Abstract
We present the first experimental demonstration of a phase-modulated MMF link implementing high-frequency digital transmission in a cost-effective solution based on direct detection. Successful subcarrier transmission of QPSK, 16-QAM and 64-QAM data channels for bit rates up to 120 Mb/s through a 5 km MMF link is achieved over the microwave region comprised between 6 and 20 GHz. The overall capacity of the proposed approach can be further increased by properly accommodating more passband channels in the operative frequency range determined by the phase-to-intensity conversion process provided by the dispersive nature of the optical fiber. In this sense, our results show the possibility of achieving an aggregate bit rate per length product of 144 Gb/s · km and confirm, in consequence, the possibility of broadband phase-modulated radio over fiber transmission through MMF links suitable for multichannel SCM signal distribution.
Highlights
The increasing transmission capacity demand following the 10-Gigabit Ethernet standard in access and in-building networks has been fuelling dynamic research on different techniques directed to the improvement of the transmission bandwidth in the existing multimode optical fibre (MMF) infrastructure
A vector signal generator generates the radiofrequency (RF) carriers which can be modulated by quadrature phase shift keying (QPSK) or multilevel quadrature amplitude modulation (16-QAM and 64-QAM) data channels at bit rates up to 120 Mb/s
A broadband phase-modulated MMF link has been successfully demonstrated for the first time to our knowledge by subcarrier transmission of high-frequency digital passband channels for bit rates up to 120 Mb/s
Summary
The increasing transmission capacity demand following the 10-Gigabit Ethernet standard in access and in-building networks has been fuelling dynamic research on different techniques directed to the improvement of the transmission bandwidth in the existing multimode optical fibre (MMF) infrastructure. The combination of modefiltering solutions implemented by centrally launching the light from a SMF, and low linewidth lasers has shown the capability of reaching broadband transmission, both radio over fibre [7,8] and digital baseband [6,9] transmission, in middle-reach MMF links. The implementation of these techniques in access networks results in a potential cost reduction, a deeper reduction in complexity can be achieved if we take advantage of the frequency response of phase modulated 2nd-order dispersive fiber links derived from the carrier suppression effect (CSE) at regions far from baseband [11]. We propose a cost-effective PM-MWP link employing direct detection in which the effect of the chromatic dispersion on the double sideband characteristic of the modulated signal allows broadband passband digital transmission through a middle-reach MMF link provided that low-linewidth lasers are used and central launching is implemented. In this paper we report, for the first time to our knowledge, the experimental demonstration of high-frequency digital radio signal transmission at bit rates up to 120 Mb/s in a PM-MWP link comprising a 5 km 62.5-μm core-diameter graded-index silica MMF link
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