A comparative study of DPSK and OOK WDM transmission over transoceanic distances and their performance degradations due to nonlinear phase noise

We have compared experimentally the transmission performance of return-to-zero differential phase-shift keying (RZ-DPSK) with RZ-ON-OFF keying (OOK), nonreturn-to-zero differential phase-shift keying (NRZ-DPSK), and NRZ-OOK for 100/spl times/10-Gb/s transmission with a spectral efficiency of 0.22 b/s/Hz over transoceanic distances. The Q degradation of the RZ-DPSK after transmission over 9180 km was 3 dB greater than that of RZ-OOK. The experimental results clearly showed the major cause of degradation for DPSK is not cross-phase modulation but self-phase modulation. The calculated nonlinear phase noise, i.e., the Gordon-Mollenauer effect, agreed with the experimental results. A distributed-Raman-amplifier assisted erbium-doped-fiber-amplified transmission line acted well in reducing the nonlinear phase noise.     

Super-multi-fibre PLC connector utilising angled connection between PLC and tens of fibres

A novel super-multi-fibre planar lightwave circuit (PLC) connector, designed to connect tens of optical fibres and a PLC for super-multichannel PLC-based optical modules with a receptacle interface, is proposed. This connector employs an angled connection instead of a PC connection. A 0.127 mm pitch 32-fibre connector is also demonstrated, which exhibits low connection and high return losses.     

1-GHz-spaced 16-channel arrayed-waveguide grating for a wavelength reference standard in DWDM network systems

We fabricated a 1-GHz-spaced 16-channel arrayed-waveguide grating (AWG) by using a new AWG configuration where the path of each arrayed waveguide winds backward and forward across a 4-in diameter wafer without crossing any other waveguides. The ultra-narrow (< 1 GHz) and stable transmission bands of this AWG can be used to construct a wavelength reference standard covering the S, C, and L bands in the dense wavelength-division-multiplexing network systems whose frequency deviation is /spl plusmn/160 MHz.     

Real-time measurement of pointing action by using DSP

This paper presents an approach of measuring in real-time the vector of finger that is pointing to an object. DSP is used in the operation processing unit in order to do the real-time processing. The steps include the extraction of flesh-colored regions from an image, the labeling of the flesh-colored regions, and the detection of two characteristic positions on the finger so that the direction that the finger is pointing at will be calculated. The entire process takes about 29 msec, which makes it possible to have the frame rate of 34 fps. With this frame rate, this measurement approach is considered real-time and promising to be merged into other application systems. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

A Model of the Relationship Between Psychosocial Variables and Diurnal Cortisol Rhythm Under Chronic Stress by Using Structural Equations

By using structural equations, we investigated the effect of chronic stress on salivary cortisol rhythm and proposed a causal model of chronic stress by using psychosocial and physiological data. First, 111 healthy workers (48 males, 63 females) completed questionnaires on chronic stress and lifestyle habits. Then, they provided saliva samples and answered questionnaires that were prepared to assess their psychological states 5 times (on waking up and at 10:00, 11:40, 14:00, and 16:00) on workdays. Structural equation modeling (SEM) revealed that chronic stress and longer commuting time resulted in sleep irregularities and this disrupted the cortisol circadian rhythm. This suggests that chronic stress disrupts the cortisol circadian rhythm even in healthy individuals, and sleep regularity mediates the effect of chronic stress on the cortisol rhythm.

     

Evaluation of myocardial damage using 123I-BMIPP imaging in patients with vasospastic angina

The purpose of this study is to determine whether left ventricular dysfunction following coronary artery spasm by 123I-BMIPP myocardial imaging. To reveal the clinical efficacy of 123I-BMIPP SPECT, 20 patients with vasospastic angina were studied using resting, 3-hour delayed image with 123I-BMIPP and exercise, 3-hour delayed image with 201Tl SPECT. 123I-BMIPP uptake was decreased compared to 201Tl (discordant) in 12 patients (60%) and in 49/100 myocardial segments (49%). The extent and severity score in resting image with 123I-BMIPP were significantly larger than that in delayed image with 201Tl (p < 0.01). In 123I-BMIPP SPECT, the severity score in the latest ischemia were significantly larger than that in others. The incidence of a complete agreement of decreased 123I-BMIPP uptake and coronary artery spasm was significantly higher (75%) than that in 201Tl (28%, p < 0.01). Furthermore, compared to 201Tl uptake, decreased 123I-BMIPP uptake much more corresponded to reduced wall motion in 9 of patients with mismatching. The severity of regional wall motion abnormality was significantly correlated with severity score of 123I-BMIPP. Late redistribution in delayed image with 123I-BMIPP was seen in 6 patients. The regional washout rate and the severity of regional wall motion abnormality in 6 patients was significantly lower than that in others (p < 0.05). Thus, metabolic abnormality assessed by 123I-BMIPP is well associated with left ventricular asynergy and spastic region in patients with vasospastic angina. In conclusion, 123I-BMIPP SPECT may sensitively delineate the impaired myocardium following coronary artery spasm, and it is very useful in diagnosing and estimating the severity of vasospastic angina.     

The temperature dependence of luminescence from a long-lasting phosphor exposed to ionizing radiation

The temperature dependence of luminescence from a long-lasting phosphor (LLP), SrAl₂O₄ : Eu²⁺,Dy³⁺, exposed to ionizing radiation has been measured to understand the LLP luminescence mechanism. Evaluation of the decay constants of the LLP exposed to -, β- or γ-rays at temperatures from 200 to 390 K showed that the decay constant is divided into four components ranging from 10⁻⁴ to 10⁻¹ s⁻¹ with activation energies of 0.02–0.35 eV.

Total luminous intensity from the LLP with changing irradiation temperature has its maximum value around the room temperature. Irradiation at elevated temperature (390 K) has the total luminescence pattern with monotonous decrease as temperature rises. As a result of evaluating the temperature dependence of luminescence, the luminescence mechanism is considered as follows:

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