Low-Cost 400 Gbps DR4 Silicon Photonics Transmitter for Short-Reach Datacenter Application.

Targeting high-speed, low-cost, short-reach intra-datacenter connections, we designed and tested an integrated silicon photonic circuit as a transmitter engine. This engine can be packaged into an optical transceiver module which meets the QSFP-DD Form Factor, together with other electrical/optical components. We first present the design and performance of a high-speed silicon modulator, which had a 3-dB EO bandwidth of >40 GHz and an ER of >5 dB. We then incorporated the engine onto a test board and injected a 53.125 Gbaud PAM4 signal. Clear eye patterns were observed at the receiver with TDECQ ~3 dB for all four lanes.

Time-restricted feeding alleviates cardiac dysfunction induced by simulated microgravity via restoring cardiac FGF21 signaling.

Dietary restriction has been well-described to improve health metrics, but whether it could benefit pathophysiological adaptation to extreme environment, for example, microgravity, remains unknown. Here, we investigated the effects of a daily rhythm of fasting and feeding without reducing caloric intake on cardiac function and metabolism against simulated microgravity. Male rats under ad libitum feeding or time-restricted feeding (TRF; food access limited to 8 hours every day) were subjected to hindlimb unloading (HU) to simulate microgravity. HU for 6 weeks led to left ventricular dyssynchrony and declined cardiac function. HU also lowered pyruvate dehydrogenase (PDH) activity and impaired glucose utilization in the heart. All these were largely preserved by TRF. TRF showed no effects on HU-induced loss of cardiac mass, but significantly improved contractile function of cardiomyocytes. Interestingly, TRF raised liver-derived fibroblast growth factor 21 (FGF21) level and enhanced cardiac FGF21 signaling as manifested by upregulation of FGF receptor-1 (FGFR1) expression and its downstream markers in HU rats. In isolated cardiomyocytes, FGF21 treatment improved PDH activity and glucose utilization, consequently enhancing cell contractile function. Finally, both liver-specific knockdown (KD) of FGF21 and cardiac-specific FGFR1 KD abrogated the cardioprotective effects of TRF in HU rats. These data demonstrate that TRF improves cardiac glucose utilization and ameliorates cardiac dysfunction induced by simulated microgravity, at least partially, through restoring cardiac FGF21 signaling, suggesting TRF as a potential countermeasure for cardioprotection in long-term spaceflight.

α-Linolenic acid but not linolenic acid protects against hypertension: critical role of SIRT3 and autophagic flux.

Although dietary α-linolenic acid (ALA) or linolenic acid (LA) intake was reported to be epidemiologically associated with a lower prevalence of hypertension, recent clinical trials have yielded conflicting results. Comparable experimental evidence for the roles of these two different fatty acids is still lacking and the underlying mechanisms need to be further elucidated. Our data showed that ALA but not LA supplementation alleviated systolic blood pressure elevation and improved ACh-induced, endothelium-dependent vasodilation in both spontaneously hypertensive rats (SHRs) and AngII-induced hypertensive mice. In addition, SHRs displayed reduced vascular Sirtuin 3 (SIRT3) expression, subsequent superoxide dismutase 2 (SOD2) hyperacetylation and mitochondrial ROS overproduction, all of which were ameliorated by ALA but not LA supplementation. In primary cultured endothelial cells, ALA treatment directly inhibited SIRT3 reduction, SOD2 hyperacetylation, mitochondrial ROS overproduction and alleviated autophagic flux impairment induced by AngII plus TNFα treatment. However, these beneficial effects of ALA were completely blocked by silencing SIRT3. Restoration of autophagic flux by rapamycin also inhibited mitochondrial ROS overproduction in endothelial cells exposed to AngII plus TNFα. More interestingly, SIRT3 KO mice developed severe hypertension in response to a low dose of AngII infusion, while ALA supplementation lost its anti-hypertensive and endothelium-protective effects on these mice. Our findings suggest that ALA but not LA supplementation improves endothelial dysfunction and diminishes experimental hypertension by rescuing SIRT3 impairment to restore autophagic flux and mitochondrial redox balance in endothelial cells.

Sheng Mai San protects H9C2 cells against hyperglycemia-induced apoptosis.

BACKGROUND: Sheng Mai San (SMS) has been proven to exhibit cardio-protective effects. This study aimed to explore the molecular mechanisms of SMS on hyperglycaemia (HG)-induced apoptosis in H9C2 cells. METHODS: HG-induced H9C2 cells were established as the experimental model, and then treated with SMS at 25, 50, and 100 µg/mL. H9C2 cell viability and apoptosis were quantified using MTT and Annexin V-FITC assays, respectively. Furthermore, Bcl-2/Bax signalling pathway protein expression and Fas and FasL gene expression levels were quantified using western blotting and RT-PCR, respectively. RESULTS: SMS treatments at 25, 50, 100 µg/mL significantly improved H9C2 cell viability and inhibited H9C2 cell apoptosis (p < 0.05). Compared to the HG group, SMS treatment at 25, 50, and 100 µg/mL significantly downregulated p53 and Bax expression and upregulated Bcl-2 expression (p < 0.05). Moreover, SMS treatment at 100 µg/mL significantly downregulated Fas and FasL expression level (p < 0.05) when compared to the HG group. CONCLUSION: SMS protects H9C2 cells from HG-induced apoptosis probably by downregulating p53 expression and upregulating the Bcl-2/Bax ratio. It may also be associated with the inhibition of the Fas/FasL signalling pathway.

Symmetrical polarization splitter/rotator design and application in a polarization insensitive WDM receiver.

In integrated photonics, the design goal of a polarization splitter/rotator (PSR) has been separating the TE0 and TM0 modes in a waveguide. This is a natural choice. But in theory, a PSR only needs to project the incoming State Of Polarization (SOP) orthogonally to its output ports, using any orthogonal mode basis set in the fiber. In this article, we introduce a novel PSR design that alternatively takes the linear combination of TE0 and TM0 (TE0 +/- TM0) as orthogonal bases. By contrast, existing approaches exclusively use TE0 and TM0 as their basis set. The design is based on two symmetric and robust structures: a bi-layer taper and a Y-junction, and involves no bends. To prove the concept, we incorporated it into a four-channel polarization insensitive wavelength division multiplexing (PI-WDM) receiver fabricated in a standard CMOS Si photonics process. 40 Gb/s data rate and 0.7 +/- 0.2 dB polarization dependent loss (PDL) is demonstrated on each channel. Lastly, we propose an improved PSR design with 12 µm device length, < 0.1 dB PDL, < 0.4 dB insertion loss and < 0.05 dB wavelength dependence across C-band for both polarizations. Overall, our PSR design concept is simple, easy to realize and presents a new perspective for future PSR designs.

Silicon microring modulator for 40 Gb/s NRZ-OOK metro networks in O-band.

A microring-based silicon modulator operating at 40 Gb/s near 1310 nm is demonstrated for the first time to our knowledge. NRZ-OOK signals at 40 Gb/s with 6.2 dB extinction ratio are observed by applying a 4.8 Vpp driving voltage and biasing the modulator at 7 dB insertion loss point. The energy efficiency is 115 fJ/bit. The transmission performance of 40 Gb/s NRZ-OOK through 40 km of standard single mode fiber without dispersion compensation is also investigated. We show that the link suffers negligible dispersion penalty. This makes the modulator a potential candidate for metro network applications.

High speed silicon microring modulator employing dynamic intracavity energy balance.

High speed coupling-modulation of a microring-based light drop structure is proposed, which removes severe signal distortion due to intracavity energy depletion and separates the modulation speed from the resonator linewidth restriction. Extinction ratio improvement from <1 dB to >20 dB with 40 Gb/s non-return-to-zero (NRZ) signals is obtained with 25 times smaller drive voltage. The tolerance to active ring propagation loss is increased from 5 dB/cm to over 25 dB/cm with less than 5% modulation bandwidth reduction. The possibility of obtaining 160 Gb/s NRZ signal with no more than 4 V drive voltage and less than 5 dB insertion loss is highlighted.

Coupled-ring-resonator-based silicon modulator for enhanced performance.

A compact silicon coupled-ring modulator structure is proposed. Two rings are coupled to each other, and only one of these rings is actively driven and over-coupled to a waveguide, which enables high modulation speed. The resultant notch filter profile is steeper than that of the single ring and has exhibited a smaller resonance shift and lower driving electrical power. Simulation results include: (i) potentially 60-Gb/s non-return-to-zero (NRZ) data modulation and over 20-dB extinction ratio can be achieved by shifting the active ring by a 20 GHz resonance shift, (ii) the frequency chirp of the modulated signals can be adjusted by varying the coupling coefficient between the two rings, and (iii) dispersion tolerance at 0.5-dB power penalty is extended from 18 to 85 ps/nm, for a 40-Gb/s NRZ signal.

Monolithic modulator and demodulator of differential quadrature phase-shift keying signals based on silicon microrings.

Silicon microring resonators are proposed to achieve ultrasmall differential quadrature phase-shift keying modulators and demodulators operated at 20 Gb/s, which may require a dramatically reduced chip size. The modulators are characterized in terms of the carrier transit time and misalignment of the driving signals, while the demodulation performance is analyzed in terms of the bandwidth and frequency detuning of the demodulator. A bit-error rate of <10(-9) is achieved using all microring-based devices in the back-to-back case.

Data quality dependencies in microring-based DPSK transmitter and receiver.

An ultra-small silicon-based microring modulator and filter were proposed to generate and demodulate NRZ DPSK at 10 Gb/s. In this paper, we analyze performance dependencies of the modulator and demodulator under different operating conditions, such as variable laser linewidth, phase shift, demodulator offset and receiver bandwidth. Data quality of the microring-based DPSK transceiver can be optimized with eye-opening improvement of up to 7 dB. Transmission performance of the all-microring-based DPSK signal over a 70-km single mode fiber is compared to that of DPSK using a Mach-Zehnder modulator and a delay-line interferometer.

Microring-based modulation and demodulation of DPSK signal.

Ultra-small modulator and demodulator for 10 Gb/s differential phase-shift-keying (DPSK), using silicon-based microrings, are proposed. A single-waveguide microring modulator with over-coupling between ring and waveguide generates a DPSK signal, while a double-waveguide microring filter enables balanced DPSK detection. These modulator and demodulator are characterized. A trade-off between pattern dependence of the Duobinary signal and alternate-mark inversion signal power in demodulator design is discussed. Power penalty of the proposed approach is 0.8 dB relative to baseline using conventional modulation and demodulation techniques.