scholarly journals Dynamics of Semiconductor Lasers under External Optical Feedback from Both Sides of the Laser Cavity

Photonics ◽  
2022 ◽  
Vol 9 (1) ◽  
pp. 43
Author(s):  
Mónica Far Brusatori ◽  
Nicolas Volet
Keyword(s):  
Semiconductor Lasers ◽  
Communication Systems ◽  
Optical Feedback ◽  
Low Cost ◽  
Laser Cavity ◽  
Field Testing ◽  
Error Rates ◽  
Modulation Formats ◽  
Readiness Level ◽  
Optical Isolators

To increase the spectral efficiency of coherent communication systems, lasers with ever-narrower linewidths are required as they enable higher-order modulation formats with lower bit-error rates. In particular, semiconductor lasers are a key component due to their compactness, low power consumption, and potential for mass production. In field-testing scenarios their output is coupled to a fiber, making them susceptible to external optical feedback (EOF). This has a detrimental effect on its stability, thus it is traditionally countered by employing, for example, optical isolators and angled output waveguides. In this work, EOF is explored in a novel way with the aim to reduce and stabilize the laser linewidth. EOF has been traditionally studied in the case where it is applied to only one side of the laser cavity. In contrast, this work gives a generalization to the case of feedback on both sides. It is implemented using photonic components available via generic foundry platforms, thus creating a path towards devices with high technology-readiness level. Numerical results shows an improvement in performance of the double-feedback case with respect to the single-feedback case. In particularly, by appropriately selecting the phase of the feedback from both sides, a broad stability regime is discovered. This work paves the way towards low-cost, integrated and stable narrow-linewidth integrated lasers.

scholarly journals Nonlinear Dynamics of a Single-Mode Semiconductor Laser with Long Delayed Optical Feedback: A Modern Experimental Characterization Approach

Photonics ◽  
2022 ◽  
Vol 9 (1) ◽  
pp. 47
Author(s):  
Xavier Porte ◽  
Daniel Brunner ◽  
Ingo Fischer ◽  
Miguel C. Soriano
Keyword(s):  
Semiconductor Laser ◽  
Semiconductor Lasers ◽  
Optical Feedback ◽  
Dynamical Behavior ◽  
Laser Cavity ◽  
Single Mode ◽  
Point Of View ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Delayed Optical Feedback

Semiconductor lasers can exhibit complex dynamical behavior in the presence of external perturbations. Delayed optical feedback, re-injecting part of the emitted light back into the laser cavity, in particular, can destabilize the laser’s emission. We focus on the emission properties of a semiconductor laser subject to such optical feedback, where the delay of the light re-injection is large compared to the relaxation oscillations period. We present an overview of the main dynamical features that emerge in semiconductor lasers subject to delayed optical feedback, emphasizing how to experimentally characterize these features using intensity and high-resolution optical spectra measurements. The characterization of the system requires the experimentalist to be able to simultaneously measure multiple time scales that can be up to six orders of magnitude apart, from the picosecond to the microsecond range. We highlight some experimental observations that are particularly interesting from the fundamental point of view and, moreover, provide opportunities for future photonic applications.

scholarly journals Carrierless amplitude and phase modulation in wireless visible light communication systems

2020 ◽  
Vol 378 (2169) ◽  
pp. 20190181 ◽  
Author(s):  
N. Bamiedakis ◽  
R. V. Penty ◽  
I. H. White
Keyword(s):  
Visible Light ◽  
Communication Systems ◽  
High Speed ◽  
Low Cost ◽  
Visible Light Communication ◽  
Practical Implementation ◽  
Visible Light Communications ◽  
Modulation Formats ◽  
Spectrally Efficient ◽  
Basic Features

Visible light communications (VLCs) have attracted considerable interest in recent years owing to the potential to simultaneously achieve data transmission and illumination using low-cost light-emitting diodes (LEDs). However, the high-speed capability of such links is typically limited by the low bandwidth of LEDs. As a result, spectrally efficient advanced modulation formats have been considered for use in VLC links in order to mitigate this issue and enable higher data rates. Carrierless amplitude and phase (CAP) modulation is one such spectrally efficient scheme that has attracted significant interest in recent years owing to its good potential and practical implementation. In this paper, we introduce the basic features of CAP modulation and review its use in the context of indoor VLC systems. We describe some of its attributes and inherent limitations, present related advances aiming to improve its performance and potential and report on recent experimental demonstrations of LED-based VLC links employing CAP modulation. This article is part of the theme issue ‘Optical wireless communication’.

Lightguide Technology Review and Status

1983 ◽  
Vol 24 ◽  
Author(s):  
M. A. Safi
Keyword(s):  
Semiconductor Lasers ◽  
Optical Fibers ◽  
Communication Systems ◽  
Low Cost ◽  
Production Capacity ◽  
The Past ◽  
Complex Information ◽  
Processing And Storage ◽  
Voice Data ◽  
Rapid Deployment

Remarkable progress has been made in the lightguide technology over the past ten years. The realization of low loss optical fibers approaching intrinsic material limit and long life semiconductor lasers has stimulated rapid deployment of lightwave communication systems. Within the past five years the world wide fiber production capacity has grown from a few thousand to over one million kilometers per year. The impetus for this phenomenal growth can also be traced to recent advances in computer technology allowing low cost processing and storage of a great deal of complex information. This combination of information processing and transmission technologies is bringing a host of new services such as voice, data and visual communications, CATV, videotex and facsimile transmission, over the same network. One could therefore expect an accelerating growth in deployment of lightwave communication systems.

Noise characteristics in line-narrowed semiconductor lasers with optical feedback

1981 ◽  
Vol 17 (19) ◽  
pp. 677 ◽  
Author(s):  
L. Goldberg ◽  
A. Dandridge ◽  
R.O. Miles ◽  
T.G. Giallorenzi ◽  
J.F. Weller
Keyword(s):  
Semiconductor Lasers ◽  
Optical Feedback ◽  
Noise Characteristics

Analysis of DFB semiconductor lasers with external optical feedback

1988 ◽  
Vol 24 (9) ◽  
pp. 509 ◽  
Author(s):  
J.L. Beylat ◽  
J. Jacquet
Keyword(s):  
Semiconductor Lasers ◽  
Optical Feedback

scholarly journals Physical-Layer Security Improvement with Reconfigurable Intelligent Surfaces for 6G Wireless Communication Systems

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1439
Author(s):  
Janghyuk Youn ◽  
Woong Son ◽  
Bang Chul Jung
Keyword(s):  
Wireless Communication ◽  
Physical Layer Security ◽  
Communication Systems ◽  
Low Cost ◽  
Physical Layer ◽  
Base Station ◽  
Wireless Communication Systems ◽  
Secrecy Rate ◽  
Pilot Signal ◽  
Time Division

Recently, reconfigurable intelligent surfaces (RISs) have received much interest from both academia and industry due to their flexibility and cost-effectiveness in adjusting the phase and amplitude of wireless signals with low-cost passive reflecting elements. In particular, many RIS-aided techniques have been proposed to improve both data rate and energy efficiency for 6G wireless communication systems. In this paper, we propose a novel RIS-based channel randomization (RCR) technique for improving physical-layer security (PLS) for a time-division duplex (TDD) downlink cellular wire-tap network which consists of a single base station (BS) with multiple antennas, multiple legitimate pieces of user equipment (UE), multiple eavesdroppers (EVEs), and multiple RISs. We assume that only a line-of-sight (LOS) channel exists among the BS, the RISs, and the UE due to propagation characteristics of tera-hertz (THz) spectrum bands that may be used in 6G wireless communication systems. In the proposed technique, each RIS first pseudo-randomly generates multiple reflection matrices and utilizes them for both pilot signal duration (PSD) in uplink and data transmission duration (DTD) in downlink. Then, the BS estimates wireless channels of UE with reflection matrices of all RISs and selects the UE that has the best secrecy rate for each reflection matrix generated. It is shown herein that the proposed technique outperforms the conventional techniques in terms of achievable secrecy rates.

scholarly journals A 300-GHz low-cost high-gain fully metallic Fabry–Perot cavity antenna for 6G terahertz wireless communications

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Basem Aqlan ◽  
Mohamed Himdi ◽  
Hamsakutty Vettikalladi ◽  
Laurent Le-Coq
Keyword(s):  
Communication Systems ◽  
Low Cost ◽  
Frequency Selective Surface ◽  
High Gain ◽  
Wireless Communication Systems ◽  
Beam Radiation ◽  
Compact Size ◽  
Fabry Perot ◽  
Operating Bandwidth ◽  
Polarization Level

AbstractA low-cost, compact, and high gain Fabry–Perot cavity (FPC) antenna which operates at 300 GHz is presented. The antenna is fabricated using laser-cutting brass technology. The proposed antenna consists of seven metallic layers; a ground layer, an integrated stepped horn element (three-layers), a coupling layer, a cavity layer, and an aperture-frequency selective surface (FSS) layer. The proposed aperture-FSS function acts as a partially reflective surface, contributing to a directive beam radiation. For verification, the proposed sub-terahertz (THz) FPC antenna prototype was developed, fabricated, and measured. The proposed antenna has a measured reflection coefficient below − 10 dB from 282 to 304 GHz with a bandwidth of 22 GHz. The maximum measured gain observed is 17.7 dBi at 289 GHz, and the gain is higher than 14.4 dBi from 285 to 310 GHz. The measured radiation pattern shows a highly directive pattern with a cross-polarization level below − 25 dB over the whole band in all cut planes, which confirms with the simulation results. The proposed antenna has a compact size, low fabrication cost, high gain, and wide operating bandwidth. The total height of the antenna is 1.24 $${\lambda }_{0}$$ λ 0 ($${\lambda }_{0}$$ λ 0 at the design frequency, 300 GHz) , with a size of 2.6 mm × 2.6 mm. The proposed sub-THz waveguide-fed FPC antenna is suitable for 6G wireless communication systems.

scholarly journals New Compact Wearable Metamaterials Circular Patch Antennas for IoT, Medical and 5G Applications

2020 ◽  
Vol 3 (4) ◽  
pp. 42
Author(s):  
Albert Sabban
Keyword(s):  
Communication Systems ◽  
Dynamic Range ◽  
Low Cost ◽  
Patch Antennas ◽  
Antenna Feed ◽  
Circular Patch ◽  
Wearable Antenna ◽  
Wearable Antennas ◽  
Feed Network ◽  
Line Design

The development of compact passive and active wearable circular patch metamaterials antennas for communication, Internet of Things (IoT) and biomedical systems is presented in this paper. Development of compact efficient low-cost wearable antennas are one of the most significant challenges in development of wearable communication, IoT and medical systems. Moreover, the advantage of an integrated compact low-cost feed network is attained by integrating the antenna feed network with the antennas on the same printed board. The efficiency of communication systems may be increased by using efficient passive and active antennas. The system dynamic range may be improved by connecting amplifiers to the printed antenna feed line. Design, design considerations, computed and measured results of wearable circular patch meta-materials antennas with high efficiency for 5G, IoT and biomedical applications are presented in this paper. The circular patch antennas electrical parameters on the human body were analyzed by using commercial full-wave software. The circular patch metamaterial wearable antennas are compact and flexible. The directivity and gain of the antennas with Circular Split-Ring Resonators (CSRR) is higher by 2.5dB to 3dB than the antennas without CSRR. The resonant frequency of the antennas without CSRR is higher by 6% to 9% than the antennas with CSRR. The computed and measured bandwidth of the stacked circular patch wearable antenna with CSRR for IoT and medical applications is around 12%, for S11 lover than −6dB. The gain of the circular patch wearable antenna with CSRR is around 8dBi.

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