Abstract
In optical OFDM (OOFDM) intensity-modulation and direct-detection (IMDD)
single-mode fibre transmission systems using directly modulated DFB lasers
(DMLs), wavelength-offset optical filtering considerably improves extinction
ratios of OOFDM signals. However, optical filter-induced group delays bring
about OOFDM signal spectrum distortions. Detailed investigations show that
group delays associated with super Gaussian optical bandpass filters (OBPFs)
significantly reduce both the dispersion tolerance and achievable optical
power budget (OPB) of the system. To solve such a challenge, two simple
approaches are proposed including combined optical filtering by using a ring
resonator filter after a super Gaussian OBPF, and cascaded optical filtering
by using multi-stage ring resonator filters. It is shown that, by optimizing
ring resonator filter parameters, the proposed approaches can completely
eliminate the filter group delay effect and enable 7 dB OPB
improvements.
© 2011 IEEE
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