تجزیه و تحلیل عملکرد شبکه گسترده نوری فیبری با استفاده از روتر SDM / WDM

A spatial division multiplexing/wavelength division multiplexing (SDM/WDM) router has been designed for a fiber optical wide area network (WAN). The router includes a 32 × 32 optical switch and eight 1 × 4 demultiplexers (DeMUXs) and eight 4 × 1 multiplexers (MUXs). The system performances for various spans and transmission speeds are simulated and compared with the results of analytical calculations. Both the LiNbO3 and semiconductor optical amplifier (SOA) switches for the dilated Benes switch configuration are studied. The simulation results show that the SDM/WDM WAN using the SOA based router performs better than the LiNbO3.

Array waveguide routers (AWR) for applications in wavelength division multiplexing (WDM) optical fiber communication networks have received significant attention recently [1], [2], [3], [4], [5], [6], [7], [8] and [9]. The schematic diagram of the traditional WDM AWR is shown in Fig. 1(a). However, as the channel number increases, the size of array waveguide grating (AWG) becomes too large, that may reduce the production yield and increase the manufacturing cost. Moreover, as the number of wavelengths increases in a single mode fiber (SMF), the nonlinear effects become more severe [10] including four-wave mixing [11], cross-phase modulation [12], self-phase modulation, stimulated Raman scattering [13] and [14], and stimulated Brillouin scattering [15]. These nonlinear effects degrade the network performance that is difficult to recover by changing other system parameters. Therefore, reducing the wavelength numbers in an SMF is an easy and practical way for the actual fiber network design. Full-size image (29 K) Fig. 1. Schematics of (a) traditional WDM AWR and (b) proposed SDM/WDM AWR. Figure options But, how to keep the same capacity with less wavelength numbers in a fiber-optical wide area network (WAN)? The spatial division multiplexing (SDM) would be a good solution. In this paper, we propose an SDM/WDM router using eight 1 × 4 demultiplexers (DeMUXs) and eight 4 × 1 multiplexers (MUXs) as shown in Fig. 1(b). The reason we adopt eight 1 × 4 DeMUX and eight 4 × 1 MUX is that the two elements are the most popular WDM components with low cost and easy for mass production using both of AWG technology and thin film filter technology. Up to now, the LiNbO3 switches are the commercially available product in the fiber optical communications market. The optical crossconnect (OXC) using LiNbO3 switches for add/drop has been reported [16]. Although other switches using semiconductor optical amplifier (SOA) are not yet commercialized, several studies have been carried out to show their performance improvement. The OXC optical add-drop multiplexer (OADM) using SOA switches were also reported with a promising potential [17]. In this paper, two optical switches – LiNbO3 switches and SOA switches – are examined for a 32 × 32 optical switch in the proposed SDM/WDM router. The dilated Benes [18] optical switch configuration is used for designing the 32 × 32 optical switch. The schematic diagram of the designed optical network using SDM/WDM router with LiNbO3 or SOA switches is shown in Fig. 2 where the filters enclosed by slash lines are used only with the SOA switches. Full-size image (59 K) Fig. 2. Schematic of designed optical networks using SDM/WDM router with LiNbO3/SOA switch. Figure options Although the fiber span in WAN is about 40–120 km, the dispersion effect degrades the system performance, especially for high data rate transmissions. The dispersion management has been demonstrated to improve the dispersion effect in a long distance fiber transmission system [19]. Therefore, a fiber network with positive and negative dispersion coefficients before and after the SDM/WDM router is considered in this paper for future higher speed WAN. The remainder of this paper is organized as follows: Section 2 describes the mathematical formulation of the switching network performance with bit-error-rate (BER) analysis. The dilated Benes switching networks based on LiNbO3 and SOA switches are analyzed and simulated in Section 3. Finally, some concluding remarks are provided in Section 4.

This paper proposes an SDM/WDM router for a fiber optical WAN with simulation studies. The router includes a 32 × 32 optical switch and eight 1 × 4 DeMUXs and 4 × 1 MUXs based on the dilated Benes configuration with LiNbO3 or SOA switches. To evaluate the system performance, the commercial software simulations and the analytical calculations for the designed router are conducted, with various spans and different transmission rates. The dispersion effects of single mode fibers before and after the SDM/WDM router are also considered. Through the simulation studies, the increase in the fiber span may cause a higher received power requirements to maintain the same BER performance for both LiNbO3 and SOA switches. In addition, the comparison shows that the SDM/WDM WAN using SOA switch has a better performance than the LiNbO3 switch. In the future work, we expect to design 128 × 128 switching networks.