Orbital Angular Momentum-based Space Division Multiplexing for High-capacity Underwater Optical Communications

To increase system capacity of underwater optical communications, we employ the spatial domain to simultaneously transmit multiple orthogonal spatial beams, each carrying an independent data channel. In this paper, we multiplex and transmit four green orbital angular momentum (OAM) beams through a single aperture. Moreover, we investigate the degrading effects of scattering/turbidity, water current, and thermal gradient-induced turbulence, and we find that thermal gradients cause the most distortions and turbidity causes the most loss. We show systems results using two different data generation techniques, one at 1064 nm for 10-Gbit/s/beam and one at 520 nm for 1-Gbit/s/beam, we use both techniques since present data-modulation technologies are faster for infrared (IR) than for green. For the higher-rate link, data is modulated in the IR, and OAM imprinting is performed in the green using a specially-designed metasurface phase mask. For the lower rates, a green laser diode is directly modulated. Finally, we show that inter-channel crosstalk induced by thermal gradients can be mitigated using multi-channel equalisation processing.Comment: 26 pages, 5 figure

Mode division multiplexing using an orbital angular momentum mode sorter and MIMO-DSP over a graded-index few-mode optical fibre

Mode division multiplexing (MDM)– using a multimode optical fiber’s N spatial modes as data channels to transmit N independent data streams – has received interest as it can potentially increase optical fiber data transmission capacity N-times with respect to single mode optical fibers. Two challenges of MDM are (1) designing mode (de)multiplexers with high mode selectivity (2) designing mode (de)multiplexers without cascaded beam splitting’s 1/N insertion loss. One spatial mode basis that has received interest is that of orbital angular momentum (OAM) modes. In this paper, using a device referred to as an OAM mode sorter, we show that OAM modes can be (de)multiplexed over a multimode optical fiber with higher than −15 dB mode selectivity and without cascaded beam splitting’s 1/N insertion loss. As a proof of concept, the OAM modes of the LP11 mode group (OAM−1,0 and OAM+1,0), each carrying 20-Gbit/s polarization division multiplexed and quadrature phase shift keyed data streams, are transmitted 5km over a graded-index, few-mode optical fibre. Channel crosstalk is mitigated using 4 × 4 multiple-input-multiple-output digital-signal-processing with <1.5 dB power penalties at a bit-error-rate of 2 × 10−3

Ciências sociais e Psicologia

Formatura de Ciências Sociais e Psicologia 2018-

Scalable and Reconfigurable Optical Tap-Delay-Line for Multichannel Equalization and Correlation of 20-Gbaud QPSK signals Using Nonlinear Wave Mixing and a Microresonator Kerr Frequency Comb

We demonstrate a scalable and reconfigurable optical TDL for multichannel equalization and correlation of 20-Gbaud QPSK signals using nonlinear wave mixing and a Kerr frequency comb. The two/three-tap OTDL is demonstrated to simultaneously equalize a first signal and to search two/three-symbol patterns on another channel

Higher-order QAM data transmission using a high-coherence hybrid Si/III–V semiconductor laser

We experimentally demonstrate the use of a high-coherence hybrid silicon (Si)/III–V semiconductor laser as the light source for a transmitter generating 20 Gbaud 16- and 64- quadrature amplitude modulated (QAM) data signals over an 80 km single-mode fiber (SMF) link. The hybrid Si/III–V laser has a measured Schawlow–Townes linewidth of ∼10kHz, which is achieved by storing modal optical energy in low-loss Si, rather than the relatively lossy III–V materials. We measure a received bit error rate (BER) of 4.1×10⁻³ when transmitting the 64-QAM data over an 80 km SMF using the hybrid Si/III–V laser. Furthermore, we measure a BER of <1×10⁻⁴ with the Viterbi–Viterbi digital carrier phase recovery method when transmitting the 16-QAM data over an 80 km SMF using the hybrid Si/III–V laser. This performance is achieved at power penalties lower than those obtained with an exemplary distributed feedback laser and slightly higher than those with an exemplary narrow-linewidth external cavity laser

Development of direct conversion of syngas to unsaturated hydrocarbons based on Fischer-Tropsch route

Fischer-Tropsch synthesis (FTS) has attracted significant attention, particularly from countries lacking petroleum but rich in coal or natural gas reserves. Recently, the syngas conversion to higher value products such as olefins (FTO) and aromatics (FTA) has become a hot research field. Direct synthesis of olefins and aromatics from syngas is an ideal route, which is an effective way to improve the economic feasibility of the FTS process. This review mainly focuses on the latest breakthroughs in controlling catalytic efficiency and selectivity in FTO/FTA. Active metal/phase, transition metal promoter, alkali promoter, support, and photocatalysis are reviewed. This review will not only contribute to the rational design of new FTO/FTA catalysts but also discuss the extension of industrial application in future syngas chemistry

Experimental demonstration of three-fold wavelength multicasting of a 64-QAM 120 Gbit/s data channel using a Kerr frequency comb and nonlinear wave mixing

We experimentally demonstrate three-fold wavelength multicasting of a 64-quadrature-amplitude-modulation (QAM), 120-Gbit/s data channel using a microresonator Kerr frequency comb and nonlinear wave mixing. The multicasting is achieved with a data signal and four comb lines serving as the pump lasers in a periodically poled lithium niobate (PPLN) waveguide. Minimal extra phase noise from the pumps is introduced into the multicast copies due to the mutual coherence between the Kerr comb lines. All three multicast copies achieve a bit-error rate (BER) <= 3.5E-3, which is below the forward-error-correction threshold. Both the error vector magnitude (EVM) and BER performances show <0.5-dB optical signal-to-noise ratio (OSNR) penalty for the multicast copies compared to the original data signal