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- 2018
- silicon photonics
- inhouse design
- coherent optical transmission network
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low-coherent optical diffraction tomography by angle-scanning illumination
摘要： Temporally low-coherent optical diffraction tomography (ODT) is proposed and demonstrated based on angle-scanning Mach–Zehnder interferometry. Using a digital micromirror device based on diffractive tilting, the full-field interference of incoherent light is successfully maintained during every angle scanning sequences. Further, current ODT reconstruction principles for temporally incoherent illuminations are thoroughly reviewed and developed. Several limitations of incoherent illumination are also discussed, such as the nondispersive assumption, optical sectioning capacity, and illumination angle limitation. Using the proposed setup and reconstruction algorithms, low-coherent ODT imaging of plastic microspheres, human red blood cells, and rat pheochromocytoma cells is experimentally demonstrated.
关键词： quantitative phase imaging,low-coherent,optical diffraction tomography,coherent noise
更新于2025-09-23 15:23:52
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Approaching Terabits per Carrier Metro-Regional Transmission Using Beyond-100GBd Coherent Optics with Propabilistically Shaped DP-64QAM Modulation
摘要： This research work proposed and experimentally demonstrated beyond-100GBd probabilistically-shaped coherent optics that support transmission of ~1.2 Tbps coded line rate and ~0.9 Tbps net bit rate per optical carrier over metro-regional distances. Pursuing next-generation transmission systems having both high capacity approaching Terabits per wavelength and high spectral efficiency requires engineering efforts from different aspects, which may includes the enhancement of analog-to-digital or digital-to-analog (AD/DA) interfaces, the improvement of channel characteristics, and also the realization of better receiver sensitivities, preferably through DSP techniques such as probabilistic shaping (PS). By doing so, this work achieved single-channel and 112.5GHz-WDM transmission of 900G wavelengths over 800 km and 400 km, respectively, which employed PS DP-64QAM modulation format at 105 GBd, yielding a net spectral efficiency of 8.05 bits/s/Hz. Such a high symbol rate was demonstrated using a commercially available DAC unit without band-interleaving. The enhanced optical channel consists of ITU-T G.654 compliant Terawave SLA+ fiber spans with backward-pumped Raman amplifiers. In addition, with the same PS DP-64QAM modulation format and the same enhanced channel, this research work also demonstrated that 400G wavelengths can be delivered over 2,800 km supporting long-haul applications.
关键词： quadrature amplitude modulation,probabilistic shaping,optical fibers,Coherent optical communications
更新于2025-09-23 15:23:52
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[Communications in Computer and Information Science] Futuristic Trends in Network and Communication Technologies Volume 958 (First International Conference, FTNCT 2018, Solan, India, February 9–10, 2018, Revised Selected Papers) || Future Perspectives in Elastic Optical Networks
摘要： The new generation Elastic Optical Networks (EONs) based on Orthogonal Frequency Division Multiplexing (OFDM) can accommodate exponentially increasing heterogeneous data traffic efficiently and economically. In EONs, the optimum channel spacing between various subcarriers is very crucial for its efficient performance. The use of Sub-Carrier Multiplexing (SCM) in EONs is visualized as an evolving field. This paper present the evaluation of SCM based EONs for both mathematical and simulative model. The designed SCM-EON network is analytically evaluated for its performance with different modulation techniques (Direct Modulation and External Modulation). The performance of system is also evaluated for amplification using Semiconductor Optical Amplifier (SOA) and Erbium Doped Fiber Amplifier (EDFA). Simulative results show that Optical Phase Modulation (OPM) along with EDFA offers enhanced performance for the proposed model. It has also been observed that OPM is a better technique for SCM and hence it can be deduced that the combination will boost EONs efficiency in handling network resources.
关键词： SCM,Elastic Optical Networks,OFDM,EDFA,OPM,Bandwidth variable-wavelength cross-connects (BV-WXC),Quadrature Amplitude Modulation (QAM),Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM),Mach-Zehnder modulator (MZM)
更新于2025-09-23 15:23:52
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A structure-simplified and cost-effective coherent receiver for high splitting downstream transmission in next-generation PONs
摘要： In this paper we demonstrate a structure-simplified and cost-effective coherent receiver scheme for high splitting downstream transmission in next generation passive optical networks (NG-PONs). In such scheme, the simple 3dB coupler is used to replace 90° optical hybrid and the electrical local oscillator (LO) is utilized to down-convert signal, and there by only one balanced photodiode (BPD) is required for each polarization. Hence the cost is reduced effectively for the high splitting PON downstream transmission scenario. The comprehensive numerical simulation results show that the receiver sensitivity for both 14G Baud PM-QPSK and PM-16QAM system is comparable to that of the conventional coherent receiver using 90° hybrid. Furthermore, the effect of fiber nonlinearity on maximum power budget performance is investigated. In addition, the high receiver sensitivity of the scheme is also experimentally validated for PM-QPSK and PM-16QAM system under the scenario of 14G Baud BtB, 20km and 40km standard single-mode fiber (SSMF) transmission. The coexistent advantages of low-cost and high receiver sensitivity make the proposed scheme an attractive candidate for NG-PONs.
关键词： Downstream transmission,NG-PONs,Coherent receiver,Quadrature amplitude modulation
更新于2025-09-23 15:23:52
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Field-squeeze operators via coherent population trapping
摘要： We present a scheme to generate unitarily two-mode and four-mode ?eld squeezing in optical cavities with the near-resonantly dressed three-level atoms in the (cid:2) con?guration. The dressing ?elds open two coherent population trapping (CPT) windows, within which the atoms stay predominantly in the dark state and yield strong nonlinearities for both the dressing ?elds themselves and the other applied ?elds. The two-mode squeeze operator is separated from degrees of freedom of atoms in a common CPT window, and the multimode squeeze operator is segregated in different CPT windows. The resulting two-mode and multimode interaction strengths are at least one order higher than in the previous dispersive schemes, where all ?elds are far off resonant with the atoms. The present near-resonant scheme is robust to spontaneous emission since atoms are nearly trapped in a long-lived superposition state.
关键词： field squeezing,coherent population trapping,optical cavities,quantum optics,three-level atoms
更新于2025-09-23 15:23:52
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Squeezing-induced giant Goos-H?nchen shift and hypersensitized displacement sensor in a two-level atomic system
摘要： We analyze an efficient scheme to enhance the Goos-H?nchen (GH) shifts of the reflected and transmitted beams in a cavity containing two-level atomic medium. A broadband squeezed vacuum field is injected into the cavity to interact with the atomic medium. In the bad cavity limit, the Bloch equations for the atomic operators are identical to those in the free space, but with the modification of the system parameters. Using experimentally achievable parameters, we identify the conditions under which the squeezed vacuum allows us to enhance the GH shifts of the reflected and transmitted beams beyond what is achievable in the absence of the squeezed vacuum. The enhanced GH shifts originate from the coherent population oscillations controlled by the squeezed vacuum field. Furthermore, we also find that the GH shifts of the reflected and transmitted beams depend sensitively on the relative phase between the control field and the squeezed vacuum field. Subsequently, we propose a scheme for such a configuration of the GH shift as a family of hypersensitized displacement sensors. Based on the numerical analysis, the detection sensitivity and minimum detectable value for the tiny displacement can reach approximately 2340 μm/nm and 14.4 pm, respectively.
关键词： coherent population oscillations,Goos-H?nchen shift,two-level atomic system,displacement sensor,squeezed vacuum
更新于2025-09-23 15:23:52
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Coherent detection of ultraweak electromagnetic fields
摘要： We explore the application of heterodyne interferometry for a weak-field coherent detection scheme. The methods detailed here will be used in ALPS II, an experiment designed to search for weakly interacting, sub-eV particles. For ALPS II to reach its design sensitivity this detection system must be capable of accurately measuring fields with equivalent amplitudes on the order of 10?5 photons=s or greater. We present initial results of an equivalent dark count rate on the order of 10?5 photons=s as well as successful generation and detection of a signal with a field strength equivalent to 10?2 photons=s.
关键词： axionlike particles,heterodyne interferometry,ALPS II,weak-field detection,coherent detection
更新于2025-09-23 15:23:52
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Optical and Digital Key Enabling Techniques for SDM-Based Optical Networks
摘要： In order to support, in a cost-effective way, the data capacity demand in the context of future 5G networks, a new set of advanced technologies need to be explored, as it is the case of space-division multiplexing (SDM) along with energy efficient coherent detection based modulation formats. This paper presents the recent results on enabled optical networks based on SDM for high capacity optical networks compatible with 5G network infrastructure and data center connectivity. In particular, we demonstrate the viability of using Long-Period Gratings (LPGs) in multi-core fibers (MCFs) to develop different components for multicore-based SDM systems, such as pump couplers and core/wavelength selective multi-core switches and couplers. Moreover, we also present and characterize the performance of different digital signal processing (DSP) algorithms and subsystems supporting optical coherent detection in SDM systems.
关键词： Coherent detection,long period grating,generalized Stokes space,digital signal processing,space-division multiplexing,space-division demultiplexing
更新于2025-09-23 15:23:52
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High-spectral-efficiency 600-Gbps/carrier Transmission Using PDM-256QAM Format
摘要： High-capacity carrier signals with high-order modulation are being considered for data center interconnection (DCI) applications as they can reduce the cost per bit by decreasing the number of devices and increasing fiber capacity. However, signal quality degradation due to device imperfections affecting the frequency response has limited the capacity per carrier of PDM-256QAM signals to under 400 Gbps. Here, it is possible to use a calibration method for dealing with device imperfections wherein a fixed equalizer separately calibrates the frequency response of the transmitter and receiver. Our previous study showed that PDM-256QAM signals at up to 48 GBaud could be transmitted over 100 km, while it used an experimental setup with total 3-dB analog bandwidth of 13 GHz and 20 GHz for transmitter and receiver, respectively. A micro-integrable tunable laser assembly (μITLA) with a typical linewidth of 20 kHz, maximum under 100 kHz. Actual data center interconnection (DCI) applications, however, are expected to use dense wavelength division multiplexing (WDM), so in this study, we examined transmission of 10-WDM 48-GBaud PDM-256QAM signals in a 50-GHz grid and evaluated the WDM penalties. The resulting spectral efficiency (SE) of 600-Gbps/carrier WDM transmissions was as high as 12.02 bit/s/Hz.
关键词： optical,digital coherent,fiber,optical transmission,signal processing,digital communication,high-order quadrature amplitude modulation
更新于2025-09-23 15:23:52
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Effect of anisotropic non-Kolmogorov turbulence on the evolution behavior of Gaussian Schell-model vortex beams
摘要： The effect of anisotropic non-Kolmogorov turbulence on the evolution behavior of average intensity and coherent vortices for Gaussian Schell-model (GSM) vortex beams is investigated. Based on the extended Huygens–Fresnel principle and power spectrum of the anisotropic non-Kolmogorov turbulence, the analytical expressions for the cross-spectral density and average intensity of GSM vortex beams propagating through anisotropic non-Kolmogorov turbulence are obtained. The evolution behavior of intensity and coherent vortices for GSM vortex beams in anisotropic non-Kolmogorov turbulence has been discussed in detail by numerical simulation. The results shown that the evolution behavior of coherent vortices and intensity profile depends on the effective anisotropic factor, generalized exponent factor and structure constant of anisotropic non-Kolmogorov turbulence, as well as the beam parameters, such as beam waist, wave length and correlation length.
关键词： Gaussian Schell-model vortex beams,Anisotropic non-Kolmogorov turbulence,Evolution behavior of coherent vortices
更新于2025-09-23 15:23:52