Optimizations and investigations for transfer learning of iteratively pruned neural network equalizers for data center networking.

In this work, for the first time to the best of our knowledge, we introduce the iterative pruning technique into the transfer learning (TL) of neural network equalizers (NNE) deployed in optical links with different length. For the purpose of time saving during the training period of NNE, TL migrates the NNE parameters which have been already trained on the source link to the newly-routed link (the target link), which has been proved to outperform the training initialized with the random state. Based on simulations, we proved that iterative pruning technique could further enhance the convergence speed during TL between the source and target links. Moreover, we quantitatively investigate the marginal effects of pruned threshold and pruned span on the convergence performance in various transmission distance scenarios. In addition, we observed a trade-off between performance stability and complexity of NNE, which requires to be optimized compromisingly by choosing an appropriate equalizer scale.

Complex-valued decision feedback equalizer for optical IMDD signals with adaptive manipulations in time and amplitude domains.

In this work, we innovatively equalize optical intensity-modulated and directly detected (IMDD) four-level pulse amplitude modulation (PAM-4) signals using a complex-valued decision feedback equalizer (CDFE). Through mapping adjacent symbols of PAM-4 signals onto the complex domain, the influence of strongest inter-symbol interference (ISI) can be alleviated during the decision process in a decision feedback equalizer (DFE), effectively combating burst-error propagation when signals are noisy. Moreover, signal-adaptive manipulations of DFE parameters in both the time and the amplitude domain are performed by using an ultra-stable timing recovery and level-adaptive decision. Performance evaluations are made on vertical cavity surface emitting laser (VCSEL) modulated and multimode fiber (MMF) transmitted 100-Gbit/s optical PAM-4 signals. Based on experimental results of the short-reach optical communication, the proposed DFE outperforms the traditional DFE with a 0.5-dB system power budget gain at the 7% overhead (OH) forward error correction (FEC) bit error rate (BER) threshold.

Low-latency and efficient retiming and equalizing scheme for a 112-Gbps bandwidth-limited optical PAM-4 system.

The bandwidth limitation of optoelectronic devices is a key constraint for realizing higher capacity short-reach optical communication systems. In this work, we show that the performance of the timing recovery algorithm will significantly impact the performance of bandwidth-limited optical PAM-4 signals. To address this problem, we introduce a moving average filter (MAF) into the Gardner retiming loop to realize ultra-stable retiming without any pilot symbols. It enables a significantly reduced timing jitter, especially for bandwidth-limited conditions. Based on simulations, we show that the proposed retiming scheme will give a stable sampling phase, which is beneficial to the performance of the decision feedback equalizer. Compared to the system based on the traditional Gardner timing synchronization algorithm, the 2-dB power budget gain is realized. The proposed method improves the equalization performance of short-reach optical communication systems where complexity and processing latency are important concerns.

Clinical outcomes of percutaneous or surgical closure of ruptured sinus of Valsalva aneurysm.

OBJECTIVE: To evaluate the clinical efficacy, safety, and long-term outcomes of percutaneous closure (PC) and surgical repair of ruptured sinus of Valsalva aneurysm (RSVA). METHODS: Eighty-five consecutive patients with RSVA were included in this study. Patients were considered candidates for PC if they met the criterion, surgical repair was performed on patients who were unsuitable or failed PC. Of them, 30 patients underwent PC, while the other 55 patients had surgical repair. RESULTS: RSVA was successfully occluded in 29 of 30 patients who were treated by PC. The mean narrowest diameter at the ruptured site was 6.45 ± 1.60 mm measured by aortography. One patient developed serious occluder-related aortic regurgitation and underwent surgery. The success rate of the interventional approach was 96.7%. In the surgical group, 23 patients underwent repair of combined RSVA and ventricular septal defect. The hospital mortality rate of the surgical approach was 3.57%. During a median follow-up of 83 months (8-152 months), the improvement in NYHA functional class in the PC group was significantly greater than those in the surgical group (P < .01). One patient died of infective endocarditis in the surgical group. There were no further serious complications. CONCLUSIONS: PC is a safe alternative to surgical repair for patients with isolated RSVA. Surgical repair is more suitable for those who have multiple cardiac lesions requiring surgical treatment or failed PC.

Acute effects of Rho-kinase inhibitor fasudil on pulmonary arterial hypertension in patients with congenital heart defects.

BACKGROUND: We investigated the acute vasodilator effects of i.v. fasudil, a specific Rho-kinase inhibitor, on pulmonary circulation in patients with congenital heart defects (CHD) and severe pulmonary arterial hypertension (PAH). METHODS AND RESULTS: Thirty-five patients (34.23±12.10 years old) with CHD and severe PAH were consecutively enrolled. All patients underwent heart catheterization. At baseline and 30 min after initiation of i.v. fasudil, the following hemodynamic parameters were measured and calculated: right atrial pressure, pulmonary and systemic artery pressure (PAP and SAP), pulmonary and systemic vascular resistance, pulmonary-to-systemic blood pressure ratio (Pp/Ps), pulmonary-to-systemic blood flow ratio (Qp/Qs), cardiac index (CI) and artery oxygen saturation (SaO2). After fasudil treatment, marked decrease in mean PAP (mPAP), pulmonary vascular resistance (PVR), total pulmonary resistance, pulmonary-to-systemic vascular resistance ratio (Rp/Rs) and mean Pp/Ps (mPp/Ps) was found, while Qp/Qs increased significantly without affecting CI and SAP. mPAP, PVR, Rp/Rs and Qp/Qs tended to be improved more significantly in the post-tricuspid shunt group compared with the pre-tricuspid shunt group. CONCLUSIONS: Fasudil was well tolerated in patients with CHD and severe PAH, and significantly reduced PAP and PVR without affecting CI, SAP or SaO2.