Optical Time Division Multiplexing (OTDM) is a powerful and scalable technique for investigating high-speed data transmission systems, signal processing and monitoring technologies related to serial data rates beyond bandwidth limitation of electronics. The OTDM technique is fundamentally compatible with modern quadrature-amplitude modulation formats and coherent digital detection. In contrast to wavelength division multiplexing (WDM), only one wavelength ("color") of light is used.
The principle of operation of the OTDM is as follows: Different optical pulse currents, called tributaries, originated from the same laser (same central wavelength), are encoded separately by electrically generated data signals. Due to the low duty cycle of their pulses (1.5 ps at 10 GHz), the tributaries are serially interleaved to form the high-speed OTDM serial data signal. At the receiver end, an ultrafast optical clock and data retrieval draws individual time domain tributaries, which are subsequently processed by conventional (opto) electronics.
Based on the OTDM technique, we operate a world-leading testbed for high-speed serial data transmission ranging from 10 Gbit / s to 10.2 Tbit / s. We have previously applied a number of modulation formats ranging from direct detection on / off (OOK), phase shift differential (DPSK) and phase shift quadrature differential (DQPSK) all the way to the coherently detected digital m (BPSK, QPSK, 8-PSK) or quadrature amplitude modulation in m (eg, 16-QAM). Our test bench is designed to operate in the C band (1.55 μm), but can also be adapted to other wavelength regions such as the O band (1.3 μm).