Abstract
We experimentally demonstrate an aggregate 86-GBaud (over three sub-bands and one polarization) signal generation based on subcarrier multiplexing technique using IQ mixers, an electrical 90 degree hybrid, and diplexers. The electrical hybrid allows transmitter-side digital signal processing to be simplified to pulse shaping and digital pre-emphasis. We verified the configuration by testing the performance of an 86-GBaud Nyquist-shaped 16 quadrature amplitude modulation signal with differential bit encoding. The implementation penalty assuming 7% hard-decision forward error correction is reduced to 2 dB by utilizing a 31-tap decision-directed least mean square based multiple-input multiple-output equalizer for sideband crosstalk mitigation.
Highlights
Driven by the ever increasing requirement to transport more data, higher-speed (400 Gb/s or 1 Tb/s) optical interfaces are highly desirable
Each technique offers its own unique features and drawbacks, and given recent progress for all options, no clear leading approach has yet been identified. We introduce another form of frequency multiplexing, adding IQ mixers and hybrid couplers in the radio frequency (RF) domain in order to simplify the transmitter-side digital signal processing (DSP), which enables simple RF oscillator suppression via DC offset optimization without sacrificing digital to analogue converters (DACs) resolution and eliminates joint sub-band processing in the transmitter
We firstly measured the optical signal-to-noise ratio (OSNR) performance for each individual band signal to verify the performance improvement brought by digital pre-emphasis
Summary
Driven by the ever increasing requirement to transport more data, higher-speed (400 Gb/s or 1 Tb/s) optical interfaces are highly desirable. Either a large number of parallel opto-electronic components or additional modulators for frequency-locked subcarriers generation are required, which inevitably increases transponder cost and complexity. Since transponder cost per bit generally decreases as data rates per optoelectronic conversion are increased, great efforts have been made to electrically generate high symbol rate signals in single carrier system with single optical modulator. The proposed electrical approaches mainly include analog-multiplexed digital to analogue converters (DACs) [8], all-DACs [9], electrical time-division multiplexing (ETDM) [10] and digital bandwidth interleaving [11], with generated signals of 80-GBaud four-level pulse amplitude modulation (PAM4), 105-Gaud probabilistic shaped 64-ary quadrature amplitude modulation (64QAM), 120-GBaud 16QAM, and 190-GBaud PAM4. Each technique offers its own unique features and drawbacks, and given recent progress for all options, no clear leading approach has yet been identified
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