Performance of mode diversity reception of a polarization-division-multiplexed signal for free-space optical communication under atmospheric turbulence.

We investigated the performance of mode diversity reception of a polarization-division-multiplexed (PDM) signal with few-mode-fiber (FMF) coupling for high-speed free-space optical communications under atmospheric turbulence. Optical propagation through eigenmodes of a FMF yields coupling between different linearly polarized (LP) modes in orthogonal polarizations, which causes power imbalance and loss of the orthogonality of multiplexed signals within each individual LP mode. Due to this phenomenon, the architecture of mode diversity combining affects the receiver performance. We numerically simulated the power fluctuation coupled to each LP mode after atmospheric propagation and FMF propagation in the condition of an optical downlink from a low-Earth-orbital satellite to the ground. We found that full receiver-side multiple-input multiple-output (Rx-MIMO) architecture in three-mode diversity reception improved the performance by 5 dB compared with selection combining (SC) of signals decoded individually in LP modes, and that it mitigated the required transmitted power by 6 dB compared with reception with single mode fiber (SMF) coupling. We also experimentally confirmed in three-mode diversity reception of a 128 Gb/s PDM-quadrature phase-shift keying with a diffuser plate as a turbulence emulator, that full Rx-MIMO with adaptive filters could work under severe fading and that it outperformed SC.

[Administration of acute exacerbation of chronic obstructive pulmonary disease].

We have to consider the exacerbation of chronic obstructive pulmonary disease(COPD) may be caused not only by infection, but also by acute exacerbation of chronic heart failure, pulmonary embolism, pneumothorax, or other cardiopulmonary complications. Because it is characteristic that the exacerbation of COPD is often recurensive, the most important thing is the administration during stable status. Approximately 40% of pathogens of the acute infectious exacerbation of COPD are Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, Pseudomonas aeruginosa, Staphylococcus aureus, and Echelisia coli. Also, approximately 15% is exacerbated by atypical pathogens such as Chlamydia pneumoniae and approximately 30% is by viral infection. We should contemplate the possibility of pathogens according to the statistics, when we choose antibiotics empirically.