By strategically modifying the preparation procedures and structural configuration, the tested component achieved a coupling efficiency of 67.52% and an insertion loss of 0.52 dB. This tellurite-fiber-based side-pump coupler, as far as we know, is a first in its class. The presented fused coupler promises to simplify the complex architectures of mid-infrared fiber lasers or amplifiers.

This paper details a joint signal processing solution for high-speed, long-reach underwater wireless optical communication (UWOC) systems. The solution combines a subband multiple-mode full permutation carrierless amplitude phase modulation (SMMP-CAP), signal-to-noise ratio weighted detection (SNR-WD), and multi-channel decision feedback equalization (MC-DFE) to alleviate bandwidth limitations. The SMMP-CAP scheme's approach to trellis coded modulation (TCM) subset division is to partition the 16 quadrature amplitude modulation (QAM) mapping set into four 4-QAM mapping subsets. The system's demodulation efficiency within a fading channel is enhanced by the incorporation of an SNR-WD and an MC-DFE. The minimal optical powers necessary for data rates of 480 Mbps, 600 Mbps, and 720 Mbps, at a 38010-3 hard-decision forward error correction (HD-FEC) threshold, as determined by a laboratory experiment, were -327 dBm, -313 dBm, and -255 dBm, respectively. Moreover, the system effectively achieved a data transmission rate of 560 Mbps in a swimming pool with a transmission length extending up to 90 meters, accompanied by a total attenuation value of 5464dB. Based on our present knowledge, this is the first occasion where a high-speed, long-distance UWOC system has been presented, leveraging an 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. The SI signal is entirely canceled when a local reference signal of equivalent amplitude and opposing phase is superimposed. Voruciclib Nonetheless, the manual approach to manipulating the reference signal often impedes the realization of both high-speed and high-precision cancellation. To mitigate this issue, an adaptive real-time optical signal interference cancellation (RTA-OSIC) scheme, employing a SARSA reinforcement learning (RL) algorithm, is both proposed and experimentally verified. The RTA-OSIC scheme, leveraging an adaptive feedback signal generated from evaluating the received SOI quality, can autonomously regulate the amplitude and phase of a reference signal using a variable optical attenuator (VOA) and a variable optical delay line (VODL). An experiment involving a 5GHz 16QAM OFDM IBFD transmission is conducted to validate the proposed system's feasibility. 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. ethylene biosynthesis The proposed RTA-OSIC scheme is evaluated for its short-term and long-term stability characteristics. 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.

The performance of modern electromagnetic and photonics systems is significantly impacted by active devices. Active devices often leverage the epsilon-near-zero (ENZ) phenomenon in combination with low Q-factor resonant metasurfaces, thereby considerably amplifying light-matter interaction at the nanoscale. Nonetheless, the low Q-factor resonance might restrict the optical modulation process. The exploration of optical modulation mechanisms within low-loss and high-Q-factor metasurfaces has been underrepresented. 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. exercise is medicine A metasurface, structured with five square apertures within a unit cell, exhibits multiple BICs, functionalities orchestrated by the strategic placement of the central aperture. We also ascertain the characteristics of these QBICs by undertaking multipole decomposition and evaluating the near-field distribution. The resonant peak position and intensity of the transmission spectrum are actively controlled by integrating ENZ ITO thin films with QBICs supported by silicon metasurfaces. This control is enabled by the significant tunability of ITO's permittivity under external bias and the high-Q factor facilitated by QBICs. QBICs consistently exhibit superior performance in modifying the optical response of these hybrid structures. The maximum modulation depth reaches a value of 148 dB. Furthermore, we explore the relationship between the carrier density of the ITO film and the near-field trapping and far-field scattering effects, which ultimately influence the efficacy of optical modulation within this framework. Applications of our findings may be promising for the development of high-performance, active optical devices.

A fractionally spaced frequency-domain adaptive multi-input multi-output (MIMO) filter architecture, designed for mode demultiplexing in long-haul transmission over coupled multi-core fibers, employs an input signal sampling rate below 2-fold oversampling with a non-integral oversampling factor. Following the fractionally spaced frequency-domain MIMO filter, the frequency-domain sampling rate conversion is applied, specifically for symbol rate conversion, i.e., a single sampling. Stochastic gradient descent, coupled with backpropagation through the sampling rate conversion of output signals, adaptively adjusts filter coefficients based on deep unfolding. Using a long-haul transmission experiment, we assessed the performance of the suggested filter, employing 16 wavelength-division multiplexed channels and 4-core space-division multiplexed 32-Gbaud polarization-division-multiplexed quadrature phase shift keying signals transmitted over coupled 4-core fibers. The 6240-km transmission had minimal impact on the performance of the fractional 9/8 oversampling frequency-domain adaptive 88 filter, remaining comparable to the 2 oversampling frequency-domain adaptive 88 filter. A substantial 407% decrease was observed in the computational complexity, specifically the count of complex-valued multiplications needed.

In medicine, endoscopic techniques are widely applied. The construction of small-diameter endoscopes can be accomplished in two ways: by using fiber bundles, or, favorably, by utilizing graded-index lenses. While fiber bundles maintain their structural integrity under mechanical stress during use, the GRIN lens's performance can be affected by its displacement. We investigate how deflection impacts image quality and related undesirable side effects in the custom-built eye endoscope we developed. Presented here is the outcome of our initiative to formulate a dependable model of a bent GRIN lens, all within the framework of the OpticStudio software.

Through experimentation, we have established a low-loss, radio frequency (RF) photonic signal combiner with a consistent response from 1 GHz to 15 GHz, and a small group delay variation, specifically 9 picoseconds. Scalable silicon photonics provides the platform for the implementation of the distributed group array photodetector combiner (GAPC), which finds application in combining large numbers of photonic signals within RF photonic systems.

An optoelectronic oscillator (OEO), characterized by a novel single-loop dispersive design and a broadband chirped fiber Bragg grating (CFBG), is numerically and experimentally studied for chaos generation. The CFBG's bandwidth significantly surpasses that of chaotic dynamics, causing its dispersion effect to be more influential than its filtering effect on reflection. Chaotic behavior is observed in the proposed dispersive OEO, provided a strong enough feedback mechanism is in place. The feedback strength's augmentation demonstrably leads to the suppression of the chaotic time-delay signature's expression. The presence of more grating dispersion results in a reduction of detectable TDS. The proposed system, without impacting bandwidth performance, extends the scope of chaotic parameters, increases resistance to modulator bias variations, and attains a TDS suppression at least five times greater than the traditional OEO system. Experimental results show a pleasing qualitative match with the numerical simulations. Through experimentation, dispersive OEO is further demonstrated to enable random bit generation at rates tunable up to 160 Gbps.

We describe a novel external cavity feedback mechanism, employing a double-layer laser diode array and a volume Bragg grating (VBG). Diode laser collimation, coupled with external cavity feedback, produces a high-power, ultra-narrow linewidth diode laser pumping source with a central wavelength of 811292 nanometers, a spectral linewidth of 0.0052 nanometers, and an output exceeding 100 watts. Electro-optical conversion efficiencies exceed 90% and 46% for external cavity feedback and collimation, respectively. To modulate the VBG temperature and thereby tune the central wavelength from 811292nm to 811613nm, ensuring complete coverage of the Kr* and Ar* absorption spectra. The first reported instance of an ultra-narrow linewidth diode laser capable of pumping two metastable rare gases is described in this paper.

The harmonic Vernier effect (HEV), combined with a cascaded Fabry-Perot interferometer (FPI), forms the basis of an ultrasensitive refractive index (RI) sensor, as presented and demonstrated 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.