The millimeter-wave (mm-wave) frequency band has emerged as a means to overcome current radio frequency spectral limitations and represents an interesting solution to fulfill the bandwidth and networking requirements of fifth generation (5G) mobile communications and beyond. Photonic generation of these frequencies holds advantages over electronic methods in terms of cost and effective network distribution. Due to their coherent nature, optical frequency combs (OFC) are a promising solution for the efficient generation of mm-wave frequencies. The work outlined examines the use of OFCs in a mm-wave radio-over-fiber (RoF) heterodyne system with regard to the specific requirements of a 5G candidate waveform, universally filtered orthogonal frequency division multiplexing. Through experimentation and simulation, the key limitations of linewidth, effective path length difference, and relative intensity noise (RIN) are explored. Results are presented, in terms of error vector magnitude (EVM), for a wide range of system parameters highlighting important considerations to be taken in designing future mm-wave RoF systems employing OFCs. Performance of ∼5% EVM using single sideband modulation is achieved for optimized system conditions and an RIN level of −132 dB/Hz.

The provision of both wireless and wired services in the optical access domain will be an important function for future passive optical networks (PON). With the emergence of 5 th generation (5G) mobile communications, a move toward a dense deployment of small cell antenna sites, in conjunction with a cloud radio access network (C-RAN) architecture, is foreseen. This type of network architecture greatly increases the requirement for high capacity mobile fronthaul and backhaul links. An efficient way of achieving such connectivity is to make use of wavelength division multiplexed (WDM) PON infrastructure where wireless and wired services may be converged for distribution. In this work, for the first time, the convergence of 5G wireless candidate waveforms with a singlecarrier wired signal is demonstrated in a PON. Three bands of universally filtered orthogonal frequency division multiplexing (UF-OFDM) and generalized frequency division multiplexing (GFDM), are transmitted at an intermediate frequency in conjunction with a digital 10Gb/s pulse amplitude modulation (PAM-4) signal in the downlink direction. Orthogonal frequency division multiplexing (OFDM) is also evaluated as a benchmark. Results show, for each waveform, how performance varies due to the 5G channel spacing -indicating UF-OFDM's superiority in terms of PON convergence. Successful transmission over 25km of fibre is also demonstrated for all waveforms.

The authors demonstrate single-polarisation WDM transmission with capacities higher than 400 Gb/s and 1 Tb/s, and show the possibility of obtaining capacity in excess of 4 Tb/s for interconnect applications within and between data centres, based on a single laser source. Quantum Dash (Q-Dash) passively modelocked lasers (PMLLs), with free spectral ranges of 82.8, 44.7, and 10.2 GHz, were used for the generation of a large number of carriers, enabling high data rate transmission. The terabit per second transmission using Q-Dash MLLs was demonstrated in this paper, and was enabled using intensity modulated and directly detected (IM/DD) single-side band orthogonal frequency-division multiplexed signals. The system performance was investigated for a propagation distance of 3 and 50 km of standard single mode fibre indicating the potential for interconnect applications within and between data centres. The relative intensity noise (RIN) of all Q-Dash devices was characterised, and the effect of RIN on the system performance was investigated by examining the errorvector magnitude of OFDM subcarriers over the desired frequency range.

We demonstrate detailed characterization results of a hybrid InP-TriPleX photonic integrated tunable laser based on silicon nitride microring resonators. A tuning range of 50 nm across the C-band, side-mode suppression ratio (SMSR) >50 dB, high output power (∼10 dBm), linewidth of <80 kHz across the whole tuning range, and µs switching speed are achieved. The delayed self-heterodyne (DSH) method is used for the linewidth measurement, the lowest linewidth can be achieve is ∼35 kHz. The FM noise spectrum is also measured to show the 1/f noise and white noise characterization. Furthermore, the device demonstrates performance comparable with commercial external cavity lasers in 64-QAM coherent system.

Fifth generation (5G) mobile communications will require a dense deployment of small cell antenna sites and higher channel bandwidth, in conjunction with a cloud radio access network (C-RAN) architecture. This necessitates low latency and high capacity architecture in addition to energy and cost efficient fronthaul links. An efficient way of achieving such connectivity is to make use of optical fiber based infrastructure where multiple wireless services may be distributed over the same fiber to remote radio head (RRH) sites. In this work, we demonstrate the spectral containment of 4G long term evolution (LTE) signal and 5G candidate waveforms-generalized frequency division multiplexing (GFDM) and universally filtered orthogonal frequency division multiplexing (UF-OFDM), through a directly modulated link. 75 bands of LTE and 10 bands of 5G waveforms are successfully transmitted over 25 km analog intermediate frequency signal over fiber (AIFoF) link through our setup, limited only by the bandwidth of the laser. For the first time, we demonstrate the fronthaul network for providing simultaneous 4G & 5G services by propagating LTE signals in coexistence with UF-OFDM.