Free Space Optical Communication in Long-Reach Unidirectional Ring-Architecture Fiber Network

Abstract

In the work, a ring-constructed wavelength-division-multiplexing (WDM) access system for delivering multiple free space optical (FSO) wireless signals is investigated. To reach the FSO transmission through single-mode fiber (SMF) connection, the optical wireless unit (OWU) and remote OWU are designed in the WDM network. The downstream and upstream WDM FSO channels could be transmitted in unidirectional propagation with the same wavelength. Hence, the presented ring-based WDM network not only can transmit the FSO signal, but also can circumvent the Rayleigh backscattering (RB) interferometric beat noise. In addition, according to the experimental results, the SMF and FSO transmission lengths can reach 50 km and 500 to 1000 m at the forward error correction (FEC) level without using optical amplification and dispersion compensation, respectively, when four WDM wavelengths are exploited experimentally for demonstration. INDEX TERMS Free space optical (FSO); Rayleigh backscattering (RB), WDM Access, OOK modulation, Ring-architecture.

A high bit rate free space optics based ring topology having carrier‐less nodes

“…The performance of uplink channel-4 sharply degrades and therefore, the FEC target BER of 10 −6 cannot be achieved. The reason behind this trend of receiver sensitivities for the downlink and uplink channels may be understood by considering Equation (5). It may be observed from the equation that the Rytov variance which represents the strength of turbulence is dependent upon the range of the FSO link.…”

“…Furthermore, high margin for P also demonstrates that the proposed model is able to withstand extreme weather conditions that introduce high level of signal attenuation over the channel. P can be computed as the amount of available power after subtracting span and components losses from the power budget [5, 27]. Consequently, P can be derived as.…”

“…The use of FSO in ring topology is most suitable in those scenarios where the capability of add-drop of data is required at multiple intermediate nodes while the distance between the two adjacent nodes is with in the permissible limit [12]. A few recent contributions on the ring-based FSO access networks are proposed in [5,10]. In [5], a hybrid fibre/FSO based ring architecture is presented where the ring is composed of a fibre link while the FSO link is employed between the optical wireless units that are connected to the fibre at four different locations.…”

“…A few recent contributions on the ring-based FSO access networks are proposed in [5,10]. In [5], a hybrid fibre/FSO based ring architecture is presented where the ring is composed of a fibre link while the FSO link is employed between the optical wireless units that are connected to the fibre at four different locations. A similar network is proposed in [10], with a major difference that the data can be transmitted in both directions along the ring.…”

“…Integrated optical wired and wireless access networks provide a promising solution for future broadband communication networks [4]. The capacity of these integrated wired and wireless links can be increased by employing wavelength division multiplexing (WDM) technology, where multiple optical wavelengths carry data of different channels [5]. The PON architectures are built upon different network topologies such as tree, ring and bus topology, as demonstrated in [6].…”