Tag Archives: GPON

The Latest Generation of PON – NG-PON2

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To meet the large demand for high capacity transmission in optical access systems, 10G-PON (10G Passive Optical Network) has already been standardized by IEEE (Institute of Electrical and Electronics Engineers) and ITU (International Telecommunication Union). To enable the development of future optical access systems, the most recent version of PON known as NG-PON2 (Next-Generation Passive Optical Network 2) was approved recently, which provides a total throughput of 40 Gbps downstream and 10 Gbps upstream over a single fiber distributed to connected premises. The migration from GPON to 10G-PON and NG-PON2 is the maturity of technology and the need for higher bandwidth. This article will introduce the NG-PON2 technology to you.

GPON 10G-PON NG-PON2

What Is NG-PON2?
NG-PON2 is a 2015 telecommunications network standard for PON which was developed by ITU. NG-PON2 offers a fiber capacity of 40 Gbps by exploiting multiple wavelengths at dense wavelength division multiplexing (DWDM) channel spacing and tunable transceiver technology in the subscriber terminals (ONUs). Wavelength allocations include 1524 nm to 1544 nm in the upstream direction and 1596 nm to 1602 nm in the downstream direction. NG-PON2 was designed to coexist with previous architectures to ease deployment into existing optical distribution networks. Wavelengths were specifically chosen to avoid interference with GPON, 10G-PON, RF Video, and OTDR measurements, and thus NG-PON2 provides spectral flexibility to occupy reserved wavelengths in deployments devoid of legacy architectures.

How Does NG-PON2 Work?
If 24 premises are connected to a PON and the available throughput is equally shared then for GPON each connection receives 100 Mbps downstream and 40 Mbps upstream over a maximum of 20 km of fiber. For 10G-PON, which was the second PON revision, each of the 24 connections would receive about 400 Mbps downstream and 100 Mbps upstream. The recently approved NG-PON2 will provide a total throughput of 40 Gbps downstream and 10 Gbps upstream over a maximum of 40 km of fiber so each of the 24 connections would receive about 1.6 Gbps downstream and 410 Mbps upstream. NG-PON2 provides a greater range of connection speed options including 10/2.5 Gbps, 10/10 Gbps and 2.5/2.5 Gbps. NG-PON2 also includes backwards compatibility with GPON and 10G-PON to ensure that customers can upgrade when they’re ready.

NG-PON2 Work Principle

NG-PON2 Advantages
The NG-PON2 technology is expected to be about 60 to 80 percent cheaper to operate than a copper based access network and provides a clear undeniable performance, capacity and price advantage over any of the copper based access networks such as Fiber to the Node (FTTN) or Hybrid Fiber Coax (HFC). At present, three clear benefits of NG-PON2 have been proved. They are a 30 to 40 percent reduction in equipment and operating costs, improved connection speeds and symmetrical upstream and downstream capacity.

Reduced Costs
NG-PON2 can coexist with existing GPON and 10G-PON systems and is able to use existing PON-capable outside plant. Since the cost of PON FTTH (Fiber to the Home) roll out is 70 percent accounted for by the optical distribution network (ODN), this is significant. Operators have a clear upgrade path from where they are now, until well into the future.

Improved Connection Speeds
Initially NG-PON2 will provide a minimum of 40 Gbps downstream capacity, produced by four 10 Gbps signals on different wavelengths in the O-band multiplexed together in the central office with a 10 Gbps total upstream capacity. This capability can be doubled to provide 80 Gbps downstream and 20 Gbps upstream in the “extended” NG-PON2.

Symmetrical Upstream and Downstream Capacity
Both the basic and extended implementations are designed to appeal to domestic consumers where gigabit downstream speeds may be needed but more modest upstream needs prevail. For business users with data mirroring and similar requirements, a symmetric implementation will be provided giving 40/40 and 80/80 Gbps capacity respectively.

With the introduction of NG-PON2, there is now an obvious difference between optical access network and copper access network capabilities. Investment in NG-PON2 provides a far cheaper network to operate, significantly faster downstream and upstream speeds and a future-proof upgrade path all of which copper access networks do not provide, thus making them obsolete technologies. Telephone companies around the world have been carrying out trials of NG-PON2 and key telecommunication vendors have rushed NG-PON2 products to market.

Source: http://www.fs.com/blog/the-latest-generation-of-pon-ng-pon2.html

From O to L: the Evolution of Optical Wavelength Bands

In optical fiber communications system, several transmission bands have been defined and standardized, from the original O-band to the U/XL-band. The E- and U/XL-bands have typically been avoided because they have high transmission loss regions. The E-band represents the water peak region, while the U/XL-band resides at the very end of the transmission window for silica glass.

Optical Wavelength Bands

Intercity and metro ring fiber already carry signals on multiple wavelengths to increase bandwidth. Fibers entering the home will soon do the same. Now there are several types of optical telecom systems have been developed, some based on time division multiplexing (TDM) and others on wavelength division multiplexing (WDM), either dense wavelength division multiplexing (DWDM) or coarse wavelength division multiplexing (CWDM). This article may represent the evolution of optical wavelength bands mainly by describing these three high-performance systems.

Dense Wavelength Division Multiplexing
DWDM systems were developed to deal with the rising bandwidth needs of backbone optical networks. The narrow spacing (usually 0.2 nm) between wavelength bands increases the number of wavelengths and enables data rates of several Terabits per second (Tbps) in a single fiber.

These systems were first developed for laser-light wavelengths in the C-band, and later in the L-band, leveraging the wavelengths with the lowest attenuation rates in glass fiber as well as the possibility of optical amplification. Erbium-doped fiber amplifiers (EDFAs, which work at these wavelengths) are a key enabling technology for these systems. Because WDM systems use many wavelengths at the same time, which may lead to much attenuation. Therefore optical amplification technology is introduced. Raman amplification and erbium-doped fiber amplifiers are two common types used in WDM system.

DWDM

In order to meet the demand for “unlimited bandwidth,” it was believed that DWDM would have to be extended to more bands. In the future, however, the L-band will also prove to be useful. Because EDFAs are less efficient in the L-band, the use of Raman amplification technology will be re-addressed, with related pumping wavelengths close to 1485 nm.

Coarse Wave Division Multiplexing
CWDM is the low-cost version of WDM. Generally these systems are not amplified and therefore have limited range. They typically use less expensive light sources that are not temperaturestabilized. Larger gaps between wavelengths are necessary, usually 20 nm. Of course, this reduces the number of wavelengths that can be used and thus also reduces the total available bandwidth.

CWDM

Current systems use the S-, C- and L-bands because these bands inhabit the natural region for low optical losses in glass fiber. Although extension into the O and E-band (1310 nm to 1450 nm) is possible, system reach (the distance the light can travel in fiber and still provide good signal without amplification) will suffer as a result of losses incurred by use of the 1310 nm region in modern fibers.

Time Division Multiplexing
TDM systems use either one wavelength band or two (with one wavelength band allocated to each direction). TDM solutions are currently in the spotlight with the deployment of fiber-to-the-home (FTTH) technologies. Both EPON and GPON are TDM systems. The standard bandwidth allocation for GPON requires between 1260 and 1360 nm upstream, 1440 to 1500 nm downstream, and 1550 to 1560 nm for cable-TV video.

To meet the rise in bandwidth demand, these systems will require upgrading. Some predict that TDM and CWDM (or even DWDM) will have to coexist in the same installed network fibers. To achieve this, work is underway within the standardization bodies to define filters that block non-GPON wavelengths to currently installed customers. This will require the CWDM portion to use wavelength bands far away from those reserved for GPON. Consequently, they will have to use the L-band or the C- and L-bands and provided video is not used.

tdm

Conclusion
In each case, sufficient performance has been demonstrated to ensure high performance for today’s and tomorrow’s systems. From this article, we know that the original O-band hasn’t satisfied the rapid development of high bandwidth anymore. And the evolution of optical wavelength bands just means more and more bands will be called for. In the future, with the growth of FTTH applications, there is no doubt that C- and L-bands will play more and more important roles in optical transmission system. Fiberstore offer all kinds of products for WDM optical network, such as CWDM/DWDM MUX DEMUX and EDFA. For more information, please visit www.fs.com.