Cai Jingzhe: The Combo PON solution will become the optimal choice for operators
High-bandwidth services including 4K/8K television, 3D gaming, live interaction, Virtual Reality (VR) and Augmented Reality (AR) have been growing exponentially over the last few years. Faced with fierce competition and driven by national broadband policies, operators are accelerating broadband network deployments. As higher bandwidth is needed, GPON, which is currently a major broadband technology, is increasingly unable to meet the bandwidth demand of the ever expanding high-bandwidth services. To enhance user experience and create new value points, operators need a new technology that delivers higher bandwidth and better services.
When upgrading GPON to 10G GPON, operators have to consider a number of factors, including the reuse of the existing resources, fast deployment, and forward/backward compatibility in order to save the overall cost of the network and meet customers’ requirements at the same time. Furthermore, in order to cater to the continuous development of services, the network needs to be planned and constructed/upgraded in advance.
At present, operators are quickening the pace to deliver 100 Mbps broadband to users and are devoting major effort to providing video services, deploying 1000 Mbps-to-premise pilot trials at an accelerated pace and expanding the application range. Delivering 1000 Mbps to premises has become the next target of broadband acceleration.
As a commercially mature technology, 10G GPON technology perfectly meets operators’ needs by providing higher bandwidth to enable service growth. Most operators have begun to explore solutions for upgrading GPON to 10G GPON in at a low-cost, flexible and fast fashion.
CHALLENGE ANALYSIS OF THE UPGRADE FROM GPON TO 10G GPONThere are two methods in upgrading to 10G PON, one being from EPON to 10G EPON and the other from GPON to 10G GPON.
Featuring outstanding compatibility and supporting flexible access of EPON ONUs and 10G EPON ONUs under the same PON port, the upgrade from 1G EPON to 10G EPON is convenient. The operator only needs to add a 10G EPON line card on the OLT side, and then add a 10G EPON line card on the ONU side – the ODN doesn’t need to change.
External WDM1r is considered the traditional method of upgrading GPON to 10G GPON. The advantage of this solution is that only an external WDM1r needs to be added in the ODN network. It’s also easy and fast to migrate from GPON to 10G GPON. According to the related factors such as network resources, when using the external WDM1r solution, a new OLT shelf, 10G GPON line card, external WDM1r, jumper fibre or even other attached resources such as an ODF may be required. There is a risk that the existing network cannot be upgraded. This might be for the following reasons:
- It requires adding an OLT or line card, upstream link, and upper-layer interconnection device and port, which places higher demands on the equipment rooms’ auxiliaries including space, power supply and more. However, the existing equipment rooms may not be able to meet these requirements
- The external WDM1r solution requires adding a multitude of WDM1rs’ and adding OLT racks or an ODF, which brings internal fibre storage problems. However, the existing network deployment may not able to meet these requirements
- The introduction of WDM1r adds an insertion loss of 1 to 2 dB, while the planned and actual ODN power budget allowance may be insufficient. Imprudent and improper upgrades may interrupt existing GPON services or even disable the upgrade; therefore the existing power budget should be calculated precisely before the upgrade
- The introduction of new passive devices requires adjusting the fibre routing and distribution, which makes the network management, operation and maintenance (O&M) much more difficult
COMBO PON ENABLES ON-DEMAND AND LOW-COST UPGRADE FROM GPON to 10G GPON
Combo PON combines GPON and 10G GPON wavelengths within one optical transceiver module, transmitting and receiving GPON and 10G GPON signals separately. It is compatible with existing GPON services, supports high-bandwidth services, and reuses existing network equipment and ODN resources without the need for altering existing network resources or occupying additional equipment room space. It supports replacing user-side ONUs as per service package to implement rapid and smooth service upgrade. The diagram below shows Combo PON implementing simultaneous access of GPON and 10G GPON.
The Combo PON solution enables a smooth upgrade to high-bandwidth services simply by replacing the line cards. Compared with the external WDM1r solution, the Combo PON solution has the following advantages:
The Combo PON solution does not require additional external equipment and auxiliaries, dramatically reducing the equipment footprint. For example, when upgrading a rack that is fully loaded with two GPON OLTs to 10G GPON, the Combo PON solution saves more than 60% of the equipment room space. In addition, no additional equipment means fewer O&M problems.
Reduced equipment room space and simplified O&M
The cost of 10G GPON ONUs is much higher than that of GPON ONUs. By leveraging the Combo PON solution, carriers can upgrade the ONUs as needed. This enables an asset-light upgrade to 10G GPON, avoids heavy investment in directly deploying 10G GPON ONUs, and achieves ROL.
Less initial investment and quick rate on line (ROL)
Smooth network evolution without affecting the current GPON services
Massive rollout of GPON services may lead to a tight optical power budget for some regions and users. The external WDM1r solution introduces an additional insertion loss of 1 to 2 dB, which may degrade the in-service GPON ONUs ability to work properly and thus affect the existing services. The Combo PON solution leverages a built-in WDM to ensure that the GPON and 10G GPON optical power budget is within the normal range, and in turn ensures that the existing services are not affected.
The Combo PON solution reduces the amount of Central-Office (CO) equipment and auxiliary equipment as well as OLT and ODN resources. Compared with the external WDM1r solution, it saves the construction cost by 26%. The below diagram lists the comparisons between Combo PON and external WDM1r solution.
COMBO PON SUPPORTS BOTH UPGRADE AND NEW-BUILT SCENARIOS
The Combo PON solution suits both GPON to 10G GPON upgrade scenarios and newly-built scenarios. In the initial period of network construction, carriers need to take the construction costs and resources into full consideration, use Combo PON cards on the OLT side, and deploy GPON ONUs to meet low-bandwidth deployment requirements.
When the users’ bandwidth demand increases, carriers can deploy 10G GPON ONUs directly or replace existing GPON ONUs with 10G GPON ONUs and make no change to the OLT side so that the initial investment is controllable and the on-demand migration to 10G GPON is guaranteed.
ZTE is dedicated to providing differentiated, innovative solutions and products that deliver more value to customers. ZTE’s Combo PON solution supports inserting Combo PON cards into the existing OLT chassis and supports the access of both GPON and 10G GPON ONUs. Through tests and verifications, ZTE’s Combo PON solution proves to be satisfactory.
Later, ZTE will provide the Combo PON solution that supports the migration to NG-PON2. With the soaring big video services, the migration from GPON to 10G GPON is unavoidable. It is estimated that the Combo PON solution will become an optimal choice when migrating from GPON to 10G GPON.