Net-432-Gb/s/λ PS-PAM transmission based on advanced DSP and single DAC for 400†G/λ IM/DD links.

The escalating surge in datacenter traffic creates a pressing demand for augmenting the capacity of cost-effective intensity modulation and direct detection (IM/DD) systems. In this Letter, we report the demonstration of the single-lane 128-GBaud probabilistically shaped (PS)-PAM-20 IM/DD transmission using only a single digital-to-analog converter (DAC) for a net 400 G/λ system. Based on the advanced digital signal processing (DSP), we achieve net bitrates of up to 437 Gb/s for optical back-to-back and 432 Gb/s after the 0.5-km SSMF transmission in the C-band with 128-Gbaud PS-PAM-20 signals. This work is the latest demonstration on ultra-high-order PS-PAM signals achieving net bitrates exceeding 400 Gb/s despite symbol rate limitations. Notably, to the best of our knowledge, the realized net information rate ([net bitrate]/[symbol rate]) of 3.37 marks a new achievement within the domain of 400 G/λ IM/DD systems, with promising implications for enhancing bandwidth efficiency in the upcoming 1.6-Tb Ethernet scenario.

Fixation of CO2 into Cyclic Carbonates by Halogen-Bonding Catalysis.

Halogen bonding, parallel to hydrogen bonding, was introduced into the catalytic cycloaddition of carbon dioxide into epoxide (CCE) reactions. A series of halogen-bond donor (XBD) catalysts of N-iodopyridinium halide featured with N-I bond were synthesized and evaluated in CCE reactions. The optimal XBD catalyst, 4-(dimethylamino)-N-iodopyridinium bromide ([DMAPI]Br), under screened conditions at 100 °C, ambient pressure, and 1 mol % catalyst loading, realized 93 % conversion of styrene oxide into cyclic carbonate in 6 h. The substrate scope was successfully extended with excellent yields (mostly ≥93 %) and quantitative selectivity (more than 99 %). 1 H NMR spectroscopy of the catalyst [DMAPI]Br on substrate epoxide certified that the N-I bond directly coordinated with the epoxide oxygen. A plausible mechanism of halogen-bonding catalysis was proposed, in which the DMAPI cation functioned as halogen-bond donor to activate the epoxide, and the counter anion bromide attacked the methylene carbon to initiate the ring-opening of the epoxide. CCE reactions promoted by N-iodopyridinium halide, exemplify a first case of halogen-bonding catalysis in epoxide activation and CO2 transformation.