# Exploring a New Adaptive Routing Based on the Dijkstra Algorithm in Optical Networks-on-Chip
## 2 Internal Insertion Loss Analysis of ONoCs
### Adaptive Power Control Model  
The output power of the optical transmitter on the link is determined on the transmission loss of the optical switching device, the transmission loss of the waveguide, and the sensitivity of the receiver. According to [26], the optical signal power received from the receiver should not be less than the sensitivity of the receiver. As is shown in (16), \(P_{TX}\) is the output power of the link transmitter, \(L_{SW}\) is the optical transmission loss of the optical switching device, \(L_{WG}\) is the optical transmission loss of the waveguides, and \(S_{RX}\) is the sensitivity of the receiver. In [27], the high-speed optical receiver used was manufactured via Ge waveguide optical detector integrated into a CMOS process. It could achieve the receiver sensitivity of \(-14.2\) dBm operating at 1550 nm and 10 Gbps. In (17), \(P_{TX}\) can be obtained by derivation of (16). In this paper, we optimize the selection of routing path based on the Dijkstra algorithm from the source node to destination node so as to achieve the minimum of the sum of \(L_{SW}\) and \(L_{WG}\). Therefore, on the basis that the receiver sensitivity remains the same, the output power \(P_{TX}\) of the link transmitter should be the minimum.  
\[P_{TX}-L_{SW}-L_{WG}\geq S_{RX} \tag{16}\]  
\[P_{TX}\geq L_{SW}+L_{WG}+S_{RX} \tag{17}\]  
The power of \(s\) node is allocated in terms of the maximum link transmission loss which is obtained from node \(s\) to all destination nodes [16]. The maximum transmission loss of node \(s\) can be calculated as (18), where \(IL^{s}_{max}\) represents the maximum transmission loss of node \(s\); the link transmission loss from source node \(s\) to destination node \(d\) is denoted by \(IL_{sd}\). In traditional power control, the power of each node is equally distributed, which is composed of the largest value among the maximum transmission loss \(IL^{s}_{max}\) of all nodes. The maximum transmission loss \(MaxIL\) among all of the \(IL^{s}_{max}\) is shown in (19).  
\[IL^{s}_{max}=max(IL_{sd})\ for(d\
eq s),d\in(0,N) \tag{18}\]  
\[MaxIL=max(IL^{s}_{max}),s\in(0,N) \tag{19}\]  
In traditional power control [16], each link is allocated the maximum transmission loss. Thus, the transmission losses of many links will be redundant when the actual transmission loss is less than the maximum transmission loss. To solve this problem, the APC technology is applied for link power distribution [20]. For example, in terms of links A, B, and C, we treat \(L_{A}\), \(L_{B}\), and \(L_{C}\) as the maximum transmission losses of the three links respectively. After comparison, we can obtain the maximum transmission loss (i.e., \(L_{A}\)) of the three links. The input power of link B and link C can be adjusted according to link A, and the calculations are shown in  
transmission loss. In spite of APC being able to reduce power consumption to some extent, it still can not solve the problem of the global minimum of network power usage. The Dijkstra algorithm is adopted to select the routing path with minimal transmission loss on account that it has the characteristics of global optimization. Therefore, the output power of the link transmitter can be the minimal on the basis that the receiver sensitivity remains constant.