Optical Communication Experiments Research Articles

Underwater wireless optical NOMA communication experiment system exploiting GaN-based micro-LED array grouping

Underwater wireless optical NOMA communication experiment system exploiting GaN-based micro-LED array grouping

Experimental demonstration of SNSPD-based free space optical communication with a high extinction ratio modulator

With the development of space technology, the amount of information transmission required by satellites and various spacecraft has increased exponentially. The use of optical communications is a means for future high-speed communications. Adopting superconducting nanowire single photon detectors (SNSPDs) as a receive detector can be capable of detecting signals on the photon scale, which has great application prospects in the field of deep-space optical communication for faint signal detection. However, the use of SNSPDs and high-peak-power optical pulse signals also place higher demands on the extinction ratio of modulators. Therefore, in this paper, we designed a high extinction ratio optical modulator, which adopts cascaded Mach-Zehnder modulators structure, and the static extinction ratio can be reached 77.5 dB. In addition, an SNSPD-based 3.4 km free space optical communication experiment is successfully carried out by using the modulator and a diffuse reflector plate.

Simulation analysis of underwater wireless optical communication based on Monte Carlo method and experimental research in complex hydrological environment

This paper aims to address the challenges of short optical communication distances and high Bit Error Rates (BERs) caused by seawater absorption, scattering, and underwater turbulence. This paper establishes an optical communication channel model based on the Monte Carlo method and simulates and analyzes the process of received optical power attenuation when light is transmitted underwater due to absorption and scattering. The simulation model focuses on the influence of seawater type, transmission distance, receiver position, and angle on the received optical power attenuation. The results of this simulation will provide theoretical support for the development of prototype underwater optical communication systems and experiments in complex environments. To solve the long-range weak signal reception and processing issues in underwater optical wireless communication systems, this paper proposes the design and implementation of an underwater optical wireless communication system using optimized on-off keying high-power light-emitting diode/laser diode modulation technology and avalanche photodiode (APD)/photomultiplier (PMT) receiver modules. In addition, this paper describes the design of the underwater optical communication host computer software, which provides functions such as mode selection, BER monitoring, and file transfer. To test the performance of the proposed system, this paper conducts experiments in a 35 m long pool, fixed platform, and underwater mobile platform, as well as cross-air-water interface optical communication performance test experiments in a complex hydrological environment. The results show that the system achieved a 35 m underwater medium communication distance, transmission rate of 5–20 Mbps, and cross-domain wireless optical communication function under the condition of a BER of less than 10−6. The experiments also revealed that the communication distance decreases as the turbidity of the water body increases and the PMT receiver module selected at the receiver end has a longer communication distance than the APD receiver module. Overall, this paper demonstrates the feasibility of the proposed technology for underwater optical communication systems in complex waters, providing theoretical and data support for the next engineering practice.

Organic photovoltaics for simultaneous energy harvesting and high-speed MIMO optical wireless communications

We show that organic photovoltaics (OPVs) are suitable for high-speed optical wireless data receivers that can also harvest power. In addition, these OPVs are of particular interest for indoor applications, as their bandgap is larger than that of silicon, leading to better matching to the spectrum of artificial light. By selecting a suitable combination of a narrow bandgap donor polymer and a nonfullerene acceptor, stable OPVs are fabricated with a power conversion efficiency of 8.8% under 1 Sun and 14% under indoor lighting conditions. In an optical wireless communication experiment, a data rate of 363 Mb/s and a simultaneous harvested power of 10.9 mW are achieved in a 4-by-4 multiple-input multiple-output (MIMO) setup that consists of four laser diodes, each transmitting 56 mW optical power and four OPV cells on a single panel as receivers at a distance of 40 cm. This result is the highest reported data rate using OPVs as data receivers and energy harvesters. This finding may be relevant to future mobile communication applications because it enables enhanced wireless data communication performance while prolonging the battery life in a mobile device.

Optical storage of Ince-Gaussian modes in warm atomic vapor.

We report on the optical storage of Ince-Gaussian modes in a warm rubidium vapor cell based on electromagnetically induced transparency protocol, and we also qualitatively analyze how atomic diffusion affects the retrieved beams after storage. Ince-Gaussian modes possess very complex and abundant spatial structures and form a complete infinite-dimensional Hilbert space. Successfully storing such modes could open up possibilities for fundamental high-dimensional optical communication experiments.

LED-Based Underwater Wireless Optical Communication for Small Mobile Platforms: Experimental Channel Study in Highly-Turbid Lake Water

Underwater collaborative work between small mobile platforms (SMP) such as divers, litter submarine or AUV, requires a high data rate communication system which is compact, reliable, affordable and eye-safe. The high bandwidth of LED-based underwater wireless optical communication (UWOC) is an advantage. Artificial, emulated as well as simulated, turbid underwater channel has been studied recently, but no practical nature water. To fully meet the requirements of challenging turbid underwater channel scenarios for SMP, we demonstrated a green LED-based UWOC system up to a bandwidth of 3.4 MHz in a highly-turbid nature lake water. Through a contrast wireless optical communication (WOC) experiment in air, turbid water channel is observed to compensates the receiving signal amplitude attenuates after propagating a longer attenuation length due to multiple-scattered light caused diffusion, and thus to be more like a single-input multi-output (SIMO) system. From our experimental observation, the SIMO channel model could be employed not only in turbulent UWOC, but also in highly turbid UWOC. Moreover, turbid water channel is observed a “frequency selection” effect, thus LED with lower threshold voltage at higher frequency would optimize bandwidth and link range, and a robust pre-code for interference cancellation would be a well-direct choice to constructing different UWOC system in highly turbid water for SMP. Our finding will provide a new reference complementing the current LED-based UWOC systems in realistic water environment.

Experimental realization of Fermi-Pasta-Ulam-Tsingou recurrence in a long-haul optical fiber transmission system

The integrable nonlinear Schrödinger equation (NLSE) is a fundamental model of nonlinear science which also has important consequences in engineering. The powerful framework of the periodic inverse scattering transform (IST) provides a description of the nonlinear phenomena modulational instability and Fermi-Pasta-Ulam-Tsingou (FPUT) recurrence in terms of exact solutions. It associates the complex nonlinear dynamics with invariant nonlinear spectral degrees of freedom that may be used to encode information. While optical fiber is an ideal testing ground of its predictions, maintaining integrability over sufficiently long distances to observe recurrence, as well as synthesizing and measuring the field in both amplitude and phase on the picosecond timescales of typical experiments is challenging. Here we report on the experimental realization of FPUT recurrence in terms of an exact space-time-periodic solution of the integrable NLSE in a testbed for optical communication experiments. The complex-valued initial condition is constructed by means of the finite-gap integration method, modulated onto the optical carrier driven by an arbitrary waveform generator and launched into a recirculating fiber loop with periodic amplification. The measurement with an intradyne coherent receiver after a predetermined number of revolutions provides a non-invasive full-field characterization of the space-time dynamics. The recurrent space-time evolution is in close agreement with theoretical predictions over a distance of 9000 km. Nonlinear spectral analysis reveals an invariant nonlinear spectrum. The space-time scale exceeds that of previous experiments on FPUT recurrence in fiber by three orders of magnitude.

From Stochastic Optics to the Wigner Formalism: The Role of the Vacuum Field in Optical Quantum Communication Experiments

The Wigner formalism in the Heisenberg picture constitutes a bridge that connects Quantum Optics to Stochastic Optics. The vacuum field appears explicitly in the formalism, and the wavelike aspects of light are emphasised. In addition, the zeropoint intensity as a threshold for detection is a common denominator in both theories. In this paper, after summarising the basic rules of the Wigner approach and its application to parametric down-conversion, some new results are presented that delve into the physical meaning of the zeropoint field in optical quantum communication. Specifically, the relationship between Bell-state distinguishability and the number of sets of zeropoint modes that take part in the experiment is analysed in terms of the coupling between the phases of the different fields involved and the subtraction of the zeropoint intensity at the detectors. Additionally, the connection between the compatibility theorem in quantum cryptography and zeropoint field is stressed.

Optical wireless APD receivers in 035 µm HV CMOS technology with large detection area

The development of two high-speed monolithically integrated optical receivers for wireless optical communication is presented from the design phase to the measurement. The first high-speed receiver is the modified previous design with an integrated 200-µm diameter avalanche photodiode. The redesign improved the optical sensitivity by 3.7 dB resulting in the sensitivity of -35.5 dBm at 1 Gbit/s. The second receiver is an avalanche photodiode receiver with increased photodiode diameter of 400 µm with a sensitivity of -34.7 dBm at 1 Gbit/s. The receivers were employed in wireless optical communication experiments under various ambient light conditions. The maximum error free transmission distance is 22 m at 1 Gbit/s OWC link. The limits of the used standard 0.35 µm HV CMOS technology are estimated in terms of maximum possible detection area of avalanche photodiode receiver still capable for Gbit data rates.

Probabilistic Constellation Shaping for Optical Fiber Communications

We review probabilistic constellation shaping (PCS), which has been a key enabler for several recent record-setting optical fiber communications experiments. PCS provides both fine-grained rate adaptability and energy efficiency (sensitivity) gains. We discuss the reasons for the fundamentally better performance of PCS over other constellation shaping techniques that also achieve rate adaptability, such as time-division hybrid modulation, and examine in detail the impact of sub-optimum shaping and forward error correction (FEC) on PCS systems. As performance metrics for systems with PCS, we compare information-theoretic measures such as mutual information (MI), generalized MI (GMI), and normalized GMI, which enable optimization and quantification of the information rate (IR) that can be achieved by PCS and FEC. We derive the optimal parameters of PCS and FEC that maximize the IR for both ideal and non-ideal PCS and FEC. To avoid plausible pitfalls in practice, we carefully revisit key assumptions that are typically made for ideal PCS and FEC systems.

Assessing Radiation Hardness of Silicon Photonic Sensors

In recent years, silicon photonic platforms have undergone rapid maturation enabling not only optical communication but complex scientific experiments ranging from sensors applications to fundamental physics investigations. There is considerable interest in deploying photonics-based communication and science instruments in harsh environments such as outer space, where radiation damage is a significant concern. In this study, we have examined the impact of cobalt-60 γ-ray radiation up to 1 megagray (MGy) absorbed dose on silicon photonic devices. We do not find any systematic impact of radiation on passivated devices, indicating the durability of passivated silicon devices under harsh conditions.

Spatial mode multiplexing using volume holographic gratings.

We experimentally demonstrate spatial mode multiplexing of optical beams using multiplexed volume holographic gratings (MVGHs) formed in phenanthrenquinone-poly (methyl methacrylate) (PQ-PMMA) photopolymer. Multiple spatial modes of Laguerre-Gaussian (LG) beams are recorded at the same pupil area of a volume hologram resulting in MVHGs, for simultaneous reconstruction of spatial modes. In addition, a helical phase beam, a non-diffracting beam with conical phase profile, and a parabolic non-diffracting beam with cubic phase profile have also been simultaneously recorded and reconstructed from MVHGs. Utilizing Bragg wavelength degeneracy property of volume hologram these multiplexed modes are reconstructed at multiple wavelengths ranging from blue (450nm) to red (635). Due to combined effect of three-dimensional pupil, Bragg wavelength degeneracy, angular selectivity, together with spatial mode properties these, MVHGs can act as spatial mode filter with spectral filtering property. Advantages of volume holography in beam shaping are discussed. Multiple first diffraction orders with desired beam shapes obtained from the single optical element (i.e. a volume hologram with MVHGs) may find important applications in optical communication experiments, and in volume holographic imaging and microscopy. Experimental results show solid evidence that MVGHs in beam shaping provide a simple, compact, single element, and direct way to multiplex spatial modes.

Controllable pulse width of bright similaritons in a tapered graded index diffraction decreasing waveguide.

We obtain the bright similariton solutions for generalized inhomogeneous nonlinear Schrödinger equation (GINLSE) which governs the pulse propagation in a tapered graded index diffraction decreasing waveguide (DDW). The exact solutions have been worked out by employing similarity transformations which involve the mapping of the GINLSE to standard NLSE for the certain conditions of the parameters. By making use of the exact analytical solutions, we have investigated the dynamical behavior of optical similariton pairs and have suggested the methods to control them as they propagate through DDW. Moreover, pulse width of similariton is controlled through various profiles. These results are helpful to understand the similaritons in DDW and can be potentially useful for future experiments in optical communications which involve optical amplifiers and long-haul telecommunication networks.

Impact of 4D Channel Distribution on the Achievable Rates in Coherent Optical Communication Experiments

We experimentally investigate mutual information and generalized mutual information for coherent optical transmission systems. The impact of the assumed channel distribution on the achievable rate is investigated for distributions in up to four dimensions. Single channel and wavelength division multiplexing (WDM) transmission over transmission links with and without inline dispersion compensation are studied. We show that for conventional WDM systems without inline dispersion compensation, a circularly symmetric complex Gaussian distribution is a good approximation of the channel. For other channels, such as with inline dispersion compensation, this is no longer true and gains in the achievable information rate are obtained by considering more sophisticated four-dimensional (4D) distributions. We also show that for nonlinear channels, gains in the achievable information rate can also be achieved by estimating the mean values of the received constellation in four dimensions. The highest gain for such channels is seen for a 4D correlated Gaussian distribution.

Development of Online Optical Fiber Communications Experiments using the Interactive ILabs Shared Architecture

intervention approach in introducing new online fiber optic communications labs in an operating environment where resources for establishing new conventional labs are limited is presented. The focus of this educational intervention is on the technological aspect required to develop and deploy the labs online. The developed labs demonstrated some of the distinctive features of fiber optic communications compared to the conventional electronics copper wire communications media. Telecommunications kits from Emona - FOTEx, National Instruments - ELVIS II hardware platform and MIT iLabs Shared Architecture remote lab framework were used to develop and deploy online fiber optic experiments. The developed labs have provided means for students to perform relatively new lab work anytime, anywhere. The sharing aspects extend their accessibility to other institutions with similar operating environment and limited technical know- how on managing remote labs.

Controllable behaviors of spatiotemporal breathers in a generalized variable-coefficient nonlinear Schrödinger model from arterial mechanics and optical fibers

We study the (3+1)-dimensional nonlinear Schrodinger equation with different distributed transverse diffraction and dispersion based on the similarity transformation and obtain exact spatiotemporal breather solutions. Based on these solutions, two kinds of combined Akhmediev breather and Kuznetsov–Ma soliton display their controllable properties by modulating the values of the maximum effective distance \(Z_\mathrm{m}\) and the effective distance at peak of breather \(Z_0\). Our results indicate that the relation between \(Z_\mathrm{m}\) and \(Z_0\) is the basis to realize the control and manipulation of propagation behaviors of breathers, such as complete excitation, sustainment, restraint and recurrence. These results are potentially useful for future experiments in various blood vessels, optical communications, and long-haul telecommunication networks.

Measuring Operating Conditions of LED as a Light Receiving Element in an Optical Communication Experiment Set(My Idea)

Measuring Operating Conditions of LED as a Light Receiving Element in an Optical Communication Experiment Set(My Idea)

Analytical soliton solutions for the cubic–quintic nonlinear Schrödinger equation with Raman effect in the nonuniform management systems

Based on the Kundu–Eckhaus equation with variable coefficients, the exact one-soliton and two-soliton solutions have been explicitly given by an appropriate similarity transformation method. As an example, an exponential distributed fiber control system, nonlinearity management system and dispersion management system have been considered, and the propagation characteristics of the exact soliton solutions in the three nonuniform management systems have been investigated in detail. Especially, the dynamic properties of the amplitude, pulse width and the central position of the soliton with transmission distance have been studied. The results have some guiding significance for soliton amplification, compression and control management, and can provide some theoretical analysis for carrying out optical soliton communication experiment.

Transmission of the LED light from the space to the ground

We report the first observation and the analysis of the LED light emission from the space to the ground. A small cube satellite mounted LEDs (Light Emitting Diodes) is released from the ISS (International Space Station). The power density of the LED emission of 4W on the ground is about 4 × 10−12 W/m2 in average, which is equivalent to the star of the 8.5th grade in average. The frequencies of the macro pulses (10Hz) and the micro pulses (5kHz) of the LED signal, were correctly clarified using the Fourier analysis. As the optical communication experiment, the potentiality of the data transmission rate of more than 1 kbit/second was shown.

S192031 福岡工業大学超小型人工衛星FITSAT-1(にわか)の成果報告([S192-03]宇宙システムに関する実践的解決と知見の汎用化(3))

We report the research activities of the cube satellite FITSAT-1 (NIWAKA). In this project, the first observation and the analysis of the LED light emission from the space to the ground were performed. A small cube satellite mounted LEDs (Light Emitting Diodes) is released from the ISS (International Space Station). The power density of the LED emission of 4W on the ground is about 4xl0-12 W/m2 in average, which is equivalent to the star of the 8. 5th grade in average. The frequencies of the macro pulses (10Hz) and the micro pulses (5kHz) of the LED signal, were correctly clarified using the Fourier analysis. As the optical communication experiment, the potentiality of the data transmission rate of more than 1 kbit/second was shown.