The tested component's coupling efficiency reached 67.52%, and its insertion loss measured 0.52 dB, achieved via optimized preparation conditions and structural parameters. Our best information indicates that this is the first instance of a tellurite-fiber-based side-pump coupler. The fused coupler introduced below is poised to significantly simplify the myriad designs of mid-infrared fiber lasers and amplifiers.

To enhance the performance of high-speed, long-reach underwater wireless optical communication (UWOC) systems by overcoming bandwidth limitations, this paper introduces a joint signal processing scheme comprising a subband multiple-mode full permutation carrierless amplitude phase modulation (SMMP-CAP), a signal-to-noise ratio weighted detector (SNR-WD), and a multi-channel decision feedback equalizer (MC-DFE). The 16 quadrature amplitude modulation (QAM) mapping set is fragmented into four 4-QAM mapping subsets, as dictated by the SMMP-CAP scheme, leveraging the trellis coded modulation (TCM) subset division strategy. Within the fading channel, the demodulation effect of this system is significantly improved by the integration of an SNR-WD and an MC-DFE. Under a hard-decision forward error correction (HD-FEC) threshold of 38010-3, the laboratory experiment quantified the required received optical powers (ROPs) as -327 dBm, -313 dBm, and -255 dBm, respectively, for data transmission rates of 480 Mbps, 600 Mbps, and 720 Mbps. Subsequently, the system successfully achieves a data rate of 560 Mbps in a swimming pool with a transmission distance up to 90 meters, resulting in a total attenuation of 5464dB. From what we currently know, this is the first time that a high-speed, long-range UWOC system has been showcased, adopting the SMMP-CAP scheme.

In an in-band full-duplex (IBFD) transmission system, the receiving signal of interest (SOI) can be severely distorted due to self-interference (SI) caused by signal leakage from a nearby transmitter. By superimposing a local reference signal of equivalent magnitude and inverted phase, the effect of the SI signal is completely nullified. latent infection However, manual operation of the reference signal manipulation process frequently compromises the attainment of both high speed and high precision cancellation. A real-time adaptive optical signal interference cancellation scheme (RTA-OSIC), employing a SARSA reinforcement learning (RL) algorithm, is proposed and validated through experimentation to address this issue. The proposed RTA-OSIC scheme employs a variable optical attenuator (VOA) and a variable optical delay line (VODL) to automatically adjust the amplitude and phase of a reference signal. This adjustment is accomplished using an adaptive feedback signal that is generated by assessing the quality of the received SOI. The effectiveness of the proposed 5GHz 16QAM OFDM IBFD transmission system is demonstrated experimentally. The signal recovery for an SOI at three bandwidths (200 MHz, 400 MHz, and 800 MHz) is achieved adaptively and correctly within eight time periods (TPs), which corresponds to the time requirement for a single adaptive control step, using the proposed RTA-OSIC scheme. The SOI's cancellation depth, operating at 800MHz bandwidth, is precisely 2018dB. Dispensing Systems The proposed RTA-OSIC scheme's short-term and long-term stability is also examined. The experimental results provide compelling evidence that the proposed approach holds considerable promise as a real-time adaptive SI cancellation solution for future IBFD transmission systems.

Modern electromagnetic and photonics systems rely heavily on the crucial function of active devices. The prevailing approach for creating active devices involves integrating epsilon-near-zero (ENZ) with low Q-factor resonant metasurfaces, substantially enhancing nanoscale light-matter interactions. Still, the low resonance Q-factor could constrain the optical modulation's performance. Fewer studies have investigated optical modulation within low-loss, high-Q-factor metasurfaces. An effective method for producing high Q-factor resonators has recently been established by the emergence of optical bound states in the continuum (BICs). Numerical simulations in this work reveal a tunable quasi-BICs (QBICs) configuration achieved via the integration of a silicon metasurface and an ENZ ITO thin film. selleckchem A unit cell containing five square holes within the metasurface design; the pivotal position of the central hole influences the generation of multiple BICs. Multipole decomposition and near-field distribution calculations allow us to also reveal the nature of these QBICs. We demonstrate active control over the resonant peak position and intensity of the transmission spectrum, achieved by integrating ENZ ITO thin films onto silicon metasurfaces which are supported by QBICs. This control arises from the high Q-factor enabled by QBICs and the strong tunability of ITO's permittivity using external bias. QBICs consistently exhibit superior performance in modifying the optical response of these hybrid structures. Modulation depth demonstrates a potential upper bound of 148 decibels. We also scrutinize the effect of ITO film carrier density upon near-field trapping and far-field scattering and its consequential effect on the performance of the optical modulation device employing this particular structural arrangement. The development of active high-performance optical devices might find promising applications in our results.

In long-haul transmission over coupled multi-core fibers, we present an adaptive multi-input multi-output (MIMO) filter architecture that operates in the frequency domain with fractional spacing. Input signal sampling rates are below 2 times oversampling, utilizing a non-integer oversampling factor for mode demultiplexing. The frequency-domain sampling rate conversion, targeted at the symbol rate, i.e., one sample, is situated after the fractionally spaced frequency-domain MIMO filter. The filter coefficients' adaptive control is orchestrated by deep unfolding, using stochastic gradient descent and gradient calculations derived from backpropagation through the sampling rate conversion applied to output signals. The proposed filter's efficacy was tested in a 16-channel wavelength-division multiplexed and 4-core space-division multiplexed experiment with 32-Gbaud polarization-division-multiplexed quadrature phase shift keying signals that used coupled 4-core fibers for long-haul transmission. Despite the 6240-kilometer transmission, the fractional oversampling frequency-domain adaptive 88 filter, operating at 9/8 oversampling, incurred a minimal performance penalty compared to the standard 2 oversampling frequency-domain adaptive 88 filter. Computational complexity, as determined by the number of complex-valued multiplications, was diminished by a remarkable 407%.

Endoscopic techniques find broad application within the medical domain. Small-diameter endoscopic instruments are built using either fiber optic bundles or, quite helpfully, graded-index lenses. While fiber bundles can endure mechanical stress during operation, the performance of a GRIN lens is susceptible to deformation. The present work examines the effects of deflection on visual image quality and associated adverse effects related to the developed eye endoscope. A result of our dedicated efforts to construct a reliable model of a bent GRIN lens is also included, achieved through utilization of the OpticStudio software.

We experimentally validate a low-loss radio frequency (RF) photonic signal combiner, presenting a flat frequency response from 1 GHz to 15 GHz, and exhibiting a negligible group delay variation of 9 picoseconds. The distributed group array photodetector combiner (GAPC) is implemented using scalable silicon photonics, enabling its application in radio frequency photonic systems, which require the merging of a substantial number of photonic signals.

Numerical and experimental investigation of chaos generation from a novel, single-loop dispersive optoelectronic oscillator (OEO) incorporating a broadband chirped fiber Bragg grating (CFBG). The reflection from the CFBG is predominantly influenced by its dispersion effect, which, owing to its broader bandwidth compared to the chaotic dynamics, outweighs any filtering effect. Assured feedback strength results in the proposed dispersive OEO exhibiting chaotic behavior. Increased feedback strength correlates with the suppression of the chaotic time-delay signature. An increase in grating dispersion leads to a reduction in TDS levels. Our proposed system, without sacrificing bandwidth performance, expands the chaotic parameter space, strengthens robustness against modulator bias fluctuations, and diminishes TDS by at least five times compared to the classical OEO. Numerical simulations exhibit satisfactory qualitative agreement with the experimental observations. Through experimentation, dispersive OEO is further demonstrated to enable random bit generation at rates tunable up to 160 Gbps.

We introduce a novel external cavity feedback arrangement, using a double-layer laser diode array in conjunction with a volume Bragg grating (VBG). External cavity feedback and diode laser collimation produce a high-power, ultra-narrow linewidth diode laser pumping source, centered at 811292 nanometers, with a spectral linewidth of 0.0052 nanometers and output power exceeding 100 watts. Electro-optical conversion efficiencies for external cavity feedback and collimation surpass 90% and 46%, respectively. Temperature regulation of VBG is carefully managed to precisely tune the central wavelength between 811292nm and 811613nm, encompassing the entire Kr* and Ar* absorption spectra. This is, we believe, the initial documentation of an ultra-narrow linewidth diode laser that has the capacity to pump two metastable rare gases.

A cascaded Fabry-Perot interferometer (FPI) incorporating the harmonic Vernier effect (HEV) is explored and shown to enable an ultrasensitive refractive index (RI) sensor, as detailed in this paper. By sandwiching a hollow-core fiber (HCF) segment between a lead-in single-mode fiber (SMF) pigtail and a reflective SMF segment, a cascaded FPI structure is formed. The 37-meter offset between the fibers' centers positions the HCF as the sensing FPI, and the reflection SMF segment as the reference FPI.