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In this paper, we demonstrate a stable output single-longitudinal-mode (SLM) Erbium-doped fiber laser (EDFL) with eight selectable wavelengths. The EDFL achieves wavelength selection through a 1 × 8 arrayed waveguide grating (AWG) and generates SLM output using the passive triple subring resonator (PTSR) architecture. In the experimental measurements, we separately measured the wavelength, power, and optical signal-to-noise ratio (OSNR) for all eight channels. The experimental results show a wavelength spacing of approximately 0.8 nm, with OSNRs around 60 dB and powers around 2.5 dBm for each channel. The power and OSNR for all eight wavelengths show very little variation. Finally, we measured that the laser outputs are all SLM, and the measured linewidths are all less than 2.5 kHz.

In this demonstration, we present two erbium-doped fiber (EDF) lasers, with series and parallel three sub-ring configurations, respectively, to achieve tunable channel output and stable single longitudinal mode (SLM) operation in the L-band range. Here, the fiber ring cavity contains the L-band EDF as a gain medium. Based on the measured results of the two quad-ring structures of the EDF lasers, tunable output bandwidth for the two lasers can be obtained from 1558.0 to 1618.0 nm simultaneously. All the 3 dB linewidths measured for both fiber lasers are 312.5 Hz over the effective wavelength output range. Furthermore, the related optical signal-to-noise ratio (OSNR), output power, output stabilities of the central wavelength and power, and equal output power range of the two proposed EDF lasers are also examined and discussed.

In this study, we proposed an adaptive successive interference cancellation (SIC) technique to enhance non-orthogonal multiple access visible light communication (NOMA-VLC) and demonstrate its effectiveness using extensive simulations. NOMA-VLC is a promising technology for high-speed wireless communication, but interference from multiple users can pose a significant challenge. SIC is a technique that can help mitigate this interference. We used non-return to zero (NRZ) modulation to achieve high bit rates up to 2 Gbps and evaluated the performance using bit error rate (BER) analysis. Our simulation showed that the static power allocation (SPA) performance on the NOMA-VLC system achieved a BER value of around 10-3 for both users, using power allocation We also compared SPA against gain ratio power allocation (GRPA) and found that the performance of GRPA was not as good, with a BER value around 10-2. Our results show the effectiveness of the proposed SIC technique in enhancing the performance of NOMA-VLC.

To reduce the error induced by overfitting or underfitting in predicting non-invasive fasting blood glucose (NIBG) levels using photoplethysmography (PPG) data alone, we previously demonstrated that incorporating HbA1c led to a notable 10% improvement in NIBG prediction accuracy (the ratio in zone A of Clarke’s error grid). However, this enhancement came at the cost of requiring an additional HbA1c measurement, thus being unfriendly to users. In this study, the enhanced HbA1c NIBG deep learning model (blood glucose level predicted from PPG and HbA1c) was trained with 1494 measurements, and we replaced the HbA1c measurement (explicit HbA1c) with “implicit HbA1c” which is reversely derived from pretested PPG and finger-pricked blood glucose levels. The implicit HbA1c is then evaluated across intervals up to 90 days since the pretest, achieving an impressive 87% accuracy, while the remaining 13% falls near the CEG zone A boundary. The implicit HbA1c approach exhibits a remarkable 16% improvement over the explicit HbA1c method by covering personal correction items automatically. This improvement not only refines the accuracy of the model but also enhances the practicality of the previously proposed model that relied on an HbA1c input. The nonparametric Wilcoxon paired test conducted on the percentage error of implicit and explicit HbA1c prediction results reveals a substantial difference, with a p-value of 2.75 × 10–7.

Inthe work, we study and express a new wavelength-division-multiplexing passive optical network (WDM-PON) architecture with fiber fault protection. The designed optical network unit (ONU) module and periodic spectrum of 2 × N array waveguide grating (AWG) are applied to produce the self-protected mechanism. Here, we employ the free space optical communication (FSO)- and fiber-based connection between two adjacent ONUs to achieve signal relink. Moreover, the corresponding signal performances of downstream and upstream are also analyzed and discussed.

Underwater wireless optical communication (UWOC) is a promising solution for Gb/s rate and long-distance underwater communication. However, random changes in the local temperature and salinity of seawater have caused different refractive indices of ocean water. This study investigated the UWOC system in different saline water while simultaneously changing the temperature and water flow. A maximum bit error rate (BER) of 4.851 × 10−6 was measured at −7.41 dBm in 3 m of 45.56 g/L saline water. By changing the temperature to 30 °C, the bit error rate (BER) value reached 5.12 × 10−6 in the saline water. On the other hand, water flow was generated in various types of water salinity to compare simultaneous environmental effects in the UWOC system. In 45.56 g/L of saline water with water flow, the UWOC system was still capable of reaching a BER value of 4 × 10−4.

Based on the coupled Ginzburg-Landau equations and Jones matrices of the waveplates considered, a numerical model of an all-normal-dispersion fiber laser mode-locked by nonlinear polarization rotation has been proposed. The operating characteristics of the fiber laser discussed were studied numerically. It has been found that the proposed all-normal-dispersion mode-locked fiber laser (AND-MLFL) could deliver dissipative solitons (DSs) with a M-shaped and U-shaped spectrum, the splitting pulse with a divided spectrum and the amplifier similaritons. The evolution of the intra-cavity pulse and spectrum has been calculated under different regimes and the effects of group velocity dispersion (GVD) and nonlinearity are analyzed. When the fiber laser delivers DSs or causes pulse splitting, nonlinear effects dominate the pulse evolution. With the increase of the accumulated nonlinear phase shift, the operation states change from DS with a M-shaped spectrum to a U-shaped spectrum, and then to the splitting pulse. In the case of amplifier similaritons, both the GVD and nonlinearity play important roles in pulse evolution. The effect of nonlinear polarization rotation and filtering on the pulse reshaping has been analyzed. When the fiber laser delivers DSs with a M-shaped spectrum, the filter has a very weak effect on the pulse and on spectral reshaping. However, when the fiber laser operates in the amplifier similariton state, the filter plays a key role in pulse and spectral reshaping, whereas the nonlinear polarization rotation become less dominant. The dependence of the operational states on the filter bandwidth, fiber length, small signal gain coefficient and orientation of waveplates has also been calculated. A Yb-doped doubled-cladding fiber laser, mode-locked by nonlinear polarization rotation, has also been demonstrated and all of the four pulse regimes are obtained experimentally.

In this paper, we propose a long-reach star-ring-based timeand wavelength-divisionmultiplexing passive optical network (TWDM-PON) by using fiberand free space optical (FSO)-protected architecture against fiber breakpoint. Here, the new fiber-based and FSO-based optical network unit (ONU) modules are designed in the PON system to achieve the self-protected operation. Thus, the adjacent ONU is linked to produce the fiberor FSO-based reconnections. Thus, 4 × 10 Gbit/s downstream and 10 Gbit/s upstream signals can be reached through 70 km fiber transmission and a length of free space link without signal amplification and dispersion compensation. Moreover, the relationships of splitter ratio and FSO link length in the proposed TWDM access network are also analyzed and discussed.

The objective of the proposed human–machine cooperation (HMC) workstation is to both rapidly detect calcium-based fish bones in masses of minced fish floss and visually guide operators in approaching and removing the detected fish bones by hand based on the detection of fingernails or plastic-based gloves. Because vibration is a separation mechanism that can prevent absorption or scattering in thick fish floss for UV fluorescence detection, the design of the HMC workstation included a vibration unit together with an optical box and display screens. The system was tested with commonly used fish (swordfish, salmon, tuna, and cod) representing various cooking conditions (raw meat, steam-cooked meat, and fish floss), their bones, and contaminating materials such as derived from gloves made of various types of plastic (polyvinylchloride, emulsion, and rubber) commonly used in the removal of fish bones. These aspects were each investigated using the spectrum analyzer and the optical box to obtain and analyze the fluorescence spectra and images. The filter was mounted on a charge-coupled device, and its transmission-wavelength window was based on the characteristic band for fish bones observed in the spectra. Gray-level AI algorithm was utilized to generate white marker rectangles. The vibration unit supports two mechanisms of air and downstream separation to improve the imaging screening of fish bones inside the considerable flow of fish floss. Notably, under 310 nm ultraviolet B (UVB) excitation, the fluorescence peaks of the raw fillets, steam-cooked meat, and fish floss were observed at for bands at longer wavelengths (500–600 nm), whereas those of the calcium and plastic materials occurred in shorter wavelength bands (400–500 nm). Perfect accuracy of 100% was achieved with the detection of 20 fish bones in 2 kg of fish floss, and the long test time of around 10–12 min results from the manual removal of these fish bones.

In this research, we present and design a blended wavelength-division-multiplexing passive optical network (WDM-PON) architecture to deliver both baseband and free-space optical (FSO) signals by using two wavelength bands over an available bandwidth to avoid the signal interference. Only using few additional components in the optical line termination (OLT) and optical network unit (ONU)/optical wireless unit (OWU) can achieve self-protected operation in the presented hybrid fiber-FSO access network against fiber breakage. In the measurement, eight WDM wavelengths with 24.3 Gbit/s on-off keying (OOK) modulation format are applied to verify and discuss the bit error rate (BER) performances of baseband and FSO signals, respectively, through 25 km fiber and 2 m wireless FSO connections. Therefore, the presented PON not only can deliver both baseband and FSO traffics, but can also provide a self-restored mechanism against fiber fault.

Poly(methacrylic acid) (PMAA) brushes were tethered on a silicon surface possessing a 500-nm hole array via atom transfer radical polymerization after the modification of the halogen group. Dextran-biotin (DB) was sequentially immobilized on the PMAA chains to obtain a P(MAA-DB) brush surrounding the hole edges on the silicon surface. After loading antibiotics inside the holes, biphenyl-4,4′-diboronic acid (BDA) was used to cross-link the P(MAA-DB) chains through the formation of boronate esters to cap the hole and block the release of the antibiotics. The boronate esters were disassociated with reactive oxygen species (ROS) to open the holes and release the antibiotics, thus indicating a reversible association. The total amount of drug inside the chip was approximately 52.4 μg cm−2, which could be released at a rate of approximately 1.6 μg h−1 cm−2 at a ROS concentration of 10 nM. The P(MAA-DB) brush-modified chip was biocompatible without significant toxicity toward L929 cells during the antibiotic release. The inflammation-triggered antibiotic release system based on a subcutaneous implant chip not only exhibits excellent efficacy against bacteria but also excellent biocompatibility, recyclability, and sensitivity, which can be easily extended to other drug delivery systems for numerous biomedical applications without phagocytosis- and metabolism-related issues.

A simple, low-cost, single-longitudinal mode, C-band narrow-linewidth optical fiber laser is presented based on the methodology of the Rayleigh backscattering (RBS). In this paper, a 1551 nm fiber ring laser is developed, and single-mode fiber (SMF) is added to compress the line width. When the SMF length of the RBS cavity is 120 m, the laser has better performance than that in other SMF lengths with a laser line width of 1.46 KHz with housing shield. The optical signal-to-noise ratio (OSNR) is 59.86 dB, and its maximum output power is 9.4 mW. It can quickly achieve the single longitude-mode operation by controlling the variable optical attenuator (VOA). The bit error rate at 10 Gb/s PRBS NRZ modulation is measured to be 10−9 when the optical receiving power is −16.2 dBm.

We report a harmonic dissipative soliton 1.93 μm thulium fiber laser based on a tungsten disulfide (WS2) saturable absorber (SA) in the anomalous dispersion regime. The multilayer WS2 nanosheets were prepared by liquid phase exfoliation method and the SA was fabricated by dropping WS2 solution onto a gold mirror. The transferred WS2 SA had a modulation depth of 2.5% and a saturation intensity of 0.82 MW/cm2. By incorporating the SA into a linear Tm3+ fiber laser cavity, harmonic mode-locked dissipative soliton laser was achieved at 1930 nm with the spectral width of 8 nm, the pulse energy of 3 nJ, the pulse width of 3.6 ns, and the repetition rate of 56.3 MHz. Based on the experimental results, it is shown that with the presence of harmonic mode-locking in 2 μm wavelength region, the multilayer WS2 serving as a SA was verified to be a good candidate for broadband high-energy mode-locking. The order of the harmonic dissipative soliton mode-locked pulses remains the same along with the increasing pump power.

Infections of orchids by the Odontoglossum ringspot virus or Cymbidium mosaic virus cause orchid disfiguration and are a substantial source of economic loss for orchid farms. Although immunoassays can identify these infections, immunoassays are expensive, time consuming, and labor consuming and limited to sampling-based testing methods. This study proposes a noncontact inspection platform that uses a spectrometer and Android smartphone. When orchid leaves are illuminated with a handheld optical probe, the Android app based on the Internet of Things and artificial intelligence can display the measured florescence spectrum and determine the infection status within 3 s by using an algorithm hosted on a remote server. The algorithm was trained on optical data and the results of polymerase chain reaction assays. The testing accuracy of the algorithm was 89%. The area under the receiver operating characteristic curve was 91%; thus, the platform with the algorithm was accurate and convenient for infection screening in orchids.

To increase the data capacity of a light-emitting diode (LED) based visible light communication (VLC) transmission, a polarization-division-multiplexing (PMD) green (G)- and blue (B)- light-based transmitter (Tx) module is demonstrated here. It was demonstrated that we can achieve 1200 and 1120 Mbps VLC capacities based on dual-polarized G- and a B-LED based light wave after 3 and 4 m free-space link lengths, respectively, at exceedingly low illuminance. Based on the presented VLC system, paired G-LEDs or B-LEDs with dual-polarization can also be applied on the VLC-Tx side for doubling and delivering VLC data. According to the obtained results, the largest polarization offset angle of 50° between two polarizers (POLs) can be allowed experimentally to provide optimal VLC traffic. Moreover, the relationships of polarization offset, the illuminance of LED and maximum achieved VLC capacity are also performed and analyzed.

Distributed fiber sensing (DFS) can provide real-time signals and warnings. The entire length of fiber optic cable can act as a sensing element, but the accuracy is sometimes limited. On the other hand, point-to-point fiber sensing (PPFS) is usually implemented using one or more fiber Bragg gratings (FBGs) at specific positions along with the fiber for the monitoring of specific parameters (temperature, strain, pressure, and so on). However, the cost becomes expensive when the number of FBGs increases. A hybrid fiber sensing scheme is thus proposed, combining the advantages of DFS and PPFS. It is based on a Brillouin optical time-domain analysis (BOTDA) fiber system with additional FBGs embedded at certain positions where it is necessary to detect specific parameters. The hybrid fiber sensing system has the advantages of full sensing coverage at essential locations that need to be carefully monitored. In our work, the test results showed that the proposed system could achieve a sensing distance of 16 km with the single-mode fiber with a 2 m spatial resolution. For FBG parameter measurements, the temperature variation was 52 °C, from 25 °C to 77 °C, with a temperature sensitivity of 23 pm/°C, and the strain was from 0 to 400 µε, with a strain sensitivity of 0.975 pm/µε, respectively, using two FBGs.

The segmentation of capillaries in human skin in full-field optical coherence tomography (FF-OCT) images plays a vital role in clinical applications. Recent advances in deep learning techniques have demonstrated a state-of-the-art level of accuracy for the task of automatic medical image segmentation. However, a gigantic amount of annotated data is required for the successful training of deep learning models, which demands a great deal of effort and is costly. To overcome this fundamental problem, an automatic simulation algorithm to generate OCT-like skin image data with augmented capillary networks (ACNs) in a three-dimensional volume (which we called the ACN data) is presented. This algorithm simultaneously acquires augmented FF-OCT and corresponding ground truth images of capillary structures, in which potential functions are introduced to conduct the capillary pathways, and the two-dimensional Gaussian function is utilized to mimic the brightness reflected by capillary blood flow seen in real OCT data. To assess the quality of the ACN data, a U-Net deep learning model was trained by the ACN data and then tested on real in vivo FF-OCT human skin images for capillary segmentation. With properly designed data binarization for predicted image frames, the testing result of real FF-OCT data with respect to the ground truth achieved high scores in performance metrics. This demonstrates that the proposed algorithm is capable of generating ACN data that can imitate real FF-OCT skin images of capillary networks for use in research and deep learning, and that the model for capillary segmentation could be of wide benefit in clinical and biomedical applications.

Underwater wireless optical communication (UWOC) has been considered a promising technology for high-speed underwater transmission. Some Gb/s level UWOC systems applying visible light have been demonstrated with a transmission distance of several meters or more. Many of the previous works focus on the advanced technologies to push the systems’ capacity–distance performance. However, practical environmental factors issue such as flow turbulence and temperature variation are seldom studied through specific statistical/theoretical models. In this paper, a UWOC system using a 450 nm blue light laser source was set up using a 1.5-m water tank with mirrors located on both sides for single or multiple reflections corresponding to different transmission distances. The blue laser was modulated by a 1.25 Gbps NRZ-OOK format with PRBS of 7, 24 or 31, respectively, for system performance comparison. The bit error rate (BER) values were measured in 1.5, 3.0 and 6 m, respectively, for system evaluation. At room temperature, the BER value was down to 10 × 10−8 for a 1.25 Gbps data rate in a 6 m transmission. Then, the UWOC transmission system experiment was carried out under several environmental parameters such as temperature, turbulence, artificial seawater by adding salt to simulate practical application in river or sea. When a submerged motor with an output of 1200 L/h was used as a water flow turbulence source, the impact to BER and transmission quality was negligible. For the temperature change issue, the experiment shows that around the original temperature of 25 °C had the best BER as compared to other temperature ranges from 10 to 50 °C. For artificial seawater issues by adding salt to simulate the real seawater environment. The transmission distance was only 3-m instead of 6 m, mainly due to particle scattering and water disturbance. With the motor pump on, the power penalty was 1 dB at 10 × 10−8 BER when compared to the motor pump off.

Fiber Bragg gratings (FBGs) are widely applied in optical sensing systems due to their advantages including being simple to use, high sensitivity, and having great potential for integration into optical communication systems. A common method used for FBG sensing systems is wavelength interrogation. The performance of interrogation based sensing systems is significantly determined by the accuracy of the wavelength peak detection processing. Direct maximum value readout (DMVR) is the simplest peak detection method. However, the detection accuracy of DMVR is sensitive to noise and the sampling resolution. Many modified peak detection methods, such as filtering and curve fitting schemes, have been studied in recent decades. Though these methods are less sensitive to noise and have better sensing accuracy at lower sampling resolutions, they also confer increased processing complexity. As massive sensors may be deployed for applications such as the Internet of things (IoT) and artificial intelligence (AI), lower levels of processing complexity are required. In this paper, an efficient scheme applying a three-point peak detection estimator is proposed and studied, which shows a performance that is close to the curve fitting methods along with reduced complexity. A proof-of-concept experiment for temperature sensing is performed. 34% accuracy improvement compared to the DMVR is demonstrated.

In this paper, a 10-Gb/s hybrid optical fiber (OF) and free-space optics (FSO) link as part of a bidirectional long-haul OF transmission for application in outdoor environments such as bridges is proposed. A fiber-Bragg-grating (FBG) sensor head is used for monitoring the condition of a bridge, and in the case of the bridge being damaged, the transmission path is changed over from OF to the FSO link to ensure link connectivity. An Erbium-doped fiber amplifier is used to compensate for losses due to the fiber cable and the free-space channel. At a bit error rate (BER) of 10e-9, the power penalty between the OF and FSO paths is

It has been shown that impact damage to composite materials can be revealed by embedded Fiber Bragg Gratings (FBG) as a broadening and splitting of the latter’s characteristic narrow peak reflected spectrum. The current work further subjected the impact damaged composite to cyclic loading and found that the FBG spectrum gradually submerged into a rise of background intensity as internal damages progressed. By skipping the impact, directing the impact to positions away from the FBG and examining the extracted fibers, we concluded that the above change is not a result of deterioration/damage of the sensor. It is caused solely by the damages initiated in the composite by the impact and aggravated by fatigue loading. Evolution of the grating spectrum may therefore be used to monitor qualitatively the development of the incurred damages.

We demonstrate a practical 2×80 Gbit/s dense wavelength division multiplexing (DWDM) bidirectional short-range optical wireless link. The measured power penalties for the bidirectional transmission are less than 0.8 and 0.2 dB compared to the back-to-back link and the unidirectional transmission system, respectively. We also practically evaluate the impact of the offset angles between the optical transmission path and the building windows. The result shows that the power penalty is as small as 0.3 dB. This technology offers a great potential for applications in building-to-building inter-transmission as part of local/wide area networks.