The Coherent Detection And Reconfigurable Spectral Conversion Research In OFDM-PON

Optical orthogonal frequency division multiplexing(O-OFDM)has attracted considerable attentions due to its many merits such as high spectral efficiency(SE),strong tolerance to chromatic dispersion(CD),polarization mode dispersion(PMD),and excellent scalability to higher level modulation formats.The OFDM passive optical network(OFDM-PON)has become an important alternative of NG-PON2,because OFDM-PON inherits the advantages of O-OFDM technology and provides a variety of business for users with high flexibility and low cost.This dissertation focuses on the analyses and investigations of OFDM-PON in coherent detection and spectral conversion.Meanwhile,the corresponding designs and solutions for several key issues encountered by the above-mentioned optical communication technology are proposed,simulated and experimentally demonstrated.The mainly innovative work contents are summarized as follows:1.This paper proposes a down conversion combines PA-BPS to reduce phase noise for CO-OFDM systems.Two near optical tones transmit through the same channel and utilized as the optical user signals and local optical signals of coherent detection.Meanwhile,the radio frequency carrier after heterodyne detection is utilized to compensate the phase noise and amplify baseband OFDM signal at the same time.Experimental results show that,based on the method,a receiver sensitivity as low as-27dBm can be achieved in the transmission systems considered in the paper.Meanwhile,in each PA-BPS calculation,the method only requires 2 pilots and 10 testing phases.By compared with the direct detection scheme under the same optical fiber channel,this proposed scheme can improve 18dB power budget.2.The paper proposes a phase noise cancelling(PNC)homodyne detection scheme based on RSOA.In order to guarantee the ONU is colorless,RSOA is a better solution to provide colorless light source.Meanwhile RSOA is a kind of low cost intensity modulator,therefore,coherent detection cannot need consider phase information extraction for signal demodulation.This paper proposes a simple mathematical operation to cancel phase noise.Meanwhile,experimental results show that,relative to PNC-free coherent detection scheme and direct detection scheme,PNC scheme can 4 dB and 15 dB power budget.3.This paper describes a research to uplink physical capacity of OFDM-PON where RSOAs are used in ONUs as the colorless resources.Based on a coherent narrowband integral model of RSOA,theoretic and experimental investigations are taken to the static optical gain,the dynamic electro-optical modulation behavior and the frequency chirp characteristic.It is proven that the RSOA's frequency response is in low-pass type with a 3dB cut-off frequency related to the bias current and injected optical power.Taking advantage of RSOA's optical frequency chirp,a blue-shifted optical band-pass filter seriesly connected to RSOA can expand the system bandwidth from 1.2 GHz up to 1.8 GHz.Furthermore,by the adaptive bit loading to OFDM sub-carriers the data capacity in one RSOA-based uplink is experimentally demonstrated to reach 4 Gb/s and above.4.This paper presents a reconfigurable and transparency spectral conversion based on the DD-MZM.The scheme can convert the OFDM-PON densely centralized light sources with dynamic,transparent and reconfigurable allocation.By analyzing mathematical model and computer simulation,the optimal conditions are demonstrated to ensure the converter has optimal performance,in terms of the converted components have the highest conversion efficiency,the number of parasitic components are minimal as well as the system BER performance is optimal.Experiments verify the feasibility of the scheme and demonstrate the conversion is almost waveform distortionless,the conversion process can be centralized controlled through SDN,as well as the impact of MZM extinction ratio on conversion performance can be neglected.5.Based on the DD-MZM spectral conversion,a novel spectral conversion scheme based on DP-MZM is proposed.The scheme inherits the DD-MZM spectral conversion advantages including high transparency,SDN-controllable reconfigurable and,more importantly,the scheme on the parasitic components suppression ability better than DD-MZM converter.Through theoretical and simulation analysis,this paper also demonstrates the correctness of optimal conditions,moreover,experiments verify the feasibility,practicality and robustness of the converter.