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100G OTN Empowers IDC Backbone Network

Updated on Jul 27, 2022 by
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FS 100G Data Center Switches

In today's digital age, Internet Data Centers (IDCs) face increasing demands for efficient data transmission. To meet these challenges, 100G Optical Transport Network (OTN) technology has emerged as a critical solution. By boosting transmission capacity and leveraging advanced techniques, such as coherent reception and error correction, 100G OTN offers a promising path for optimizing IDC networks. This article explores the key technologies and benefits of 100G OTN, underscoring its significance in advancing IDC infrastructure.

100G OTN Boosting IDC Backbone Networks Development

The rising demand for bandwidth, fueled by cloud services, IoT, and AI, highlights the need for strong network infrastructure. This surge, driven by various applications like live streaming and high-definition videos, has led to increased bandwidth requirements for IDC backbone networks. As a result, OTN bandwidth has become essential for high-speed data transmission. Surveys show internet traffic growth rates surpassing revenue growth rates, prompting efforts to optimize OTN bandwidth usage and lower transmission costs by internet providers and mobile network operators.

Therefore, One of the most effective ways to reduce Total Cost of Ownership (TCO) is to enhance transmission capacity. The completion of the 100G standard and the introduction of OTN equipment have led to significant breakthroughs in this regard. Nowadays, most equipment manufacturers offer a wide range of 100G products to meet the rapidly growing demands for higher data rates and bandwidth in IDC backbone networks.

100G OTN Key Technologies

We will discuss key technologies used in 100G OTN in the following part.

100G OTN Line Modulation

Modulation signal rate has a great influence on 100G OTN network performance since it's closely related to a number of physical limitations that hinder the long-distance transmission of OTN. The higher modulation rate you use, the more susceptible you are to noise or interference. Quadrature Phase Shift Keying (QPSK), a modulation technique, is often used with polarization multiplexing (PM) to reduce the modulation rate of 100G systems.

To be specific, the 100G signal (The bit rate of 100G signal is 112Git/s or higher) is divided into four low-speed signals at the transmitting end. Each signal is 28Gbit/s with OTN and FEC overhead. The light emitted by the laser is decomposed into vertical and horizontal polarization states. PM uses these two polarization states that have the same frequency to carry signals. The optical signal of two polarization states is modulated by QPSK before they're coupled and output together. This can greatly reduce the modulation rate and baud rate, and further reduce the power consumption and cost of IDC backbone networks.

Coherent Reception and DSP

Because polarization state of PM-QPSK optical signals change randomly in long-distance transmission, the frequency and phase of the the local optical oscillator at the receiving end is different from those of the received optical signal. High-speed digital signal processing (DSP) is used to solve this problem since it can process the received signal.

Using advanced DSP compensation technology, the polarization-mode dispersion (PMD) tolerance of 100G system can be greatly improved, reducing the transmission cost incurred by PMD in IDC backbone networks. In addition, there will be higher optical receiving sensitivity.

Out-of-Band FEC Scheme

OTN, an integral component in networking, defines an out-of-band FEC scheme that is applied to the optical signal before transmission. This scheme significantly enhances tolerance to network impairments encountered in high-speed transmissions. Additionally, it efficiently detects and corrects errors in the optical link, thereby greatly increasing system margin for a given Bit Error Rate (BER). By incorporating OTN in networking, it becomes feasible to extend the distance between optical repeaters in IDC backbone networks. This extension not only reduces overall capital and operational expenses but also simplifies IDC network architecture, necessitating fewer amplifier sites.

100G Customer-Side CFP Module

IEEE defines the speed of 100 Gigabit Ethernet (100GE) as 103.125 gigabits per second (Gb/s). Both IEEE and ITU-T specify four physical layer interfaces for 100GE. While the standards for the 10x10G customer side are still being discussed, the Optical Internetworking Forum (OIF) has outlined that the 100G C Form-Factor Pluggable (CFP) customer-side optical module can utilize either 4 wavelengths (4×25G, 100GBASE-LR4/ER4) or 10 wavelengths (10×10G, 100GBASE-LR10/ER10). Notably, the 100GBASE-LR4 CFP and 100GBASE-LR10 CFP have found widespread use in high-speed routers, switches, and client-side components of Wavelength Division Multiplexing (WDM) systems.

Additionally, the 100G CFP client-side module incorporates photonic integration technology (PIC) to achieve a compact form factor and low power consumption. In the realm of 100G WDM/OTN systems, CFP-encapsulated customer-side modules are commonly utilized to access 100GE or OTU4 services, with 100GBASE-LR4 and 100GBASE-LR10 being the predominant options. However, it's worth noting that 100GBASE-ER4 and 100GBASE-ER10 technologies are still in the development phase and require further refinement.

100G OTN

Figure 1: 100G OTN Line-side Service Types

How 100G OTN Empowers IDC Network Construction

Behind 100G OTN's popularity lie a series of crucial benefits it offers. The following illustrates how 100G OTN empowers IDC network construction.

Efficient Utilization of 100G Pipeline

The complete operation, administration and management capability of 100G OTN contributes to the efficient utilization of 100G pipeline. Compared to WDM networks without channel level monitoring and management capability, 100G OTN can realize the active perception of the wavelength channels, and provide level 6 connection monitoring capability, greatly improving network manageability and service security. In addition, OTN can realize hierarchical and segmented channel level management for application scenarios typical in IDC networks where multiple operators and subnets are involved.

Great Protection Mechanism

100G OTN incorporates a diverse array of network-level protection mechanisms, significantly bolstering the reliability and security of IDC networks. These safeguards operate across both optical and electrical layers, including optical line and channel protection, SNCP protection, ODUK 1+1 protection, and ODUk ring network protection. Optical channel 1+1 protection is typically employed for optical layer defense, while ODUK 1+1 protection primarily safeguards the electric layer. Together, these measures effectively minimize service disruptions stemming from component failures and maintain the integrity of the optical transport network with a high level of security.

Differentiated Service Offerings

100G OTN enables network operators to establish, protect, and restore services according to specific SLAs and policies with enhanced programmability. With packet enhanced OTN products, an IDC network can realize unified transmission of TDM and packet services, and have processing capabilities such as ODUk crossover, packet switching, and VC crossover. Therefore, 100G OTN is a great choice to match various service ports and solve multi-service carrying.

Summary

As the 100G OTN industrial chain has already matured, the scale deployment of 100G OTN in IDC networks will become more and more common. In addition, with the maturity of 100G key technologies, IDC networks will deliver smooth and efficient network performance with easy management and high-level security.

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