Discrete-multitone modulation for short distance 100 Gbit/s optical links
The commercially available 100 Gbit/s optical channel employs coherent modulation and demodulation allowing transmission over long distances, up to thousands of kilometers, but for short distances the cost of a coherent receiver can be overkill. In literature there are several techniques, based on advanced different digital modulation schemes, that reduce the complexity of the transmitter or the receiver, allowing a more cost effective solution. The contribution of this work is the design and implementation of a communication system employing Discrete Multitone (DMT) modulation with bit and power loading, transmitted using an externally modulated laser in C-band, optically amplified, and received with a single photodiode (direct detection). After the design of the system followed by numerical simulations, it has been experimentally tested both in back-to-back and over several spans of Standard Single-Mode optical Fibers (SSMFs), up to 80 km. We studied and adopted Single Side-Band (SSB) at the transmitter to increase spectral efficiency and reduce the effects of Chromatic Dispersion (CD).