Soliton transmission at 10 Gbit/s over 2022 km of standard fibre with dispersion compensation

We present experimental results of 10 Gbit/s, 20 ps soliton data transmission over standard fibre, dispersion compensated to 0.5 ps/nm/km. Acceptable Q values were measured to a distance of 2022 km.

Recent developments in all-optical nonlinear signal processing for fiber-optic communications

All-optical data processing is expected to play a major role in future optical communications. Nonlinear effects in optical fibers have attractive applications in optical signal processing. In this paper, we review our recent advances in developing all-optical processing techniques at high speed based on optical fiber nonlinearities.

Adaptive electrical signal post-processing in optical communications systems

Improving bit error rates in optical communication systems is a difficult and important problem. The error correction must take place at high speed and be extremely accurate. We show the feasibility of using hardware implementable machine learning techniques. This may enable some error correction at the speed required.

Two-dimensional optical power distribution of side-out-coupled radiation from tilted FBGs in multimode fibre

Two-dimensional optical power distribution of the out-coupled radiation from UV-inscribed tilted fibre Bragg gratings (TFBGs) in multimode fibre (MMF) has been side-detected with high spatial/spectral resolution, showing a near-identical radiation mode profile to that measured from the fibre-end detection method. A comparative investigation of the radiation characteristics of TFBGs fabricated in singlemode fibre (SMF) and MMF clearly indicates that the radiation out-coupling is stronger and spatially more confined in MMF. The unique spatial-to-spectral encoding property of the coupling mechanism offers potential application in low-cost WDM devices.

Implementation of optical chemsensors based on HF-etched fibre Bragg grating structures

High-sensitivity optical chemsensors have been implemented by exploiting fibre Bragg grating structures UV-inscribed in D-shape, single-mode and multimode fibres and post-sensitized by hydrofluoric acid (HF) etching treatment. We have demonstrated that the Bragg grating structures which are intrinsically insensitive to chemicals can be sensitized by effective etching. All etched devices possess refractive index sensing capability that offers an encoding function to chemical concentrations. Most etched devices have been used to measure the concentrations of sugar solutions, showing a potential capability of detecting concentration changes as small as 0.1–0.5%.

Quasi-lossless data transmission with ultra-long Raman fibre laser based amplification

The project consists of an experimental and numerical modelling study of the applications of ultra-long Raman fibre laser (URFL) based amplification techniques for high-speed multi-wavelength optical communications systems. The research is focused in telecommunications C-band 40 Gb/s transmission data rates with direct and coherent detection. The optical transmission performance of URFL based systems in terms of optical noise, gain bandwidth and gain flatness for different system configurations is evaluated. Systems with different overall span lengths, transmission fibre types and data modulation formats are investigated. Performance is compared with conventional Erbium doped fibre amplifier based system to evaluate system configurations where URFL based amplification provide performance or commercial advantages.

Chirped fibre Bragg grating optical wear sensor

A novel sensor is demonstrated to allow a real-time measurement of the physical wear applied to the surface of an object. Two different measurement methods are presented, both utilizing the reflected power from a sacrificial chirped fibre Bragg grating to give the wear measurement. The measurement systems are simple to implement with the possibility of low cost designs depending on the application. The sensor can measure wear with a resolution of 120 μm. © 2004 IOP Publishing Ltd.

Two-dimensional optical power distribution of side-out-coupled radiation from tilted FBGs in multimode fibre

Two-dimensional optical power distribution of the out-coupled radiation from UV-inscribed tilted fibre Bragg gratings (TFBG) in multimode fibre (MMF) has been side-detected with high spatial spectral resolution, showing a near-identical radiation mode profile to that measured from the fibre-end detection method. A comparative investigation of the radiation characteristics of TFBGs fabricated in singlemode fibre (SMF) and MMF clearly indicates that the radiation out-coupling is stronger and spatially more confined in MMF. The unique spatial-to-spectral encoding property of the coupling mechanism offers potential application in low-cost WDM devices.

Patterning effects in a WDM RZ-DBPSK SMF/DCF optical transmission at 40 Gbit/s channel rate

Through extensive direct modelling we quantify the error statistics and patterning effects in a WDM RZ-DBPSK SMF/DCF fibre link using hybrid Raman/ EDFA amplification at 40 Gbit/s channel rate. We examine the BER improvement through skewed channel pre-coding reducing the frequency of appearance of the triplets 101 and 010 in a long data stream. © 2007 Elsevier B.V. All rights reserved.

Simultaneous multiple channel all-optical NRZ to CSRZ and RZ to CSRZ format conversion using an SOA-NOLM

The optical conversion bandwidth for an all-optical modulation format converter, based on a semiconductor laser amplifier in a nonlinear optical loop mirror (SOA-NOLM), is investigated. 4 Â 10 Gbit/s channels are all- optically converted between both non-return-to-zero (NRZ) and return-to-zero (RZ) format to carrier- suppressed return-to-zero (CSRZ). WDM transmission of the converted signals over a 194 km fibre span is then demonstrated. The receiver sensitivity for the converted four wavelengths is measured and compared after transmission.

Simultaneous multiple channel all-optical NRZ to CSRZ and RZ to CSRZ format conversion using an SOA-NOLM

The optical conversion bandwidth for an all-optical modulation format converter, based on a semiconductor laser amplifier in a nonlinear optical loop mirror (SOA-NOLM), is investigated. 4 Â 10 Gbit/s channels are all- optically converted between both non-return-to-zero (NRZ) and return-to-zero (RZ) format to carrier- suppressed return-to-zero (CSRZ). WDM transmission of the converted signals over a 194 km fibre span is then demonstrated. The receiver sensitivity for the converted four wavelengths is measured and compared after transmission.

Advanced techniques for the improvement of optical transmission systems

This thesis presents the experimental investigation into two novel techniques which can be incorporated into current optical systems. These techniques have the capability to improve the performance of transmission and the recovery of the transmitted signal at the receiver. The experimental objectives are described and the results for each technique are presented in two sections: The first experimental section is on work related to Ultra-long Raman Fibre lasers (ULRFLs). The fibre lasers have become an important research topic in recent years due to the significant improvement they give over lumped Raman amplification and their potential use in the development of system with large bandwidths and very low losses. The experiments involved the use of ASK and DPSK modulation types over a distance of 240km and DPSK over a distance of 320km. These results are compared to the current state of-the-art and against other types of ultra-long transmission amplification techniques. The second technique investigated involves asymmetrical, or offset, filtering. This technique is important because it deals with the strong filtering regimes that are a part of optical systems and networks in modern high-speed communications. It allows the improvement of the received signal by offsetting the central frequency of a filter after the output of a Delay Line Interferometer (DLI), which induces significant improvement in BER and/or Qvalues at the receiver and therefore an increase in signal quality. The experimental results are then concluded against the objectives of the experimental work and potential future work discussed.

Simultaneous multiple channel all-optical NRZ to CSRZ and RZ to CSRZ format conversion using an SOA-NOLM

The optical conversion bandwidth for an all-optical modulation format converter, based on a semiconductor laser amplifier in a nonlinear optical loop mirror (SOA-NOLM), is investigated. 4×10 Gbit/s channels are all-optically converted between both non-return-to-zero (NRZ) and return-to-zero (RZ) format to carrier-suppressed return-to-zero (CSRZ). WDM transmission of the converted signals over a 194 km fibre span is then demonstrated. The receiver sensitivity for the converted four wavelengths is measured and compared after transmission. © 2014 Elsevier B.V. All rights reserved.

Ultra-long laser cavities for non-repeated fibre transmission

We propose the use of ultra-long laser cavities for non-repeated fibre communication. We perform a comparison based on nonlinearity management theory between the performance of ultra-long cavities and other amplification schemes for non-repeated transmission.