Intelligent OTN Solution: Enabling Fast and Simplified Deployment of Self-Healing Networks

Recent years have witnessed a booming development within the global ICT sector. The deployment of 5G networks on a large scale is in progress, leading to an explosive surge in network traffic from various applications. Additionally, new technologies like intelligent driving, AI, and ChatGPT continue to emerge, imposing higher requirements on the rate and bandwidth of infrastructure networks. Enhancing digital intelligence of OTN foundational network has become a pressing need for network operators. ZTE has been exploring the realm of OTN intelligence and has introduced its collaborative solution integrating network management and control with WDM/OTN automatically switched optical network (WASON). Additionally, new intelligent technologies such as power balancing and flexible grids have also been unveiled. These efforts are aimed at building highly intelligent transmission networks for customers.

Management and Control Integrated Solution for End-to-End Management and Distributed Control

The traditional OTN management and control approach implements dynamic network restoration and control through a centralized mode. This method, when compared to WASON’s operation on the device side, results in a longer interaction process. This, in turn, leads to increased uncertainty factors, including disrupted signaling channels between OTN management and control and the devices. As a result, stability issues emerge, thereby presenting significant risks in engineering applications. Though the WASON function is stable and supports dynamic restoration, it lacks the global route computation capability, which becomes a bottleneck for supporting large networks with more than 300 network elements (NEs). To leverage the advantages of both, ZTE has rolled out a collaborative solution that combines intelligent OTN management and control with WASON, enabling the management and control to have the route computation capability.

As shown in Fig. 1, the management and control integrated solution utilizes the global perspective of the management and control server for end-to-end service allocation. It hands over the services with restoration attribute to the WASON distributed control, and the services with non-restoration attribute to the management and control server. This approach enables end-to-end management and control, promoting coordinated development of the control plane. Additionally, the WASON distributed control function is used to restore services and improve the operational stability of the control plane. The controller provides centralized route computation to improve the success rate of service restoration.

The management and control integrated solution abstracts the bandwidth supported by each board through the network management system, eliminating the need for manual resource allocation for optical-layer boards. The solution also deploys collaborative services, enabling direct end-to-end cross-layer deployment of OAC services. After deployment, it can generate optical channels (OCHs) while also allowing a one-click removal of services. This simplifies the steps involved in service deployment and removal.  

Automated Power Optimization for Cost Reduction and Efficiency Improvement

The optimization of optical power within the optical power system for traditional OTNs is carried out manually during joint debugging and maintenance phases. This is especially challenging in WASON service restoration scenarios, where the number of routes to be restored can be extensive. Manual operation methods are unable to debug all available paths, demanding a significant amount of human effort. The traditional method of prefabricated paths, due to its inability to cover all possible routes, results in certain risks to network robustness. Furthermore, it is unable to promptly adjust optical power in the event of optical cable degradation, consequently affecting services.

To tackle this challenge, ZTE has implemented an automatic power optimization (APO) solution. Through intelligent algorithms, this solution enables automatic control and optimization of optical power throughout the entire network. Compared with manual calculations and interventions, this approach is closer to optimal values. This not only enhances transmission performance but also reduces the need for extra transmission performance margins, thereby lowering network construction costs.

The APO solution includes a range of functions such as collection and reporting of power detector data, target power preset for the power detector, power parameter setting for the power controller, local automatic optimization of controller power parameters, global optimization of controller power parameters, automatic power optimization of the detector, and automatic channel power equalization.

The APO solution implements network-wide power equalization by overlaying the  power adjustments at both the optical multiplexing section (OMS) layer and the OCH layer. At the OMS layer, when the actual engineering parameters (such as fiber length) do not match the power budget design during network commissioning, or when fiber link attenuation changes during network maintenance, APO enables the system to automatically adjust the attenuation of optical attenuators or the gain of amplifiers. This allows the system to maintain the intended target power budget as designed. At the OCH layer, when individual wavelength channels experience power fluctuations due to factors like fiber connector losses, APO automatically adjusts the attenuation of boards equipped with channel attenuation adjustment capabilities (such as VMUX). This restores wavelength channels with abnormal power levels to their optimal operating points.

During network commissioning, APO’s network-wide power setting and adjustment capabilities can improve the efficiency of new network deployment. Throughout network operation, APO’s real-time intelligent monitoring and network-wide power optimization capabilities can reduce the manpower costs of routine operation and maintenance. In addition, APO can rapidly respond to network power changes, reducing network adjustment time, network degradation duration, and even service failure time. This significantly strengthens network reliability and stability, leading to a substantial improvement in the intelligence of network self-healing capabilities.

In the scenario of WASON service restoration, APO can automatically adjust the optical power of service paths, enabling the WASON network to possess a genuine automatic global exhaustive route computation capability. This greatly enhances network robustness.

Flexible Grids for Self-Intelligence Management

A key concept of a flexible grid is frequency slot, which refers to a spectrum section that meets the definition of a flexible grid as specified in G.694.1. At any given moment, this spectrum segment can be used for only one optical channel and is uniquely defined by its central frequency and slot width. Compared with the traditional fixed grid network, a flexible grid network has the flexibility to select a range of slot widths as required.

In comparison to the traditional fixed-grid network, where all NEs are fixed-grid components, and the spectrum resource management granularity is based on fixed wavelengths, a flexible-grid network offers a different approach. In a flexible-grid network, there's no need for manual grid division in the network management. The network is composed entirely of fully automated flexible-grid NEs. The control plane can dynamically create and remove optical-layer wave channels as required, without human intervention. Resource allocation in a fully automated flexible-grid network is based on fundamental frequency slots, allowing the control plane to efficiently allocate optical-layer resources within its designated spectral range.

• In the 100G+ OTN service scenario, signals with different transmission rates or signals with the same transmission rate but using different modulation modes and coding schemes have different baud rates. This necessitates the use of different channel spacing. The concept of a flexible grid is exceptionally well-suited for accommodating this mix of various channel spacing requirements in transmission. It can dynamically allocate spectrum as needed, leading to efficient spectrum utilization and conservation of spectral resources.
• In the WASON service restoration scenario, fixed grids need to manually configure all ports of WSS and OPM spectrum analysis boards on the working and restoration routes. When a large number of alarms occur on idle network ports, the typical practice is to suppress these alarms. However, in cases where WASON services need to recover due to factors like optical cable interruptions, the previously idle ports become active for the restoration path. In such situations, it’s challenging to manually and promptly remove the alarm suppression from these parts, which can lead to a problem of real network alarms being overlooked. In contrast, flexible grids can automatically enable the ports on the route taken by the service through WSS and OPM spectrum analysis boards. When the service route changes, the system automatically removes these ports, ensuring that network alarms are always visible throughout the process. This feature makes network maintenance more convenient.
• In a fully automated flexible grid scenario, during the optical-layer end-to-end service provisioning phase, the system can automatically identify and adjust parameters related to service boards and the optical channel’s spectral width. This eliminates the manual configuration steps for individual network WSS bandwidth and OPM spectral analysis board ports, simplifying network deployment. In the network maintenance phase, WASON services can automatically enable WSS and OPM ports on new recovery routes, and idle ports are automatically removed when the services are restored. This advanced capability facilitates autonomous network management.

Intelligent Applications

ZTE and a Turkish mobile operator collaborate for the first time to implement a simplified deployment of OTN networks using a combination of intelligent solutions. This deployment encompasses the management and control integrated services, enabling OMS APO and OCH APO functionalities, with all scenarios based on flexible grids.

In the network deployment phase, there’s no need for WSS channel setting, EOPM channel setting, or OA board resource allocation, resulting in a workload reduction of over 40% for single-point network configurations. The system automates optical power adjustments, boosting end-to-end service activation efficiency by over 70%.

In the network maintenance phase, APO can automatically adjust the power of the optical system in real time, achieving intelligent network self-healing and greatly reducing the network management and maintenance costs.  

In terms of network evolution, the use of flexible grids enables the system to automatically allocate resources when transitioning to different service bandwidths, such as 400G in the future. This facilitates significant network scalability and growth.

ZTE’s OTN intelligent applications come with distinct advantages in saving manpower and time costs, improving network maintenance and management efficiency, and promoting network scalability. The intelligent OTN solution is expected to be widely used in future network construction and optimization, helping customers achieve rapid and simplified network deployment, along with intelligent self-healing capabilities.