40 Gbit/s soliton transmission over dispersion managed standard fibre links

Error free transmission of a single polarisation optical time division multiplexed 40 Gbit/s dispersion managed pulse data stream over 1009 km has been achieved in a dispersion compensated standard (non-dispersion shifted) fibre. This distance is twice the previous record at this data rate, and was acheived through techniques developed for dispersion managed soliton transmission.

1000 Km transmission of 40 Gbit/s single channel RZ data over dispersion managed standard (non-dispersion shifted) fibre

Error-free transmission of a single polarization optical time division multiplexed 40 Gbit/s dispersion managed pulse data stream over 1009 km has been achieved in dispersion-compensated standard (non-dispersion shifted) fibre. This distance is twice the previous record at this data rate.

10Gbit/s dispersion managed soliton transmission over 16,500km in standard fibre by reduction of soliton interactions

We show experimentally and numerically that in high-speed strongly dispersion-managed standard fiber soliton systems nonlinear interactions limit the propagation distance. We present results that show that the effect of these interactions can be significantly reduced by appropriate location of the amplifier within the dispersion map. Using this technique, we have been able to extend the propagation distance of 10-Gbit/s 231–1pseudorandom binary sequence soliton data to 16, 500km over standard fiber by use of dispersion compensation. To our knowledge this distance is the farthest transmission over standard fiber without active control ever reported, and it was achieved with the amplifier placed after the dispersion-compensating fiber in a recirculating loop.

40Gb/s dispersion managed soliton transmission over 1160km in standard fibre with a 75 km span length

It is shown that in strongly dispersion managed high bit rate systems it is important to correctly choose the pulse launch position. Using this technique error free transmission has been achieved of a 40 Gbit/s 231-1 nonlinear RZ PRBS over 1160 km in a dispersion compensated standard fibre propagation experiment with a 75 km standard fibre span

Transmission of non-uniform OTDM channels in nonlinearly-guided dispersion-managed fibre system

The effects of channel inequality on nonlinear signal switching in a nonlinear optical fiber loop mirror (NOLM) were investigated. It was found that the channel-to-channel amplitude differences in optical time division multiplexing (OTDM) have strong impact on swiching behavior of individual channels in a 2R regenerator. The optical pulses in different channels face either suppression of the amplitude noise or increase in noise, depending on the inter-channel amplitude difference. It was stated that appropriate control of the channel uniformity in the OTDM transmitters is required to support stable long-haul transmission in 2R regenerated systems.

The water use rates of reedbed and wet woodland habitats

To create hydrologically sustainable wetlands, knowledge of the water use requirements of target habitats must be known. Extensive literature reviews highlighted a dearth of water-use data associated with large reedbeds and wet woodland habitats and in response to this field experiments were established. Field experiments to measure the water use rates of large reedbeds [ET(Reed)] were completed at three sites within the UK. Reference Crop Evapotranspiration [ETo] was calculated and mean monthly crop coefficients [Kc(Reed)] were developed. Kc(Reed) was less than 1 during the growing season (March to September), ranging between 0.22 in March and reaching a peak of 0.98 in June. The developed coefficients compare favourably with published data from other large reedbed systems and support the premise that the water use of large reedbeds is lower than that from small/fringe reedbeds. A methodology for determining water use rates from wet woodland habitats (UK NVC Code: W6) is presented, in addition to provisional ET(W6) rates for two sites in the UK. Reference Crop Evapotranspiration [ETo] data was used to develop Kc(W6) values which ranged between 0.89 (LV Lysimeter 1) and 1.64 (CH Lysimeter 2) for the period March to September. The data are comparable with relevant published data and show that the water use rates of wet woodland are higher than most other wetland habitats. Initial observations suggest that water use is related to the habitat’s establishment phase and the age and size of the canopy tree species. A theoretical case study presents crop coefficients associated with wetland habitats and provides an example water budget for the creation of a wetland comprising a mosaic of wetland habitats. The case study shows the critical role that the water use of wetland habitats plays within a water budget.

The application of remote sensing to the management of urban wildlife habitats

The project set out with two main aims. The first aim was to determine whether large scale multispectral aerial photography could be used to successfully survey and monitor urban wildlife habitats. The second objective was to investigate whether this data source could be used to predict population numbers of selected species expected to be found in a particular habitat type. Panchromatic, colour and colour infra-red, 1:2500 scale aerial photographs, taken in 1981 and 1984, were used. For the orderly extraction of information from the imagery, an urban wildlife habitat classification was devised. This was based on classifications already in use in urban environments by the Nature Conservancy Council. Pilot tests identified that the colour infra-red imagery provided the most accurate results about urban wildlife habitats in the study area of the Blackbrook Valley, Dudley. Both the 1981 and 1984 colour infra-red photographs were analysed and information was obtained about the type, extent and distribution of habitats. In order to investigate whether large scale aerial photographs could be used to predict likely animal population numbers in urban environments, it was decided to limit the investigation to the possible prediction of bird population numbers in Saltwells Local Nature Reserve. A good deal of research has already been completed into the development of models to predict breeding bird population numbers in woodland habitats. These models were analysed to determine whether they could be used successfully with data extracted from the aerial photographs. The projects concluded that 1:2500 scale colour infra-red photographs can provide very useful and very detailed information about the wildlife habitats in an urban area. Such imagery can also provide habitat area data to be used with population predictive models of woodland breeding birds. Using the aerial photographs, further investigations into the relationship between area of habitat and the breeding of individual bird species were inconclusive and need further research.

Dissipative dispersion-managed solitons in mode-locked lasers

We extend the theory of dispersion-managed solitons to dissipative systems with a focus on mode-locked fiber lasers. Dissipative structures exist at high map strengths, leading to the generation of stable, short pulses with high energy. Two types of intramap pulse evolution are observed depending on the net cavity dispersion. These are characterized by a reduced model, and semianalytical solutions are obtained.

Dissipative nonlinear structures in optical fiber systems I : dissipative dispersion managed solitons in mode-locked lasers

In this first talk on dissipative structures in fiber applications, we extend theory of dispersion-managed solitons to dissipative systems with a focus on mode-locked fibre lasers. Dissipative structures exist at high map strengths leading to the generation of stable, short pulses with high energy. Two types of intra-map pulse evolutions are observed depending on the net cavity dispersion. These are characterized by a reduced model and semi-analytical solutions are obtained.

Dissipative dispersion managed solitons in mode-locked fibre lasers

We extend theory of dispersion-managed solitons to dissipative systems with a focus on mode-locked fibre lasers. Dissipative structures exist at high map strengths, and different pulse evolutions are observed depending on the net cavity dispersion.

Dispersion-managed solitons in fibre systems and lasers

Nonlinear systems with periodic variations of nonlinearity and/or dispersion occur in a variety of physical problems and engineering applications. The mathematical concept of dispersion managed solitons already has made an impact on the development of fibre communications, optical signal processing and laser science. We overview here the field of the dispersion managed solitons starting from mathematical theories of Hamiltonian and dissipative systems and then discuss recent advances in practical implementation of this concept in fibre-optics and lasers.

All-optical passive 2R regeneration of dispersion-managed RZ data at 40 and 80 Gbit/s using in-line NOLMs

We demonstrate that the use of in-line nonlinear optical loop mirrors (NOLMs) in dispersion-managed (DM) transmission systems dominated by amplitude noise can achieve passive 2R regeneration of a 40 and 80 Gbit/s RZ data stream. This is an indication that the use of this approach could obviate the need for full-regeneration in high data rate, strong DM systems, when intra-channel four-wave mixing poses serious problems.

Study of the operating regime for all-optical passive 2R regeneration of dispersion-managed RZ data at 40 Gb/s using in-line NOLMs

In this letter, we numerically demonstrate that the use of inline nonlinear optical loop mirrors in strongly dispersion-managed transmission systems dominated by pulse distortion and amplitude noise can achieve all-optical passive 2R regeneration of a 40-Gb/s return-to-zero data stream. We define the tolerance limits of this result to the parameters of the input pulses.