Experimental demonstration of a DSP-based cross-channel interference cancellation technique for application in digital filter multiple access PONs

Abstract

A DSP-based cross-channel interference cancellation (CCIC) technique with initial condition-free, fast convergence and signal modulation format independence, is experimentally demonstrated in a two-channel point-to-point digital filter multiple access (DFMA) PON system based on intensity-modulation and direct-detection (IMDD). The CCIC-induced transmission performance improvements under various system conditions are fully investigated for the first time. It is shown that with one iteration only the CCIC technique can achieve a reduction in individual OFDM subcarrier BERs of more than 1000 times, an increase in transmission capacity by as much as 19 times and an increase in optical power budget by as much as 3.5dB. The CCIC technique thus has the potential to drastically improve the transmission performance of DFMA PONs.

Experimental demonstrations of 30Gb/s/λ digital orthogonal filtering-multiplexed multiple channel transmissions over IMDD PON systems utilizing 10G-class optical devices

“…The channel roll-off effect introduces amplitude variations between the corresponding frequency components in the upper and lower sidebands, this prevents full cancellation between the sidebands of the unwanted signal when these sidebands are mapped back in the receiver. As such, the crosschannel interference (CCI) effect occurs [14,15]. In particular, a larger system frequency response roll-off causes a greater amplitude variation between the two sidebands, thus lower frequency subcarriers suffer more CCI, leading to the utilization of low signal modulation formats on these subcarriers to obtain the acceptable bit error rate (BER) performances, as observed in Figs.…”

“…On the other hand, to improve the software-controllable network reconfigurability and network bandwidth utilization efficiency, by making use of digital orthogonal filtering (DOF) implemented with hardware-based digital signal processing (DSP), we have recently proposed and theoretically investigated a novel channel multiplexing/demultiplexing technique [12], in which centralized SDN controller-managed, software-reconfigurable digital orthogonal filters are embedded in transceivers to adaptively and dynamically combine and separate different digital signal channels according to channel spectral characteristics and network traffic status. It has been shown [12][13][14][15] that the proposed DOF-based multiplexing/demultiplexing technique not only provides the PON systems with the aforementioned online network operation functionalities, but also has the excellent potential of achieving the integrated cloud access networks, because of its salient advantages listed below:…”

Performance Tolerance of IMDD DFMA PONs to Channel Frequency Response Roll-Off

“…As such, the CCI effect occurs. In particular, a larger roll-off causes a greater amplitude variation between the two sidebands, thus lower frequency subcarriers suffer more CCI and more low frequency subcarriers' BERs exceed the FEC limit as the roll-off increases [6]. The ONU transmission capacities saturate to maximum when R≤3dB, where ONU2 can support at most 14 (of 15) subcarriers as the first subcarrier must be dropped due to the high attenuation of its sine filter near the DC component.…”

“…To validate the DFMA-PON's feasibility, multipoint-topoint optical OFDM (OOFDM) upstream transmissions of IMDD DFMA PONs [4] have recently been successfully experimentally demonstrated, where Hilbert pair-based digital orthogonal filters are assigned to two spectrally overlapped orthogonal channels occupying a common spectral region. As such, the channel frequency response characteristics influenced the orthogonality between the channel pair, leading to crosschannel interference (CCI) and subsequent system performance degradation [6]. To effectively mitigate the channel frequency response-induced CCI, a DSP-based CCI cancellation (CCIC) technique has been proposed and experimentally demonstrated in a point-to-point IMDD DFMA PON system [6].…”

“…As such, the channel frequency response characteristics influenced the orthogonality between the channel pair, leading to crosschannel interference (CCI) and subsequent system performance degradation [6]. To effectively mitigate the channel frequency response-induced CCI, a DSP-based CCI cancellation (CCIC) technique has been proposed and experimentally demonstrated in a point-to-point IMDD DFMA PON system [6]. Also a more comprehensive DSP-based DFMA channel interference cancellation (DCIC) technique has been numerically investigated in multipoint-to-point IMDD DFMA PONs [7].…”