Millimeter-Wave Radio Over Fiber Optical Upconversion Techniques Relying on Link Nonlinearity

Abstract

Abstract-A study of advanced upconversion techniques used in radio over fiber (ROF) is provided. With the huge increase in both the number of wireless communication subscribers and the bandwidth required per customer, migrating to higher frequencies, i.e., from lower radio frequency to millimeter-wave carriers, is an essential solution. However, due to the short propagation range of millimeter waves, a large number of radio access points are required for providing reliable coverage, which would increase the infrastructure costs. Hence, the transmission of RF signals between the central (or control) points and radio access points (or remote antenna units) using optical fibers is one of the major access network solutions that have been proposed for future high-bandwidth wireless communication systems. In this paper, we introduce the basics of ROF communication, including optical modulation, the optical channel, and the optical detection techniques. Then we survey the family of advanced optical upconversion techniques that exploit the nonlinearity of the ROF link. Specifically, we describe how optical upconversion can be achieved by exploiting the Mach-Zehnder modulator's nonlinearity, wavelength conversion techniques, or the photodetector's nonlinearity. The wavelength conversion techniques rely on the nonlinearities present in the fiber, in the optical amplifier, or in the electroabsorption modulator. Index Terms-Radio over fiber, direct modulation, external modulation, direct photo-detection, coherent photo-detection, mach zehnder modulator, cross phase modulation, self phase modulation, four wave mixing, stimulated raman scattering, stimulated brillouin scattering, optical frequency modulation, optical phase modulation, optical intensity modulation, optical single side band modulation, optical double side band modulation, optical carrier suppression modulation, sub carrier multiplexing, wavelength division multiplexing, optical N-tupling, optical upconversion, semiconductor optical amplifier, electro-absorption modulator, mach zehnder interferometer, highly nonlinear dispersion shifted fiber, nonlinear optical loop mirror, millimeter wave, 5G, microwave photonics.

Joint Space-Time Block-Coding and Beamforming for the Multiuser Radio Over Plastic Fiber Downlink

“…Their output signal will be fed into a MZM. Then the MZM copies the STBC signals to multiple wavelengths by exploiting the nonlinearity of MZM [17]. The wavelengths can be tuned by a frequency-controllable MZM drive signal in order to control the beamsteering angle.…”

“…As shown in Figure 2, the multi-wavelength signal is generated with the aid of the MZM's nonlinearity, where the ODSB appears at every wavelength [17]. This is arranged for ensuring that different wavelengths experience different delays in the CFBG and hence beamforming can be achieved for each STBC signal, which is a benefit of the CFBG-inducedtime-delay of each wavelength.…”

Optical single sideband signal generation relying on a single‐drive Mach–Zehnder modulator for radio over fibre communications

“…The advantages of the ROF-aided architecture include ability to implement multiple-inputmultiple-output techniques, ease of system upgrades, better resource allocation, better wireless coverage and higher power efficiency [1]. A comprehensive study of ROF techniques and its advantages has been provided in [1,3,9].…”

“…Optical single sideband (OSSB) modulation scheme was then proposed for overcoming this challenge [9]. Whilst being tolerant to the fibre-dispersion-induced power attenuation, the OSSB modulation scheme requires the employment of a dual-drive modulator [3]. Alternatively, one can employ a single-drive modulator, but will have to employ an extra temperature-sensitive fibre Bragg grating (FBG) optical filter for eliminating one of the sidebands [1].…”

“…Radio over fibre (ROF) is a promising solution to the challenge of having a large number of small cells with high-RF frequencies [3][4][5][6]. It is also possible for macrocells to co-exist with microcells, when relying on the ROF technique [7].…”