Fiber Optic Communication

Topic Information

Dear colleagues,

Over the last five decades fiber optic communication has been the most important means of human communication. In the coming decades it will continue to play a core role in communication networks. In the future optical fiber communication will have greater bandwidth, higher speed, intelligence, device integration, and photoelectric cooperation to provide large bandwidths and low delay networks for new technologies, such as AR/VR, 5G, 6G, etc. Fiber optic communication is a set of major components, including:

• Fiber optic systems, fiber optic subsystems, and their new applications in quantum electronic devices, including system demonstrations, signal processing, performance characterization, etc.;
• Architecture and design of fiber-based optical networks;
• Architecture and design of free space and hybrid optical networks;
• Smart sensors, such as intelligent optical fiber sensors, spectrum sensors, photoelectric sensors, etc.;
• Active components, such as semiconductor lasers and amplifiers, fiber optic amplifiers, photodetectors, and optical switches;
• Passive optical components, such as silicon and InP, and silica components;
• Fiber, cable, and waveguide technologies, including materials, splicing, connectors, measurement techniques, etc.;
• Signal processes, including technologies related to artificial intelligence, machine learning;
• Radio over fiber, including technologies related to digital/analog linearization, radio frequency/microwave circuits over fiber communication, photoelectric modulators, photoelectric detectors, etc.

This Topic aims to collect the results of research in these and other relevant areas of fiber optic communication. The submission of papers within those areas with strong connection to beyond 5G/6G/THz over fiber applications is strongly encouraged.

Prof. Dr. (John) Xiupu Zhang
Dr. Gaoming Xu
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Applied Sciences applsci	2.7	4.5	2011	16.9 Days	CHF 2400
Electronics electronics	2.9	4.7	2012	15.6 Days	CHF 2400
Optics optics	-	-	2020	17.7 Days	CHF 1200
Photonics photonics	2.4	2.3	2014	15.5 Days	CHF 2400
Sensors sensors	3.9	6.8	2001	17 Days	CHF 2600

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Published Papers (31 papers)

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16 pages, 3641 KiB  

Open AccessArticle

Enhanced Performance of Artificial-Neural-Network-Based Equalization for Short-Haul Fiber-Optic Communications

by Mahmoud M. T. Maghrabi, Hariharan Swaminathan, Shiva Kumar, Mohamed H. Bakr and Shirook M. Ali

Sensors 2023, 23(13), 5952; https://doi.org/10.3390/s23135952 - 27 Jun 2023

Viewed by 1135

Abstract

This work proposes an efficient and easy-to-implement single-layer artificial neural network (ANN)-based equalizer with improved compensation performance. The proposed equalizer is used for effectively mitigating the distortions induced in the short-haul fiber-optic communication systems based on intensity modulation and direct detection (IMDD). The [...] Read more.

This work proposes an efficient and easy-to-implement single-layer artificial neural network (ANN)-based equalizer with improved compensation performance. The proposed equalizer is used for effectively mitigating the distortions induced in the short-haul fiber-optic communication systems based on intensity modulation and direct detection (IMDD). The compensation performance of the ANN equalizer is significantly improved, exploiting an introduced advanced training scheme. The efficiency and robustness of the proposed ANN equalizer are illustrated through 10- and 28-Gbaud short-reach optical-fiber communication systems. Compared to the efficient but computationally expensive maximum likelihood sequence estimator (MLSE), the proposed ANN equalizer not only significantly reduces its computational equalization cost and storage memory requirements, but it also outperforms its bit error rate performance. Full article

(This article belongs to the Topic Fiber Optic Communication)

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13 pages, 6800 KiB  

Open AccessReview

Two-Channel OTDM System for Data-Center Interconnects: A Review

by Sunghyun Bae and Hyeon-June Kim

Sensors 2023, 23(13), 5908; https://doi.org/10.3390/s23135908 - 26 Jun 2023

Viewed by 1111

Abstract

It has been proposed to implement the >100 Gb/s data-center interconnects using a two-channel optical time-division multiplexed system with multilevel pulse-amplitude modulation. Unlike the conventional four-channel optical time-division multiplexed system which requires an expensive narrow pulse, the two-channel system can be implemented cost-effectively [...] Read more.

It has been proposed to implement the >100 Gb/s data-center interconnects using a two-channel optical time-division multiplexed system with multilevel pulse-amplitude modulation. Unlike the conventional four-channel optical time-division multiplexed system which requires an expensive narrow pulse, the two-channel system can be implemented cost-effectively using a wide pulse (which can be simply generated using a single modulator). The two-channel system is expected to be practically available using an integrated transmitter in a chip due to the recent advances in photonics-integrated circuits. This paper reviews the current stage of research on a two-channel optical time-division multiplexed system and discusses possible research directions. Furthermore, it has been demonstrated that 200 Gb/s signals can be generated by using modulators with only 17.2 GHz bandwidth. Therefore, the use of the phase-alternating pulse can make the multiplexed signal robust to chromatic dispersion, enabling the 200 Gb/s 4-level pulse-amplitude-modulated signal to be transmitted over 1.9 km of standard single-mode fiber. Full article

(This article belongs to the Topic Fiber Optic Communication)

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9 pages, 3104 KiB  

Open AccessCommunication

SNR Model of Optical Fiber Acoustic Sensing System Based on F-P Structure

by Yingjie Liu, Chenggang Guan, Yala Tong, Wenxiu Chu, Ruling Zhou and Yikai Zhou

Photonics 2023, 10(6), 676; https://doi.org/10.3390/photonics10060676 - 11 Jun 2023

Cited by 2 | Viewed by 1064

Abstract

The signal-to-noise ratio (SNR) is a crucial parameter for assessing audio transmission quality and fiber optic acoustic sensors. This study presents a model for predicting the SNR of a fiber optic F-P acoustic sensing system using the Fabry–Perot (F-P) cavity length modulation principle, [...] Read more.

The signal-to-noise ratio (SNR) is a crucial parameter for assessing audio transmission quality and fiber optic acoustic sensors. This study presents a model for predicting the SNR of a fiber optic F-P acoustic sensing system using the Fabry–Perot (F-P) cavity length modulation principle, considering noise and line loss in the optical path. To validate the model, we constructed an F-P acoustic sensor system and measured the SNR in a semi-anechoic room. Additionally, we used MATLAB to simulate the SNR model and compared the results with experimental data. The model accurately predicted the SNR of the fiber optic F-P acoustic sensor system. Our results offer valuable guidance and theoretical support for optimizing system performance. Full article

(This article belongs to the Topic Fiber Optic Communication)

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14 pages, 5163 KiB  

Open AccessArticle

A Low-Complexity Joint Compensation Scheme of Carrier Recovery for Coherent Free-Space Optical Communication

by Xinyu Tang, Liqian Wang, Wei Zhang, Shanyong Cai, Yuemei Li and Zhiguo Zhang

Photonics 2023, 10(4), 389; https://doi.org/10.3390/photonics10040389 - 01 Apr 2023

Viewed by 1010

Abstract

In this paper, a low-complexity joint compensation scheme of carrier recovery (JCSCR) for coherent free-space optical (CFSO) communication is proposed. We applied the carrier recovery joint compensation approach to a CFSO communication system in the quadrature phase shift keying (QPSK) modulation format. A [...] Read more.

In this paper, a low-complexity joint compensation scheme of carrier recovery (JCSCR) for coherent free-space optical (CFSO) communication is proposed. We applied the carrier recovery joint compensation approach to a CFSO communication system in the quadrature phase shift keying (QPSK) modulation format. A signal-preprocessing stage, which effectively avoided the repetitive operations found in traditional carrier recovery schemes, was proposed. Unlike in existing carrier recovery algorithms, the modulated phase of the received signal could be accurately removed using only the sum and subtraction of real absolute values in the signal-preprocessing stage, greatly reducing the complexity of the operation. Since this algorithm avoids the traditional fourth operation, the system’s complexity is reduced while additional noise generated by fourth cross-terms would be prevented and system noise immunity would be greatly enhanced. In addition, this algorithm uses joint compensation of phase errors in the final compensation stage, further reducing the complexity of the computation of the whole algorithmic scheme. A 10 Gbps QPSK CFSO communication transmission experiment was conducted in an atmospheric turbulence channel to verify the proposed technique and improvement in receiver sensitivity. Full article

(This article belongs to the Topic Fiber Optic Communication)

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15 pages, 3818 KiB  

Open AccessArticle

Modulation Format Identification and OSNR Monitoring Based on Multi-Feature Fusion Network

by Jingjing Li, Jie Ma, Jianfei Liu, Jia Lu, Xiangye Zeng and Mingming Luo

Photonics 2023, 10(4), 373; https://doi.org/10.3390/photonics10040373 - 27 Mar 2023

Cited by 1 | Viewed by 1054

Abstract

In this paper, we propose a multi-feature fusion network (MFF-Net) for a modulation format identification (MFI) and optical signal-to-noise ratio (OSNR) monitoring scheme. The constellation map data used in this work comes from five modulation formats, namely 56 Gbit/s 4/8 phase shift keying [...] Read more.

In this paper, we propose a multi-feature fusion network (MFF-Net) for a modulation format identification (MFI) and optical signal-to-noise ratio (OSNR) monitoring scheme. The constellation map data used in this work comes from five modulation formats, namely 56 Gbit/s 4/8 phase shift keying (PSK) and 16/32/64 quadrature amplitude modulation (QAM). The constellation maps are input to one branch network of the MFF-Net, and then the constellation maps are processed by horizontal projection and used as input to another branch network as a way to fuse the two image features. The results show that the scheme achieves 100% MFI accuracy and 98.82% OSNR monitoring accuracy for the five modulation formats. In addition, the performance of MFF-Net and binarized convolutional neural network (B-CNN), visual geometry group network (VGG-Net), and traditional weighted multi-task learning (EW-MTL) are compared to present the superiority of the method. The effect of model structure on MFF-Net is also discussed. The robustness of the model is also evaluated for different transmission distances and bit rates. Full article

(This article belongs to the Topic Fiber Optic Communication)

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10 pages, 3942 KiB  

Open AccessCommunication

Key Space Enhancement of Chaos Communication Using Semiconductor Lasers with Spectrum-Programmable Optoelectronic Feedback

by Yuanyuan Guo, Dongsheng Wang, Longsheng Wang, Zhiwei Jia, Tong Zhao, Pengfa Chang, Yuncai Wang and Anbang Wang

Photonics 2023, 10(4), 370; https://doi.org/10.3390/photonics10040370 - 26 Mar 2023

Cited by 1 | Viewed by 1102

Abstract

We propose a scheme for key-space-enhanced chaos secure communication using semiconductor lasers with spectrum-programmable optoelectronic feedback. This feedback consists of multiple parallel optoelectronic feedback loops composed of bandpass filters and radio-frequency amplifiers. The centre frequencies of the filters and gain coefficients of the [...] Read more.

We propose a scheme for key-space-enhanced chaos secure communication using semiconductor lasers with spectrum-programmable optoelectronic feedback. This feedback consists of multiple parallel optoelectronic feedback loops composed of bandpass filters and radio-frequency amplifiers. The centre frequencies of the filters and gain coefficients of the amplifiers increase the key space. We use 12 parallel filtered feedback loops to analyse the effects of parameter mismatch on the synchronization quality. The simulation result indicates that the key space reaches approximately 2¹⁰⁰ at a data rate of 10 Gbit/s, and it can be further enhanced by increasing the number of feedback loops. These results suggest an alternative approach for security-enhanced optical chaos communication. Full article

(This article belongs to the Topic Fiber Optic Communication)

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13 pages, 4485 KiB  

Open AccessArticle

Impact of Intracavity Power Variations toward Ultrashort Pulse Generation

by Ahmad Fauzi Abas, Kuen Yao Lau, Yahya Mohammed Al-Moliki, Yosef Taher Aladadi, Mohammed Thamer Alresheedi and Mohd Adzir Mahdi

Appl. Sci. 2023, 13(7), 4087; https://doi.org/10.3390/app13074087 - 23 Mar 2023

Cited by 1 | Viewed by 1188

Abstract

This study demonstrates a passive mode-locked erbium-doped fiber laser with a graphene nanoplatelet-saturable absorber (GNP-SA) that generates ultrashort pulses within femtosecond pulse duration. The GNP-SA is fabricated via a direct transfer approach by mechanically exfoliated graphene on a fiber ferrule. Its characteristics include [...] Read more.

This study demonstrates a passive mode-locked erbium-doped fiber laser with a graphene nanoplatelet-saturable absorber (GNP-SA) that generates ultrashort pulses within femtosecond pulse duration. The GNP-SA is fabricated via a direct transfer approach by mechanically exfoliated graphene on a fiber ferrule. Its characteristics include 0.8% modulation depth, 8.7 MW/cm² saturation fluence, and 36.8% absorbance. The quality of ultrashort pulses is studied with a variation of intracavity circulating powers that is controlled through an optical coupler. By changing the light intensity in the cavity, the optical amplification property in the erbium-doped fiber is also impacted. The increment of the output coupling ratio increases the population inversion in the active gain medium, which leads to the change of lasing wavelength from 1558 to 1532 nm. Using a 50% output coupling ratio, the fiber laser generates 960 fs pulse duration, 11.08 MHz repetition rate, and 6.05 mW output power. This study contributes to the understanding of oscillating light behavior while changing its intracavity power that affects the optical amplification properties. Full article

(This article belongs to the Topic Fiber Optic Communication)

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18 pages, 14817 KiB  

Open AccessArticle

A DIDE-FPP Composite Algorithm for Accurate Tunnel Fire Location

by Hong Jiang, Yihan Zhao, Chenyang Wang and Lina Cui

Photonics 2023, 10(3), 272; https://doi.org/10.3390/photonics10030272 - 03 Mar 2023

Viewed by 880

Abstract

We propose a DIDE-FPP composite algorithm to improve the spatial location accuracy of tunnel fires based on the distributed individuals differential evolution (DIDE) algorithm and the four-point positioning (FPP) method. Using the DIDE algorithm to solve the multimodal optimization problems in tunnel fire [...] Read more.

We propose a DIDE-FPP composite algorithm to improve the spatial location accuracy of tunnel fires based on the distributed individuals differential evolution (DIDE) algorithm and the four-point positioning (FPP) method. Using the DIDE algorithm to solve the multimodal optimization problems in tunnel fire location can locate more peaks and improve peak finding, and the FPP method is used to process the peak points located using the DIDE and achieve the spatial location which cannot be achieved otherwise using the DIDE method only. We used 20 multimodal test functions to evaluate the performance of the DIDE-FPP algorithm in peak finding and solving MMOPs. Through experimental comparisons with 13 other existing advanced methods, the comprehensive performance of the proposed DIDE-FPP composite algorithm shows advantages to some extents. Additionally, the combined value of PR (peak ratio) and SR (success rate) on up to 20 experimental functions is relatively high. The spatial positioning accuracy of a tunnel fire warning system using this positioning method can reach the centimeter level. Full article

(This article belongs to the Topic Fiber Optic Communication)

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24 pages, 7491 KiB  

Open AccessArticle

Analysis of Crosstalk in Multicore Fibers: Statistical Distributions and Analytical Expressions

by Kam Ng, Vladimir Nazarov, Sergey Kuchinsky, Aramais Zakharian and Ming-Jun Li

Photonics 2023, 10(2), 174; https://doi.org/10.3390/photonics10020174 - 07 Feb 2023

Cited by 2 | Viewed by 1716

Abstract

We present a study of multicore fiber (MCF) crosstalk using the coupled mode theory. We derived a general closed-form simulation formula for the crosstalk of MCF under random perturbations, which includes both the average crosstalk and the crosstalk statistical distribution. From this general [...] Read more.

We present a study of multicore fiber (MCF) crosstalk using the coupled mode theory. We derived a general closed-form simulation formula for the crosstalk of MCF under random perturbations, which includes both the average crosstalk and the crosstalk statistical distribution. From this general formula, we further derived simple analytical expressions for the average crosstalk under the assumption of exponential distribution of fiber segment lengths. We show that the analytical expressions approximate very well the results for other distributions, such as Dirac and Gaussian, and thus they can be used as a general analytical approach for estimating the average crosstalk. Results from numerical simulations of average crosstalk are shown to be in full correspondence with analytic results. We also performed numerical simulations of crosstalk statistical distributions generated from our general closed-form simulation formula and find that these agree well with the χ²-distribution function with four degrees of freedom. Finally, we conducted crosstalk measurements under different bending deployment conditions, and the measured crosstalk distributions and average crosstalk are found to be in agreement with the modeling results. Full article

(This article belongs to the Topic Fiber Optic Communication)

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12 pages, 5362 KiB  

Open AccessArticle

The Explanation of Photopic Luminous Efficiency Curve by Using Both of the Cones’ Optical Fiber Coupling Effects and the Absorption of L Cones

by Anhui Liang, Kexin Yu, Xiaolin Min, Jing Li, Jianyu Li, Xiaoling Zuo and Youli Yao

Sensors 2023, 23(3), 1523; https://doi.org/10.3390/s23031523 - 30 Jan 2023

Viewed by 1291

Abstract

In this paper, we build four-part cone models to explore the coupling effect of seven cone fiber couplers. Moreover, this is the first study of the coupling effect of four layers of biological couplers in animals and other biological lives. We simulate the [...] Read more.

In this paper, we build four-part cone models to explore the coupling effect of seven cone fiber couplers. Moreover, this is the first study of the coupling effect of four layers of biological couplers in animals and other biological lives. We simulate the four layers cone couplers by using the beam propagation method, and we assume the input beam is located at the outer fiber of the central cone. Our simulation results showed that there are two wavelength regions (short and long wavelength regions) with the strongest coupling, where the most power of input optical powers of the central cones will transfer to the six surrounding cones after transmitting through the four layers of cone couplers. However, within a wavelength region of ±75 nm near to the peak wavelengths, located in the yellow–green wavelength range, the splitting ratios at the output of the outer segment of the central cone are always greater than the sum of the splitting ratios of the six surrounding cones. These cone couplers may play an important role in color preprocessing (e.g., doing opponent color processing partially). The cone fiber coupler effect and light absorption of cones are considered separately in our models. By taking account of both the cone fiber coupling effect and absorption of outer segment of L cone, we find the multiplication of the relative optical power of cone couplers, the spectral sensitivity data of the L cone, and a normalized coefficient that matches with the photopic luminous efficiency of the human eye well. This is the attempt to use both the cone fiber coupling effect and the absorption of L cones to explain the photopic luminous efficiency. The splitting ratios of the central cones are greater than 80% at peak wavelengths located in the yellow-green wavelength range, and this can help to explain why the human eye is more sensitive to green light. Full article

(This article belongs to the Topic Fiber Optic Communication)

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19 pages, 8427 KiB  

Open AccessArticle

Supermode Characteristics of Nested Multiple Hollow-Core Anti-Resonant Fibers

by Zequan Li, Jiantao Liu, Changming Xia, Zhiyun Hou and Guiyao Zhou

Photonics 2022, 9(11), 816; https://doi.org/10.3390/photonics9110816 - 29 Oct 2022

Viewed by 1474

Abstract

Mode-division multiplexing (MDM) can achieve ultra-high data capacity in optical fiber communication. Several impressive works on multicore fiber (MCF), multi-mode fiber, and few-mode multicore fiber have made significant achievements in MDM. However, none of the previous works can simultaneously maintain the transmission loss, [...] Read more.

Mode-division multiplexing (MDM) can achieve ultra-high data capacity in optical fiber communication. Several impressive works on multicore fiber (MCF), multi-mode fiber, and few-mode multicore fiber have made significant achievements in MDM. However, none of the previous works can simultaneously maintain the transmission loss, chromatic dispersion (CD), and differential group delay (DGD) at a relatively low level. A nested multiple hollow-core anti-resonant fiber (NMH-ARF) has significant potential for applications in MDM. This study proposes a novel NMH-ARF with its structural design based on the traditional single-core nested anti-resonant fiber. We increased the number of nodes between capillaries. By changing the position of the nested tubes, several interconnected areas form when a single core is separated. We investigated the mode-coupling theory and transmission characteristics of this fiber. This fiber structure showed a low sensitivity to bending and achieved a super-low DGD and a super-low confinement loss (CL) at a wavelength of 1.55 µm while keeping CD relatively low. Full article

(This article belongs to the Topic Fiber Optic Communication)

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10 pages, 1769 KiB  

Open AccessArticle

Performance Comparison of Different Modulation Formats for a 40 Gbps Hybrid Optical CDMA/DWDM System against ISI and FWM

by Naif Alsowaidi, Tawfig Eltaif and Mohd Ridzuan Mokhtar

Photonics 2022, 9(8), 555; https://doi.org/10.3390/photonics9080555 - 07 Aug 2022

Cited by 4 | Viewed by 1526

Abstract

This paper carries out a numerical simulation investigating three different modulation formats: carrier suppressed return to zero (CSRZ), modified duobinary return to zero (MDRZ) and return to zero (RZ). The purpose of this investigation is to find the optimum modulation format for the [...] Read more.

This paper carries out a numerical simulation investigating three different modulation formats: carrier suppressed return to zero (CSRZ), modified duobinary return to zero (MDRZ) and return to zero (RZ). The purpose of this investigation is to find the optimum modulation format for the hybrid optical code division multiple accesses–dense wavelength division multiplexing (optical CDMA/DWDM) system with the implementation of an electro-optic phase modulator (EOPM) at a data rate of 40 Gbps per channel, with a transmitted power of 22 dBm and transmission distance of 105.075 km. The results revealed that CSRZ was superior to MDRZ and RZ and was more tolerant to optical fiber nonlinearity. Furthermore, unlike the DWDM systems, the performance of the proposed hybrid system based RZ format was better than the performance of MDRZ. Hence, the CSRZ modulation format is the best candidate for the optical CDMA/DWDM with EOPM module due to its high performance. Full article

(This article belongs to the Topic Fiber Optic Communication)

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11 pages, 1315 KiB  

Open AccessCommunication

Security of Optical Beam Splitter in Quantum Key Distribution

by Dong-Dong Li, Yan-Lin Tang, Yu-Kang Zhao, Lei Zhou, Yong Zhao and Shi-Biao Tang

Photonics 2022, 9(8), 527; https://doi.org/10.3390/photonics9080527 - 28 Jul 2022

Cited by 4 | Viewed by 1729

Abstract

The optical beam splitter is an essential device used for decoding in quantum key distribution. The impact of optical beam splitters on the security of quantum key distribution was studied, and it was found that the realistic device characteristics closely influence the error [...] Read more.

The optical beam splitter is an essential device used for decoding in quantum key distribution. The impact of optical beam splitters on the security of quantum key distribution was studied, and it was found that the realistic device characteristics closely influence the error rate introduced by the wavelength-dependent attack on optical beam splitters. A countermeasure, combining device selection and error rate over-threshold alarms, is proposed to protect against such attacks. Beam splitters made of mirror coatings are recommended, and the variation of splitting ratio should be restricted to lower than 1 dB at 1260–1700 nm. For the partial attack scenario where the eavesdropper attacks only a portion of the quantum signal, a modified secure key rate formula is proposed to eliminate the revealed information of the attacked portion. Numerical results show that the QKD system adopting this countermeasure exhibits good performance with a secure key rate of over 10 kbps at 100 km and a maximum transmission distance of over 150 km, with only a small difference from the no-attack scenario. Additionally, a countermeasure to monitor the light intensity of different wavelengths is proposed to protect against the wavelength-dependent attack on optical beam splitters. Full article

(This article belongs to the Topic Fiber Optic Communication)

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9 pages, 1847 KiB  

Open AccessCommunication

The Performance of Orbital Angular Momentum Mode (|l| = 1~3) Amplification Based on Ring-Core Erbium-Doped Fibers

by Shuaishuai Liu, Liang Zhang, Qi Jiang, Xiaobo Xue, Jianxiang Wen, Wei Chen, Fufei Pang and Tingyun Wang

Photonics 2022, 9(7), 491; https://doi.org/10.3390/photonics9070491 - 13 Jul 2022

Cited by 2 | Viewed by 1419

Abstract

We demonstrated that a ring-core erbium-doped fiber amplifier (RC-EDFA) can support orbital angular momentum (OAM) modes with topological charges (|l| = 1~3). The dependence of the characteristics on the length of the RC-EDF was investigated experimentally, including an investigation of gain [...] Read more.

We demonstrated that a ring-core erbium-doped fiber amplifier (RC-EDFA) can support orbital angular momentum (OAM) modes with topological charges (|l| = 1~3). The dependence of the characteristics on the length of the RC-EDF was investigated experimentally, including an investigation of gain and 3 dB gain bandwidth over the whole C band (i.e., 1530~1565 nm). The 3 dB gain bandwidth was improved to 21 nm. At a signal wavelength of 1550 nm, the maximum gain of all signal modes was up to 30.1 dB. Differential modal gain was maintained below approximately 1.3 dB. Full article

(This article belongs to the Topic Fiber Optic Communication)

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14 pages, 4877 KiB  

Open AccessArticle

Cladding-Pumped Er/Yb-Co-Doped Fiber Amplifier for Multi-Channel Operation

by Kaspars Zakis, Sergejs Olonkins, Aleksejs Udalcovs, Ingars Lukosevics, Dmitrijs Prigunovs, Jurgis Grube, Liga Bikse, Andis Supe, Oskars Ozolins, Sandis Spolitis and Vjaceslavs Bobrovs

Photonics 2022, 9(7), 457; https://doi.org/10.3390/photonics9070457 - 28 Jun 2022

Cited by 4 | Viewed by 2317

Abstract

Cladding-pumped erbium (Er³⁺)/ytterbium (Yb³⁺)-co-doped fiber amplifiers are more advantageous at high output powers. However, this amplification technique also has potential in telecom-related applications. These types of amplifiers have complex properties, especially when considering gain profile and a pump conversion [...] Read more.

Cladding-pumped erbium (Er³⁺)/ytterbium (Yb³⁺)-co-doped fiber amplifiers are more advantageous at high output powers. However, this amplification technique also has potential in telecom-related applications. These types of amplifiers have complex properties, especially when considering gain profile and a pump conversion efficiency. Such metrics depend on the doped fiber profile, absorption/emission spectra, and the input signal power. In this context, we design, build and characterize an inhouse prototype of cladding-pumped Er³⁺/Yb³⁺-co-doped fiber amplifier (EYDFA). Our goal is to identify the EYDFA configuration (a co-doped fiber length, pump power, input signal power) suitable for signal amplification in a multichannel fiber-optic transmission system with a dense wavelength allocation across the C-band (1530–1565 nm). Our approach involves experimentally determining the Er³⁺/Yb³⁺-co-doped fiber’s parameters to be used in a simulation setup to decide on an initial EYDFA configuration before moving to a laboratory setup. An experimental EYDFA prototype is tested under different conditions using a 48-channel dense wavelength division multiplexing (DWDM, 100 GHz) system to evaluate the absolute gain and gain uniformity. The obtained results allow the cladding pump amplifier’s suitability for wideband signal amplification to be assessed. The developed prototype provides >21 dB of gain with a 12 dB ripple within 1534–1565 nm. Furthermore, we show that the gain profile can be partially flattened out by using longer EYDF spans. This enhances signal amplification in the upper C-band in exchange for a weaker amplification in the lower C-band, which can be marginally improved with higher pump powers. Full article

(This article belongs to the Topic Fiber Optic Communication)

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13 pages, 4872 KiB  

Open AccessArticle

Design and Performance Analysis of Hybrid Multidimensional OAM-DM-WDM-OFDM-PON System with High-Capacity and Long-Distance Transmission

by Qingan Ding, Li Zheng, Huixin Liu, Junkai Li, Xiaohan Guo, Xudong Cheng, Zhenfei Dai, Qunying Yang and Jun Li

Photonics 2022, 9(7), 448; https://doi.org/10.3390/photonics9070448 - 27 Jun 2022

Cited by 5 | Viewed by 1687

Abstract

Orbital angular momentum (OAM) with mutually orthogonal advantage attribute to break through the high capacity and long-reach transmission limited in the classical passive optical network (PON). Employing Laguerre Gaussian (LG) mode as the orthogonal OAM excitation, a more dimensional multiplexing PON system is [...] Read more.

Orbital angular momentum (OAM) with mutually orthogonal advantage attribute to break through the high capacity and long-reach transmission limited in the classical passive optical network (PON). Employing Laguerre Gaussian (LG) mode as the orthogonal OAM excitation, a more dimensional multiplexing PON system is proposed to creatively hybridize OAM division multiplexing (OAM-DM) based on wavelength division multiplexing (WDM) and orthogonal frequency division multiplexing (OFDM). By utilizing the compatibility of OAM-DM and WDM, data of $40$ Gbit/s OFDM signals is successfully transmitted in 80 km multimode fiber (MMF) with low crosstalk. Within this hybrid system, the effects of different wavelengths and different modes on the bit error rate (BER) are discussed at varying transmission distances. Moreover, the performance of several subsystems carrying quadrature phase-shift keying (QPSK), on-off keying (OOK), and OFDM modulation signals is also compared at a BER less than $3.8\times {10}^{-3}$. It is observed that the proposed OAM-DM-WDM-OFDM-PON system has favorable performance, which is a reasonable solution for large-capacity PON architecture. Full article

(This article belongs to the Topic Fiber Optic Communication)

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10 pages, 2376 KiB  

Open AccessArticle

Experimental Research on In Situ Uniaxial Tensile Response of Silica-Based PLC Optical Splitters

by Yu Zheng, Lianqiong Jiang, Jie Cheng, Jianzhe Liu and Ji’an Duan

Appl. Sci. 2022, 12(12), 5778; https://doi.org/10.3390/app12125778 - 07 Jun 2022

Cited by 2 | Viewed by 1496

Abstract

In this study, the mechanical and optical properties of silica-based planar lightwave circuit (PLC) optical splitters under uniaxial tensile loading are studied by building an in situ experimental test platform. The tensile test results revealed that the adhesively-bonded fiber array-PLC chip joints are [...] Read more.

In this study, the mechanical and optical properties of silica-based planar lightwave circuit (PLC) optical splitters under uniaxial tensile loading are studied by building an in situ experimental test platform. The tensile test results revealed that the adhesively-bonded fiber array-PLC chip joints are weak areas of the PLC optical splitter. Combined with the real-time monitoring of the optical performance index insertion loss (IL) during the tensile test, it was found that the changing trend of ΔIL-time curves is related to the deformation, damage, and debonding process of the weak area. Based on the experimental results and phenomena, the correspondence between ΔIL at 1.55 μm wavelength and the damage degree of PLC optical splitters is established, that is, ΔIL in (−5 dB; 0 dB], (−15 dB; −5 dB], and (−∞, −15 dB] belong to light damage, moderate damage, and severe damage, respectively. This research can provide a useful reference for damage characteristics analysis and reliability design of PLC optical splitters. Full article

(This article belongs to the Topic Fiber Optic Communication)

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9 pages, 3190 KiB  

Open AccessArticle

Dual Polarization Simultaneous Optical Intensity Modulation in Single Birefringent LiNbO₃ Mach–Zehnder Optical Modulator

by Young-Jin Hyun, Jae-Young Choi and Sang-Kook Han

Photonics 2022, 9(6), 386; https://doi.org/10.3390/photonics9060386 - 30 May 2022

Cited by 1 | Viewed by 1744

Abstract

A new method of simultaneous modulation of dual-polarization intensity based on a single LiNbO₃ Mach–Zehnder modulator (MZM) is proposed. Using the birefringence of lithium niobate, the bipolar optical intensity can be modulated independently with the proposed modulation condition. In this paper, the [...] Read more.

A new method of simultaneous modulation of dual-polarization intensity based on a single LiNbO₃ Mach–Zehnder modulator (MZM) is proposed. Using the birefringence of lithium niobate, the bipolar optical intensity can be modulated independently with the proposed modulation condition. In this paper, the optimized modulation conditions and the performance of the proposed method are investigated through simulations and experiments. Full article

(This article belongs to the Topic Fiber Optic Communication)

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15 pages, 6854 KiB  

Open AccessArticle

Silica Microsphere WGMR-Based Kerr-OFC Light Source and Its Application for High-Speed IM/DD Short-Reach Optical Interconnects

by Toms Salgals, Janis Alnis, Oskars Ozolins, Alexey V. Andrianov, Elena A. Anashkina, Inga Brice, Roberts Berkis, Xiaodan Pang, Aleksejs Udalcovs, Jurgis Porins, Sandis Spolitis and Vjaceslavs Bobrovs

Appl. Sci. 2022, 12(9), 4722; https://doi.org/10.3390/app12094722 - 07 May 2022

Cited by 3 | Viewed by 2057

Abstract

Kerr optical frequency combs (OFCs) based on silica microsphere whispering gallery mode resonator (WGMR) have various applications where they are used as a light source. For telecommunication purposes, WGMR-based Kerr-OFC comb generators can be physically realized using silica microsphere resonators and can be [...] Read more.

Kerr optical frequency combs (OFCs) based on silica microsphere whispering gallery mode resonator (WGMR) have various applications where they are used as a light source. For telecommunication purposes, WGMR-based Kerr-OFC comb generators can be physically realized using silica microsphere resonators and can be used to replace multiple laser arrays. In such a realization, these novel light sources have the potential to demonstrate an attractive solution for intra-datacenter interconnects (DCI). In this paper, we show an experimental demonstration of a silica microsphere WGMR-based Kerr OFC light source where newly generated 400 GHz spaced carriers together with powerful linear equalization techniques, such as a linear symbol-spaced adaptive decision-feedback equalizer (DFE) with feed-forward (FF) and feedback (FB) taps, provide an alternative to individual lasers ensuring low-cost and low-complexity IM/DD scheme for the transmission of NRZ-OOK modulated signals at data rates up to 50 Gbps/λ over 2 km SMF link. Finally, we demonstrate a record 50 Gbps per λ transmission of NRZ-OOK modulated signals with a novel silica microsphere WGMR-based Kerr-OFC as a light source operating in the optical C-band, surpassing the previously demonstrated data rate record by five times. Full article

(This article belongs to the Topic Fiber Optic Communication)

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18 pages, 4562 KiB  

Open AccessArticle

Machine Learning-Based Optical Performance Monitoring for Super-Channel Optical Networks

by Waddah S. Saif, Amr M. Ragheb, Bernd Nebendahl, Tariq Alshawi, Mohamed Marey and Saleh A. Alshebeili

Photonics 2022, 9(5), 299; https://doi.org/10.3390/photonics9050299 - 28 Apr 2022

Cited by 3 | Viewed by 2094

Abstract

In this paper, and for the first time in literature, optical performance monitoring (OPM) of super-channel optical networks is considered. In particular, we propose a novel machine learning OPM technique based on the use of transformed in-phase quadrature histogram (IQH) features and support [...] Read more.

In this paper, and for the first time in literature, optical performance monitoring (OPM) of super-channel optical networks is considered. In particular, we propose a novel machine learning OPM technique based on the use of transformed in-phase quadrature histogram (IQH) features and support vector regressor (SVR) to estimate different optical parameters such as optical signal-to-noise ratio (OSNR) and chromatic dispersion (CD). Two transformation methods, the two-dimensional (2D) discrete Fourier transform (DFT) and 2D discrete cosine transform (DCT), are applied to the IQH to extract features with a considerably reduced dimensionality. For the purpose of simulation, the OPM of a 7 × 20 Gbaud dual-polarization–quadrature phase shift keying (DP-QPSK) is considered. Simulations reveal that it can accurately estimate the various optical parameters (i.e., OSNR and CD) with a coefficient of determination value greater than 0.98. In addition, the effectiveness of proposed OPM scheme is examined under different values of polarization mode dispersion and frequency offset, as well as the utilization of different higher order modulation formats. Moreover, proof-of-concept experiments are performed for validation. The results show an excellent matching between the simulation and experimental findings. Full article

(This article belongs to the Topic Fiber Optic Communication)

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11 pages, 4207 KiB  

Open AccessArticle

Study of an Optical Fiber Time Transmission Method with Real-Time Average Temperature Measurement of Links

by Ding Chen, Jiangning Xu, Xiaorong Tan and Miao Wu

Photonics 2022, 9(5), 293; https://doi.org/10.3390/photonics9050293 - 26 Apr 2022

Viewed by 1505

Abstract

The temperature of optical fiber links is an important factor affecting the accuracy of optical fiber time transmission. However, the real-time temperature measurement of optical fiber links in field networks is difficult and contains many errors. In this paper, a new method for [...] Read more.

The temperature of optical fiber links is an important factor affecting the accuracy of optical fiber time transmission. However, the real-time temperature measurement of optical fiber links in field networks is difficult and contains many errors. In this paper, a new method for the real-time average temperature measurement of optical fiber links is proposed. By accurately measuring the round-trip time delay of the optical fiber link and filtering out the delay jitter and system noise through the Kalman filter, the real-time average temperature of optical fiber links can be accurately calculated. The experimental results in the temperature control box show that the temperature measurement accuracy of this method is about 0.015 °C. Under the condition of a significant temperature change, the time synchronization accuracy of the round-trip system can reach the sub-nanosecond level and the time stability is less than 35 ps/s and 8 ps/10⁴ s. Full article

(This article belongs to the Topic Fiber Optic Communication)

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10 pages, 2542 KiB  

Open AccessArticle

Linearly Swept Tunable Laser Source with Closed-Loop Control of Drive Waveform

by Yunhae Yeh

Electronics 2022, 11(9), 1371; https://doi.org/10.3390/electronics11091371 - 25 Apr 2022

Viewed by 1202

Abstract

A method for a linearly swept tunable laser source with a simple configuration is proposed. The principle of the method is based on the fact that the interval of the transmission peaks of a fixed etalon can be used as a stable reference. [...] Read more.

A method for a linearly swept tunable laser source with a simple configuration is proposed. The principle of the method is based on the fact that the interval of the transmission peaks of a fixed etalon can be used as a stable reference. The reference provided by the fixed etalon is used to deform the drive signal waveform for linear optical-frequency tuning. To verify the validity of the methodology, an optical system augmented with two fiber Bragg gratings, one fixed etalon, and a dedicated signal-processing circuit was built and experimentally tested, confirming that it works well for a linearly tuned tunable laser source. Moreover, the potential for extending the scope of the application of the proposed method is suggested and some ways to improve its performance are also discussed. Full article

(This article belongs to the Topic Fiber Optic Communication)

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17 pages, 8891 KiB  

Open AccessArticle

Reduction of Complexity Design of SAC OCDMA Systems by Utilizing Diagonal Permutation Shift (DPS) Codes with Single Photodiode (SPD) Detection Technique

by Hassan Yousif Ahmed, Medien Zeghid, Belgacem Bouallegue, Abdellah Chehri and Somia A. Abd El-Mottaleb

Electronics 2022, 11(8), 1224; https://doi.org/10.3390/electronics11081224 - 12 Apr 2022

Cited by 15 | Viewed by 1338

Abstract

In this paper, a diagonal permutation code is presented for spectral amplitude coding optical code division multiple access (SAC-OCDMA) employing a single photodiode (SPD) detection technique. It is characterized by practical code length and ideal in-phase cross correlation (CC) that results in multiple [...] Read more.

In this paper, a diagonal permutation code is presented for spectral amplitude coding optical code division multiple access (SAC-OCDMA) employing a single photodiode (SPD) detection technique. It is characterized by practical code length and ideal in-phase cross correlation (CC) that results in multiple access interference (MAI) suppression. A diagonal permutation shift (DPS) code can be constructed using both prime codes and some matrix operations. In addition, it can be easily implemented as it exists for prime numbers P, which limits the addressing probability of codes to P2. Fiber Bragg gratings (FBGs) are used for code encoding and decoding. Simulation analysis that calibrates with BER, Q-factor, and eye diagram proves that DPS code using SPD technique is able to maintain error free transmission compared to the complementary detection scheme (CDS) technique. It is reported that a reduction of fiber Bragg grating (FBG) sets by 41.6% was achieved for SPD over CDS techniques. Full article

(This article belongs to the Topic Fiber Optic Communication)

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16 pages, 6091 KiB  

Open AccessArticle

Topology-Abstraction-Based Protection Scheme in Quantum Key Distribution Networks with Partially Trusted Relays

by Qin Zhang, Yikai Liu, Xiaosong Yu, Yongli Zhao and Jie Zhang

Photonics 2022, 9(4), 239; https://doi.org/10.3390/photonics9040239 - 03 Apr 2022

Cited by 3 | Viewed by 2452

Abstract

Quantum key distribution (QKD) can protect the exchange process of confidential information between communicating parties. By using the basic principles of quantum mechanics and combined with “one-time pad” cipher encryption, information can be unconditionally secure. The BB84 protocol first describes the method of [...] Read more.

Quantum key distribution (QKD) can protect the exchange process of confidential information between communicating parties. By using the basic principles of quantum mechanics and combined with “one-time pad” cipher encryption, information can be unconditionally secure. The BB84 protocol first describes the method of transmitting information by photon polarization state, and it expounds the transmission process of services between trusted relays. However, due to the defects of real experimental devices, there are security vulnerabilities in QKD in a real system. The birth of measurement-device-independent quantum key distribution (MDI-QKD) protocol solves the problem, providing immunity to hacker attacks at the end of the detector. It can enable both sides of the transmission service to establish a connection and generate secret keys through an untrusted relay node to ensure information security. However, the types and properties of link nodes in quantum key distribution network (QKDN) based on partially trusted relay are more complex, which can easily result in network fault. Therefore, how to prevent the impact of failure on QKDN has become an urgent problem. In this paper, we propose a protection scheme for QKDN with partially trusted relays. The method deals with trusted and untrusted relays differently and constructs the working and protection paths of the secret key for each service. It reduces resource conflict between the protection and working paths by establishing a key protection threshold, which realizes the resource trade-off between the two factors. Simulation results show that the scheme provides effective protection to the services, and it improves the stability and reliability of QKDN based on partially trusted relay. Full article

(This article belongs to the Topic Fiber Optic Communication)

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13 pages, 3051 KiB  

Open AccessArticle

Dispersion Management and Pulse Characterization of Graphene-Based Soliton Mode-Locked Fiber Lasers

by Ahmad Fauzi Abas, Kuen Y. Lau, Wazie M. Abdulkawi, Mohammed T. Alresheedi, Farah D. Muhammad and Mohd Adzir Mahdi

Appl. Sci. 2022, 12(7), 3288; https://doi.org/10.3390/app12073288 - 24 Mar 2022

Cited by 7 | Viewed by 1936

Abstract

This paper presents the generation and characterization of femtosecond pulses utilizing graphene-polymethyl-methacrylate (PMMA) thin-film saturable absorber (SA), which is subjected to different lengths of single-mode fiber (SMF) in an erbium-doped fiber laser cavity. The graphene/PMMA-SA is prepared by using a simple transfer procedure [...] Read more.

This paper presents the generation and characterization of femtosecond pulses utilizing graphene-polymethyl-methacrylate (PMMA) thin-film saturable absorber (SA), which is subjected to different lengths of single-mode fiber (SMF) in an erbium-doped fiber laser cavity. The graphene/PMMA-SA is prepared by using a simple transfer procedure of the thin-film on a fiber ferrule. By increasing the SMF length from 0 to 4 m, the corresponding group velocity dispersion of the entire cavity is estimated to change from −0.033 to −0.121 ps². Analysis of the pulse performance shows that the pulse width behavior varies from 820 fs to 710 fs against different cavity lengths. Similarly, the pulse repetition rate and the spectral bandwidth can be adjusted from 12.5 to 10.0 MHz, and from 8.2 to 5.6 nm, respectively. A comprehensive discussion on the pulse performance is presented, which can contribute to widening the knowledge on the operation of graphene-based soliton mode-locked erbium-doped fiber lasers based on dispersion management by controlling the cavity length. Full article

(This article belongs to the Topic Fiber Optic Communication)

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16 pages, 2723 KiB  

Open AccessArticle

Structured Light Transmission under Free Space Jamming: An Enhanced Mode Identification and Signal-to-Jamming Ratio Estimation Using Machine Learning

by Ahmed B. Ibrahim, Amr M. Ragheb, Waddah S. Saif and Saleh A. Alshebeili

Photonics 2022, 9(3), 200; https://doi.org/10.3390/photonics9030200 - 20 Mar 2022

Cited by 1 | Viewed by 1740

Abstract

In this paper, we develop new classification and estimation algorithms in the context of free space optics (FSO) transmission. Firstly, a new classification algorithm is proposed to address efficiently the problem of identifying structured light modes under jamming effect. The proposed method exploits [...] Read more.

In this paper, we develop new classification and estimation algorithms in the context of free space optics (FSO) transmission. Firstly, a new classification algorithm is proposed to address efficiently the problem of identifying structured light modes under jamming effect. The proposed method exploits support vector machine (SVM) and the histogram of oriented gradients algorithm for the classification task within a specific range of signal-to-jamming ratio (SJR). The SVM model is trained and tested using experimental data generated using different modes of the structured light beam, including the 8-ary Laguerre Gaussian (LG), 8-ary superposition-LG, and 16-ary Hermite Gaussian (HG) formats. Secondly, a new algorithm is proposed using neural networks for the sake of predicting the value of SJR with promising results within the investigated range of values between −5 dB and 3 dB. Full article

(This article belongs to the Topic Fiber Optic Communication)

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12 pages, 5329 KiB  

Open AccessArticle

Enhancing Energy Efficiency of the Doze Mode Mechanism in Ethernet Passive Optical Networks Using Support Vector Regression

by Cheng-Zen Yang, Mohammad Amin Lotfolahi, I-Shyan Hwang, Mohammed Syuhaimi Ab-Rahman, Aliakbar Nikoukar, Andrew Tanny Liem and Elaiyasuriyan Ganesan

Photonics 2022, 9(3), 180; https://doi.org/10.3390/photonics9030180 - 12 Mar 2022

Cited by 1 | Viewed by 1802

Abstract

An Ethernet passive optical network (EPON) is an optical access network that allows a higher data rate with low power consumption. To improve energy savings for an EPON, the sleep and doze modes for the optical network units (ONUs) play a pivotal role. [...] Read more.

An Ethernet passive optical network (EPON) is an optical access network that allows a higher data rate with low power consumption. To improve energy savings for an EPON, the sleep and doze modes for the optical network units (ONUs) play a pivotal role. Many prediction schemes have been proposed to control these modes. To increase the prediction accuracy, this study proposes an energy-efficient approach that uses a support vector regression (SVR) model. A dynamic bandwidth allocation (DBA) scheme called SVR-DBA is designed to allocate bandwidth to ONUs more efficiently and fairly. To determine the effectiveness of the proposed scheme, simulations are performed. The simulation results show that the proposed scheme decreases energy consumption for ONUs by up to 47% and fulfills the quality-of-service (QoS) requirements in terms of delay, jitter, and packet loss. Full article

(This article belongs to the Topic Fiber Optic Communication)

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11 pages, 1910 KiB  

Open AccessArticle

Low-Power Regulated Cascode CMOS Transimpedance Amplifier with Local Feedback Circuit

by Yasuhiro Takahashi, Daisuke Ito, Makoto Nakamura, Akira Tsuchiya, Toshiyuki Inoue and Keiji Kishine

Electronics 2022, 11(6), 854; https://doi.org/10.3390/electronics11060854 - 09 Mar 2022

Cited by 4 | Viewed by 3027

Abstract

In this paper, we propose a multistage transimpedance amplifier (TIA) based on the local negative feedback technique. Compared with the conventional global-feedback technique, the proposed TIA has the advantages of a wider bandwidth, and lower power dissipation. The schematic and characteristics of the [...] Read more.

In this paper, we propose a multistage transimpedance amplifier (TIA) based on the local negative feedback technique. Compared with the conventional global-feedback technique, the proposed TIA has the advantages of a wider bandwidth, and lower power dissipation. The schematic and characteristics of the proposed TIA circuit are described. Moreover, the proposed TIA employs inductive peaking to increase bandwidth. The TIA is implemented using a 65 nm complementary metal oxide semiconductor (CMOS) technology and consumes 23.9 mW with a supply voltage of 1.0 V. Using a back-annotated simulation, we obtained the following characteristics: a gain of 46 dB$\mathsf{\Omega }$ and −3 dB frequency of 11.4 GHz. TIA occupies an area of 366 $\mathsf{\mu }$m × 225 $\mathsf{\mu }$m. Full article

(This article belongs to the Topic Fiber Optic Communication)

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10 pages, 4343 KiB  

Open AccessArticle

A Simple Photonic Generation of a Microwave Waveforms Scheme Based on a Dual-Polarization Dual-Drive Mach-Zehnder Modulator

by Yiying Gu, Ruirui Gao, Yuhua Chong, Xiaozhou Li, Mingshan Zhao, Jingjing Hu and Xiuyou Han

Appl. Sci. 2022, 12(5), 2668; https://doi.org/10.3390/app12052668 - 04 Mar 2022

Cited by 2 | Viewed by 1479

Abstract

In this paper, a simple scheme for the generation of sawtooth, triangular, and square waveforms using an integrated dual-polarization dual-drive Mach-Zehnder modulator (Dpol-DDMZM) is proposed. By properly setting the working point and the modulation index of the Dpol-DDMZM, the desired microwave waveforms are [...] Read more.

In this paper, a simple scheme for the generation of sawtooth, triangular, and square waveforms using an integrated dual-polarization dual-drive Mach-Zehnder modulator (Dpol-DDMZM) is proposed. By properly setting the working point and the modulation index of the Dpol-DDMZM, the desired microwave waveforms are easily obtained after photodetection. The proposed scheme for the photonic generation of microwave waveforms is analyzed both by simulation and experiment. The periodical sawtooth, triangular, and square waveforms with repetition rates of 8 GHz are successfully generated. The root-mean-square errors (RMSE) are 0.190, 0.168, and 0.135, respectively. The system features flexible tunability. Full article

(This article belongs to the Topic Fiber Optic Communication)

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18 pages, 3528 KiB  

Open AccessArticle

Deep Neural Network Based Reconciliation for CV-QKD

by Jun Xie, Ling Zhang, Yijun Wang and Duan Huang

Photonics 2022, 9(2), 110; https://doi.org/10.3390/photonics9020110 - 15 Feb 2022

Cited by 3 | Viewed by 2468

Abstract

High-speed reconciliation is indispensable for supporting the continuous-variable quantum key distribution (CV-QKD) system to generate the secure key in real-time. However, the error correction process’s high complexity and low processing speed limit the reconciliation speed. Therefore, reconciliation has also become the bottleneck of [...] Read more.

High-speed reconciliation is indispensable for supporting the continuous-variable quantum key distribution (CV-QKD) system to generate the secure key in real-time. However, the error correction process’s high complexity and low processing speed limit the reconciliation speed. Therefore, reconciliation has also become the bottleneck of system performance. In this paper, we proposed a high-speed reconciliation scheme that uses the deep neural network to optimize the decoding process of the low-density parity-check (LDPC) code. We first introduced a network structure of decoding implementation based on the deep neural network, which can be applied to decoding algorithms of parallel strategy and significantly reduce the decoding complexity. Subsequently, we proposed two improved decoding algorithms based on this structure, named linear fitting algorithm and deep neural network-assisted decoding algorithm. Finally, we introduced a high-speed reconciliation scheme based on the CPU-GPU hybrid platform. Simulation results show that the proposed reconciliation scheme reduces the complexity and enables us to realize the high-speed CV-QKD system. Furthermore, the improved decoding algorithm can also reduce the FER, thereby increasing the secret key rate. Full article

(This article belongs to the Topic Fiber Optic Communication)

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9 pages, 3275 KiB  

Open AccessCommunication

A Nondestructive Measurement Method of Optical Fiber Young’s Modulus Based on OFDR

by Pengfei Li, Cailing Fu, Huajian Zhong, Bin Du, Kuikui Guo, Yanjie Meng, Chao Du, Jun He, Lei Wang and Yiping Wang

Sensors 2022, 22(4), 1450; https://doi.org/10.3390/s22041450 - 14 Feb 2022

Cited by 5 | Viewed by 1762

Abstract

A nondestructive measurement method based on an Optical frequency domain reflectometry (OFDR) was demonstrated to achieve Young’s modulus of an optical fiber. Such a method can be used to measure, not only the averaged Young’s modulus within the measured fiber length, but also [...] Read more.

A nondestructive measurement method based on an Optical frequency domain reflectometry (OFDR) was demonstrated to achieve Young’s modulus of an optical fiber. Such a method can be used to measure, not only the averaged Young’s modulus within the measured fiber length, but also Young’s modulus distribution along the optical fiber axis. Moreover, the standard deviation of the measured Young’s modulus is calculated to analyze the measurement error. Young’s modulus distribution of the coated and uncoated single mode fiber (SMF) samples was successfully measured along the optical fiber axis. The average Young’s modulus of the coated and uncoated SMF samples was 13.75 ± 0.14, and 71.63 ± 0.43 Gpa, respectively, within the measured fiber length of 500 mm. The measured Young’s modulus distribution along the optical fiber axis could be used to analyze the damage degree of the fiber, which is very useful to nondestructively estimate the service life of optical fiber sensors immersed into smart engineer structures. Full article

(This article belongs to the Topic Fiber Optic Communication)

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