Abstract
We propose a time division multiplexing passive optical network (TDM-PON) monitoring scheme based on the optical pulse width modulation (OPWM) by using a simple asymmetric loop (AL) located near the optical network unit (ONU). Various pulse widths can be easily obtained by configuring the appropriate length of the patchcord used to generate the path difference between two branches of a 1 × 2 splitter. Different wavelengths can be assigned to the same pulse width, which can further increase the network size. The optimized parameters of the AL are investigated and analysis models are established. The calculation results show that the proposed scheme has smaller correlation distance (CD) and lower multiple-customers interference probability (MCIP) than the periodic coding (PC) scheme. A simplified PON system with 8 ONUs is set up to experimentally demonstrate the feasibility of the proposed scheme. The network recognition processing used to identify the reflected monitoring signals in the proposed scheme is simple, especially compared with the reduced complexity maximum likelihood sequence estimation (RC-MLSE) used in the typical PC scheme.
Highlights
Passive optical network (PON) will play key role in alleviating the last mile bottleneck for the generation broadband optical access networks[1,2,3]
It is important for network operators to identify and fix the failure in the feeder fiber (FF) or drop fibers (DFs) timely in order to ensure the high quality of service (QoS)[7,8,9]
We have proposed and experimentally demonstrated optical pulse width modulation (OPWM) in the optical domain by using the asymmetric loop (AL) for time division multiplexing PON (TDM-PON) monitoring
Summary
Where c is the speed of light in the vacuum, ng is the effective group index in the fiber core. Only at the maximum broadening ratio, the flatness of the composite pulse waveforms can be satisfied with r = 50% and Ri = 66.7%. Note that the flatness of the composite pulse waveforms in the proposed scheme has no effect on the recognition processing, as the rising and falling edge of the first and last subpulse contributes to that. When Ri is fixed to 100%, the incident pulse can be divided into two parts respectively reflected by the FBG. It seems to have the same expression of 0 < Ri < 100% in Equation (1). If we take the same expression for two different Ri, the patchcord length li must be distinguished, otherwise the maximum broadening ratio for Ri = 100% may be 3 when li is equal to cTs/ng. Considering the bigger broadening ratio, we mainly focus on the case of 0 < Ri < 100% in the later discussion
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