Abstract
In this paper, we theoretically analyze and demonstrate that spectral efficiency of a conventional direct detection based optical OFDM system (DDO-OFDM) can be improved significantly using frequency interleaving of adjacent DDO-OFDM channels where OFDM signal band of one channel occupies the spectral gap of other channel and vice versa. We show that, at optimum operating condition, the proposed technique can effectively improve the spectral efficiency of the conventional DDO-OFDM system as much as 50%. We also show that such a frequency interleaved DDO-OFDM system, with a bit rate of 48 Gb/s within 25 GHz bandwidth, achieves sufficient power budget after transmission over 25 km single mode fiber to be used in next-generation time-division-multiplexed passive optical networks (TDM-PON). Moreover, by applying 64- quadrature amplitude modulation (QAM), the system can be further scaled up to 96 Gb/s with a power budget sufficient for 1:16 split TDM-PON.
Highlights
Optical orthogonal frequency division multiplexing (O-OFDM) brings the benefit of electronic equalization and robustness against multi-path fading of legacy wireless-OFDM systems into the optical domain to combat against fiber impairments, such as chromatic dispersion and polarization mode dispersion (PMD) and achieved impairments-tolerant ultra high speed optical systems [1,2,3]
In order to resolve these issues in short-haul communications, such as passive optical network (PON), a frequency interleaving method has been proposed where two neighboring DDO-OFDM channels are overlapped in such a way that the mandatory spectral gap of a channel is being occupied by the OFDM signal band of its neighbor and vice versa
At optimum operating condition, frequency interleaving of two adjacent DDO-OFDM channels can increase the spectral efficiency up to 50% over a standard DDO-OFDM system
Summary
Optical orthogonal frequency division multiplexing (O-OFDM) brings the benefit of electronic equalization and robustness against multi-path fading of legacy wireless-OFDM systems into the optical domain to combat against fiber impairments, such as chromatic dispersion and polarization mode dispersion (PMD) and achieved impairments-tolerant ultra high speed optical systems [1,2,3]. In order to resolve these issues in short-haul communications, such as PON, a frequency interleaving method has been proposed where two neighboring DDO-OFDM channels are overlapped in such a way that the mandatory spectral gap of a channel is being occupied by the OFDM signal band of its neighbor and vice versa. This overlapping enhances the spectral efficiency of a conventional DDO-OFDM system significantly, as shown in Fig. 1 [17,18,19]. Received 5 Aug 2010; revised 1 Oct 2010; accepted 1 Oct 2010; published 19 Oct 2010 25 October 2010 / Vol 18, No 22 / OPTICS EXPRESS 23163
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