In China, 100M optical broadband has become popular, and the Gigabit era is about to open. In 2019, the Ministry of Industry and Information Technology launched the “Double G Double Lifting, Same Network Same Speed” action for broadband networks, and continued to accelerate the promotion of fixed broadband Gigabit applications.10G GPON technology can achieve a leap from “hundred megabytes” to “gigabit”. 10G GPON technology refers to technologies such as XG-PON, XG-PON & GPON Combo, XGS-PON, XGS-PON & GPON Combo. The evolution to 10G GPON needs to consider the compatibility issues of various ONUs.
In order to solve the problem that XG-PON is not compatible with GPON ONU, ZTE is the first to propose an innovative technology of Combo PON to realize XG-PON & GPON Combo.At present, this two-speed Combo PON technology has been welcomed by operators because of its good compatibility and convenience. It has become the mainstream solution for 10G GPON construction and is commercially available on a large scale.
Now XGS-PON technology has been mature, and XGS-PON can provide 10G of upstream and downstream symmetric bandwidth, but XGS-PON OLT can only compatible with XGS-PON and XG-PON two kinds of ONU, while a large number of GPON and ONU are deployed in the existing network, and the compatibility of existing network GPON and ONU must be solved when the network evolves to XGS-PON.In order to solve this problem, ZTE proposed a three-rate Combo technology, namely XGS-PON and GPON to implement Combo, which supports smooth upgrade of GPON to XGS-PON.
Three-rate Combo PON technology principle
XGS-PON&GPON’s Combo PON solution is a built-in multiplexer solution that supports XGS-PON/XG-PON/GPON three-mode coexistence.The industry also calls it “three-speed Combo PON”, which is recognized by the industry as the best solution for smooth upgrade of GPON to XGS-PON.
The three-rate Combo PON utilizes the principle of different carrier wavelengths by XGS-PON and GPON technologies, and combines two wavelengths in one optical module to realize independent transmission and reception processing of GPON and XGS-PON optical signals.The three-speed Combo PON optical module has a built-in combiner that can combine the up and down four wavelengths required for splitting XGS-PON and GPON.XGS-PON and XG-PON use the same wavelength, which is an upstream wavelength of 1270 nm and a downstream wavelength of 1577 nm.GPON uses 1310nm upstream wavelength and 1490nm downstream wavelength, and the three-rate Combo PON optical module realizes single-fiber four-wavelength transmission and processing (see Figure 1).
The three-rate Combo PON provides the capability of compatible GPON terminals. Due to the WDM technology, the bandwidth provided by the PON port is the sum of the bandwidth of the XGS-PON and GPON channels.When the three-rate Combo PON port is simultaneously connected to the XG(S)-PON terminal and the GPON terminal, the downlink bandwidth provided by each PON port is 12.5 Gbps (10 Gbps + 2.5 Gbps), and the uplink bandwidth is 11.25 Gbps (10 Gbps + 1.25 Gbps).
ZTE’s three-rate Combo PON solution
ZTE’s three-rate Combo PON board adopts 8/16-port XGS-PON&GPON dual-channel hardware design. One Combo PON port corresponds to two PON MACs (GPON MAC and XGS-PON MAC) and two physical channels (WDM1r is integrated into the optical module). In the downlink direction, the two downlink waves are processed by a separate PON MAC, sent to the optical module for multiplexing, and then sent to different ONUs. The XGS-PON ONU receives the XGS-PON signal, and the XG-PON ONU receives the XG. – PON signal, GPON ONU receives GPON signal.In the uplink direction, GPON and XGS-PON use different wavelengths, filter first in the optical module, and then process in different MAC channels.XGS-PON and XG-PON use the same wavelength and need to perform DBA scheduling on the same channel.
The port number of the Combo PON card is 8 or 16 ports. The appearance and physical interface are one-to-one. This facilitates the daily management and maintenance of the device and the resource management system.When configuring network management data, you need to add a new type of board, and number the GPON, XG-PON, and XGS-PON ONUs to automatically identify the ONU type and adapt the channel.Since a three-speed Combo PON port corresponds to two physical channels, the maintenance management modes are as follows: A Combo PON port includes two physical channels: GPON and XGS-PON. Performance statistics and alarm management need to be extended based on the original MIB (Management Information Base).
Originally accessing information independently for GPON and XG(S)-PON channels, it is necessary to obtain information of two physical channels at the same time.
The MIBs related to other service configurations and operation and maintenance management remain unchanged. They are configured to the Combo PON port, and the Combo PON automatically adapts to the channel.
Leading the trend of 10G PON construction
The three-speed Combo PON can access XGS-PON, XG-PON and GPON three types of ONUs on demand, which can flexibly meet the needs of different operators: XGS-PON can be used for government and enterprise private line users, and XG-PON can be used for Home Gigabit users access, GPON is used for ordinary 100M subscriber access.
Compared with the external multiplexer scheme, the advantages of the three-rate Combo PON are obvious:
No need to adjust the ODN, the project is simple. When an external multiplexer is used, it is necessary to increase the multiplexer device, and it is necessary to adjust the ODN network on a large scale, which is difficult to implement in engineering, which is one of the main reasons why XG-PON is difficult to scale.
The new insertion loss is not introduced, and the problem of optical power margin is completely solved. The use of an external multiplexer will add an additional 1~1.5db insertion loss, which is undoubtedly worse for many optical power budgets that are already tight, and the project cannot be implemented.The three-rate Combo PON does not add extra insertion loss. When the same optical module level is adopted, the Combo PON is introduced, and the optical power budget margin of the ODN network does not change.
Save space in the machine room and simplify operation and maintenance.The three-speed Combo PON optical module integrates functions such as XG(S)-PON, GPON, and WDM1r. It does not add additional equipment and does not occupy additional room space, simplifying maintenance and management.
The OSS is easy to dock, the opening process is unchanged, and the upper line is cut.The three-speed Combo PON adopts the WDM mode. The XG(S)-PON channel and the GPON channel are automatically matched with their terminal types. The existing XG(S)-PON and GPON are connected to the OSS, and the service opening process remains unchanged. Easy to open, the project is easy to cut.
The three-rate Combo PON solution has received a lot of attention from mainstream operators such as Orange, Telefonica and China Mobile.Based on the Combo PON solution and large-scale commercial practice, ZTE actively participated in the three-rate Combo PON test and commercial practice of mainstream operators, and continued to lead the 10G GPON construction trend.