Advanced manufacturing technology, work design, and performance:a change study

Two alternative work designs are identified for operators of stand-alone advanced manufacturing technology (AMT). In the case of specialist control, operators are limited to running and monitoring the technology, with operating problems handled by specialists, such as engineers. In the case of operator control, operators are given much broader responsibilities and deal directly with the majority of operating problems encountered. The hypothesis that operator control would promote better performance and psychological well-being than would specialist control (which is more prevalent) was tested in a longitudinal field study involving work redesign for operators of computer-controlled assembly machines. Change from specialist to operator control reduced downtime, especially for high-variance systems, and was associated with greater intrinsic job satisfaction and less perceived work pressure. The implications of these findings for both small and large-scale applications of AMT are discussed.

Femtosecond laser inscribed Bragg sensor in Terfenol-D coated optical fibre with ablated microslot for the detection of static magnetic fields

A novel device for the detection and characterisation of static magnetic fields is presented. It consists of a femtosecond laser inscribed fibre Bragg grating (FBG) that is incorporated into an optical fibre with a femtosecond laser micromachined slot. The symmetry of the fibre is broken by the micro-slot, producing non-uniform strain across the fibre cross section. The sensing region is coated with Terfenol-D making the device sensitive to static magnetic fields, whereas the symmetry breaking results in a vectorial sensor for the detection of magnetic fields as low as 0.046 mT with a resolution of ±0.3mT in transmission and ±0.7mT in reflection. The sensor output is directly wavelength encoded from the FBG filtering, leading to simple demodulation through the monitoring of wavelength shifts that result as the fibre structure changes shape in response to the external magnetic field. The use of a femtosecond laser to both inscribe the FBG and micro-machine the slot in a single stage, prior to coating the device, significantly simplifies the sensor fabrication.

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.

Multi-wavelength source using low drive-voltage amplitude modulators for optical communications

A simple and cost-effective technique for generating a flat, square-shaped multi-wavelength optical comb with 42.6 GHz line spacing and over 0.5 THz of total bandwidth is presented. A detailed theoretical analysis is presented, showing that using two concatenated modulators driven with voltages of 3.5 Vp are necessary to generate 11 comb lines with a flatness below 2dB. This performance is experimentally demonstrated using two cascaded Versawave 40 Gbit/s low drive voltage electro-optic polarisation modulators, where an 11 channel optical comb with a flatness of 1.9 dB and a side-mode-suppression ratio (SMSR) of 12.6 dB was obtained.

Performance comparison of 40 Gb/s ULH transmissions using CSRZ-ASK or CSRZ-DPSK modulation formats on UltraWave (TM) 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 (TM) 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. (c) 2007 Optical Society of America.

Correlations between optimal temporal width and spectral characteristics of an optical signal in a wavelength-paired CS-RZ transmission with high spectral efficiency

We examine the correlations between the parameters of ultra-narrow off-centred filtering and pulse width on the performance of a wavelength paired Nx40Gbit/s DWDM transmission, consisting of carrier suppressed return-to-zero signal with 0.64 bit/s/Hz (without polarization-division multiplexing) spectral efficiency.

Time domain all-optical signal processing at a RZ optical receiver

We propose a new all-optical signal processing technique to enhance the performance of a return-to-zero optical receiver, which is based on nonlinear temporal pulse broadening and flattening in a normal dispersion fiber and subsequent slicing of the pulse temporal waveform. The potential of the method is demonstrated by application to timing jitter-and noise-limited transmission at 40 Gbit/s. © 2005 Optical Society of America.

Was it good for them? Reflections on the use of MENTOR and changes in course design using general performance measures

This paper considers the use of general performance measures in evaluating specific planning and design decisions in higher education and reflects on the students' learning process. Specifically, it concerns the use of the MENTOR multimedia computer aided learning package for helping students learn about OR as part of a general business degree. It includes the transfer of responsibility for a learning module to a new staff member and a change from a single tutor to a system involving multiple tutors. Student satisfaction measures, learning outcome measures and MENTOR usage patterns are examined in monitoring the effects of the changes in course delivery. The results raise some questions about the effectiveness of general performance measures in supporting specific decisions relating to course design and planning.

Multiplexers and demultiplexers based on fibre Bragg gratings and optical circulators for DWDM systems

Two different architectures of multiplexers/demultiplexers based on 4×1 and 1×4 configurations are discussed. These architectures are implemented using apodized fibre Bragg gratings as optical filters and optical circulators. The spectral characteristics of the devices for channel separations of 100 GHz and 50 GHz are analysed and their performance is evaluated. Optical switch and cross-connect configurations are also demonstrated.

Optical burst-switched SSB-OFDM using a fast switching SG-DBR laser

The application of orthogonal frequency-division multiplexing (OFDM) in an optical burst-switched system employing a single fast switching sample grating-distributed Bragg reflector (SG-DBR) laser is demonstrated experimentally. The effect of filter profiles compatible with 50, 25, and 12.5 GHz wavelength-division multiplexing grids on the system is investigated with system performance examined in terms of error vector magnitude per subcarrier for OFDM burst data beginning at various times after a switching event. Additionally the placement of the OFDM training sequence within the data burst and its effect on the system is investigated.

Potential for broad range multiplexing of fibre Bragg gratings in polymer optical fibres and operation in the 700-nm wavelength range

Refractive index and structural characteristics of optical polymers are strongly influenced by the thermal history of the material. Polymer optical fibres (POF) are drawn under tension, resulting in axial orientation of the polymer molecular chains due to their susceptibility to align in the fibre direction. This change in orientation from the drawing process results in residual strain in the fibre and also affects the transparency and birefringence of the material (1-3). PMMA POF has failure strain as high as over 100%. POF has to be drawn under low tension to achieve this value. The drawing tension affects the magnitude of molecular alignment along the fibre axis, thus affecting the failure strain. The higher the tension the lower the failure stain will be. However, the properties of fibre drawn under high tension can approach that of fibre drawn under low tension by means of an annealing process. Annealing the fibre can generally optimise the performance of POF while keeping most advantages intact. Annealing procedures can reduce index difference throughout the bulk and also reduce residual stress that may cause fracture or distortion. POF can be annealed at temperatures approaching the glass transition temperature (Tg) of the polymer to produce FBG with a permanent blue Bragg wave-length shift at room temperature. At this elevated temperature segmental motion in the structure results in a lower viscosity. The material softens and the molecular chains relax from the axial orientation causing shrinking of the fibre. The large attenuation of typically 1dB/cm in the 1550nm spectral region of PMMA POF has limited FBG lengths to less than 10cm. The more expensive fluorinated polymers with lower absorption have had no success as FBG waveguides. Bragg grating have been inscribed onto various POF in the 800nm spectral region using a 30mW continuous wave 325nm helium cadmium laser, with a much reduced attenuation coefficient of 10dB/m (5). Fabricating multiplexed FBGs in the 800nm spectral region in TOPAS and PMMA POF consistently has lead to fabrication of multiplexed FBG in the 700nm spectral region by a method of prolonged annealing. The Bragg wavelength shift of gratings fabricated in PMMA fibre at 833nm and 867nm was monitored whilst the POF was thermally annealed at 80°C. Permanent shifts exceeding 80nm into the 700nm spectral region was attained by both gratings on the fibre. The large permanent shift creates the possibility of multiplexed Bragg sensors operating over a broad range. -------------------------------------------------------------------------------------------------------------------- 1. Pellerin C, Prud'homme RE, Pézolet M. Effect of thermal history on the molecular orientation in polystyrene/poly (vinyl methyl ether) blends. Polymer. 2003;44(11):3291-7. 2. Dvoránek L, Machová L, Šorm M, Pelzbauer Z, Švantner J, Kubánek V. Effects of drawing conditions on the properties of optical fibers made from polystyrene and poly (methyl methacrylate). Die Angewandte Makromolekulare Chemie. 1990;174(1):25-39. 3. Dugas J, Pierrejean I, Farenc J, Peichot JP. Birefringence and internal stress in polystyrene optical fibers. Applied optics. 1994;33(16):3545-8. 4. Jiang C, Kuzyk MG, Ding JL, Johns WE, Welker DJ. Fabrication and mechanical behavior of dye-doped polymer optical fiber. Journal of applied physics. 2002;92(1):4-12. 5. Johnson IP, Webb DJ, Kalli K, Yuan W, Stefani A, Nielsen K, et al., editors. Polymer PCF Bragg grating sensors based on poly (methyl methacrylate) and TOPAS cyclic olefin copolymer2011: SPIE.

Optical communications applications of ultra-long Raman fiber lasers

Recent work on ultra-long Raman fiber lasers has shown that it is possible to create quasi-lossless transmission conditions in fiber spans long enough to be considered for high speed optical communications. This paper reviews how quasi-lossless transmission conditions are reached and presents experimental results of 40Gb/s transmission in a quasi lossless system. The performance is compared with a conventional EDFA based system.

All-optical passive regeneration of 40 Gbit/s soliton data stream using dispersion management and in-line NOLMs

The feasibility of stable soliton transmission system was demonstrated using a practical dispersion map in conjunction with in-line nonlinear optical loop mirrors (NOLMs). The system's performance was examined at 40 Gbit/s data rate in terms of maximum propagation distance corresponding to a bit error rate of more than 10-9. The bit error rate was estimated by means of the standard Q-factor.

1-Tb/s DWDM long-haul transmission employing a fiber optical parametric amplifier

In this letter, we report the performance of a fiber optical parametric amplifier (OPA) when used as a source or intermediate node amplifier in a dense wavelength-division-multiplexed (DWDM) long-haul transmission testbed with 26 DWDM channels modulated at 43.7-Gb/s return-to-zero differential phase-shift keying. In both scenarios, we demonstrate similar performance to an erbium-doped fiber amplifier. This shows the OPAs compatibility with high-capacity (>1 Tb/s) long-haul communication systems.

Auto-solitons guided by in-line nonlinear optical loop mirrors in dispersion-managed communication systems

Summary form only given. Both dispersion management and the use of a nonlinear optical loop mirror (NOLM) as a saturable absorber can improve the performance of a soliton-based communication system. Dispersion management gives the benefits of low average dispersion while allowing pulses with higher powers to propagate, which helps to suppress Gordon-Haus timing jitter without sacrificing the signal-to-noise ratio. The NOLM suppresses the buildup of amplifier spontaneous emission noise and background dispersive radiation which, if allowed to interact with the soliton, can lead to its breakup. We examine optical pulse propagation in dispersion-managed (DM) transmission system with periodically inserted in-line NOLMs. To describe basic features of the signal transmission in such lines, we develop a simple theory based on a variational approach involving Gaussian trial functions. It, has already been proved that the variational method is an extremely effective tool for description of DM solitons. In the work we manage to include in the variational description the point action of the NOLM on pulse parameters, assuming that the Gaussian pulse shape is inherently preserved by propagation through the NOLM. The obtained results are verified by direct numerical simulations