Abstract
We propose an adaptive channel estimation (CE) method for zero-guard-interval (ZGI) coherent optical (CO)-OFDM systems, and demonstrate its performance in a single channel 28 Gbaud polarization-division multiplexed ZGI CO-OFDM experiment with only 1% OFDM processing overhead. We systematically investigate its robustness against various transmission impairments including residual chromatic dispersion, polarization-mode dispersion, state of polarization rotation, sampling frequency offset and fiber nonlinearity. Both experimental and numerical results show that the adaptive CE-aided ZGI CO-OFDM is highly robust against these transmission impairments in fiber optical transmission systems.
Highlights
Coherent optical orthogonal frequency division multiplexing (CO-OFDM) is regarded as a potential candidate for spectrally efficient and high capacity transmission systems attributed to its inherent compact spectrum [1,2]
Via an inverse fast Fourier transform (IFFT) with a size of 128 and the preemphasis to compensate for the transmitter roll-off, the time domain waveform was generated with an oversampling ratio of 1.13. 8-samples cyclic prefix (CP) was inserted for each training symbols (TS) and no CP was added to the data symbols
We presented and experimentally demonstrated a decision feedback channel estimation algorithm for ZGI coherent optical (CO)-OFDM
Summary
Coherent optical orthogonal frequency division multiplexing (CO-OFDM) is regarded as a potential candidate for spectrally efficient and high capacity transmission systems attributed to its inherent compact spectrum [1,2]. The required TS overhead depends on both the rate of the time varying effects of the channel, which determines the required TS insertion frequency, and on the optical signal to noise ratio (OSNR), which is related to the required number of TSs to be averaged for each CE. This time averaging (TA) method achieves an accurate CE at the expense of a reduced SE. We experimentally demonstrate a single channel 28-Gbaud (112 Gb/s) polarization-division multiplexing (PDM) QPSK Adaptive-ZGI CO-OFDM system with a total processing overhead of only 1.03%
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