1. What is XGS-PON?
Both XG-PON and XGS-PON belong to GPON series. From the technology roadmap, XGS-PON is the technological evolution of XG-PON.
Both XG-PON and XGS-PON are 10G PON. The main differences are: XG-PON is asymmetric PON, the uplink/downlink speed of PON port is 2.5G/10G. XGS-PON is a symmetrical PON, the uplink/downlink speed of PON port is 10G/10G.
The main PON technologies in use today are GPON and XG-PON, which are asymmetric PONs. Users' upstream/downlink data is generally asymmetrical, so taking a particular Tier 1 city as an example, OLT's average upstream traffic is only 22% of downstream traffic. Therefore, the technical characteristics of asymmetric PON are basically related to user needs. match. More importantly, the uplink rate of asymmetric PON is low, the cost of transmitting components such as lasers in the ONU is low, and the equipment price is correspondingly low.
However, user needs are diverse. With the rise of live broadcasting and video surveillance services, there are more and more scenarios where users pay more attention to uplink bandwidth. Inbound leased lines must provide symmetrical uplink/downlink circuits. These companies drive the demand for XGS-PON.
2. Coexistence of XGS-PON, XG-PON and GPON
XGS-PON is the technological evolution of GPON and XG-PON, and supports mixed access of three types of ONUs: GPON, XG-PON and XGS-PON.
2.1 Coexistence of XGS-PON and XG-PON
Like XG-PON, the downlink of XGS-PON adopts the broadcast method, and the uplink adopts the TDMA method.
The downstream wavelength and downstream rate of XGS-PON and XG-PON are the same, so the downstream of XGS-PON does not distinguish between XGS-PON ONUs and XG-PON ONUs, and the optical splitter splits the downstream optical signals into Same ODN Link For each XG(S)-PON (XG-PON and XGS-PON) ONU, each ONU chooses to receive its own signal and discards other signals.
The uplink of XGS-PON performs data transmission according to time slots, and ONUs transmit data in time slots permitted by OLT. The OLT dynamically allocates timeslots according to the traffic demand of different ONUs and the type of ONU (XG-PON or XGS-PON?). In the time slot assigned to XG-PON ONU, the data transmission rate is 2.5Gbps. In the time slot assigned to XGS-PON ONU, the data transmission rate is 10Gbps.
It can be seen that XGS-PON naturally supports mixed access with two types of ONUs, XG-PON and XGS-PON.
2.2 Coexistence of XGS-PON and GPON
XGS-PON uses Combo solution to share ODN with GPON because the uplink/downlink wavelength is different from GPON. For the principle of the Combo solution, please refer to the article "Discussion of Solutions for Improving XG-PON Resource Utilization of Combo Subscriber Board".
XGS-PON combo optical module integrates GPON optical module, XGS-PON optical module and WDM multiplexer.
In the upstream direction, after the optical signal enters the XGS-PON combo port, WDM will filter his GPON signal and XGS-PON signal according to the wavelength and send the signals to different channels.
In the downlink direction, signals from GPON and XGS-PON channels are multiplexed through WDM, and the mixed signal is downlinked to ONU through ODN. Due to different wavelengths, different types of ONUs select the required wavelengths to receive the signal through internal filters.
XGS-PON naturally supports coexistence with XG-PON, so XGS-PON's Combo solution supports mixed access of three types of ONUs: GPON, XG-PON and XGS-PON. XGS-PON Combo optical module is also called 3-mode Combo optical module called a module).
3. Market Situation
Affected by equipment cost and equipment maturity, the current equipment price of XGS-PON is much higher than that of XG-PON. Of these, the unit price of OLT (including Combo user board) is about 20% higher, and the unit price of ONU is more than 50% higher.
Although inbound leased lines must provide uplink/downlink symmetrical lines, the actual traffic of most inbound leased lines is still governed by the following behaviors: There are more and more scenarios where users pay attention to uplink bandwidth, but there are few services that cannot be accessed via XG-PON and must be accessed via XGS-PON.
