# Performance Evaluation of Highly Nonlinear Fiber (HNLF) Based Optical Phase Conjugation (OPC) in Long Haul Transmission of 640 Gbps 16-QAM CO-OFDM

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Experiment Setup

## 3. Optical Phase Conjunction (OPC) Parametric Optimization

## 4. Performance Evaluation

^{−4}and conversion efficiency of −22 dB. In contrast, the mid-link OPC with 800 m HNLF D has Q-factor gain of 8.9 dB, BER of 2.7 × 10

^{−3}, and conversion efficiency of −22.6 dB. This can be explained by Equation (4), that the power spectrum of OPC, denoted as ${P}_{OPC}$, is in direct proportion to the term ${(\gamma L)}^{2}$ [2].

## 5. Conclusions

^{−4}, which has the Q-factor improvement of 3 dB and nearly two orders magnitude improvement in BER comparing to the case of no OPC. The evaluation methodology presented in this paper provides useful information for OPC design.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**A diagram of 16-QAM coherent-optical orthogonal frequency-division multiplexing (CO-OFDM) transmission with mid-link optical phase conjunction (OPC) compensation.

**Figure 2.**Measured conversion efficiency in square symbol line and bit error rates (BERs) in triangle symbol line versus the signal power input into OPC. (

**a**) HNLF A; (

**b**) HNLF B; (

**c**) HNLF C; (

**d**) HNLF D.

**Figure 3.**Measured conversion efficiency in square symbol line and BERs in triangle symbol line versus the pump signal power input into OPC. (

**a**) HNLF A; (

**b**) HNLF B; (

**c**) HNLF C; (

**d**) HNLF D.

**Figure 5.**Received 16-QAM signal constellation diagram after 800 km transmission: (

**a**) Dispersion compensation using dispersion compensated fiber (DCF); (

**b**) mid-link OPC using 550 m HNLF A; (

**c**) mid-link OPC using 500 m HNLF B; (

**d**) mid-link OPC using 750 m HNLF C; (

**e**) mid-link OPC using 800 m HNLF D.

**Figure 6.**A comparison of Q-factor gains versus optical signal-to-noise ratio (OSNR) after 800 km transmission.

Parameters | Value |
---|---|

Bit rate | 640 Gbps |

Maximum possible sub-carriers | 128 |

Number of sub-carriers | 80 |

Number of prefix points | 10 |

Number of training symbols | 10 |

Number of pilot symbols | 6 |

HNLF | A | B | C | D |
---|---|---|---|---|

${\lambda}_{0}[\mathrm{n}\mathrm{m}]$ | 1541.3 | 1546.7 | 1542.9 | 1545.4 |

${S}_{0}[\mathrm{p}\mathrm{s}/\mathrm{n}{\mathrm{m}}^{2}\mathrm{k}\mathrm{m}]$ | 0.0074 | 0.017 | 0.072 | 0.07 |

$\alpha [\mathrm{d}\mathrm{B}/\mathrm{k}\mathrm{m}]$ | 0.76 | 0.74 | 0.83 | 0.47 |

${n}_{2}[{\mathrm{m}}^{2}/\mathrm{W}]$ | 30.467 | 31.989 | 27.392 | 18.951 |

$\gamma [{\mathrm{W}}^{-1}/\mathrm{k}{\mathrm{m}}^{-1}]$ | 10.8 | 11.3 | 9.7 | 6.7 |

Parameters | BER | Q [dB] | CE [dB] |
---|---|---|---|

Without compensation | 1.5 $\times {10}^{-2}$ | 6.8 | - |

With dispersion compensation fiber | 1 $\times {10}^{-2}$ | 7.2 | - |

with mid-link OPC using 550 m HNLF A | 6.1 $\times {10}^{-4}$ | 9.8 | −22 |

with mid-link OPC using 500 m HNLF B | 1.6 $\times {10}^{-3}$ | 9.4 | −22.4 |

with mid-link OPC using 750 m HNLF C | 1.3 $\times {10}^{-3}$ | 9.5 | −20.6 |

with mid-link OPC using 800 m HNLF D | 2.7 $\times {10}^{-3}$ | 8.9 | −22.6 |

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**MDPI and ACS Style**

Wang, J.; Du, Y.; Liang, C.; Li, Z.; Fang, J.
Performance Evaluation of Highly Nonlinear Fiber (HNLF) Based Optical Phase Conjugation (OPC) in Long Haul Transmission of 640 Gbps 16-QAM CO-OFDM. *Photonics* **2021**, *8*, 45.
https://doi.org/10.3390/photonics8020045

**AMA Style**

Wang J, Du Y, Liang C, Li Z, Fang J.
Performance Evaluation of Highly Nonlinear Fiber (HNLF) Based Optical Phase Conjugation (OPC) in Long Haul Transmission of 640 Gbps 16-QAM CO-OFDM. *Photonics*. 2021; 8(2):45.
https://doi.org/10.3390/photonics8020045

**Chicago/Turabian Style**

Wang, Jingjing, Yongtao Du, Chunhao Liang, Zhong Li, and Jing Fang.
2021. "Performance Evaluation of Highly Nonlinear Fiber (HNLF) Based Optical Phase Conjugation (OPC) in Long Haul Transmission of 640 Gbps 16-QAM CO-OFDM" *Photonics* 8, no. 2: 45.
https://doi.org/10.3390/photonics8020045