Experimental evaluation of a digitized fiber-wireless system employing sigma delta modulation

Abstract

Digitized radio-over-fiber (D-RoF) transport schemes are being pointed as viable alternative solutions to their analog counterparts, in order to avoid distortion/dynamic range problems. Here we propose a novel D-RoF architecture that takes advantage of a bandpass sigma-delta modulator at the transmitter which subsequently permits the usage of a simpler/cheaper base station that avoids the employment of a digital to analog converter. The proposed architecture exploits the properties of the digital signal to enable the extraction of an higher carrier frequency through the employment of a bandpass filter. Furthermore, we present a comprehensive analysis regarding the impact of a low-cost electro-optic modulation on the quality of received demodulated signal. Finally, a comparison performance analysis between the conventional D-RoF and the proposed architecture is presented. We conclude that although the proposed architecture performs similarly to conventional D-RoF schemes, it is more competitive for either upgrading installed systems as well as for new deployments.

Comparison Between Analog Radio-Over-Fiber and Sigma Delta Modulated Radio-Over-Fiber

“…5 as a function of driving current. It can be observed that the VCSEL driving current should be sufficiently large to avoid subtreshold operation [6]. On the other hand, gain compression occurs at higher currents.…”

“…digital communication with a simple, power efficient RRH while completely eliminating the need for high-speed, high resolution DACs is provided by sigma delta-over-fiber (SDoF) [6], [7], [8] and as shown in Fig. 1c.…”

Hybrid CATV/MMW/BB lightwave transmission system based on fiber-wired/fiber-wireless/fiber-VLLC integrations

“…where o P is the output of system detected from the PD, i P is the input of system, 1 n , 2 n , and 3 n are the amplitude coefficients ( 2 n and 3 n are coefficients regarding nonlinearities). Clearly, o P is equal to i G ; substituting Eq.…”

“…A network which can support both wired and wireless communications concurrently has been necessary because of the increased demands for broad bandwidth and high-speed transmission rate [1][2][3][4]. Delivering hybrid cable television (CATV), millimeter-wave (MMW), and baseband (BB) signals over a lightwave transmission system has many advantages, like broad bandwidth, high-speed transmission rate, and wide service area.…”

Real-time all-digital radio-over-fiber LTE transmission

“…To mitigate the linearity requirement, different authors [8], [9] explored how low-cost, less linear modulators, such as vertical cavity lasers (VCSELs), can still be used to transmit RF signals. Delta-Sigma modulation of the RF signal oversamples the signal and quantizes the signal to a limited amount of quantization levels (typically 2, resulting in a singlebit stream).…”