Spectrally Efficient Compatible Single-Sideband Modulation for OFDM Transmission With Direct Detection

Optical Direct Detection for 100G Short Reach Applications

“…Traditional direct detection (DD) scheme uses intensity modulation at the transmitter [4][5]. The modulator is driven by a real-valued RF signal, leading to a Hermitian symmetric optical spectrum.…”

“…The modulator is driven by a real-valued RF signal, leading to a Hermitian symmetric optical spectrum. This method wastes half of the optical spectral efficiency; more importantly, it gives rise to the problem of CD-induced power fading [4] which limits the transmission distance. The most straightforward approach to avoid the problem is to use single side-band (SSB) field modulation [6][7], which is adopted by a set of OFDM based SCOH systems as illustrated in Fig.…”

“…While long-haul networks have witnessed a capacity evolution to multi-Terabit during the last decade with the revival of coherent communications [1][2], short-reach networks [3][4][5][6][7][8][9][10][11][12] within distance of hundreds of kilometers need to increase their capacity per wavelength beyond 40 or even 100 Gb/s to meet the ever-increasing traffic demand. Different from long-haul communications, these short-reach networks require massive number of transceivers across diverse geographic areas.…”

“…Direct detection (DD) [4][5][6][7][8][9][10][11][12] can significantly lower the expense compared with the coherent counterpart, making it suitable for short-reach applications. However, the conventional intensity modulation direct detection (IM-DD) systems cannot undertake the task due to two fundamental bottlenecks: (i) chromatic dispersion (CD) induced signal fading due to the lack of receiver phase diversity [4][5], which limits the transmission distance; and (ii) 2nd order nonlinearity due to photo-detection [6][7], which limits the system capacity. A multitude of solutions have been proposed to overcome the problems, among which a host of self-coherent (SCOH) systems have attracted most attention.…”

61 Gbits/s direct-detection optical OFDM based on blockwise signal phase switching with signal-to-signal beat noise cancellation

“…Single-sideband (SSB) modulation is effective in eliminating the dispersion fading by completely removing the lower sideband. Various versions of SSB modulation have been demonstrated [6][7][8]. Conventional SSB modulation is achieved at the cost of reduced electrical spectral efficiency, thus requiring high electrical bandwidth for the components and increasing the transponder cost.…”