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  • Polarization-Maintaining Fiber Tutorial

    Introduction to Polarization

    As light passes through a point in space, the direction and amplitude of the vibrating electric field traces out a path in time. A polarized lightwave signal is represented by electric and magnetic field vectors that lie at right angles to one another in a transverse plane (a plane perpendicular to the direction of travel). Polarization is defined in terms of the pattern traced out in the transverse plane by the electric field vector as a function of time.

    Polarization can be classified as linear, elliptical or circular, in them the linear polarization is the simplest. Whichever polarization can be a problem in the fiber optic transmission.

    FiberStore Polarization Coordinate System

    More and more telecommunication and fiber optic measuring systems refer to devices that analyse the interference of two optical waves. The information given by the interferences cannot be used unless the combined amplitude is stable in time, which means, that the waves are in the same state of polarization. In those cases it is necessary to use fibers that transmit a stable state of polarization. And polarization-maintaining fiber was developed to this problem. (The polarization-maintaining fiber will be called PM fiber for short in the following contents.)

     

    What Is PM Fiber?

    The polarization of light propagating in the fiber gradually changes in an uncontrolled (and wavelength-dependent) way, which also depends on any bending of the fiber and on its temperature. Specialised fibers are required to achieve optical performances, which are affected by the polarization of the light travelling through the fiber. Many systems such as fiber interferometers and sensors, fiber laser and electro-optic modulators, also suffer from Polarization-Dependent Loss (PDL) that can affect system performance. This problem can be fixed by using a specialty fiber so called PM Fiber.

     

    Principle of PM Fiber

    Provided that the polarization of light launched into the fiber is aligned with one of the birefringent axes, this polarization state will be preserved even if the fiber is bent. The physical principle behind this can be understood in terms of coherent mode coupling. The propagation constants of the two polarization modes are different due to the strong birefringence, so that the relative phase of such copropagating modes rapidly drifts away. Therefore, any disturbance along the fiber can effectively couple both modes only if it has a significant spatial Fourier component with a wavenumber which matches the difference of the propagation constants of the two polarization modes. If this difference is large enough, the usual disturbances in the fiber are too slowly varying to do effective mode coupling. Therefore, the principle of PM fiber is to make the difference large enough.

    In the most common optical fiber telecommunications applications, PM fiber is used to guide light in a linearly polarised state from one place to another. To achieve this result, several conditions must be met. Input light must be highly polarised to avoid launching both slow and fast axis modes, a condition in which the output polarization state is unpredictable.

    The electric field of the input light must be accurately aligned with a principal axis (the slow axis by industry convention) of the fiber for the same reason. If the PM fiber path cable consists of segments of fiber joined by fiber optic connectors or splices, rotational alignment of the mating fibers is critical. In addition, connectors must have been installed on the PM fibers in such a way that internal stresses do not cause the electric field to be projected onto the unintended axis of the fiber.

     

    Types of PM Fibers

    Circular PM Fibers

    It is possible to introduce circular-birefringence in a fiber so that the two orthogonally polarized modes of the fiber—the so called Circular PM fiber—are clockwise and counter-clockwise circularly polarized. The most common way to achieve circular-birefringence in a round (axially symmetrical) fiber is to twist it to produce a difference between the propagation constants of the clockwise and counterclockwise circularly polarized fundamental modes. Thus, these two circular polarization modes are decoupled. Also, it is possible to conceive externally applied stress whose direction varies azimuthally along the fiber length causing circular-birefringence in the fiber. If a fiber is twisted, a torsional stress is introduced and leads to optical-activity in proportion to the twist.

    Circular-birefringence can also be obtained by making the core of a fiber follows a helical path inside the cladding. This makes the propagating light, constrained to move along a helical path, experience an optical rotation. The birefringence achieved is only due to geometrical effects. Such fibers can operate as a single mode, and suffer high losses at high order modes.

    Circular PM fiber with Helical-core finds applications in sensing electric current through Faraday effect. The fibers have been fabricated from composite rod and tube preforms, where the helix is formed by spinning the preform during the fiber drawing process.

     

    Linear PM Fibers

    There are manily two types of linear PM fibers which are single-polarization type and birefringent fiber type. The single-polarization type is characterized by a large transmission loss difference between the two polarizations of the fundamental mode. And the birefringent fiber type is such that the propagation constants between the two polarizations of the fundamental mode are significantly different. Linear polarization may be maintained using various fiber designs which are reviewed next.

    Linear PM Fibers With Side Pits and Side Tunnels

    Side-pit fibers incorporate two pits of refractive index less than the cladding index, on each side of the central core. This type of fiber has a W-type index profile along the x-axis and a step-index profile along the y-axis. A side-tunnel fiber is a special case of side-pit structure. In these linear PM fibers, a geometrical anisotropy is introduced in the core to obtain a birefringent fibers.

     

    Linear PM Fibers With Stress Applied Parts

    An effective method of introducing high birefringence in optical fibers is through introducing an asymmetric stress with two-fold geometrical symmetry in the core of the fiber. The stress changes the refractive index of the core due to photoelastic effect, seen by the modes polarized along the principal axes of the fiber, and results in birefringence. The required stress is obtained by introducing two identical and isolated Stress Applied Parts (SAPs), positioned in the cladding region on opposite sides of the core. Therefore, no spurious mode is propagated through the SAPs, as long as the refractive index of the SAPs is less than or equal to that of the cladding.

    The most common shapes used for the SAPs are: bow-tie shape and circular shape. These fibers are respectively referred to as Bow-tie Fiber and PANDA Fiber. The cross sections of these two types of fibers are shown in the figure below. The modal birefringence introduced by these fibers represents both geometrical and stress-induced birefringences. In the case of a circular-core fiber, the geometrical birefringence is negligibly small. It has been shown that placing the SAPs close to the core improves the birefringence of these fibers, but they must be placed sufficiently close to the core so that the fiber loss is not increased especially that SAPs are doped with materials other than silica. The PANDA fiber has been improved further to achieve high modal birefringence, very low-loss and low cross-talk.

    PANDA Fiber and Bow-tie Fiber

    PANDA Fiber (left) and Bow-tie Fiber (right). The built-in stress elements made from a different type of glass are shown with a darker gray tone.

    Tips: At present the most popular PM fiber in the industry is the circular PANDA fiber. One advantage of PANDA fiber over most other PM fibers is that the fiber core size and numerical aperture is compatible with regular single mode fiber. This ensures minimum losses in devices using both types of fibers.

     

    Linear PM Fibers With Elliptical Structures

    The first proposal on practical low-loss single-polarization fiber was experimentally studied for three fiber structures: elliptical core, elliptical clad, and elliptical jacket fibers. Early research on elliptical-core fibers dealt with the computation of the polarization birefringence. In the first stage, propagation characteristics of rectangular dielectric waveguides were used to estimate birefringence of elliptical-core fibers. In the first experiment with PM fiber, a fiber having a dumbbell-shaped core was fabricated. The beat length can be reduced by increasing the core-cladding refractive index difference. However, the index difference cannot be increased too much due to practical limitations. Increasing the index difference increases the transmission loss, and splicing would become difficult because the core radius must be reduced. Typical values of birefringence for the elliptical core fiber are higher than elliptical clad fiber. However, losses were higher in the elliptical core than losses in the elliptical clad fibers.

     

    Linear PM Fibers With Refractive Index Modulation

    One way to increase the bandwidth of single-polarization fiber, which separates the cutoff wavelength of the two orthogonal fundamental modes, is by selecting a refractive-index profile which allows only one polarization state to be in cutoff. High birefringence was achieved by introducing an azimuthal modulation of the refractive index of the inner cladding in a three-layer elliptical fiber. A perturbation approach was employed to analyze the three-layer elliptical fiber, assuming a rectangular-core waveguide as the reference structure. Examination of birefringence in three-layer elliptical fibers demonstrated that a proper azimuthal modulation of the inner cladding index can increase the birefringence and extend the wavelength range for single-polarization operation.

    A refractive index profile is called Butterfly profile. It is an asymmetric W profile, consisting of a uniform core, surrounded by a cladding in which the profile has a maximum value of ncl and varies both radially and azimuthally, with maximum depression along the x-axis. This profile has two attributes to realize a single-mode single-polarization operation. First, the profile is not symmetric, which makes the propagation constants of the two orthogonal fundamental modes dissimilar, and secondly, the depression within the cladding ensures that each mode has a cutoff wavelength. The butterfly fiber is weakly guiding, thus modal fields and propagation constants can be determined from solutions of the scalar wave equation. The solutions involve trigonometric and Mathieu functions describing the transverse coordinates dependence in the core and cladding of the fiber. These functions are not orthogonal to one another which requires an infinite set of each to describe the modal fields in the different regions and satisfy the boundary conditions. The geometrical birefringence plots generated vs. the normalized frequency V showed that increasing the asymmetry through the depth of the refractive index depression along the x-axis increases the maximum value of the birefringence and the value of V at which this occurs. The peak value of birefringence is a characteristic of noncircular fibers. The modal birefringence can be increased by introducing anisotropy in the fiber which can be described by attributing different refractive-index profiles to the two polarizations of a mode. The geometric birefringence is smaller than the anisptropic birefringence. However, the depression in the cladding of the butterfly profile gives the two polarizations of fundamental mode cutoff wavelengths, which are separated by a wavelength window in which single-polarization single-mode operation is possible.

     

    Applications of PM Fibers

    PM fibers are applied in devices where the polarization state cannot be allowed to drift, e.g. as a result of temperature changes. Examples are fiber interferometers and certain fiber lasers. A disadvantage of using such fibers is that usually an exact alignment of the polarization direction is required, which makes production more cumbersome. Also, propagation losses are higher than for standard fiber, and not all kinds of fibers are easily obtained in polarization-preserving form.

    PM fibers are used in special applications, such as in fiber optic sensing, interferometry and quantum key distribution. They are also commonly used in telecommunications for the connection between a source laser and a modulator, since the modulator requires polarized light as input. They are rarely used for long-distance transmission, because PM fiber is expensive and has higher attenuation than single mode fiber.

     

    Requirments for Using PM Fibers

    Termination: When PM fibers are terminated with fiber connectors, it is very important that the stress rods line up with the connector, usually in line with the connector key.

    Splicing: PM fiber also requires a great deal of care when it is spliced. Not only the X, Y and Z alignment have to be perfect when the fiber is melted together, the rotational alignment must also be perfect, so that the stress rods align exactly.

    Another requirement is that the launch conditions at the optical fiber end face must be consistent with the direction of the transverse major axis of the fiber cross section.

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  • How to Install or Remove SFP Transceiver Modules on Cisco Device

    The SFP (small form Factor pluggables) transceiver modules are hot-pluggable I/O devices that plug into module sockets. The transceiver connects the electrical circuitry of the module with the optical or copper network. SFP transceiver modules are the key components in today's transmission network. Thus, it is necessary to master the skill of installing or removing a transceiver modules to avoid unnecessary loss. This tutorial are going to guide you how to install or remove SFP transceiver module in a right way.

     

    Things you should Know Before Installing or Removing SFP

    Before removing or installing a Transceiver Module you must disconnect all cables, because of leaving these attached will damage the cables, connectors, and the optical interfaces. At the same time please be aware that do not often remove and install an SFP transceiver and it can shorten its useful life. For this reason transceivers should not be removed or inserted more often than is required. Furthermore, transceiver modules are sensitive to static, so always ensure that you use an ESD wrist strap or comparable grounding device during both installation and removal.

     

    Required Tools

    You will need these tools to install the SFP transceiver module:
    Wrist strap or other personal grounding device to prevent ESD occurrences.Antistatic mat or antistatic foam to set the transceiver on.Fiber-optic end-face cleaning tools and inspection equipment

     

    Installing SFP Transceiver Modules

    SFP transceiver modules can have three types of latching devices to secure an SFP transceiver in a port socket:
    SFP transceiver with a Mylar tab latch.SFP transceiver with an actuator button latch.SFP transceiver that has a bale-clasp latch.
    Types of SFP Latching

    Determine which type of latch your SFP transceiver uses before following the installation and removal procedures.

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  • Fiber Media Converter Tutorial

    Fiber media converter is a cost-effective solution to overcome the bandwidth and distance limitations of traditional network cable. It dramatically increases the bandwidth and transmission distance of the local area network (LAN) by allowing the use of fiber and integrating new equipment into existing cabling infrastructure. To better understand it, this article will give an overview of fiber media converter.

    What is Fiber Media Converter?

    Fiber media converter is a transfer media that connects two dissimilar media types. Generally, it is a device that converts electrical signal used in copper unshielded twisted paired (UTP) network cabling into light waves used in fiber optic cabling, and vice versa. This kind of fiber media converter is called copper-to-fiber media converter that provides a simple way to introduce fiber into a LAN without tearing out the existing copper wiring or making changes to copper-based switches. Furthermore, there is another kind of fiber media converter that supports fiber-to-fiber conversion, which provides connections between dual-fiber and single-fiber or between multimode fiber and single-mode fiber. Fiber-to-fiber media converters also provide a cost-effective solution for wavelength conversion in Wavelength Division Multiplexing (WDM) applications, which are also known as transponders.

    Types of Fiber Media Converters

    There are a wide variety of fiber media converters available in the market. According to different criteria, fiber media converters may be classified into different types.

    Managed VS Unmanaged

    The managed fiber media converter has the functions of networking monitoring, fault detection and remote management. It helps the network administrator to easily monitor and manage the network. An unmanaged fiber media converter, however, allows for simple communication with other devices and does not have the monitoring and management functions that managed fiber media converter has.

    Platform: Stand-Alone VS Modular Chassis-Based

    According to the platform type, fiber media converters can be divided into stand-alone fiber media converter and modular chassis-based fiber media converter. Stand-alone fiber media converters are designed to be used in where a single or limited number of converter(s) need(s) to be quickly implemented. Modular chassis-based fiber media converters, however, are used in high-density applications that multiple points of copper and/or fiber integration are essential.

    Copper-to-Fiber Media Converter VS Fiber-to-Fiber Media Converter

    According to media types, fiber media converters may be classified into copper-to-fiber media converter and fiber-to-fiber media converter.

    Copper-to-Fiber Media Converter

    Copper-to-fiber media converters are the key to integrating fiber into a copper infrastructure. According to different applications, copper-to-fiber media converters may be further divided into Ethernet copper-to-fiber media converters, video-to-fiber media converters and serial-to-fiber media converters.

    Fs copper-to-fiber-media-converter.jpg

    Ethernet Copper-to-Fiber Media Converter

    This kind of fiber media converter supports the IEEE 802.3 standard and provides connectivity for Ethernet, fast Ethernet, Gigabit and 10 Gigabit Ethernet devices. SC to RJ45 media converters, SFP to RJ45 media converters, PoE media converters, mini media converters and industrial media converters are all among this type.

    Fs ethernet-copper-to-fiber-media-converter.jpg

    The SC to RJ45 media converter comes with RJ45 and SC ports, which is designed to be used with fiber cable preterminated with the SC-type connector.The SFP to RJ45 media converter comes with RJ45 and pluggable fiber optics ports, which allows for flexible network configurations using SFP transceivers. PoE media converters can transparently connect copper to fiber while providing Power-over-Ethernet (PoE) to standards-based PoE compliant devices such as IP cameras, VoIP phones and wireless access points. Mini media converter is a miniature-sized copper-to-fiber converter. It is ideal for bringing fiber to the desktop and for mobile applications where light weight, compact size and low power are required.Industrial media converters are compact and robust devices designed to convert Gigabit Ethernet or Fast Ethernet networks into Gigabit or Ethernet fiber optic networks.

     

    Video Copper-to-Fiber Media Converter

    Video copper-to-fiber media converter also called fiber optic multiplexer, which is used to transmit and receive signals such as video, audio, data and Ethernet. fiber optic multiplexers are devices that process two or more light signals through a single optical fiber (as shown in the following figure), increasing the amount of information that can be carried through a network. Since signals may be analog or digital, video copper-to-fiber can be further divided into converters transmitting analog signals and converters transmitting digital signals. As the name applies, converters transmitting analog signals give amplitude or frequency modulation of the electric signal and then convert it into optical signal. Demodulation will also be done at the receiving end. Converters transmitting digital signals, however, digitize and multiplex the video, audio and data signals, transforming multiple low-speed digital signals into one high-speed signal. This high speed signal will then be turned into optical signal transmitting on a fiber.

    Fs vedio-copper-to-fiber-media-converter.png

    In accordance with different applications, there are three commonly used video copper-to-fiber media converters: plesiochronous digital hierarchy (PDH) multiplexers, synchronous digital hierarchy (SDH) multiplexers and synchronous plesiochronous sigital hierarchy (SPDH) multiplexers. Using the PDH fiber transmission technologies, PDH multiplexers are E1 point-to-point optical transport equipment. And the general transmission capacity of this kind of multiplexer is 4E1,8E1 and 16E1. SDH multiplexers, having a large transmission capacity, are designed to support end-to-end provisioning and management of services across all segments of the optical network. SPDH multiplexers adopt both PDH and SDH technologies. It is a PDH transmission system that based on the PDH code speed adjustment principle at the same time, use as far as possible parts of the SDH network technology.

    Serial-to-Fiber Media Converter

    This kind of media converter provides fiber extension for serial protocol copper connections. It accepts serial data on one port in RS232, RS485 or other format and convert the serial data stream into a fiber optic signal to a matching unit at the other end of the fiber span.

    Fs serial-to-fiber-media-converter.jpg

    Fiber-to-Fiber Media Converter

    Fiber-to-fiber media converters are used to extend network distance by providing connectivity between multimode and single-mode fiber, between different “power” fiber sources and between dual fiber and single-fiber. Furthermore, they also support conversion from one wavelength to another. Mode converter and WDM OEO transponder are two common types of fiber-to-fiber media converters.

    Mode Converter

    A mode converter can be used to allow for an adiabatic transition between two optical modes. Other than cross-connecting different fiber types, mode converters can also re-generate optical signals, extending transmission distance and double fiber cable usage. It is usually applied in multi-mode to single-mode fiber conversion.

    Fs mode-converter.jpg

    WDM OEO Transponder

    When a fiber media converter is used in the WDM system, it is called WDM OEO transponder which converts the incoming signal from the end or client device to a WDM wavelength. WDM OEO transponders are often used for dual fiber to single fiber conversion and wavelength conversion.

    Networks may require conversion between dual and single-fiber, depending in the type of equipment and the fiber installed in the facility. The following figures shows the role of WDM transponder played in the fiber optic network.

    Fs wdm-oeo-transponder-dual-fiber-to-single-fiber-conversion.jpg

    WDM OEO transponders are capable of wavelength conversion by using small form-factor pluggable (SFP) transceivers that transmit different wavelengths, provide a cost-effective solution to convert from standard optical wavelengths (850nm, 1310nm and 1550nm) of legacy equipment to optical wavelengths specified for WDM networks.

    Fs wdm-oeo-transponder-wavelength-conversion.jpg

    Selection Guide of Fiber Media Converters

    A proper fiber media converter may provide a cost-effective solution for extending Ethernet transmission while reducing cable and labor cost. When selecting fiber media converters for your network, the following points should be taken into consideration:

    The chip of the fiber media converter shall work in both full-duplex and half-duplex systems. The reason is that some N-Way Switches and HUBs may use half-duplex mode operations, and serious collision and data loss may be caused if the fiber media converter only supports full-duplex operation. Connection test should be done between the fiber media converter and different optical fiber splices. Otherwise, data loss and unstable transmission may happen on account of incompatibility between different fiber media converters.To ensure the proper operation of the fiber media converter, temperature measurement is also necessary. This is because the fiber media converter may not work correctly in high-temperature environment. Thus, it is important to know exactly its working temperature.Safety device guarding against data loss shall be equipped in the fiber media converter.The fiber media converter shall meet the IEEE802.3 standards. If not, there must be a risk of incompatibility.
     
    For a selection of Compufox fiber media converters, please click on the link below:
     
     
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  • Fiber Optic Overview

    Fiber Optic Communication - The Future Of Networking & Data Transmission

    Fiber optic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fiber. The light forms an electromagnetic carrier wave that is modulated to carry information.

    First developed in the 1970s, fiber-optic communication systems have revolutionized the telecommunications industry and have played a major role in the advent of the Information Age. Because of its advantages over electrical transmission, optical fibers have largely replaced copper wire communications in core networks. Optical fiber is used by many telecommunications companies to transmit telephone signals, Internet communication, and cable television signals. Researchers have reached internet speeds of over 100 petabits per second using fiber-optic communication.

    Fiber's advantages has led to its use as the backbone of all of today's communications, telecom, Internet, CATV, etc. - even wireless, where towers are connected on fiber and antennas are using fiber up the towers.

    Fiber Communication Example

     

    Optical Fiber - The Better Solution

    Fiber vs. Copper. Fiber is the better solution!

    This photo from the infancy of fiber optics (to the right) was used to illustrate that one tiny optical fiber could carry more communications signals than a giant copper cable. Today one single mode fiber could carry the same amount of communications as 1000 of those old copper cables!

    Fiber offers thousands of times more bandwidth than copper cables and can go more than 1000 times further before needing repeaters - both of which contribute to the immense economic advantage of fiber optics over copper. You can do a similar analysis for using wireless transmission also, but wireless is limited by the available wireless spectrum which is overcrowded because of everyone's desire to use more mobile devices.

    Why Convert From Copper Cable To Fiber Optic Cable?

    If you need some convincing before you make your first fiber optic cable purchase keep the following facts in mind.

    CheckOptical Fiber - Much More Efficient & Secure

    Fiber optic cable operates much more efficiently and is more secure than traditional copper cabling. Fiber can transmit far more information over greater distance and with a higher clarity while offering a more secure connection. Fiber optic cable is resistant to electromagnetic interference and generates no radiation of its own. This point is important in locations where high levels of security must be maintained. Copper wire radiates energy that can be monitored. In contrast, taps in  Fiber optic cable  Fiber  are easily detected. Copper cable, is also subject to problems with attenuation, capacitance, and crosstalk.

    CheckOptical Fiber - Does Not Require Grounding

    Since fiber is made of glass, which is a bad electrical conductor, it does not require grounding and shields itself from other electrical interference. Fiber cables can be run near electrical cables without fear that it will weaken or interrupt the signal.

    CheckOptical Fiber - Corrosion Resistant

    Fiber optic cable does not corrode and is not as sensitive to water or chemicals. This means you can safely run fiber cable in direct contact with dirt or in close proximity to chemicals (with the proper outer jacket materials).

    CheckOptical Fiber - The Safer Choice

    Since fiber is not a good conductor of electricity, an installer or user will be safe from electrocution if there is a break in the outer jacket and the fiber is exposed.

     

    How Fiber Optic Communication Works

    The process of communicating using fiber-optics involves the following basic steps: Creating the optical signal involving the use of a transmitter, relaying the signal along the fiber, ensuring that the signal does not become too distorted or weak, receiving the optical signal, and converting it into an electrical signal.

    Fiber (or fibre) consists of a strand of pure glass a little larger than a human hair. Fiber optic cable employs photons and pulsing laser light for the transmission of digital signals. Photons pass through the glass with negligible resistance. As light passes through the cable, its rays bounce off the cladding in different ways as shown below. The optic core of fiber optic cable is pure silicon dioxide. The electronic 1s and 0s of computers are converted to optically coded 1s and 0s. A light-emitting diode on one end of the cable then flashes those signals down the cable. At the other end, a simple photodetector collects the light and converts it back to electrical signals for transmission over copper cable networks.

    Fiber light source and transmission illustartion.

    Step index multimode was the first fiber design but is too slow for most uses, due to the dispersion caused by the different path lengths of the various modes. Step index fiber is rare - only POF uses a step index design today.

    Graded index multimode fiber uses variations in the composition of the glass in the core to compensate for the different path lengths of the modes. It offers hundreds of times more bandwidth than step index fiber - up to about 2 gigahertz.

    Singlemode fiber shrinks the core down so small that the light can only travel in one ray. This increases the bandwidth to almost infinity - but it's practically limited to about 100,000 gigahertz - that's still a lot!

     

    Optic Fiber Cable Construction

    Optic Fiber Cable Structure.

     

    Optical fiber consists of a core and a cladding layer, selected for total internal reflection due to the difference in the refractive index between the two. In practical fibers, the cladding is usually coated with a layer of acrylate polymer or polyimide. This coating protects the fiber from damage but does not contribute to its optical waveguide properties.

    Individual coated fibers (or fibers formed into ribbons or bundles) then have a tough resin buffer layer and/or core tube(s) extruded around them to form the cable core. Several layers of protective sheathing, depending on the application, are added to form the cable.

    Rigid fiber assemblies sometimes put light-absorbing ("dark") glass between the fibers, to prevent light that leaks out of one fiber from entering another. This reduces cross-talk between the fibers, or reduces flare in fiber bundle imaging applications.

    A “dopant” is added to the core to actually make it less pure than the cladding. This changes the way the core transmits light. Because the cladding has different light properties than the core, it tends to keep the light within the core. Because of these properties, fiber optic cable can be bent around corners and can be extended over distances of up to 100 miles.

    A typical laser transmitter can be pulsed billions of times per second. In addition, a single strand of glass can carry light in a number of wavelengths (colors), meaning that the data-carrying capacity of fiber optic cable is potentially thousands of times greater than copper cable.

     

    Types Of Fiber Optic Cable

    • Plastic cable, which works only over a few meters, is inexpensive and works with inexpensive components.
    • Plastic-coated silica cable offers better performance than plastic cable at a little more cost.
    • Single-index monomode fiber cable is used to span extremely long distances. The core is small and provides high bandwidth at long distances. Lasers are used to generate the light signal for single-mode cable. This cable is the most expensive and hardest to handle, but it has the highest bandwidths and distance ratings.
    • Step-Index multimode cable has a relatively large diameter core with high dispersion characteristics. The cable is designed for the LAN environment and light is typically generated with a LED (light-emitting diode).
    • Graded-index multimode cable has multiple layers of glass that contain dispersions enough to provide increases in cable distances.

    Cable specifications list the core and cladding diameters as fractional numbers. For example, the minimum recommended cable type for FDDI (Fiber Distributed Data Interface) is 62.5/125 micron multimode fiber optic cable.That means the core is 62.5 microns and the core with surrounding cladding is a total of 125 microns.

    • The core specifications for step-index and graded-index multimode cables range from 50 to 1,000 microns.
    • The cladding diameter for step mode cables ranges from 125 to 1,050 microns.
    • The core diameter for single-mode step cable is 4 to 10 microns, and the cladding diameter is from 75 to 125 microns.
    Choosing the right Optic Fiber Glass Type/ Fiber Mode.

     

    Indoor Vs. Outdoor Optic Fiber Cable Applications

    For  indoor applications, the jacketed fiber is generally enclosed, with a bundle of flexible fibrous polymer strength members like aramid (e.g. Twaron or Kevlar), in a lightweight plastic cover to form a simple cable. Each end of the cable may be terminated with a specialized optical fiber connector to allow it to be easily connected and disconnected from transmitting and receiving equipment.

    For outdoor applications or use in more strenuous environments, a much more robust cable construction is required. In loose-tube construction the fiber is laid helically into semi-rigid tubes, allowing the cable to stretch without stretching the fiber itself. This protects the fiber from tension during laying and due to temperature changes. Loose-tube fiber may be "dry block" or gel-filled. Dry block offers less protection to the fibers than gel-filled, but costs considerably less. Instead of a loose tube, the fiber may be embedded in a heavy polymer jacket, commonly called "tight buffer" construction. Tight buffer cables are offered for a variety of applications, but the two most common are "Breakout" and "Distribution".

    Breakout Cables normally contain a ripcord, two non-conductive dielectric strengthening members (normally a glass rod epoxy), an aramid yarn, and 3 mm buffer tubing with an additional layer of Kevlar surrounding each fiber. The ripcord is a parallel cord of strong yarn that is situated under the jacket(s) of the cable for jacket removal. Distribution Cables  have an overall Kevlar wrapping, a ripcord, and a 900 micrometer buffer coating surrounding each fiber. These fiber units are commonly bundled with additional steel strength members, again with a helical twist to allow for stretching.

    A critical concern in outdoor cabling is to protect the fiber from contamination by water. This is accomplished by use of solid barriers such as copper tubes, and water-repellent jelly or water-absorbing powder surrounding the fiber.

    Finally, the cable may be armored to protect it from environmental hazards, such as construction work or gnawing animals. Undersea cables are more heavily armored in their near-shore portions to protect them from boat anchors, fishing gear, and even sharks, which may be attracted to the electrical power that is carried to power amplifiers or repeaters in the cable.

    Modern cables come in a wide variety of sheathings and armor, designed for applications such as direct burial in trenches, dual use as power lines, installation in conduit, lashing to aerial telephone poles, submarine installation, and insertion in paved streets.

    To purchase your fiber cables, please click link below:

    Fiber Patch Cables

     

     

     

     

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  • Feds get huge response to request for IoT input

    By Sean Kinney   www.industrialiot5G.com

     

     

    More than 100 companies suggest ways U.S. government can help advance the IoT

    Many industry watchers feel the U.S. is slipping behind other countries, particularly Germany and China, in creating a unified national strategy for development of the Internet of Things or IoT. But federal leaders, in the early stages of involvement, reached out to the telecom industry for guidance.

    Back in April the National Telecommunications and Information Administration, a part of the U.S. Department of Commerce, issued a “request for comments on the benefits, challenges and potential roles for the government in fostering the advancement of the Internet of Things.”

    Two months later and the call for comment has been met in spades with more than 130 filings coming from a broad swath of telecom interests including carriers like AT&T, T-Mobile, Verizon and Vodafone; vendors including Nokia, Ericsson, Huawei and Samsung; and industry trade groups like the Wi-Fi Alliance, Wireless Infrastructure Association, the Open Connectivity Foundation and the GSMA.

    Here’s a full list of the respondents and their filings with NTIA. A review of some of the filings indicates a strong industry expectation that the rapid uptake of IoT will require global coordination and will likely create new markets while disrupting existing ones.

    Verizon representatives told NTIA: “To support this explosion of IoT devices, a robust and secure underlying communications network must serve as a foundation. That network requires both increased commercial spectrum and development of the underlying core infrastructure. We encourage all stakeholders to work together to ensure that these necessary building blocks for IoT development are available and accessible. To enable sufficient spectrum to power this new wave of connected innovation, private and public sectors must continue to cooperate, not only to develop more ways to effectively share spectrum, but also to provide federal users incentives to free up spectrum for commercial licensed and unlicensed use. As potentially billions of new IoT devices are deployed, they will drive data growth that – combined with the parallel growth in overall data usage by consumer devices – will require new commercial spectrum allocations to accommodate the unprecedented demands for more bandwidth. This includes spectrum necessary to support 5G, since 5G’s super-fast speeds and low latency will help facilitate new IoT use cases.”

    Ericsson commented: “In Ericsson’s view, 5G is the technology that will unleash the true potential of the Internet of Things. To support the IoT’s development, the government should unleash the resources that will ensure U.S. leadership in 5G by releasing more spectrum for commercial use. Through network slicing, 5G technology will allow a single infrastructure to meet the very different needs of Massive and Critical IoT devices – it will enable networks to handle the incredible increase in data from the billions of low energy, low data devices, while also providing very high reliability, availability and security for critical uses. We also encourage the government to support global standards and best practices and to allow industry to continue to innovate and coalesce around the most favorable IoT solutions.”

    And from the GSMA’s point of view: “The United States should forbear from regulating IoT and avoid reflexively extending legacy regulations designed for outdated technologies to the IoT…The U.S. government should support and promote industry alignment around interoperable, industry-led specifications and standards across the global IoT ecosystem…The U.S. government should promote the allocation of globally harmonized spectrum that can support IoT…The U.S. government should encourage industry to build trust into IoT devices. Existing laws and regulations, operating in tandem with self-regulatory regimes and best practices, will provide sufficient protection to consumers as the IoT develops…Finally, the U.S. government should engage on a bilateral and multilateral basis, as appropriate, to ensure that international IoT activities similarly encourage competition, investment, and innovation. Regulatory interference at this stage—from any source—could lead to fragmentation and impede innovation, inhibiting the IoT’s ability to reach its full potential to deliver benefits to consumers.”

     

     

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