Duty cycle optimization in a wavelength allocated WDM transmission with narrow asymmetric VSB filtering

We investigate the impact of a duty cycle on a wavelength allocated transmission at 40 Gbit/s with narrow, off-centre, optical filtering. We also study how the shape of the off-centred VSB filter affects the performance of the optical system. © 2004 Elsevier Inc. All rights reserved.

Optimal duty cycle and asymmetric VSB filtering in a wavelength allocated DWDM CS-RZ transmission

Impact of duty cycle on the optimisation of ultra-narrow VSB filtering in wavelength allocated CS-RZ Nx40Gbit/s DWDM transmission is investigated. A feasibility has been confirmed of over 600 km with 0.64 bit/s/Hz spectral efficiency.

Practical photovoltaic simulator with a cross tackling control strategy based on the first-hand duty cycle processing

This paper proposes a methodological scheme for the photovoltaic (PV) simulator design. With the advantages of a digital controller system, linear interpolation is proposed for precise fitting with higher computational efficiency. A novel control strategy that directly tackles two different duty cycles is proposed and implemented to achieve a full-range operation including short circuit (SC) and open circuit (OC) conditions. Systematic design procedures for both hardware and algorithm are explained, and a prototype is built. Experimental results confirm an accurate steady state performance under different load conditions, including SC and OC. This low power apparatus can be adopted for PV education and research with a limited budget.

Apodisation of photo-induced waveguide gratings using double-exposure with complementary duty cycles

We present a novel apodisation scheme for photo-induced waveguide gratings. The apodisation is implemented with double exposures that have reversely varying duty cycles. We have successfully applied the proposed scheme to remove the sidelobes of long period gratings (LPGs). We also observed for the first time super strong sidelobes in LPGs when creating them with only a single varying-duty-cycle exposure. The strong sidelobes can be well explained with a Mach-Zehnder interference model.

Apodisation of photo-induced waveguide gratings using double-exposure with complementary duty cycles

We present a novel apodisation scheme for photo-induced waveguide gratings. The apodisation is implemented with double exposures that have reversely varying duty cycles. We have successfully applied the proposed scheme to remove the sidelobes of long period gratings (LPGs). We also observed for the first time super strong sidelobes in LPGs when creating them with only a single varying-duty-cycle exposure. The strong sidelobes can be well explained with a Mach-Zehnder interference model.

Effect of pulsed current on the electrodeposition of chromium and copper

This research was concerned with the effects of pulsed current on the electrodeposition of chromium and copper. In the case of the latter metal, a novel application has been studied and a theory proposed for the ability to improve throwing power by the joint use of organic additives and pulsed reverse current. During the course of the research, several improvements were made to the pulse plating unit.Chromium. A study was made of the effect of square wave pulsed current on various physical properties of deposits from three hard chromium plating electrolytes. The effect of varying frequency at a duty cycle of 50% on the mean bulk internal stress, visual appearance, hardness, crack characteristics and surface topography of the electrodeposits was determined. X-ray diffraction techniques were used to study the phases present in the deposits. The effect of varying frequency on the cathodic efficiencies of the electrolytes was also determined. It was found that pulsed current reduced the internal stress of deposits from the sulphate catalysed electrolyte. It also reduced or eliminated cracking of deposits and reduced deposit brightness. Under certain conditions, pulsed current was found to induce the co-deposition of hydrides of chromium. Deposit hardness was found to be reduced by the use of pulsed current. Cathodic efficiencies of the high efficiency electrolytes were reduced by use of pulsed current although this effect was minimised at high frequencies. The sulphate catalysed electrolyte showed an increase in efficiency over the frequency range where hydrides were co-deposited.Copper. The polarisation behaviour of acid copper solutions containing polyethers, sulphopropyl sulphides and chloride ions was studied using both direct and pulse reverse current. The effect of these additives on the rest potentials of copper deposits immersed in the electrolyte was also studied. Hole Throwing Power on printed circuit boards was determined using a specially designed test cell. The effect of pulsed reverse current on the hole throwing power of commercially produced printed circuit boards was also studied. Polyethers were found to have an inhibiting effect on the deposition of copper whereas the sulphopropyl sulphides produced a stimulating (i.e. depolarising) effect. Studies of rest potentials made when both additives were present indicated that the sulphopropyl sulphide was preferentially adsorbed. The use of pulsed reverse current in solutions containing both polyether and sulphopropyl sulphide was found to cause desorption of the sulphopropyl sulphide at the cathode surface. Thus, at higher current densities, the inhibiting effect of the polyether produced an increase in the cathodic polarisation potential. At lower current densities, the depolarisation effect of the sulphopropyl sulphide could still occur. On printed circuit boards, this effect was found to produce an increase in the `hole throwing power' due to depolarisation of the holes relative to the surface of the boards. Typically, using direct current, hole/surface thickness ratios of 40% were obtained when plating 0.6 mm holes in a 3.2 mm thick board at a current density of 3 A/dm2 whereas using pulsed reverse current, ratios of 80% could be obtained at an equivalent rate of deposition. This was observed both in laboratory tests and on commercially plated boards.

40 Gbit/s asynchronous digital optical regenerator

We present the first experimental demonstration of an asynchronous digital optical regenerator at 42.67 Gbit/s. The system effectively retimes incoming asynchronous data bursts to a local clock without burst mode clock recovery and converts the signal to a desired wavelength and duty cycle.

Comparison of BER estimation methods in numerical simulation of 40 Gbit/s RZ-DPSK transmission

This study analyzes the validity of different Q-factor models in the BER estimation in RZ-DPSK transmission at 40 Gb/s channel rate. The impact of the duty cycle of the carrier pulses on the accuracy of the BER estimates through the different models has also been studied.

Comparative analysis of BER estimation methods in numerical simulation of 40-Gb/s RZ-DPSK transmission with in-line SOAs

Applying direct error counting, we compare the accuracy and evaluate the validity of different available numerical approaches to the estimation of the bit-error rate (BER) in 40-Gb/s return-to-zero differential phase-shift-keying transmission. As a particular example, we consider a system with in-line semiconductor optical amplifiers. We demonstrate that none of the existing models has an absolute superiority over the others. We also reveal the impact of the duty cycle on the accuracy of the BER estimates through the differently introduced Q-factors.

Enhanced spectral sensitivity of fibre long period gratings to refractive index of aqueous solutions utilising copper patterned coatings

A set of long period grating devices have been fabricated in photosensitive single mode fibre coated with a series of copper rings (period of 380μm, 50% duty cycle and length of 4cm). The long period gratings were inscribed with a uniform UV-laser exposure across the entire length of the copper ring patterned coating. The devices ranged in copper thickness from 0.5μm to 1.5μm. In addition, a control long period grating was fabricated in the same type of fibre with the same period for comparison. The refractive index and temperature spectral sensitivity of these devices were investigated and it was found that the index and temperature sensitivity is a function of the thickness of the copper rings, as supported by theoretical modelling. Furthermore, the index sensitivity of these devices in the 1.333 index region is greater than the control long period grating. The patterned 0.5μm coated long period grating gave a sensitivity of Δλ/Δn = -74 nm leading to a resolution of 1.4×10-3 compared to the control which had a sensitivity of Δλ/Δn = -32 nm with a resolution of 3.2×10-3 in the index region of 1.320 to 1.380 (aqueous solution regime). This demonstrates a two fold increase in the sensitivity. This novel fibre long period grating device shows potential for increasing the resolution of measurements of the index of aqueous solutions.

Bit-error rate performance of 20 Gbit/s WDM RZ-DPSK non-slope matched submarine transmission systems

Applying direct error counting, we assess the performance of 20 Gbit/s wavelength-division multiplexing return-to-zero differential phase-shift keying (RZ-DPSK) transmission at 0.4 bit/(s Hz) spectral efficiency for application on installed non-zero dispersion-shifted fibre based transoceanic submarine systems. The impact of the pulse duty cycle on the system performance is investigated and the reliability of the existing theoretical approaches to the BER estimation for the RZ-DPSK format is discussed.

Comparison of BER estimation methods in numerical simulation of 40 Gbit/s RZ-DPSK transmission

This study analyzes the validity of different Q-factor models in the BER estimation in RZ-DPSK transmission at 40 Gb/s channel rate. The impact of the duty cycle of the carrier pulses on the accuracy of the BER estimates through the different models has also been studied.

Comparative analysis of BER estimation methods in numerical simulation of 40-Gb/s RZ-DPSK transmission with in-line SOAs

Applying direct error counting, we compare the accuracy and evaluate the validity of different available numerical approaches to the estimation of the bit-error rate (BER) in 40-Gb/s return-to-zero differential phase-shift-keying transmission. As a particular example, we consider a system with in-line semiconductor optical amplifiers. We demonstrate that none of the existing models has an absolute superiority over the others. We also reveal the impact of the duty cycle on the accuracy of the BER estimates through the differently introduced Q-factors. © 2007 IEEE.

All-optical 42.6 Gbit/s NRZ to RZ format conversion by cross-phase modulation in single SOA

A 42.6 Gbit/s all-optical non-retum-to-zero (NRZ) to return-to-zero (RZ) format converter using a single SOA followed by an asymmetrical Mach-Zehnder interferometer is presented. The format converter generates a correctly-coded RZ signal with a controllable duty-cycle. It has the advantages of flexible input N RZ wavelength, preserved input polarity, negative bit error rate power penalty and low switching pulse energy (15fJ).

Effect of carrier reshaping and narrow MUX-DEMUX filtering in 0.8 bit/s/Hz WDM RZ-DPSK transmission

Effect of the carrier shape in the ultra high dense wavelength division multiplexing (WDM) return to zero differential phase shift keying (RZ-DPSK) transmission has been examined through numerical optimization of the pulse form, duty cycle and narrow multiplex/de-multiplex (MUX/DEMUX) filtering parameters. © 2007 Springer Science+Business Media, LLC.