Monolithic Directly-Modulated Multi-Wavelength- Channel GaInAsP/InP Micro-Ring Laser Array

Two directly-modulated GaInAsP/InP micro-rings with different radii vertically-coupled on a common bus are assessed for both independent and simultaneous operation. A device area <0.12mm^2 per microring allows the generation of 2λx1Gb/s WDM signals with 6nm wavelength separation. These show successful transmission over 25km of single-mode-fibre with < 0.2dB power penalty

Modelling of thermal behaviour of iron oxide layers on boiler tubes

Slender boiler tubes are subject to localised swelling when they are expose to excessive heat. The latter is due to the formation of an oxide layer, which acts as an insulation barrier. This excessive heat can lead to microstructural changes in the material that would reduce the mechanical strength and would eventually lead to critical and catastrophic failure. Detecting such creep damage remains a formidable challenge for boiler operators. It involves a costly process of shutting down the plant, performing electromagnetic and ultrasonic non-destructive inspection, repairing or replacing damaged tubes and finally restarting the plant to resume its service. This research explores through a model developed using a finite element computer simulation platform the thermal behaviour of slender tubes under constant temperature exceeding 723 \K. Our simulation results demonstrate that hematite layers up to 15 \μm thickness inside the tubes do not act as insulation. They clearly show the process of long term overheating on the outside of boiler tubes which in turn leads to initiation of flaws

An ICT-Enabled Approach to Optimising the Reliability of Manual Ultrasonic Non-Destructive Testing

Manual Ultrasonic Testing (MUT) is the most cost effective NDT method for the in-situ inspection of aerospace structures, in particular composite structures. However, its defect detection reliability is low. Manual Ultrasonic Testing (MUT) reports may vary depending on the operator conducting the test. Its reliability is therefore greatly influenced by human factors. Nonetheless, MUT continues to play a key role in the NDT suite of techniques. Despite its simplicity, it often meets the required performance at a reduced cost. No mechanised system exists which is as dextrous as the human hand for moving a probe over complex shapes while also dynamically skewing the probe to achieve the maximum amplitude from a reflector. It is therefore worth looking at ways to improve the reliability of MUT

Collision Evaluation in Low Power Wide Area Networks

This paper presents a performance evaluation of intercell interference and packets collision in scalable Low Power Wide Area Networks (LPWANs). The collision problem is one of the most critical challenges in LPWANs because it can substantially affect network performance and reliability. The paper also offers a rigorous and flexible mathematical model for the ALOHA-based random access protocol with the support of multiple groups of devices and multiple message copies. The analysis is based on the worst-case scenario of message collision, which calculates the message lost ratio (MLR) by assuming that even a weak overlap between two packets in the time-frequency domain leads to the loss of both. Simulations of Weightless-N and Sigfox LPWAN technologies using a variable number of devices, message copies, payload, transmission time, and channels offer some fresh insights into the LPWANs performance. For example, increasing the number message copies reduces the MLR but only up to a certain number of connected devices. After which, the redundancy in packet transmission is no longer beneficial

Eddy current analysis of shipped stainless steel heat exchanger bundle

In this paper, we present the results of a failure analysis done on new heat exchangertubes, which shows loss of thickness during a EC inspection to establish a prior loss of thickness base line aiming guarantee fitness for service during its working life. The root cause analysis indicates that there is intergranular corrosion due a differential concentration caused by seawater evaporation inside the tubes during the ship transit from the port of origin in China to the destination port in Brazil. The intergranular corrosion depth showed by root cause failure analysis is smaller than that showed by EC inspection. We attribute the EC inspection results deviation to a tube magnetisation due to mechanical stress and to a secondary phase due to an incomplete solubilisation after tube conforming and welding. Traditionally, these tubes are visually inspected and deemed acceptable but our conclusions reveal that eddy current testing is capable of detecting some corrosion anomalies which makes the tubes unfit for service

Directly modulated wavelength-multiplexed integrated microring laser array

The first demonstration of a directly modulated microring laser array is presented for on-off keyed, wavelength- division- multiplexed fiber-optic data transmission. GaInAsP-InP microring resonators oscillating at separate wavelengths in the 1.5-μm band are vertically coupled to a common passive waveguide bus, which is fabricated on the reverse side of the InP membrane. Two microrings defined with radii for a wavelength channel separation of 6 nm have been assessed for both individual and simultaneous operation. Negligible power penalty (<0.2 dB) is observed for wavelength-division-multiplexed operation with and without transmission over a 25-km fiber span in a manner which indicates low crosstalk between the integrated sources. A device area of less than 0.12 mm2 per microring on a common passive bus allows a highly scalable solution for short-reach wavelength-multiplexed links. © 2008 IEEE

Monolithic directly-modulated multi-wavelength-channel GalnAsP/InP micro-ring laser array

Two directly-modulated GalnAsP/InP micro-rings with different radii vertically-coupled on a common bus are assessed for both independent and simultaneous operation. A device area <0.12mm 2 per microring allows the generation of 2λ- xlGb/s, WDM signals with 6nm wavelength separation. These show successful transmission over 25km of single-mode-fibre with < 0.2dB power penalty

Monolithic directly-modulated multi-wavelength-channel GalnAsP/InP micro-ring laser array

\u3cp\u3eTwo directly-modulated GalnAsP/InP micro-rings with different radii vertically-coupled on a common bus are assessed for both independent and simultaneous operation. A device area &lt;0.12mm \u3csup\u3e2\u3c/sup\u3e per microring allows the generation of 2λ- xlGb/s, WDM signals with 6nm wavelength separation. These show successful transmission over 25km of single-mode-fibre with &lt; 0.2dB power penalty.\u3c/p\u3

Directly modulated wavelength-multiplexed integrated microring laser array

The first demonstration of a directly modulated microring laser array is presented for ON-OFF keyed, wavelength- division-multiplexed fiber-optic data transmission. GaInAsP–InP microring resonators oscillating at separate wavelengths in the 1.5-m band are vertically coupled to a common passive wave-guide bus, which is fabricated on the reverse side of the InP membrane. Two microrings defined with radii for a wavelength channel separation of 6 nm have been assessed for both individual and simultaneous operation. Negligible power penalty (0.2 dB ) is observed for wavelength-division-multiplexed operation with and without transmission over a 25-km fiber span in a manner which indicates low crosstalk between the integrated sources. A device area of less than 0.12 mm per microring on a common passive bus allows a highly scalable solution for short-reach wavelength-multiplexed links