M-QAM transmission over hybrid microwave photonic links at the K-band

Abstract

Two experimental configurations of a hybrid K-band (25 GHz) microwave photonic link (MPL) are investigated for seamless broadband wireless access networks. Experimental configurations consist of optical fiber, free-space optics (FSO) and radio frequency (RF) wireless channels. We analyze in detail the effects of channel impairments, namely fiber chromatic dispersion, atmospheric turbulence and multipath-induced fading on the transmission performance. In the first configuration, transmission of the 64-quadrature amplitude modulation (QAM) signal with 5, 20 and 50 MHz bandwidths over 5 km standard single-mode fiber (SSMF), 2 m turbulent FSO and 3 m RF wireless channels is investigated. We show that, for QAM with a high bandwidth, the link performance is being affected more by atmospheric turbulence. In the second configuration, the 20 MHz 4/16/64-QAM signals over a 50 km SSMF and 40 m FSO/RF wireless links are successfully transmitted with the measured error vector magnitude (EVM) values of 12, 9 and 7.9%, respectively. It is shown that, for all transmitted microwave vector signals, the bit error rate is lower than the hard-decision forward-error-correction limit of 3.8×10 −3. Moreover, an extended FSO link span of 500 m for 25 GHz hybrid MPL with 16-QAM at 10 Gb/s under the weak and strong turbulence regimes is evaluated via simulation analysis to mimic a practical outdoor system.

Transmitters for Combined Radio Over a Fiber and Outdoor Millimeter-Wave System at 25 GHz

“…However, the size of MZM can be reduced by integrating, as shown for example in [11]. Note that by using single drive MZM in the null transmission point, a carrier suppressed regime can be achieved, resulting in frequency doubling of the original RF signal after beating in a photodiode, as experimentally demonstrated in laboratory conditions [12], [13]. However, the operation in the null transmission point further reduces optical signal power due to high losses and second MZM needs to be used for data modulation.…”

M-QAM signal transmission at the photonically generated K-band over thermal-induced turbulent FSO links with different turbulence distributions

“…In particular, FSO is affected by atmospheric turbulence created by temperature gradients [15][16][17] occurring naturally in an outdoor environment. However, the thermal distribution can vary significantly along the FSO link especially in the cities as a result of the presence of the sources of hot and cold air, e.g.…”

On N-PAM and M-QAM implementation within the hybrid RoF-FSO-PON system

“…Radio-over-fiber (RoF) systems operating in the MMW bands (e.g., within 24 -60 GHz) take full advantage of broadband and lightwave features of optical fiber (OF) such as single-mode fiber (SMF) and multi-mode fiber (MMF) [2], [3]. They have been identified as potential candidates to extend the transmission range and offer higher Rb e.g., by distributing the MMW signal from the central station (CS) to the remote base station (BS) or in convergent optical and BWA networks [4].…”

“…They have been identified as potential candidates to extend the transmission range and offer higher Rb e.g., by distributing the MMW signal from the central station (CS) to the remote base station (BS) or in convergent optical and BWA networks [4]. MMW signals can be photonically generated by different techniques, among others, by using optical heterodyning or external modulation [3], [5]. Approaches employing a Mach-Zehnder modulator (MZM) at different bias point allow obtaining modulation schemes such as double sideband, single sideband and optical carrier suppression (OCS) [4].…”

“…Approaches employing a Mach-Zehnder modulator (MZM) at different bias point allow obtaining modulation schemes such as double sideband, single sideband and optical carrier suppression (OCS) [4]. Recent literature reports a number of schemes using MZMs e.g., a 60 GHz MMW signal was used for 2 Gb/s data transmission using two cascaded MZMs over a 21 km of SMF [6], a 24 Gb/s carrier-less amplitude and phase modulated signal over 40 GHz MMW along 40 km of SMF and a 1.5 m of wireless link [7] and a 25 GHz MMW over a 50 km of SMF and 40 m of wireless link [3].…”