New numerical model of stimulated Brillouin scattering in optical fibres with nonuniformity

A new numerical model which incorporates Brillouin shift frequency variations arising from fibre inhomogeneities has been developed for stimulated Brillouin scattering in optical fibres. This enables simulations of backscattered and transmitted power as functions of input power based only on known physical and material parameters as well as the polarisation factor and the measured Brillouin gain linewidth for the fibre. Agreement between modelled and experimental power characteristics for a CW input is excellent.

Picosecond soliton propagation using nonlinear optical loop mirrors as intensity filters

The authors show that by inserting nonlinear optical loop mirrors into an optical fibre transmission line, 1.5 ps solitons may be transmitted over at least 750 km, with amplifiers spaced at 15 km intervals.

Picosecond soliton transmission using concatenated nonlinear optical loop mirror intensity filters

We investigate the use of nonlinear optical loop mirrors as saturable absorbers in picosecond soliton transmission systems. It is found that they allow short (1–5-ps) pulses to be propagated through chains of optical amplifiers spaced at intervals of typically 10 km. The loop mirror removes dispersive waves and stabilizes the peak amplitude of the soliton. An additional advantage is that the self-frequency shift of the soliton may be suppressed by bandwidth filtering without causing growth of dispersive waves at the center of the passband. The timing jitter and soliton interactions present in the scheme are also described.

On the adoption decision and the intensity of use of complementary innovations: The intra firm diffusion of management practices across UK establishments

This paper contributes to the literature on the intra-firm diffusion of innovations by investigating the factors that affect the firm’s decision to adopt and use sets of complementary innovations. We define complementary innovations those innovations whose joint use generates super additive gains, i.e. the gain from the joint adoption is higher than the sum of the gains derived from the adoption of each innovation in isolation. From a theoretical perspective, we present a simple decision model, whereby the firm decides ‘whether’ and ‘how much’ to invest in each of the innovations under investigation based upon the expected profit gain from each possible combination of adoption and use. The model shows how the extent of complementarity among the innovations can affect the firm’s profit gains and therefore the likelihood that the firm will adopt these innovations jointly, rather than individually. From an empirical perspective, we focus on four sets of management practices, namely operating (OMP), monitoring (MMP), targets (TMP) and incentives (IMP) management practices. We show that these sets of practices, although to a different extent, are complementary to each other. Then, we construct a synthetic indicator of the depth of their use. The resulting intra-firm index is built to reflect not only the number of practices adopted but also the depth of their individual use and the extent of their complementarity. The empirical testing of the decision model is carried out using the evidence from the adoption behaviour of a sample of 1,238 UK establishments present in the 2004 Workplace Employment Relations Survey (WERS). Our empirical results show that the intra-firm profitability based model is a good model in that it can explain more of the variability of joint adoption than models based upon the variability of adoption and use of individual practices. We also investigate whether a number of firm specific and market characteristics by affecting the size of the gains (which the joint adoption of innovations can generate) may drive the intensity of use of the four innovations. We find that establishment size, whether foreign owned, whether exposed to an international market and the degree of homogeneity of the final product are important determinants of the intensity of the joint adoption of the four innovations. Most importantly, our results point out that the factors that the economics of innovation literature has been showing to affect the intensity of use of a technological innovation do also affect the intensity of use of sets of innovative management practices. However, they can explain only a small part of the diversity of their joint adoption use by the firms in the sample.

Experimental and theoretical investigations of intensity-modulation and direct-detection optical fast-OFDM over MMF-links

We demonstrate the first experimental implementation of a 3.9-Gb/s differential binary phase-shift keying (DBPSK)-based double sideband (DSB) optical fast orthogonal frequency-division-multiplexing (FOFDM) system with a reduced subcarrier spacing equal to half the symbol rate over 300m of multimode fiber (MMF) using intensity-modulation and direct-detection (IM/DD). The required received optical power at a bit-error rate (BER) of 10(-3) was measured to be similar to -14.2 dBm with a receiver sensitivity penalty of only similar to 0.2 dB when compared to the back-to-back case. Experimental results agree very well with the theoretical predictions.

The influence of emotional intensity on facial emotion recognition in disordered eating

Significant facial emotion recognition (FER) deficits have been observed in participants exhibiting high levels of eating psychopathology. The current study aimed to determine if the pattern of FER deficits is influenced by intensity of facial emotion and to establish if eating psychopathology is associated with a specific pattern of emotion recognition errors that is independent of other psychopathological or personality factors. Eighty females, 40 high and 40 low scorers on the Eating Disorders Inventory (EDI) were presented with a series of faces, each featuring one of five emotional expressions at one of four intensities, and were asked to identify the emotion portrayed. Results revealed that, in comparison to Low EDI scorers, high scorers correctly recognised significantly fewer expressions, particularly of fear and anger. There was also a trend for this deficit to be more evident for subtle displays of emotion (50% intensity). Deficits in anger recognition were related specifically to scores on the body dissatisfaction subscale of the EDI. Error analyses revealed that, in comparison to Low EDI scorers, high scorers made significantly more and fear-as-anger errors. Also, a tendency to label anger expressions as sadness was related to body dissatisfaction. Current findings confirm FER deficits in subclinical eating psychopathology and extend these findings to subtle expressions of emotion. Furthermore, this is the first study to establish that these deficits are related to a specific pattern of recognition errors. Impaired FER could disrupt normal social functioning and might represent a risk factor for the development of more severe psychopathology.

Export propensity, export intensity and firm performance:the role of the entrepreneurial founding team

We investigate how the characteristics and experience of the entrepreneurial founding team (EFT) affect the export orientation and subsequent performance of the businesses they establish, while allowing for the mutually reinforcing relationship between exporting and productivity. Using a sample of UK technology-based firms, we hypothesise and confirm that the set of EFT human capital needed for entering export markets is different from that required for succeeding in export markets. Commercial and managerial experience helps firms become exporters, but once over the exporting hurdle it is education, both general and specific, that has a substantially positive effect. The overall pattern of human capital effects on productivity is similar to those for export propensity. We also find evidence that productive firms are more likely both to enter export markets and to be export intensive, and that exporting boosts subsequent firm productivity.