Technologies to Facilitate Metro Network Upgrade to 100G

Updated on Feb 3, 2023

FS 100G Portfolio

With the rapid development of Internet technology, various new applications emerge, increasing the demand for network bandwidth and driving network upgrades to high-speed 100G Ethernet. The same goes for metropolitan area networks, which require more channels operating at higher data rates. Migrating to 100G metropolitan area networks faces many challenges, but there are some cutting-edge advanced technologies to support 100G metro networks.

Challenges for 100G Metro Network

Affected by factors such as long-distance links and high-density transmission, 100G transmission over metropolitan area networks is very challenging. Below are the challenges facing 100G metropolitan area networks.

Link Loss: 100G metro networks contain a large number of ROADMs, which leads to an increase in loss. Besides, the signal loss may increase due to older metro fiber and numerous connectivity points.

Cost & Density: Since metro networks are usually large in scale, they are more cost-sensitive and require high port density.

Latency: Low latency is critical for high-speed network deployment. Metro networks require low latency to ensure desired 100G transmission quality.

Technology Used in 100G Metro Network

To meet the high-capacity and long-distance transmission requirements of 100G metro networks, advanced DWDM technology and coherent optics are being adopted. Besides, a new signal transmission technology, PAM4, has been developed to provide a new solution for 100G Ethernet connectivity in metropolitan area networks.

DWDM Technology

DWDM is a fiber-optic transmission technique that multiplexes many different wavelength signals onto a single fiber, while maintaining complete separation of the data streams. DWDM can greatly increase the bandwidth and extend the transmission distance of optical networks. Metro deployment of the 100G network requires DWDM components, including DWDM Mux/Demux, optical amplifiers, and dispersion compensators.

DWDM Mux/Demux

The DWDM multiplexer or de-multiplexer is a core optical multiplex technology that puts data from various sources on an optical fiber, each signal traveling at the same speed on its own light wavelength. DWDM Mux/Demux can extend the bandwidth of optical communication networks with low cost and long transmission distance, making it ideal for 100G metro networks.

Optical Amplifiers

Optical amplifiers can overcome the additional losses caused by fiber attenuation, optical power splitting, and other factors, extending the fiber links for long-haul signal transport. For DWDM applications, EDFA is the optimal choice as it provides high small signal gains and output powers.

Dispersion Compensation Modules

The DCM provides chromatic dispersion compensation for long-span transmission fibers, supporting ultra-long 100G fiber transport of metro networks.

DWDM Network

Coherent Optical Technology

For 100G metro networks, coherent optics, especially small pluggable CFP2 and CFP4 modules, have gained widespread attention and adoption because of their optimized performance and size. The basis of coherent optics lies in technologies such as higher-order modulation and coherent detection. In addition, DSP and FEC are also of great significance for enhancing the transmission capability of 100G coherent optical communication systems.

Digital Signal Processors electronically compensate for Chromatic and Polarization Mode Dispersion to enable robust performance and eliminate the need for DCM, making coherent systems commercially viable.

Forward Error Correction (FEC) is a method of reducing data transmission errors, effectively enhancing OSNR and extending the transmission range of high-speed optical systems.

PAM4 Modulation

PAM4 is a technology that uses four different signal levels for signal transmission and each symbol period represents 2 bits of logic information (0, 1, 2, 3). It can increase the transmission rate and reduce signal loss, thus supporting higher capacity and longer distance transmission.

Based on this leading-edge technology, the 100G PAM4 QSFP28 becomes a cost-effective solution for 100G metro networks because of its simplicity and low power consumption.

100G PAM4 QSFP28


The technologies mentioned above make it possible to transmit 100G over long distances across metropolitan area networks. Based on different technologies, various 100G metro network solutions have been developed. However, they may still have some limitations in terms of cost or cabling, and so on. Continuous technological development is required to address these challenges.


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