In this paper, a wideband photomultiplier tube (PMT)-based underwater wireless optical communication (UWOC) system is proposed and comprehensive experimental study of the PMT-based UWOC conducted, in which transmission distance, data rate, attenuation length (AL) pushed to 100.6 meters, 3 Gbps, 6.62, respectively. The receiver sensitivity at 100.6-meter as low -40 dBm for 1.5-Gbps on-off keying (OOK) modulation signal. To best our knowledge, first Gbps-class demonstration >100-meter that has...

Reconfigurable photonic integrated devices and circuits are very important for many applications. Among various mechanisms realizing reconfigurability, thermo-optic effect is popular because of the availability materials, design simplicity fabrication ease. In particular, silicon has a large coefficient as well high heat conductivity, thus it promising to realize efficient thermally-reconfigurable circuits. Recent progress reviewed in this paper. First, thermally-tunable filters based on...

In this paper, we experimentally demonstrate a 450-nm laser underwater wireless optical transmission system by using adaptive bit-power loading discrete multi-tone (DMT) and Volterra series based post nonlinear equalization. Post equalization mitigates the impairment of UWOC system. By incorporating with 3rd-order diagonal plane kernel, received signal-to-noise ratio (SNR) can be improved ~2 dB compared linear method. The measured capacity is 16.6 Gbps over 5 m, 13.2 35 6.6 55 m tap water...

Probabilistic constellation shaping (PCS) is utilized to approach the channel capacity limit in discrete multitone (DMT) transmission for underwater optical wireless communication (UOWC) system. A fixed quadrature amplitude modulation (QAM) format with various probabilistic distributions individually allocated different subcarriers obtain achievable maximum accordance pre-estimated signal-to-noise ratio. By using a 450-nm directly modulated laser diode (LD) an available bandwidth of ∼2.75...

In this paper, we experimentally demonstrate an underwater wireless optical communication (UWOC) system using a 450-nm gallium nitride (GaN) laser and adaptive bit-power loading discrete multitone (DMT). To enhance the capacity, post nonlinear equalizer based on simplified Volterra series is employed at receiver to mitigate impairments of UWOC system. By combining with equalization, 7.33-Gb/s DMT-modulated under 15-m tap water achieved bit error rate below 7% hard-decision forward correction...

In this paper, a low-complexity two-level chaotic encryption scheme is introduced and experimentally demonstrated to improve the physical layer security of 450-nm laser underwater optical wireless communication (UOWC) system using discrete Fourier transform spread multi-tone (DFT-S DMT) modulation. first stage, original bit stream encrypted with sequence based on one-dimensional Logistic map. second real imaginary components DFT-S symbols are further pair separate sequences, which generated...

The multimode power splitter is a fundamental component in mode-division multiplexed systems. In this paper, we design and characterize broadband compact dual-mode interferometer (MMI) optical based on subwavelength grating (SWG) structures. optimized MMI three times more than its conventional mode insensitive MMIs shows low loss crosstalk flat response over 100 nm bandwidth. Characterizations of the fabricated show that total excess experiment less 0.1 dB 0.65 for TE0 TE1, respectively,...

Underwater wireless optical communication (UWOC) is considered as an enabling technology with a mass of potential applications. The silicon photomultiplier (SiPM) exhibits bright prospect for UWOC thanks to the traits low-light detection capability, low-voltage operation, and superior operability. However, performance SiPM-based system severely degraded by dead-time caused nonlinear response. In this paper, mitigate induced distortion explore achievable capacity newly developed SiPM, we...

A novel frequency domain nonlinear compensation method, FD-NC, is proposed for orthogonal division multiplexing (OFDM) based visible light communication (VLC) system. By tackling the memory impairments from emitting diodes (LEDs) in rather than time domain, method has much lower computational complexity conventional Volterra (TD-NC). Both theoretical derivation and experimental investigation of OFDM VLC systems with four types commercial LEDs are presented. The results experiments show that...

A mode insensitive switch is proposed and experimentally demonstrated on a silicon-on-insulator platform using balanced Mach–Zehnder interferometer structure with phase shifter for on-chip division multiplexing interconnects. Switching the first three quasi-transverse electric (TE) modes, consuming less than 40 mW power demonstrated. The whole system exhibits approximately <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mo>−<!-- − --></mml:mo> <mml:mrow...

In this paper, we introduce an energy constraint to improve topology-based inverse design. Current methods typically place the constraints solely on device geometry and require many optimization iterations converge a manufacturable solution. our approach directs process solutions that best contain optical field inside waveguide core medium, leading more robust designs with relatively larger minimum feature size. To validate method, optimize two components: mode converter (MC) wavelength...

In this paper, we present the experimental results for integrated photonic devices optimized with an energy-constrained inverse design method. When constraint is applied, optimizations are directed to solutions that contain optical field inside waveguide core medium, leading more robust designs relatively larger minimum feature size. We optimize three components: a mode converter (MC), 1310 nm/1550 nm wavelength duplexer, and three-channel C-band demultiplexer coarse division multiplexing...

The nonlinearity of the light-emitting diode (LED) in underwater wireless optical communication (UWOC) systems is considered one major limiting factor that degrades system's performance. Volterra series-based nonlinear equalization widely employed to mitigate such systems. However, conventional model high complexity, especially for higher-order terms or longer memory lengths. In this paper, by pruning away some negligible beating and adaptively picking out dominant while discarding trivial...

In this paper, recent advances in underwater wireless optical communication (UWOC) are reviewed for both LED- and LD-based systems, mainly from a perspective of advanced modulation formats. Volterra series-based nonlinear equalizers, which can effectively counteract the impairments induced by UWOC system components, discussed experimentally demonstrated. Both effectiveness robustness proposed equalizer systems under different water turbidities validated. To further approach Shannon capacity...

Underwater wireless optical communication (UWOC) has broad prospects in underwater real-time applications. We design and experimentally demonstrate a discrete Fourier transform spread multi-tone (DFT-S DMT) signal transmission based on field programmable gate array for blue-LED-based UWOC system with data rate of up to 30 Mbps over 15-m channel. The architecture usage an on-chip resource as well power consumption are analyzed discussed. To reduce the impacts multipath fading received...

In this article, a novel spectrally efficient non-orthogonal discrete multi-tone (NODMT) system is proposed for the bandwidth-starved underwater wireless optical communication (UWOC) to compensate insufficient bandwidth of components. Different from other systems with complex-valued correlation matrices, designed NODMT has real-valued matrix, which significant in reducing complexity decoders, e.g., iterative detection (ID) algorithm can be reduced by 50% as compared conventional ID. However,...

We propose and experimentally demonstrate a reconfigurable mode division multiplexing (MDM) silicon photonics three-mode switch (3MS) in C-band using 120° optical hybrid based unbalanced Mach-Zehnder interferometer (UMZI) Ti/W metal heater phase-shifter. The novel 3MS enables switching of the first three transverse electric (TE) modes by exploiting relative phase difference hybrid. A proof-of-concept realization this demonstrates <12.0 μs time >12.3 dB extinction ratio at 1560 nm wavelength...

Computational inverse design techniques have shown potential to become reliable means for designing compact nanophotonic devices without compromising the performance. Much effort has been made reduce computation cost involved in optimization process and obtain final designs that are robust fabrication imperfections. In this work, we experimentally demonstrate TE0-TE1 TE1-TE3 mode converters (MCs) on silicon-on-insulator platform designed using computationally efficient shape method. These...

In this work, we experimentally demonstrate a four-mode polarization/mode insensitive 3-dB coupler based on an adiabatic coupler. The proposed design works for the first two transverse electric (TE) modes and magnetic (TM) modes. Over optical bandwidth of 70 nm (1500 to 1570 nm), exhibits at most 0.7 dB insertion loss with maximum crosstalk -15.7 power imbalance not worse than 0.9 dB. A multimode photonic switch matrix using is simultaneously exploiting wavelength division multiplexing...

Improving the spectrum efficiency (SE) is an effective method to further enhance data rate of bandwidth-limited underwater wireless optical communication (UWOC) systems. Non-orthogonal frequency-division multiplexing (NOFDM) with a compression factor 0.5 can save half bandwidth without introducing any inter-carrier-interference (ICI) only if total number subcarriers large enough, and we termed it as half-spectrum OFDM (HS-OFDM). To best our knowledge, this first reported work on closed-form...

In this letter, a multiband discrete-Fourier-transform spread (DFT-spread) is introduced to reduce the peak-to-average-power ratio (PAPR) of discrete multi-tone (DMT)-based underwater optical wireless communication (UOWC) system. The performance different DFT-spread DMT schemes in wide transmission range (from 5 55 m at fixed data rate 5.6 Gb/s) experimentally investigated. measured results show that 1-band and 2-band can significantly improve system compared with conventional clipping DMT,...

The nonlinearity of light emitting diode (LED) in visible communication (VLC) systems is considered as one major limiting factor that deteriorates the systems' performance. In this paper, nonlinear equalization VLC deemed to be a sparse recovery problem. Three different greedy algorithms, namely matching pursuit (MP), orthogonal MP (OMP), and regularized OMP (ROMP) are employed constructing sparsity-aware equalizer for LED-based systems. By adopting these number kernels can significantly...

In this paper, we design and experimentally demonstrate a two-mode three-mode mode exchanger (ME) using an inverse method. The designed MEs provide more flexibility for division multiplexing (MDM) system links. optimized designs are compact, 16 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> 24 the ME, respectively. During optimization process, fabrication imperfection tolerance, insertion loss (IL), crosstalk performance optimized....