Category Archives: FTTX network

PON Transceivers for FTTH Applications

Nowadays, the requirements for higher Internet access speed keep growing in different applications such as video conference, 3D and cable TV, which result in popularity of FTTH (fiber-to-the-home) deployments. Passive Optical Networks (PON), as the leading technology used in FTTH applications, are also widely used. PON transceivers are one of the important components in PON systems. This post intends to describe some basic knowledge of PON transceivers.

Basics of PON Transceiver

PON transceiver is a type of optical transceivers which often uses different wavelengths to transmit and receive signals between an OLT (Optical Line Terminal) and ONTs (Optical Network Terminals, also called ONU). According to different standards, PON transceivers can be divided into different types. There are diplexer and the triplexer transceivers on the basis of wavelengths. For the diplexer transceivers, the 1310nm wavelength is for the upstream and 1490nm for the downstream wavelength. While for the triplexer transceiver, the 1550nm wavelength is used in the downstream direction. Of course, it is also possible that 1490nm wavelength is allocated in the downstream direction by using video over IP technologies.

ftth

According to the plugged-in device, there are OLT and ONU transceivers. Generally, OLT transceiver is more complicated than ONU transceiver. Because one OLT transceiver may need to communicate with up to 64 ONU transceivers.

Two Common Types of PON Transceiver

It’s know to all that there are two usual network architectures in PON systems: GPON (Gigabit Passive Optical Network) and EPON (Ethernet Passive Optical Network). Both of them offer users high-speed services over an all-optical access network. As we have mentioned above, PON transceiver can be classified into OLT and ONU transceivers. Here mainly introduce two common OLT transceivers used in GPON or EPON network.

GPON OLT Transceiver

The GPON OLT transceiver is designed for GPON transmission. In order to illustrate this transceiver clear, let’s take the GPON OLT SFP module for an example (shown as following picture). The transceiver uses 1490nm continuous-mode transmitter and 1310nm burst-mode receiver. The transmitter section uses a high efficiency 1490nm DFB laser and an integrated laser driver which is designed to be eye safety under any single fault. The receiver section uses an integrated APD detector and bursts mode pre-amplifier mounted together. To provide fast settling time with immunity to long streams of Consecutive Identical Digits (CID), the receiver requires a reset signal provided by the media access controller (MAC). The GPON OLT SFP transceiver is a high performance and cost-effective module for serial optical data communication applications to 2.5Gpbs.

gpon-olt-sfp-transceiver

EPON OLT Transceiver

EPON OLT transceiver is designed for PON applications. It has SFP, XFP and SFP+ packages. Here we also introduce this transceiver by taking EPON OLT SFP transceiver as an example. Generally, EPON OLT SFP transceivers support 1.25Gbps downstream and 1.25Gbps upstream in EPON applications. Like the GPON OLT SFP transceiver, they also have 1490nm continuous-mode transmitter and 1310nm burst-mode receiver. And their transmission reach is 20 km. The transmitter section uses a 1490nm DFB with automatic power control (APC) function and temperature compensation circuitry, which can ensure stable extinction ratio overall temperature range. And the receiver section has a hermetically pre-amplifier and a limiting amplifier with LVPECL compatible differential outputs.

epon-olt-sfp-transceiver

Challenges of PON Transceivers

Although PON transceivers provide a satisfying performance in FTTH applications, there still exists some challenges in the following aspects:

  • Burst-mode optical transmission technologies for the upstream link.
  • High-output-optical-power and high-sensitivity OLT at the CO (central office) are needed for the losses introduced by the optical splitters and fibers connecting subscribers’ premises.
  • The Optical Line Terminal (OLT) RX needs to be able to receive packets with large differences in optical power and phase alignment.
  • Quick rise/fall time to minimize guard time during transmission.
Summary

PON transceiver is a high performance module for single fiber communications by using continuous-mode transmitter and burst-mode receiver with different data rate and wavelengths. In this post, the basis and common types of PON transceivers are illustrated. Hope it could help you. For more information, please visit FS.COM.

Comparison Between Active and Passive Optical Network

As time goes by, in order to meet the need for higher bandwidth, faster speed and better utilization of fiber optics, FTTH access networks designs have developed rapidly. And there are two basic paths of FTTH networks: active optical network (AON) and passive optical network (PON). However, how much do you know about the them? Do you know what’s the differences between the two systems? Now, this article will give a detailed comparison between them.

Active Optical Network (AON)

Active optical network, also called point-to-point network, usually uses electrically powered switching equipment such as a router or switch aggregator, to manage signal distribution and direct signals to specific customers. This switch opens and closes in various ways to direct incoming and outgoing signals to the proper place. Customers can have a dedicate fiber running to his or her home, but it needs many fibers.

aon

Passive Optical Network (PON)

Different from AON, PON doesn’t contain electrically powered switching equipment, instead it uses fiber optic splitters to guide traffic signals contained in specific wavelengths. The optical splitters can separate and collect optical signals when they run through the network. And powered equipment is needed only at the signal source and the receiving ends of the signals. Usually, the PON network can distribute signals into 16, 32 and 64 customers.

pon

AON vs. PON

As data travel across the fiber connection, it needs a way to be directed so that the correct information can arrive at its intended destination. And AON and PON offer a way to separate data and set it upon its intended route to arrive at the proper place. Therefore, these two networks are widely applied in FTTH systems. However, each system has their own merits and shortcomings. Here is a simple comparison between them.

Signal Distribution

In AON networks, subscribers have a dedicated fiber optic strand. In another word, each subscriber gets the same bandwidth that doesn’t be shared. While the users share the fiber optic strands for a portion of the network. These different network structures also lead to different results. For example, if something goes wrong in a PON network, it will be difficult to find the source of the problem. But this problem does not exist in AON.

Equipment

As we have noted above, AON directs optical signals mainly by powered equipment while PON has no powered equipment in guiding signals except for two ends of the system.

Cost

When running an existing network, it’s known to us that the main source of cost is the maintenance and powering equipment. However, PON uses passive components that only need less maintenance and do not need power, which contributes to that PON building is cheaper than that of AON.

Coverage Distance

AON networks can cover a range to about 100 km, a PON is typically limited to fiber cable runs of up to 20 km. That is to say, subscribers must be geographically closer to the central source of the data.

Of course, apart from what have been listed above, there are other differences between these two networks. For instance, AON network is currently the industry standard. It’s simple to add new devices to the network. And there are numbers of similar products on the market, which are convenient for users to select. Besides, AON is a powered network, which decides it’s less reliable than PON. However, since the bandwidth in PON is not dedicated to individual users, people who use a passive optical network may find that their system slows down during peak usage times.

Conclusion

In summary, AON and PON have their own advantages and disadvantages, but both of them provide practical solutions for FTTH network connection. There is no right or wrong answers when it comes to choose which one of them. FS.COM provides several kinds of PON equipment such as PON splitters and OLT/ONT Units. If you want to find out more, please visit Fiberstore website.

PON – a Better Network Solution

When choosing a best fiber architecture for the network, many planners may choose PON today. PON, short for passive optical networks, is a telecommunication network that uses point-to-multipoint fiber to the end-points in which unpowered optical splitters are used to enable a single optical fiber to serve multiple end-points. “Passive” means optical transmission has no power requirements or active electronic parts when the signal is going through the network. It is the core underpinning of fiber optical service.

Introduction of PON

Passive optical network is widely applied in fiber-to-the-curb (FTTC), fiber-to-the-building (FTTB), or fiber-to-the-home (FTTH), which is decided by the places it terminates. Commonly, it is made up of an optical line terminal (OLT) in the central office and a number of optical network units (ONU) near end users. From the picture below, we can get a brief understanding of the working process of it.

First and foremost, the data or the signals in the central office will be transmitted over a single optical fiber without interfered by each other, because encryption can prevent eavesdropping. And then the passive splitter will separate the signals into several optical network units which can be up to 64 units.

PON

Classifications of PON

The first PON systems which is based on Asynchronous Transfer Mode (ATM, or “cell switching”) were called “APON”. It has been achieved significant commercial deployment and still be applied in someplace today. The “Broadband PON” comes after APON. Typically, these two systems both have downstream capacity of 155 Mbps or 622 Mbps and upstream capacity of 155 Mbps.

And as the technology advanced, there is a growing requirements of higher capacity. As a result, APON and BPON is gradually replaced by GPON. GPON, short for Gigabit-capable passive optical network, is the successor of APON and BPON, and also based on ATM transport. Typically, its capacity of upstream ranges from 622 Mbps to 1.25 Gbps, while the downstream capacity ranges from 622 Mbps to 2.5 Gbps. In today’s fiber-to-the-home (FTTH) networks, GPON is most widely deployed, which is generally considered suitable for consumer broadband services for the next 5 to 10 years.

EPON (Ethernet passive optical network) is the rival of GPON, using Ethernet packets instead of ATM cells. It is cheaper to deploy than GPON, but it has not garnered the level of acceptance of GPON.

And WDM PON (wavelength-division multiplexing passive optical network) is a network that combines WDM technology with PON system. It can use wavelength-division multiplexing to split each signal into different branches.

Advantages of PON

Compared with the traditional enterprise network, PON network is obvious superior to it. And there are several advantages of PON.

Energy savings – PON system does not need rack mount switches and other active devices in remote locations so that it can reduce a number of heat generating devices that must be cooled and powered, thereby generating energy savings. Also, there are reduced HVAC (Heating Ventilation Air Conditioning) requirements, since there is no radiant heat with fiber cabling.

Lower cost – Due to lower power consumption, reduction in floor space, and yearly reduced maintenance costs, the enterprise will realize significant operational expense savings over the life of the system of 45-70% over that of a traditional copper based system, as well.

Optimized bandwidth utilization – with dynamic allocation of bandwidth, the system can provide optimized network connectivity to those application and users requiring the greatest bandwidth, while facilitating future proofing.

Now, the Ethernet market becomes more and more popular, so PON is gradually getting into a bright future. With these significant advantages, PON can meet the changing demands of the enterprise network more quickly and easily. And at present, the most popular network systems are GPON and EPON. Fiberstore offers various PON products, including optical line terminals and optical network units, and if you want to deploy your network most efficiently, Fiberstore is your best choice.

Related article: http://www.chinacablesbuy.com/a-guide-for-pon.html