Dynamically tunable metasurfaces employing chalcogenide phase-change materials (PCMs) such as Ge2Sb2Te5 alloys have garnered significant attention and research efforts. However, the utilization of chalcogenide PCMs in dynamic metasurface devices necessitates protection, owing to their susceptibility to volatilization and oxidation. Conventional protective layer materials such as Al2O3, TiO2, and SiO2 present potential drawbacks including diffusion, oxidation, or thermal expansion coefficient mismatch with chalcogenide PCMs during high-temperature phase transition, severely limiting the durability of chalcogenide PCM-based devices. In this paper, we propose, for the first time to our knowledge, the utilization of chalcogenide glass characterized by high thermal stability as a protective material for chalcogenide PCM. This approach addresses the durability challenge of current dynamic photonic devices based on chalcogenide PCM by virtue of their closely matched optical and thermal properties. Building upon this innovation, we introduce an all-chalcogenide dynamic tunable metasurface filter and comprehensively simulate and analyze its characteristics. This pioneering work paves the way for the design and practical implementation of optically dynamically tunable metasurface devices leveraging chalcogenide PCMs, ushering in new opportunities in the field.
To meet the ever-increasing demand for data traffic, the simplified coherent optical communications, which exhibit the advantages of low cost, low power consumption and high capacity, have garnered the widespread attention for short-reach optical communications applications. To further reduce the cost of coherent optical transmissions, we for the first time propose and demonstrate the capability of non-integer-oversampling clock data recovery (CDR) to process the noise-shaped signals which is robust to the quantization noise when using cheap digital-to-analog converters (DACs). The 192-Gbps dual-polarization quadrature amplitude modulation- 16 (DP-QAM-16) transmissions are experimentally realized by jointly implementing the noise shaping (NS) technique and 4/3 samples per symbol (sps) CDR processing. Experimental results indicate that 1.2- and 1-dB Q factor gains have been achieved by using the proposed simplified coherent optical transmission structure, under the constraints of 3- and 4-bit quantization respectively. We believe that the joint implementation of NS and non-integer-oversampling CDR is promising for simplifying the coherent optical transmissions for low-cost optical communications applications.
Fiber Bragg grating (FBG) sensor has been one of the main research objects in the field of optical sensing due to its advantages of compact size and capability of multiplexing and long-distance measurement. Since its central wavelength shift has a linear relationship with the measurand change, the typical demodulation method is to fit such relationship linearly or nonlinearly, and demodulate the measured parameter based on the change of Bragg wavelength. In this paper, particularly for an FBG temperature sensor, an effective sensing signal measurement method employing deep convolutional neural networks (DCNN) is proposed. This method can extract temperature automatically with a comparable and even more accurate precision. After training process of DCNN, the temperature information can be directly extracted from the experimentally obtained FBG spectra instead of tracking the peak. Since it makes full use of the spectral information rather than only the central wavelength, it overcomes the limit of traditional fitting method and can improve the measurement accuracy of FBG effectively, with an accuracy of 99.38% and mean error of 0.608. The proposed approach to demodulate the FBG sensors is experimentally verified by checking various spectra obtained at different temperatures, and superior accuracy could be achieved. It provides a cost-effective solution for multiplexing of FBG sensors, and is promising for establishing sensing networks to implement smart monitoring.
FBG in polymer optical fibers (POFs) is a promising technology for a wide range of sensing applications due to a lower Young’s modulus and a large range of applying strain. Furthermore, POFs have several properties which make them attractive for biosensing applications such as nonbrittle nature, flexibility in bending and biocompatibility. Chirped Fiber Bragg gratings (CFBGs), which are characterized by a nonuniform modulation of the refractive index show a broad reflection spectrum, enabling shortlength distributed sensing. The combining benefits of POF and CFBGs is attractive for biomedical applications. Here, we present a novel method to obtain CFBG in POF with a postprocess uniform POF FBG by using resin.
We experimentally demonstrate a fast, simple, and accurate method based on the electrical spectral interferometry for measuring the differential mode group delay (DMGD) and chromatic dispersion (CD) between the higher order modes and the fundamental mode in a 5-km few-mode fiber (FMF). The interferogram information of multiple modes of the measured FMF is recorded and used to deduce the relative delay by applying the FFT processing with a simple mathematical algorithm. Based on the acquired relative delay of different fiber modes, the DMGD and CD can be obtained about (2.27 to 2.36) ps/m, (1.4 to 2.3) ps/nm.km for LP11 mode and (4.56 to 4.68) ps/m, (−1.1 to 1) ps/nm.km for LP21 mode, respectively, for this tested FMF. At the same time, a precision of ±0.0015 ps/m for DMGD measurement has been achieved. The experimental results show that the demonstrated method could be a good solution to the characterization of FMF used in large capacity SDM transmission systems.
The performance of the dual-parallel polarization modulator based optical single-sideband modulator (PSSBM) or frequency shifter (FS) has been studied theoretically. There are various factors impacting the performance of PSSBM/FS, such as the state of polarization (SOP), imbalanced power ratio, and direct current (dc) bias control, and they all have been validated through the VPI software. Based on our simulation results, the desired high-quality SSB frequency shift can be achieved through the PSSBM/FS by applying the optimized parameters while only one dc bias control is required. The results show that PSSBM/FS has the advantages and potentiality to be a commercial product used in various scenarios.
The property of a three-branch waveguide interferometer (TBWI) used to achieve the desired single-side-band (SSB) frequency shift has been theoretically analyzed in detail. Optical frequency comb generation (OFCG) based on TBWI with a recirculating loop has been also proposed and analyzed. The simulation has been implemented to show the properties of TSSBM and TSSBM-based OFCG (TOFCG). Simulation results show that the TOFCG has the ability to generate high-quality multiple optical frequency combs by applying optimized parameters.
We propose and demonstrate a simple multiwavelength erbium-doped fiber laser (EDFL) scheme based on a WaveShaper. The WaveShaper can not only act as a multichannel filter but can also introduce wavelength-dependent loss (WDL) in the laser cavity. The WDL can effectively suppress the mode competition caused by the homogeneous gain broadening of the EDF. As a result, up to an 11-wavelength lasing operation with a wavelength spacing of 0.8 nm has been achieved. The power distribution among wavelengths is uniform and the measured power fluctuation of each wavelength is less than 1 dB.
An incoherent microwave photonic filter (MPF), based on multiwavelength phase modulation (PM) and a WaveShaper, is proposed and investigated. The multiwavelength erbium-doped fiber laser provides multiple taps, while the WaveShaper and a dispersive device perform PM to amplitude modulation (AM) conversion. The WaveShaper can also induce both spectral shaping effect for the taps and a different phase for radio-frequency signal during the PM-to-AM conversion. Principle analysis of MPF based on PM-to-AM conversion is discussed. Simulation is carried out to investigate the influence of WaveShaper parameters on the frequency response of the MPF. Through adjustment of the WaveShaper, MPFs with positive, negative, or complex coefficients are also obtained in the experiment. Experimental observations agree well with the simulation results and discussions are given.
We demonstrate dispersion monitoring of differential phase-shift keying (DPSK) modulated optical transmission system
by measuring RF components of detected optical signal. The results show that this scheme can realize dispersion
monitoring up to 4320ps/nm and sensitivity up to 15.5(ps/nm)/dBm. The effect of OSNR on the performance of the
monitoring system are studied and discussed.
Transmission of eight channel 100Gbit/s CS-RZ DQPSK signals up to 1500km SSMF was demonstrated. This
transmission system only used EDFA and did not adopt coherent detection and polarization multiplexing. The span
spacing in this system varies from 80km to 100km to simulate the practical optical network.
Keywords: Transmission system, modulation format
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