Category Archives: WDM Optical Network

Optical Facility Protection for WDM Network

Wavelength-division multiplexing (WDM) is nothing new to us. It is a technology that multiplexes multiple optical signal on a single optical fiber by using different wavelengths of laser light. The multiple transmission paths involved in WDM network effectively relieve fiber exhaustion and extend link capacity, but they also make facility protection more essential than ever, because solid facility protection is the key to the availability of the link and the data being transmitted. This article introduces two methodologies that proven to be valid for optical link protection: electrical switching and optical switching.

Why Facility Protection is Essential to WDM Network?

With the explosion of information, the demand for extremely high-capacity data transmission began to soar. Enterprises and companies were asked to deliver greater volumes of traffic at much higher rates. Which spurs the need to store data in different facilities and to transport these data over different paths, so that if any network failure or downtime occurs, they can soon recover and keep the business running. In a properly protected WDM network, customers will have two or more sites that are connected to each other by diver paths, ensuring the availability and reliability of the network all the time. But fiber may break for many reasons including damage from the physical environment and human faults. Thus facility protection becomes vitally important.

Effective Facility Protection Methods for WDM Network

There are basically two methods for optical facility protection: one is electrical switching which adopts a cross connect to duplicate and select the working or protecting path, with two independent optics involved per each path and two Mux/Demux. And the other is optical switching, unlike electrical switching, it typically uses an optical switch to select the working or protected path.

Electrical Switching

In electrical switching, each service is simultaneously transmitted and received from two dark fibers. The signal from the device on the left side is transmitted to both working and protecting fiber, then it is delivered to the end device on the right side.

facility protection with electrical switching

So how the cross connect duplicates the Tx signals and selects the working and protecting path (Rx) for the receiving signal? In fact, the Tx signal is sent through the cross connect and duplicated through both transponders. On the Rx direction, the cross connect switches the signal to the receiving optical power of the transponder.

electrical switching details

Optical Switching

An optical switch is involved in this method to duplicate the data to the working and protecting fiber with an optical splitter, and selecting the operating fiber according to the optical power signals of all the services. One of the distinct differences between optical switching and electrical switching is that it simply offers no protection for the WDM optic.

facility protection with optical switching

Electrical Switching vs. Optical Switching: How to Choose?

When applied for optical facility protection, both methods have their benefits and drawbacks. For electrical switching, the WDM optic is better protected since it uses two uplink transponders per service – one for working and the other for protecting. Since protection is delivered per service, once a single service needs to be switched, the other service won’t be disturbed. Moreover, electrical switching is suited for any network topologies, and no power budget loss is associated with this method. However, electrical switching generally adopted more WDM optics and an additional Mux/Demux, hence fewer services are available through each unit, and it inevitably increases total costs.

While for optical switching which does not offer protection for WDM optic, more ports are available to transport services on each unit. Besides, no additional Mux/Demux is required in this method, so the overall cost of the solution can be decreased. The drawbacks of this method are that the optical switch lowers the optical power budget of the link. And optical switching is not suited for ring topologies for the fact that add and drop functionality is not available per wavelength.

Conclusion

Optical facility protection impacts the link availability, performance and reliability to a large extent. Your choice on facility protection method should always base on your specific needs, and taking power budget, network topology and cost into consideration. I hope this article would be helpful for you to make an informed decision.

Dual-Fiber or Single-Fiber CWDM Mux Demux for Higher Capacity Need?

What would you do if your network capacity can not meet your requirement? Will you put more fibers or update your system? In fact, these two methods are not very recommendable. Why? As your fiber cabling infrastructure is limited for adding fibers and high cost is required for upgrading system, these two methods are unworkable or too expensive. Under this condition, using a pair of CWDM Mux Demux to build a CWDM system with higher capacity is highly recommended. The CWDM Mux Demux is regarded as a key component for a CWDM system, as shown below. It can be simply divided into two types, dual-fiber and single-fiber CWDM Mux Demux. To meet the higher capacity need of your system, this post will mainly introduce the basic knowledge of the dual-fiber and single-fiber CWDM Mux Demux and guide you find a suitable fiber optic Mux Demux for building your CWDM system.

CWDM system

Dual-Fiber CWDM Mux Demux

Dual-Fiber CWDM Mux Demux is a passive device multiplexing and demultiplexing the wavelengths for expanding network capacity, which must work in pairs for bidirectional transmission over dual fiber. It enables up to 18 channels for transmitting and receiving 18 kinds of signals, with the wavelengths from 1270 nm to 1610 nm. The CWDM transceiver inserted into the fiber optic Mux port should have the same wavelength as that of Mux port to finish the signal transmission. For instance, the two reliable 4 channel CWDM Mux Demux showed below use four wavelengths, 1510 nm, 1530 nm, 1550 nm and 1570 nm, their corresponding CWDM transceivers also features the same wavelengths.

Dual Fiber CWDM Mux Demux

When the connection above works, the left 4 channel dual-fiber CWDM Mux Demux uses 1510 nm, 1530 nm, 1550 nm and 1570 nm for transmitting 4 kinds of signals through the first fiber, while the right 4 channel dual-fiber CWDM Mux Demux features 1510 nm, 1530 nm, 1550 nm and 1570 nm for receiving the signals. On the other hand, the transmission from the right to left use the same wavelengths to carry another 4 signals through the second fiber, finally achieving the bidirectional signal transmission.

Single-Fiber CWDM Mux Demux

Single-fiber CWDM Mux Demux should be also used in pairs. One multiplexes the several signals, transmits them through a single fiber together, while another one at the opposite side of the fiber demultiplexes the integrated signals. Considering that the single-fiber CWDM Mux Demux transmitting and receiving the integrated signals through the same fiber, the wavelengths for RX and TX of the same port on the Single-fiber CWDM Mux Demux should be different. Hence, if the 4 channel single-fiber CWDM Mux Demux is used for CWDM system, 8 wavelengths are required, the twice time as that of the dual-fiber one.

Single Fiber CWDM Mux Demux

The working principle of single-fiber CWDM Mux Demux is more complicated, compared to the dual-fiber one. As shown in the figure above, the transmission from the left to right uses 1470 nm, 1510 nm, 1550 nm and 1590 nm to multiplex the signals, transmit them through the single fiber, and using the same four wavelengths to demultiplex the signals, while the opposite transmission carries signals with 1490 nm, 1530 nm, 1570 nm and 1610 nm over the same fiber. As for the wavelength of the transceiver, it should use the same wavelength as TX of the port on the CWDM Mux Demux. For example, when the port of a single-fiber CWDM Mux Demux has 1470 nm for TX and 1490 nm for RX, then a 1470nm CWDM transceiver should be inserted.

Dual-Fiber vs. Single-Fiber CWDM Mux Demux

We always consider whether an item is worth buying according to its performance and cost. In view of the performance, the single-fiber CWDM Mux Demux can carry signals through only one fiber supporting fast speed transmission and saving the fiber resource, while the dual-fiber one requires two fibers for transmission with a higher reliability. Besides, using single-fiber CWDM Mux Demux can be easier to install. In view of the cost, the single-fiber CWDM Mux Demux is much more expensive than the dual-fiber. And the simplex fiber cable also costs higher than duplex fiber cable. Thereby, the whole cost for building single-fiber CWDM system must be much more higher. Like the two sides of the same coin, both the dual-fiber and single-fiber CWDM Mux Demux have their own advantages and disadvantages. Which one you should choose just depends on your system needs and your budget for building the CWDM system.

Embedded CWDM Solution for Fiber Channel SAN Extension

CWDM, as an established optical transport technology, is universally employed in optical network for transmission distance extension and fiber exhaust reduction. This technology has evolved for years and now is available for Fiber Channel applications with the rate up to 4.25Gb/s. Moreover, when compared with traditional transmission approach via multiple fibers, embedded CWDM technology also makes economic sense while used in 4G Fiber Channels, and that’s what we are going to address in this article.

Fiber Channel Overview

The 4G Fiber Channel effectively improves storage area networks (SANs) performance by doubling speed and offering backward compatibility with 2G and 1G systems. With the proliferation of bandwidth-extensive applications, fiber capacity is on the edge of exhaustion. However, the demand for extremely high-capacity data transmissions began to soar. In this case, it is critical for IT technicians to enhance Fiber Channel SAN capacity without increasing costs.

Economical Fiber Channel Solution: Embedded CWDM Technology

CWDM technology expands fiber capacity by multiplexing optical light signals of different wavelength on a single optical fiber. In a CWDM network, components like CWDM Mux/Demux and CWDM transceivers are indispensable. With CWDM, IP data (Gigabit Ethernet or 10G Ethernet) and storage data (4G/2G/1G Fiber Channel) can be transported over a single fiber infrastructure, eliminating the need for complex protocol conversion.

Until now, standalone CWDM solutions are the commonly used methods to transport LAN connections and SAN connections simultaneously between main and recovery sites. Despite that it generates high equipment cost and reduces system reliability. In this case, embedded CWDM emerges as an ideal alternative for use in Fiber Channel applications. Embedded CWDM integrates CWDM optics (like CWDM SFP transceivers) directly into the Fiber Channel switch or Ethernet router, offering better reliability and simplicity. Thus instead of laying more fibers and equipment, users can extend system capacity only by adding new CWDM SFPs, which greatly reduces human labor and overall expenditure.

embedded CWDM solution with CWDM SFPs

Embedded CWDM for Distance Extension in 4G Fiber Channel

While used for SAN distance extension, CWDM functions to reduce the amount of required WAN fibers. Here we take the example of a SAN extension between a primary site and secondary site. With solution A, the implementation requires several WAN fibers to get the capacity required.

multiple fiber in SAN

As for solution B, CWDM is adopted to multiplex several signals onto a single fiber pair. CWDM SFPs are directly plugged into the ports from the Fiber Channel switch to generate signals of specific CWDM wavelength. The CWDM Mux combines wavelengths onto a fiber pair, while the CWDM Demux splits these wavelengths into several fiber on the receiver site. Thus the number of required WAN fibers is reduced by the number of wavelengths used.

embedded CWDM in SAN extension

Benefits of Embedded CWDM Solution

Embedded CWDM system is easier to operate, which requires no additional network management or training. It introduces more reliability, flexibility and simplicity due to fewer components involved in the system. And its advantages become more evident when it comes to cost: Embedded CWDM solution simply offers lower investment expenditure and operation cost, since it removes the need for adding new fibers and equipment, which can be cost-prohibitive. Even that CWDM SFPs and CWDM Mux/Demux should be involved in CWDM system, the overall cost is just a fraction of multiple fiber transmission.

Conclusion

CWDM solution allows IT managers to achieve network capacity expansion in a more cost-effective, simplified and flexible way. Besides, it also provides enhanced performance and reliability for current need and future growth. For more CWDM solutions and information, visit www.fs.com or contact us via sales@fs.com.

How to Realize 16 Channels Transmission in DWDM Network?

DWDM MUX/DEMUX plays a critical in WDM network building. 16 channels transmission is very common in DWDM networks. How to realize it in a simple way? This article intends to introduce two solutions to achieve 16 channels with different types of components. Which one is more cost-effective and competitive? The comparison between the them also will be explored. Hope it will help you when choosing fiber mux for your DWDM networks.

wdm network

Solutions to Achieve 16 Channels Transmission in DWDM Network

In order to illustrate the solution more clearly, I take two types of DWDM MUX/DEMUX as an example. One is the traditional 16 channels dual fiber DWDM MUX/DEMUX. Another is two FMU 8 channels dual fiber DWDM MUX/DEMUX. The latter has an expansion port.

Solution One: Using Traditional 16 Channels DWDM MUX/DEMUX

The 16 channel DWDM MUX/DEMUX is a passive optical multiplexer designed for metro access applications. It’s built fiber mux and demux in one unit and can multiplex 16 channels on a fiber pair. In addition, this type of fiber mux also can be added some functional ports like expansion port, monitor port and 1310nm port, which make it possible to increase network capacity easily. The following is a simple graph showing the 16 channels transmission with this traditional DWDM MUX/DEMUX.

16 channels dwdm mux demux

Solution Two: Using Two FMU 8 Channels DWDM MUX/DEMUX Modules

The FMU 8 channels DWDM MUX/DEMUX provide 8 bidirectional channels on a dual strand of fiber. Usually they are used together. Unlike the 16 channels DWDM MUX/DEMUX, this FMU 8 channels one has a more compact size, for it only occupies half space in a 1U rack. Put two FMU 8 channels DWDM MUX/DEMUX modules into one 1U two-slot rack mount chassis. two 8 channels DWDM MUX/DEMUX with different wavelengths are connected through the expansion port to realize 16 channels transmission in a DWDM network. Here is a graph showing how to achieve 16 channels DWDM transmission with these two 8m channels fiber muxes. As shown in the figure, two 8 channels DWDM MUX/DEMUX with different wavelengths are connected through the expansion port to realize 16 channels transmission in a DWDM network.

8 channels

16CH DWDM MUX and Two FMU 8CH DWDM MUX: What’s the Difference When Deployed?

From the content above, we can see both solutions can realize the 16 channels transmission in a DWDM network. Then, are there differences between them? Or which is more competitive? Here is a simple analysis of the two solutions.

fiber mux

Firstly, comparing the two graphs above, the FMU 8 channels DWDM MUX/DEMUX are connected together by an expansion port, that’s why it can deliver 16 channels services like the traditional one. Except for connecting 8 channels DWDM MUX/DEMUX, the FMU fiber mux with expansion port also can be combined with other channels fiber mux like 2 channels, 4 channels or other channels, which offer more flexibility for optical network deployment and upgrade. And you can add DWDM into CWDM networks at some specific wavelengths with FS.COM FMU fiber mux.

Secondly, DWDM MUX/DEMUX price is always an important point that many network operators pay attention to. Therefore, when buying a fiber mux, the cost is a critical point to consider. If you search on Google, you will find the lowest price is $1100 in FS.COM. And the cost of using two 8 channels MUX/DEMUX is the same as the deployment of one 16 channels MUX/DEMUX. However, compared with the 16 channels DWDM MUX/DEMUX, the FMU 8 channels fiber mux provides a competitive solution for small networks which needn’t to buy a full-channel fiber mux that supports all 16 channels or more channels.

Conclusion

From the comparison above, the FMU 8 channels DWDM MUX/DEMUX is more flexible and cost-effective when deployed in WDM networks. How to choose is based on the requirements of your networks. FS.COM supplies two different types of these WDM MUX/DEMUX. Here is a simple datasheet of them. If you have more requirements for additional wavelengths, welcome to visit www.fs.com for more detailed information.

Application
ID
Description
16 channels
16 ch. DWDM Mux Demux, C27-C42, , IL <4.6dB, duplex LC/UPC
8 channels
8 ch. Dual Fiber DWDM Mux Demux, C53-C60, with expansion port, IL <4.6dB, LC/UPC

Factors to Consider Before DWDM Network Design

DWDM network deployment usually requires a lot of preparation. There are many factors to be considered before DWDM network design. Even a professional team would take a long time to calculate the parameters over and over to ensure good network performance, let alone some customers who are not experienced. In many cases, customers just have a rough concept of what they need for a DWDM network. When it comes to specific parameters of products, they get no idea. This post offers the most important factors to be considered before DWDM networking. No matter you want to deploy a DWDM network all by your own team, or you want to customize one by other vendors. You will find this post helpful.

DWDM Network Design

What Kind of DWDM Network You Want to Build?

This question contains many details. Here offer several basic factors:

Simplex or Duplex: it is known that DWDM network multiplex different wavelengths together to transmit different ways of optical signals over optical fiber. These wavelengths can be transmitted over the same optical fiber or a pair of optical fibers. Duplex DWDM uses the same for both transmitting and receiving for a way of duplex optical signal over duplex optical fiber. However, the simplex DWDM network uses two different wavelengths for a way of duplex optical signal over a length of single fiber. Thus, the simplex DWDM network provides lower capacity than duplex DWDM network.

Distance: DWDM network gets the greatest returns on investment. It is usually deployed for long distance transmission. But long distance means large light loss. Distance of DWDM network and devices or points it passes should also be considered.

Data Rate and Space Channel: a DWDM network can transmit optical signals of different data rates at the same time. Currently, DWDM network generally transmits 1G and 10G for each wavelength. 1G DWDM SFP, 10G DWDM SFP+ and 10G DWDM XFP modules are usually used. Space Channel of 50 GHz Grid and 100 GHz Grid is commonly applied.

Is There Any Wavelength Adding and Dropping?

The DWDM network needs DWDM MUX/DEMUX for wavelengths multiplexing and de-multiplexing. It is common that a DWDM network passing many places. And wavelengths are required to be added and dropped at some of these places. In this case, DWDM OADM should be used.

DWDM MUX insertion loss test

How to Calculate Light Loss of DWDM Network?

There is light loss in every DWDM network. Technicians should calculate the light loss to decide what devices to be added in the network to ensure good transmission quality. Light loss occurs at many place, the optical fiber for transmission, the DWDM MUX/DEMUX, the devices connected in the network and even the fiber optic splicers and connection points have light loss.

How to Ensure Good DWDM Network Transmission Quality?

There are a variety of factors that can affect the transmission quality. The light source, light loss, transmission distance, fault risks, etc. However, there are always methods to overcome problems. EDFA can be added in the network to ensure enough optical power. If optical power is too strong, fiber optic attenuator can be used. OEO offers conversion between grey wavelengths and DWDM wavelengths. DCM and OLP are separately used for light dispersion compensation and backup line building. These devices can be used properly for good transmission quality.

DWDM MUX

How to Satisfy the Requirements for Both Now and Future?

A DWDM network might only need to transmit several ways of optical signals. However, it might be required to transmission tens of ways optical signals. During the deployment, technician should considerate about the future application. If there is no limit in budget, it would be better to deploy DWDM MUX with more channel port. If not, you can try FS.COM FMU half-U plug-in DWDM MUX modules. You can buy one module for current use and expand the DWDM MUX with another module in the future easily via expansion port on the MUX. All the wavelengths on the DWDM MUX can be customized according to your application.

DWDM long haul

How to Get the Better Performance With Lowest Cost for DWDM Network?

To get the better performance with lowest cost for DWDM network, you need carefully calculate the wavelength, light loss, devices and so on. In practical application, the DWDM network could be really complex, many devices like EDFA, OEO and DCM might be added in the network. It costs a lot for the deployment and management of these devices. Now FS.COM has made these devices into small plug-in cards and offers 1/2/4U chassis to hold them. A free software is also provided for better management and monitoring. This is FS.COM new series of product for DWDM long haul transmission—FMT multi-service transmission platform, which is a cost-effect and high performance system for DWDM network.

Professional Team for DWDM Network Design and Customization

The above mentioned factors are just the basic information that you should consider before DWDM network design. For more professional service and tech support, you can visit FS.COM where you can find professional DWDM network design and customized one-stop solution team and services.