# An \(N\)-Port Universal Multimode Optical Router Supporting Mode-Division Multiplexing
## 3 Results
From Figure 10, we can see that the transmission loss of the corresponding port pairs are not much different when the five-port MDM-OR transmits different mode signals. It can be seen from Table 1 that the higher the order mode signals that pass through the multimode waveguide crossing and the multimode bending, the higher the insertion loss will be. However, the multimode switching element we designed can adjust this situation so that the transmission loss between different port pairs in different modes is at an average level. By using the crosstalk noise calculation model proposed in the previous section, we can obtain the crosstalk noise power accumulated on the main signal when different modes are transmitted between different port pairs in the MDM-OR. The specific simulation results are shown in Figure 11. Figure 11 shows the crosstalk noise power accumulated on the TE\({}_{0}\) mode during transmission between different port pairs in the MDM-OR. It can be seen from Figure 11 that when the TE\({}_{0}\) mode is transmitted between different port pairs, the crosstalk noise power accumulated on it is different, and the crosstalk noise power is in the range of (\(-27.21\), \(-21.31\)) dBm. When the TE\({}_{1}\) mode is transmitted between different port pairs in the MDM-OR, the crosstalk noise power accumulated on it ranges from \(-34.27\) dBm to \(-17.45\) dBm. Correspondingly, when the TE\({}_{2}\) mode is transmitted between different port pairs in the MDM-OR, the range of crosstalk noise power is \(-34.19\) dBm to \(-21.55\) dBm. Figure 10: The transmission loss between different port pairs of the multimode router based on the TE\({}_{0}\), TE\({}_{1}\) and TE\({}_{2}\) mode. After obtaining the transmission loss and the crosstalk noise power of different port pairs of the MDM-OR under different modes, the OSNR of different modes can be calculated using Equation (33). In this paper, OSNR is calculated for continuous wave transmission. Figure 12 shows the OSNR when the TE\({}_{0}\), TE\({}_{1}\), and TE\({}_{2}\) mode passes through different port pairs of the MDM-OR. From the figure, it can be found that the OSNR transmitted by TE\({}_{0}\) mode between different port pairs of the MDM-OR is different. In general, the OSNR of the TE\({}_{0}\) mode is excellent, the maximum OSNR can reach 26.37 dB, and the minimum OSNR can also reach 12.49 dB. For TE\({}_{1}\) mode, the OSNR of transmission in this case ranges from 7.19 dB to 32.68 dB. In the five-port MDM-OR, the OSNR of TE\({}_{2}\) mode is also different, among which the maximum value is 32.11 dB and the minimum value is 11.63 dB. According to the obtained OSNR, Equation (33) is used to calculate the BER in different modes. Figure 13 describes the BER of TE\({}_{0}\), TE\({}_{1}\), and TE\({}_{2}\) modes through different port pairs of MDM-OR. It can be found that the BER for the TE\({}_{0}\), TE\({}_{1}\), and TE\({}_{2}\) mode ranges from \(-3.85\) dB to \(-2.10\) dB, \(-4.58\) dB to \(-1.54\) dB, and \(-4.51\) dB to \(-2.10\) dB, respectively. In this paper, BER is calculated according to 10 Gb/s bit rate, and the modulation mode is non-return-to-zero (NRZ). Figure 11: The crosstalk noise power between different port pairs of the multimode router based on the TE\({}_{0}\), TE\({}_{1}\) and TE\({}_{2}\) mode. Figure 12: The OSNR between different port pairs of the multimode router based on the TE\({}_{0}\), TE\({}_{1}\), and TE\({}_{2}\) mode. It is believed that, with research into multimode bending and multimode waveguide crossing and the continuous development of fabrication technology, the insertion loss and crosstalk noise of different high-order modes passing through them will be reduced. Moreover, with the extensive research into mode (de)multiplexer, the corresponding insertion loss and crosstalk noise of mode (de)multiplexing will be further reduced. Therefore, the transmission loss and crosstalk noise of MDM-OR designed by general model will be greatly reduced, and its performance will be greatly improved.