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.

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Abstract-This paper studies the key aspects of an optical link which transmits a broadband microwave filter bank multicarrier (FBMC) signal. The work is presented in the context of creating an all-analogue real-time multi-gigabit orthogonal frequency division multiplexing (OFDM) electro-optical transceiver for short range and high capacity data center networks. Passive microwave filters are used to perform the pulse shaping of the bit streams, allowing an orthogonal transmission without the necessity of digital signal processing (DSP). Accordingly, a cyclic prefix that would cause a reduction in the net data rate is not required. An experiment consisting of three orthogonally spaced 2.7 Gbaud quadrature phase shift keyed (QPSK) subchannels demonstrates that the spectral efficiency of traditional DSP-less subcarrier multiplexed (SCM) links can be potentially doubled. A sensitivity of -29.5 dBm is achieved in a 1 kilometer link.