What is All Optical Network (AON)?

Review of Optical Fiber Communication
Based on industrial view, the development of optical fiber communication has experienced four stages and is now in the fifth stage. In 1970, the emergence of optical fiber with low loss and laser diode operating at room temperature initialized optical fiber communication.

However, the wide application of optical fiber communication was in 1990s. USA government released the plan named “National Information Infrastructure (NII)” in 1993. Optical fiber communication technologies were important parts supporting NII and were developed rapidly. The symbolic technology in the period is DWDM, which expands the transmission capacity of optical fiber communication by tens of times. The development of optical fiber communication slowed down in 2001 with the burst of internet bubble.

Then in 2004, Japan began the wide deployment of FTTH before the emergence of services and contents that require more bandwidth. With the participation of China in 2008, the development of FTTH reached the peak in ~2012. The backbone optical fibers deployed in 2001 was then fully employed.

The fourth symbolic development of optical fiber communication is related to data center. The rapid development of mobile internet promoted the construction of big data centers. Google led the application of optical fiber interconnection in data center in ~2010, which became the second grow point of optical fiber interconnection besides Telecom.

Above is the past four stages of optical fiber communication. 5G is the focus of the world in recent years, which is characterized by high speed, large capacity and low delay. The wireless technologies have enabled the former two. However, the delay of 5G is related to the optical fiber network supporting the base stations. The high speed and wide connection of terminals exhausts the bandwidth of optical fiber communication and results in more delay. The optical fiber network is required to be upgraded and the focus is on metro network. Based on cost consideration, the current metro network is mainly based on CWDM and FOADM (fixed optical add/drop multiplexer) technologies. The DWDM and ROADM technologies for long haul network are expected to sink to metro network.

Structure of All Optical Network
In order to improve the efficiency and reduce the OPEX (operation expense) cost of the optical fiber network, the new generation of all optical network (AON) is required to be software defined network (SDN). The SDN network can be reconfigured based on software setting, exempting from manual operation. ROADM is the key equipment enabling SDN network, as shown in Fig.1. The ROADM-based AON includes three level of networks: long haul, metro and access network. The long haul network connects big cities and is usually constructed as a mesh network. The metro network usually employs fiber ring structure. As the telecom services become diverse and complicated, the metro network extends to be a multiple-ring network, including a core ring and many edge rings. The access network is fed by the metro rings and extends to the vicinity of the end users. The final links between the access network and the users include FTTx (to the business buildings, schools, homes, etc.) and wireless base stations.

Fig.1 Structure of all optical network

The coming 5G application promotes the upgrading of AON. As the key part for AON, ROADM market is expected to increase rapidly, especially in metro network application.

Written by Zhujun Wan, HYC Co., Ltd

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