Tag Archives: CWDM multiplexer

WDM Multiplexer Is an Ideal Component Optimised for WDM Aplications

Wavelength-division multiplexing (WDM) is a technology which allows multiple signals to be transmitted at different wavelengths over a single optical transmission medium. It can dramatically expand the total capacity of an optical network, for many signals are able to be transported simultaneously. This core technology makes optical network capacity to be gradually efficiently increased to meet the higher demand for bandwidth. To construct WDM networks, a wide range of optical components optimised for WDM applications are required to be researched and created. One of the important components is WDM multiplexer.

WDM multiplexer is an electronic device that uses WDM technology. It is able to combine light signals with different wavelengths coming from different fibrs on toe a single fibre. A multiplexer usually has two signal inputs, one control input and one output. The input end of a WDM multiplexer is coupler that combines all the inputs into one putout fibre. And each channel in a WDM multiplexer is designed to transmit a specific optical wavelength. For example, an 16-channel multiplexer would have the ability to combine sixteen different channels or wavelengths from separate optical fibres onto one optical fibre. And the separated signals will be recovered by another multiplexer called demultiplexer. The following picture shows how the signals are transported.

multiplexer and demultiplexer

WDM multiplexer is available with various configurations such as 2,4, 8, 16, 32, 64, etc. The types of multiplexers can be divided by channel spacing. They can be called CWDM multiplexers, wideband or crossband ones, and DWDM multiplexers, narrowband or dense ones. Compared to DWDM multiplexers, CWDM multiplexers combines signals at fewer channels for its larger channel spacing. CWDM multiplexers is usually with configurations such as 8, 16 and so on, while DWDM multiplexers is commonly with configurations including 32, 96, 128, etc. CWDM multiplexers are able to combine a broad range of wavelengths such as l310 nm and 1550 nm. DWDM multiplexers are able to combines wavelengths with 100 GHz channel spacing. It typically provides a broad range of wavelengths in 1.55-μm region within C-band.

WDM multiplexer, an advanced optical component, is widely used in optical links. It can increase connectivity and bandwidth of processing systems by interconnecting different channels. Most WDM multiplexers employ one of three technologies: arrayed waveguide grating (AWG), filter and dispersive element, primarily diffraction grating. Some multiplexers based on filters exhibit high insertion loss for devices with many channels, which makes them are not suitable in the application of multimode and bi-directional transmission. But the multiplexers with AWG technology offers many advantages over them including low cost for many channels, low loss, little crosstalk, and receiving much attention. With AWG technology, WDM multiplexer is ideal for the application of high throughput optical links in parallel processing and computing.

It is concluded that WDM multiplexer with WDM technology is a key component in optical links and even in the high throughput optical links.

What Are WDM Multiplexer Modules

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What is a multiplexer?

A multiplexer, sometimes referred to as a multiplexor or simply a MUX, is an electronic device that selects from several input signals and transmits one or more output signals. In its simplest form, a multiplexer will have two signal inputs, one control input and one output. One example of an analog multiplexer is the source control on a home stereo unit that allows the user to choose between the audio from a compact disc (CD) player, digital versatile disc (DVD) player and cable television line.

Multiplexers also are used in building digital semiconductors such as central processing units (CPUs) and graphics controllers. In these applications, the number of inputs is generally a multiple of two, the number of outputs is either one or relatively small multiple of two, and the number of control signals is related to the combined number of inputs and outputs. For example, a two-input, one-output multiplexer requires only one control signal to select the input, and a 16-input, four-output multiplexer requires four control signals to select the input and two to select the output.

Type of Multiplexer


Time Division Multiplexer (TDM)

Short for Time Division Multiplexing, a type of multiplexing that combines data streams by assigning each stream a different time slot in a set. TDM repeatedly transmits a fixed sequence of time slots over a single transmission channel. Within T-Carrier systems, such as T-1 and T-3, TDM combines Pulse Code Modulated (PCM) streams created for each conversation or data stream.

Wavelength Division Multiplexing (WDM)

WDM system is a technology which multiplexes a number of optical carrier signals onto a single optical fibre by using different wavelengths (i.e. colours) of laser light. This technique enables bidirectional communications over one strand of fibre, as well as multiplication of capacity.

In early WDM systems, there were two IR channels per fibre. At the destination, the IR channels were demultiplexed by a dichroic (two-wavelength) filter with a cutoff wavelength approximately midway between the wavelengths of the two channels. It soon became clear that more than two multiplexed IR channels could be demultiplexed using cascaded dichroic filters, giving rise to coarse wavelength-division multiplexing (CWDM Multiplexer) and dense wavelength-division multiplexing (DWDM).

1. WDM is the analog multiplexing technique. WDM is conceptually similar to FDM, in the sense that it combines different signals of different frequencies into single composite signal and transmit it on a single link.

2. In WDM the different signals are optical or light signals that are transmitted through optical fibre. Wavelength of a wave is reciprocal of its frequency. Therefore, if wavelength goes up, the frequency goes down and Vice-versa.

3. Thus in WDM, various light waves from different sources are combined to form a composite light signal that is transmitted across the channel to the receiver.

4. At the receiver side, this composite light signal is broken into different light waves by demultiplexer.

5. This combining and the splitting of light waves is done by using a prism.

6. One prism is used at the sender side to perform multiplexing and another prism is used at receiver side that performs demultiplexing as shown in fig.

7. The basic principle behind the usage of prisms is that, the prism bends a beam of light based on the angle of incidence and the frequency of light wave.


Applications of WDM

WDM is used in SONET (Synchronous Optical Network). It makes use of multiple optical fibre lines which are multiplexed & demultiplexed.

Dense Wavelength Division Multiplexer (DWDM)

Dense Wavelength Division Multiplexing (DWDM) is a technology that puts data from different sources together on an optical fibre, with each signal carried at the same time on its own separate light wavelength.

DWDM multiplexer works by combining and transmitting multiple signals simultaneously at different wavelengths on the same fibre. In effect, one fibre is transformed into multiple virtual fibres. So, if you were to multiplex eight OC -48 signals into one fibre, you would increase the carrying capacity of that fibre from 2.5 Gb/s to 20 Gb/s. Currently, because of DWDM, single fibres have been able to transmit data at speeds up to 400Gb/s.

A key advantage to DWDM is that it’s protocol- and bit-rate-independent. DWDM-based networks can transmit data in IP, ATM, SONET /SDH, and Ethernet, and handle bit rates between 100 Mb/s and 2.5 Gb/s. Therefore, DWDM-based networks can carry different types of traffic at different speeds over an optical channel.

Frequency Division Multiplexing (FDM)

Frequency-division multiplexing (FDM) is a scheme in which numerous signals are combined for transmission on a single communications line or channel. Each signal is assigned a different frequency (subchannel) within the main channel.

Statistical Multiplexer

Statistical multiplexers make it possible for multiple RS-232 devices to share a single data line. They also perform error correction to insure error-free transmissions. The term “statistical” refers to their ability to take advantage of the intermittent usage statics of most RS-232 devices (and all PC and terminal users). Because keyboards are idle a large part of each second with no one typing and no data being sent from the computer, each PC or terminal often averages less than 5% of its potential data rate. Statistical multiplexers allow the sum of the PC and terminal rates to exceed the composite link speed between the multiplexers.

Multiplex Your Fiber By Using CWDM Or DWDM

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Using a WDM(Wavelength Division Multiplexing) for expanding the capacity of the fiber to carry multiple client interfaces is a highly advisable way as the physical fiber optic cabling is not cheap. As WDM widely used you must not unfamiliar with it, it is a technology that combines several streams of data/storage/video or voice protocols on the same physical fiber-optic cable, by using several wavelengths (frequencies) of light with each frequency carrying a different type of data.

Two types of WDM architecture available: Coarse Wavelength Division Multiplexing (CWDM) and Dense Wavelength Division Multiplexing (DWDM). CWDM/DWDM multiplexer and demultiplexerand OADM (Optical Add-Drop Multiplexer) are common fit in with Passive. With the use of optical amplifiers and the development of the OTN (Optical Transport Network) layer equipped with FEC (Forward Error Correction), the distance of the fiber optical communication can reach thousands of Kilometers without the need for regeneration sites.

CWDM
CWDM, each CWDM wavelength typically supports up to 2.5Gbps and can be expanded to 10Gbps support. The CWDM is limited to 16 wavelengths and is typically deployed at networks up to 80Km since optical amplifiers cannot be used due to the large spacing between channels. CWDM uses a wide spectrum and accommodates eight channels. This wide spacing of channels allows for the use of moderately priced optics, but limits capacity. CWDM is typically used for lower-cost, lower-capacity, shorter-distance applications where cost is the paramount decision criteria.

The CWDM Mux/Demux (or CWDM multiplexer/demultiplexer) is often a flexible plug-and-play network solution, which helps insurers and enterprise companies to affordably implement denote point or ring based WDM optical networks. CWDM Mux/demux is perfectly created for transport PDH, SDH / SONET, ETHERNET services over WDM, CWDM and DWDM in optical metro edge and access networks. CWDM Multiplexer Modules can be found in 4, 8 and 16 channel configurations. These modules passively multiplex the optical signal outputs from 4 too much electronic products, send on them someone optical fiber and after that de-multiplex the signals into separate, distinct signals for input into gadgets across the opposite end for your fiber optic link.

Typically CWDM solutions provide 8 wavelengths capability enabling the transport of 8 client interfaces over the same fiber. However, the relatively large separation between the CWDM wavelengths allows expansion of the CWDM network with an additional 44 wavelengths with 100GHz spacing utilizing DWDM technology, thus expanding the existing infrastructure capability and utilizing the same equipment as part of the integrated solution.

DWDM
DWDM is a technology allowing high throughput capacity over longer distances commonly ranging between 44-88 channels/wavelengths and transferring data rates from 100Mbps up to 100Gbps per wavelength.

DWDM systems pack 16 or more channels into a narrow spectrum window very near the 1550nm local attenuation minimum. Decreasing channel spacing requires the use of more precise and costly optics, but allows for significantly more scalability. Typical DWDM systems provide 1-44 channels of capacity, with some new systems, offering up to 80-160 channels. DWDM is typically used where high capacity is needed over a limited fiber resource or where it is cost prohibitive to deploy more fiber.

The DWDM multiplexer/demultiplexer Modules are made to multiplex multiple DWDM channels into one or two fibers. Based on type CWDM Mux/Demux unit, with optional expansion, can transmit and receive as much as 4, 8, 16 or 32 connections of various standards, data rates or protocols over one single fiber optic link without disturbing one another.

Ultimately, the choice to use CWDM or DWDM is a difficult decision, first we should understand the difference between them clearly.

CWDM vs DWDM
CWDM scales to 18 distinct channels. While, DWDM scales up to 80 channels (or more), allows vastly more expansion. The main advantage of CWDM is the cost of the optics which is typically 1/3rd of the cost of the equivalent DWDM optic. CWDM products are popular in less precision optics and lower cost, less power consumption, un-cooled lasers with lower maintenance requirements. This difference in economic scale, the limited budget that many customers face, and typical initial requirements not to exceed 8 wavelengths, means that CWDM is a more popular entry point for many customers.

Buying CWDM or DWDM is driven by the number of wavelengths needed and the future growth projections. If you only need a handful of waves and use 1Gbps optics, CWDM is the way to go. If you need dozens of waves, 10Gbps speeds, DWDM is the only option.