Background:
The increasing need for high speed connectivity and seamless data flow to Data Centre and Integrated Command and Control Centre (ICCC) is driving the demand for providing city wide fiber networks. In India this demand is being further propelled by the Governments Digital India Campaign which includes initiatives such as Smart Cities mission, Bharatnet etc. Optical Fiber Cables plays a crucial role in enabling services such as CCTV video surveillance and security, Smart Traffic management, Smart lighting, Smart parking, Smart monitoring and control of water supply, sewerage and drainage, Waste management and many more applications required for cities.
Optical Fiber Installation Techniques:
There are various methods of fiber deployment, where cable installation in heavily influenced by the development level of the area, environment, population density and business operations. There are primarily two techniques for installing OFC cables in city area: Aerial, Underground.
Aerial installation includes the deployment of cables on utility poles or specially designed fixtures. These cables carry the risk of continual tension caused by wind, temperature changes and the weight of ice in cold regions. Special installation techniques are used for this type of installation as most OFCs are not strong enough to withstand these forces.
Another way to install OFCs is by installing them underground. This method is particularly useful in urban areas for cross-country cabling. The OFC is installed at a specific depth underneath the earth’s surface. This can be done either by burying it directly in the ground or placing the fibre cable in a duct buried underground. OFCs that are directly buried usually have multiple layers of metallic-banded sheathing to tolerate heat, conductivity, and moisture and soil acidity. Installation through ducts is mostly seen in highly urbanized areas. It involves digging where the OFCs are to be placed in installed ducts. The cables are pulled in the conduit, which is buried underground to a depth of more than 1.5 meters. These ducts protect the cables and make fibre cable expansion easier.
OFC Network topology:
The OFC Network in City will have distributed architecture and will have three rings and their termination:
Access Ring: The Access ring are street or Junction rings which are formed using a pair of Optical Fiber and Industrial Grade Ethernet switches placed at each Junction / Point of Presence (PoP) and other ICT based sensors / devices in future. These rings will normally not span more than 5 to 8 Kms and would be of 1 Gbps capacity and connects around 6 to 8 nodes as per location. 1 Gbps Single Mode Fiber SFPs will be used in Access Rings. These rings would be terminated on Aggregation nodes.
Aggregation Ring: These Aggregation rings function as a second hierarchy ring in transport network. Each Aggregation ring will have multiple Access Rings terminated These rings will normally not span more than 12 to 15 Kms in length and are of 2x10 Gbps capacity with scalability in future. These Rings are formed using pair of optical fiber cable and Aggregation Routers. Aggregation Rings will have maximum of 4 to 5 Aggregation Nodes in a single ring. 10 Gbps Single Mode Fiber SFPs will be used in Aggregation Rings. These rings would be terminated on Core nodes.
Core Ring: These Rings are formed using pair of optical fiber cable, Core Routers & DWDM Equipment. These rings would be terminated on Network Operation Centre (NoC) / Data Centre Routers. Normally in a city 3 to 4 Core Nodes are planned and all the nodes are connected in mesh topology to give high level of redundancy in the event of cable faults. The Core nodes are usually of 100 Gbps capacity and will be formed using extended range (ER) SFP Modules.
Basic functioning of captive City OFC Network:
The Core Ring 100 G Network forms the basis for connecting CCTV Cameras requiring high bandwidth and data transmission to Data centre and ICCC. The transport underlay of the network is based upon MPLS data plane with Segment Routing (SR) capabilities provided by ISIS routing domain. Segment Routing technology will distribute the segment (labels) for node and no other signalling protocol will be used (LDP or RSVP for label generation). BGP is enabled for overlay technologies such as L3VPN, EVPN, and mVPN. Topology independent Loop free Alternate (T1-LFA) is enabled in the underlay network to achieve the highest degree of resilience and service availability. Network Level and service level QoS is deployed on all nodes to ensure the expected behavior of packet delivery in the event of network congestion.
Conclusion:
Given the increasing importance of City surveillance and efficient traffic management the importance of City wide captive Optical Fiber Networks as part of city infrastructure have become crucial for cities. Besides planning for road, water, sewage and other infrastructure for any city, the OFC infrastructure should be planned and implemented by City authorities. This infrastructure can make the cities truly smart as it shall enable various citizen centric services monitoring and control on real time basis and its visibility to the citizens also.