Understanding WDM MUX/DEMUX Ports and Its Application

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

Wavelength division multiplexing (WDM) is a commonly used technology in optical communications. It combines multiple wavelengths to transmit signals on a single fiber. To realize this process, CWDM and DWDM mux/demux are the essential part. As we all know, there are several different ports on the WDM mux and demux. This article will give a clear explanation to these ports and their applications in WDM network.
Overview of Different Ports on WDM MUX/DEMUX
Line Port
Line port, sometimes also called as common port, is the one of the must-have ports on CWDM and DWDM Mux/Demux. The outside fibers are connected to the Mux/Demux unit through this port, and they are often marked as Tx and Rx. All the WDM channels are multiplexed and demultiplexed over this port.
Channel Port
Like the line port, channel ports are another must-have ports. They transmit and receive signals on specific WDM wavelengths. CWDM Mux/Demux supports up to 18 channels from 1270nm to 1610nm with a channel space of 20nm. While DWDM Mux/Demux uses wavelengths from 1470nm to 1625nm usually with channel space of 0.8nm (100GHz) or 0.4nm (50GHz). Services or circuits can be added in any order to the Mux/Demux unit.
40ch dwdm mux demux
Monitor Port
Monitor port on CWDM and DWDM Mux/Demux offers a way to test the dB level of the signal without service interruption, which enable users the ability to monitor and troubleshoot networks. If the Mux/Demux is a sing-fiber unit, the monitor port also should be a simplex one, and vice verse.
Expansion Port
Expansion port on WDM Mux/Demux is used to add or expand more wavelengths or channels to the network. By using this port, network managers can increase the network capacity easily by connecting the expansion port with the line port of another Mux/Demux supporting different wavelengths. However, not every WDM Mux/Demux has an expansion port.
dwdm mux demux
1310nm and 1550nm Port
1310nm and 1550nm are one of WDM wavelengths. Many optical transceivers, especially the CWDM and DWDM SFP/SFP+ transceiver, support long runs transmission over these two wavelengths. By connecting with the same wavelength optical transceivers, these two ports can be used to add 1310nm or 1550nm wavelengths into existing WDM networks.
Application Cases of Different Ports on WDM MUX/DEMUX
Although there are several different ports on WDM Mux/Demux, not all of them are used at the same time. Here are some examples of these functioning ports in different connections.
Example One: Using 8 Channels CWDM Mux/Demux with Monitor Port
cwdm mux demux with monitor port
This example is a typical point-to-point network where two switches/routers are connected over CWDM wavelength 1511nm. The CWDM Mux/Demux used has a monitor port and 1310nm port, but the 1310nm does not put into use. In addition, an optical power meter is used to monitor the power on fibers connecting the site A and B.
Example Two: Achieve 500Gbps at Existing Fiber Network with 1310nm Port
dwdm mux with 1310nm port
In this example, two 40 channels DWDM Mux/Demux with monitor port and 1310nm port are used to achieve total 500Gbps services. How to achieve this? First, plug a 1310nm 40G or 100G fiber optical transceiver into the terminal equipment, then use the patch cable to connect it to the existing DWDM network via the 1310nm port on the DWDM Mux/Demux. Since the 1310nm port is combined into a 40 channels DWDM Mux, then this set-up allows the transport of up to 40x10Gbps plus 100Gbpx over one fiber pair, which is total 500Gbps. If use 1550nm port, then the transceiver should be available on the wavelength of 1550nm.
cwdm mux with expansion port
The connection in this example is similar to the last one. The difference is that this connection is achieved with expansion port not 1310nm port. On the left side in the cases, a 8 channels CWDM Mux/Demux and a 4 channels CWDM Mux/Demux are stacked via the expansion port on the latter Mux/Demux. And the two 4 channels CWDM Mux/Demux are combined with the line port. If there is a need, more Mux/Demux modules can be added to increase the wavelengths and expand network capacity.

Different Ports on WDM Mux/Demux

In the WDM (wavelength-division multiplexing) system, CWDM (coarse wavelength-division multiplexing) and DWDM (dense wavelength-division multiplexing) Mux/Demux (multiplexer/demultiplexer) modules are often deployed to join multiple wavelengths onto a single fiber. Multiplexer is for combining signals together, while demultiplexer is for splitting signals apart. On a WDM Mux/Demux, there are many kinds of ports for different applications. This article will discuss the functions of these ports on WDM Mux/Demux.
Necessary Ports on WDM Mux/Demux
Channel port and line port are the necessary ports to support the basic function of WDM Mux/Demux to join or split signals in the data network.
Channel Port
A WDM Mux/Demux usually has several channel ports on different wavelengths. Each channel port works for a specific wavelength. Since there are 18 wavelengths of CWDM ranging from 1270 nm to 1610 nm with a 20nm interval, the number of channel ports on CWDM Mux/Demux also ranges from 2 to 18. DWDM has a more dense wavelength spacing of 0.8 nm (100 GHz) or 0.4 nm (50 GHz) ranging from S-Band to L-Band around 1490 nm to 1610 nm. The number of DWDM Mux/Demux channel ports is about 4 to 96 for high-density networks.
Line Port
Each WDM Mux/Demux will have a line port connecting to the network backbone. Combined channels are transmitted or received at the line port. In addition, line port can be divided into dual-fiber and single-fiber types. Dual-fiber line port is used for bidirectional transmission, therefore the transmit and receive port in each duplex channel must support the same wavelength. However, single-fiber line port only supports one direction data flow, thus the transmit and receive port of duplex channel will support different wavelengths. The wavelengths’ order of single-fiber WDM MUX/DEMUX should be reversed at both sides of the network.
Special Ports on WDM Mux/Demux
Apart from the necessary ports, some special ports can also be found on WDM Mux/Demux for particular needs.
1310nm Port and 1550nm Port
1310nm and 1550nm ports are certain wavelength ports. Since a lot of optical transceivers use these two wavelengths for long-haul network, adding these two ports when the device does not include these wavelengths is very important. CWDM Mux/Demux can add either type of wavelength ports, but the wavelengths which are 0 to 40 nm higher or lower than 1310 nm or 1550 nm cannot be added to the device. However, DWDM Mux/Demux can only add 1310nm port.
Expansion Port
Expansion port can be added on both CWDM and DWDM Mux/Demux modules. This is a special port to increase the number of available channels carried in the network. That is to say, when a WDM Mux/Demux can not meet all the wavelength needs, it is necessary to use the expansion port to add different wavelengths by connecting to another WDM Mux/Demux’s line port.
Monitor Port
Monitor port is used for signal monitoring or testing. Network administrators will connect this port to the measurement or monitoring equipment to inspect whether the signal is running normally without interrupting the existing network.
From this post, we can know that a WDM Mux/Demux has multiple types of ports. Channel and line ports are integral ports for normal operation of the WDM Mux/Demux. 1310nm port, 1510nm port, expansion port and monitor port are used for special requests of the WDM application. Hence, you should have a thorough consideration of your project before choosing the WDM Mux/Demux module.

What Is WDM?

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

WDM is a technique in fiber optic transmission that enables the use of multiple light wavelengths (or colors) to send data over the same medium. Two or more colors of light can travel on one fiber and several signals can be transmitted in an optical waveguide at differing wavelengths.
Early fiber optic transmission systems put information onto strands of glass through simple pulses of light. A light was flashed on and off to represent digital ones and zeros. The actual light could be of almost any wavelength—from roughly 670 nanometers to 1550 nanometers.
WDM is a technique in fiber optic transmission for using multiple light wavelengths to send data over the same medium.
During the 1980s, fiber optic data communications modems used low-cost LEDs to put near-infrared pulses onto low-cost fiber. As the need for information increased, so did the need for bandwidth. Early SONET systems used 1310 nanometer lasers to deliver 155 Mb/s data streams over very long distances.
But this capacity was quickly exhausted. Advances in optoelectronic components allowed the design of systems that simultaneously transmitted multiple wavelengths of light over a single fiber. Multiple high-bit rate data streams of 2.5 Gb/s, 10 Gb/s and, more recently, 40 Gb/s, 100 Gb/s, and 200 Gb/s could be multiplexed through divisions of several wavelengths. Thus, WDM was born.
There are two types of WDM today:
Coarse WDM (CWDM): WDM systems with fewer than eight active wavelengths per fiber. CWDM is defined by wavelengths. DWDM (see below) is defined in terms of frequencies. DWDM’s tighter wavelength spacing fits more channels onto a single fiber, but cost more to implement and operate.
CWDM is for short-range communications, so it employs wide-range frequencies with wavelengths spread far apart. Standardized channel spacing permits room for wavelength drift as lasers heat up and cool down during operation. CWDM is a compact and cost-effective option when spectral efficiency is not an important requirement.
Dense WDM (DWDM): DWDM is for systems with more than eight active wavelengths per fiber. DWDM dices spectrum finely, fitting 40-plus channels into the same frequency range used for two CWDM channels.
DWDM is designed for long-haul transmission, with wavelengths packed tightly together. Vendors have found various techniques for cramming 40, 88, 96, or 120 wavelengths of fixed spacing into a fiber. When boosted by Erbium Doped-Fiber Amplifiers (EDFAs)—a performance enhancer for high-speed communications—these systems can work over thousands of kilometers. For robust operation of a system with densely packed channels, high-precision filters are required to peel away a specific wavelength without interfering with neighboring wavelengths. DWDM systems must also use precision lasers that operate at a constant temperature to keep channels on target.
Ciena’s 6500 Packet-Optical Platform converges packet, Optical Transport Networks (OTNs), and flexible WaveLogic Photonics in a single platform to streamline operations and optimize footprint, power, and capacity. Built for efficient network scaling from the access to the backbone core, it offers the full gamut of CWDM and DWDM solutions, with DWDM solutions ranging from 10 Gb/s to beyond 200 Gb/s.
The 6500 has the following advantages:
Industry-leading 10G, 40G, 100G, and 200G coherent and control plane capabilities for scale and service differentiation
Hybrid OTN and packet-switching technologies for the most efficient use of network resources
Embedded and discrete software tools that increase programmability, visibility, and control of the optical network
Minimal equipment needed to adapt to a wide variety of requirements, reducing standardization and operational costs
The ability to tailor customer solutions via various chassis, power, and configuration options to maximize operational efficiencies

How to Use OADM in WDM Network ?

OADM is a cost-effective and easy to use passive fiber optic component, which can provide easy to build and grow connectivity environment for WDM network.

OADM is a cost-effective and easy to use passive fiber optic component, which can provide easy to build and grow connectivity environment for WDM network.Optical add-drop multiplexer is one of the key devices to implement such optical signal processing. Use of OADM makes it possible to freely add or drop signals with arbitrary wavelengths over multiplexed optical signals by assigning a wavelength to each destination.this article ,Let us introduce how to use OADM in WDM Network?

Inside an OADM

A traditional OADM consists of three parts: an optical demultiplexer, an optical multiplexer and between them a method of reconfiguring the paths between the optical demultiplexer, the optical multiplexer and a set of ports for adding and dropping signals. The multiplexer is used to couple two or more wavelengths into the same fiber. Then the reconfiguration can be achieved by a fiber patch panel or by optical switches which direct the wavelengths to the optical multiplexer or to drop ports. The demultiplexer undoes what the multiplexer has done. It separates a multiplicity of wavelengths in a fiber and directs them to many fibers.


Main Function and Principle of OADM

For an OADM, “Add” refers to the capability of the device to add one or more new wavelength channels to an existing multi-wavelength WDM signal while “drop” refers to drop or remove one or more channels, passing those signals to another network path. The OADM selectively removes (drops) a wavelength from a multiplicity of wavelengths in a fiber, and thus from traffic on the particular channel. It then adds in the same direction of data flow the same wavelength, but with different data content. The main function of OADM function is shown in the following picture. This function is especially used in WDM ring systems as well as in long-haul with drop-add features.

How to Connect OADM With WDM MUX/DEMUX

In most cases, OADM is deployed with CWDM or DWDM MUX/DEMUX. It is usually installed in a fiber optic link between two WDM MUX/DEMUXs. The following picture shows a CWDM network using a 1-channel dual fiber OADM between two CWDM MUX/DEMUXs. Signals over 1470 nm are required to be added to and dropped from the dual fiber link. On the OADM, there are usually one port for input and one port for output. The OADM can be regarded as a length of fiber cable in the fiber link. The point is the one or more strand of signals is added or dropped when the light goes through the OADM.



OADM is still evolving, and although these components are relatively small, they are immeasurable in the future.Optical Add-Drop Multiplexer (OADM) is used for multiplexing and routing different channels of fiber into or out of a single fiber. The CWDM OADM is designed to optically add/drop one or multiple CWDM channels into one or two fibers. Fiber-Mart provides a series of OADM modules which can be Customized. For more information, welcome to visit www.fiber-mart.com or contact me by e-mail: service@fiber-mart.com

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