상세정보

In recent years, data traffic has increased dramatically due to high bandwidth applications such as multimedia streaming, internet protocol television (IPTV), 4G and 5G wireless service. Therefore, the next generation optical access networks demand high-speed data rates over 10 Gb/s. But high speed optical signals are very vulnerable to chromatic dispersion. Therefore, transmission of high-speed optical signal over single-mode fiber suffers from signal distortion by the chromatic dispersion.

In this dissertation, we investigate the mitigation of dispersion impairment in high-speed optical access network through theorectical analysis and experimental demonstration. 

We present a method for transmitting high speed (over 10 Gb/s) optical nonreturn-to-zero signals at a wavelength of 1550 nm without any dispersion compensation methods. We propose optimized self-phase modulation by varying parameters of the fiber launching power and the extinction ratio of optical non-return to zero signals to overcome severe signal distortions by the chromatic dispersion effect. Using the optimization of the self-phase modulation effect, we were able to transmit 10 Gb/s optical nonreturn-to-zero signals over 200 km single mode fiber and 25 Gb/s optical nonreturn-to-zero signals over 40-km single-mode fiber, which can be applicable to passive optical networks with a single wavelength channel and a high split ratio. We demonstrated that the self-phase modulation effect can be controlled by the extinction ratio and the fiber launching power.

Also, A method for a 1550 nm vertical cavity surface emitting laser (VCSEL)-based 10 Gb/s optical non-return to zero (NRZ) signal transmission over 20 km single mode fiber (SMF) using reflective semiconductor optical laser amplifier (RSOA) gain saturation is presented. The optical signal distortion of 10 Gb/s optical NRZ signals caused by the inherent frequency chirp of the VCSEL and the chromatic dispersion of SMF were investigated through numerical simulations and experiments. For 20 km transmission over SMF, VCSEL-based 10 Gb/s optical NRZ signals were severely distorted and ‘1’ bit signals had different amplitudes with respect to their bit patterns. The gain saturation of RSOA can equalize the different amplitudes of ‘1’ bit signals and can mitigate the optical pulse distortion after 20 km transmission over SMF. The experimental results showed that VCSEL-based 10 Gb/s optical NRZ signals can achieve a bit error rate (BER) of 10^-9 with a 2.4 dB dispersion penalty for 20 km transmission of SMF with RSOA gain saturation.

Abstract
Contents i
List of Figures iv
List of Table vii
1 Introduction 1
2 Optical access network systems 4
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Evolution of optical communication system . . . . . . . . . . . . . . . 5
2.3 Type of optical access network . . . . . . . . . . . . . . . . . . . . . . 8
2.3.1 Passive optical network . . . . . . . . . . . . . . . . . . . . . . 8
2.3.2 Ethernet PON . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.3.3 Wavelength division multiplexing PON . . . . . . . . . . . . . . 12
2.3.4 Application for PON . . . . . . . . . . . . . . . . . . . . . . . . 13
2.4 Components of optical access network . . . . . . . . . . . . . . . . . . 14
2.4.1 Optical transmitter . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.4.2 Optical fiber . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.4.3 Optical receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.5 summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3 Mitigation of dispersion impairment using self-phase modulation effect 28
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.2 Theoretical fundamentals of self-phase modulation . . . . . . . . . . . 31
3.2.1 Nonlinear pulse propagation . . . . . . . . . . . . . . . . . . . . 31
3.2.2 Self-phase modulation effect with respect to the extinction ratio 34
3.3 Verification of mitigation of dispersion using SPM effect . . . . . . . . 36
3.3.1 10 Gb/s optical NRZ signal transmission over 200 km SMF . . 36
3.3.2 25 Gb/s optical NRZ signal transmission over 40 km SMF . . . 45
3.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
4 Mitigation of dispersion impairment using RSOA gain saturation 54
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
4.2 Vertical cavity surface emitting laser . . . . . . . . . . . . . . . . . . . 55
4.2.1 Structure of VCSEL . . . . . . . . . . . . . . . . . . . . . . . . 56
4.2.2 Frequency chirping of VCSEL . . . . . . . . . . . . . . . . . . . 59
4.2.3 Characteristic of VCSEL . . . . . . . . . . . . . . . . . . . . . 60
4.2.4 VCSEL-based optical communication system configuration . . 61
4.3 VCSEL-based 10 Gb/s optical NRZ signal transmission . . . . . . . . 64
4.4 20 km transmission using RSOA gain saturation . . . . . . . . . . . . 69
4.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
5 Conclusions and futureworks 75
5.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.2 Futureworks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
References 78
Acknowledgement