Near-noiseless and small-footprint phase sensitive optical parametric amplifier using AlGaAs-on-insulator waveguides.

Phase sensitive amplifiers (PSAs) based on optical parametric amplification feature near noiseless amplification, which is of considerable benefit for improving the performance of optical communication systems. Currently, the majority of research on PSAs is carried out on the basis of highly nonlinear fibers or periodically poled lithium niobite waveguides, with the impediments of being susceptible to environmental interference and requiring complex temperature control systems to maintain quasi-phase matching conditions, respectively. Here, a near-noiseless and small-footprint PSA based on dispersion-engineered AlGaAs-on-insulator (AlGaAsOI) waveguides is proposed and demonstrated theoretically. The phase-dependent gain and the phase-to-phase transfer function of the PSA are calculated to analyze its characteristics. Furthermore, we investigate in detail the effects of linear loss, nonlinear coefficient, and pump power on the PSA gain and noise figure (NF) in AlGaAsOI waveguides. The results show that a PSA based on an AlGaAsOI waveguide is feasible with a maximum phase sensitive gain of 33 dB, achieving an NF of less than 1 dB over a gain bandwidth of 245 nm with a gain of >15d B, which completely covers the S + C + L band. This investigation is worthwhile for noiseless PSAs on photonic integrated chips, which are promising for low-noise optical amplification, multifunctional photonic integrated chips, quantum communication, and spectroscopy, and as a reference for low-noise PSAs depending on the third-order nonlinearity, χ (3), of the waveguide material.

Free-space transmission of picosecond-level, high-speed optical pulse streams in the 3†µm band.

The utilization of mid-infrared (mid-IR) light spanning the 3-5 µm range presents notable merits over the 1.5 µm band when operating in adverse atmospheric conditions. Consequently, it emerges as a promising prospect for serving as optical carriers in free-space communication (FSO) through atmospheric channels. However, due to the insufficient performance level of devices in the mid-IR band, the capability of mid-IR communication is hindered in terms of transmission capacity and signal format. In this study, we conduct experimental investigations on the transmission of time-domain multiplexed ultra-short optical pulse streams, with a pulse width of 1.8 ps and a data rate of up to 40 Gbps at 3.6 µm, based on the difference frequency generation (DFG) effect. The mid-IR transmitter realizes an effective wavelength conversion of optical time division multiplexing (OTDM) signals from 1.5 µm to 3.6 µm, and the obtained power of the 40 Gbps mid-IR OTDM signal at the optimum temperature of 54.8 °C is 7.4 dBm. The mid-IR receiver successfully achieves the regeneration of the 40 Gbps 1.5 µm OTDM signal, and the corresponding regenerated power at the optimum temperature of 51.5 °C is -30.56 dBm. Detailed results pertaining to the demodulation of regeneration 1.5 µm OTDM signal have been acquired, encompassing parameters such as pulse waveform diagram, bit error rate (BER), and Q factor. The estimated power penalty of the 40 Gbps mid-IR OTDM transmission is 2.4 dB at a BER of 1E-6, compared with the back-to-back (BTB) transmission. Moreover, it is feasible by using chirped PPLN crystals with wider bandwidth to increase the data rate to the order of one hundred gigabits.

On-orbit demonstration of inter-satellite free-space optical stable communication enabled by integrated optical amplification of HPA and LNA.

Satellite free-space optical (FSO) communication is very promising in improving the bandwidth and capacity of space information networks in the future. However, the inter-satellite transmission distance of over 1000 km leads to unstable optical beam pointing, acquisition, and tracking and then generates optical power jitter by a large margin before detection-demodulation. Therefore, it is difficult to realize high-stability and long-time FSO communication between satellites due to the generated bit error rate (BER) by jitter. In this paper, we report an autonomously self-designed and high-integration laser communication payload (LCP) and on-orbit-demonstrated inter-satellite 145 min, zero-BER FSO stable communication with a line rate of 2.8 Gbps. Moreover, based on the inter-satellite laser communication link, a video phone was clearly implemented for more than 10 min, and authentic user data transmitted 459,149 packets, achieving results of zero-packet loss. Summarily, this on-orbit experiment demonstrated an excellent performance of the LCP owing to the distinctive design of integrating a high-power amplifier and low-noise amplifier optical amplification function. Our space mission was successfully completed, and the on-orbit demonstration results may offer a significant reference for the field of satellite laser communication and space information networks.

150 Gbps multi-wavelength FSO transmission with 25-GHz ITU-T grid in the mid-infrared region.

The 3∼5 µm mid-infrared (mid-IR) light has several exceptional benefits in the case of adverse atmospheric conditions compared to the 1.5 µm band, so it is a promising candidate for optical carriers for free-space communication (FSO) through atmospheric channels. However, the transmission capacity in the mid-IR band is constrained in the lower range due to the immaturity of its devices. In this work, to replicate the 1.5 µm band dense wavelength division multiplexing (DWDM) technology to the 3 µm band for high-capacity transmission, we demonstrate a 12-channel 150 Gbps FSO transmission in the 3 µm band based on our developed mid-IR transmitter and receiver modules. These modules enable wavelength conversion between the 1.5 µm and 3 µm bands based on the effect of difference-frequency generation (DFG). The mid-IR transmitter effectively generates up to 12 optical channels ranging from 3.5768 µm to 3.5885 µm with a power of 6.6 dBm, and each channel carries 12.5 Gbps binary phase shift keying (BPSK) modulated data. The mid-IR receiver regenerates the 1.5 µm band DWDM signal with a power of -32.1 dBm. Relevant results of regenerated signal demodulation have been collected in detail, including bit error ratio (BER), constellation diagram, and eye diagram. The power penalties of the 6th to 8th channels selected from the regenerated signal are lower than 2.2 dB compared with back-to-back (BTB) DWDM signal at a bit error ratio (BER) of 1E-6, and other channels can also achieve good transmission quality. It is expected to further push the data capacity to the terabit-per-second level by adding more 1.5 µm band laser sources and using wider-bandwidth chirped nonlinear crystals.

Classical Analog and Hybrid Metamaterials of Tunable Multiple-Band Electromagnetic Induced Transparency.

The electromagnetic induced transparency (EIT) effect originates from the destructive interference in an atomic system, which contributes to the transparency window in its response spectrum. The implementation of EIT requires highly demanding laboratory conditions, which greatly limits its acceptance and application. In this paper, an improved harmonic spring oscillation (HSO) model with four oscillators is proposed as a classical analog for the tunable triple-band EIT effect. A more general HSO model including more oscillators is also given, and the analyses of the power absorption in the HSO model conclude a formula, which is more innovative and useful for the study of the multiple-band EIT effect. To further inspect the analogizing ability of the HSO model, a hybrid unit cell containing an electric dipole and toroidal dipoles in the metamaterials is proposed. The highly comparable transmission spectra based on the HSO model and metamaterials indicate the validity of the classical analog in illustrating the formation process of the multiple-band EIT effect in metamaterials. Hence, the HSO model, as a classical analog, is a valid and powerful theoretical tool that can mimic the multiple-band EIT effect in metamaterials.

Shudi Erzi San relieves ovary aging in laying hens.

Poultry meat and eggs are a primary source of animal protein. To meet the market needs, high yield laying hens are reared continuously, resulting in quick ovary aging. Thus, we investigated the anti-aging effects of Shudi Erzi San (SES) on laying hens. Sixty 300-day-old laying hens were divided into 2 experimental groups and a control group. The control group was fed on a basic diet, which was supplemented with 1% and 2% SES for experimental groups I and II, respectively. Egg quality and changes in serum hormones and blood-biochemical indicators of laying hens were determined. The rate of egg production was significantly higher in group Ⅱ than in both the control and group Ⅰ by 9.29 and 8.22 percentage points, respectively (P < 0.05). Eggshell strength of groups Ⅰ and Ⅱ were significantly higher than that of the control group (P < 0.01). Albumen height and Haugh Units of group Ⅱ were significantly higher than those of the control (P < 0.05). Serum levels of follicle stimulating hormone and estradiol in group Ⅱ were significantly higher than those of both the control and group Ⅰ (P < 0.05), whereas groups Ⅰ and Ⅱ had significantly higher serum levels of luteinizing hormone than the control (P < 0.05). Levels of superoxide dismutase (SOD) did not significantly differ between the control and group Ⅰ (P > 0.05), but SOD and malondialdehyde (MDA) levels in group Ⅱ were significantly higher and lower, respectively (P < 0.05) when compared to the control. Compared with the control, uric acid levels in groups Ⅰ and Ⅱ were significantly lower (P < 0.05), as was urea nitrogen in group Ⅱ (P < 0.05). Transcriptome and KEGG pathway analysis of ovarian tissues of laying hens showed a significant immune related signal pathway as the possible main regulator of a lysosome related signal pathway. Thus, supplementing chicken feed with SES improves egg production and quality and alleviates ovarian decline in laying hens.

Untargeted and targeted metabolomics profiling reveals the underlying pathogenesis and abnormal arachidonic acid metabolism in laying hens with fatty liver hemorrhagic syndrome.

As a metabolic disease, fatty liver hemorrhagic syndrome (FLHS) has become the major factor responsible for the noninfectious cause of mortality in laying hens, which lead to huge economic losses to poultry industry. However, the pathogenesis of FLHS remains unclear. The aim of present study was to identify novel liver metabolites associated with FLHS. Twenty healthy Chinese commercial Jing Fen laying hens aged 90 d were used in present study. After acclimatization for 2 wk, the hens were divided into 2 treatments (n = 10): control group (normal diet) and FLHS group (high-energy low-protein diet). The experiment lasted for 48 d, and the laying hens were killed for blood and liver sampling at the end of the experiment. Blood biochemical indicators and liver pathological changes were examined. Meanwhile, the changes in liver metabolic profile were investigated with the application of metabolomics approach. Significant increased levels of alanine aminotransferase, aspartate aminotransferase, low density lipoprotein, total cholesterol and triglycerides, decreased high density lipoprotein (P < 0.01), and hepatic steatosis were observed in hens of FLHS group, which suggested FLHS was successfully established in this study. Distinct changes in metabolite patterns in liver between control and FLHS group were observed by partial least-squares discriminant analysis. In total, 42 liver metabolites including tyrosine, glutathione, carnitine, linoleic acid, uric acid, arachidonic acid (ARA), lactate and lysophosphatidylcholine (14: 0) were identified and considered to be related with pathogenesis of FLHS. Pathway analysis revealed that these metabolites were mainly involved in amino acid metabolism, fatty acid metabolism, ARA metabolism, glucose metabolism and glycerophospholipid metabolism. Furthermore, targeted metabolomics found that ARA metabolites such as prostaglandins and hydroxyeicosatetraenoic acids were significantly increased in FLHS group (P < 0.05). In conclusion, our data showed that liver metabolites and ARA metabolism were linked to the pathophysiology of FLHS, which provided a basis for understanding the pathogenesis of FLHS in laying hens.

Study on the backscattering disturbance in duplex underwater wireless optical communication systems.

Backscattering affects the performance of receivers in duplex underwater wireless optical communication (UWOC) systems. In this work, we study this issue using the Monte Carlo method. We show that with an increase of transmitter divergence angle, backscattering light power changes little while communication signal and optical signal-to-noise ratio (OSNR) are reduced dramatically at the receiver. With an increase of receiver field angle, backscattering light power becomes higher, communication signal is nearly unchanged, and OSNR is reduced greatly. With an increase of the separated distance between receiver and transmitter in each terminal, backscattering light power decreases quickly, communication signal is unchanged, and OSNR increases rapidly. With an increase of communication distance, backscattering light power is almost unchanged while both the communication signal and OSNR are reduced drastically. We demonstrate that, to reduce the impact of backscattering disturbance, the transmitter and receiver in each terminal should be placed at a greater distance and the latter should be with a smaller field angle. When the transmitting optical power or receiving sensitivity is too high, such disturbance is hard to suppress effectively. In this case, the system should work in half-duplex mode. These results will be useful for duplex UWOC system design.