximate the response of the full RBF model for the current input vector, and not for the entire input space. Using such a scheme, for cases in which the channel equalisation problem is non-stationary, the requirement for updating all the centre locations is removed, and the implementation complexity is reduced. Using computer simulations, we show that the number of centres can be greatly reduced without compromising classification performance     

Blue light generation in holey fibre using frequency doubled fibre pump source

A report is presented on the efficient generation of 18 mW of 428 nm light by propagating frequency doubled 780 nm pulses from an all-fibre integrated picosecond pulse source with kW level peak power through a length of highly nonlinear holey fibre. The wavelength conversion process is attributed to resonant coupling between solitons and dispersive radiation.     

High-speed fibre Bragg grating sensor interrogation using dispersion compensation fibre

A novel high-speed fibre Bragg grating (FBG) sensor interrogator using dispersion-compensating fibre is proposed and demonstrated. The wavelength shift measurement of the FBG sensor is converted to time-domain measurement. The high-speed potential of this scheme was investigated experimentally, demonstrating an effective sampling speed of 2.44 megasamples per second.     

Dispersion compensated 80 Gbit/s WDM transmission over 1171 kmstandard singlemode fibre

WDM transmission experiment at 80 Gbit/s (8×10 Gbit/s, 0.8 nm channel spacing) over 1171 km of standard singlemode fibre has been performed with a 90.1 km recirculating loop incorporating a dispersion compensation fibre and gain-equalising optical bandpass filters     

Bend measurement using Bragg gratings in multicore fibre

The first measurements of curvature made using Bragg gratings written in separate cores of a multicore optical fibre are described. The gratings act as independent, but isothermal, strain gauges. The difference in Bragg wavelength between the gratings provides a temperature-independent measurement of the local curvature     

Remote temperature sensing using polarisation-preserving fibre

A fibre-optic temperature sensor is described in which the change in modal birefringence of a short length of polarisation-preserving fibre is monitored in reflection through a 90 m length of input fibre. The system shows high sensitivity and good downlead insensitivity.     

Picosecond optical sampling using four-wave mixing in fibre

An all-optical sampling system with 20 ps resolution realised by employing four-wave mixing in a fibre is demonstrated. Using only semiconductor laser sources, picosecond pulses are displayed on a microsecond time scale with a low speed receiver.<>     

Wideband gain flattened erbium fibre amplifier using a photosensitive fibre blazed grating

An erbium fibre amplifier with a highly flattened gain spectrum is demonstrated for the first time using an all fibre photosensitive Bragg grating. An ASE spectrum flattened to within +or-0.5 dB over a bandwidth of 35 nm in the 1550 nm window is achieved with a 3 mm long radiation coupling Bragg fibre grating.<>     

Intensity noise in lightwave fibre systems using LED transmitters

Excess noise in fibre-optic systems using LED transmitters is analysed. The relative excess noise (REN) of a commercially available single-mode LED source was measured to be -128+or-1.0 dB Hz/sup -1/. REN is shown to be significant in single-mode fibre systems in which the detected optical power is greater than -25 dBm.<>     

Antisymmetric pulse generation using phase-shifted fibre Bragggrating

A 10 mm Bragg grating with a 0.18 nm (peak-to-peak) spectral response was designed to shape a train of 7 ps Gaussian pulses into antisymmetric Hermite-Gauss pulses. The pulses were characterised in the frequency and time domain. The presence of the phase shift was verified by propagation in standard fibre     

In-line optical fibre filters using dispersive materials

It is shown that optical fibre filters can be made by choosing core and cladding materials having appropriate dispersive characteristics. The bending loss of the dispersive optical fibres is calculated, and proves them to be useful for short- and long-wavelength-pass filters.     

Digital fibre transmission using optical homodyne detection

Homodyne detection of a 140 Mbit/s PSK signal transmitted over 30 km of cabled fibre has been achieved using a balanced optical phase-locked-loop receiver. System phase error was dominated by the laser frequency instability and not the cabled fibre.