Design And Application Of Burst-Mode Optical Amplifiers In Passive Optical Network

Since the beginning of this century,with the rapid development of network scale and various businesses,the number of global Internet users has been increasing with each passing year,and the bandwidth demand of users has been greatly increased.Access technology needs to realize longer transmission distance and more users,so as to cover a larger area of access.Optical access network,known as the"last kilometer",is one of the most optimal access technologies.After decades of development,Passive Optical Network(PON)has been gradually upgraded.Time and wavelength division multiplexed-passive optical network(TWDM-PON)architecture has been selected as the primary solution for the next generation passive optical network stage-2(NG-PON2)by Full Service Access Network(FSAN)group.To expand the area of access,amplifiers at Optical Line Terminal(OLT)such as erbium-doped fiber amplifiers(EDFAs)are necessary.Among all the challenges facing in the PON applications of EDFAs,upstream pre-amplification is one of the biggest issues since the fast gain transient effect of EDFA that generates burst surge at the rising edge of each frame results in serious signal performance degradation.Therefore,this paper mainly focuses on how to realize the amplification of upstream burst signal in passive optical network.In this paper,we prove that the simplest single-fiber bi-directional EDFA without isolators has the potential to be used in TWDM-PON for simultaneously downstream and upstream signal amplification.Experimental results have demonstrated that,instead of an additional light source,the downstream signal acting as saturation signal can keep the inversion of the EDF constant.As a result,with the downstream input power of-5dBm,the upstream burst surge can be effectively suppressed.Considering that the downstream input power is often higher than-5dBm,the capability of burst surge suppression can be further enhanced.For stimulated Brillouin scattering,Rayleigh backscattering(RBS)in transmission fiber,the configuration without optical isolators indeed results in amplification of these detrimental reflections therefore induces crosstalk,and error floor can be observed for high reflection cases.But considering forward error correction(FEC)will be eventually used for high-speed PONs,bit-error rate(BER)of 1×10~3 should be the judging point.In this case,the degradation of receiver sensitivity after 25-km single-mode fiber(SMF)transmission is negligible with a reflection power up to-14dBm,which can represent most of the serious reflection cases.Therefore,the proposed single-fiber bi-directional burst-mode EDFA is a good option to improve the loss budget in TWDM-PON.