# How to Calculate DWDM System Loss in Long Haul Transmission

Nowadays, high capacity network is needed to deal with large amount of data transfer. The application of DWDM (dense wavelength division multiplexing) system is a commonly used technique to enhance network capacity. Due to its complexity caused by various components like EDFA and dispersion compensating module (DCM), it may be difficult to calculate the loss over the whole links, especially in long haul transmissions. Then, how to calculate the budget loss of a DWDM system in long haul transmission? This post will illustrate the method to solve this problem.

Causes of Loss in Long Haul DWDM System

Loss budget is always one of the crucial problems that need to be considered before deploying a network. Any components in optical links will introduce loss. For example, when add a DWDM mux to a DWDM network, it will cause insertion loss which is the total optical power loss (often measured by dB) caused by the insertion of an optical component. In long haul DWDM system, there are several causes of link loss.

DWDM Muxs

DWDM Muxs are the components that combine several different wavelengths so that they can be transferred on one fiber. And Mux is a passive device that cannot strengthen the light signals. Therefore, there is a big insertion loss of DWDM Mux. The lower the insertion loss is, the less network deployment cost is needed. Although Mux vendors are always endeavoring to reduce the insertion loss, there are still big differences between DWDM Muxs of many vendors. Here is a histogram to provide a direct-viewing comparison. From the graph, we can see the maximum insertion loss of FS.COM 40CH DWDM Mux is only 4.5dB.

DCM (Dispersion Compensation Module)

Dispersion compensation module is to fix the optical signals that have been deformed by chromatic dispersion. Therefore it is important to use at the receiver end to recover the signals by reshaping the optical pulse. This component also brings a good amount of insertion loss.

OADM is another device that introduces insertion loss for DWDM networks. Since it allows individual or multiple wavelength channels to be added or dropped from an incoming link, as the signal pass from the common port to add/drop port or from the add/drop port to the common port, insertion loss occurs.

Except for the components that cause loss for the whole links, fiber optic cables also introduce loss which increases as the distance gets longer. Besides, in order to achieve balance signal power for receivers, designers often use EDFA to boost or add gain to optical signals on a fiber optic cable.

How to Calculate the Loss Budget of DWDM System?

In order to illustrate the calculation process clearly, here takes a case from FS.COM as an example. This deployment solution is designed for a client in UK. The following picture just shows part of the solution design.

The distance of site A and site B is 132.4km. From the figure, we can see optical components used includes 40CH DWDM Mux/Demux, booster EDFA, Pre-amplifier, 2CH OADM, etc. And there are also optical attenuators which are not shown in the figure. Here is a chart indicating the loss or gain value of them which can be found on FS.COM website.

 Components Insertion loss/Gain 40CH DWDM+MON 4.5dB Booster EDFA 23dB Pre-amp EDFA 26dB Attenuator 0-30dB

Now let’s start to calculate the budget loss in this link. Considering the whole solution is so complicated that this calculation is just to give an example of calculating the budget loss between site A and site B. And the calculation starts from site A to site B unidirectional, as the arrow line shows.

• The loss between the 40CH DWDM Mux and the router is -8.5dB, caused by the use of an optical attenuator.
• Then the signals pass through the DWDM Mux, the output power is:-8.5dB-4.5dB =-13dB.
• Since the booster EDFA gain is +23dB, the signal output power of this EDFA is: -13dB+23dB= +10dB.
• Calculation of the fiber optic cable, the total loss is: -0.22dB/km x132.4km = -29.13dB. The input power of the pre-amp EDFA is: +10dB-29.13dB = -19.13dB.
• The pre-amp EDFA gain is +26dB, then the output power of this EDFA is +6.87dB.
• There is an attenuator placed after the pre-amp EDFA, the output power after the attenuator is: +6.87dB-18dB = -11.13dB.
• The output power of the booster EDFA is: +23dB-11.13dB=+10.67dB. That’s the output power of site B.
Summary

For DWDM network system, how to control the power loss is important, which requires network designers calculate the budget loss before deploying the systems. This post gives an example from our client to calculate the loss in a DWDM network. FS.COM offers both necessary optical components and solutions for your networks. If you are interested, please contact us via sales@fs.com.

# Options Upgrading to 100G Connection

With growing data traffic volume in recent years, the existing 10Gb/s optical networks are becoming saturated, which drive the great need for 40G and 100G networks. In turn, 100G network also can bring benefits for network operators. For example, 100G network can reduce the cost per bit, improve the utilization of existing fiber and reduce the network delay. This post intends to explore the options to get 100G connection.

100G Connectivity Challenges

As we all know, existing 10G network use two fibers in either a SC duplex or a LC duplex connector to realize data transmission. But different from this transmit type, data in 100G network often get multiplexed and transferred over the 4 or 10 parallel wavelengths on a single fiber, which means the lanes of the two kinds of networks are a little different. This is one problem that should be considered when deploy 100G connections.

Except for that, the cost is another problem needed to be resolved. No matter the 40G or 100G, both of them require more fibers and optical connectors, resulting in increasing cost. For example, 40G Ethernet and 100G Ethernet over multimode fiber uses parallel optics at 10 Gb/s per lane. One lane uses one fiber for each direction of transmission. So 40G Ethernet requires eight fibers. And 100G Ethernet requires 20 fibers.

Option One: Upgrading to 100G Connections with DWDM Mux

With the boom application of cloud services, telemedicine, video on demand, etc, data rate migration encompassing the entire optical network. Therefore, some core networks have deployed DWDM to release this bandwidth explosion. With large capacity transmission ability, DWDM technology offers a cost-effective method to meet the bandwidth requirements.

In many cases, to avoid the high cost and save cost, some operators often use one DWDM Mux to add one or more 100G services into the same fiber. The picture is showing one of that cases. In this case, 10G and 100G services are multiplexed by two separated 100GHz DWDM MUX. Owing to the 100G services are easy to be affected by dispersion, so the optical amplifier and DCM (Dispersion Compensation Module) are added in the links to boost the signal power. Then the 10G and 100G services are bundled together by using the interleaver which is an optical router often used in DWDM system. And finally the 100G connection is achieved.

Option Two: Upgrading to 100G Connections with MTP Assemblies

Nowadays there are various products on the market to support 100G connections. The most often used is 100G CFP, 100G QSFP28 and MTP optical cables. For many network operators, the option one that uses 100GHz DWDM Mux, optical amplifier, DCM and 100G optical transceivers maybe a little expensive. However, except for using DWDM Mux to achieve 100G connections, there is another choice. It is to achieve 100G connections with MTP assemblies.

In this connection, the 100G connection can be realized by using a MTP cord with a 24-fiber MTP connector on one end and two 12-fiber MTP connectors on the other end.

Notes: this simple chart just illustrates a short distance 100G connection.

Besides, since 10G connections usually use common fiber optic cables with LC or SC connectors, and the 40G connections use 12-fiber MTP cables, while 100G connections utilize 24-fiber MTP connections. Therefore, migrating from 10G/40G to 100G can be realized. Look at the basic 10G and 40G deployment scenario.

From the picture we can see, the similarities of these connections are that they are using MTP cables. Just change the cable types and then migrating from 10G to 40G and 100G are possible.

Summary

100G connection is the trend in the future data centers. This post introduces two options to achieve 100G connections with existing optical components. According to different requirements, you can choose a suitable solution. FS.COM supplies various optical components to meet diverse applications in data centers and enterprise networks. If you want to know more details about 100G networks, please visit our website www.fs.com.

With an explosive growth in the amount of information transmission, the optical telecommunication networks develop rapidly. The progress of single wavelength point-to-point transmission lines to wavelength division multiplexed optical networks has introduced a demand for wavelength selective optical add-drop multiplexer (OADM) to separate or route different wavelength channels. This paper will have an overview of the OADM.

The introduction of optical add drop multiplexers into optical networks allows traffic to be inserted, removed and, most importantly, bypassed. Moreover, OADM can support functions such as protection, drop/continue, loop-back and wavelength reuse of the optical channels. Drop and continue refer that the channel is removed at the node but allowed to pass through to the next OADM. Wavelength reuse means the dropped channel does not pass through to the next OADM, instead, a new channel of the same wavelength can be added. Below figure explains OADMs work in a CWDM system.

OADM can be used in the dynamic as well as static mode. The add and drop wavelengths are fixed in the passive OADM, while in dynamic mode, the OADM can be set to any wavelength after installation. Passive OADM is mainly used in networks with WDM systems (CWDM and DWDM) or hubbed structures, where the OADM is connected to a central hub, e.g. in the metropolitan network. In order to utilize resources in a more efficient way, the OADM with dynamic wavelength assignment are preferred when traffic variations are comparable to network capacity. It can select any wavelength by provisioning on demand without changing its physical configuration.

OADM has many advantages. The most striking one is that its multiplexing happens to coincide with the minimum loss area of single mode fiber. This reduces the transmission loss of the light signal which can be transmitted relatively far distance. Additionally, it is transparent to digital signal format and data rate. Its gain saturation recovery time is long, and has a very small crosstalk between the respective channels. What’s more, multiple channels of information carried over the same fiber with each using an individual wavelength. Narrow channel spacing or wavelength selection give rise to denser channels in the same wavelength range. Last but not the least, repeater or amplification sites are reduced, which results in large savings of funding.

Applications

OADM supports standard network topologies such as point-to-point and ring. It can be used at different points along the optical link to insert/remove or route selected channels increasing the network flexibility. This feature is particularly important in metropolitan WDM lightwave services where offices or sites can be connected by different add-drop channels, for instance in an interoffice ring. In WDM systems, OADM is installed in a multi-wavelength fiber span, and allows a specific wavelength on the fiber to be demultiplexed (dropped) and remultiplexed (added) while enabling all other wavelengths to pass. Then it can provide flexibility and scalability to optical networks as it allows users to optimize the use of existing fiber by adding or dropping channels on a per-site basis, thereby maximizing fiber bandwidth.

In conclusion, optical add-drop multiplexer can contribute to improve and optimize the network performance. Fiberstore, a professional supplier in the optical industry, has lots of CWDM OADM and DWDM OADM. Besides these, the WDM fiber optic multiplexer, CWDM Mux/Demux and DWDM Mux are also available. Welcome to visit www.fs.com for more information.

# Optical Module Will Be Shine In The Field of Data Communications

With the current amount of data has been too large to be collected, stored, managed and analyzed using traditional tools, the era of big data is coming. To meet the challenges of big data, cloud computing network technology application virtualization technology is the inevitable trend of development, cloud computing and data center network cabling system to build, then adapted to the era of big data network infrastructure requirements. Faced with massive data storage and data processing, and data centers in order to improve the efficiency of resource use computing power and data analysis, the extensive use of virtualization, cloud computing power and data analysis, the extensive use of virtualization, cloud computing technologies, including server virtualization, network virtualization technology and storage virtualization technology etc.

The network is the foundation of all the data flow, closely related to the development of large data generation and network technology. Accordingly, the large data transfer rate is closely related to the network, and therefore a higher demands of the optical module. In general, the core layer using 40G/100G, access layer with the method of 10G basic has become the direction of the network upgrade.

Take a look at the sales volume of 10G optical transceivers. Although 100G and 40G sals growth is more attention, but 10G optical transceiver sales still set a new record in 2013. 10G optical
transceiver demand is very strong at short distances, which pushed up overall in 2013 the 10G module shipments will exceed 10 million, up 40% from last year. This will also be a short distance 10G module shipments 1G short distance beyond the first year, the data show that the 10G connector will have a larger market share.

There are many factors encourage the growth of 100G and 40G, the Ethernet transceiver market growth prompted 40G and 100G growth in shipments. However, due to the rapid decline in FTTx market, in 2013 the optical transceiver market as a whole will be flat. Many manufacturers have said the 2013 report of EPON and GPON ONU a significant reduction in volume, although sales remained stable OLT. Global optical transceiver market, including 10G, 40G and 100G transceiver, 2012 increaded 10% to \$1.63 billion.

Optical module growth space is large especially the data communication field

2013 data communications optical components and modules for sales growth of 20%, and in 2012 was 16%. But the telecom optical components and modules market is still sleeping, in 2012 and 2013 grew by only 3%. For the upcoming 2014, the telecommunications market is likely to be better.

40G optical transceiver sales in 2013 increased by more than three times, mainly like Google has a large data center for its large demand. 100G DWDM transponder current price is 30 times 10G DWDM transceiver. However, 100G wide area, and some are laying metro network applications, because it can create additional value for network operators. WAN, 100G maximize the transmission capacity of optical fiber has been deployed, and in the next 10 years, it will not become obsolete. A core router 100G port can be connected with 10 different 10G ports. This is 100G optical device to another value of core network.

And we have learned, Facebook, Google, Microsoft and other multinational companies, have their own cloud data centers, coupled with governments agencies also commissioned by the network operator to build a public cloud centers, etc., the future applications in the data center business opportunities in the field of the cloud is still in the growth, therefore, in the next few years optical transceiver module, AOC and other products are growing space.

Cisco has also stepped up its efforts in building the data center. Cisco continued to increase in recent years of data construction, revenue accounting for its data center products increased year by year the proportion of revenue, below shows the Cisco 2011 to the first quarter of 2013 accounted for a quarter of data revenue from product revenue proportion charts. In addition, in June this year Composite cisco’s \$180 million acquisition of the data processing companies, also shows that the emphasis on data center.

Data center optical module, the device corresponding to the high demands, it is understood, the China manufacturers are already some devices, such as cooperation with Baidu supply module with a data center. One of the requirements of the data center optical devices are high-speed, server interfaces are from 1G to 10G, and aggregation switches from 10G to 40G/100G; Second, the cost is low, because the data center requires a lot of applications; third requirement is also lower power consumption, because the power consumption is very large data centers. Therefore, the device should adapt to the data provider development needs of server interfaces and aggregation switches to upgrade and evolution; improve production efficiency to reduce costs and reduce power consumption components.

As an professional manufacturer & provider of fiber optic transceivers, we supply sfp transceiver module, xfp transceiver module etc. what’s more we also supply other fiber optic products, such as dwdm muxfiber pigtails, fiber optic testers and tools and so on.

# FS.COM Supply 100GHz DWDM Mux Demux

DWDM Mux and DWDM Demux are designed to multiplex DWDM channels into one or two fibers. 100GHz DWDM Mux Demux is used to provide 100GHz transport solution for DWDM networking system. The common configuration is 4, 8, 16 and 32 channels, and we also have 40 and 96 channels. They are available in plug-in module and standalone 19″ 1RU or 2RU rack mount. These DWDM modules passively multiplex the optical signal outputs from 8 or more electronic devices, send them over a single optical fiber and then de-multiplex the signals into separate, distinct signals for input into electronic devices at the other end of the fiber optic link. We provide option of DWDM expansion port, monitor ports, 1310nm wideband port for existing 1310nm equipment.

AWG DWDM Modules – Planar Technology
FS.COM Thermal Arrayed Waveguide Grating (TAWG) DWDM modules are part of a series of high performance products based on silica-on-silicon planar technology. Our TAWG DWDM modules are designed for use within the C-band release of DWDM system. To decrease the power dissipation of the devices in different environmental conditions, the AWG package is special designed with selection of reliable thermal plastic with low thermal conduction, and the AWG operating temperature is controlled by using foil resist heater or Peltier TEC with thermistor temperature sensor.

FS.COM 100GHz DWDM Mux Demux Solution
We supply common configuration 8, 16, 40 and 96 channels which is available in plug-in module and standalone 19″ 1RU/2RU rack mount. FS.COM provide option of DWDM expansion port, monitor ports, and 1310nm wideband port for existing 1310nm equipment. DWDM transceivers from FS.COM are together used in a cost effective way. DWDM is a proven technology, which offers flat channel bandwidth, flexible channel configuration, low insertion loss and high isolation. Modules are available on the C bands, ITU 100GHz grid at channel spacing of 100GHz.

DWDM MUX and DEMUX Types
1. DWDM MUX DEMUX with Monitor Port
Many technicians will add a monitor port on DWDM MUX/DEMUX for better network monitoring and management. If you choose a single-fiber DWDM MUX DEMUX, the monitor port should be a simplex fiber optic port. For dual-fiber WDM MUX DEMUX, you can add a duplex monitor port for the whole network monitoring, or just add a simplex port for MUX or DEMUX monitoring.

2. DWDM MUX DEMUX with Expansion Port
Expansion port added on DWDM MUX DEMUX is really useful. If you installed a DWDM network which just using several of the DWDM wavelengths, you can use this expansion port to increase the network capacity by connecting the expansion port with the line port of another DWDM MUX DEMUX supporting different wavelengths. Then the network of this CWDM network can be increased easily.

3. DWDM MUX DEMUX with 1310 Port
The 1310nm port is used in some legacy networks and sometimes as a return path. If an existing legacy network is using 1310nm port and they have exhausted all fibers and are looking for ways to increase their network capacity they can add in other DWDM wavelengths on to the same fiber while still allowing the use of the 1310nm port. Meanwhile, it can carry LR optics, LX optics etc.

FS.COM, as a 3rd party OEM manufacturer, we supply various 100GHz DWDM MUX DEMUX. Customer can select DWDM wavelength from ITU Grid C-Band C15 to C62. Customer can select LC/UPC, LC/APC, SC/UPC, SC/APC, FC/UPC, FC/APC, ST/UPC, ST/APC etc as connectors. Customer can select plug-in module or 1RU rack mount chassis as housing. Customer can add monitor port, expansion port and 1310 port. As a professional optical communication products manufacturer, we also supply CWDM MUX, 100G DWDM Muxponder, and FMT DWDM Optical Transport Network System.