Optical Channel Aggregation by Coherent Spectral Superposition with Electro-Optic Modulators

TL;DR

This paper introduces a linear, all-optical spectral aggregation method using coherent superposition and electro-optic modulators, enhancing spectral efficiency and network capacity without nonlinear effects.

Contribution

It presents a novel linear spectral aggregation technique based on coherent superposition with electro-optic modulators, enabling flexible and efficient optical signal combination.

Findings

Successfully aggregated multiple low-bitrate channels into higher spectral efficiency signals.

Demonstrated experimental aggregation of various modulation formats including BPSK, QPSK, and PAM-4.

Showed significant improvement in spectral utilization and potential for reconfigurable optical networks.

Abstract

As the bit rates of routed data streams exceed the throughput of single wavelength-division multiplexing channels, spectral traffic aggregation becomes essential for optical network scaling. Here we propose a scheme for all-optical aggregation of several low bitrate channels to fewer channels with higher spectral efficiency. The method is based on optical vector summation facilitated by coherent spectral superposition. Thereby it does not need any optical nonlinearities and is based on linear signal processing with an electro-optic modulator. Furthermore, optical phase tuning required for vector addition can be easily achieved by a phase tuning of the radio frequency signal driving the modulator. We experimentally demonstrate the aggregation of two 10 Gbaud BPSK signals into one 10 Gbaud QPSK and one 10 Gbaud PAM-4 signal, the aggregation of two 10 Gbaud QPSK signals into 10 Gbaud QAM-16, as well as the aggregation of sinc-shaped Nyquist signals. The presented concept of in-line all-optical aggregation demonstrates considerable improvement in network spectrum utilization and can significantly enhance the operational capacity with reduced complexity. It provides a new way for realizing the flexible optical transmission of advanced modulation format signals, and suits for future dynamically reconfigurable optical networks. Since the method is based on linear signal processing with electro-optic modulator, integration into any integrated photonic platform is straightforward.