Institute of Photonics and Quantum Electronics (IPQ)

Optical Communications

The Optical Communications Research Group aims at Tbit/s data transmission exploiting novel concepts and components. This includes multi-carrier communication systems based on optical frequency combs, higher-order modulation formats as well as signal processing for data communications.

Artist’s view of an on-chip multi-channel optical transmitter setup comprising a laser source, frequency comb generator, an array of modulators which are connected with photonic wirebonds.

Driven by the vision of an integrated communication system comprising integrated optical frequency comb sources, modulators and multiplexers, the Optical Communications Group investigates data transmission beyond data rates of 1 Tbit/s using coherent modulation formats such as quadrature phase shift keying (QPSK) and M-ary quadrature amplitude modulation (M-QAM). Therefore, methods are being investigated in order to efficiently generate optical frequency combs by way of integrated optical components. Spectral efficiency is a key characteristic in today’s telecom systems but will also gain importance for applications in datacom industry. Therefore, pulse shaping techniques that limit the occupied channel bandwidth is another important aspect under investigation: The combination of frequency combs and pulse shaping allows for a dense packing of individual optical channels without suffering from intersymbol interference (ISI) or interchannel interference due to frequency drifts of the individual optical carriers.

Using our 92 GSa/s multi-format transmitter, we are able to generate highspeed data signals with various modulation formats and pulse shapes. The electrical data is modulated onto optical carriers using either commercial lithium niobate (LiNbO3) IQ modulators or silicon-organic hybrid (SOH) modulators that are designed in-house by the PIC Design and Fabless Fabrication Group. Our dual-polarization coherent receiver completes an end-to-end optical transmission system and allows for subsequent offline data analysis and processing.

For transmission experiments, our lab is equipped with reconfigurable optical switches, multiplexers, and filters and includes a total of several hundred kilometers of single-mode fiber (SMF) and 150 km ultra-large area fiber (ULAF).