Know the Difference between CWDM and DWDM

A WDM (Wavelength Division Multiplexing) is a system that uses a multiplexing (at the transmitter) and a demultiplexer (at the receiver) for the completion of the process and transmission of the signals.

The WDM is divided into three types (WDM, CWDM and DWDM) on the basis of wavelength difference among the three. The article discusses the main differences among CWDM and DWDM.

CWDM stands for Coarse Wavelength Division Multiplexing, and DWDM is the acronym for Dense Wavelength Division Multiplexing. Whether DWDM or CWDM, both are the types of WDM mechanism and have an array of differencess.

Let’s get acquainted with the chief difference between CWDM and DWDM:

• The Coarse WDM has less than 8 active wavelengths per optical fiber whereas the DWDM has more than 8 active wavelengths per optical fiber.
• The CWDM has lower capacity strength and hence is low in costs; conversely the DWDM possesses high capacity –this leads to an augmented price which is worth its qualities.
• When it comes to the difference between the distance of the two, the CWDM has short range communication because the wavelength is not amplified, and DWDM has long range communication.
• CWDM Mux and Demux systems are developed to be used in multiplexing multiple CWDM channels into one or two fibers.
• Another major difference is that DWDM systems are made for longer haul transmittal, by keeping the wavelengths closely packed. Also, a DWDM device can transmit more data over long distances and to a significantly larger run of cable with lesser interference than a comparable CWDM system which has a shorter haul transmittal.
• Furthermore, the Dense Wavelength Division Multiplying systems are capable to fit more than forty different data streams in the amount akin to that of fiber used for two data streams in a CWDM system.

Apart from all the difference there is one more and that is wavelength drift is possible in CWDM, but when it comes to the DWDM –precision lasers are needed to keep channels on the target.

Beyond being different from each other –these systems play different roles in the effective transfer of the signals, and thereby both are important enough.

Know Wave Division Multiplexing & its Working

The world knows that the physical fiber optic cabling can be a lot expensive when it comes implementing for every service separately; but this expense can be made worthy by capacity expansion using a Wave Division Multiplexing also known as WDM.

Wave Division Multiplexing technology was evolved to expand aptitude of networks that a single fiber provides. It helps because a WDM system employs a multiplexer solution at the transmitter that combines several wavelengths in concert; also in this entire process, each carries sundry signal and at the receiver –a de-multiplexer helps in splitting them apart. Both Mux and Demux are passive and thereby require no power supply.

Types of WDM

Currently there are many kinds of standardized WDM in existence. The types / kinds of Wave Division Multiplexing are:

• General WDM (that may include 980/1550 WDM and 1310/1550 WDM).
• CWDM (such as CWDM Mux and Demux module and CWDM OADM module).
• DWDM (including 50GHz, 100GHz, 200GHz DWDM mux/demux module and DWDM OADM module).

How WDM works?

The operating principle of WDM is easy and understandable. Wave Division Multiplexing is akin to the prism in the operating principle; as a prism separates white light into seven different colored rays, similarly a WDM system uses a multiplexer at the transmitter to join different signals together, and has a demultiplexer at the receiver end for splitting the signals apart. All you need is a right type of fiber optic cable, and it is possible to have a WDM device that can do both simultaneously, and can act as an optical add / drop multiplexer.

The first WDM systems (which were demonstrated with optical fiber in the early 80s) combined only two signals; however, modern systems can handle up to 160 signals. In short, WDM systems can expand the capacity of the network while accommodating many generations of technology development in optical infrastructure without having to revamp the backbone network; this quality plays in its popularity with telecommunications companies.

Data Bottleneck Solutions for your Business with Compact CWDM Mux and Demux

Communication networks are vulnerable to data congestion. This limits the end users from accessing certain links including mobile radio towers. The problem has led to management of dedicated links by a large number of wireless carriers through the optical fiber network connection.

Depending on the requirement standards the service provider is expected to comply, some even go to the extent of claiming additional dedicated strands which give access and core meshes to the mobile tower sites.  This trend depletes the number of available fiber strands denying new service providers access to mobile towers.

Thanks to the art of technology which has introduced data bottleneck solution to businesses. The compact CWDM multiplexer allows fiber capacity enhancement without the need to increase the number of fiber strands. This ensures easy communication and connectivity to mobile towers by giving quick access without bugs.

Features

• High channel isolation
• Mini size
• High insertion loss
• Epoxy-free optical path
• Large bandwidth

Applications

• Mobile phone applications
• WDM network
• Access network
• Tele-communication
• Fiber optic amplifier

How it works

Compact CWDM multiplexer works by either extracting or inaugurating several signals which are broadcasted through different fiber wavelengths to efficient create more different channels. A MUX conglomerates individual light channels to the fiber at the sending end of the data link.

 On arrival, a demultiplexer (DEMUX) applies a similar optical conformation in a reverse direction, propagating via the device. The DEMUX optical filter singles out the incoming wavelengths and pairs each channel separately with fiber. This increases the number of channels transmitted through the fiber.

As the demand for more subscribers continues to grow, the CWDM scales the supply of additional bandwidth by handling bottlenecks without substantial equipment modification. According to the IEEE standards. CWDM is compact and has the capability of withstanding outside plant (OSP) environmental conditions. This allows deployment of uncooled and unheated equipment and cabinets.

Advantages

Saves money

CWDM helps access network operators lower their costs by providing quality connections to their users without the need of investing on more fiber links.

High quality

Compact CWDM is designed using modern technology and complies with IEEE standards making service providers meet the global communication standards. Besides, the device has the capability of withstanding outside the plant environmental conditions giving providers favorable installation conditions.

Reduces data bugs

Networks are prone to bottlenecks. However, the device scales additional bandwidth without the need of substantial modification of the device. This ensures quick access to links despite the increase in the number of subscribers. This has enabled users to enjoy high-speed internet, telephony services, and on-demand videos without limited access.

Before making use of this new technology, access network operators must satisfy the following requirements.

1. Bandwidth of up to 10Gps for each first-time backhaul link
2. Facility to storing stable legacy fiber connections of between 15510nm or 1310nm
3. Typical spans of up to 80km
4. Uncomplicated operations which are reliable
5. Wireless carrier segregation bandwidth
6. Packaged and long-lasting environmental constraints for installation

Introduction of Fiber Optic Coupler with its Benefits & Classification

A fiber optic coupler is an indispensable part of the world of electrical devices. Without these no signals would be transmitted or converted from inputs to outputs. This is the reason these are so important thereby this article discussed about these, introduction, classification and benefits in detail.

Fiber Optic Coupler is an optical cog that is capable of connecting single or multiple fiber ends in order to permit the broadcast of light waves in manifold paths. This optical device is also capable of coalescing two or more inputs into a single output while dividing a single input into two or more outputs. In comparison to a connector or a splice, the signals may be even more attenuated by FOC i.e. Fiber Optic Couplers; this is due to the division of input signal amongst the output ports.

Types of Fiber Optic Coupler

Fiber Optic Couplers are broadly classified into two, the active or passive devices. For the operation of active fiber coupler an external power source is required, conversely no power is needed when it comes to operate the passive fiber optic couplers.

Fiber Optic Couplers can be of different types for instance X couplers, PM Fiber Couplers, combiners, stars, splitters and trees etc. Let’s discuss the function of each of the type of the Fiber Optic Couplers:

Combiners: This type of Fiber Optic Coupler combines two signals and yields single output.

Splitters: These supply multiple (two) outputs by using the single optical signal. The splitters can be categorized into T couplers and Y couplers, with the former having an irregular power distribution and latter with equal power allocation.

Tree Couplers: The Tree couplers execute both the functions of combiners as well as splitters in just one device. This categorization is typically based upon the number of inputs and outputs ports. These are either single input with a multi-output or multi-input with a single output.

PM Coupler: This stands for Polarization Maintaining Fiber Coupler. It is a device which either coalesces the luminosity signals from two PM fibers into a one PM fiber, or splits the light rays from the input PM fiber into multiple output PM fibers. Its applications include PM fiber interferometers, signal monitoring in its systems, and also power sharing in polarization sensitive systems etc.

Star Coupler: The role of star coupler is to distribute power from the inputs to the outputs.

Benefits of Fiber Optical Couplers

There are several benefits of using fiber optic couplers. Such as:

• Low excess loss,
• High reliability,
• High stability,
• Dual operating window,
• Low polarization dependent loss,
• High directivity and Stumpy insertion loss.

The listed benefits of Fiber Optical Couplers make them ideal for many applications for instance community antenna networks, optical communication systems and fiber-to-home technology etc.

Optical Filters: Filter stacks transmit wide-angle incident light without shifting wavelength(2)

To avoid the problem of color change versus incidence angle in an optical system, thin-film-coated filter elements can be replaced by a filter consisting of a stack of different filter glasses.

JASON KECK

Wide-angle filter stack apps

There is a multitude of applications for this type of filter. In the field of digital imaging, colorimeters-which take wideband spectral energy readings-are used to profile and calibrate display devices, verifying that pixel color and intensity at the edge of a display matches the performance of pixels in the center of the display.

In astronomy, biomedical or fluorescence imaging, and mineralogy, hyperspectral imaging has many important applications. It is essential that the incident light undergo as little iridescence as possible. Also, when precision imaging instruments are expensively launched into orbit, the filters must be robust enough to withstand extreme environmental operating conditions.

In agriculture, the color of crops or food products reveals vital information. The use of Earth-observing satellites to measure the "vegetation index" of crops (a measurement of green hue) is nothing new, but the affordability of aerial drones has brought new possibilities. A drone can be programmed with GPS data to fly on a fixed pattern over a designated crop area and take wide-angle images at regular intervals, building up a picture of the vegetation index of crops. If the images used in such applications provide accurate spectral data that is as free as possible from iridescent distortion, it can give farmers precise control over fertilizer application rates and greatly improve efficiency and productivity. This is a considerable cost saving over low-resolution, narrowband satellite imagery and conventional aerial photography using manned aircraft.

Design hurdles

There are three complicating factors in the design of such filter stacks. The first is the limited choice in filter glass, limited not only by manufacturer availability but also by physics. Filter glass with an ideal edge cut-on or cut-off wavelength for an application is not always easy to find, or may be impossible to precisely manufacture. Where it is available, the designer is then limited by what the manufacturer can deliver in a reasonable time, as melts may be scheduled as infrequently as once every several years, depending on demand.

The second factor is that, while the perfect filter glass for a particular application may not exist, there are hundreds of other glass types from numerous vendors that can be combined to achieve a close approximation of the requirement.

The third complicating factor is that the design of ColorLock filters is a massively multidimensional, nonsmooth optimization challenge. Physical manufacturing requirements restrict the thickness of all combined individual layers to not exceed the overall thickness requirement of the resulting optical component, further putting restrictions on the selection of specific CWDM filter glass types.

Reynard streamlined this complex design process by developing in-house software into which all of the system requirements are fed. The software produces a manufacturable design for a filter in which the necessary materials are combined at the correct thickness in each layer. The design is then manufactured and validated for performance.

About DK Photonics

DK Photonics – www.dkphotonics.com  specializes in designing and manufacturing of high quality optical passive components such as 8CH CWDM Module,100GHz 8CH DWDM,200GHz DWDM,Mini-size CWDM,compact CWDM,Athermal AWG DWDM Module,100GHz AWG,Thermal AWG DWDM Module,1310/1490/1550nm FWDM, PLC Splitter, Optical Circulator,Optical Isolator,Fused Coupler,Mini Size Fused WDM.

Optical Filters: Filter stacks transmit wide-angle incident light without shifting wavelength(1)

To avoid the problem of color change versus incidence angle in an optical system, thin-film-coated filter elements can be replaced by a filter consisting of a stack of different filter glasses.

JASON KECK

Wide-angle imaging systems have to overcome numerous problems. Distortion of the shape of objects in the scene is the predominant issue, recognizable as the "fish-eye lens" look that is often corrected in software. However, lens distortion is not the only problem.

Iridescence, or the change in transmitted or reflected color of light viewed from different angles, is a phenomenon that can be found both in nature and in artificial light-detecting systems with precise color requirements, where it can cause many problems.

Wide-angle color-sensing applications commonly require that a CWDM wavelength must be detectable regardless of the incident angle. Iridescence through a thin-film-coated optical element can cause problems in this situation by distorting the spectral transmission of light coming from peripheral objects.

Maximizing light transmission in a thin-film WDM coating's passband while blocking out-of-band light is a requirement for coated optical components such as dielectric filters; however, the wavelength's transition commonly only remains steady within relatively narrow cone angles. Beyond angles of 5°, such filters are susceptible to iridescence, observable as a change of color, or "blueshift." As the angle of light entering the filter increases, the light propagates through more of each thin-film stack layer, altering the apparent overall thickness of the optical-filter stack and affecting the performance of the original intended design. This can make such filters unsuitable for wide-angle imaging applications with bright illumination and where higher standards of consistency are required of the wavelength of all incident light.

One of the more convoluted wide-angle imaging solutions is the use of a cluster of cameras or a polycamera, pointing in various directions like the compound eye of an insect; the resulting multiple pictures are then assembled into one image in software. Although the light entering each camera thus fills only a narrow cone angle, the complexity and resultant high expense of such a system is obvious.

Engineers at Reynard have addressed this problem in a single optical device with a system in which two or more layers of filter glass are combined into a stacked configuration. These ColorLock filter stacks eliminate the wavelength shift as incident angle increases and are customized to meet specific system needs.

Software is used to determine the exact composition and thickness of the layers in these filters; the software determines a merit function that best estimates the filter requirements and allows filter stacks to be designed for band pass, short-wave pass, long-wave pass, or user-specified functions. Incident angles can be as high as 50° without any shift in the transmitted wavelength, while more traditional coated filters with the same conditions would see a significant shift toward shorter wavelengths.

 

About DK Photonics

DK Photonics – www.dkphotonics.com  specializes in designing and manufacturing of high quality optical passive components such as 8CH CWDM Module,100GHz 8CH DWDM,200GHz DWDM,Mini-size CWDM,compact CWDM,Athermal AWG DWDM Module,100GHz AWG,Thermal AWG DWDM Module,1310/1490/1550nm FWDM, PLC Splitter, Optical Circulator,Optical Isolator,Fused Coupler,Mini Size Fused WDM.