Abstract
In this paper, we propose adaptively loaded set-partitioned offset quadrature amplitude modulation (SP-offset-QAM) orthogonal frequency division multiplexing (OFDM) for low-cost intensity-modulation direct-detection (IM/DD) communication systems. We compare this scheme with multi-band carrier-less amplitude phase modulation (CAP) and conventional OFDM, and demonstrate >40 Gbit/s transmission over 50-km single-mode fiber. It is shown that the use of SP-QAM formats, together with the adaptive loading algorithm specifically designed to this group of formats, results in significant performance improvement for all these three schemes. SP-offset-QAM OFDM exhibits greatly reduced complexity compared to SP-QAM based multi-band CAP, via parallelized implementation and minimized memory length for spectral shaping. On the other hand, this scheme shows better performance than SP-QAM based conventional OFDM at both back-to-back and after transmission. We also characterize the proposed scheme in terms of enhanced tolerance to fiber intra-channel nonlinearity and the potential to increase the communication security. The studies show that adaptive SP-offset-QAM OFDM is a promising IM/DD solution for medium- and long-reach optical access networks and data center connections.
Highlights
The ever-growing Internet content is driving the rapid development of optical access networks
It is shown that the use of SP-QAM formats, together with the adaptive loading algorithm designed to this group of formats, results in significant performance improvement for all multi-carrier systems
SNRn can be estimated using a training sequence before the payload is sent. This bit and power loading algorithm was originally proposed for SP-QAM based conventional orthogonal frequency division multiplexing (OFDM) [10], but it can be applied to any multi-carrier systems using the SP-QAM formats, including offset-QAM OFDM and multi-band carrier-less amplitude phase modulation (CAP) studied in this paper
Summary
The ever-growing Internet content is driving the rapid development of optical access networks. Singlecarrier formats, such as PAM4 and CAP, have a lower peak-to-average power ratio (PAPR) and have relaxed requirement on quantization resolution, device linearity, etc They may be suitable for high-capacity short-reach connections. We propose adaptively loaded set-partitioned offset quadrature amplitude modulation (SP-offset-QAM) OFDM for IM/DD systems This scheme simultaneously explores the advantages of SP-QAM formats and offset-QAM (de-)multiplexing. It is shown that the use of SP-QAM formats, together with the adaptive loading algorithm designed to this group of formats, results in significant performance improvement for all multi-carrier systems. The proposed scheme is better than SP-QAM based Nyquist FDM, which can be viewed as a special case of multi-band CAP or offset-. The studies give clear implications that the proposed scheme is a very promising solution for medium- and long-reach access networks and data center connections
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