SMF/FSO integrated dual-rate reliable and energy efficient WDM optical access network for smart and urban communities

Abstract

To handle the massive high-speed internet traffic, free space optics (FSO) or single-mode fiber (SMF) based fiber optic communication is being used everywhere across the world. These technologies are capable of providing huge bandwidth and transmitting the data at very high speed with low energy consumption. FSO is a very convenient technology to quickly expand the legacy network in the adverse geographical areas. However, its link performance is highly dependent of inconsistent weather conditions. SMF based fiber optic link has a very low loss and its performance is almost independent on the weather conditions. Though, the installation and maintenance of fibers are quite complex and costly. Individually, FSO or SMF links have their limitations and have to be integrated to leverage their benefits. In this paper, we integrated FSO/SMF links and compared the performance of the proposed architecture which is capable of providing high-speed dual-rate data transmission. The proposed architecture transmits data over either FSO or SMF or both links simultaneously and has 100% more reliability against any one of the link failures. In case of operational link failure (FSO/SMF), data may be switched to the alternative working link (SMF/FSO), simply by tuning the transmitted signal by 50 GHz. The proposed architecture is also reliable against the optical line terminal transceiver (TRx) failure as each user located in the network can be served by two transceivers (1 Gbps and 10 Gbps). The proposed architecture also supports the wavelength division multiplexing overlay transmission for broadcasting the common signal to all the available users in the networks. The architecture reduces ~ 27% of the energy consumption by utilizing the appropriate link of hybrid architecture and TRx according to weather conditions and traffic load. The integrated architecture looks attractive for providing energy-efficient, high speed, and reliable internet coverage to the areas where there is a difficulty of laying fibers and has frequent fiber faults. The architecture is useful for strengthening and boosting rural and urban development.

Keywords: Energy efficient optical network; Free space optics; Hybrid fiber FSO; Information and communication technology; Integrated SMF/FSO; TWDM PON.

Fig. 1

Proposed dual-rate dual-link hybrid FSO/SMF architecture

Fig. 2

Downstream and WDM overlay transmission through a FSO link

Fig. 3

Downstream and WDM overlay transmission through a SMF link

Fig. 4

Dynamic wavelength allocation to different ODNs for FSO communication (a: f_c = 193.1 THz, b: f_c = 193.2 THz, c: f_c = 193.3 THz, and d: f_c = 193.4 THz)

Fig. 5

Dynamic wavelength allocation to different ODNs for SMF communication (a: f_c = 193.15 THz, b: f_c = 193.25 THz, c: f_c = 193.35 THz, and d: f_c = 193.45 THz)

Fig. 6

a Transmission of downstream data through both FSO/SMF with simultaneous FSO broadcasting. b Transmission of downstream data through both FSO/SMF with simultaneous SMF broadcasting

Fig. 7

a Point to point FSO communication in upstream direction. b Point to point SMF communication in upstream direction

Fig. 8

Spectrum of transmitted and received signals at OLT and ODN(s)

Fig. 9

Time-domain representation of transmitted and received signals for FSO and SMF

Fig. 10

BER performance for FSO and SMF link for narrowband and broadband transmission

Fig. 11

Energy saving (%) of proposed architecture w.r.t. pure FSO link for different weeks of a month

Fig. 12

Energy saving (%) of proposed architecture w.r.t. pure SMF link for different weeks of a month