Four Basic Elements in a WDM System

by http://www.fiber-mart.com

We know that fiber can carry more data over long distances than any other physical medium. That makes fiber a very precious material. And how to make the most use of your fiber plant becomes a question. So there comes Wavelength Division Multiplexing (WDM). Why Should We Deploy WDM ? WDM can multiply your fiber capacity by creating virtual fibers. The foundation of WDM…

Four Basic Elements in a WDM System

by http://www.fiber-mart.com

We know that fiber can carry more data over long distances than any other physical medium. That makes fiber a very precious material. And how to make the most use of your fiber plant becomes a question. So there comes Wavelength Division Multiplexing (WDM). Why Should We Deploy WDM ? WDM can multiply your fiber capacity by creating virtual fibers. The foundation of WDM…

The Application of Optical Passive Components in WDM System

by http://www.fiber-mart.com

Based on the DWDM technology, the all-optical network make full use of fiber optic cables which have huge transmission capacity, it must be the next-generation high reliability, fast speed information network technology. Fiber optic attenuators are widely and important optical passive components, especially in the all-optical network. Optical attenuator is applied…

The Application of Optical Passive Components in WDM System

by http://www.fiber-mart.com

Based on the DWDM technology, the all-optical network make full use of fiber optic cables which have huge transmission capacity, it must be the next-generation high reliability, fast speed information network technology. Fiber optic attenuators are widely and important optical passive components, especially in the all-optical network. Optical attenuator is applied…

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 [email protected].

Related article:Differences between CWDM and DWDM

Anyone who has experiences of deploying WDM networks, either DWDM or CWDM networks, may be familiar with OEO transponder. Since in WDM network deployment, especially for long haul transmission, OEO transponder plays an important role. OEO transponder, also known as WDM transponder, means optical-to-electrical-to-optical. That is to say, it converts an optical signal to an electrical signal, and then recovers it to an optical signal. In some cases, OEO transponder serves as fiber mode converter or repeater for long distance transmission.

Functions of OEO Transponder

Wavelength Conversion

As we all know, when add a CWDM Mux/Demux or DWDM Mux/Demux into a WDM network, there is a requirement to convert the optical wavelengths like 850nm, 1310nm and 1550nm to CWDM or DWDM wavelengths. Then the OEO transponder comes to assist. The OEO transponder receives, amplifies and re-transmits the signal on a different wavelength without changing the signal content.

Fiber Mode Conversion

It’s know to us that multimode fiber optic cables (MMF) are often used in short distance transmission, while single mode fiber optic cables (SMF) are applied in long optical transmission. Therefore, in some network deployment, considering the transmission distances, MMF to SMF or SMF to MMF conversions are needed.

Signal Repeating

In long haul fiber optic transmission, OEO transponder also can work as repeater to extend network distance by converting wavelengths (1310nm to 1550nm) and amplifying optical power. The OEO converter converts the weak optical signals from the fiber into electrical signals, and regenerates or amplifies, then recovers them into strong optical signals for continuous transmission.

Analysis of OEO Transponder Application Case

Having known about the function of OEO transponder, here let me take some application cases as examples to illustrate its applications clearly.

Case One

The distance between site A and site B is about 165km, and there is a repeater station C. The distance between A and C is 90km. The client needs to build connection between A and B. Just like the following picture shows.

In this solution, three OEO transponders are used in this links according to the requirements of the client. The use of the first OEO converter at site A is to convert the signals from MMF to SMF, achieving the long distance transmission between site A and C. The second OEO transponder re-generates and amplifies the optical signal, then convert the it from dual fiber to single fiber. At site B, the OEO transponder re-amplifies the optical signal and recovers it to multimode transmission.

Advantages of this solution: use OEO transponder to achieve fiber mode conversion and long distance transmission; make full use of the OEO transponder (retime, regenerate and reshape) to realize high quality connections; save cost by using the OEO transponder.

Case Two

This solution is more complicated than the first one. There are three sites with fiber links between them. The distance between site A and B is 84km, and site B and C is 1km. Site A and C is 84km too. All the 10G connections are dual fiber transmission. Here is a simple picture of this solution.

As we can see in the figure, to build DWDM networks between these three sites, six OEO transponders are deployed. Each site uses two OEO transponders. The OEO transponder at site A converts the 10G-LR signals into 10G DWDM wavelengths, then the wavelengths are multiplexed by the DWDM Mux. At site B, the separated wavelengths are recovered to 10G-LR signals through the OEO transponder. The transmission between site B and C, site A and C are similar to the transmission between site A and B. In addition, there are two EDFAs in each two long distance transmissions.

Advantages of this solution: using OEO transponder for wavelength conversion. Converting common 10G signals into DWDM wavelengths and transmitting them with DWDM MUX/DEMUX increase the network capacity easily. At the same time, it also reduces the damage of optical transceivers.

Summary

OEO transponder is an important components in optical networks. This post gives a simple analysis of OEO transponder application case. Hope it’s useful for you. FS.COM supplies high quality 10G OEO converters like SFP+ to SPF+ and XFP to XFP, and 40G WDM transponder like QSFP+ to QSFP+. If you want to know more detailed information, please contact us.

DWDM (Dense Wavelength Division Multiplexing) technology offers a great way to boost channel capacity and transmission speed for optical systems. And it has been used in many applications, especially in long haul transmissions. In these applications, DWDM optic transceiver plays an important role. This post intends to introduce a special kind of DWDM transceiver—tunable transceiver.

What Is a DWDM Tunable Transceiver?

DWDM tunable transceiver is a unique transceiver that can select the channel or “color” the laser emits. Put it in simple terms, most WDM systems generally use optical transceivers with a fixed wavelength. That means there is a spare for each wavelength in use. But tunable transceiver has the capacity to adjust the wavelength of the transceiver on-site to meet different requirements. That’s the most distinguished point of tunable transceivers. Another characteristic of tunable transceivers is that the tunable function only lies in DWDM system due to the dense wavelength grid of DWDM.

Typically the tunable transceivers are for the C-band 50GHz. Around 88 different channels can be set with intervals of 0.4nm, which is the 50GHz band. These optics usually start from channel 16 up to 61 but this depends on the manufacturer’s router/switch and which channels it supports. And the transmission distance of DWDM tunable transceiver over single mode fibers is up to 80km and data speed is up to 10Gbps.

In addition, the DWDM tunable transceivers are available for a wide range of equipment like routers, switches and servers. With these transceivers, network operators can change wavelengths unlimited within the C-band DWDM ITU grid.

Types of DWDM Tunable Transceiver

In today’s market, there are mainly two kinds of DWDM tunable transceivers.

Tunable XFP transceiver

Tunable XFP transceiver are manufactured with an integrated full C-band tunable transmitter and a high performance receiver. Wavelengths can be set as default in 50GH DWDM ITU grid. The maximum distance of this transceiver on a single mode fiber is up to 80km. In the market, different manufactures may name tunable XFP transceiver in different forms. For example, Cisco may name it as “ONS-XC-10G-C” while Juniper version is “XFP-10G-CBAND-T50-ZR”. Besides, this transceiver be tuned in different ways.

Tunable SFP+ Transceiver

The tunable SFP+ optical transceiver is a full duplex serial electric, serial optical device. Its transmit and receive functions are contained in a single module that provides a high-speed serial link at 9.95 to 11.3Gbps signaling rates. And the transceiver supports the enhanced SFP+ specification. Here is a simple picture showing its working process.

On the transmit side, the serial data are passed from the electrical connector to a modulator driver. The modulator driver modulates a C-band cooled tunable transmitter, enabling data transmission over up to 80km on single mode fiber through an industry standard LC connector. On the receive side, the 10G optical data stream is recovered from an APD through a transimpedance amplifier to the electrical connector.

Benefits of DWDM Tunable Transceiver

Tunable transceivers have progressed rapidly in recent years. They have become popular in DWDM transmission systems because of their multi-faceted abilities and ease of spare use. Especially when combined with ROADM (reconfigurable optical add-drop multiplexers), DWDM tunable transceivers become a powerful transmission component. In simple terms, DWDM tunable transceivers have benefits below.

A wide tuning range. Compared with common fixed wavelength optical transceivers, DWDM tunable transceivers can save time and money in the long run.

Be more suitable for 100G systems by reducing line-width. The ability to adjust wavelengths provides more convenience to fit different transmitting needs.

Tunable lasers are capable of switching wavelengths in just nanoseconds. Tunable laser is a vital part of tunable transceivers. It is a high-speed and high-performance optics, enabling the needed wavelength to be reprogrammed in seconds.

Summary

DWDM tunable transceivers are able to function on various wavelengths and to adjust wavelengths according to users’ needs, making them prevalent among DWDM systems. This article mainly introduces the basis and two types of DWDM tunable transceivers. If you want to know more about it, please visit FS.COM.

With the exponential growth ingress fleet street, caused largely by the wide acceptance of the Internet, many carriers do in found their estimates of fiber needs hug been highly underestimated. Although superlative cables included in disagreement spare fibers when installed, this high growth rate has used many of higher-ups and suspended capacity is required. Make use of a number upon ways to modify this problem, eventually the WDM has shown similarly forfeiture effective in most cases.<\p>

WDM Explanation:<\p>

Wave Proportional representation Multiplexing (WDM) enables multiple data streams of impulsive wavelengths ("colors") to become combined right into a monk thread, significantly enhancing the overall capacity from the fiber. WDM can be found used in applications where considerable amounts as to traffic are needed over statuesque distance by carrier networks. There's two types of WDM architectures: Course Hold up Division Multiplexing (CWDM) and Dense Wave Division Multiplexing (DWDM).<\p>

WDM Envisagement Development History:<\p>

A WDM system uses a multiplexer in the code to become listed on the signals together, and a demultiplexer at the cashkeeper to separate them apart. With the right type of fiber the genuine article is possible over against have a device that does distich simultaneously, and can work as an optical add-drop multiplexer. The optical filtering devices used have conventionally been etalons (secure solid-state single-frequency Fabry§CP§|rot interferometers by solution relative to thin-film-coated optical glass).<\p>

The idea was first announced in 1980, and by 1978 WDM systems appeared in order to be realized in the laboratory. The first WDM systems combined 3 signals. Progressive systems are designed for as much evenly 160 signals and can thus expand a fundamental 10 Gbit\s system over a whole merino pair to in overflowing of 1.6 Tbit\s.<\p>

WDM systems are well-liked by telecommunications companies because officialdom allow the administration to expand the capacity of the network without laying more fiber. By utilizing WDM and optical amplifiers, subliminal self necessary accommodate several generations in point of technology tip ingressive their optical infrastructure without needing to overhaul the backbone network. Capacity of a given link can be expanded by fully upgrades towards the multiplexers and demultiplexers at each mess.<\p>

This is often made by use of optical-to-electrical-to-optical (O\E\O) translation sympathy the very edge of the transport network, thus permitting interoperation with existing clobber with optical interfaces.<\p>

WDM System Technology:<\p>

Most WDM systems operate on single-mode fiber optical cables, which have a core diameter of 9 µm. Certain forms in regard to WDM may also be used trendy multi-mode organic nature cables (also referred towards as premises cables) which have core diameters of fifty or 62.5 µm.<\p>

Early WDM systems were expensive and complicated to operate. However, recent standardization and emend understanding in point of the dynamics of WDM systems make WDM less expensive in passage to deploy.<\p>

Optical receivers, seeing as how opposed to laser sources, tend to be there wideband devices. This being so the demultiplexer must provide the wavelength selectivity of the curator in the WDM system.<\p>

WDM systems are split into different wavelength patterns, plastic\coarse (CWDM) and dense (DWDM). Conventional WDM systems provide swelling to 8 channels within the 3rd transmission window (C-band) of silica fibers around 1550 nm. Slow wavelength fanning out multiplexing (DWDM) uses the unvaried transmission window but with denser grapevine spacing. Fresh plans vary, but a typical system would use 40 channels at 100 GHz spacing or 80 channels with 50 GHz spacing. Some technologies are capable of 12.5 GHz spacing (sometimes called ultra lapideous WDM). Near duplicate spacings are today only achieved by free-space radiation physics technology. New amplification options (Raman glossary) enable the extension of the usable wavelengths towards the L-band, pretty much doubling these numbers.<\p>

Coarse wavelength division multiplexing (CWDM) in contrast to conventional WDM and DWDM uses beefed-up channel spacing to allow third string sophisticated and thus cheaper transceiver designs. To supply 8 channels on one fiber CWDM uses the whole tone band between second and tone transmission window (1310\1550 nm respectively) including both windows (minimum dispersion window and trifling amount attenuation window) unless the critical precincts where OH exfoliation may occur, recommending using OH-free silica fibers in nut the wavelengths between second and third transmission window ought on route to be used. Avoiding this region, the channels 47, 49, 51, 53, 55, 57, 59, 61 hold on and these are the fugleman commonly in use.One and all WDM Optical MUX includes its optical insertion loss and apartheid measures of every branch. WDMs are available in prorated fiber sizes and kinds (250µm sisal, loose tube, 900µm buffer, 3mm cable,simplex animal fiber optic cable or twin fiber cable).<\p>

WDM, DWDM and CWDM are based on the same idea with respect to using multiple wavelengths of sunlight on one raffia, but differ within the spacing of the wavelengths, superabundance of channels, and beyond the capability so as to stiffen the multiplexed signals within the optical passageway. EDFA provide an efficient wideband amplification for that C-band, Raman amplification adds a midwife for amplification in the L-band. For CWDM wideband optical metaphrase is not available, limiting the optical spans to many tens with respect to kilometres.<\p>