Small Outdoor OLT Cabinets for Rapid FTTx Deployment

With the ongoing copper-to-fiber migration, fibers are deployed even closer to the user's homes, and accordingly the OLTs in FTTx networks have been brought closer to users. Small-capacity OLTs and auxiliary outdoor cabinets are popular with users due to their small dimensions, light weight, budget friendliness, and efficient deployment. Small-capacity OLTs usually account for approximately 80% of the total OLT deployment, and small-capacity outdoor sites approximately 80% of the total outdoor site deployment.

Outdoor Sites Have Extensive Applications

In order to narrow the digital divide between urban and rural areas and achieve ubiquitous access, some countries have launched rural broadband plans, such as Thailand's Village Broadband Internet Project and Egypt's Decent Life Initiative. Some countries provide free Wi-Fi to remote areas. The operators are more and more concerned about the coverage in suburban, rural and remote areas where there is a relatively small population dispersed over a large area, and a need for a large number of sites. With more flexibility, small outdoor OLTs are more applicable to delivering access to remote and rural areas.
Urban areas, with a high user density and a large population, have always been a battleground for operators, and the broadband penetration rate in urban cores has almost saturated. New commercial buildings and new communities are becoming the focus of the competition. New entrant operators focus on making breakthroughs through rapid network deployment while incumbent operators are looking for ways to reuse existing site resources, such as mobile base stations or fixed network access sites, to achieve rapid and economical deployment of new sites. In either scenario, small outdoor sites have absolute advantages. 

Challenges and Requirements for Outdoor Site Deployment 

Harsh natural environments pose a great threat to outdoor sites. For example, outdoor sites must withstand high temperatures, high solar radiation, high dust, and devastating dust storms in a tropical desert climate, and high temperature, high humidity, high salt fog corrosion, frequent thunderstorms, and ultra-strong typhoons in tropical oceanic regions. 
Limited deployment space and prolonged deployment time due to land acquisition and civil works are engineering risks frequently encountered by operators. Complicated engineering and installation operations such as trench excavation and fiber splicing that can only be completed by professional personnel increase the difficulty and expenditure of deploying outdoor sites. 
In rural and remote areas, there are a large number of sites in actual deployment, which is highly sensitive to costs. In addition, the installation and maintenance difficulty should be minimized due to inconvenient transportation. Some sites may be deployed in the areas with unstable electrical grids and frequent power outages, and the outdoor sites need to provide stable power supplies and sufficient batteries to the main equipment they accommodate. 
In urban areas, operators need to rapidly deploy sites with scalable capacity. In addition, they need to effectively use existing resources to save investment, for example, retaining VoIP services while supporting differentiated services, and reusing the original optical cables, power cabinets, and even cable distribution resources during the upgrade of legacy sites. 
It can be seen that an ideal small outdoor cabinet should not only meet the common challenges faced by outdoor sites but also the differentiated requirements of urban and rural scenarios. 

Light Cabinet Solution

Based on years of experience in access network deployment, ZTE provides the Light Cabinet solution to customers to implement economical and efficient deployment of small-capacity outdoor sites. This solution has four highlights: light, reliable, reusable and sustainable.
Light 
The rapid deployment of light cabinets helps customers save initial investment. ZTE's small OLT cabinets use an aluminum enclosure with outstanding anti-corrosion performance and is at least 30% lighter than the galvanized iron cabinet of the same dimensions. They support flexible installation modes such as pole-mounted and wall-mounted installation. Although light in weight, they provide complete functions such as structural division and support, power supply, power distribution, backup, monitoring, cable distribution, and temperature control, and support one-stop deployment. ZTE's smallest fixed network access cabinet EC100 is very light, and can be pre-connectorized, free from the dependence on professional splicing technicians, further compressing the cabinet installation time and saving manpower, logistics and engineering expenditures. 
The "light" feature is also reflected in lightweight operation, low power consumption and low noise. ZTE's small OLT cabinets based on the green design principle use ZTE's in-house developed high-efficiency folded-plate heat exchanger and organ-pipe type heat exchanger, which, when combined with the adjustable fans, and the intelligent speed adjustment strategy designed and optimized for the main equipment, can minimize the power consumption and noise while dissipating the heat inside the cabinets. When the cabinets accommodate no more than 16 PON ports, the cabinets use natural cooling, which can meet the requirements of ETS 300 753 Class 4.1E protected-area level.
Reliable
To address harsh natural environment challenges, ZTE's outdoor cabinets are specially customized to meet the requirements of extreme climatic environments, such as high temperature, high humidity, and high salt fog corrosion. 
The heat dissipation system of the cabinets ensures that the equipment can operate properly at 50 degrees Celsius in direct sunlight. The cabinets have an enclosed architecture, and the internal and external circulation are separated to effectively prevent corrosive air from entering the cabinet. The customized double-layer aluminum enclosure and hot-dip galvanized installation kits greatly improve the anti-corrosion performance of the cabinets. The IPX5 rating can resist the super typhoons and thunderstorms in tropical areas. The addition of anti-condensation sponge and sealing strips can more effectively prevent the equipment within the cabinet from moisture. The cabinets with surge current ratings up to 50 kA can also withstand level-17 super typhoon or Category 4 hurricane, much higher than the level-14 typhoon or Category 2 hurricane specified in the industry. The cabinets also integrate a IK10 anti-vandal structure. 
Reliable power supply is also very important to outdoor cabinets. ZTE's small-capacity outdoor PON OLT cabinets use high-performance power units, which support wide-amplitude input voltages, fault alarm and automatic recovery, and remote monitoring and protection of battery against abnormalities. The cabinets also support flexible options of lead-acid batteries and lithium-ion batteries, and flexible configuration of the battery capacity. 
Reusable
For the operators with existing outdoor sites, deploying FTTx networks with the existing resources effectively saves investment. ZTE's small-capacity outdoor PON OLT cabinets can use power supply resources of the existing sites. The cabinets can be wall-mounted or pole-mounted, facilitating in-situ installation. In particular, the fly-weight EC100 cabinet supports an ultra-wide pole diameter range of 60-380 mm, allowing for the installation on the same pole and tower with the mobile BBUs or the installation with existing cabinets on a utility pole.
The cabinets can also be reused. ZTE's OLT cabinets in the existing network can be smoothly upgraded to support XGS-PON services only with the upgrade of the heat dissipation performance and adaptation of the power system. The lead-acid batteries in the old cabinet can also be upgraded to li-ion batteries through the reconstruction of the battery compartment. 
Sustainable
In the access network projects of several countries, the small outdoor cabinets customized to the sustainability requirements of the operators are favored for their capacity scalability and equipment integrability. 
For example, the EC70E cabinet supports up to 64 GPON ports/32 XGS-PON ports, 24-core fiber uplink and 120-core fiber downlink, and the battery capacity can be configured flexibly. All of ZTE's small cabinets are designed with scalability, supporting the ODF capacity redundancy of 50%﹣85%, 1+1 redundancy backup for the power rectifier, heat dissipation of high-power XGS-PON cards, and 2﹣5.2 hours of backup power when the equipment operates in its full configuration.
ZTE also provides specially designed small cabinets that integrate optical splitters, video multiplexers, and OTDR. Flexible support of devices allows flexible deployment based on the operator's existing network conditions, thus saving deployment costs. 

Summary

Lightweight is a direction for solving problems in deploying outdoor sites. Safe and reliable outdoor cabinets can cope with harsh environments and save maintenance costs in rural and remote areas. Reusable existing site resources, scalable cabinet capacity, and flexible device integration can help operators deploy outdoor sites rapidly in urban areas. 
In addition to the small-capacity OLT outdoor cabinets, ZTE can also provide end-to-end FTTx series products covering the EMSs, cabinets, OLTs, ODNs and ONTs to meet the overall network construction requirements of operators.