Category Archives: CWDM network

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 Mux Demux for Connecting Cisco Nexus 9396PX and FS S5850-3252Q

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.

Why Not Use Raman Amplifier to Extend the CWDM Network Reach?

In comparison with the long-haul DWDM network that uses the thermo-electric coolers to stabilize the laser emissions essential, the CWDM network is a more economical solution that features wider wavelength spacing, allowing the wavelength fluctuation of uncooled directly modulated laser diodes (DMLs). But on the other hand, the CWDM network exists the limitation for the uncooled DMLs’ output power and the additional loss of CWDM Mux Demux and optical add/drop modules. These make the CWDM loss budget limited to < 30 dB and the CWDM reach within 80 km. Moreover, when the insertion loss of the dark fiber is higher than our expectation, a decreasing transmission distance may occur. Hence, here offers the Raman amplifier (see the following figure) to extend the CWDM network reach, as an ideal solution.

Raman Amplifier

What’s Raman Amplifier?

Raman amplifier, also referred to as RA, is a kind of optical fiber amplifier based on Raman gain, which is used for boosting optical signals and finally achieving a longer transmission distance. Different from the erbium-doped fiber amplifier (EDFA) and semiconductor optical amplifier (SOA), the RA intensifies the signals through the nonlinear interaction between the signal and a pump laser within an optical fiber, as shown in the figure below.

Raman amplifier working principle

At present, two kinds of Raman amplifiers are available on the market, the distributed and lumped Raman amplifiers. As for the distributed Raman amplifier (DRA), it uses the optical fiber as the gain medium to multiplex the pump wavelength with signal wavelength, so that the optical signals can be boosted. With regard to the lumped one (LRA), it requires a shorter length of optical fiber for the signal amplification. Both of these two Raman amplifiers are suitable for amplifying CWDM signals and extending the CWDM network reach.

Why Raman Amplifier Is Used for Amplifying CWDM Signals?

As we know, the EDFA and SOA are able to strengthen the CWDM signals. But why it is not recommendable for the CWDM network? In fact, they can not perform as well as the RA in the CWDM network for some limitations, which can be learned from the following figure.

Optical Fiber Amplifier Comparison

The figures above shows various gain bandwidths of these three optical fiber amplifiers for CWDM network, but only the gain bandwidth the RA offers meet the CWDM network demands. To fully serve the CWDM network, the RA usually optimizes the pumping lightwave spectrum to extend the usable optical bandwidth. As for the EDFA, its gain bandwidth can not match well with the channel spacing of the CWDM network requirements. And for the SOA, although it offers the gain bandwidth fit enough for the CWDM network, it is still not suggested for the inherent technical limitations. In details, the SOA has a relatively low saturation power but a high noise figure and polarization sensitivity, compared to other two amplifiers. Hence, the RA is undoubtedly the best choice to strengthen the CWDM signals and lengthen the CWDM network reach.

How Does Raman Amplifier Benefit CWDM Network?

In order to study the benefit of RA for the CWDM network, here offers two sets of research data about the receiver sensitivity, for a bit-error rate (BER) of 10-9 using a pseudo-random bit sequence (PRBS) with a 231-1 word length.

Raman Amplifier Benefits for CWDM Network

From the figure above, we can learn that the first set of data is resulted from the four channel CWDM network without use of the RA, while the second utilizes the RA. In order to check whether the Raman amplifier benefits the CWDM network, we can take the data of 100km CWDM transmission through singlemode fiber (SMF) as an example. The power penalty of the transmission with a RA are separately -34.4 dBm, -34.2 dBm, -33.2 dBm and -32.3 dBm. It is 0.3 dBm better than the power penalty of the transmission without a RA, at least. Except that, we can also learn that the CWDM network with a RA can transmit the signals through the SMF at lengths up to 150m without any repeater stations, while the network without the RA cannot.

Conclusion

The Raman amplifier is an ideal alternative to the repeater in CWDM network, for intensifying the CWDM signals and extending the CWDM network reach. By using the Raman amplifier, the loss budget of the CWDM network can be increased, which finally achieves a longer transmission. Meanwhile, from the view of cost, the RA and the repeater are almost the same, but the repeater stations should cost much more for constructing and maintaining. Moreover, using the RA in the CWDM network can also gain the loss compensation of OADM. Then, why not use Raman amplifier to extend your CWDM network reach?

How to Deploy a Single-Fiber CWDM Network?

Generally, CWDM network designed for expanding the network capacity can be basically divided into two types, dual-fiber and single-fiber CWDM network, according to the optical fiber transmission line. For the dual-fiber CWDM network, its working principle is easy to acquire, which uses the same wavelength for transmitting and receiving each pair of dual-way signals over the duplex fiber cable. However, for the single-fiber CWDM network, the working principle is highly complex that specially works with different wavelengths for transmitting and receiving each pair of dual-way signals over only one fiber. To better understand the single-fiber CWDM network, here will mainly illustrate how does a single-fiber CWDM network work and introduce the components and installation steps for fast deploying a single-fiber CWDM network.

Introduction of Single-Fiber CWDM Network

Single-fiber CWDM network is a kind of WDM network, designed for greatly expanding the network capacity by combining and transmitting several pairs of dual-way signals with different wavelengths over a single fiber, instead of putting more fibers for lager dual-way data transmission need. When the single-fiber CWDM network runs, there are two single-fiber CWDM Mux Demux using two different wavelengths for each pair of dual-way transmission. In details, if the single-fiber CWDM Mux Demux has four channels for dual-way data transmission, then eight different wavelengths divided into four pairs are required for the four channels, as shown in the figure below. To make a comparison, a 4 channel dual-fiber CWDM Mux Demux only needs four different wavelengths for the dual-way transmission.

 4 Channel CWDM Network

From the figure above, we can learn that a 4 channel CWDM network needs two reliable 4 channel CWDM Mux Demux connected by a single fiber and four pairs of CWDM transceivers with eight different wavelengths connected to the CWDM Mux Demux, achieving the dual-way transmission. Obviously, each port of the two CWDM Mux Demux for the same channel has the complete reversed TX and RX. Just taking the first channel as example, the first port of the CWDM Mux Demux on the left side uses 1470nm for TX and 1490nm for RX, while the first port on the right side uses 1490nm for TX and 1470nm for RX, reversely. Hence, each pair of dual-way signals with two different wavelengths will be smoothly transmitted and received. To better understand how does the single fiber CWDM network work, the following table also lists the four pairs of wavelengths for the TX and RX ports of the two CWDM Mux Demux, which are also totally reversed.

TX and RX for Single-Fiber CWDM Mux Demux

Basic Components for a Single-Fiber CWDM Network

When deploy the single-fiber CWDM network, we should prepare two single-fiber CWDM Mux Demux, two switches, a rack-mount chassis, several pairs of CWDM transceivers and singlemode simplex patch cables that are the basic and essential components for a single-fiber CWDM network. The two switches separately act as the Local unit and Remote unit for the CWDM network, while the CWDM Mux Demux is the main unit of the network that should be fixed and held on the rack-mount chassis and then connected to the switch. To finish the connection between the CWDM Mux Demux and switch, we should insert the CWDM transceivers into the ports of CWDM Mux Demux and use the singlemode simplex patch cables to connect CWDM transceivers with the switch.

Basic Components for a Single-Fiber CWDM Network

Steps for Single-Fiber CWDM Network Deployment

To fast deploy a single-fiber CWDM network, here offers the step by step installation procedure.

Step A: Install the rack-mount chassis in a standard 19-inch cabinet or rack.

Step B: Align the single-fiber CWDM Mux Demux with the chassis shelf, slightly push it to the shelf cavity. And tighten the captive screws once the CWDM Mux Demux is totally inserted.

Step C: Plug the CWDM transceivers into the switch. And also, connect these CWDM transceivers to the corresponding ports on CWDM Mux Demux according to the wavelengths of the TX and RX, with the use of singlemode simplex patch cable.

Step D: Utilize the singlemode simplex patch cable to connect the two CWDM Mux Demux and test the performance of the whole single-fiber CWDM network.

Installation Steps for Single-Fiber CWDM Network

Conclusion

Single-fiber CWDM network is a cost-effective and easy-to-deploy solution that can not only take full use of the available fiber bandwidth in your network but also greatly expand your network capacity. If you are hesitating over upgrading your system for bigger capacity, buy CWDM multi-channel Mux/Demux, CWDM transceivers and other basic components to deploy the single-fiber CWDM network would be a better choice for you.

Guide to CWDM MUX/DEMUX System Installation

CWDM (coarse wavelength division multiplexing) comes from the WDM system. It is designed to increase the capacity of a fiber optic network without adding additional fiber. The wavelengths of CWDM channels are spaced 20 nm apart which allows the use of low-cost, uncooled lasers. The wavelengths usually range from 1270 nm to 1610 nm.

Today, CWDM Mux/Demux (multiplexer/demultiplexer) module is an important device to increase the current fiber cable capacity by transmitting multiple wavelengths with up to 18 signal channels over a single fiber. When using a CWDM multiplexer at the beginning of the network, accordingly a CWDM demultiplexer should be used at the opposite end to separate the wavelengths and direct them into the correct receivers. This greatly reduces the number of fiber cables and other data links.

CWDM-Mux-and-Demux

Basic Components of CWDM MUX/DEMUX System

Several basic components constitute a CWDM Mux/Demux system. They are a local unit, a remote unit, a rack-mount chassis, CWDM Mux/Demux modules, CWDM SFP transceivers and single-mode patch cables. The local unit and remote unit are two different switches. The rack-mount chassis is needed to be installed for holding the CWDM Mux/Demux module. As for the connections, CWDM SFP transceivers are usually used between a CWDM Mux/Demux module and a switch, and single-mode patch cables are used to connect transceivers to the module.

Preparation Before Installation

Multiple single-mode patch cables are needed for CWDM Mux/Demux system connection. And the transceivers used in the system must support the wavelengths from 1270 nm to 1610 nm. Make sure the installation environment is in a dry and interior space. The module should have enough room to create airflow for easier heat distribution. Any inappropriate arrangement that obstructs the ventilation holes should also be avoided.

CWDM MUX/DEMUX System Installation

Step one, mount the system chassis on the rack. The CWDM rack-mount chassis can be mounted in a standard 19-inch cabinet or rack. Make sure that you install the rack-mount chassis in the same rack or an adjacent rack to your system so that you can connect all the cables between your CWDM Mux/Demux modules and the CWDM SFP transceivers.

mounting-system-chassis

Step two, install the CWDM Mux/Demux modules. You should first loose the captive screws on the blank of module panel and remove the panel. Then align the module with the slot of the chassis shelf and gently push the module into the slot. Finally, ensure that you line up the captive screws on the module with the screw holes on the shelf and tighten them up.

installing-CWDM-MuxDemux-modules

Step three, install CWDM SFP transceivers. Since each channel has a specific wavelength, transceivers must comply with the right wavelengths. Each wavelength must not appear more than once in the system. Device pairs must carry transceivers with the same wavelength.

CWDM-SFP-transceiver

Step four, install the CWDM Mux/Demux to the switch. After inserting the CWDM SFP transceiver into the switch, single-mode patch cables are used to connect the transceiver to the CWDM Mux/Demux module.

Step five, connect the CWDM MUX/DEMUX pairs. In a CWDM MUX/DEMUX system, multiplexer and demultiplexer must be installed in pairs. Two strands of single-mode patch cables are needed in the duplex Mux/Demux module, and one strand of single-mode patch cable is enough for the simplex Mux/Demux module.

When you finish all these steps, the installation of CWDM Mux/Demux system is successfully completed.

Conclusion

CWDM Mux/Demux system is definitely a good solution to high capacity data transmission. It is efficient for power, space and cost saving. And the installation procedure is easy to follow. All the components above are available in FS.COM. If you are interested, please come and visit our website for more information.

Effective CWDM & DWDM Mux/Demux Solutions for WDM System

Wavelength division multiplexing (WDM) system is designed for high capacity communications. It is now frequently used as a method to merge multiple optical signals with different wavelengths onto a single fiber. There are two divisions of WDM system: coarse wavelength division multiplexing (CWDM) and dense wavelength division multiplexing (DWDM). Using WDM can enhance the effectiveness of bandwidth in fiber optic communications. The WDM Mux/Demux has a number of communication channels, and matches with a certain frequency. Wavelengths are separated to different receivers at the destination. Mux/Demux module is an important assembly using WDM technology. This article will introduce some effective CWDM and DWDM Mux/Demux solutions for WDM system.

CWDM Mux/Demux & DWDM Mux/Demux
CWDM Mux/Demux

CWDM Mux/Demux is a flexible network solution for WDM optical networks. At most 18 full-duplex wavelengths can be added over a single fiber trunk which greatly alleviates fiber exhaustion. With low insertion loss and high stability, CWDM Mux/Demux is applied to many operations, such as CATV links, WDM systems, test and measurement, metro and access networks, FTTH networks, etc. The deployment of CWDM Mux/Demux is transparent and clear. Its compact form factor enables a much easier manipulation. Only coarse wavelengths can be transmitted over the fiber which reduces the WDM system cost.

Three kinds of CWDM Mux/Demux are widely used in the application. They are 1RU 19″ rack chassis CWDM Mux/Demux, half 19″/1RU CWDM Mux/Demux and splice/pigtailed CWDM Mux/Demux. CWDM Mux/Demux in 19 inch rack mount package is often used for CWDM, EPON and CATV network. Half 19″/1RU CWDM Mux/Demux is packed in LGX box using thing film coating and non-flux metal bonding micro optics packaging. Splice/pigtailed CWDM Mux/Demux is packed in the ABS box package based on standard thin film filter (TFF) technology.

DWDM Mux/Demux

DWDM Mux/Demux conveys optical signals in a more dense wavelength. It is especially used for long distance transmission where wavelengths are highly-packed together. The maximum delivered wavelengths can reach up to 48 channels in 100GHz grid (0.8nm) and 96 channels in 50GHz grid (0.4nm). DWDM Mux/Demux uses a reliable passive WDM technology that achieves low insertion loss. And it provides a solution for adding WDM technology to any existing network device. Applications like point-to-point DWDM fiber optimization, linear add/drop DWDM fiber optimization, external optical monitoring are typically using DWDM Mux/Demux module.

Likewise, 1RU 19″ rack chassis DWDM Mux/Demux, Half 19″/1RU DWDM Mux/Demux and splice/pigtailed DWDM Mux/Demux are three divisions of DWDM Mux/Demux modules. The first type is in 19 inch rack mount package used for long-haul transmission over C-band range of wavelengths. The second one is in LGX package used for PDH, SDH/SONET, Ethernet services transmission. The last one is in ABS box package and its pigtails are labeled with wavelengths.

Effective CWDM Mux/Demux & DWDM Mux/Demux Solutions

18-CH CWDM Mux/Demux is a highly recommended 1RU rack-mount CWDM Mux/Demux that combines 18 CWDM sources on a single fiber. The insertion loss is below 4.9 dB. Moreover, it has a monitor port that enables maintenance without ceasing the operation.

18ch-cwdm-mux-demux

40-CH DWDM Mux/Demux has 40 channels. As a DWDM Mux/Demux module with high density, low-loss and independent 1RU rack mount package, the best utilization of this device is to employ it for high density applications over long-haul transmission. It multiplexes and demultiplexes 40 DWDM wavelengths with 100 GHz in a ring or point-point network. It is a highly cost-effective DWDM Mux/Demux module.

40ch-dwdm-mux-demux

Conclusion

To improve the efficiency of network transmission, WDM technology is often deployed in the devices. 18-CH CWDM Mux/Demux and 40-CH DWDM Mux/Demux are now recommended as the most cost-effective WDM solutions with expanded fiber capabilities. Hope you can choose and use them wisely.

What Is CWDM?

As we all known, WDM (wavelength division multiplexing) is a technology that can transmit multiple different wavelength lasers on a single optical fiber, and widely used in optical networks. CWDM (coarse wavelength division multiplexing), as one type of WDM technology, first came in the 1980s, mainly being used to transmit digital video signal in the multimode fiber. However, it did not interest telecommunication service providers much until now. In recent years, with the development of metropolitan area network which has short transmission distance and do not need optical amplifier, there is a growing technology investment for it because it is a cost-effective solution for telecommunication service providers. We could say this is the time that CWDM exists with great significance.

Introduction of CWDM

As we said above, CWDM is one type of WDM technology, oriented to metropolitan area network. According to ITU-T G.694.2 standard, it has three wavelength bands: O band, E band and S+C+L band. The wavelength of O band is about 1270 nm, 1290 nm, 1310 nm, 1330 nm and 1350 nm. The wavelength of E band is about 1370 nm, 1390 nm, 1410 nm, 1430 nm and 1450 nm. As to S+C+L band, the wavelength is about 1470 nm, 1490 nm , 1510 nm, 1530 nm, 1550 nm, 1570 nm, 1590 nm and 1610 nm. And the channel spacing in CWDM system is typically 20 nm as the picture shows below. So the number of its channels on the same link can be up to 18. And due to its wide channel spacing the temperature control could not be so rigid. Typically, its operating temperature is from 0 to 70°C. And the use of uncooled lasers brings a low cost.

Typical transmittance for coarse wavelength multiplexer

Advantages of CWDM

One of the biggest advantage of CWDM is low cost. As we have mentioned before, CWDM with the wider channel spacing do not need rigid temperature stability control, so the construction of laser device could be simplified. This feature of it is of great help to reduce the cost.

Another advantage of CWDM is that it has small volume and low power consumption. The laser in CWDM system do not need semiconductor cooler and temperature controlling, so it can reduce the power consumption obviously. Its power consumption is only 0.5 W. And the laser module which is simplified in CWDM system can make the volume of optical transceiver module reduced so that it can save a lot of room space.

Application of CWDM

With these advantages, CWDM technology is applied in various areas now, such as enterprise LAN and SAN connection, central office to customer premise interconnection and so on. And one of the most commonly devices is CWDM SFP. CWDM SFP is the transceiver which made by CWDM technology. It is of great simplicity, flexibility and interoperability. Mostly there are eight center wavelengths available from 1470nm to 1610nm, with each step 20 nm. Of course, there are some other CWDM devices,too. But today we are not going to list the products.

In a word, because of its good capacity and low cost, CWDM provides a better solution for metropolitan area network. I believe it will be a hot spot in metropolitan area network construction in the next few years.

WDM Overview

With the development of the computers, mobile phones and some other things, there is an increasing eagerness for more traffic volume of telecommunication. So WDM, with more bandwidth and faster data transmission rate, comes into being.

WDM is a technology to send multiple different wavelength lasers on a single optical fiber. As shown in the picture below, there are different signals coming from different channels. when through the multiplexer, they can be transmitted on a single fiber without obstructed by each other at a high speed. And then, when they are through the demultiplexer, they will be allocated into different channels. The multiplexer and the demultiplexer are the most important parts in WDM systems, just like transmitter and receiver. When signals are transmitted to the network medium on the fiber links, they will be amplified. And after through the network medium, the signals will still be amplified on the fiber links untill they are received by the receiver.

WDM-wavelength division multiplexing

Currently, there are two types of it in the market. CWDM, short for coarse wavelength division multiplexing, is a low-cost WDM transmission technology. Another type is DWDM, namely, dense wavelength division multiplexing. The primary difference between them is the channel spacing. The channel spacing of CWDM is wider than DWDM, so that the number of its channels on the same link could be reduced relatively. As a result, its optical interface components does not need to be precise as same as DWDM.

Now the technology of WDM is widely used in optical networks. Why can it be so widely used? The reasons is closely linked to its features. First, it has Super capacity transmission technology. The transmission capacity can be up to 300-400 Gbit/s or even larger. Second, it can save fiber resources. No matter how many SDH subsystems there are, the whole reuse system only needs a pair of optical fiber. Third, it can work with EDFA that strengthens and restores the attenuated signals in the long-distance transmission, so that it can reduce the cost. Forth, it can improve the reliability of the system. Because most WDM systems are the photoelectric devices which have high reliability. This is a guarantee for the system reliability.

As the optical communication technology progressed further, WDM will be developed in some aspects. In terms of DWDM, Something still needs to be improved such as cost, so that more customers can adopt it.

About single wavelength BiDi transmission technology solutions

The single wavelength BiDi transmission technology offers a unique solution to meet these apparently conflicting goals at the same time, particularly in access networks such as FTTx and in wireless backhaul networks between a base station and antenna tower or aRRH, compared with the two-wavelength BiDi transmission and the duplex transmission which are currently in use. This article presents pros and cons between competing technologies, operating principles of the single wavelength transmission technology and its applications, and Fiberstore’s BiDi transmission products. For example, in a P2P upstream signal from the subscriber to the CO. The optical transceivers at two ends of a transmission link can be identical if one wavelength is used for both directions. However, the CAPEX and OPEX are much higher due to the cost for two fibers and their installation compared with other BiDi technologies described below which use a single fiber. This technology can be used in the wavelength division multiplexing(WDM) communication as well as in the P2P communication.

These wavelengths are separated widely from each other. For example, in a P2P access network, the downstream signal from the CO to a subscriber is at 1550 nm and the upstream signal from a subscriber to the CO is at 1310 nm. The fact that a different signal wavelength must be used in each opposite direction of transmission imposes on the network operators two disadvantages. For example, in a P2P access network , the wavelength can be at 1550nm (or 1310 nm) for both downstream and upstream signals. This reduces CAPEX and OPEX for the network operators since they need to deploy only one kind of optical transceivers at 1550 nm (or 1310 nm). This also guarantees a foolproof installation of transceivers without any confusion since all the transceivers are identical and there is one fiber. In a WDM BiDi system, this is only a viable approach for providing each channel a fully bi-directionally dedicated (or symmetric) bandwidth. This technology may face between upstream and downstream signals a crosstalk and an interferometric beat noise, both coming from reflections at the interface between a transceiver and a channel link fiber with PC (or UPC) type connectors , which may impose a limit on the maximum allowable channel loss, or in other words, the maximum transmission distance. These reflections, however, can be mitigated by using APC type connectors.

Here is a table that summarizes pros and cons of various BiDi transmission technologies. The single wavelength BiDi clearly shows its own unique advantages over two other competing technologies, two-wavelength BiDi and Duplex.

The single wavelength BiDi transmission technology allows over a single fiber a simultaneous communication in both directions at the almost same wavelength. Here is a figure that shows a simple of such transmission system:The signal wavelengths from two transceivers, downstream signal from Tx 1 and upstream signal from Tx 2, are very close to each other, which explains why this approach is named as “a single wavelength BiDi transmission”.

A BiDi CWDM MUX/DEMUX with 9 Channels in 19

More product introduction:

DWDM 40CH multiplexer

Another Large Core Optical Multiplexing Techniques

There are mainly three different techniques in multiplexing light signals onto a single optical fiber link: Optical Time Division Multiplexing (OTDM), Wavelength Division Multiplexing (WDM), and Code Division Multiplexing (CDM).

  1. OTDM: Separating wavelengths in time.
  2. WDM: Each channel is assigned a unique carrier frequency; Channel spacing of about 50GHz; Includes Coarse WDM (CWDM) and Dense WDM (DWDM).
    • CWDM: Characterized by wider channel spacing than DWDM.
    • DWDM: Uses a much narrower channel spacing, therefore, many more wavelengths are supported.
  3. CDM: Also used in microwave transmission; Spectrum of each wavelength is assigned a unique spreading code; Channels overlap both in time and frequency domains but the code guide each wavelength.

Applications

  • The major scarce resource in telecommunication is bandwidth—users want transmit at more high rate and service providers want to offer more services, hence, the need for a faster and more reliable high speed system.
  • Reducing cost of hardware, one multiplexing system can be used to combine and transmit multiple signals from Location A to Location B.
  • Each wavelength, λ, can carry multiple signals.
  • CWDM 10Gbps serve optical switching of signals in telecommunication and other field of signal processing and transmission.
  • Future next generation internet.

Advantages

  • High data rate and throughput: Data rates possible in optical transmission are usually in Gbps on each wavelength; Combination of different wavelengths means more throughput in one single communication systems.
  • Low attenuation: Optical communication has low attenuation compare to other transport system.
  • Less propagation delay.
  • More services offered.
  • Increase Return On Investment (ROI)
  • Low Bit Error Rate (BER)

Shortcomings

  • Fiber Output Loss and Dispersion: Signal is attenuated by fiber loss and distorted by fiber dispersion, then regenerator are needed to recover the clean purposes.
  • Inability of current Customer Premises Equipment (CPE) to receive at the same transmission rate of optical transmitting systems (achieving all-optical networks).
  • Optical-to-Electrical Conversion Overhead: Optical signals are converted into electrical signal using photo-detectors, switched and converted back to optical. Optical/electrical/optical conversions introduce unnecessary time delays and power loss. End-to-end optical transmission will be better.

Future Work

  • Research in optical end user equipment: Mobile phones, PC, and other handheld devices receiving and transmitting at optical rate.
  • Fast regeneration of attenuated signal.
  • Less distortion resulting from fiber dispersion.
  • End-to-end optical components: Eliminating the need for Optical-to-Electrical converter and vise versa.

While optical transmission is better compare to other transmission media because of its low attenuation and long distance transmission profile, optical multiplexing is useful in signal CWDM combination MUX DEMUX processing and transmission by transporting multiple signals using one single fiber link. As the growth of the internet requires fiber optic transmission to achieve greater throughput, optical multiplexing is also useful in image processing and scanning application.

How Much Do You Know About CWDM SFPs?

You must be very interested in some SFP modules which are with colorful markings, such as color arrow on label and color coded bale clasp. But do you know what are these colorful SFPs used for? And why are they designed as several color? This paper is going to introduce one type of these colorful SFP transceiver modules.

These SFPs with color arrow on label and color coded bale clasp are called WDM(Wavelength Divison Multiplexing) SFPs. WDM SFPs are devided into two basic types. One is CWDM(Coarse Wavelength Divison Multiplexing) SFPs, and the other one is DWDM(Dense Wavelength Division Multiplexing) SFPs. This paper is mainly about the CWDM SFPs. The different colors represent different wavelength.

What’s CWDM SFP? CWDM SFP is a kind of optical transceiver which combines the CWDM technology. Similar with the traditional SFPs, CWDM SFP is also a hot-swappable input/output device that plugs into an SFP port or slot of a switch or router, and links the port with the fiber-optic network. It is a convenient and cost-effective solution for the adoption of Gigabit Ethernet and Fibre Channel (FC) in campus, data-center, and metropolitan-area access networks.

Fiberstore-Cisco-compatible-CWDM-SFPs

CWDM SFPs With Different Wavelengths In general, CWDM SFPs come in eight wavelengths that range from 1470 nm to 1610nm. In order to better identify the wavelength to which the Gigabit Ethernet channel is mapped when using these CWDM SFPs, we use the color markings on the devices, such as color arrow on label and color coded bale clasp to achieve it. This is why there are many SFPs with different colors for applications. Here, we take Cisco for example. Here, we take Cisco for example. The following table lists the CWDM SFPs with their wavelength and color codes.

cisco cwdm sfp information

Standards and Regulatory Compliance

  • RoHS compliant
  • IEEE Std 802.3 (Gigabit Ethernet 802.3z,802.3ah, FastE 802.3u)
  • Fibre Channel Draft Physical Interface Specification FC-PI-2
  • Compliant with SONET/SDH optical standards
  • SFP MSA (multi-source agreement)

Protocols and Data Rates

  • Fast Ethernet (125Mbps)
  • Gigabit Ethernet (1.25Gbps)
  • 1G and 2G Fibre Channel
  • SONET OC-3 (155Mbps), OC-12 (622Mbps), and OC-48 (2.488Gbps)

Fiberstore CWDM SFPs Solution Fiberstore offers a cost-effective CWDM SFPs solution which is 100% compatible with many devices of major brands, e.g. Cisco, HP or Juniper etc. Compatible CWDM SFPs with multi-rate transceiver for data rates from 100 Mbps up to 4 Gbps, transfer distance at 20 to 40km, 40 to 80km and 80 to 120km as well as different color marking options are available in Fiberstore which can better satisfy the different requirements on parameters of our clients. CWDM SFP transceivers also feature digital diagnostics, also known as digital optical monitoring (DOM), which is supported by the majority of switch and router OEMs in their operating system software.

CWDM-SFP-COLOR-CODING

For Cisco users, we highly recommend our CWDM SFP products, such as CSFP-1G47-80-CO, CSFP-1G49-80-CO, CSFP-1G51-80-CO, CSFP-1G53-80-CO, CSFP-1G55-80-CO, CSFP-1G57-80-CO, CSFP-1G59-80-CO, CSFP-1G61-80-CO that are the corresponding compatible CWDM SFPs of Cisco’s. Additionally, we can offer other products which are the custom version for Cisco compatible. Actually, more products are waiting for you. If you want to order other brand compatible or get more information about these products, we welcome you to visit our website or contact us over E-mail sales@fs.com directly.