Posted in XFP

How Much Do You Know About FTTH PON Testing?

Passive optical network (PON) is a cost-effective way to deliver high-bandwidth broadband services to users and widely deployed all over the world. FTTH uses PON technology and provides high bandwidth from the central office (CO) to subscribers. FTTH PON system achieves network reliability and makes network testing, monitoring and measuring easier. This article will tell about FTTH PON testing from the four aspects below.

Connector Inspection

Connector inspection/cleaning plays an important role in network installation and maintenance. Typically an optical microscope is used for connector inspection. To prevent accidental eye damage when inspecting fibers potentially carrying live traffic, a video microscope images the connector end-face and displays the magnified image on a handheld display. In this way, the dirt, debris or damage on the connector could be easily detected. According to the study by NTT-Advanced Technology, connector contamination and damage are the key reason for poor optical network performance.

Insertion Loss Test

In telecommunications, the term “insertion loss” expressed in dB, refers to the loss of signal power resulting from the insertion of a device in a transmission line or in an optical fiber. An insertion loss test measures the end-to-end loss of the installed link by injecting light with a known power level and wavelength at one end, and then measures the received power level output from the other end. The measured difference between the transmitted and received power levels exactly indicates the very optical loss through the network. In some occasions, insertion loss is allowed and considered acceptable when the measured loss level is lower than the budget loss level.

Optical Return Loss Test

In telecommunications, return loss expressed in dB, means the loss of power in the signal returned or reflected by a discontinuity in a transmission line which can be a mismatch with the terminating load or with a device inserted in the line. The optical return loss test injects light with known wavelength and power level into one end and measures the power level returned to that same end. Then the return loss is the difference between the injected power level and the measured return level. When the return loss is higher than the budgeted return loss target, it is considered acceptable.

Typically insertion loss test and return loss test are performed by using wavelengths at those which will be used during network operation. For FTTH PON system, 1310nm wavelength is used in the upstream direction, while 1490nm and 1550nm wavelengths are used in the downstream direction. So it is essential to have insertion and return loss testing at 1310nm, 1490nm and 1550nm wavelengths. The optical network is considered ready for activation when the insertion loss and return loss measured at each wavelength are within the budgeted levels for the link. However, in some cases, the network operator uses an optical time domain reflectometry (OTDR) as the following picture shows for more fully documented network.

JDSU MTS 4000 OTDR

Optical Time Domain Reflectometry (OTDR)

OTDR scans a fiber from one end to measure the length, loss and optical return loss of an optical network. And it also locates and measures reflective or non-reflective events in the network caused by splices, connectors, splitters, faults, etc. OTDR operates like a radar by injecting narrow pulses of light into the fiber under test. As each pulse travels down the fiber, imperfections in the fiber scatter some of the light, with some of this Rayleigh-scattered light being guided back up the fiber.

Summary

From the above description, four tests are commonly used to verify optical links. Proper testing is critical for FTTH PON installing, activating and maintaining, because excess loss or reflectance can result in poor network performance if not detected and corrected. And over time, transmission errors will occur before the need for any maintenance activity.

Originally published at How Much Do You Know About FTTH PON Testing? – Fiber Optic Network Products | FS.COM

Advertisements
Posted in Article, Optical Transceiver

Suggested 100G QSFP28 Transceiver Solutions for Data Centers

In recent years, QSFP28 transceiver module has upgraded the 100G market which can support the data transmission mode of 4×25G. Currently many data centers have already adopted QSFP28 transceivers for 100G migration. Of course, there are many other types of transceivers can transfer the 100G network, but QSFP28 modules are still considered to be the optimal choice. This post is going to present some useful 100G QSFP28 transceiver solutions for data centers. Maybe one of them is exactly what you need.

Basics of QSFP28 Optical Transceiver

QSFP28 transceiver is designed for high-density and high-speed for applications in telecommunications. The transceiver offers four channels of different signals with data rates ranging from 25 Gbps up to potentially 40 Gbps, and meets 100 Gbps Ethernet (4×25 Gbps) and 100 Gbps 4X InfiniBand Enhanced Data Rate (EDR) requirements. QSFP28 optical transceiver has various advantages. It has a smaller size than other 100G modules, thus it is ideal for high-density ports on the switch. Power consumption of QSFP28 transceiver is usually the lowest of less than 3.5W. In addition, QSFP28 increases the transmission capacity of every lane from 10G to 25G, which can save much cost for each bit.

QSFP28 Transceiver Solutions

QSFP28 transceivers can be categorized into several types based on different IEEE (Institute of Electrical and Electronics Engineers ) or MSA (Multi-source Agreement) standards.

100GBASE-SR4 is the IEEE standard for 100G QSFP28 that supports short distance over multimode. It can reach 100G transmission up to 70m over OM3 and 100m over OM4. With the MTP/MPO interface, 100GASE-SR4 QSFP28 transceiver supports four lanes of 25G dual way transmission over eight fibers.

qsfp28-sr4

100GBASE-LR4 is also the IEEE standard for QSFP28 module but supports long distance transmission for the maximum of 10km over single-mode fiber. 100GBASE-LR4 QSFP28 is special for adopting the WDM technologies for four 25G lanes transmission over four different wavelengths. In addition, its duplex LC interface supports the 100G dual-way transmission.

qsfp28-lr4

100GBASE-PSM4 is the standard defined by MSA for the point-to-point 100G link over eight single-mode fibers reaching the length of up to 500m. 100GBASE-PSM4 QSFP28 transceiver uses four identical and independent lanes for each signal direction with each lane carrying a 25G optical transmission. With the MTP/MPO interface, optical fiber ribbon cables with MTP/MPO connectors can be plugged into the QSFP28 module.

qsfp28-psm4

100GBASE-CWDM4 standard was released by CWDM MSA to support 100G network for up to 2km. It uses the CWDM technology to reduce the transmission on 8 fibers (4 optical transmitters and four optical receivers) into 2 fibers. This transceiver is similar to 100GBASE-LR4 QSFP28 but has a shorter transmission range and lower cost.

qsfp28-cwdm4

Conclusion

In a word, QSFP28 modules are suggested transceiver solutions for upgrading the data center 100G network. The 100GBASE-SR4, 100GBASE-LR4, 100GBASE-PSM4, and 100GBASE-CWDM4 QSFP28 transceivers mentioned above are the most popular ones to ensure the high-speed data transmission at either short or long distance. FS.COM offers both generic and compatible QSFP28 modules according to your demands. Other than QSFP28 transceivers, there are also many other types of 100G transceivers, such as CFP, CFP2, CFP4, CXP transceivers. For more information, please kindly visit FS.COM or contact us directly via sales@fs.com.

Source:http://www.fiber-optic-cable-sale.com/suggested-100g-qsfp28-transceiver-solutions-data-centers.html

Posted in Article, Optical Transceiver

How to Clean a Fiber Optic Transceiver?

To ensure the high performance of optical data transmission, fiber optic cleaning is regarded as an essential way to get rid of the contaminants on devices. Fiber optic connectors are often recommended to be cleaned on a regular basis. Apart from the connectors, other devices such as fiber optic transceiver, optical adapter should also be cleaned when they are being polluted. This post will focus on introducing the proper method of cleaning fiber optic transceivers.

How to Find a Contaminated Optical Transceiver?

Compared with connectors, transceiver modules seem to have a smaller chance to be contaminated. Therefore, fiber optic transceivers should only be cleaned when problems occur. Generally, if signal output from the transceiver is still false or in low-power after cleaning the connectors, you can clean the fiber optic transceiver instead to solve the issue. Common contaminant in optical transceivers is the debris or particles coming through the contact with optical connector ferrules. The following picture shows the comparison of dirty and clean interfaces of transceivers under the digital microscope.

fiber optic transceiver contaminants

Cleaning Tools

Air duster and lint-free swab are the major cleaning tools for fiber optic transceivers. Air duster uses the clean dry air to blow any dust and debris out of the transceiver. Lint-free swab is special for not leaving any lint in the transceiver interface after cleaning.

cleaning tools

Things to Note Before Cleaning

A safe operation is very important to protect yourself from unnecessary accidents. Before starting the cleaning process, here are some precautions for you to note.

  • Always handle optical modules in an ESD (electro-static discharge) safe area using the proper safety precautions.
  • Ensure that the module power is off and handle the modules with care.
  • Always use CDA or an approved canned compressed air supply.
  • Always hold the can of compressed air upright. Tipping may release liquids in the air stream.
  • Do not touch the inner surfaces of the module including the OSA (optical subassemblies), or insert any foreign objects into the ports.
  • Use of finger cots or powder free surgical gloves is not required but can ensure better cleanliness.
Cleaning Procedures

After every thing is ready, you can start to clean the transceiver interface. The followings are the general cleaning steps for reference. If condition permits, you can use microscope to inspect the transceiver to ensure cleanliness. Usually, when output signal becomes normal, then the cleaning procedure is a success.

  • Step 1: Open the dust cover or remove the dust plug from the module.
  • Step 2: Use a non-abrasive cleaner (air duster) to remove any dirt or debris.
  • Step 3: Insert a lint-free cleaning stick of the appropriate size (2.5 mm or 1.25 mm) and turn clockwise. It is recommended to do dry cleaning instead of wet cleaning by using alcohol-based cleaning sticks.
  • Step 4: Repeat steps 2 and 3 if necessary.
  • Step 5: Remove the cleaning stick, and reinsert the module’s dust cap. Always keep the dust cap inserted in the module when not in use.
  • Step 6: Always make sure that the connector is also clean before plugged into the module.
Conclusion

Fiber optic cleaning plays an important role in fiber optic system. Although optical transceivers are less frequent to be cleaned, the request for cleaning still exists. As long as you use the correct cleaning tools and follow the right cleaning procedures, transceivers can surely be cleaned with no more contamination. In this case, the efficiency of fiber optic system will be greatly improved.

Source:http://www.chinacablesbuy.com/clean-fiber-optic-transceiver.html

Posted in Article, Fiber Optic Cable

Basic Things To Know About PM Patch Cables

Standard fiber patch cables are widely discovered in our life, but fiber patch cables also have other special types, such as the mode conditioning cables, fiber loopbacks, etc. These special fiber patch cables are usually used for some particular applications. In this article, we will mainly introduce the basic knowledge of PM (polarization maintaining) patch cables.

PM-patch-cable

Function of PM Patch Cables

In fiber optic industry, polarization maintaining fiber is a single-mode fiber that can maintain a linear polarization light propagation during the whole transmission inside fiber. As long as the light is linearly launched into the fiber, its polarization in the fiber path will not change. PM patch cable is a fiber optic cable consisting of PM fiber and high-quality ceramic fiber optic connectors. With the special polarization maintaining function, PM patch cables have the characteristics of low insertion loss, high extinction ratio, high return loss, excellent changeability over a wide wavelength range and excellent environmental stability and reliability.

How to Choose PM Patch Cables?

PM patch cables have various types according to different classification bases. To choose the right type of PM fiber patch cable, you may consider the following aspects.

Connector

Similar to standard fiber optic cables, the common connectors for PM fiber patch cables are LC, SC, FC and ST types. Connectors on both ends of the cable can be identical or different, such as LC-LC or LC-SC connectors. The special part is that connector ends are capped for better protection since the PM connectors are made to be more sophisticated.

Fiber

PM fiber patch cables all use the PM fibers. However, PM fibers can be different according to different shapes of the inside rod. This special rod can ensure the linear polarization of input and output light in the fiber. The following picture shows the examples of “Panda” and “Bow-Tie” styles of PM fiber.

PM-fiber

Cable Jacket

With or without cable jacket are both common for PM fiber patch cables. Generally speaking, there are three types of PM cables – 250μm bare fiber PM cable, 900μm loose tube jacket PM cable and 3mm loose tube jacket PM cable.

Length

The standard cable length of PM fiber patch cables is 1 meter. If other lengths are required, the cable is able to be customized to the required lengths as well.

Where to Use PM Patch Cables?

Since PM fibers are typically used to guide linearly polarized light from point to point, PM fibers can be used for many special applications in optical sensors or telecommunications and sensor research. PM fiber patch cables are especially useful for polarization sensitive fiber optical systems where optical light needs to be maintained at a linear state. PM fiber patch cables can be used with other devices like interferometric sensors, integrated optics, fiber amplifiers in high-speed and coherent telecommunications.

Conclusion

As one type of special fiber patch cables, PM patch cables are particularly designed for keeping the polarization of linear optical lights. PM patch cable is definitely a good solution to ensure the high performance of data transmission. FS.COM offers various types of PM patch cables with length customization service. If you are interested in more details, please kindly visit FS.COM or contact us via sales@fs.com.

Source:http://www.china-cable-suppliers.com/basic-things-know-pm-patch-cables.html

Posted in Article, Networking

Do You Know the Difference Between Hub, Switch & Router?

When computers, network devices or other networks are required to be connected, hubs, switches and routers are the bridges to link them together. All the three types of devices can perform the same function, and technicians sometimes may use the terms interchangeably. However, this will make people confuse whether they are the same thing or different from each other. This post is going to explore the actual meanings of hub, switch, router and what they are used for.

Overview of Hub, Switch & Router
Hub

A hub is to sent out a message from one port to other ports. For example, if there are three computers of A, B, C, the message sent by a hub for computer A will also come to the other computers. But only computer A will respond and the response will also go out to every other port on the hub. Therefore, all the computers can receive the message and computers themselves need to decide whether to accept the message.

hub network

Switch

A switch is able to handle the data and knows the specific addresses to send the message. It can decide which computer is the message intended for and send the message directly to the right computer. The efficiency of switch has been greatly improved, thus providing a faster network speed.

switch network

Router

Router is actually a small computer that can be programmed to handle and route the network traffic. It usually connects at least two networks together, such as two LANs, two WANs or a LAN and its ISP network. Routers can calculate the best route for sending data and communicate with each other by protocols.

router network

What Is the Difference?
Hub Vs. Switch

A hub works on the physical layer (Layer 1) of OSI model while Switch works on the data link layer (Layer 2). Switch is more efficient than the hub. A switch can join multiple computers within one LAN, and a hub just connects multiple Ethernet devices together as a single segment. Switch is smarter than hub to determine the target of the forwarding data. Since switch has a higher performance, its cost will also become more expensive.

Switch Vs. Router

In the OSI model, router is working on a higher level of network layer (Layer 3) than switch. Router is very different from the switch because it is for routing packet to other networks. It is also more intelligent and sophisticated to serve as an intermediate destination to connect multiple area networks together. A switch is only used for wired network, yet a router can also link with the wireless network. With much more functions, a router definitely costs higher than a switch.

Hub Vs. Router

As mentioned above, a hub only contains the basic function of a switch. Hence, differences between hub and router are even bigger. For instance, hub is a passive device without software while router is a networking device, and data transmission form in hub is in electrical signal or bits while in router it is in form of packet.

Which One Should I Buy?

Whatever device you use for your network, you must make sure it can perform all the functions required by the network. As for performance, wireless router is recommended because it allows different devices to connect to the network. If you have a limited budget, switch is a good solution with relatively high performance and lower cost.

Conclusion

Although sometimes specialists alternatively use hub, switch or router to describe these devices, they still have their own differences. Understanding their distinctions can be helpful to find the most appropriate device for your network.

Source:http://www.fiber-optic-cable-sale.com/know-difference-hub-switch-router.html

Posted in Article, WDM System

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.

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 support 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 side 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.

ports on WDM mux demux

Conclusion

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.

source:http://www.fiber-optical-networking.com/different-ports-wdm-muxdemux.html

Posted in Article, Networking

How Will SDN Change the Future Network?

Traditional networks are usually built with tiers of Ethernet switches in a tree structure. However, the development of mobile devices, server virtualization and cloud computing service has driven the need for dynamic computing and storage in data centers. Thus, the concept of software-defined networking (SDN) was put forward to construct a more flexible and agile network. This technology has widely caught people’s attention in the industry over the years. In this post, some basic knowledge about SDN will be introduced to help you have better understanding.

Definition of SDN Architecture

SDN is a developing network architecture that aims to directly program the network computing. Through the open interfaces and abstraction of lower-level functionality, this approach allows the network administrators to programmatically initialize, control, change and manage network behavior dynamically. SDN is different from the traditional network architecture whose network devices are based on both control plane and data plane. Instead, SDN puts the control plane on the SDN controller to communicate with a physical or virtual switch data plane through the OpenFlow protocol.

sdn-architecture

Features of SDN

Here are some fundamental features of the SDN architecture:

  • Instantly programmable: Network control is directly programmable for it is decoupled from forwarding functions.
  • Agile: Administrators can dynamically adjust network-wide traffic flow to meet changing needs.
  • Centralized management: Network intelligence is centralized in SDN controllers that maintain a global view of the network.
  • Programmatically configured: Network managers can configure, manage, secure, and optimize network resources very quickly by dynamic, automated SDN programs.
  • Open standards-based and vendor-neutral: SDN simplifies network design and operation since instructions are provided by SDN controllers instead of multiple, vendor-specific devices and protocols.
Basics of OpenFlow

OpenFlow is a type of communication protocol that provides access to the forwarding plane of a network switch or router over the network. It is considered to be the first SDN standard, which enables network controllers to determine the path of network packets across a network of switches. In order to work in an OpenFlow environment, all the equipment should support the OpenFlow protocol to communicate to an SDN controller.

openflow

What Benefits Will OpenFlow-Based SDN Bring to Network?
  • Point 1, SDN controller can get centralized control of OpenFlow-enabled devices from any vendors instead of managing the devices from different vendors separately.
  • Point 2, OpenFlow-based SDN provides a flexible network automation and management architecture, and can develop a variety of automated network management tools to replace the current manual operation which greatly reduces the complexity.
  • Point 3, SDN increases higher rates of business innovation and allows IT network operators to meet specific business needs and variable user needs in real time by explicitly programming or reprogramming the network.
  • Point 4, SDN enables IT to define the configuration network and develop management policies at a higher level and distributes the information to the network infrastructure through OpenFlow, which has increased the network reliability and security.
  • Point 5, OpenFlow’s flow control model allows IT to deploy network policies at a granular level which is a higher abstraction and automated deployment level including session-level, user-level, device-level and application-level.
  • Point 6, through centralized network control and network application status information, SDN can provide better dynamic user experience.
Conclusion

Future network will depend on more and more software to accelerate the pace of network innovation. SDN is committed to changing the current static network into a dynamic and programmable one. With so many advantages and industrial potentiality, SDN will definitely become the new standard of future network.

Source:http://www.fiber-optic-cable-sale.com/will-sdn-change-future-network.html