No abstract

We experimentally demonstrate the use of optical frequency combs (OFCs), generated by a photonic integrated circuit (PIC), in a flexible optical distribution network based on fiber-optics and free-space optics (FSOs) links, aimed at the fifth generation of mobile network (5G) Xhauls. The Indium Phosphide (InP) monolithically integrated OFC is based on cascaded optical modulators and is broadly tunable in terms of operating wavelength and frequency spacing. Particularly, our approach relies on applying the PIC in a centralized radio access network (C-RAN) architecture, with the purpose of optically generating two low-phase noise mm-waves signals for simultaneously enabling a 12.5-km of single-mode fiber (SMF) fronthaul and a 12.5-km SMF midhaul, followed by a 10-m long FSO fronthaul link. Moreover, the demonstrator contemplates two 10-m reach 5G wireless access networks operating in the 26 GHz band, i.e. over the frequency range 2 (FR2) from the 5G NR standard. The proposed integrated OFC-based 5G system performance is in accordance to the 3rd Generation Partnership Project (3GPP) Release 15 requirements, achieving a total wireless throughput of 900 Mbit/s.

We experimentally demonstrate the use of optical frequency combs (OFC), generated by a photonic integrated circuit (PIC), in a flexible optical distribution network based on fiber-optics and free-space optics (FSO) links, aiming the fifth generation of mobile network (5G) Xhauls. The Indium Phosphide (InP) monolithically integrated OFC is based on cascaded optical modulators and is broadly tunable in terms of operating wavelength and frequency spacing. Particularly, our approach relies on applying the PIC in a centralized radio access network (C-RAN) architecture, with the purpose of optically generating two low-phase noise mm-waves signals for simultaneously enabling a 12.5-km of single-mode fiber (SMF) fronthaul and a 12.5-km SMF midhaul, followed by a 10-m long FSO fronthaul link. Moreover, the demonstrator contemplates two 10-m reach 5G wireless access networks operating in the 26 GHz band, i.e. over the frequency range 2 (FR2) from the 5G NR standard. The proposed integrated OFC-based 5G system performance is in accordance to the 3rd Generation Partnership Project (3GPP) Release 15 requirements, achieving a total wireless throughput of 900 Mbit/s.

The characterization of a broadband Si3N4 integrated linear optical processor operating in the C-band is reported. The impact of losses on the processor accuracy is discussed towards the photonic implementation of state-of-the-art neural networks.

We experimentally demonstrate a low-phase-noise tenfold frequency multiplier based on a compact integrated optical frequency comb (OFC) generator. The Indium Phosphide (InP) monolithically integrated OFC is based on a flexible scheme using cascaded optical modulators. The extremely compact frequency multiplier is broadly tunable in wavelength and in OFC repetition frequency, making it interesting for high-spectralpurity mm-waves applications. OFC generation with a 2.6 GHz spacing and 19 tones within a 10 dB power range and an optical signal-to-noise ratio (OSNR) higher than 40 dB is reported. Using a 74 GHz-bandwidth photodetector, we achieve a set of 2.6 GHz phase-stabilized electrical tones, reaching carriers up to 39 GHz with a high signal-to-noise ratio (SNR). In particular, the OFCbased tenfold-multiplied signal (26 GHz) provides a remarkable low-phase-noise feature, equivalent to the commercially available radiofrequency (RF) generator used as a source at the same electrical power. At 26 GHz, phase-noise of -50 dBc/Hz and -80 dBc/Hz are reported for 10 Hz and 1 kHz offsets, respectively. The proposed system enables frequency multiplication up to 12times without phase impairments, i.e., phase noise performance equivalent to a commercial RF generator, validating its potential to low-phase-noise and high-spectral-purity mm-wave applications.Index Terms-5G, mm-waves, optical frequency comb (OFC) and photonic integrated circuits (PIC).