Showing papers in "IEEE Photonics Technology Letters in 2018"
TL;DR: It is demonstrated that NomA with NGDPA achieves a sum rate improvement of up to 29.1% compared with NOMA with the gain ratio power allocation method in the $2\times 2$ MIMO-VLC system with three users.
Abstract: In this letter, we apply the non-orthogonal multiple access (NOMA) technique to improve the achievable sum rate of multiple-input multiple-output (MIMO)-based multi-user visible light communication (VLC) systems. To ensure efficient and low-complexity power allocation in indoor MIMO-NOMA-based VLC systems, a normalized gain difference power allocation (NGDPA) method is first proposed by exploiting users’ channel conditions. We investigate the performance of an indoor $2\times 2$ MIMO-NOMA-based multi-user VLC system through numerical simulations. The obtained results show that the achievable sum rate of the $2\times 2$ MIMO-VLC system can be significantly improved by employing NOMA with the proposed NGDPA method. It is demonstrated that NOMA with NGDPA achieves a sum rate improvement of up to 29.1% compared with NOMA with the gain ratio power allocation method in the $2\times 2$ MIMO-VLC system with three users.
215 citations
TL;DR: A real-time indoor visible light positioning system based on the optical camera communication, where the coordinate data in the ON–OFF keying format is transmitted via light-emitting diode-based lights and captured using a smartphone camera is presented.
Abstract: We present a real-time indoor visible light positioning system based on the optical camera communication, where the coordinate data in the ON–OFF keying format is transmitted via light-emitting diode-based lights and captured using a smartphone camera. The position of the camera is estimated using a novel perspective- $n$ -point problem algorithm, which determines the position of a calibrated camera from $n~3\text{D}$ -to-2D point correspondences. The experimental results show that the proposed system offers mean position errors of 4.81 and 6.58 cm for the heights of 50 and 80 cm, respectively.
116 citations
TL;DR: In this article, a hybrid Bragg reflector (HBR) was used to enhance the color conversion efficiency and the light output intensity of monolithic RGB micro LEDs, thus reflecting the RGB light emitted to the substrate.
Abstract: In this letter, monolithic red, green, and blue (RGB) micro light-emitting diodes (LEDs) were fabricated using gallium nitride based blue micro LEDs and quantum dots (QDs). Red and green QDs were sprayed onto individual region surrounded by patterned black matrix photoresist on the blue micro LEDs to form color conversion layers. Owing to its light-blocking capability, the patterned black matrix photoresist improved the contrast ratio of the micro LEDs from 11 to 22. To enhance the color conversion efficiency and the light output intensity, a hybrid Bragg reflector (HBR) was deposited on the bottom side of the monolithic RGB micro LEDs, thus reflecting the RGB light emitted to the substrate. To further improve the color purity of the red and green light, a distributed Bragg reflector (DBR) with high reflection for the blue light was deposited on the top side of the QDs/micro LEDs. The red and green light output intensities of the micro LEDs with HBR and DBR were enhanced by about 27%.
81 citations
TL;DR: In this article, an ultrathin niobium nanofilm was employed on a photonic crystal fiber for the first time resulting sensing over a wide range of refractive indices.
Abstract: This letter presents a numerical investigation of a highly sensitive refractive index sensor based on surface plasmon resonance. An ultrathin niobium nanofilm is proposed as a new plasmonic material, which outperforms existing plasmonic materials. This nanofilm is employed on a photonic crystal fiber for the first time resulting sensing over a wide range of refractive indices. Finite-element method-based numerical analysis shows that maximum amplitude sensitivity of 1560 RIU $^{-1}$ and wavelength sensitivity of 8000 nm/RIU can be obtained for an analyte index of 1.40. A thin aluminum oxide (Al2O3) film is deposited on the outer layer of niobium film to enhance the coupling strength and in order to tune the resonance wavelength. Moreover, the effects of varying thickness of niobium nanofilm and Al2O3 film on sensing performance are also discussed. The proposed niobium nanofilm based sensor can be potentially implemented in biochemical and organic chemical sensing.
81 citations
TL;DR: The results prove the feasibility of the integration of the developed continuous variables (CV) quantum key distribution (QKD) system with legacy telecom equipment in existing WDM optical networks.
Abstract: In this letter, we report on the advances toward the integration of our developed continuous variables (CV) quantum key distribution (QKD) system in existing optical infrastructure and wavelength division multiplexed (WDM) networks. First, we investigate the tolerance of the CV-QKD system to spontaneous Raman scattering (SRS) noise, the latter being the most dominant impairment in a WDM co-existence environment for QKD. In particular, we investigate by experiment the impact of a WDM 10 × 10 Gb/s ON-OFF-keying signal in terms of induced SRS noise in the QKD channel. The spontaneous SRS noise influence is assessed for different transmission scenarios, i.e., for various optical launch powers of the WDM signal, and for different transmission links of 20, 40, 60, and 80 km. Based on the experimental data and on the measured system's parameters, we estimate the key rates and reach capabilities of the proposed CV-QKD system. The scheme supports a key rate of 90 kbit/s over 20 km, for an ideal QKD system multiplexed with 2-mW optical power. A step further, we demonstrate for first time the use of the aforementioned CV-QKD system to encrypt a 10GE client service over deployable optical transport network legacy equipment over 20 km. Our results prove the feasibility of the integration of our proposed scheme with legacy telecom equipment in existing WDM optical networks.
80 citations
TL;DR: In this article, an aluminum-doped zinc oxide (AZO) coated photonic crystal fiber (PCF) is proposed and numerically analyzed for surface plasmon resonance-based refractive index (RI) sensing.
Abstract: An aluminum-doped zinc oxide (AZO) coated photonic crystal fiber (PCF) is proposed and numerically analyzed for surface plasmon resonance-based refractive index (RI) sensing. A microchannel is incorporated in this PCF, which is proposed to be fabricated using a pulsed laser. Such a structure is expected to have less roughness compared to that fabricated by mechanical polishing. Furthermore, properties such as no island formation and absence of intraband transition are added advantages of AZO. Numerical simulation shows that the maximum wavelength sensitivity and the corresponding resolution of this sensor are 5000 nm/RIU and 2 × 10
-5
RIU, respectively. Furthermore, the amplitude sensitivity is found to be as high as 167 RIU
-1
. The proposed structure can be easily fabricated and utilized for sensing applications as it does not require either coating of metals on the inner surface of holes of PCF nor filling of the voids of PCF and it requires a small amount of analyte for RI monitoring.
71 citations
TL;DR: In this article, a simultaneous measurement system of temperature and relative humidity is proposed, which consists of a fiber Bragg grating (FBG) and Fabry-Perot (FP) interferometer.
Abstract: In this letter, a simultaneous measurement system of temperature and relative humidity is proposed, which consists of a fiber Bragg grating (FBG) and Fabry–Perot (FP) interferometer. The FP interferometer was fabricated by splicing the hollow capillary with a single-mode fiber and the end of the hollow capillary was filled with a layer of polyimide, achieving a humidity sensitivity of 22.07 pm/%RH in the range of 20–90 %RH. FBG is insensitive to humidity, which can be used to measure temperature and eliminate the obstruction of temperature on FP humidity probe by formula conversion. The temperature sensitivity of FBG is 9.98 pm/°C. Due to low cost and good stability, this system has broad application prospects in the fields of food processing, medical care, and food storage.
67 citations
TL;DR: In this paper, a novel polarization beam splitter (PBS) based on a subwavelength grating (SWG) multimode interference coupler for the silicon-on-insulator platform is presented.
Abstract: We demonstrate a novel polarization beam splitter (PBS) based on a subwavelength grating (SWG) multimode interference (MMI) coupler for the silicon-on-insulator platform The birefringence of the MMI coupler is engineered using SWG, which leads to a compact design footprint, with a device length of less than $100~\mu \text{m}$ Our PBS has simulated extinction ratios (ERs) better than 20 dB for both polarizations over the wavelength range from 1530 to 1625 nm that covers the entire $C$ - and $L$ -bands The fabricated device achieves the measured ERs larger than 20 dB at the wavelength of 1550 nm for both polarizations, and the insertion losses of 19 and 25 dB for the transverse electric (TE) and transverse magnetic (TM) polarizations, respectively, at 1550 nm In addition, the measured ERs are larger than 145 dB for the TE polarization and 117 dB for the TM polarization over an 84-nm spectral range covering the entire $C$ -band
67 citations
TL;DR: In this article, a thermally/electrically tunable graphene on white graphene polarizer is proposed, in which the resonant coupling between the plasmonic surface modes of the structure and the transverse electric (TE) [or transverse magnetic (TM)] polarized incident wave is used to absorb this polarization, while the TM polarized event wave is totally reflected, and the thermal and electrical tunability of surface conductivity of graphene can be used to control the optical properties of the proposed polarizer, including the selection of the desired polarization, and adjusting the amplitude of the
Abstract: A thermally/electrically tunable graphene on white graphene polarizer is proposed, in which the resonant coupling between the plasmonic surface modes of the structure and the transverse electric (TE) [or transverse magnetic (TM)] polarized incident wave is used to absorb this polarization, while the TM (or TE) polarized incident wave is totally reflected. It is then shown that the thermal and electrical tunability of surface conductivity of graphene can be used to control the optical properties of the proposed polarizer, including the selection of the desired polarization, and adjusting the amplitude of the reflected (desired) polarization. The application of the hexagonal boron-nitride (white graphene) as the substrate of graphene increases the propagation of the surface waves of the structure, which in turn results in the very high polarization extinction ratio of 75 dB. Moreover, the ultra-small insertion loss of 0.022 dB and relatively large bandwidth of ~ 60 nm are calculated for the proposed polarizer.
66 citations
TL;DR: In this paper, a two-dimensional blue phosphorene/molybdenum disulfide (i.e., BlueP/MoS2) heterostructure was used as an interacting layer with analyte to enhance the sensitivity of surface plasmon resonance (SPR) sensor.
Abstract: Sensitivity enhancement of surface plasmon resonance (SPR) sensor is proposed utilizing two-dimensional blue phosphorene/molybdenum disulfide (i.e., BlueP/MoS2) heterostructure as an interacting layer with analyte. The analysis indicates that the proposed sensor design provides significantly higher sensitivity in comparison to conventional and graphene-based SPR sensors. The combined effect of number of heterostructure layers and light wavelength on sensitivity is also analyzed. The results will open a new way to BlueP/MoS2 heterostructure based SPR sensor for bio- and gas-sensing applications in visible and near infrared spectral regions.
66 citations
TL;DR: In this article, a narrowband unitraveling-carrier photodiode (UTC-PD) is used for heterodyne generation of terahertz (THz) communication signals, which is transparent to optical modulation formats.
Abstract: In this letter, we experimentally demonstrate terahertz (THz) photonic wireless transmission of high-speed quadrature-phase-shift-keying (QPSK) and 16 quadrature amplitude modulation (16-QAM) signals in the 350-GHz band, with an effort to extend the wireless reach of ultrafast 100 Gbit/s. In the experiment, a narrowband unitraveling-carrier photodiode (UTC-PD) is used for heterodyne generation of THz communication signals, which is transparent to optical modulation formats. Experimental results show that 30 GBd/s QPSK (60 Gbit/s) and 25 GBd/s 16-QAM signals (100 Gbit/s) are successfully transmitted over a 350-GHz wireless link with an extended distance of 2 m. This enhancement is enabled by combining the techniques of employing cutting-edge narrowband UTC-PD as the photomixing THz emitter, spectrally efficient modulation format and advanced digital signal processing algorithms. The achievement makes 100 Gbit/s THz wireless communication systems promising for future smart wireless services.
TL;DR: In this paper, a low-crosstalk and flat-top 4-channel coarse wavelength-division multiplexing (de)multiplexer is proposed and demonstrated.
Abstract: A low-crosstalk and flat-top 4-channel coarse wavelength-division multiplexing (de)multiplexer is proposed and demonstrated. The cascaded Mach-Zehnder interferometers are used to provide flat pass-bands. By utilizing the power splitters based on the bent directional couplers, the crosstalk of the Mach-Zehnder interferometers could be ultra-low for all four channels. The measurement results of the fabricated device show that the crosstalk is $\sim 300~\mu \text{m} \times 100~\mu \text{m}$ .
TL;DR: In this article, a metal-semiconductor-metal structured photodetector array was designed and fabricated for the first time, and the photo responsivity was shown to be approximately 8.926 × 10−1/W at a 10−V bias voltage.
Abstract: Recently, the $\beta $ -Ga2O3-based solar-blind ultraviolet photodetector has attracted intensive attention due to its wide application prospects. Photodetector arrays can act as an imaging detector and also improve the detecting sensitivity by series or parallel of detector cells. In this letter, the highly integrated metal-semiconductor-metal structured photodetector arrays of $32\times 32$ , $16\times 16$ , $8\times 8$ , and $4\times 4$ have been designed and fabricated for the first time. Herein, we present a 4-1 photodetector cell chosen from a $4\times 4$ photodetector array as an example to demonstrate the performance. The photo responsivity is $8.926 \times 10^{-1}$ A/W @ 250 nm at a 10-V bias voltage, corresponding to a quantum efficiency of 444%. All of the photodetector cells exhibit the solar-blind ultraviolet photoelectric characteristic and the consistent photo responsivity with a standard deviation of 12.1%. The outcome of the study offers an efficient route toward the development of high-performance and low-cost DUV photodetector arrays.
TL;DR: Experimental results for a DML-based 20-Gb/s signal transmission over an 18-km SMF-28e fiber at 1310-nm employing pulse amplitude modulation (PAM)-4 confirm that the proposed ANN-NLE equalizer can increase the channel capacity and significantly reduce the impact of nonlinear penalties.
Abstract: Nonlinear distortion from a directly modulated laser (DML) is one of the major limiting factors to enhance the transmission capacity beyond 10 Gb/s for an intensity modulation direct-detection optical access network. In this letter, we propose and demonstrate a low-complexity nonlinear equalizer (NLE) based on a machine-learning algorithm called artificial neural network (ANN). Experimental results for a DML-based 20-Gb/s signal transmission over an 18-km SMF-28e fiber at 1310-nm employing pulse amplitude modulation (PAM)-4 confirm that the proposed ANN-NLE equalizer can increase the channel capacity and significantly reduce the impact of nonlinear penalties.
TL;DR: In this article, an electrically driven electro-optical modulator integrated with the phase change material Ge¯¯¯¯ 2¯¯¯¯Sb 2 TecffffTecffff 5 (GST) was proposed, which incorporates a hybrid Si-GST-Cu waveguide.
Abstract: We propose an electrically driven electro-optical modulator integrated with the phase-change material Ge
2
Sb
2
Te
5
(GST). This modulator incorporates a hybrid Si-GST-Cu waveguide with input and output Si waveguides. For the waveguide modulator with an active segment of 0.2 μm
2
, the switched phase is stable with off/on extinction ratios of >5.4 dB on the entire C-band. Since the phase change of GST only consumes energy during the stated transitions, the energy consumption per bit for this nanosize device is ideally low on the order of sub-nJ per cycle.
TL;DR: In this article, all optical logic gates (OR, XOR, and NOT) based on hybrid metal insulator metal (HMIM) plasmonic waveguide (Ag-SiO2-Si-Si O2-Ag) have been proposed and designed in the confinement area of $0.25\times 0.04\,\,
Abstract: In this letter, all optical logic gates (OR, XOR, and NOT), based on hybrid metal insulator metal (HMIM) plasmonic waveguide (Ag-SiO2-Si-SiO2-Ag) have been proposed and designed in the confinement area of $0.25\times 0.04\,\,\mu \text{m}^{2}$ at $1.55~\mu \text{m}$ operating wavelength. The proposed logic gates work on principle of linear interference, are designed using Y-splitter. OR and XOR logic gates are designed in footprint area of 17.12 and $19.6~\mu \text{m}^{2}$ , respectively, which is several times miniaturized compared to previous reports. Moreover an intensity contrast ratio of 26 dB has been achieved between ON and OFF states for XOR and NOT logic gates, which is 3 to 4 fold enhanced compared with previous literature. This study opens a new avenue for designing of chip scale plasmonic integrated circuits.
TL;DR: In this article, the authors proposed spatial diversity reception of non-line-of-sight (NLOS) ultraviolet (UV) communication in turbulent atmospheric channel, where one branch is only connected to the receiver at any instant using appropriate switching logic.
Abstract: In this letter, we propose spatial diversity reception of non-line-of-sight (NLOS) ultraviolet (UV) communication in turbulent atmospheric channel. The turbulent atmospheric channel causes fluctuation in the received signal intensity of a UV system, resulting in power loss and subsequent performance degradation at the receiver. To mitigate this adverse effect, we present the spatial diversity reception in the form of dual-branch switch and stay combining (SSC) at the receiver. That is, one branch is only connected to the receiver at any instant using appropriate switching logic. The channels are assumed to be exponentially correlated in space, while irradiance fluctuation due to turbulence is modeled by a Gamma–Gamma distribution with parameters directly related to the attributes of the NLOS UV link. Analytic expressions for both the outage probability and the average symbol error probability are derived using the SSC diversity technique with the correlated receivers.
TL;DR: In this paper, the authors numerically demonstrate and propose sensitivity enhancement of surface plasmon resonance (SPR)-based conventional gaseous sensor using few layers of black phosphorous (BP), as compared with other 2D material such as graphene and molybdenum disulphide (MoS2).
Abstract: We numerically demonstrate and propose sensitivity enhancement of surface plasmon resonance (SPR)-based conventional gaseous sensor using few layers of black phosphorous (BP), as compared with other 2D material such as graphene and molybdenum disulphide (MoS2). Results of our optimized numerical study show that with implementation of bilayer BP over a conventional gaseous sensor, sensitivity enhances by ~35%, which is further increased up to ~73% by addition of a monolayer MoS2 at an operating wavelength $\lambda =633$ nm. Therefore, the proposed SPR gaseous sensor could potentially open a new platform for high-performance gaseous sensing in the visible region.
TL;DR: In this paper, the authors report the inscription of fiber Bragg gratings (FBGs) and Fabry-Perot (FP) cavities in a gradient index cyclized transparent optical polymer (CYTOP) polymer optical fiber (POF) using a femtosecond laser.
Abstract: We report the inscription of fiber Bragg gratings (FBGs) and Fabry-Perot (FP) cavities in a gradient index cyclized transparent optical polymer (CYTOP) polymer optical fiber (POF) using a femtosecond laser. Through careful control of the inscription parameters, the coupling between the grating and the fiber’s higher order propagation modes is reduced, allowing for single peak grating spectra. Furthermore, we inscribe a 10-nm chirped grating and an FBG FP cavity with a free spectral range of 240 pm. We measure the group delay of the chirped grating and characterize the fiber FP cavity for strain and temperature.
TL;DR: In this article, a gallium arsenide (GaAs) single-junction photovoltaic (PV) cell was shown to achieve a power efficiency of at least 42% when irradiance of 0.46 W/cm2 is received from an 847-nm vertical-cavity surface-emitted laser.
Abstract: In this letter, we demonstrate for the first time the additional capability of high-speed data communication for single-junction photovoltaic (PV) cells. A record 3-dB bandwidth of 24.5 MHz is reported for a gallium arsenide (GaAs) PV cell. The PV cell is shown to achieve a power efficiency of at least 42% when irradiance of 0.46 W/cm2 is received from 847-nm vertical-cavity surface-emitted laser. Optimized bit-and-power-loaded optical orthogonal frequency-division multiplexing (OFDM) is applied to use the communication bandwidth most efficiently. With this, a data rate of 0.5 Gb/s is achieved for a 2-m OFDM-based laser link. To the best of our knowledge, the reported data rates achieved with a GaAs PV cell as the detector are the highest for simultaneous optical wireless information and power transfer.
TL;DR: This letter investigates the power allocation problem for the downlink of an orthogonal frequency division multiple (OFDM)-based non-orthogonal multiple access visible light communication (NOMA-VLC) system and derives the optimal power ratio for an arbitrary number of multiplexed users in OFDM-NOMa VLC.
Abstract: This letter investigates the power allocation problem for the downlink of an orthogonal frequency division multiple (OFDM)-based non-orthogonal multiple access visible light communication (NOMA-VLC) system. Unlike the commonly used two-user OFDM-NOMA VLC model, in this letter, an arbitrary number of multiplexed users is considered when formulating the sum rate maximization problem. Moreover, both user-level and subcarrier-level power optimization are taken into account to improve the system performance. The corresponding theoretical analysis is presented, with the consideration of optimal decoding order and each user's required signal-to-interference-plus-noise ratio (SINR). Given a fixed power constraint on each OFDM subcarrier, we derive the optimal power ratio for an arbitrary number of multiplexed users in OFDM-NOMA VLC. Numerical results show that with a required SINR of 3 dB, the proposed enhanced power allocation algorithm has 39.59% and 40.11% sum-rate enhancement when compared to optimized fixed power allocation algorithm and gain ratio power allocation algorithm, respectively.
TL;DR: In this article, an asymmetrical birefringence photonic crystal fiber based on a surface plasmon resonance (SPR) sensor designed to detect the low analyte refractive indexes is investigated.
Abstract: An asymmetrical birefringence photonic crystal fiber based on a surface plasmon resonance (SPR) sensor designed to detect the low analyte refractive indexes is investigated by a novel birefringence analysis method The results show that the birefringent analysis method can replace the conventional confinement loss method pertaining to the investigation SPR on the asymmetrical structures The air holes in the sensor are arranged in a square lattice structure and two active plasmonic gold layers are deposited on the inner surface of the left and right channels to enhance the SPR phenomenon The birefringence sensor shows a broad refractive index detection range from 1 to 143 with the maximum wavelength sensitivity of 6300 nm/RIU
TL;DR: A physical-layer encryption scheme is proposed and experimentally demonstrated in orthogonal frequency division multiplexing passive optical network (OFDM-PON) and the dynamic parameters of constellation shifting are generated by a 3-D hyper digital chaos.
Abstract: A physical-layer encryption scheme is proposed and experimentally demonstrated in orthogonal frequency division multiplexing passive optical network (OFDM-PON). In the proposed multifold encryption scheme, quadratic-amplitude modulation (QAM) symbols are scrambled and distributed onto the complex plane independently. The dynamic parameters of constellation shifting are generated by a 3-D hyper digital chaos, in which a key space of ~10162 is created to enhance the security level of OFDM data encryption during transmission. An encrypted data transmission of 9.4-Gb/s, 16-QAM optical OFDM signals is successfully demonstrated over 20-km standard single-mode fiber.
TL;DR: In this paper, a novel fiber sensor, which enables us to simultaneously measure the torsion, strain, and temperature, is proposed and experimentally demonstrated, which is based on utilization of two successively cascaded helical long-period fiber gratings (TSC-HLPGs).
Abstract: A novel fiber sensor, which enables us to simultaneously measure the torsion, strain, and temperature, is proposed and experimentally demonstrated, which is based on utilization of two successively cascaded helical long-period fiber gratings (TSC-HLPGs). By using the proposed approach, crosstalk effects among temperature, strain, and torsion can totally be discriminated for the first time to the best of our knowledge. Moreover, not only the torsion angle, but also the torsion direction can be determined simultaneously. Accuracies for the resolved temperature, the strain, and the torsion angle are estimated to be ~0.8 °C within the range of 20 °C–100 °C, $\sim 225~\mu \varepsilon $ within the range of 0- $2600~\mu \varepsilon $ , and ~1.2° (corresponding to a torsion responsivity of 3.54 nm/rad/m in our case) within the rotation angle of −360° ~ 360°, respectively.
TL;DR: In this paper, the authors demonstrate high performance vertical solar-blind Schottky photodetectors on MBE-grown homoepitaxial (010)-oriented Ga2O3 films.
Abstract: In this letter, we demonstrate high-performance vertical solar-blind Schottky photodetectors on MBE-grown homoepitaxial (010)-oriented $\beta $ -Ga2O3 films. The structure, consisting of (100 nm) $\beta $ -Ga2O3/(60 nm) $\text{n}^{++} \beta $ -Ga2O3, was grown on a Fe-doped insulating (010) $\beta $ -Ga2O3 substrate. Ni/Au and indium were used as the Schottky and Ohmic contacts, respectively. The devices exhibited a rectification ratio of ~107 with turn-on voltage ~1 V and an ideality factor of 1.31. The extracted Schottky barrier height was 1.4 eV. The photodetectors showed low dark current of 0.3 nA at 5 V with a photo-to-dark current ratio of ~102 at 0 V. The devices exhibited a zero-bias responsivity of 4 mA/W at 254 nm corresponding to an external quantum efficiency ~3 %, with a UV-to-visible rejection ratio >103, showing true solar-blind operation. The transient response of the devices indicated rise/fall times of ~100 ms. Temperature-dependent current–voltage characteristics agree with the thermionic emission model.
TL;DR: In this paper, a three-mode MDM multiplexer (MUX) and de-multiplexer was designed and used with an aggregate transmission capacity of 2.6 Tbit/s with all channels satisfying the hard-decision forward error correction threshold.
Abstract: In this letter, we combine the use of dense-wavelength-division-multiplexing and mode-division-multiplexing (MDM) with advanced-modulation formats for on-chip optical interconnects. A three-mode MDM multiplexer (MUX) and de-multiplexer (DEMUX) was designed and used. Each wavelength carrier had an aggregate data rate of 192-Gbit/s using 4-level pulse-amplitude-modulation. The mode crosstalk of the MDM MUX/DEMUX was measured to be below −20 dB in the 40-nm wavelength band from 1520 to 1560 nm. Fourteen wavelength channels are multiplexed and successfully transmitted with an aggregate transmission capacity of 2.6 Tbit/s (14 wavelengths $\times$ 3 modes $\times$ 64 Gbit/s) with all channels satisfying the hard-decision forward-error-correction threshold. Numerical analysis of the mode crosstalk is also performed.
TL;DR: A novel multilevel-intensity modulation (m-IM) scheme for a rolling-shutter (RS)-based OCC is introduced and the performance of the proposed system is compared to a typical modulation scheme for OCC system, such as ON–OFF keying.
Abstract: High data transmission rates are desirable in an optical camera communication (OCC) system. In order to achieve this, a novel multilevel-intensity modulation (m-IM) scheme for a rolling-shutter (RS)-based OCC is introduced in this letter. The proposed multilevel intensity signal is obtained by transmitting the signal pulse time faster than the camera shutter speed, where the shutter speed is highly dependent on the camera exposure time and the RS-effect of CMOS-image sensor of the camera. In addition, pulse width modulation is also used on the transmitter side to control the output intensity (signal pulse) of the LED transmitter. As the optical signal is received wirelessly by the camera, we further propose a novel smartphone-based digital demodulation algorithm for our RS-based OCC system. In this letter, we compare the performance of the proposed system to a typical modulation scheme for OCC system, such as ON–OFF keying. Moreover, an intensive performance test is conducted for different symbol times to determine their relationship to bit error rate and achieved data rate. A data transmission rate >10 kbps over a range of up to 2 m by using a 30 fps smartphone camera can be achieved by using our proposed 4-IM in our proposed scheme.
TL;DR: Numerical simulations show that the proposed support vector machine-based algorithm achieves a very good modulation classification (MC) performance, as well as high OSNR estimation accuracy with a maximum estimation error of 0.8 dB.
Abstract: By adopting the cumulative distribution function of the received signal’s amplitude as feature, a support vector machine-based algorithm is proposed to jointly classify the modulation format and estimate the optical signal-to-noise ratio (OSNR) in coherent optical communication systems. Three commonly-used quadrature-amplitude modulation (QAM) formats are considered. Numerical simulations have been carried out in the OSNR ranges from 5 to 30 dB, and results show that the proposed algorithm achieves a very good modulation classification (MC) performance, as well as high OSNR estimation accuracy with a maximum estimation error of 0.8 dB. Optical back-to-back experiments are also conducted in OSNR ranges of interest. A 99% average correct MC rate is observed, and mean OSNR estimation errors of 0.38, 0.68, and 0.62 dB are noticed for 4-QAM, 16-QAM, and 64-QAM, respectively. Furthermore, compared with the neural networks-based joint estimation algorithm, the proposed algorithm attains better performance with comparable complexity.
TL;DR: This work proposes an alternative receiver for nonlinear frequency division multiplexing optical communication systems using techniques from machine learning that is highly adaptive as it learns from previously transmitted pulses and thus holds no assumptions on the system and noise distribution.
Abstract: The nonlinear Fourier transform is a new approach for addressing the capacity limiting Kerr nonlinearities in optical communication systems. It exploits the property of integrability of the lossless nonlinear Schrodinger equation and thus incorporates nonlinearities as an element of the transmission. However, practical links employing erbium-doped fiber amplifiers include losses/gains and introduce noise which breaks the integrability of the nonlinear Schrodinger equation. Although the lossless path average approximation proposes an integrable model, its imprecision still leads to unintended distortions and thus performance degradation. We propose an alternative receiver for nonlinear frequency division multiplexing optical communication systems using techniques from machine learning. It is highly adaptive as it learns from previously transmitted pulses and thus holds no assumptions on the system and noise distribution. The detection method presented is fully applied in time-domain and omits the nonlinear Fourier transform. The numerical results provide a benchmark for nonlinear Fourier transform based detection of high order solitons for fiber links with losses and noise present.
TL;DR: In this paper, a Fabry-Perot (FP) cavity was used to enhance the localized surface plasmon resonances (LSPRs) of metallic nanoparticles for high-quality sensing.
Abstract: We report an effective strategy to enhance the localized surface plasmon resonances (LSPRs) of metallic nanoparticles by introducing a Fabry–Perot (FP) cavity for high-quality sensing. The concept is based on the combined excitation of LSPRs in metallic nanoparticles and optical cavity modes supported by the FP cavities, whose strong interactions result in two ultra-narrowband hybridized plasmon modes with a huge electric field enhancement. A high-quality double-band plasmonic nanosensor, with the refractive index sensitivity approaching 600 nm/RIU and a figure of merit exceeding 28 is achieved here, which suggests that the cavity-coupling strategy could offer new perspectives for achieving ultra-compact efficient biosensors.