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[Keyword] optical(1497hit)

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  • Effect of Binary Labeling Schemes on PAS with BICM-ID System Performance over the AWGN and Optical Fiber Channels Open Access

    Mamoru KOMATSU  Akira NAKA  

     
    PAPER-Fiber-Optic Transmission for Communications

      Vol:
    E108-B No:1
      Page(s):
    24-34

    Bit-interleaved coded modulation with iterative decoding (BICM-ID) effectively provides a high spectral efficiency and coding gain for digital coherent systems over additive white Gaussian noise (AWGN) and optical fiber channels. We previously proposed combining probabilistic amplitude shaping (PAS) with BICM-ID to further improve the system performance. However, the BICM-ID performance depends on the binary labeling scheme used for the constellation points. In this study, we evaluated the effect of binary labeling schemes on the performance of the PAS with BICM-ID system. Numerical simulations showed that the PAS with BICM-ID system employing a suitable binary labeling scheme offers a significant coding gain over both the AWGN and optical fiber channels. The system is also robust against performance degradation caused by the optical Kerr effect in the optical fiber channel. We used an extrinsic information transfer (EXIT) chart to analyze the suitability of binary labeling schemes and the effect of bit interleavers. The results showed that a binary labeling scheme is suitable if the slope of the demodulator’s EXIT curve is close to the slope of the decoder’s EXIT curve. The EXIT chart analysis also showed that inserting bit interleavers mitigates the performance degradation during iterative decoding. In addition, we used bitwise mutual information to evaluate the SNR penalty due to shaping gap and coding gap, and coding gain offered by iterative decoding of BICM-ID.

  • Disaggregated Architecture of Post-Quantum Security for Optical and Packet Transport Equipment Open Access

    Atsushi TANIGUCHI  Yasuhiro MOCHIDA  Sakae CHIKARA  Yasuyuki SANARI  Keizo MURAKAMI  Momoko MIURA  Hirokazu TAKAHASHI  Koichi TAKASUGI  Hiroki ITOH  Daigoro YOKOZEKI  

     
    INVITED PAPER

      Vol:
    E107-B No:12
      Page(s):
    899-906

    The advent of quantum computers has raised the risk of eavesdropping and made it essential to apply post-quantum security to most communication services. Encryption processing is not a single function as it includes key exchange functions (e.g., PQC and QKD) and encryption protocols (e.g., IPsec, MACsec, and L1 encryption), and it is necessary to combine these functions to suit the requirements of each service. However, the encryption protocols of existing optical & packet transport equipment are vertically integrated and cannot be altered easily. In this paper, we propose a disaggregation architecture of post-quantum security for optical and packet transport equipment. By separating key management functions from their implementation, the architecture enables more secure encrypted communication by using more secure key exchange methods and implemented encryption protocols. In addition, we also propose a key splitting method that eliminates the impact on communication in the event of a failure due to the functional separation provided by the method; it supports various encryption ciphers. By using this method, key update can be continued even after a communication break interrupts key exchange. We show that 96 Gbps traffic can be encrypted without error.

  • Multi-Band Optical Networking: Recent Advances toward IOWN All-Photonics Network Open Access

    Masahiro NAKAGAWA  Haruka MINAMI  Takafumi FUKATANI  Takeshi SEKI  Rie HAYASHI  Takeshi KUWAHARA  

     
    INVITED PAPER

      Vol:
    E107-B No:12
      Page(s):
    842-851

    IoT and AI-related services and applications are becoming more common and it is expected that cyber-physical systems will enrich our daily lives in the near future. In such a situation, a huge amount of data is exchanged throughout the world in a real time fashion, which will increasingly push the need for optical network evolution. Considering these trends, intensive efforts on research and development have recently been dedicated to realize All-Photonics Network (APN) that is a key element of Innovative Optical and Wireless Network (IOWN). For materializing APN vision, one of the fundamental challenges is to expand network capacity in a highly cost- and energy-efficient manner. Meanwhile, many detailed studies have greatly improved the performance of multi-band optical networks. Thanks to such efforts, multi-band networking has been becoming feasible as a promising capacity-scaling solution, which can be a key enabler for APN. This paper reviews the recent advances in the multi-band optical network from various aspects. Specifically, we take a quick look at the studies enabling multi-band transmission in terms of devices design of transceiver and amplifier, quality-of-transmission estimation, and launch power optimization. Then, we focus on progress in optical switch technology, optical node configuration, path provisioning, and network analysis, aiming to deploy multi-band networks nationwide. We also refer to several emerging technologies, which include our efforts related to wavelength-selective band switching technology. This paper gives an opportunity to understand the trends and potential of multi-band optical networking.

  • High-Power Optical Fiber Transmission Technologies for Radio-Over-Fiber Networks Open Access

    Motoharu MATSUURA  

     
    INVITED PAPER

      Vol:
    E107-B No:12
      Page(s):
    832-841

    The development of optical fiber transmission technologies has led to the emergence of various types of optical fibers have been introduced. In addition, the increase in the transmission capacity of optical fiber communications and the emergence of new applications have gained significant attention in high-power transmission technologies. Particularly, for beyond 5G/6G networks that are based on radio-over-fiber, which transmits wireless radio frequency signals along fiber links, power-over-fiber and high-power signal transmissions are important for the availability and simplification of remote antenna units in mobile communications to improve the scalability. This paper introduces various types of optical fibers and describes representative high-power transmission technologies that use specialized optical fibers.

  • Finite Element Beam Propagation Method Based on Coordinate Transformation for Optimal Design of Optical Waveguide Devices Open Access

    Haonan CHEN  Akito IGUCHI  Yasuhide TSUJI  

     
    PAPER

      Pubricized:
    2024/02/05
      Vol:
    E107-C No:11
      Page(s):
    457-464

    In order to calculate photonic devices with slowly varying waveguide structure along propagation direction, we develop finite element beam propagation method (FE-BPM) with coordinate transformation. In this approach, converting a longitudinally varying waveguide into the equivalent straight waveguide, cumbersome processes in FE-BPM, such as mesh updating and field interpolation processes at each propagation step, can be avoided. We employ this simulation technique in shape optimization of photonic devices and show design examples of mode converter. To show the validity of this approach, the calculated results of designed devices are compared with the finite element method (FEM) or the standard FE-BPM.

  • An Adaptively Biased OFDM Based on Hartley Transform for Visible Light Communication Systems Open Access

    Menglong WU  Yongfa XIE  Yongchao SHI  Jianwen ZHANG  Tianao YAO  Wenkai LIU  

     
    LETTER-Communication Theory and Signals

      Pubricized:
    2023/09/20
      Vol:
    E107-A No:6
      Page(s):
    928-931

    Direct-current biased optical orthogonal frequency division multiplexing (DCO-OFDM) converts bipolar OFDM signals into unipolar non-negative signals by introducing a high DC bias, which satisfies the requirement that the signal transmitted by intensity modulated/direct detection (IM/DD) must be positive. However, the high DC bias results in low power efficiency of DCO-OFDM. An adaptively biased optical OFDM was proposed, which could be designed with different biases according to the signal amplitude to improve power efficiency in this letter. The adaptive bias does not need to be taken off deliberately at the receiver, and the interference caused by the adaptive bias will only be placed on the reserved subcarriers, which will not affect the effective information. Moreover, the proposed OFDM uses Hartley transform instead of Fourier transform used in conventional optical OFDM, which makes this OFDM have low computational complexity and high spectral efficiency. The simulation results show that the normalized optical bit energy to noise power ratio (Eb(opt)/N0) required by the proposed OFDM at the bit error rate (BER) of 10-3 is, on average, 7.5 dB and 3.4 dB lower than that of DCO-OFDM and superimposed asymmetrically clipped optical OFDM (ACO-OFDM), respectively.

  • Simulation of Scalar-Mode Optically Pumped Magnetometers to Search Optimal Operating Conditions Open Access

    Yosuke ITO  Tatsuya GOTO  Takuma HORI  

     
    INVITED PAPER

      Pubricized:
    2023/12/04
      Vol:
    E107-C No:6
      Page(s):
    164-170

    In recent years, measuring biomagnetic fields in the Earth’s field by differential measurements of scalar-mode OPMs have been actively attempted. In this study, the sensitivity of the scalar-mode OPMs under the geomagnetic environment in the laboratory was studied by numerical simulation. Although the noise level of the scalar-mode OPM in the laboratory environment was calculated to be 104 pT/$\sqrt{\mathrm{Hz}}$, the noise levels using the first-order and the second-order differential configurations were found to be 529 fT/cm/$\sqrt{\mathrm{Hz}}$ and 17.2 fT/cm2/$\sqrt{\mathrm{Hz}}$, respectively. This result indicated that scalar-mode OPMs can measure very weak magnetic fields such as MEG without high-performance magnetic shield roomns. We also studied the operating conditions by varying repetition frequency and temperature. We found that scalar-mode OPMs have an upper limit of repetition frequency and temperature, and that the repetition frequency should be set below 4 kHz and the temperature should be set below 120°C.

  • Implementing Optical Analog Computing and Electrooptic Hopfield Network by Silicon Photonic Circuits Open Access

    Guangwei CONG  Noritsugu YAMAMOTO  Takashi INOUE  Yuriko MAEGAMI  Morifumi OHNO  Shota KITA  Rai KOU  Shu NAMIKI  Koji YAMADA  

     
    INVITED PAPER

      Pubricized:
    2024/01/05
      Vol:
    E107-A No:5
      Page(s):
    700-708

    Wide deployment of artificial intelligence (AI) is inducing exponentially growing energy consumption. Traditional digital platforms are becoming difficult to fulfill such ever-growing demands on energy efficiency as well as computing latency, which necessitates the development of high efficiency analog hardware platforms for AI. Recently, optical and electrooptic hybrid computing is reactivated as a promising analog hardware alternative because it can accelerate the information processing in an energy-efficient way. Integrated photonic circuits offer such an analog hardware solution for implementing photonic AI and machine learning. For this purpose, we proposed a photonic analog of support vector machine and experimentally demonstrated low-latency and low-energy classification computing, which evidences the latency and energy advantages of optical analog computing over traditional digital computing. We also proposed an electrooptic Hopfield network for classifying and recognizing time-series data. This paper will review our work on implementing classification computing and Hopfield network by leveraging silicon photonic circuits.

  • Analysis of Optical Power Splitter with Resonator Structure Constructed by Two-Dimensional MDM Plasmonic Waveguide Open Access

    Yoshihiro NAKA  Masahiko NISHIMOTO  Mitsuhiro YOKOTA  

     
    BRIEF PAPER-Electromagnetic Theory

      Pubricized:
    2023/12/07
      Vol:
    E107-C No:5
      Page(s):
    141-145

    An efficient optical power splitter constructed by a metal-dielectric-metal plasmonic waveguide with a resonator structure has been analyzed. The method of solution is the finite difference time domain (FD-TD) method with the piecewise linear recursive convolution (PLRC) method. The resonator structure consists of input/output waveguides and a narrow waveguide with a T-junction. The power splitter with the resonator structure is expressed by an equivalent transmission-line circuit. We can find that the transmittance and reflectance calculated by the FD-TD method and the equivalent circuit are matched when the difference in width between the input/output waveguides and the narrow waveguide is small. It is also shown that the transmission wavelength can be adjusted by changing the narrow waveguide lengths that satisfy the impedance matching condition in the equivalent circuit.

  • Optical Mode Multiplexer Using LiNbO3 Asymmetric Directional Coupler Enabling Voltage Control for Phase-Matching Condition Open Access

    Shotaro YASUMORI  Seiya MORIKAWA  Takanori SATO  Tadashi KAWAI  Akira ENOKIHARA  Shinya NAKAJIMA  Kouichi AKAHANE  

     
    BRIEF PAPER-Optoelectronics

      Pubricized:
    2023/11/29
      Vol:
    E107-C No:5
      Page(s):
    146-149

    An optical mode multiplexer was newly designed and fabricated using LiNbO3 waveguides. The multiplexer consists of an asymmetric directional coupler capable of achieving the phase-matching condition by the voltage adjustment. The mode conversion efficiency between TM0 and TM1 modes was quantitatively measured to be 0.86 at maximum.

  • Overfitting Problem of ANN- and VSTF-Based Nonlinear Equalizers Trained on Repeated Random Bit Sequences Open Access

    Kai IKUTA  Jinya NAKAMURA  Moriya NAKAMURA  

     
    PAPER-Fiber-Optic Transmission for Communications

      Vol:
    E107-B No:4
      Page(s):
    349-356

    In this paper, we investigated the overfitting characteristics of nonlinear equalizers based on an artificial neural network (ANN) and the Volterra series transfer function (VSTF), which were designed to compensate for optical nonlinear waveform distortion in optical fiber communication systems. Linear waveform distortion caused by, e.g., chromatic dispersion (CD) is commonly compensated by linear equalizers using digital signal processing (DSP) in digital coherent receivers. However, mitigation of nonlinear waveform distortion is considered to be one of the next important issues. An ANN-based nonlinear equalizer is one possible candidate for solving this problem. However, the risk of overfitting of ANNs is one obstacle in using the technology in practical applications. We evaluated and compared the overfitting of ANN- and conventional VSTF-based nonlinear equalizers used to compensate for optical nonlinear distortion. The equalizers were trained on repeated random bit sequences (RRBSs), while varying the length of the bit sequences. When the number of hidden-layer units of the ANN was as large as 100 or 1000, the overfitting characteristics were comparable to those of the VSTF. However, when the number of hidden-layer units was 10, which is usually enough to compensate for optical nonlinear distortion, the overfitting was weaker than that of the VSTF. Furthermore, we confirmed that even commonly used finite impulse response (FIR) filters showed overfitting to the RRBS when the length of the RRBS was equal to or shorter than the length of the tapped delay line of the filters. Conversely, when the RRBS used for the training was sufficiently longer than the tapped delay line, the overfitting could be suppressed, even when using an ANN-based nonlinear equalizer with 10 hidden-layer units.

  • Recent Progress in Optical Network Design and Control towards Human-Centered Smart Society Open Access

    Takashi MIYAMURA  Akira MISAWA  

     
    INVITED PAPER

      Pubricized:
    2023/09/19
      Vol:
    E107-B No:1
      Page(s):
    2-15

    In this paper, we investigate the evolution of an optical network architecture and discuss the future direction of research on optical network design and control. We review existing research on optical network design and control and present some open challenges. One of the important open challenges lies in multilayer resource optimization including IT and optical network resources. We propose an adaptive joint optimization method of IT resources and optical spectrum under time-varying traffic demand in optical networks while avoiding an increase in operation cost. We formulate the problem as mixed integer linear programming and then quantitatively evaluate the trade-off relationship between the optimality of reconfiguration and operation cost. We demonstrate that we can achieve sufficient network performance through the adaptive joint optimization while suppressing an increase in operation cost.

  • Bandwidth Abundant Optical Networking Enabled by Spatially-Jointed and Multi-Band Flexible Waveband Routing Open Access

    Hiroshi HASEGAWA  

     
    INVITED PAPER

      Pubricized:
    2023/09/19
      Vol:
    E107-B No:1
      Page(s):
    16-26

    The novel optical path routing architecture named flexible waveband routing networks is reviewed in this paper. The nodes adopt a two-stage path routing scheme where wavelength selective switches (WSSs) bundle optical paths and form a small number of path groups and then optical switches without wavelength selectivity route these groups to desired outputs. Substantial hardware scale reduction can be achieved as the scheme enables us to use small scale WSSs, and even more, share a WSS by multiple input cores/fibers through the use of spatially-joint-switching. Furthermore, path groups distributed over multiple bands can be switched by these optical switches and thus the adaptation to multi-band transmission is straightforward. Network-wide numerical simulations and transmission experiments that assume multi-band transmission demonstrate the validity of flexible waveband routing.

  • Crosstalk-Aware Resource Allocation Based on Optical Path Adjacency and Crosstalk Budget for Space Division Multiplexing Elastic Optical Networks

    Kosuke KUBOTA  Yosuke TANIGAWA  Yusuke HIROTA  Hideki TODE  

     
    PAPER

      Pubricized:
    2023/09/12
      Vol:
    E107-B No:1
      Page(s):
    27-38

    To cope with the drastic increase in traffic, space division multiplexing elastic optical networks (SDM-EONs) have been investigated. In multicore fiber environments that realize SDM-EONs, crosstalk (XT) occurs between optical paths transmitted in the same frequency slots of adjacent cores, and the quality of the optical paths is degraded by the mutual influence of XT. To solve this problem, we propose a core and spectrum assignment method that introduces the concept of prohibited frequency slots to protect the degraded optical paths. First-fit-based spectrum resource allocation algorithms, including our previous study, have the problem that only some frequency slots are used at low loads, and XT occurs even though sufficient frequency slots are available. In this study, we propose a core and spectrum assignment method that introduces the concepts of “adjacency criterion” and “XT budget” to suppress XT at low and middle loads without worsening the path blocking rate at high loads. We demonstrate the effectiveness of the proposed method in terms of the path blocking rate using computer simulations.

  • Antennas Measurement for Millimeter Wave 5G Wireless Applications Using Radio Over Fiber Technologies Open Access

    Satoru KUROKAWA  Michitaka AMEYA  Yui OTAGAKI  Hiroshi MURATA  Masatoshi ONIZAWA  Masahiro SATO  Masanobu HIROSE  

     
    INVITED PAPER

      Pubricized:
    2023/09/19
      Vol:
    E106-B No:12
      Page(s):
    1313-1321

    We have developed an all-optical fiber link antenna measurement system for a millimeter wave 5th generation mobile communication frequency band around 28 GHz. Our developed system consists of an optical fiber link an electrical signal transmission system, an antenna-coupled-electrode electric-field (EO) sensor system for 28GHz-band as an electrical signal receiving system, and a 6-axis vertically articulated robot with an arm length of 1m. Our developed optical fiber link electrical signal transmission system can transmit the electrical signal of more than 40GHz with more than -30dBm output level. Our developed EO sensor can receive the electrical signal from 27GHz to 30GHz. In addition, we have estimated a far field antenna factor of the EO sensor system for the 28GHz-band using an amplitude center modified antenna factor estimation equation. The estimated far field antenna factor of the sensor system is 83.2dB/m at 28GHz.

  • Ferrule Endface Dimension Optimization for Standard Outer Diameter 4-Core Fiber Connector

    Kiyoshi KAMIMURA  Yuki FUJIMAKI  Kentaro MATSUDA  Ryo NAGASE  

     
    PAPER

      Pubricized:
    2023/10/02
      Vol:
    E106-C No:12
      Page(s):
    781-788

    Physical contact (PC) optical connectors realize long-term stability by maintaining contact with the optical fiber even during temperature fluctuations caused by the microscopic displacement of the ferrule endface. With multicore fiber (MCF) connectors, stable PC connection conditions need to be newly investigated because MCFs have cores other than at the center. In this work, we investigated the microscopic displacement of connected ferrule endfaces using the finite element method (FEM). As a result, by using MCF connectors with an apex offset, we found that the allowable fiber undercut where all the cores make contact is slightly smaller than that of single-mode fiber (SMF) connectors. Therefore, we propose a new equation for determining the allowable fiber undercut of MCF connectors. We also fabricated MCF connectors with an allowable fiber undercut and confirmed their reliability using the composite temperature/humidity cyclic test.

  • Evaluating Energy Consumption of Internet Services Open Access

    Leif Katsuo OXENLØWE  Quentin SAUDAN  Jasper RIEBESEHL  Mujtaba ZAHIDY  Smaranika SWAIN  

     
    INVITED PAPER

      Pubricized:
    2023/06/15
      Vol:
    E106-B No:11
      Page(s):
    1036-1043

    This paper summarizes recent reports on the internet's energy consumption and the internet's benefits on climate actions. It discusses energy-efficiency and the need for a common standard for evaluating the climate impact of future communication technologies and suggests a model that can be adapted to different internet applications such as streaming, online reading and downloading. The two main approaches today are based on how much data is transmitted or how much time the data is under way. The paper concludes that there is a need for a standardized method to estimate energy consumption and CO2 emission related to internet services. This standard should include a method for energy-optimizing future networks, where every Wh will be scrutinized.

  • Optical Fiber Connector Technology Open Access

    Ryo NAGASE  

     
    INVITED PAPER

      Pubricized:
    2023/05/11
      Vol:
    E106-B No:11
      Page(s):
    1044-1049

    Various optical fiber connectors have been developed during the 40 years since optical fiber communications systems were first put into practical use. This paper describes the key technologies for optical connectors and recent technical issues.

  • Real-Time Detection of Fiber Bending and/or Optical Filter Shift by Machine-Learning of Tapped Raw Digital Coherent Optical Signals

    Yuichiro NISHIKAWA  Shota NISHIJIMA  Akira HIRANO  

     
    PAPER

      Pubricized:
    2023/05/19
      Vol:
    E106-B No:11
      Page(s):
    1065-1073

    We have proposed autonomous network diagnosis platform for operation of future large capacity and virtualized network, including 5G and beyond 5G services. As for the one candidate of information collection and analyzing function blocks in the platform, we proposed novel optical sensing techniques that utilized tapped raw signal data acquired from digital coherent optical receivers. The raw signal data is captured before various digital signal processing for demodulation. Therefore, it contains various waveform deformation and/or noise as it experiences through transmission fibers. In this paper, we examined to detect two possible failures in transmission lines including fiber bending and optical filter shift by analyzing the above-mentioned raw signal data with the help of machine learning. For the purpose, we have implemented Docker container applications in WhiteBox Cassini to acquire real-time raw signal data. We generated CNN model for the detections in off-line processing and used them for real-time detections. We have confirmed successful detection of optical fiber bend and/or optical filter shift in real-time with high accuracy. Also, we evaluated their tolerance against ASE noise and invented novel approach to improve detection accuracy. In addition to that, we succeeded to detect them even in the situation of simultaneous occurrence of those failures.

  • All-Optical Modulation Format Conversions from PAM4 to QPSK and 16QAM Using Silicon-Rich Nitride Waveguides Open Access

    Yuto FUJIHARA  Asahi SUEYOSHI  Alisson RODRIGUES DE PAULA  Akihiro MARUTA  Ken MISHINA  

     
    PAPER

      Pubricized:
    2023/05/11
      Vol:
    E106-B No:11
      Page(s):
    1074-1083

    Quadrature phase-shift keying (QPSK) and 16-quadrature amplitude modulation (16QAM) formats are deployed in inter-data center networks where high transmission capacity and spectral efficiency are required. However, in intra-data center networks, a four-level pulse amplitude modulation (PAM4) format is deployed to satisfy the requirements for a simple and low-cost transceiver configuration. For the seamless and effective connection of such heterogeneous networks without an optical-electrical-optical conversion, an all-optical modulation format conversion technique is required. In this paper, we propose all-optical PAM4 to QPSK and 16QAM modulation format conversions using silicon-rich nitride waveguides. The successful conversions from 50-Gbps-class PAM4 signals to 50-Gbps-class QPSK and 100-Gbps-class 16QAM signals are demonstrated via numerical simulations.

1-20hit(1497hit)

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