# Evaluation of Performance Enhancement of Optical Multi-Level Modulation Based on Direct Modulation of Optically Injection-Locked Semiconductor Lasers

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## Abstract

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## 1. Introduction

## 2. Principle and Theoretical Model

## 3. Simulation and Result

## 4. Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 1.**Schematic for the generation of the multi-level (M-level) amplitude shift keying (ASK) optical signals based on the optically injection-locked (OIL) semiconductor lasers.

**Figure 2.**Eye patterns of the free-running lasers. (

**a**) 2-level amplitude-shift keying (ASK) signal at 1-Gbaud data modulation. (

**b**) 4-level ASK signal at 1-Gbaud data modulation. (

**c**) 8-level ASK signal at 1-Gbaud data modulation. (

**d**) 2-level ASK signal at 5-Gbaud data modulation. (

**e**) 4-level ASK signal at 5-Gbaud data modulation. (

**f**) 8-level ASK signal at 5-Gbaud data modulation.

**Figure 3.**Eye pattern of the OIL semiconductor lasers. (

**a**) 2-level amplitude-shift keying (ASK) signal at 1-Gbaud data modulation. (

**b**) 4-level ASK signal at 1-Gbaud data modulation. (

**c**) 8-level ASK signal at 1-Gbaud data modulation. (

**d**) 2-level ASK signal at 5-Gbaud data modulation. (

**e**) 4-level ASK signal at 5-Gbaud data modulation. (

**f**) 8-level ASK signal at 5-Gbaud data modulation.

**Figure 4.**Averaged Q-factors of the free-running and the OIL semiconductor lasers as a function of various M-levels for 10-Gbaud and 20-Gbaud modulation. Q-factor: quality-factor; M-level: multi-level; OIL: optically injection locked.

**Figure 5.**Averaged Q-factors of the free-running and the OIL semiconductor lasers as a function of various data rates for 2 and 4-level ASK signals. Q-factor: quality-factor; ASK: amplitude-shift keying; OIL: optically injection-locked.

**Figure 6.**Q-factor dependence on the injection-locking parameters for two-level ASK signals at 10-Gbaud data modulation. The locking range is represented as a gray-scaled range that shows the Q-factor value. Q-factor: quality-factor; n.s.: unstable locking range.

Symbol | Quantity | Value | Unit |
---|---|---|---|

${\lambda}_{0}$ | Wavelength | $1550$ | nm |

$g$ | Net stimulated gain | $4.7\times {10}^{4}$ | $1/\mathrm{s}$ |

${N}_{tr}$ | Transparency carrier number | $9.36\times {10}^{6}$ | No unit |

${J}_{th}$ | Threshold current | $2\times {10}^{16}$ | $1/\mathrm{s}$ |

${J}_{bias}$ | Bias current | $5\times {J}_{th}$ | $1/\mathrm{s}$ |

${\gamma}_{p}$ | Photon decay rate | $5\times {10}^{11}$ | $1/\mathrm{s}$ |

${\gamma}_{n}$ | Carrier decay rate | $1\times {10}^{9}$ | $1/\mathrm{s}$ |

$\alpha $ | Linewidth enhancement factor | $5$ | No unit |

$\kappa $ | Coupling ratio | $225$ | $1/\mathrm{s}$ |

${R}_{inj}$ | Injection power ratio | $10$ | dB |

$\Delta {\omega}_{inj}$ | Detuning frequency | $-10$ | GHz |

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**MDPI and ACS Style**

Jeong, H.-S.; Cho, J.-H.; Sung, H.-K.
Evaluation of Performance Enhancement of Optical Multi-Level Modulation Based on Direct Modulation of Optically Injection-Locked Semiconductor Lasers. *Photonics* **2021**, *8*, 130.
https://doi.org/10.3390/photonics8040130

**AMA Style**

Jeong H-S, Cho J-H, Sung H-K.
Evaluation of Performance Enhancement of Optical Multi-Level Modulation Based on Direct Modulation of Optically Injection-Locked Semiconductor Lasers. *Photonics*. 2021; 8(4):130.
https://doi.org/10.3390/photonics8040130

**Chicago/Turabian Style**

Jeong, Hyo-Sang, Jun-Hyung Cho, and Hyuk-Kee Sung.
2021. "Evaluation of Performance Enhancement of Optical Multi-Level Modulation Based on Direct Modulation of Optically Injection-Locked Semiconductor Lasers" *Photonics* 8, no. 4: 130.
https://doi.org/10.3390/photonics8040130