Hi Everyone,
Let's have a brief comparison about Passive Optical Networks: GPON vs EPON
Increasing bandwidth requirements is a common challenge being faced by all Internet Service Providers (ISPs). To fulfill BW requirements, fixed network ISPs are shifting from conventional copper based network (i-e xDSL & WLAN) to Optical Fiber Cable (OFC) based network of FTTx to manage the bulging traffic and enhance customers’ user experience. Passive Optical Network (PON) uses low-power consumption components which eliminates power feeding issues to distribution and access network. In a nutshell, PON technology results in high bandwidth, lower latency, high efficiency, power saving and last but not the least, high network security in comparison to conventional technologies.
Basic Elements of PON:
PON has three primary elements in its network: Optical Line Terminal (OLT), Fiber Distribution Hub (FDH) & Optical Network Terminal (ONT). OLT is installed in Central Office (CO) or Central Exchange of the ISP. It acts as an aggregating equipment to aggregate the traffic from distribution hubs for onwards routing to Transmission network. FDHs or ODN are basically splitters of the feeder OFC that distribute the traffic to and from End users. Lastly, ONT (also referred as ONU- Optical Network Unit) is an end user devices installed at customer premises.
On the basis of architecture, PON is usually divided into two type: Gigabit PON (GPON) & Ethernet PON (EPON). Former works on Asynchronous Transfer Mode, whereas, latter works on Ethernet principles of IEEE. Furthermore, EPON is standardized by IEEE 802.3 and being used widely in Asia. On the other hand, GPON uses ITU-T G.984 framework and widely deployed in Europe, North America, Australia and Middle East. The key architectural difference of EPON & GPON lies in implementation of physical & data link layers. EPON uses the Ethernet frame to transmit traffic where downstream MAC layer has the same operation as a Gigabit Ethernet MAC to broadcast the traffic to all users. On other hand, GPON is supported by two layers i-e the Ethernet frame which is encapsulated in GPON Encapsulation Method (GEM) frame which is further encapsulated in GPON Transmission Convergence (GTC) frame.
Difference between EPON & GPON:
As discussed earlier, there is no major difference between EPON and GPON in terms of utility. However, the difference lies in standards being used i-e bit rate or Speed, split ratio, internet protocol being used and Quality of Service (QoS). Firstly, EPON Uses same bit rate of 1.2Gbps for up as well as for down steam, whereas, GPON uses different bit rates i-e 1.2/2.4 Gbps for downstream and 1.2/1.5/2.4/6.2 Gbps for upstream. Secondly, regarding wavelength, upstream wavelength is 1260-1360nm for EPON and 1290-1330 nm for GPON. Thirdly, EPON allows OFC split ration of 1:16, whereas for GPON, it is 1:64. Fourthly, EPON uses Ethernet protocol, whereas, GPON uses ATM. Lastly, QoS is not supported by EPON but is supported by GPON.
Advantages & Disadvantages of EPON & GPON over each other:
Both GPON and EPON come with their own Pros & Cons over the other technology. GPON is better than EPON in terms of data rate, QoS (as GPON divides bandwidth into four types: Fixed, Assured, Non-Assured, and Best Effort) and network security. Whereas, EPON has several advantages in terms of initial cost (CAPEX) required for its deployment. GPON CO equipment (i-e OLT & cards) are FPGA (Field Programmable Gate Array) based that are expensive than that of EPONs. Normally, it costs 1.5 to 2 times higher for GPON in comparison to EPON. Nevertheless, Pros & Cons of each technology is kept in mind in finalizing the strategy to go ahead with any of both.
Thank You for reading.
References:
1. The next generation of passive optical networks: A review: Article in Journal of Network and Computer Applications: Mark A Gregory, Huda Abbas - March 2016
2. A Comparison of Dynamic Bandwidth Allocation for EPON, GPON, and Next-Generation TDM PON Björn Skubic, Ericsson Research
3. Ragheb and H. Fathallah, "Candidate modulation schemes for next generation-passive optical networks (NG-PONs)," in High Capacity Optical Networks and Enabling Technologies (HONET), 2012 9th International Conference on, 2012, pp. 226-231.
4. Techno-economical comparison between GPON and EPON networks Conference: Innovations for Digital Inclusions, 2009. K-IDI 2009. ITU-T Kaleidoscope:
