DWDM Network over Long Distance Transmission

With the ever-increasing need for higher bandwidth, DWDM technology has been one of the most favorable optical transport network (OTN) applications. In this post, we will reveal FS.COM DWDM-based network solutions over various transmitting distances as well as some suggestions for the DWDM networks deployment.

DWDM Networks Basics

As usual, let’s review some basics of DWDM networks. In this part, we will figure out two questions: What is DWDM? What are the components of DWDM networks?

DWDM Technology
DWDM Networks

Figure 1: DWDM Networks

DWDM (Dense Wavelength Division Multiplexing) is an associate extension of optical networking. It can put data signals from different sources together on a single optical fiber pair, with each signal simultaneously carried on its own separate light wavelength. With DWDM, up to 160 wavelengths with a spacing of 0.8/0.4 nm (100 GHz/50 GHz grid) separate wavelengths or channels of data can be transmitted over a single optical fiber.

DWDM Networks Components

Conventionally, for DWDM networks, there are four devices showed as below that are commonly used by IT workers:

  • Optical transmitters/receivers
  • DWDM mux/demux filters
  • Optical add/drop multiplexers (OADMs)
  • Optical amplifiers transponders (wavelength converters)

DWDM Networks Over Long Distance Transmission Solutions

Scenario 1: 40 km Transmission
40km DWDM Network

Figure 2: 40km DWDM Network

For this case, the 80km DWDM SFP+ modules and 40ch DWDM Mux/Demuxs are recommended to use. Since the 80km DWDM SFP+ modules are able to support 10G transmission over 40 km, no additional device is needed under this scenario.

Scenario 2: 80 km Transmission
80km DWDM Network

Figure 3: 80km DWDM Network

Deploying this 80 km DWDM network, we will still use 80km DWDM SFP+ modules and 40ch DWDM Mux/Demuxs. The light source of 80km DWDM SFP+ modules might not be able to support such long transmission distance, as there might be a light loss during transmission. In this case, pre-amplifier (PA) is usually deployed before the location A and location B to improve the receiver sensitivity and extend signal transmission DWDM distance. Meanwhile, the dispersion compensation module (DCM) can be added to this link to handle the accumulated chromatic dispersion without dropping and regenerating the wavelengths on the link. The above diagram shows the deploying method of this 80km DWDM network.

Scenario 3: 100 km Transmission
100km DWDM Network

Figure 4: 100km DWDM Network

Under this scenario, the devices used in scenario 2 still need to remain. Since the transmission distance has been increased, the light power will be decreased accordingly. Besides that, you will also need to use booster EDFA (BA) to amplify the optical signal transmission of the 80km DWDM SFP+ modules.

By the way, if you want to extend DWDM transmission distance, you can read this post for solutions: Extend DWDM Network Transmission Distance With Multi-Service Transport Platform.

Factors to Consider in Deploying DWDM Networks

1. Being compatible with existing fiber plant. Some types of older fiber are not suitable for DWDM use. Currently, standard singlemode fiber (G. 652) accounts for the majority of installed fiber, supporting DWDM in the metropolitan area.

2. Having an overall migration and provisioning strategy. Because DWDM is capable of supporting massive growth in bandwidth demands over time without forklift upgrades, it represents a long-term investment. Your deployment should allow for flexible additions of nodes, such as OADMs, to meet the changing demands of customers and usages.

3. Network management tools. A comprehensive network management tool will be needed for provisioning, performance, monitoring, fault identification and isolation, and remedial action. Such a tool should be standards-based (SNMP, for example) and be able to interoperate with the existing operating system. For example, the FMT DWDM solutions from FS.COM are able to support kinds of network management, including NMU line-card, monitor online, simple management tool, and SNMP.

4. Interoperability issues. Because DWDM uses specific wavelengths for transmission, the DWDM wavelengths used must be the same on either end of any given connection. Moreover, other interoperability issues also need to be considered, including power levels, inter- and intra-channel isolation, PMD (polarization mode dispersion) tolerances, and fiber types. All these contribute to the challenges of transmission between different systems at Layer 1.

5. Strategy for protection and restoration. There might have hard failures (equipment failures, such as laser or photodetector, and fiber breaks) and soft failures such as signal degradation (for example, unacceptable BER). Therefore, you need to have a protection strategy while deploying a DWDM network.

6. Optical power budget or link loss budget. Since there might be an optical signal loss over the long distance transmission, it’s critical to have a link loss budget in advance.

Summary

Bringing great scalability and flexibility to fiber networks, the DWDM networks solutions obviously enjoys plenty of strengths, which is also proved to be future-proof. In this post, we make a revelation of the DWDM-based network over long distance transmission. Also, some tips for deploying a DWDM network has also been shared for your reference.

Open Switch—One Contributor to Open Source Network

With the higher and higher demand for network agility and scalability, traditional networking has been no longer satisfying. In that case, the open source network has been an urgent need. To meet with this new trend, here comes our open switch, a great contributor to the open networking.

What Is Open Switch?

Open switches refer to switches in which the hardware and software are separate components that can be changed independently of each other. That means you will gain more flexibility to tailor your own network switch. Conventionally, the open source switch in the market can mainly be classified into the bare metal switch, white box switch, and brite box switch.

Open Switch

Figure 1:Open Switch

Open Switch Hardware

The open hardware means the hardware of an open switch can support multiple operating systems (OS). This is in contrast to closed switches, in which the hardware and software are always purchased together. For example, if you buy a Juniper EX or MX you also buy JUNOS; if you buy a Cisco Catalyst switch you buy IOS. However, things will be different with open switches. In the context of that, no matter which type of open source switch you are using, it’s possible to support many operating systems instead of a proprietary one. By the way, the hardware manufacturers of the open switch are primarily Taiwanese, including Accton, Quanta QCT, Alpha Networks, and Delta Computer. These same companies are original design manufacturers (ODMs) for many of the mainstream switch vendors.

Open Hardware

Figure 2: Open Hardware

Open Switch Software

The open software signifies that an OS can be run on multiple hardware configurations. As we mentioned before, you don’t need to buy an OS from the original brand of your switch hardware. For example, if you have Cumulus Linux, you can buy a layer 3 switch without a brand label. They still work well with each other. In the past, most people have no choice but to use brite box switch that integrates OS and hardware of branded suppliers. Now, with an open switch software, choices and economic efficiency will be largely expanded and improved. Generally, there are three popular open softwares in the market: Cumulus Linux, IP Infusion OcNOS and Pica8 PICOS.

Cumulus Linux Software

Figure 3: Cumulus Linux Software

Why Choose Open Switch?

  • With an open source switch, more flexibility, and options can be enjoyed. There is no need to configure your switch as in the past or wait for vendors to release new software or hardware.
  • It brings the open source network to operators, enterprises, third-party vendors and network users, accelerates the innovation speed of new services and functions of the network deployment, and takes users closer to SDN (software-defined network) and NFV (network functions virtualization).
  • The network simplicity and reliability can be improved through the automated centralized network device management, unified deployment strategies, and fewer configuration errors.
  • The network flexibility and scalability have been greatly increased, which will also save much cost and time for IT workers and enterprises.

Summary

In this post, we make an exploration of the open switch. From the introduction to its hardware, software, and benefits, we can understand why the open switch has been a great facilitator for open networking.

An Overview on EVPN and LNV

Bombarded with assorted network applications and protocols, the technologies and solutions for network virtualization delivery have been enriched greatly over past years. Among those technologies, VXLAN, also called virtual extensible local area network, is the key network virtualization. It enables layer 2 segments to be extended over an IP core (the underlay). The initial definition of VXLAN (RFC 7348) only relied on a flood-and-learn approach for MAC address learning. Now, a controller or a technology such as EVPN and LNV in Cumulus Linux can be realized. In this post, we are going to make an exploration on those two techniques: LNV and EVPN.

VXLAN

Figure 1: VXLAN

What Is EVPN

EVPN is also named as Ethernet VPN. It is largely considered as a unified control plane solution for the controller-less VXLAN, allowing for building and deploying VXLANs at scale. The EVPN relies on multi-protocol BGP (MP-BGP) to transport both layer 2 MAC and layer 3 IP information at the same time. It enables a separation between the data layer and control plane layer. By having the combined set of MAC and IP information available for forwarding decisions, optimized routing and switching within a network becomes feasible and the need for flooding to do learning gets minimized or even eliminated.

What Is LNV

LNV is the short of lightweight network virtualization. It is a technique for deploying VXLANs without a central controller on bare metal switches. Typically, it’s able to run the VXLAN service and registration daemons on Cumulus Linux itself. The data path between bridge entities is established on the top of a layer 3 fabric by means of a simple service node coupled with traditional MAC address learning.

The Relationship Between EVPN and LNV

From the above wiki of the EVPN and LNV, it’s easy for us to notice these two technologies are both the applications of VXLAN. For LNV, it can be used to deploy VXLAN without an external controller or software suite on the bare-metal layer 2/3 switches running Cumulus Linux network operating system (NOS). As for EVPN, it is a standards-based control plane for VXLAN, which can be used in any usual bare-metal devices, such as network switch and router. Typically, you cannot apply LNV and EVPN at the same time.

Apart from that, the deployments for EVPN and LNV are also different. Here, we make a configuring model for each of them for your better visualization.

EVPN Configuration Case

 

EVPN

Figure 2: EVPN

In the EVPN-VXLAN network segments shown in Figure 2 (Before), hosts A and B need to exchange traffic. When host A sends a packet to host B or vice versa, the packet must traverse the switch A, a VXLAN tunnel, and the switch B. By default, routing traffic between a VXLAN and a Layer 3 logical interface is disabled. If the functionality is disabled, the pure Layer 3 logical interface on the switch A drops Layer 3 traffic from host A and VXLAN-encapsulated traffic from the switch B. To prevent the pure Layer 3 logical interface on the switch A from dropping this traffic, you can reconfigure the pure Layer 3 logical interface as a Layer 2 logical interface, like Figure 2 (After). After that, you need to associate this interface with a dummy VLAN and a dummy VXLAN network identifier (VNI). Then, an Integrated routing and bridging (IRB) interface need to be created, which provides Layer 3 functionality within the dummy VLAN.

LNV Configuration Case

 

LNV

Figure 3: LNV

The two layer 3 switches are regarded as leaf 1 and leaf 2 in the above figure. They are running with Cumulus Linux and have been configured as bridges. Containing physical switch port interfaces, the two bridges connect to the servers as well as the logical VXLAN interface associated with the bridge. After creating a logical VXLAN interface on both leaf switches, the switches become VTEPs (virtual tunnel end points). The IP address associated with this VTEP is most commonly configured as its loopback address. In the image above, the loopback address is 10.2.1.1 for leaf 1 and 10.2.1.2 for leaf 2.

Summary

In this post, we have introduced the two techniques of network virtualization: EVPN and LNV. These two applications of network virtualization delivery share some similarities, but also quite a lot of differences. Being satisfied with the simplicity, agility, and scalability over the network, the EVPN has been a popular choice in the market.

MTP Solutions for High-Density Needs

With the ever-increasing demands for high-density backbone cabling. MTP solutions have enjoyed widespread popularity. In this post, we will have an exploration of two MTP solutions: MTP cable and MTP cassette. For those who are unfamiliar with this term, it’s necessary for us to get started from its basics.

Background Information on MTP

In this part, you are required to acquire three terms: MTP, MPO, and polarity.

MPO

MPO stands for “multi-fiber push on” connector. Usually, it refers to a type of a multiple fiber core connector, defined by IEC-61754-7 (common standard) and the U.S. TIA-604-5 Standard.

MTP

MTP is the short for “multi-fiber termination push-on” connector, which is the latest generation of MPO connector developed by US Conec. Fully compliant with the MPO standards, the multi-fiber termination push-on connector is considered as MPO fiber connector. For multi-fiber termination push-on or multi-fiber push on connector, they can both accommodate 8 to 24 fibers, which are the perfect choices for the 40G/100G network. Multi-fiber termination push-on or multi-fiber push on connector is available in a female version (without pins), or a male version (with pins) as shown in figure 1. The pins ensure the exact alignment of the fronts of the connectors, which protects the interfaces of the connectors from being offset.

MTP Connectors

Figure 1: MTP Connectors

Also, there are guide grooves (keys) on the top side of the factory terminated multi-fiber termination push-on connectors, which ensure that the adapter holds the connector with the correct ends aligned with each other. According to the key, the multi-fiber termination push-on connector comes with two types. One is “key-up to key-down”, which means the key is up on the one side and down on the other. The two connectors are connected turned 180°in relation to each other. The other one is “key-up to key-up”, which means both keys are up. The two connectors are connected while in the same position in relation to each other.

MTP Connector Structure

Figure 2:  Multi-fiber Termination Push-on Connector Structure

Polarity

In any installation, it is important to ensure that the optical transmitter at one end is connected to the optical receiver at the other. This matching of the transmitting signal (Tx) to the receiving equipment (Rx) at both ends of the fiber optic link is referred to as polarity.

MTP Solutions

For multi-fiber termination push-on solutions, there are two frequently used applications: MTP cable and multi-fiber termination push-on cassettes. They are the best choices for providing a simple, cost-effective, and structured cabling system.

MTP Solutions

Figure 3: MTP Solutions

Cables

Multi-fiber termination push-on cables usually consist of the multi-fiber termination push-on connectors and the fiber optic cables. Sometimes, the LC connectors are used, which we will expound in the following part. As for fiber cables, they are typically used in OS2, OM3 or OM4. With different applications, the multi-fiber termination push-on cable can be classified into multi-fiber termination push-on trunk cable and multi-fiber termination push-on harness cable.

Trunk Cable

Serving as a permanent link, the trunk cable is designed to connect multi-fiber termination push-on or multi-fiber push on modules to each other. It’s available in 12, 24, 48 and 72 fibers. For the ends, the cable is commonly found to be terminated with 12-fiber or 24-fiber multi-fiber termination push-on or multi-fiber push on connectors. When it comes with the polarity of the patch cord, there are three different types (type A, B, and C), which is defined in the TIA standard. In the following figures, the three different connectivity methods for 12-fiber and 24-fiber MTP/MPO trunk cable are showed respectively.

12-Fiber MTP Trunk Cable

Figure 4: 12-Fiber Multi-fiber Termination Push-on Trunk Cable

24-Fiber MTP Trunk Cable

Figure 5: 24-Fiber Multi-fiber Termination Push-on Trunk Cable

Harness Cable

Multi-fiber termination push-on harness cable is used to provide a transition from multifiber cables to individual fibers or duplex connectors. For instance, 8 fibers 12 strands MTP-LC breakout cable has eight LC fiber connectors and a multi-fiber termination push-on connector. According to data of FS.COM, the 8-fiber and 24-fiber MTP to LC breakout cables are the best-selling multi-fiber termination push-on connector harness cables. For the polarity, the 8-fiber multi-fiber termination push-on connector breakout patch cord has two types (Type A and Type B); while the 24-fiber harness cable has three types (Type A, Type B, and Type C). For details, please refer to the following figures.

12-Fiber MTP Harness Cable

Figure 6: 12-Fiber Multi-fiber Termination Push-on Harness Cable

24-Fiber MTP Harness Cable

Figure 7: 24-Fiber Multi-fiber Termination Push-on Harness Cable

 Cassette

MTP-cassette is a kind of pre-terminated cassette module. It enables the “transition” from ribbon cables terminated with multi-fiber termination push-on connector connectors to the LC or SC interface on the transceiver terminal equipment. Conventionally, the multi-fiber termination push-on connector cassette is loaded with 8, 12 or 24 fibers and have LC or SC adapters on the front side and multi-fiber termination push-on connector at the rear. Nowadays, the three most widely used cassettes are MTP-8, MTP-12, and MTP-24 cassettes, or also known as Base-8, Base-12, and Base-24 multi-fiber termination push-on cassettes. For MTP-8 cassette, it is only available in Type A. While multi-fiber termination push-on-12 and multi-fiber termination push-on-24 cassettes both come with Type A and Type AF. For their polarity details, please refer to the following figures.

MTP-8 Cassette

Figure 8: Multi-fiber Termination Push-on-8 Cassette

MTP-12 Cassette

Figure 9:  Multi-fiber Termination Push-on-12 Cassette

MTP-24 Cassette

Figure 10:  Multi-fiber Termination Push-on-24 Cassette

Summary

In this post, we make an overview of MTP, including what the multi-fiber termination push-on and multi-fiber push on, and what their the polarities are. Then we share three types of multi-fiber termination push-on solutions for high-density networking: MTP trunk cable, MTP harness cable, and MTP cassette.

What Cable Should I Use for 10G Transceiver Module?

To deploy the optical network, the transceiver module and patch cable are the two basic components. According to the feedbacks of customers from FS.COM, one of the common problems faced by them is what cables they should use for their transceiver modules. To solve this problem, we make this post of patch cable selection guidance. Since the order for 10G transceivers ranks top, we are going to take 10G modules as a reference.

An Overview of 10G Transceiver Module

Transceiver module, also called fiber optic transceiver, is a hot-pluggable device that can both transmit and receive data. By combining a transmitter and receiver into a single module, the device converts electrical signals into optical signals to allow these signals to be efficiently transferred on fiber optic cables. As for the 10G transceiver, it refers to the optical modules with 10G data rate. In FS.COM, there are mainly four types of 10G transceivers: XENPAK, X2, XFP, and SFP+. Even though these optical transceivers are all accessible to the 10G networks, they have different matching patch cables and applications.

10G Transceiver Module

Figure 1: 10G Transceiver Modules

Patch Cable Basics

Apart from optical module, the patch cable is the other vital role in networking. Patch cable, also called patch cord, refers to the copper or optical cable. It’s designed to connect one electronic or optical device to another for signal routing. Conventionally, the patch cable will be terminated with connectors at both ends. For example, the LC fiber cable refers to the optical cable fixed with LC connector. Typically, there are LC, SC, ST, FC and MTP/MPO fiber patch cables. According to different features, we can get various classifications of patch cables, such as fiber types, polishing types, etc.

Patch Cables

Figure 2: Patch Cables

Factors to Consider When Choosing Patch Cable for 10G Transceiver Module

Recently, most of the 10G transceiver modules are compatible with different brands and support higher data rates. It will be much easier to choose optical modules for your networking than selecting mating patch cables. Based on most applications, there are three major factors that can be taken into consideration: transmission media, transmission distance, and transceiver module interface.

Transmission Media

Classified by transmission media, two types of patch cables can be found in the market: optic fiber cable and copper cable. Correspondingly, there are two kinds of optical transceivers available: copper-based transceivers and fiber optic based transceivers. Copper transceiver modules like 10GBASE-T SFP+, they have an RJ45 interface, connecting with copper cables. Typically, Ethernet cables that support 10G copper-based transceivers are Cat7 and Cat6a cables.

As for the 10G optical modules, they can support higher data rates over optic fiber cables. It will be more complicated to choose fiber cables. Generally, there are multimode fibers and single mode fibers. Based on the specified needs for transmission distance, the answer will be varied.

Transmission Distance

To select cables, the transmission distance is also an important factor that you need to take care. In the following table, we list the basic information of common 10G transceivers, including their supporting fiber cable types and transmitting distance.

Transceiver Type
Wavelength
Cable Type
Transmission Distance
SR
850 nm
MMF
300 m
LR
1310 nm
SMF
10 km
ER
1550 nm
SMF
40 km
ZR
1550 nm
SMF
80 km

As for fiber cables, single mode fiber is used for long-distance transmission and multimode fiber is for short distance. In a 10G network, the transmission distance of single mode fiber (OS2) can reach from 2 km to 100 km. When it comes to multimode fibers, the transmission distances for OM1, OM2, OM3 are 36 m, 86 m and 300 m. OM4 and OM5 can reach up to 550 m.

Transceiver Module Interface

Another factor you need to consider is the transceiver interface. Usually, transceivers use one port for transmitting and the other port for receiving. They tend to employ duplex SC or LC interface. However, for 10G BiDi transceivers, it only has one port for both transmitting and receiving. Simplex patch cord is applied to connect the 10G BiDi transceiver.

Summary

For your 10G network cabling, transceiver module and patch cable are necessary components. With a wide range of patch cables, selecting the right patch cables will be more complex than 10G transceivers. Generally, three major factors can be considered: transmission media, transmission distance, and transceiver module interface. To apply what you have learned in this post in cabling, you can visit FS.COM for all the transceivers and patch cables at one shop.