Analysis of wave attenuation and shore protection of a bulk carrier ship performing as a detached floating breakwater

Análisis de la atenuación del oleaje por un carguero funcionando como dique flotante y aplicación a dos casos de protección portuaria y costera. The effectiveness of a bulk carrier working as a detached floating breakwater to protect a stretch of coast and form salients or tombolos is assessed in this paper. Experiments were conducted in the Madrid CEDEX facilities in a 30 m long, 3 m wide, 1/150 scale flume. The bulk carrier ship is 205 m long, 29 m wide and 18 m in height with a draught of 13 m, and has been subjected to irregular waves with significant heights from 2 m to 4 m and peak periods from 6 s to 12 s at a depth of 15 m, all prototype dimensions. Three probes were placed between the wave paddle and the ship to record incident and reflected waves and four probes were placed between the ship and the coastline to measure the transmitted waves. Transmission, reflection and dissipation coefficients (Ct, Cr, Cd) were calculated to determine wave attenuation. Results show good shelter in the lee of the ship with values of Ct under 0.5 for peak periods from 6 s to 11 s. In addition, forces on the mooring chains were measured showing maximum values of about 2000 tons at a 10 speak period. Finally, two analytical models were used to determine the shoreline’s response to the ship’s protection and to assess the possible forming of salients or tombolos. According to the results, salients - but not tombolos - are formed in all tests.

Dimerlike positional correlation and resonant transmission of electromagnetic waves in aperiodic dielectric multilayers

In this paper, we investigate transmission of electromagnetic wave through aperiodic dielectric multilayers. A generic feature shown is that the mirror symmetry in the system can induce the resonant transmission, which originates from the positional correlations (for example, presence of dimers) in the system. Furthermore, the resonant transmission can be manipulated at a specific wavelength by tuning aperiodic structures with internal symmetry. The theoretical results are experimentally proved in the optical observation of aperiodic SiO2/TiO2 multilayers with internal symmetry. We expect that this feature may have potential applications in optoelectric devices such as the wavelength division multiplexing system.

WDM of solitons in dispersion managed transmission systems

This thesis investigates the physical behaviour of solitons in wavelength division multiplexed (WDM) systems with dispersion management in a wide range of dispersion regimes. Background material is presented to show how solitons propagate in optical fibres, and key problems associated with real systems are outlined. Problems due to collision induced frequency shifts are calculated using numerical simulation, and these results compared with analytical techniques where possible. Different two-step dispersion regimes, as well as the special cases of uniform and exponentially profiled systems, are identified and investigated. In shallow profile, the constituent second-order dispersions in the system are always close to the average soliton value. It is shown that collision-induced frequency shifts in WDM soliton transmission systems are reduced with increasing dispersion management. New resonances in the collision dynamics are illustrated, due to the relative motion induced by the dispersion map. Consideration of third-order dispersion is shown to modify the effects of collision-induced timing jitter and third-order compensation investigated. In all cases pseudo-phase-matched four-wave mixing was found to be insignificant compared to collision induced frequency shift in causing deterioration of data. It is also demonstrated that all these effects are additive with that of Gordon-Haus jitter.

Surface acoustic wave devices with low loss and high frequency operation

This thesis describes an industrial research project carried out in collaboration with STC Components, Harlow, Essex. Technical and market trends in the use of surface acoustic wave (SAW) devices are reviewed. As a result, three areas not previously addressed by STC were identified: lower insertion loss designs, higher operating frequencies and improved temperature dependent stability. A review of the temperature performance of alternative lower insertion loss designs,shows that greater use could be made of the on-site quartz growing plant. Data is presented for quartz cuts in the ST-AT range. This data is used to modify the temperature performance of a SAW filter. Several recently identified quartz orientations have been tested. These are SST, LST and X33. Problems associated with each cut are described and devices demonstrated. LST quartz, although sensitive to accuracy of cut, is shown to have an improved temperature coefficient over the normal ST orientation. Results show that its use is restricted due to insertion loss variations with temperature. Effects associated with split-finger transducers on LST-quartz are described. Two low-loss options are studied, coupled resonator filters for very narrow bandwidth applications and single phase unidirectional transducers (SPUDT) for fractional bandwidths up to about 1%. Both designs can be implemented with one quarter wavelength transducer geometries at operating frequencies up to 1GHz. The SPUDT design utilised an existing impulse response model to provide analysis of ladder or rung transducers. A coupled resonator filter at 400MHz is demonstrated with a matched insertion loss of less than 3.5dB and bandwidth of 0.05%. A SPUDT device is designed as a re-timing filter for timing extraction in a long haul PCM transmission system. Filters operating at 565MHz are demonstrated with insertion losses of less than 6dB. This basic SPUDT design is extended to a maximally distributed version and demonstrated at 450MHz with 9.8dB insertion loss.

A new method for microwave generation and data transmission using DFB laser based on fiber Bragg gratings

A novel architecture for microwave/millimeter-wave signal generation and data modulation using a fiber-grating-based distributed feedback laser has been proposed in this letter. For demonstration, a 155.52-Mb/s data stream on a 16.9-GHz subcarrier has been transmitted and recovered successfully. It has been proved that this technology would be of benefit to future microwave data transmission systems.

A new method for microwave generation and data transmission using DFB laser based on fiber bragg gratings

A novel architecture for microwave/millimeter-wave signal generation and data modulation using a fiber-grating-based distributed feedback laser has been proposed in this letter. For demonstration, a 155.52-Mb/s data stream on a 16.9-GHz subcarrier has been transmitted and recovered successfully. It has been proved that this technology would be of benefit to future microwave data transmission systems. © 2006 IEEE.

Multi-level optimization of a fiber transmission system via nonlinearity management

linearity management is explored as a complete tool to obtain maximum transmission reach in a WDM fiber transmission system, making it possible to optimize multiple system parameters, including optimal dispersion pre-compensation, with fast simulations based on the continuous-wave approximation.

Impact of longitudinal power budget in coherent transmission systems employing digital back-propagation

We report the impact of longitudinal signal power profile on the transmission performance of coherently-detected 112 Gb/s m-ary polarization multiplexed quadrature amplitude modulation system after compensation of deterministic nonlinear fibre impairments. Performance improvements up to 0.6 dB (Q(eff)) are reported for a non-uniform transmission link power profile. Further investigation reveals that the evolution of the transmission performance with power profile management is fully consistent with the parametric amplification of the amplified spontaneous emission by the signal through four-wave mixing. In particular, for a non-dispersion managed system, a single-step increment of 4 dB in the amplifier gain, with respect to a uniform gain profile, at similar to 2/3(rd) of the total reach considerably improves the transmission performance for all the formats studied. In contrary a negative-step profile, emulating a failure (gain decrease or loss increase), significantly degrades the bit-error rate.

Impact of signal-ASE four-wave mixing on the effectiveness of digital back-propagation in 112 Gb/s PM-QPSK systems

Limitations in the performance of coherent transmission systems employing digital back-propagation due to four-wave mixing impairments are reported for the first time. A significant performance constraint is identified, originating from four-wave mixing between signals and amplified spontaneous emission noise which induces a linear increase in the standard deviation of the received field with signal power, and linear dependence on transmission distance.

Power pre-emphasis for suppression of FWM in coherent optical OFDM transmission

Four-wave-mixing (FWM) due to the fiber nonlinearity is a major limiting factor in coherent optical OFDM transmission. We propose to apply power pre-emphasis, i.e. to allocate the transmitted power nonuniformly among subcarriers in order to suppress the FWM impairment. The proposed technique was numerically investigated for both single channel 15.6 Gbs CO-OFDM transmissions and 7-channel WDM transmissions, showing that up to 1 dB improvement in the system's Qfactor can be achieved without considering sophisticated power loading algorithms developed for wireless communications. © 2014 Optical Society of America.

Impact of longitudinal power budget in coherent transmission systems employing digital back-propagation

We report the impact of longitudinal signal power profile on the transmission performance of coherently-detected 112 Gb/s m-ary polarization multiplexed quadrature amplitude modulation system after compensation of deterministic nonlinear fibre impairments. Performance improvements up to 0.6 dB (Q(eff)) are reported for a non-uniform transmission link power profile. Further investigation reveals that the evolution of the transmission performance with power profile management is fully consistent with the parametric amplification of the amplified spontaneous emission by the signal through four-wave mixing. In particular, for a non-dispersion managed system, a single-step increment of 4 dB in the amplifier gain, with respect to a uniform gain profile, at similar to 2/3(rd) of the total reach considerably improves the transmission performance for all the formats studied. In contrary a negative-step profile, emulating a failure (gain decrease or loss increase), significantly degrades the bit-error rate.

Multi-level optimization of a fiber transmission system via nonlinearity management

Nonlinearity management is explored as a complete tool to obtain maximum transmission reach in a WDM fiber transmission system, making it possible to optimize multiple system parameters, including optimal dispersion pre-compensation, with fast simulations based on the continuous-wave approximation. © 2006 Optical Society of America.

Performance comparison of 40 Gb/s ULH transmissions using CSRZ-ASK or CSRZ-DPSK modulation formats on Ultra Wave™ fiber

In this work we present extensive comparisons between numerical modelling and experimental measurements of the transmission performance of either CSRZ-ASK or CSRZ-DPSK modulation formats for 40-Gb/s WDM ULH systems on UltraWave™ fiber spans with all-Raman amplification. We numerically optimised the amplification and the signal format parameters for both CSRZ-DPSK and CSRZ-ASK formats. Numerical and experimental results show that, in a properly optimized transmission link, the DPSK format permits to double the transmission distance (for a given BER level) with respect to the ASK format, while keeping a substantial OSNR margin (on ASK modulation) after the propagation in the fiber line. Our comparison between numerical and experimental results permits to identify what is the most suitable BER estimator in assessing the transmission performance when using the DPSK format. © 2007 Optical Society of America.