Determining the Stable Injection Locking of a Fabry-Pérot Laser by Observing the RF Spectral Components Generated by a Low-Reflectivity External Cavity

A novel approach to monitoring the laser injection-locking (IL) state is proposed and verified using the side-mode suppression ratio (SMSR). In a photonics experiment for laser IL, an optical spectrum analyzer with the conventional criterion of a 35-dB SMSR is conventionally used to detect the locking state of a Fabry–Pérot (FP) laser with multiple longitudinal modes to an external master laser with one longitudinal mode. Since the 35-dB criterion is not always a sufficient locking condition, we propose a microwave-photonic technique to determine the stable-locking regime based on the observation of the radio-frequency (RF) components. A novel approach to monitoring the generated additional spectral components uses the well-known delayed-self-homodyne technique and the RF spectrum analyzer. For the novel generation of additional longitudinal groups on each FP laser’s resonator mode in the optical spectrum and consequently the overlapping RF components in the RF spectrum, an additional external resonator with low reflectivity was connected to the slave FP laser. The novel monitoring approach was experimentally verified by connecting a 1-m-long external cavity with 0.5% reflectivity and observing the optical IL phenomenon of a 1550-nm FP semiconductor laser.

A 120 Mbps WDM-based VLC system for implementation of Internet of Things

It is envisioned that by 2022, the number of Internet of Things (IoT) devices will be more than 20 billion. The transfer of information between IoT devices is heavily dependent on wireless links based on the radio frequency (RF) spectrum. Due to the scarcity of limited and licensed RF spectrum, visible light communication (VLC) based IoT links can be considered as a promising and viable solution. In this work, four channels are multiplexed to carry low-datarate information over a VLC link using cost-effective and easy to implement on-off-keying (OOK). Red, blue, green, and amber light-emitting diodes (LEDs) are deployed for parallel data transportation. The proposed system has been designed and simulated using Optisystem software. Through numerical simulations, we investigate the bit error rate (BER) performance of the proposed VLC link with increasing transmission range. Also, we investigate the BER performance of the proposed VLC link under the impact of increasing detection surface area, responsivity of the photodiode, and slope efficiency of the LEDs. Further, the performance of the proposed VLC link has been compared for different data transmission rates using non-return-to-zero and return-to-zero modulation schemes.

A Novel Spectrum Decision Pattern for The Favorable Cognitive Radio Based Internet of Things in 5G System

The Radio Frequency (RF) Spectrum decision in Cognitive Radio (CR) allows unlicensed users of wireless communication schemes to conquer the unoccupied spectrum slots as a resolution for barely spectrum. The Internet of Things (IoT) is a broad-arriving network and its object is linked by wireless communication technologies, donating cost- efficiency and generously opens to remote users. When IoT is applied, it is injured by challenges of susceptibility in the forceful surrounding situations, allotment and use of bandwidth, ease of approach and expense to buy RF spectrum. The object is permeated with cognitive capacity and is capable to model RF spectrum decisions to attain interference-release and wireless connectivity due to their Quality of Service (QoS) demands. Therefore the spectrum decision through an unlicensed user on CR influences an importance in CR-based IoT in 5G system and further network. This article depicts a systematic sustainment of the spectrum decision structure to CR Network. So, this can be mainly achieved by applying a favorable spectrum sensing technique and a novel spectrum decision framework. Presently, the wireless connectivity is intended to greater capacity, immense machine connectivity, and greater data range, low end-to-end latency, low cost and coherent Quality of Experience (QoE) condition. Hence, 4G is being substituted by 5G. Being in this 5G, the vast connectivity can be properly inspired by using the novel techniques, which is applied under the Energy detection spectrum sensing system. Also, a novel spectrum decision framework is designed for the optimum application of applying the IoT in 5G system ie., the effective use of an allocated RF spectrum is differently underutilized because of the standard handling with the licensed users are called as Primary Users (PUs).

5 THz bandwidth photonic radio frequency spectrum analyzer based on a CMOS-compatible high-index doped silica waveguide

We report an all-optical radio-frequency (RF) spectrum analyzer with a bandwidth greater than 5 terahertz (THz), based on a 50-cm long spiral waveguide in a CMOS-compatible high-index doped silica platform. By carefully mapping out the dispersion profile of the waveguides for different thicknesses, we identify the optimal design to achieve near zero dispersion in the C-band. To demonstrate the capability of the RF spectrum analyzer, we measure the optical output of a femtosecond fiber laser with an ultrafast optical RF spectrum in the terahertz regime.