Research On High-speed Optical Fiber Transmission System For Metropolitan Data Center Interconnections

The development of communication technology drives the emergence of emerging technologies such as cloud computing,Internet of cars and Internet of things,and virtual reality.Data traffic generated by emerging services is growing at an exponential rate every year,posing a great challenge to existing network capacity and communication equipments.Optical fiber communication has natural characteristics of low cost,large bandwidth and capacity,it is the main supporter of high-speed information transmission system and the cornerstone of rapidly developed modern information technology,its application subject has moved from the central offices of telecom operators into data centers.The future development and construction of data centers need to meet the needs of low energy consumption and super large-scale data processing.From the perspective of optical interconnection application of data center,the low cost and low power consumption characteristics of intensity modulation and direct-detection(IM/DD)system make optical interconnection between large-scale and high-speed data centers possible.This dissertation has carried out a series of researches on high-speed optical transmission system between metropolitan data center interconnections based on IM/DD system.It is committed to realize the high-speed optical transmission system with low cost,low power consumption and large capacity for optical interconnection between data centers.The main work and innovations of this dissertation are as follows.1.Research on optical SSB transmission technology based on DDMZMTo overcome the fiber dispersion introduced prequency selective power fading in optical double side-band transmission system,the optical single side-band(SSB)transmission system based on dual-drive Mach-Zehnder modulator(DDMZM)is established.Phase rotation and Hilbert superposition cancellation(HSC)structure are proposed for first-order linear interference elimination.Based on the HSC structure,a modified single-stage linear filter is also proposed to eliminate DD introduced signal-tosignal beating interference(SSBI).By building up an experimental platform,combining with the proposed interference cancellation scheme,the transmission of 25 Gbit/s fourlevel pulse amplitude modulation(PAM-4)signal over 300 km standard single-mode fiber(SSMF)is realized.The feasibility of optical SSB transmission system based on DDMZM in optical interconnection between metropolitan data centers is verified.2.Research on equalization algorithm for optical SSB transmission systemIn optical SSB transmission system with IM/DD,the correlation between adjacent symbols of the signal will be enhanced after fiber transmission,and the influence of SSBI will be aggravated.An enhanced hybrid equalizer based on forward feedback equalizer and Volterra filter(VF)is proposed to eliminate the linear and nonlinear interference between the adjacent symbols.The proposed enhanced hybrid equalizer not only reduces the computational complexity of the receiver,but also ensures the high performance of the system.It is verified by experiments that 102.4 Gbit/s PAM-4 signal is transmitted over 240 km SSMF with the proposed hybrid equalizer.3.Research on metropolitan optical transmission system based on DD-KK receiverA metropolitan optical transmission system based on Kramers-Kronig(KK)receiver is studied.A simplified DD-KK receiver based on digital virtual carrier insertion is proposed to restore the phase of SSB signal for SSBI mitigation.With the proposed simplified DD-KK receiver,102.4 Gbit/s optican SSB PAM-4 signal is transmitted over800 km SSMF via experimental demonstration.Meanwhile,the dispersion compensation with KK receiver is analyzed,the interaction of dispersion compensation function,laser linewidth and fiber dispersion will produce equalization-enhanced phase noise(EEPN).Laser linewidth and fiber dispersion also will generate phase to amplitude(P2A)noise after square-law detection.The effects of EEPN and P2 A noise under dispersion pre-and post-compensation are studied theoretically.It has a guiding significance on the study of the laser linewidth requirement in IM/DD system.4.Research on offset carrier PDM-Twin-SSB metro optical transmission ssystemFinally,the large capacity optical transmission system based on multi-dimension multiplexing is studied to realize 400 G dater center interconnection application.A polarization division multiplexing(PDM)Twin-SSB transmission system with offset carrier is proposed,and a simplified multiple input multiple output(MIMO)VF algorithm is also proposed to eliminate the polarization and sideband crosstalk.409.6 Gbit/s PAM-4 signal is transmitted over 80 km single-mode fiber by building an experimental platform,and the proposed simplified MIMO-VF reduces 57.9% computational complexity,which verifies the effectiveness of the proposed transmission system and simplified algorithm.