#cwdm oadm

by Fiber-MART.COM

For a better signal transmission in fiber-optic communication, different kinds of technologies are applied to the industry. Wavelength-division multiplexing (WDM) is one of the commonly used technologies which multiplexes a number of optical carrier signals onto a single optic fiber by using different wavelengths of laser light. That is to say, WDM enables two or more than two wavelength signals to transmit through different optical channels in the same optical fiber at the same time.

In the WDM system, there are two types of divisions –

CWDM

(coarse wavelength division multiplexing) and DWDM (dense wavelength division multiplexing). They are both using multiple wavelengths of laser light for signal transmission on a single fiber. However, from the aspects of channel spacing, transmission reach, modulation laser and cost, CWDM and DWDM still have a lot of differences. This article will focus on these distinctions and hope you can have a general understanding about CWDM and

DWDM

technology. Channel SpacingAs their names suggest, the words “coarse” and “dense” reveal the difference in channel spacing. CWDM has a wider spacing than DWDM. It is able to transport up to 16 wavelengths with a channel spacing of 20 nm in the spectrum grid from 1270 nm to 1610 nm. But DWDM can carry 40, 80 or up to 160 wavelengths with a narrower spacing of 0.8 nm, 0.4 nm or 0.2 nm from the wavelengths of 1525 nm to 1565 nm (C band) or 1570 nm to 1610 nm (L band). It is no doubt that DWDM has a higher performance for transmitting a greater number of multiple wavelengths on a single fiber. Transmission ReachSince the wavelengths are highly integrated in the fiber during light transmission, DWDM is able to reach a longer distance than CWDM. The amplified wavelengths provide DWDM with the ability of suffering less interference over long-haul cables. Unlike DWDM system, CWDM is unable to travel unlimited distance. The maximum reach of CWDM is about 160 kilometers but an amplified DWDM system can go much further as the signal strength is boosted periodically throughout the run. Modulation LaserCWDM system uses the uncooled laser while DWDM system uses the cooling laser. Laser cooling refers to a number of techniques in which atomic and molecular samples are cooled down to near absolute zero through the interaction with one or more laser fields. Cooling laser adopts temperature tuning which ensures better performance, higher safety and longer life span of DWDM system. But it also consumes more power than the electronic tuning uncooled laser used by CWDM system. CostBecause the range of temperature distribution is nonuniform in a very wide wavelength, so the temperature tuning is very difficult to realize, thus using the cooling laser technique increases the cost of DWDM system. Typically, DWDM equipment is four or five times more expensive than CWDM equipment. ConclusionCWDM and DWDM are both coming from the WDM technology that is capable of conveying multiple wavelengths in a single fiber. But with different characteristics, people should think twice before choosing the CWDM or DWDM system. CWDM usually costs less but its performance is far behind DWDM. Both your requirements and budget need to be taken into consideration. Moreover, the WDM products including CWDM mux/demux module, DWDM mux/demux module and

optical splitter

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

OADMAs the quick development of telecommunications, people’s requirements for bandwidth continue growing. Optical network operators have to face great challenges to meet the demand. In this case, OADM appears. How much do you know about OADM? This article will introduce it for you.

OADM Overview

OADM, or optical add-drop multiplexer, is a passive optical device used in WDM technology. Its main function is to selectively separate or add optical signals or multiplex wavelength from one stream of light on a single fiber while other uncorrelated signals will not be affected. According to the wavelength, OADM has passive and active modes. In passive OADM, the add and drop wavelengths are fixed in advance, and it uses thin-film interference filters, fiber gratings, and planar waveguides in networks with WDM systems. Different from passive OADM, active OADM can be set to any wavelength after installation. And it is also more flexible and cheaper than passive OADM.

A traditional OADM consists of three stages: an optical demultiplexer, an optical multiplexer, and between them a method of re-configuring the paths between the demultiplexer, the multiplexer and a set of ports for adding and dropping signals. The demultiplexer separates wavelengths in an input fiber onto ports. The reconfiguration can be achieved by a fiber patch panel or by optical switches which direct the wavelengths to the multiplexer or to drop ports. The multiplexer multiplexes the wavelength channels that are to continue on from demultiplexer ports with those from the add ports, onto a single output fiber.

Types of OADM

Fixed optical add drop multiplexer (FOADM) and re-configurable optical add drop multiplexer (ROADM) are the two common types of OADM.

Fixed Optical Add-Drop Multiplexer (FOADM)

FOADM, sometimes also called configurable optical add drop multiplexers, can add or drop a fixed type or multiple fixed wavelength. In fixed-wavelength OADM, the wavelength has been selected and remains the same until human intervention changes it. FOADMs allow the manufacturers to customize the number of channels, filter specifications, and power equalization but require excessive transporters at each node. Although fixed optical add drop multiplexers lack of flexibility, they have more reliable performance and small delay.

Re-configurable Optical Add-Drop Multiplexer (ROADM)

ROADM is a device that can add, block, pass or redirect modulated infrared (IR) and visible light beams of various wavelengths in a fiber optic network. A laser tuned to a particular wavelength can electronically change the selected channel routing through the optical network. Hence, the ROADM provides flexibility for rerouting optical streams, and at the same time it can bypass wrong connections and allow minimal service disruptions.

Before ROADMs appear, signal routing in fiber optic networks was realized by converting the IR or visible beams to electrical signals and routing those signals using conventional electronic switches. The rerouted electrical signals were then converted back into IR or visible beams. Now with the application of ROADM, singles can be easily handled. Therefore, ROADM is widely used in systems that employ wavelength division multiplexing.

Application of OADM

As people’s requirements for bandwidth grow rapidly, network mangers not only need to satisfy this demand, but also face the challenge to keep track of all the wavelengths, monitor their correct operation and deploy new wavelengths easily without increasing the operation cost. However, the optical add-drop multiplexers which can couple two or more wavelengths into the same fiber add the required flexibility, and make it easy to add wavelengths or change the wavelength destination providing more convenient over the entire high capacity infrastructure. Therefore, optical add-drop multiplexer is widely used in long-haul optical communication system and metropolitan area network (MAN).

Besides, optical add-drop multiplexers play an important role in WDM networks. The typical applications are CWDM OADM and DWDM OADM. CWDM OADM is applied to optically add/drop one or multiple CWDM channels into one or two fibers. There are various CWDM OADM modules in our website such as 1CH CWDM OADM, 2CH CWDM OADM, 4CH CWDM OADM, 8CH CWDM OADM, 16CH CWDM OADM, etc. When numerous channels can be transmitted through a single fiber network, only selected channels of information are required at a particular place. At this moment, DWDM OADM can add or remove additional wavelengths in the network and make sure the signals spread correctly. There are 100 GHz and 200GHz DWDM OADM modules available for you.

Conclusion

In today’s world of intensive communication needs and requirements, OADM is a vital component in data networks. It plays a key role in improving the network performance and reliability. Now OADM is still progressing. Its great development prospect cannot be ignored.

In order to research the present situation and the existing problems about CEDM technology, Fiberstore invited some equipment manufacturers include Huawei, Shanghai bell alcatel(asb), CIENA, light bridge, Fire network to test CWDM equipments. Main test content includes: Main optical channel MPI interface, OTU testing, business interface testing (including SDH, Ethernet, transparent rate channel interface, ESCON, etc.); Networking ability tests (including CWDM OADM ring type network, point-to-point, chain type, bi-directional single fiber, etc.), optical layer protection function test, network management function test, reliability (high and low temperature, humidity, vibration, etc.) and equipment safety testing. Through this test, we find the current CWDM technology has the following main features:

1. As a result of E band optical transceiver module technology is not mature, so the vast majority of products are 8 (1470 nm to 1610 nm), because of CWDM technology located in the edge of the metropolitan area network layer, so the related products are designed as cartridge products, and And you can expand conveniently through the cascade.

2. CWDM support point to point, the chain of chain shaped, ring, ring, bi-directional single fiber and other network mode, It can be flexible to use according to requirements.

3. In general it supports MUX line side to choose 1+1 optical line protection, and OTU layer 1 + 1 optical channel protection through the special protection board.

4. Because of variety of the metropolitan area network business, such as GE, SDH, FE, ESCON, FICON, FC, etc., and rate may reach to 100 Mbit/s~2.5 Gbit/s, protocol transparency and rate of transparency of CWDM make it can be a very good offer for the transmission function of metropolitan area business.

5. Many vendors begin to support electricity layer reuse of business functions, such as Shanghai bell can be 622 m below the rate of different formats of signal multiplexing for 4 x Any board of STM-16 signal, Huawei GEMUX plate can multiplex 2 GE or FC for STM-16.

6. CWDM network management system of performance management and fault management and configuration management exist the problems of weak ability, it need to further improve.

7. The reliability and safety of some CWDM device still exist some shortcomings, such as lack of ALS or APR function, the reliability of the optical transceiver module still needs improvement. These problems are the result of the emphasis on cost reduction.

CWDM technology’s biggest problem is that its cost advantages relative to the DWDM Equipment is still not enough. Optical transceiver modules and optical devices is the key to reduce costs. But due to the small market, supplier shipments is not big, so the device cost advantage is not obvious. Another way to reduce the cost is simplified the function of devices, and this method results in the decrease of system reliability and the management ability. DWDM Price is more and more lower also bring a lot of pressure to CWDM technology, and now use the DWDM technology can form a complete metro DWDM Network, so good scalability, the pressure bring to CWDM is larger. Now CWDM device support the number of optical CWDM channels ( CWDM wavelengths) no more than 8, main reason is that E band optical transceiver module manufacturing process is not yet mature, in addition, eliminating the water absorption peak of G.652 c cables in the application is less, so the market demand for E band optical transceiver module is not big. Higher rate and further transmission distance of CWDM system still have many technical problems. Such as CWDM 10G system dispersion problem, ultra broadband optical amplification technology, etc. In addition, it need to speed up the standardization process, especially it need operators’ guidance in the business interface function aspect.

If you have some needs to buy related CWDM/DWDM optical fiber products, advise you to a professional store to get them. Fiberstore is just a quite right choice.

CWDM, just as DWDM, use multiple light wavelengths to transmit signals over a single optical fiber. However, there are still some differences betwwen the two techologies in many ways.

CWDM uses a 20-nm wavelength spacing that is much wider than the 0.4 nm for DWDM. The wider wavelength spacing in CWDM means lower product development costs. This is one reason why CWDM is less costly than DWDM.

Most CWDM devices operate in the 1470-nm to 1610-nm range. The frequency grid for DWDM and the wavelength grid for CWDM systems are defined by the international telecommunication union (ITU) standard G.694.1 and G.694.2, respectively.

CWDM provides a maximum of 8 lambadas between two CWDM multiplexers over a single fiber pair as compared to DWDM Multiplexers, which support up to 32 lambdas (based on 0.8-nm or 100-GHz wavelength spacing) over a single fiber pair. some long-haul DWDM systems can support up to 160 lambdas per fiber pair.

Each CWDM channels uses a specialized gigabit interface converter (GBIC) or small form-factor pluggable (SFP) transceivers are commonly known as colored GBIC and SFP. Each CWDM channels uses a different "color" GBIC or SFP because each lambda represents a different color in the spectrum. In this case, the native GBIC or SFP in the client devices are substituted with a colored GBIC or SFP.

CWDM multiplexers are usually passive (i.e, not powered) devices containing a very accurate prism to multiplex eight separate wavelengths of light along a single fiber pair. And passive CWDM devices cannot generate or repeat optical signals.

No amplification is possible with CWDM because CWDM uses wavelengths that cannot be amplified with EDFA amplifiers. Therefore, the maximum distance for a CWDM link is approximately 100 km.

The Cisco ONS 15501 EDFA, which has a wavelength range of 1530 nm to 1563 nm, can only amplify two signals (1530 nm and 1550 nm) out of the eight signals that are multiplexed onto the fiber pair.

CWDM provides an alternative solution to DWDM for low-latency and high-bandwidth requirements associated with synchronous replication application. However, DWDM is more scalable than CWDM. DWDM also has a longer distance capacity than CWDM because DWDM can be amplified. The main benefit of CWDM is its low cost. It is a cheaper solution than DWDM. In other words, CWDM is optimized for cost, while DWDM is optimized for bandwidth. For enterprises that have access to dark fiber and have only limited scalability requirement, CWDM is a relatively inexpensive way to achieve low-latency and high-bandwidth interconnections between DCs. The CWDM implementation also results in less complex installation, configuration, and operation as compared to DWDM.

CWDM can be deployed in point-to-point, linear, or fiber protected ring topologies, It is limited to a distance of up to 120 km for Gigabit Ethernet and 100 km for 2-G FC in a point -to-point topology. It is typically used only for extension of the FC fabric in a metro or campus application. As CWDM carries only eight lambdas on a single fiber pair, there are limits to the number of possible drops and the number of sites that can be interconnected. A ring or linear topology reduces the distance depending on the number of OADMs traversed by the CWDM channels because each CWDM OADM introduces additional power loss in the network.

CWDM can also be used to enable multiple ISL connections between the switches over a single fiber since it requires less fiber for interconnecting two metro sites. The same benefit applies to port channel implementation between the switches.

In short, DWDM is a solution that provides a higher number of connections and longer reach, or extension, at a much higher cost while CWDM is a more cost-effective solution for metro or campus solutions where the distance is limited.

If you have any questions about CWDM and DWDM technology, welcome to visit our online store. http://www.fiberstore.com/