Most Popular Articles

• Introduction to Bi-Directional Transceiver Modules

  Feb 7, 2016 by Articles / 440 Views

  Almost all modern optical transceivers utilize two fibers to transmit data between switches, firewalls, servers, routers, etc. The first fiber is dedicated to receiving data from networking equipment, and the second fiber is dedicating to transmitting data to the networking equipment. But there is a type of fiber optic transceiver module called BiDi (Bi-Directional) transceiver to break this rule. What's BiDi transceiver? How does it work? And why people believe it will have broad market prospect? This tutorial will give you the answer.

  What's BiDi Transceiver?

  BiDi transceiver is a type of fiber optic transceivers which is used WDM (Wavelength Division Multiplexing) Bi-directional transmission technology so that it can achieve the transmission of optical channels on a fiber propagating simultaneously in both directions. BiDi transceiver is only with one port which uses an integral bidirectional coupler to transmit and receive signals over a single fiber optical cable. Thus, it must be used in pairs.

  How Does BiDi Transceiver Work

  The primary difference between BiDi transceivers and traditional two-fiber fiber optic transceivers is that BiDi transceivers are fitted with Wavelength Division Multiplexing (WDM) couplers, also known as diplexers, which combine and separate data transmitted over a single fiber based on the wavelengths of the light. For this reason, BiDi transceivers are also referred to as WDM transceivers.

  To work effectively, BiDi transceivers must be deployed in matched pairs, with their diplexers tuned to match the expected wavelength of the transmitter and receiver that they will be transmitting data from or to.

  For example, if paired BiDi transceivers are being used to connect Device A (Upstream) and Device B (Downstream), as shown in the figure below, then:

  Transceiver A's diplexer must have a receiving wavelength of 1550nm and a transmit wavelength of 1310nmTransceiver B's diplexer must have a receiving wavelength of 1310nm and a transmit wavelength of 1550nm

  

  Advantages of BiDi Transceivers

  The obvious advantage of utilizing BiDi transceivers, such as SFP+- BiDi and SFP-BiDi transceivers, is the reduction in fiber cabling infrastructure costs by reducing the number of fiber patch panel ports, reducing the amount of tray space dedicated to fiber management, and requiring less fiber cable.

  While BiDi transceivers (a.k.a. WDM transceivers) cost more to initially purchase than traditional two-fiber transceivers, they utilize half the amount of fiber per unit of distance. For many networks, the cost savings of utilizing less fiber is enough to more than offset the higher purchase price of BiDi transceivers.

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• COMPUFOX SFP+ Direct Attach Copper Cables Solution

  Feb 27, 2016 by Articles / 439 Views

  Overview
  SFP+ Direct Attach Copper Cable, also known as Twinax Cable, is an SFP+ cable assembly used in rack connections between servers and switches. It consists of a high speed copper cable and two SFP+ copper modules. The SFP+ copper modules allow hardware manufactures to achieve high port density, configurability and utilization at a very low cost and reduced power budget.

  Direct Attach Cable assemblies are a high speed, cost-effective alternative to fiber optic cables in 10Gb Ethernet, 8Gb Fibre Channel and InfiniBand applications. They are suitable for short distances, making them ideal for highly cost-effective networking connectivity within a rack and between adjacent racks. They enable hardware OEMs and data center operators to achieve high port density and configurability at a low cost and reduced power requirement.

  Compufox SFP+ copper cable assemblies meet the industry MSA for signal integrity performance. The cables are hot-removable and hot-insertable: You can remove and replace them without powering off the switch or disrupting switch functions. A cable comprises a low-voltage cable assembly that connects directly into two SFP+ ports, one at each end of the cable. The cables use high-performance integrated duplex serial data links for bidirectional communication and are designed for data rates of up to 10 Gbps.

  Types of SFP+ Direct Attach Copper Cables

  SFP+ Direct Attach Copper Cable assemblies generally have two types which are Passive and Active versions.
  
  

  SFP+ Passive Copper Cable
  SFP+ passive copper cable assemblies offer high-speed connectivity between active equipment with SFP+ ports. The passive assemblies are compatible with hubs, switches, routers, servers, and network interface cards (NICs) from leading electronics manufacturers like Cisco, Juniper, etc.

   

  SFP+ Active Copper Cable
  SFP+ active copper cable assemblies contain low power circuitry in the connector to boost the signal and are driven from the port without additional power requirements. The active version provides a low cost alternative to optical transceivers, and are generally used for end of row or middle of row data center architectures for interconnect distances of up to 15 meters.

   

  Applications of SFP+ Direct Attach Copper Cables

  -Networking – servers, routers and hubs

  -Enterprise storage

  -Telecommunication equipment

  -Network Interface Cards (NICs)

  -10Gb Ethernet and Gigabit Ethernet (IEEE802.3ae)

  -Fibre Channel over Ethernet: 1, 2, 4 and 8G

  -InfiniBand standard SDR (2.5Gbps), DDR (5Gbps), and QDR (10Gbps)

  -Serial data transmission

  -High capacity I/O in Storage Area Networks, Network Attached Storage, and Storage Servers

  -Switched fabric I/O such as ultra high bandwidth switches and routers

  -Data center cabling infrastructure

  -High density connections between networking equipment

   

  Compufox SFP+ Direct Attach Copper Cables Solution

  Compufox SFP+ twinax copper cables are avaliable with custom version and brand compatible version. All of them are 100% compatible with major brands like Cisco, HP, Juniper, Enterasys, Extreme, H3C and so on. If you want to order high quality compatible SFP+ cables and get worldwide delivery, we are your best choice.

  For instance, our compatible Cisco SFP+ Copper Twinax direct-attach cables are suitable for very short distances and offer a cost-effective way to connect within racks and across adjacent racks. We can provide both passive Twinax cables in lengths of 1, 3 and 5 meters, and active Twinax cables in lengths of 7 and 10 meters. (Tips: The lengths can be customized up to the customers' requirements.)

  Features
  -1m/3m/5m/7m/10m/12m available

  -RoHS Compatible

  -Enhanced EMI suppression

  -Low power consumption

  -Compatible to SFP+ MSA

  -Hot-pluggable SFP 20PIN footprint

  -Parallel pair cable

  -24AWG through 30AWG cable available

  -Data rates backward compatible to 1Gbps

  -Support serial multi-gigabit data rates up to 10Gbps

  -Support for 1x, 2x, 4x and 8x Fibre Channel data rates

  -Low cost alternative to fiber optic cable assemblies

  -Pull-to-release retractable pin latch

  -I/O Connector designed for high speed differential signal applications

  -Temperature Range: 0-70°C

  -Passive and Active assemblies available (Active Version: Low Power Consumption: < 0.5W Power Supply: +3.3V)

   

  FAQ of Compufox SFP+ Direct Attach Copper Cables

  Q: What are the performance requirements for the cable assembly?
  A: Our SFP+ copper passive and active cable assemblies meet the signal integrity requirements defined by the industry MSA SFF-8431. We can custom engineer cable assemblies to meet the requirements of a customer’s specific system architecture.

  Q: Are passive or active cable assemblies required?
  A: Passive cables have no signal amplification in the assembly and rely on host system Electronic Dispersion Compensation (EDC) for signal amplification/equalization. Active cable assemblies have signal amplification and equalization built into the assembly. Active cable assemblies are typically used in host systems that do not employ EDC. This solution can be a cost savings to the customer.

  Q: What wire gauge is required?
  A: We offer SFP+ cable assemblies in wire gauges to support customers' specific cable routing requirements. Smaller wire gauges results in reduced weight, improved airflow and a more flexible cable for ease of routing.

  Q: What cable lengths are required?
  A: Cable length and wire gauge are related to the performance characteristics of the cable assembly. Longer cable lengths require heavier wire gauge, while shorter cable lengths can utilize a smaller gauge cable.

  For all you SFP+ Direct attach cables, please see link below. We carry compatible cables for most major brands.

  http://www.compufox.com/SFP_Cables_s/337.htm

      

  

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• Basics of Fiber Optic Splicing

  Feb 26, 2016 by Articles / 437 Views

  Fiber Optics Splicing is becoming  more and more a common skill requirement for cabling technicians. A fiber optic splice is defined by the fact that it gives a permanent or relatively permanent connection between two fiber optic cables. Fiber optic cables might have to be spliced together for a number of reasons—for example, to create a link of a particular length, or to repair a broken cable or connection. As fiber optic cables are generally only manufactured in lengths up to about 5 km, when lengths of 10 km are required, for example, then it is necessary to splice two lengths together to make a permanent connection.

  Classification of Techniques Used for Optical Fiber Splicing

  Mechanical splices

  The mechanical splices are normally used when splices need to be made quickly and easily. Mechanical fiber optic splices can take as little as five minutes to make, although the level of light loss is around ten percent. However this level of better than that which can be obtained using a connector. Some of the sleeves for mechanical fibre optic splices are advertised as allowing connection and disconnection. In this way a mechanical splice may be used in applications where the splice may be less permanent.

   

  Fusion splices

  This type of connection is made by fusing or melting the two ends together. This type of splice uses an electric arc to weld two fiber optic cables together and it requires specialised equipment to perform the splice. Fusion splices offer a lower level of loss and a high degree of permanence. However they require the use of the expensive fusion splicing equipment.
  
  

  Mechanisms of Light Loss at Optical Fiber Joint

  When joining optical fibers, the opposed cores must be properly aligned. Optical fiber splice loss occurs mostly in the following manner.

  Poor concentricity

  Poor concentricity of joined optical fibers causes a splice loss. In the case of general purpose single-mode fibers, the value of splice loss is calculated roughly as the square of the amount of misalignment multiplied by 0.2. (For example, if the light source wavelength is 1310 nm, misalignment by 1 µm results in approximately 0.2 dB of loss.)
  
  

  

  Axial run-out

  A splice loss occurs due to an axial run-out between the light axes of optical fibers to be joined. For example, it is necessary to avoid an increased angle at fiber cut end when using an optical fiber cleaver before fusion splicing, since such an angle can result in splicing of optical fibers with run-out.
  

  
  

  Gap

  An end gap between optical fibers causes a splice loss. For example, if optical fiber end faces are not correctly butt-joined in mechanical splicing, a splice loss.
   

  

  Reflection

  An end gap between optical fibers results in 0.6 dB of return loss at the maximum due to the change in refractive index from the optical fiber to the air. In addition, the whole optical fiber ends should be cleaned because loss can also occur due to dirt between optical fiber ends.

  
  

  Classification and Principles of Fusion Splices

  Fusion splicing is classified into the two methods, as follows:

  
  Core alignment

  Optical fiber cores observed with a microscope are positioned with the help of image processing so that they are concentrically aligned. Then, an electric arc is applied to the fiber cores. The fusion splicer used has cameras for observation and positioning in two directions.

  

  Stationary V-groove alignment

  This fusion splicing method uses V-grooves produced with high precision to position and orient optical fibers and utilizes the surface tension of melted optical fibers for alignment effects (cladding alignment). Splices made by this method achieve low loss thanks to the recent advancement of optical fiber production technology, which has improved the dimensional accuracy regarding the placement of core. This method is primarily used for splicing a multi-fiber cable in a single action.

  
   

  Tips for Better Splices:

  1. Thoroughly and frequently clean your splicing tools. When working with fiber, keep in mind that particles not visible to the naked eye could cause tremendous problems when working with fiber optics. "Excessive" cleaning of your fiber and tools will save you time and money down the road.

   

  2. Properly maintain and operate your cleaver. The cleaver is your most valuable tool in fiber splicing. Within mechanical splicing you need the proper angle to insure proper end faces or too much light escaping into the air gaps between the two fibers will occur. The index matching gel will eliminate most of the light escape but cannot overcome a low quality cleave. You should expect to spend around $200 to $1,000 for a good quality cleaver suitable for mechanical splicing.

   

  For Fusion splicing, you need an even more precise cleaver to achieve the exceptional low loss (0.05 dB and less). If you have a poor cleave the fiber ends might not melt together properly causing light loss and high reflection problems. Expect to pay $1,000 to $4,000 for a good cleaver to handle the precision required for fusion splicing. Maintaining your cleaver by following manufacturer instructions for cleaning as well as using the tool properly will provide you with a long lasting piece of equipment and ensuring the job is done right the first time.

   

  3. Fusion parameters must be adjusted minimally and methodically (fusion splicing only). If you start changing the fusion parameters on the splicer as soon as there is a hint of a problem you might lose your desired setting. Dirty equipment should be your first check and them continue with the parameters. Fusion time and fusion current are the two key factors for splicing. Different variables of these two factors can produce the same splice results. High time and low current result in the same outcome as high current and low time. Make sure to change one variable at a time and keep checking until you have found the right fusion parameters for your fiber type.

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• Polarity and MPO Technology in 40/100GbE Transmission

  Feb 5, 2016 by Articles / 419 Views

  It have been proved that reducing cable diameters and increasing connection densities offered by fiber links would be extremely valuable during installation in constrained space, like data center, large enterprise equipment rooms, central office, etc. With the market turning to 40/100G transmission, to reduce congestion during cabling and make it easier to organize equipment cable runs, the network designers turns to MPO/MTP technology and components for today's duplex fiber transmission. Then, network designers face another challenge which is how to assure the proper polarity of these array connections using MPO/MTP components from end-to-end.

  Traditionally, a fiber optic link requires two fibers for full duplex communications. It is very important to ensure that the equipment on the link are connected properly at each end. However, when the link contains two or more fibers, maintain the correct polarity across a fiber network become more complex, especially when using multi-fiber MPO components for high data rate transmission. Luckily, pre-terminated MPO components adopt humanized design for polarity maintenance and the TIA 568 standard provides three methods for configuring systems to ensure that proper connections are made. This article will introduce polarity in MPO system and 40/100GbE polarization connectivity solutions in details.

  Polarity in MPO Components

  To maintain the correct polarity in MPO systems, the property of the components of MPO systems should be understood firstly. This part will introduce the basic components that are used in MPO system.

  MPO Connector: To understand the polarity in 40/100 GbE transmission, the key of MPO technology—MPO connector should be first introduced. MPO connector usually has 12 fibers. 24 fibers, 36 fibers and 72 fibers are also available. Each MTP connector has a key on one of the flat side added by the body. When the key sits on the bottom, this is called key down. When the key sits on the top, this is referred to as the key up position. In this orientation, each of the fiber holes in the connector is numbered in sequence from left to right and is referred as fiber position, or P1, P2, etc. A white dot is additionally marked on one side of the connector to denote where the position 1 is. (shown in the following picture) The orientation of this key also determines the MTP cable's polarity.

  

   

  MPO Adapter: MPO (male) connectors are mated to MPO(female) connectors using a MPO adapter. As each MPO connector has a key, there are 2 types of MPO adapters:

  Type A—key-up to key-down. Here the key is up on one side and down on the other. The two connectors are connected turned 180° in relation to each other.Type B—key-up to key-up. Here both keys are up. The two connectors are connected while in the same position in relation to each other.

   

  

   

  MPO Cables: MPO trunk cable with two MPO connectors (male/female) on both side of the cable serves as a permanent link connecting the MPO modules to each other, which is available with 12, 24, 48, 72 fibers.

  MPO harness cable, which is terminated with a male/female connector on the MPO side and several duplex LC/SC connectors on the other side, provides a transition from multi-fiber cables to individual fibers or duplex connectors.

  MPO Cassette: Modular MPO cassette is enclosed unit that usually contains 12 or 24-fiber factory terminated fan-outs inside. It enables the user to take the fibers brought by a trunk cable and distribute them to a duplex cable with a MPO connector (at the rear) to the more common LC or SC interface (on the front side). The following is a MTP cassette with 6 duplex LC interface and a MTP connector.

  

  Three Cables for Three Polarization Methods

  The three methods for proper polarity defined by TIA 568 standard are named as Method A, Method B and Method C. To match these standards, three type of MPO truck cables with different structures named Type A, Type B and Type C are being used for the three different connectivity methods respectively. In this part, the three different cables will be introduced firstly and then the three connectivity methods.

  MPO Trunk Cable Type A: Type A cable also known as straight cable, is a straight through cable with a key up MPO connector on one end and a key down MPO connector on the opposite end. This makes the fibers at each end of the cable have the same fiber position. For example, the fiber located at position 1 (P1) of the connector on one side will arrive at P1 at the other connector. The fiber sequence of a 12 fiber MPO Type A cable is showed as the following:

  

  MPO Trunk Cable Type B: Type B cable (reversed cable) uses key up connector on both ends of the cable. This type of array mating results in an inversion, which means the fiber positions are reversed at each end. The fiber at P1 at one end is mated with fiber at P12 at the opposing end. The following picture shows the fiber sequences of a 12 fiber Type B cable.

  

  MPO Trunk Cable Type C: Type C cable (pairs flipped cable) looks like Type A cable with one key up connector and one key down connector on each side. However, in Type C each adjacent pair of fibers at one end are flipped at the other end. For example, the fiber at position 1 on one end is shifted to position 2 at the other end of the cable. The fiber at position 2 at one end is shifted to position 1 at the opposite end etc. The fiber sequence of Type C cable is demonstrated in the following picture.

  

  Three Connectivity Methods

  Different polarity methods use different types of MTP trunk cables. However, all the methods should use duplex patch cable to achieve the fiber circuit. The TIA standard also defines two types of duplex fiber patch cables terminated with LC or SC connectors to complete an end-to-end fiber duplex connection: A-to-A type patch cable—a cross version and A-to-B type patch cable—a straight-through version.

  

  The following part illustrates how the components in MPO system are used together to maintain the proper polarization connectivity, which are defined by TIA standards.

  Method A: the connectivity Method A is shown in the following picture. A type-A trunk cable connects a MPO module on each side of the link. In Method A, two types of patch cords are used to correct the polarity. The patch cable on the left is standard duplex A-to-B type, while on the right a duplex A-to-A type patch cable is employed.

  

  Method B: in Connectivity Method B, a Type B truck cable is used to connect the two modules on each side of the link. As mentioned, the fiber positions of Type B cable are reversed at each end. Therefore standard A-to-B type duplex patch cables are used on both sided.

  

  Method C: the pair-reversed trunk cable is used in Method C connectivity to connect the MPO modules one each side of the link. Patch cords at both ends are the standard duplex A-to-B type.

  

  Upgrade to 40/100GbE With Correct Polarity

  The using of MPO/MTP connectors for 40/100G transmission is achieved with multimode fiber by transmitting multiple parallel 10G transmissions that will then be recombined when received. This method has been standardized. The following is to offer 40G transmission solution and 100G respectively.

  40G Transmission Connectivity

  The 40G transmission usually uses 12-fiber MPO/MTP connectors. There are eight lanes within twelve total positions being employed for transmitting and receiving signals. Looking at the end face of the MPO/MTP connector with the key on top, the four leftmost positions are used to transmit, the four rightmost positions are used to receive, the four in the center are unused. The following picture shows the optical lane assignments. (Tx stands for Transmit, Rx stands for Receive) This approach would transmit 40G using for parallel 10G lanes in each direction according to 40GBase-SR4.

  

  100G Transmission Connectivity

  The 100G transmission over multimode requires a total of 20 fibers, 10 for transmitting and 10 for receiving. There are three options which is introduced as following:

  The first method is to use a 24-fiber MPO/MTP connector with the top center 10 positions allocated for receiving and the bottom 10 position allocated for transmitting,as shown in the following figure. This method is recommended by IEEE.

  

  The second option is to use two 12-fiber MPO/MTP connectors side by side. The 10 positions in the center of the connector on the left are used for transmitting and the center 10 positions of the left are used for receiving.

  

  The third way of 100G transmission also uses two 12-fiber MPO/MTP connectors, but it uses the stacked layout as showed in the following figure. The ten center positions of the top connector are used for receiving and the ten center position of the bottom are used for transmitting.

  

  Understand Polarity in 40/100G

  Any transmit position should be connected to its own receive position. Here's an analogy to illustrate: Think of ball players. You have pitchers & catchers. For 10G transmission, Pitcher 1 needs to throw to Catcher 1, Pitcher 2 to Catcher 2 and so on. (showed on the left side of the following picture) For 40/100G, any pitcher can throw to any catcher.(showed on the right side of the following picture)

  

  But if you've got two catchers looking at each other as showed in the following picture, there isn't a whole lot happening.

  

  Conclusion

  Network designer using MPO/MTP components to satisfy the increasing requirement for higher transmission speed, during which one of the big problems—polarity, can be solved by selecting the right types of MPO cables, MPO connectors, MPO cassette and patch cables. Consider the polarity method to be used and selecting the correct MPO/MTP components to support that methods, the proper solution for 40/100G transmission would be achieved with high density and flexibility and reliability.

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• T-Mobile becomes number one US smartphone channel

  May 31, 2016 by Telecom News / 418 Views

  Written by Scott Bicheno  Telecoms.com

  

  Disruptive US operator T-Mobile has become the leading sales channel for smartphones in the US, according to new research from Counterpoint.

  T-Mobile overtook Verizon to take the number one smartphone sales spot, having been a distant fourth just two years ago. This change is viewed as indicative of a broader change in the way smartphones are being purchased in the US, with the cost of devices increasingly uncoupled from the service contracts and, if needed, paid for via conventional financing arrangements.

  “The US market has undergone significant shifts in the power of the different sales channels with the move to unsubsidized plans,” said Neil Shah of Counterpoint. “The growth of T-Mobile through its different ‘Uncarrier’ moves, the removal of subsidies and enticing subscribers with ‘Simple Choice’ & ‘Jump’ plans, has helped the operator to become the top smartphone sales channel in the USA.

  Samsung and Apple together captured almost two-thirds of the total smartphone shipments share at T-Mobile, with Samsung leading. However, it will be an uphill task for T-Mobile to maintain this lead ahead of Verizon and continue to attract millions of subscribers to its network. The move to unsubsidized and unlocked has also boosted demand in the open channel, which continued to contribute close to 10% of the total shipments in Q1 2016.”

  

  US smartphone sales on the whole declined by 4% year-on-year due to the maturity of the market (most people already have a smartphone) and a lengthening on the upgrade cycle. The latter factor will be a direct result of the shift in buying habits as fewer consumers are being prompted to upgrade their subsidized phones by the renewal of their postpaid contracts.

  “The US market decelerated due to softness in Apple iPhone demand and iPhone SE demand not materializing until Q2 2016,” said Jeff Fieldhack of Counterpoint. “Carriers continued to push subscribers to non-subsidy plans as for the first time more than half of the combined subscriber base of the top four carriers are now on non-subsidized plans. This is a significant shift from the subsidy-driven model just ten to twelve quarters ago. This has changed the basis of competition in US mobile landscape.

  “The focus has shifted to creating more value for the consumer, instead of being device-driven. Unsubsidized device sales have educated consumers that flagship smartphones are costly. This has led to a temporary softness in the device upgrade cycle; the in-carrier upgrade run rate continues to be in 5-6% range per quarter. Handset manufacturers will continue to push hardware and marketing limits to entice subscribers to not defer upgrading.”

   

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