Evolution of Optical Transport
Optical transport net evolved from the traditional Synchronous Optical Network (SONET) and Synchronous Digital Hierarchy (SDH) as the demand for bandwidth increased tremendously over the years. While SONET/SDH served the purpose of transporting telecommunication signals over optical fibers, it lacked the flexibility and scalability required to handle exponential growth in data transmission requirements. Optical transport net was developed with Dense Wavelength Division Multiplexing (DWDM) technology that transmits multiple optical carrier signals with different wavelengths through a single optical fiber. This significantly enhanced the bandwidth carrying capacity of fiber networks.
Key Elements of Optical Transport Network
An optical transport network consists of four main elements - optical line terminals, optical networking units, reconfigurable optical add-drop multiplexers and optical cross-connects. Optical line terminals function as the interface between the optical core/backbone network and customer equipment. They perform aggregation, grooming and encryption of traffic. Optical networking units serve as the customer premises equipment that interfaces with the customer router or switch. Reconfigurable optical add-drop multiplexers allow signals of certain wavelengths to be added or dropped from the fiber backbone without disrupting other wavelengths. Optical cross-connects provide switching functionality within the network to dynamically route wavelengths from input fibers to appropriate output fibers.
Advantages of Using Optical Transport Technology
There are several advantages of deploying optical transport net. Optical Transport Network Firstly, it provides vastly increased bandwidth capacity over legacy SONET/SDH systems. A single DWDM system can carry thousands of Gigabits per second of data traffic. Secondly, it offers high scalability as bandwidth can easily be increased by adding more wavelengths or fiber strands. Optical transport is also efficient as it leverages wavelength division multiplexing to maximize use of fiber infrastructure. Network upgrades are easier as new services can be provisioned without incurring costs of deploying new fiber cables. The use of reconfigurable optical add-drop multiplexers provides flexibility to dynamically route bandwidth based on traffic patterns. Optical switching ensures fast transmission speeds with minimal latency compared to electrical transmission systems. The all-optical architecture is less susceptible to electromagnetic interference.
Driving Massive Change in Telecom Industry
Optical transport net are driving massive changes in the telecommunication industry. Telecom operators are upgrading their backbone infrastructure with DWDM platforms in order to support exploding bandwidth needs arising from 5G, Internet of Things, cloud computing, digital content and video streaming. Optical networks are also playing a pivotal role in building hyper-scale data center interconnect networks. Hyperscalers like Amazon, Microsoft and Google are using Dense Wavelength Division Multiplexing systems to connect their geographically distributed mega data centers with 100GbE and 200GbE wavelengths. Long haul and subsea communications require optical transport solutions for connecting continents and oceans. For instance, Google has deployed trans-Pacific and trans-Atlantic optical fiber networks using network of repeaters and amplifiers to carry terabits of internet traffic every second. Optical transport is also seeing increased adoption in Fiber-To-The-Home deployments to offerultra-high speed broadband access to homes and enterprises.
Future-Proofing Network Architectures
As network traffic demand accelerates, so does the requirement for optical transport capacity. Telecom operators are future-proofing their network architectures using flexible grid optical transport that supports flexible bandwidth variable and flexible spectrum. Flexible grid allows spectrum allocation that precisely matches coherent fiber superchannels carrying 10, 40 or 100 Gbps data rates. It supports efficient switching at sub-wavelength granularity. Higher capacity modulation formats like 64QAM, BPSK and QPSK are increasing spectral efficiency and doubling network capacity.
Networks are leveraging software defined networking (SDN) and network function virtualization (NFV) principles for flexibly managing optical spectrum allocation, automated service provisioning and streamlining network operations. Coherent detection techniques are enhancing transmission reach and superchannel capacities. Advancements in photonics components like Silicon photonics are reducing the cost per bit of transport. Optical transport networks will continue to modernize and play a transformative role in powering the data-driven global economy.
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