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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Optical heterodyne analog radio-over-fiber (A-RoF) links provide an efficient solution for future millimeter wave (mmwave) wireless systems. The phase noise of the photo-generated mm-wave carrier limits the performance of such links, especially, for the transmission of low subcarrier baud rate multi-carrier signals. In this work, we present three different techniques for the compensation of the laser frequency offset (FO) and phase noise (PN) in an optical heterodyne A-RoF system. The first approach advocates the use of an analog mm-wave receiver; the second approach uses standard digital signal processing (DSP) algorithms, while in the third approach, the use of a photonic integrated mode locked laser (MLL) with reduced DSP is advocated. The compensation of the FO and PN with these three approaches is demonstrated by successfully transmitting a 1.95 MHz subcarrier spaced orthogonal frequency division multiplexing (OFDM) signal over a 25 km 61 GHz mm-wave optical heterodyne A-RoF link. The advantages and limitations of these approaches are discussed in detail and with regard to recent 5G recommendations, highlighting their potential for deployment in next generation wireless systems.

Strict optical linewidth/coherence requirements for A-RoF systems are overcome through development of an analog optical heterodyne architecture tolerant to phase noise and carrier offset. Successful generation and reception of a 60GHz UF-OFDM signal using two free-running tunable lasers, without digital phase/frequency offset compensation, is demonstrated.

In this article, analog fiber optic links (radio-over-fiber, RoF, links) are presented as a flexible, low-cost solution for in-house distribution of millimeter-wave (mmw) signals. Mode-locked laser diodes (MLLD) serve as inexpensive mmw sources for the downlink distribution of mmw signals across an optical fiber link. We compare the robustness of direct and external RF modulation for such MLLD-based RoF systems, whereas the error vector magnitude (EVM) of the received symbols serves as a figure of merit. On the eve of 60 GHz WLAN standardization, we experimentally investigate the transmission of narrowband WLAN (IEEE 802.11a) signals in the millimetric range at moderate data rates. We also demonstrate broadband transmission of multi-band orthogonal frequency-division multiplexing (MB-OFDM) ultra-wideband (UWB) european computer manufacturers association (ECMA 368) signals in the 60 GHz band for data rates of up to 480 Mbps.

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In this paper, a complete theoretical and experimental study of amplitude noise impact on performance of radio-overfiber (RoF) communication system in millimeter-wave (MMW) frequency band is presented. A simulation method is also presented, using which one can determine the origin of the amplitude noise which has the most impact on error vector magnitude (EVM). This method is based on analyzing the trends of EVM versus received optical power. The impact of different optical and electrical noise such as relative intensity noise, shot noise and thermal noise on EVM is precisely studied employing experimental and theoretical analysis. In the proposed RoF system, two techniques are used to generate MMW signal, and the EVM results are compared from amplitude noise viewpoint. In the first technique, two independent distributed feedback lasers are used to generate MMW signal at the output of a photodetector, and the second technique is based on a passively mode-locked laser diode. Impact of optical sources phase noise on performance of the system is removed using a noncoherent down-conversion method based on envelope detector. Using this method, a very good matching between the experimental and the simulation results is observed.Index Terms-Distributed feedback (DFB) laser, envelope detector, error vector magnitude (EVM), millimeter wave (MMW), passively mode-locked laser diode (PMLLD), phase noise, radioover-fiber (RoF), relative intensity noise (RIN), shot noise.

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