# Design of Novel Fiber Optical Flexible Routing System
## 1 Introduction  
In today's era, there is an explosion of information and the amount of transmitted network data is growing at a rate of 7% to 20% per month. Because fiber-optic networks meet this high-capacity communication requirement, they are the backbone of present, and next-generation, high-speed networks. As the demand for wavelengths of optical communication signals continues to increase, the number of fibers laid in adjacent network nodes has also increased. Systems containing reconfigurable optical add/drop multiplexers (ROADMs) and optical cross-connects (OXCs) have generated a large number of development requirements [1; 2; 3]. Dense wavelength division multiplexing (DWDM) technology has also been developed. Each optical fiber can transmit hundreds of wavelength channels simultaneously, and each wavelength channel can carry several gigabits per second. Due to the rapid development of the Internet of Things (IoT), network traffic will continue to increase, coupled with the popularity of mobile internet, and the continuous introduction of new 4 k/8 k high-definition audio and video services, these applications will increase the number of fibers required in each adjacent network node. Especially in densely populated metropolitan areas, network traffic is growing much larger than the core networks [4]. Therefore, the mutual application of ROADM and OXC has been widely discussed [5; 6]. In addition, an optical component for expanding or contracting the number of each fiber channels is called an optical interleaver. Optical interleavers that can be used to separate or combine odd and even channels are also widely used in DWDM applications [7], which is one of the key components of the DWDM system [8; 9]. The interleaver can be used to merge two sets of DWDM channels. In other words, reducing the channel spacing can double the number of optical signal channels per fiber. By using optical interleavers, existing DWDM systems can increase the amount of channels that can be transmitted, which can increase network utilization [10; 11]. On the other hand, it can double the channel spacing of the original DWDM and allow the existing network system to connect smoothly to the new network system [12; 13]. The optical network of metropolitan area networks (MANs) are mainly concentrated in metropolitan areas, and are used to connect the local central office (CO) and various network nodes. That is, to establish a high-speed broadband optical network in the most densely populated metropolitan areas. In addition, for multimedia applications, online shopping, video services, video calls, and video transmissions, it is more advantageous to use DWDM features to increase bandwidth for metropolitan areas that require relatively large bandwidth services. However, the main difference between the metropolitan area networks and backbone networks is that the DWDM systems of the long-distance backbone networks are all peer-to-peer network architectures, and the metropolitan DWDM network systems are a large number of data transmissions between the network nodes. Therefore, OXC and ROADM are the key technologies for signal wavelength switching between these optical network nodes. The all optical fiber network has gradually matured in recent years, especially in backbone networks. DWDM technology has the function of effectively expanding the transmission capacity and distance of networks [14]. Although DWDM technology can effectively expand the transmission capacity of a single optical fiber, but it can only be used on long distance point-to-point architectures. When the network architecture is more complex, it requires the help of optical add/drop multiplexer (OADM) and OXC to complete the network construction [15]. However, to add or drop optical signal wavelengths in a traditional OADM, the system power budget must be calculated, resulting in an increase in cost, and an increased likelihood of occurrence of errors. With the evolution of optical communication technology, the ROADM has matured over the last few years [16].