Opto-RF
The ever growing demand for always more capable interconnections, is moving a lot of attention into the optical world. This has led to the creation of an Opto-RF research group, in partnership with the Huawei research center in Milano. This group is in charge of designing the electrical part of transmitters and receivers for such applications. The focus is on CMOS technology, which is not so widespread in this field, and the goal is to achieve comparable or even better results than the most common BiCMOS. The two main limitations are the lower break-down voltage, and transconductance, while cost, better integration of analog and digital parts and the possibility to use complementary structures are the interesting features.
Coherent Optical Transmitter
The Coherent Optical Transmitter is characterized a digital part and an analog part. After the Signal Digital processing the signal is converted in analog domain where it is amplified by Drivers (DRV), they have the aim to drive MachZenders involved in the light modulation.
Coherent Optical Receiver
After the optical fiber we have the Coherent Optical Receiver. In first step the optical signal is demodulated and moved in Base Band by 90 Hybrid, after it the signal is converted in electrical domain by Photodiode detector. In order to improve the noise performances the signal is amplified by Transimpedance Amplifier (TIA). After this processing the signal is converted in digital domain by ADC and processed by the DSP.
Moving from 2-level modulation to more dense modulations allows higher data rates and more efficient bandwidth utilization.
Denser constellations provide higher spectral efficiency; it allows higher Bit rate in correspondence of the same bandwidth. At the same time these constellations require higher Noise and Distortion performances in order to have a low Bit Error Rate. It makes the coherent modulation an advanced and challenging field where it is possible to develop new techniques to improve Bandwidth, Noise and Distortion.