Simultaneous Phase Noise Reduction of 30 Comb Lines from a Quantum-Dash Mode-Locked Laser Diode Enabling Coherent Tbit/s Data Transmission

InAs/InP quantum-dash lasers

“…Each channel is directly modulated at 28 Gb/s in OOK format after 100 km fiber. Alternatively, feed forward heterodyne [98] and self-homodyne [99] detection schemes were employed by J. Pfeifle et al to reduce the phase noise and optical linewidth of QD-MLL. In Ref.…”

“…In Ref. [98], coherent Tbit/s transmission was demonstrated on simultaneous 30 comb lines at 18 Gbaud QPSK signal and over 75 km fiber, with an aggregate capacity of w 1 Tbit/s. This was further enhanced to an aggregate data rate of 1.562 Tbit/s with 25 comb lines of QD-MLL via 16 QAM transmission, and at a symbol rate of 18 Gbaud, utilizing self-homodyne system [99].…”

Comb-based WDM transmission at 10 Tbit/s using a DC-driven quantum-dash mode-locked laser diode

“…These limitations may be overcome by so-called quantum-dash (QD) mode-locked laser-diodes (MLLD) [12][13][14][15][16][17][18][19][20][21]. These devices combine an inhomogeneously broadened gain spectrum of the QD material with passive mode-locking through four-wave mixing [12,13] and allow for generation of broadband flat frequency combs.…”

Ultra-narrow linewidth quantum dot coherent comb lasers with self-injection feedback locking

“…As a consequence, those CCLs are not satisfactory for Tb/s (and higher) coherent networking systems [17]. In order to improve net data transmission rates and spectral efficiency in optical coherent communication systems, researchers have put significant efforts to simultaneously reduce optical linewidth of each individual wavelength channel of CCLs [18,19]. A feed-forward heterodyne detection scheme [18] has been used to simultaneously reduce the optical linewidth of many comb lines from a mode-locked laser, but this method has difficulty producing a large set of comb lines (more than 20) simultaneously narrowed to a high degree (below a few hundred kHz).…”

“…A feed-forward heterodyne detection scheme [18] has been used to simultaneously reduce the optical linewidth of many comb lines from a mode-locked laser, but this method has difficulty producing a large set of comb lines (more than 20) simultaneously narrowed to a high degree (below a few hundred kHz). To circumvent the issues associated with the large linewidth a self-homodyne system has been tried where unmodulated carriers are transmitted as local oscillators along with the modulated signal [19]. Neither of these approaches actually address the linewidth of the laser source itself.…”