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The work clarified directly measured modulated laser with dual drive measured Mach–Zehnder modulators for signal strength in free space optics (FSO) channel. Peak power after free space communication channel at various propagation distances is measured in the optical time domain. As well as the signal level amplitude quality and data error rates after light detector at various propagation distances are also measured in the time bit period. The directly measured modulated laser with dual drive measured Mach–Zehnder modulators for signal strength in FSO communication channels is stimulated with optisystem program version 13. Peak signal power after free space communication channel at various propagation distances is measured in the optical time domain. The optimum peak signal power is achieved at 10 km distance with a value of 4.328 W. The signal level amplitude quality and data error rates after light detector at various propagation distances are also measured in the time bit period. The optimum Q level and BER level are clarified at 10 km distance with the values of 23.1164 for signal quality and 1.439 × 10 for minimum data error rates.

In this paper, a scheme for generating high-quality tunable microwave-frequency combs (MFCs) is proposed. The proposed scheme is based on an initially non-flat MFC generated by a directly modulated laser operating in gain-switching status. Filtering operations are used to increase the flatness of the MFC. Concretely, by employing an optical bandpass filter and a two-tap negative-coefficient microwave photonic filter, the flatness of the MFC is significantly optimized. In the experiment, MFCs with adjustable comb spacing from 0.5 GHz to 1.6 GHz and bandwidths ranging from 0 to 26.5 GHz are generated. The flatness is better than ±2.5 dB for the MFC. The proposed scheme provides a simple, efficient, and high-performance solution for generating MFCs, making it a promising candidate for various applications requiring high-quality MFC sources.

60 Gbits over 2 m, 50 Gbits over 50 m and 40 Gbits was transmitted over 100 m of OM4 multimode fibre using four-level pulse amplitude modulation and a directly modulated 850 nm vertical cavity surface emitting laser (VCSEL).

The 25 Gbaud/s 4-level pulse amplitude modulation (4-PAM) of a 1.3 μm electroabsorption modulator integrated with a distributed feedback (DFB) laser is demonstrated for the first time. The linearities of the electroabsorption DFB (EADFB) laser and the directly modulated laser are evaluated to investigate the applicability of the PAM format to these devices.

In this paper, we present a directly modulated laser (DML) using a partially corrugated grating (PCG) and integrated with a semiconductor optical amplifier (SOA). The influence of the quasi-high-pass filter properties of the SOA on the bandwidth was explored, resulting in high optical power output at lower current levels, with a bandwidth surpassing 25 GHz and an output power above 25 mW. The PCG design boosts the lasing mode’s resistance to random phase fluctuations at the rear facet, hence boosting the mode stability of the laser with a side-mode suppression ratio (SMSR) of over 44 dB. Furthermore, we performed back-to-back (BTB) 26.5625 Gbps NRZ data transmission experiments at room temperature (25 °C) with a modulation current of 60 mA. The results reveal that the transmitter and dispersion eye closure (TDEC) of the fabricated DML is lower than that of a conventional laser when the SOA area current reaches a specific threshold, demonstrating the enhanced signal transmission capabilities of our design. This laser structure offers a fresh strategy for the development of high-power, high-speed DMLs.

This paper proposes an innovative light-fidelity (Li-Fi) system for high-speed communication in hospital environments that operates at a green wavelength of 500 nm with Directly Modulated Laser (DML). The proposed system shows an excellent performance and achieves a Q factor of 18.84, a bit error rate (BER) of 1.6e-79, and a signal-to noise ratio (SNR) of 74.94 dB, which is significantly better than the previous research. It also has a range of up to 25 m line-of-sight (LOS) and can transfer data at speeds in excess of 1 Gbps, making it significantly faster than previous work conducted with much lower LOS ranges while being robust against interference. New applications of DML combined with optical splitters contribute to providing signal stability and system scalability, overcoming problems such as low range. This design ensures safe, reliable, and non-intrusive communication, ideal for applications that require high data reliability, such as real-time imaging and telemedicine in hospitals. This new Li-Fi system is found to be compatible with modern hospital power requirements, and it also provides a solid foundation for future 6G communication networks.

The first 25 Gbaud/s four-level pulse amplitude modulation (PAM) of a 1.3 μm directly modulated laser (DML) is achieved and a 10 km transmission over a single-mode fibre (SMF) with clear eye openings is demonstrated.

Near-future upgrades of intra data center networks and high-performance computing systems would require optical interconnects capable of operating at beyond 100 Gbps/lane. In order for this evolution to be achieved in a sustainable way, high-speed yet energy-efficient transceivers are in need. Towards this direction we have previously demonstrated directly-modulated lasers (DMLs) capable of operating at 50 Gbps/lane with sub-pJ/bit efficiencies based on our novel membrane-III-V-on-Si technology. However, there exists an inherent tradeoff between modulation speed and power consumption due to the carrier-photon dynamics in DMLs. In this work, we alleviate this tradeoff by introducing photon–photon resonance dynamics in our energy-efficient membrane DMLs-on-Si design and demonstrate a device with a maximum 3-dB bandwidth of 47.5 GHz. This denotes a bandwidth increase of more than 2x times compared to our previous membrane DMLs-on-Si. Moreover, the DML is capable of delivering 60-GBaud PAM-4 signals under Ethernet’s KP4-FEC threshold (net data rate of 113.42 Gbps) over 2-km of standard single-mode fiber transmission. DC energy-efficiencies of 0.17 pJ/bit at 25 °C and 0.34 pJ/bit at 50 °C have been achieved for the > 100-Gbps signals. Deploying such DMLs in an integrated multichannel transceiver should ensure a smooth evolution towards Terabit-class Ethernet links and on-board optics subsystems.

Dynamic characteristics of directly modulated laser are investigated by simulating the single mode laser rate equations, emphasized on the effect of the gain compression for the two laser models: one adiabatic chirp dominated and another with a combination of adiabatic and transient chirp-dominated laser. The influence of laser adiabatic and transient chirp on system performance in normal and anomalous propagation regime is investigated by simulation. It is shown that in the anomalous propagation regime, the presence of fiber nonlinearity can be beneficial, improving the system performance by opening the eye diagram at system output. Contrarily, in the normal propagation regime, presence of high gain compression coefficient (ε > 4 × 10 cm ) can strongly degrade the system performance by closing the eye diagram at system output. Finally, it is shown that the laser model with a combination of adiabatic and transient chirp with anomalous dispersion coefficient shows much better result in the saturated regime. This can be used to extend the transmission distance in optical communication.

In this paper, for the first time transmission of 2.5 Gb/s duobinary signal is investigated for the downlink direction in 40 GHz optical millimeter-wave generation or up-conversion, utilizing a dual-arm Mach–Zehnder modulator based on different modulation schemes, namely double- and single-sideband (DSB and SSB) and optical carrier suppression (OCS). The up-converted optical millimeter-wave employing OCS modulation scheme indicates the highest back-to-back received optical power and the smallest power penalty after long propagation in the single-mode fiber, in comparison to DSB and SSB. Directly modulated laser in association with OCS modulation scheme has been used to generate duobinary optical millimeter-wave signal in order to minimize the cost and complexity of the system.