How to Expand Bandwidth in PON Network with CWDM Technology?

PON (passive optical network) is one of a common optical fiber network architectures. It is characterized by the “splitting” of the optical fiber one or more times, resulting in the sharing of optical fiber among multiple users. However, as networks grow in terms of subscriber counts, the scope and number of services offered, expanding the network bandwidth is inevitable. Coarse Wave Division Multiplexing (CWDM), known for its low cost and scalability to increase fiber capacity as needed, is a preferred method for PON network expansion. This article will focus on using CWDM technology to overcome bandwidth limitations in PON access networks.

CWDM Mux/Demux and OADM (Optical Add-Drop Multiplexer) in Access PON

Fibers in a PON are typically shared with several users. Hence the bandwidth of the fiber originating at the CO (center office) is shared among a group of users. The splitting of the network is accomplished by optical splitters. These splitters can split the fiber 2-32 times, which may introduce high losses in the network. Besides, as different places in a same network need different wavelengths, CWDM Mux is often deployed to multiplex these signals on a single fiber.

In PON (Passive Optical Network) network, whether in ring structures or point-to-point arrangements, different optical nodes need specific wavelengths. Therefore, at each node, a CWDM OADM is used to drop or add certain channels from the fiber as required,. Then the signals will be transmitted to the user through optical fibers. The following picture shows a simple PON network.

How to Expand Bandwidth of PON Network Using CWDM Technology?

Upgrading Access PONs Using Passive CWDM Mux/Demux

In PON networks, OLT has two float directions: upstream (getting an distributing different type of data and voice traffic from users) and downstream (getting data, voice and video traffic from metro network or from a long-haul network and send it to all ONT modules on the ODN).

The following figure represents a situation where existing subscribers intend to upgrade to higher value added bandwidth services. In order to satisfy customers’ needs for IPTV, VoIP, video on demand etc., the 622 Mb/s downstream capacity between the CO and the OLT, providing roughly 20 Mb/s to each subscriber, must increase.

Considering there may be new subscribers and services added, the targeted bandwidth requires at least a downstream CO/OLT link bandwidth of 2.5Gb/s. Therefore, four CWDM wavelengths are introduced to multiply the channels passing between the CO and OLT. This introduction of passive CWDM Mux/Demux can relieve the fiber exhaust effectively. The below figure shows the upgrading process.

Advantages of This Upgrade

Compared with laying a new fiber cable, the upgrade with passive CWDM is easily accomplished within hours after some modest investment in network planning. And the sum of material, labor, equipment and training expense is far less, which explain why many enterprises, private business users of LAN and data storage networks use passive CWDM too.

Expanding EPON Bandwidth Using CWDM Mux/Demux

EPON stands for Ethernet passive optical network. It is an enabling technology that benefits consumers. Here is an EPON network, which was conceived to serve up to 64 subscribers. All users share a single bidirectional optical feed line. With the need for IPTV, HDTV and other higher bandwidth services growing, the downstream capacity 16Mb/s should be improved.

The picture below shows the same EPON deployment upgraded to 4Gb/s bandwidth capacity.

This upgrade uses 4 channels passive CWDM Mux/Demux to extend the whole network capacity, allowing the downstream capacity increase four times without affecting the upstream traffic.

Advantage of This Expansion

Using CWDM Mux/Demux effectively increases the network bandwidth capacity and reduces the cost. At the same time, it requires minimal modification of the existing infrastructure, which also saves labors.

Summary

CWDM technology offers significant benefits of low investment, minimal operating cost and very simple and straightforward upgrade planning and implementation. In addition, passive CWDM also provides scalability and network flexibility for network growth and bandwidth demands in the future. FS.COM supplies different channels of CWDM components. Welcome to contact us via sales@fs.com.

Related article: Examples of CWDM Network Deployment Solution

Sources:http://www.fiber-optic-components.com/how-to-expand-bandwidth-in-pon-network-with-cwdm-technology.html

Examples of CWDM Network Deployment Solution

Based on the same concept of using multiple wavelengths of light on a single fiber, CWDM and DWDM are two important technologies in fiber optical communications. As we all know, although the transmission distance of CWDM network is shorter than that of DWDM, it costs less and has the scalability to grow fiber capacity as needed. This article intends to give a simple introduction of components in CWDM networks and to explore some examples of CWDM network deployment cases.

Common Components Used in CWDM Networks

CWDM Mux/Demux

CWDM Mux/Demux, which is based on the film filter technology, is the basic component in CWDM networks. It can combine up to 4, 8 or 16 different wavelength signals from different fiber extenders to a single optical fiber, or it can separate the same wavelengths coming from a single CWDM source. That’s why CWDM can extend existing fiber capacity.

CWDM OADM (Optical Add-Drop Multiplexer)

A CWDM OADM is a device that can add (multiplex) and drop (demultiplex) channels on both directions in a CWDM network. It can add new access points anywhere in CWDM systems without impacting the remaining channels traversing the network. With this ability of OADM, the access points can be added to liner, bus, and ring networks, where the dual direction ring design provides redundant protected architecture.

CWDM Optical Transceiver

Optical transceiver is a necessary element in optical networks. And CWDM optical transceiver is a type of module supporting CWDM network application with CWDM wavelengths. When connected with CWDM Mux/Demux, CWDM transceiver can increase network capacity by allowing different data channels to use separate optical wavelengths (1270nm to 1610nm) on the same fiber. And the common CWDM transceiver type is SFP, SFP+, XFP, XENPAK, X2, etc.

CWDM Network Deployment Solution

Example One

Description: there are five buildings (Sheriff, Courthouse, Admin, Police & Fire, & Public Works) connected via multimode fiber cables (MMF) or single mode fiber cables (SMF). These buildings are linked via multimode SFPs in an existing D-link switches to create one network for internal use of the city offices. Below is a simple graph to show the situation.

Requirements: the goal is to install a single mode fiber network in town to connect numerous buildings. Some of these buildings have access to the city LAN. The Public Works building need to connect with Youth & Recreation Center, Library, Immanuel Lutheran School and the Senior Center. And all these buildings should have unfiltered Internet. Besides, the Waster Water Treatment Plant should be connected passing through the Senior Center. All these services are achieved using CWDM technology.

Solution: according to the requirements, this is a CWDM networks with several buildings to connect with. Here is the solution diagram.

In the diagram above, we can see there is an 8CH CWDM Mux/Demux connected with the switches. According to the requirements, Youth & Recreation Center, Library, Immanuel Lutheran School and Senior Citizen Center should be connected with the Public Works and need unfiltered services. Therefore, a 4CH CWDM OADM is placed after the CWDM Mux/Demux. Then the four wavelengths will be drop and into the four buildings. In addition, another CWDM OADM is deployed in Senior center to connect the Waster Water Treatment Plant, to meet the requirement. And each site also needs to use CWDM optical transceivers.

Example Two

Description: on site A, there are three Ethernet switches and a T3 router. And their working wavelengths 1470nm, 1490nm, 1510nm, 1530nm and 1610nm. Other three sites B, C, and D also have three Ethernet switches. And a T3 router is in site E. As the following figure shows.

Requirements: Considering the cost, all the wavelengths should be transmitted on a single fiber using CWDM technology.

Solution: according to the requirements, here is a simple diagram showing the solution.

In order to save cost, a 4CH CWDM Mux/Demux is used to multiplex four wavelengths (from three switches and one router) into one single fiber. At the first site B, a 1CH CWDM OADM is installed to remove one wavelength which is associated with network B. And other three sites are the same—dropping one wavelength associated with corresponding switch or router.

Summary

This article mainly introduces two CWDM network deployment examples. All the components like the CWDM Mux/Demux, CWDM OADM and CWDM transceiver are available in FS.COM. If you are interested in them, please contact us via sales@fs.com.

Related article:Differences between CWDM and DWDM

Sources:http://www.fiber-optic-components.com/examples-cwdm-network-deployment-solution.html

How to Realize Single Fiber Connection in WDM System?

As we all know, fiber optical networking has two transmission ways: dual fiber transmission and single fiber transmission. The difference between them is that the former one requires two fibers—one is for transmitting and the other is for receiving, while the latter only uses one fiber for both transmitting and receiving. Single fiber transmission emergence reduces network deployment cost, especially in WDM systems. This blog intends to introduce how to achieve single fiber connections in CWDM and DWDM networks.

Understanding Single Fiber Transmission

Single fiber transmission, also called bidirectional (BiDi) transmission, sends data in both directions with one strand fiber. For enterprise networks or telecom networks providers who are with limited budgets and fiber capacity, the single fiber transmission is no doubt an ideal choice.

In addition, single fiber transmission is popular in many places.

• Point to Point, Ring or linear Add and Drop, where installing new fiber is difficult or expensive
• Enable segmentation of the enterprise traffic over 2 different fibers rather than using the same fiber for both segments
• Increase reliability to an existing dual fiber solution by using one fiber for working and one for protecting

Single Fiber Solution in CWDM Systems

CWDM technology enables multiple channels (wavelengths) to be transmitted over the same fiber cabling and is able to provide a capacity boost in metro and access networks. Each channel carries data independently from each other, which allows network providers to transport different data rates and protocols (T1, T3, Ethernet, Serial, etc) for different customers or applications. Then how to achieve single fiber transmission in CWDM networks?

Here is an example of single fiber solution in CWDM system.

The above picture shows how different CWDM wavelengths are transmitted in a single fiber CWDM link. In this link, two 8CH CWDM Mux/Demuxs are required to transmit sixteen different wavelengths. At site A, there is a single fiber 8CH CWDM Mux/Demux using eight wavelengths for transmitting and the other different eight wavelengths for receiving. At site B, another 8CH single fiber CWDM Mux/Demux is deployed. But the wavelengths for TX and RX are reversed. And one single fiber connects the two CWDM Mux/Demux.

Notes: the use of transceivers connected with the CWDM Mux/Demux should be based on the wavelength of the TX side.

Single Fiber Solution in DWDM Systems

DWDM is an optical multiplexing technology to increase bandwidth over existing fiber optic networks, especially in long haul transmissions. And it can support more channels and higher traffic services such as 40G, 100G of LAN/WAN. Since the cost of DWDM components is high, the single fiber transmission is necessary.

DWDM single fiber transmission can be achieved with the use of single fiber DWDM Mux/Demux. As the following picture shows.

The picture shows a single fiber 8CH DWDM Mux/Demux with expansion port used for single fiber transmission. Similar to the single fiber CWDM Mux/Demux above, this DWDM Mux/Demux also uses eight wavelengths for transmitting and another eight wavelengths for receiving. In general, the DWDM Mux/Demux should be used in pairs in single fiber bi-directional transmission, and the Mux/Demux port for specific channel must be reversed. Besides, more channels can be added into the links with the expansion port.

This 8CH DWDM Mux/Demux single fiber solution allows extremely high utilizing of a single fiber strand to pass up to 16 wavelengths, optimizing the use of fiber optic cables. And in long distance transmission, optical amplifier also can be utilized.

FS.COM Single Fiber Solution

FS.COM supplies various single fiber CWDM & DWDM Mux/Demux and optical transceivers. Here is part of our Mux/Demux products.

Single Fiber CWDM & DWDM Mux/Demux	Product ID	Operating Channel
	43779	Tx/Rx:1310/1290, 1350/1330, 1390/1370, 1430/1410, 1490/1470, 1530/1510, 1570/1550, 1610/1590
	50117	Tx/Rx:C21/C22,C23/C24,C25/C26,C27/C28, C29/C30,C31/C32,C33/C34,C35/C36

sources:http://www.fiber-optic-components.com/how-to-realize-single-fiber-connection-in-wdm-system.html