What is Distributed Acoustic Sensing (DAS)?

Distributed Acoustic Sensing (DAS) is a technology that enables continuous, real-time measurements along the entire length of a fiber optic cable.  Unlike traditional sensors that rely on discrete sensors measuring at pre-determined points, distributed sensing utilizes the optical fibre. The optical fiber is the sensing element.

AcoustiSens® Wideband Single-Mode Optical Fiber, the newest addition to the OFS LineaSens® family, is a vibration sensing fiber with optimal performance for DAS systems.  Using a waveguide design based on the ITU-T G.657.A1 telecom-grade single-mode standard, AcoustiSens Wideband Optical Fibers significantly increase Rayleigh backscatter while maintaining low attenuation to improve Optical Signal to Noise Ratio (OSNR).  Furthermore, the AcoustiSens Wideband Optical Fibers provide bend-insensitivity and expand the operating wavelength band (1536 – 1556 nm) ensuring interoperability with all known DAS interrogators.

AcoustiSens Wideband is intended for use in cables designed as sensing components in DAS systems. Without the need for changes in interrogation equipment or complex optical amplification schemes AcoustiSens Wideband is a drop-in fiber replacement that provides greatly improved sensing performance with OSNR orders of magnitude better than telecom-standard fibers.  This translates into significantly improved ASNR in DAS systems.  Due to its waveguide design, AcoustiSens fibers are also bend-insensitive and splice compatible with G.657.A1 and G.652.D optical fibers, assuring smooth integration with commonly deployed sensing solutions.

AcoustiSens Optical Fibers are intended for use as components in optical and hybrid cables designed for vibration or acoustic sensing applications including:

  • Pipeline monitoring (midstream)
  • Rail monitoring
  • Perimeter monitoring
  • Subsea monitoring
  • Highway monitoring
  • Smart City applications

To learn more about AcoustiSens watch this video overview or visit the OFS website.  Or you may contact us to discuss solutions to your sensing needs.

A Hollow-Core Fiber Cable for Low Latency Transmission – when microseconds count

AccuCore HCF™ Optical Fiber Cable is the world’s first terrestrial hollow-core fiber (HCF) cable solution. Light travels about 50% faster in a hollow core optical fiber compared to the solid silica core of conventional fiber. Consequently, light transmitted in a hollow-core fiber arrives 1.54 microseconds faster for each kilometer traveled compared with conventional optical fiber.

The AccuCore HCF Optical Fiber Cable solution includes indoor/outdoor cable and termination with standard connectors, which are fusion-spliced to the patented photonic bandgap hollow-core fiber. OFS also offers installation services and both passive and active component selection to meet customer requirements.  AccuCore HCF optical fiber cable has been successfully deployed, carrying live traffic in several networks.

This latest development from OFS was presented as a postdeadline paper on March 12, 2020 at the Optical Fiber Communication Conference and Exhibition (OFC) held in San Diego.  OFC postdeadline papers represent the latest and most advanced technical achievements in the field. The paper reported error-free transmission of direct-detection 10 Gb/s DWDM signals over 3.1 km of cascaded cabled HCF. This is the first time that transmission results in a cabled HCF have been reported.  That white paper is available here.

 Contact OFS to learn more about AccuCore HCF fiber optic products.

The OFS Fiber Connection in The U.S. Virgin Islands

The co-inventor of optical fiber, Dr. Peter Schultz, is a resident of the Virgin Islands. He was instrumental in convincing the local authorities back in the early 2000’s that the islands needed high-speed connectivity afforded by optical fiber. He assisted in the successful lobbying of federal and local governments to provide funding for the project and in 2009 The Virgin Islands Next Generation Network (ViNGN) was formed. This video shows how he partnered with OFS to deliver high-speed fiber connectivity to the U.S. Virgin Islands and specifically to his condo unit. OFS designed the fiber to the MDU (Multiple Dwelling Unit) network with the InvisiLight® Facade Solution using the 12-Fiber M-Pack® Indoor Outdoor MDU Drop Cable and SlimBox® Indoor Outdoor Enclosures. For inside the MDU, a SlimBox 64-Fiber Indoor Enclosure and the InvisiLight Indoor Living Unit (ILU) Solution were installed. OFS oversaw the installation for ViNGN with technicians from local contractor ADM Technologies, Inc.

Fiber Optic Dispersion and other Non-Linear Effects

This article focuses on the parameters that affect available bandwidth in optical fibers, and the dispersion mechanisms of various fiber types and non-linear effects.  Dispersion describes the process of how an input signal broadens out as it travels down the fiber. There are several types of dispersions that we will cover. We’ll also take a cursory look at other important nonlinear effects that can reduce the amount of bandwidth that is ultimately available over an optical fiber.

Dispersion

Fiber Optic Dispersion Bandwidth Illustration

Most of the traffic traveling through fiber networks takes the form of a laser pulse, where the laser is pulsed on and off, effectively forming a digital square wave comprised of “1”s and “0”s. Dispersion causes a pulse to spread out over time, effectively rounding the edges, and making it harder for the detector to determine whether a “1” or a “0” is being transmitted. When this happens, the effective bandwidth of the link is reduced. The three main types of dispersion mechanisms are modal dispersion, chromatic dispersion, and polarization mode dispersion. Because these mechanisms affect fiber networks in different ways, we’ll discuss each in some depth. Please download the full article for more information.

Modal Dispersion

In general, our article on Single-Mode Optical Fiber Selection focuses on single-mode fibers since they comprise the vast majority of fiber kilometers deployed around the world. In contrast to multimode fibers, single-mode fibers are used for all high-capacity, long-distance networks due to their low attenuation and high bandwidth. A main limiting factor of multimode fibers is modal dispersion.

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Illustration of Modal dispersion in a multimode and single optical fibers

Multimode fibers carry multiple modes of light at the same time.  While a mode of light can be thought of as a ray of light, a typical multimode fiber can have up to 17 modes of light traveling along it at once. These modes all traverse slightly different paths through the fiber, with some path lengths longer than others. Modes that take a straighter path will arrive sooner, and modes that bounce along the outer edges of the core of the fiber take a longer path and arrive later. The effect on the end pulse is called modal dispersion, since it is due to the different modes in the fiber. Multimode fibers are designed to reduce the amount of modal dispersion with precise control of the index of refraction profile, through the quantity of dopants used in the core. However, it isn’t possible to completely eliminate modal dispersion in multimode fibers.

Chromatic Dispersion

Chromatic dispersion describes a combination of two separate types of dispersion, namely material dispersion and waveguide dispersion. Light travels at different speeds at different wavelengths, and all laser pulses are transmitted over a wavelength range. Light also travels at different speeds through different materials. These varying speeds cause pulses to either spread out or compress as they travel down the fiber. Fiber designers can use these two points to customize the index of refraction profile to produce fibers for different applications. Chromatic dispersion isn’t always a bad thing. In fact, it can be used as a tool to help optimize network performance.

For example, the first lasers used for fiber transmission operated at 1310 nm, and many networks still use that wavelength. Fiber designers therefore developed the first single-mode fibers to have minimum or zero dispersion at this wavelength. In fact, G.652 fibers are still designed this way. In these fibers, dispersion is higher in the 1550 nm window.

Today’s networks often operate with multiple wavelengths running over them. In these networks, nonlinear effects that result from the multiple wavelengths can affect network operation. We’ll give a brief overview of some of these non-linear effects in this article. Chromatic dispersion is often used as a tool to help optimize these types of networks.

Polarization Mode Dispersion (PMD)

Light is an electromagnetic wave and is comprised of two polarizations that travel down the fiber at the same time. In a perfectly round fiber deployed with perfectly balanced external stresses, these polarizations would reach the end of the fiber at the same time. Of course, our world isn’t perfect. Even small amounts of glass ovality/non-concentricity or non-concentric stresses in the cable can cause one of the polarizations to travel faster than the other, spreading out in time as they travel along the fiber. This phenomenon is called polarization mode dispersion (PMD).

Polarization mode dispersion illustration- delay in two polarizations traveling down an optical fiber.

Cabling and installation affect PMD, and even things like vibration from trains moving down tracks or wind-induced aerial cable vibrations can affect PMD. However, the impacts of these interactions are typically smaller than the inherent PMD caused by the glass manufacturing process.

Manufacturing Caused of Polarization Mode Dispersion (PMD)

There are ways to mitigate PMD. One very effective method is to make the glass fiber as geometrically round and consistent as possible. OFS uses a special technique to accomplish this. Using a patented process called fiber “spinning”; half-twists are translated through the fiber during the draw process, reducing the non-concentricities and ovalities in the glass that are the major contributors to increased PMD.

PMD Chart

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Non-Linear Effects

There are a host of other factors that network, equipment, and fiber designers have needed to consider as network capabilities have grown over the years. These factors often result as we collectively add more and more wavelengths of traffic at greater speeds and higher power levels.

It is not the intent of this article to review each of these in depth, but instead to touch on them so the reader can have a passing familiarity. The highest profile of these factors is four-wave mixing, which led to the development of non-zero dispersion-shifted fibers (NZDF). However, other non-linear effects include self-phase modulation, cross-phase modulation, Raman and Brillouin scattering, and others. As mentioned earlier, chromatic dispersion can be used to offset the effects of four-wave mixing. For those non-linear effects related to higher power levels, increasing the effective area where the light travels down the fiber can help to reduce the impact of these other non-linear effects.

Dispersions and non-linear effects are the least understood issues in the general fiber user population, mainly because the guidelines used to match up today’s fibers and electronics typically work so that the end user doesn’t need to have a detailed background to bring up a system.

OFS has multiple decades of experience with fiber optic networks. Please contact your local OFS representative if you would like additional information regarding any of the items in this article.

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OFS is a market leader in the design and manufacture of standard and custom Dispersion Slope Compensating Modules (DSCMs) also known as Dispersion Compensating Modules (DCMs). Our fixed broadband, reconfigurable, and tunable colorless modules round out a product line that is well-suited for the major transmission fiber types.

Bandwidth Drivers and Fiber Optic Standards

The fiber optic cable world has come a long way over the past 30 years. Products have become more rugged and user friendly, making it easier for people to enter the industry and work handling optical fiber and cable. While this is great for the industry, many people may understand the “how to” but not necessarily the “why” of fiber optics. To understand the “why” behind fiber and cable products, the next step is to become a full-fledged “fiber geek.” Because the industry changes so quickly, it’s important to understand fiber specifications are continuously changing.

Bandwidth demand continues 

Enjoying virtual reality technologyThe demand for bandwidth continues unabated, driven by Web 1.0/2.0, mobile and now streaming video. The result is an expected Compound Annual Growth Rate (CAGR) of approximately 22% across the network through 2020.

While that’s somewhat old news, new bandwidth demand is on the horizon, potentially driven by several relative sources including 4K TV, virtual reality and an expansion of the “Internet of Things.”

Ultra HD TV, also known as 4K TV, first appeared on the radar screen approximately four to five years ago. While 4K TV offers twice the resolution of standard HDTV, the first models were priced at more than $20,000. Since then, the cost of 4K TV units has dropped rapidly to the point that they are now ubiquitously available at most electronics stores.

While linear TV packages still don’t offer many 4K programming options, over-the-top video providers such as Netflix and Amazon Video are rapidly adding content.

The primary reason that 4K TV is significant to bandwidth demand is that each 4K channel requires up to 25 Mbps, more than 2X the typical HD video requirement. Considering the number of TV screens that are typically on in a household, the potential demand could be a significant increase versus current HDTV demand levels.

High resolution screens are also an integral part of the experience promised by virtual reality. Virtual reality, while in its commercialized early stages, holds the promise of significantly changing the way that we experience media of all types. However, there’s a catch – fully- networked 4K virtual reality will require hundreds of megabits per second (or more) of bandwidth(1).

High Def TVHigh resolution video will continue to use bandwidth as it becomes embedded in various networked applications such as telemedicine, remote medical monitoring and distance learning.

Why does optical fiber care?

This bandwidth demand can be satisfied in three ways: faster electronics, more wavelengths on the fiber and more optical fiber.

Standards are important

IOT requires Fiber StandardsFiber optic standards help to ensure a minimal level of network compatibility and performance. The standards-making process is an arduous one. Fiber standards are global, and standards makers strive to achieve balance and fairness. However, standards often provide only minimum performance levels. In fact, fibers that meet the standards may struggle with some current as well as future applications.

For this reason, it’s best to insist on fiber optic performance beyond the standards for many applications.

The demand for bandwidth is expected to continue far into the future, driven in part by requirements for breakthrough applications such as higher resolution video, virtual reality and other applications. We expect this demand to continue to drive the need for optical spectrum provided by fiber. Fiber standards, such as G.652 and G.657, are very important for network designers in setting minimum performance levels but can ultimately be insufficient to meet the requirements for future networks. For this reason, performance beyond the standards can be very important.

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Reference (1): Why The Internet Pipes Will Burst When Virtual Reality Takes Off

Optical Fiber Building Solutions

FTTX Building Optimized Fiber Infrastructure

Optical fiber-to-the-business deployment is accelerating globally to support increasing internet speeds of up to 1 Gigabit per second, and 10 Gigabit speeds that are already available in some regions. Service providers are responding by installing optical fiber both to and deep inside buildings to the living unit.

The Solutions in this 64-page guide can help reduce both first and life cycle costs of optical fiber deployments to residential and business customers.

Solutions for both Greenfield installation during building construction and Brownfield installation in existing buildings are included. Scalable and optimized to fit a broad range of building structures, these solutions offer faster, reliable installation through innovative labor saving technologies, using less space than conventional approaches.

Solutions for both indoor and outdoor deployment offer flexibility to use the best available pathways for each building. The solution building blocks include a wide range of terminals, splitters, point-of-entry modules, riser cables, attic and wall fish fiber, hallway fiber and complete indoor living unit fiber kits. This portfolio allows service providers to select the best solution for each building, and OFS can help design building specific solutions and bills of material as a value added service.

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FIBER TO THE BUILDING BENEFITS 

OFS fiber-to-the-subscriber (FTTx) solutions help to revolutionize the speed of installing fibers; enhance the customer experience; minimize disruption; reduce labor costs; increase subscriber take rates; enable faster time to revenue for service providers; and get Gigabit and higher speeds faster to subscribers.

OPTICAL FIBER BUILDING CHALLENGES AND SOLUTIONS 

  • Time to revenue: Fast and easy to install pre-terminated solutions can speed installation and reduce labor costs.
  • No pathways, requiring labor intensive cut and patch: Compact surface mounted fiber solutions.
  • Limited closet space: Smaller enclosures can enable installation of multiple operator connections in a small telecommunications closet.
  • Multiple boxes for splicing and splitter connections: Single box pre-terminated solutions can require less space and enable faster provisioning.
  • No duct space: Compact surface mounted fiber solutions either inside or on the outside of the building do not require duct.
  • Shared infrastructure: Compact cables can support multiple service providers in telecommunication pathways.
  • Fiber bends around many corners: Bend-insensitive fiber specified to support bend radius as low as 2.5 mm.
  • Disruptive/noisy to tenants: Optical solutions that are virtually invisible can be installed quickly and quietly and preserve the building decor.
  • Service disruptions and lost subscribers: Full solution of fiber, cable and connectors from one company, designed to work together. Factory tested to Tier 1 standards.
  • Multiple building types: Solutions to fit each building type.

PRE-TERMINATED vs. FIELD TERMINATED OPTICAL FIBER

Pre-terminated solutions are increasingly used to install fiber in Multiple Dwelling Unit (MDU) buildings to save time and money in higher labor cost regions. Pre-terminated products with built-in slack management are preferred so installers can neatly manage excess slack and use a single component to support multiple deployment lengths. Nevertheless, field terminated solutions can complement pre-terminated parts of the indoor or outdoor network and, for low labor cost markets, field terminated solutions may be preferred. OFS offers both pre-terminated and field terminated solutions to fit the needs of each service provider.

OPTICAL FIBER SPECIFICATIONS OPTIMIZED TO THE APPLICATION

Installing optical fiber in buildings and homes often requires conforming the fiber around sharp corners. EZ- Bend® Single-Mode Fiber offers outstanding bend performance down to a 2.5 mm radius for the most challenging in-residence and MDU applications. Compatible with the installed base of conventional G.652.D single-mode fibers, the fiber meets and exceeds ITU-T G.657.B3 recommendations. EZ-Bend fiber uses patented, groundbreaking EZ-Bend Optical Technology from OFS to provide three times lower loss at tight bends than competing G.657.B3 products.

Centralized, Distributed and Distributed Cascaded Splitting

As FTTx deployment accelerates globally to meet increasing bandwidth needs, service providers must install optical fiber both to and inside the building for business and residential subscribers. Building types include duplexes, garden style, low rise (less than 10 floors), mid rise (10 to 15 floors), high rise (16 to 40 floors) and skyscrapers (40 floors and above). To provide building Gigabit services, providers must place optical cables in building risers and ducts, install optical fiber in hallways, and then take this fiber deep into the units, connecting to an indoor Optical Network Terminal (ONT). How can providers accomplish this in buildings that can vary widely in design, materials and available pathways?

Splitter Architectures

Cascaded SplitterA typical PON network consists of the Optical Line Terminal (OLT) in a central office, head end or cabinet, connected by a feeder cable to optical splitters, and then to distribution cables downstream in the network. Choosing the right architecture depends upon end-user density, projected subscription rates and distance from the OLT. Splitter placement is important in FTTx design as it can significantly affect plant and electronics costs.

Three common types of splitter architectures are used when deploying FTTx:

  • Centralized splitting
  • Distributed splitting
  • Distributed cascaded splitting

To help meet these needs, the OFS portfolio supports all three splitter architectures, and features a broad range of solutions to meet the requirements of virtually any MDU deployment. For flexibility and regional preferences, these offers include a mix of pre-connectorized, in-field fusion splicing and mechanical connector solutions from which OFS can configure customized designs for each type of building.

Brownfield Outdoor Facade Solution

The Outdoor Facade Solution is used when property owners want to preserve the decor of the building exterior. The compact EZ-Bend Indoor/Outdoor cable is placed vertically on the exterior wall of the residence from an outdoor wall mount box to an indoor SlimBox® unit. The indoor SlimBox can be factory configured with SCA adapters or fanouts for a pre-terminated solution, or for fusion splicing. EZ-Bend jumpers are used for the path to each living unit. Pre-terminated EZ-Bend Jumpers are recommended for faster installation, or a mechanical connector may be used for field termination in the SlimBox Wall Plate. The 80×80 InvisiLight® Module can be used as a “fiber extension” to any location in the living unit. Alternatively, instead of EZ-Bend jumpers, the InvisiLight MDU solution may be placed in the hallway to the living units (not shown).

Brownfield Outdoor Facade Solution

Brownfield Outdoor Facade Solution

Greenfield Pre-Terminated Solution

TELECOMMUNICATION ROOM

  • Compact basement box for a progressive customer activation;
  • The basement box (SlimBox 64F Terminal) allows fusion splices for the outside plant cable;
  • Ideal for buildings with low penetration rates: One splitter can be installed and the management of the customers is done through the SCA ports. A parking area permits easy connection of new customers;
  • Several boxes can be connected for modular expansion. Connections between multiple SlimBoxes are possible through access openings between them.

RISER BACKBONE

  • SCA pre-terminated cables for quick plug and play installation;
  • EZ-Bend patch cords directly from the apartment unit may be used for small buildings.

HORIZONTAL DEPLOYMENT

  • Direct deployment from the telecommunication closet to the apartment unit;
  • Ideal for Greenfield installation;
  • The EZ-Bend jumper is connected to an adapter installed in the SlimBox Wall Plate (inside the living unit).

INSIDE THE LIVING UNIT

  • An SCA mechanical connector can be used to terminate the EZ-Bend Jumper inside the living unit;
  • The InvisiLight ILU Solution is a complementary product used to extend the fiber inside the apartment.

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Greenfield Fusion Spliced or Field Terminated Solution

TELECOMMUNICATION ROOM

  • Compact basement box for a progressive customer activation (parking up to 48 connectors in the SlimBox 64F Terminal);
  • The basement box (SlimBox 64F Terminal) allows fusion splices for the outside plant cable and the internal cables (up to 96 fusion splices – 8 splice trays with 12 splices in each one);
  • Ideal for buildings with low penetration rate: One splitter can be installed with management of the customers done through the SCA ports. A parking area permits easy connection of new customers;
  • Several boxes can be connected for modular expansion. Connections between SlimBoxes are possible through access openings between them.

RISER BACKBONE

  • ACCUMAX® cables may be used for quick and easy installation:
  • SCA pre-terminated pigtails are used for fusion splicing inside the basement and floor boxes.

HORIZONTAL DEPLOYMENT

  • Direct deployment from the telecommunication closet to the apartment unit through EZ-Bend cable (ruggedized 3.0 or 4.8 mm);
  • The horizontal cable is fusion spliced or field terminated with a mechanical connector in the SlimBox 12F Terminal (floor distribution box) and in the SlimBox Wall Plate (inside the living unit).

INSIDE THE LIVING UNIT

  • An SCA mechanical connector can be used to terminate the EZ-Bend Jumper inside the living unit or a pre-terminated pigtail can be used;
  • The InvisiLight ILU Solution is a complementary product used to extend the fiber inside the apartment.

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Brownfield Pre-Terminated Solution

Brownfield Pre-Terminated Solution

Brownfield Pre-Terminated Solution

TELECOMMUNICATION ROOM

  • Compact basement box for progressive customer activation;
  • The basement box (SlimBox™ 64F Terminal) allows fusion splices to the outside plant cable;
  • Ideal for buildings with low penetration rate: One splitter can be installed with management of the customers done through the SCA ports. A parking area permits easy connection of new customers;
  • Boxes can be added for modular expansion. Connections between SlimBox units are easily made using jumpers through multiple ports designed into the box.

RISER BACKBONE

  • SCA pre-terminated cables for quick plug and play installation:
  • It is possible to place InvisiLight 2.0 mm 12-Fiber multifiber cord directly from the basement box and down hallways in small or garden style buildings.

HORIZONTAL DEPLOYMENT

  • The InvisiLight MDU Point of Entry (POE) Module offers a discrete solution using field termination inside the module;
  • Virtually invisible installation using the InvisiLight 12F Pre-terminated 2.0 mm cord.

INSIDE THE LIVING UNIT

  • InvisiLight ILU Solution is complementary and connects to the InvisiLight MDU installation;
  • InvisiLight ILU Solution is installed with the same tools and procedures as the InvisiLight MDU Solution

This 64-page guide with illustrations and part specifications will help in  selecting the right fiber optic cables and accessories to reduce both the first and life cycle costs of fiber deployments to business customers inside buildings.

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FAQ Guide to Laser-Optimized Fiber

As transmission speeds over optical fiber networks in the enterprise increase to 10 Gigabits per second (Gb/s) and beyond, a relatively new term – “laser-optimized fiber” – has crept into the industry’s vocabulary. What is laser-optimized fiber? What do you need to know about it? And what exactly does the term “laser- optimized” mean? Understanding the answers to these questions will help you prepare for the latest wave in optical communications for enterprise networks.Laser Fiber

Why have optical fibers been “optimized” for use with lasers?

Older “legacy” optical fiber systems (Token Ring, Ethernet, FDDI, ATM) used in premises applications operated at relatively slow speeds in the range of 4 to 155 Megabits per second (Mb/s). These systems utilized inexpensive light sources called Light Emitting Diodes (LEDs), which were perfectly adequate for these slower speeds. Multimode fibers used in these systems were rated to certain minimum bandwidths, typically:

  • 160 MHz/km over 62.5/125 μm fiber at 850 nm
  • 500 MHz/km over 50/125 μm fiber at 850 nm
  • 500 MHz/km over both products at 1300 nm

These fibers were tested for bandwidth using an Overfilled Launch (OFL) test method, which accurately replicated real-life performance with an LED.

As the demand for bandwidth and higher throughput increased, especially in building and campus backbones, LEDs could not keep pace. With a maximum modulation rate of 622 Mb/s, LEDs would not support the 1 Gb/s and greater transmission rates required. One could make use of traditional lasers (Fabry-Perot, Distributed Feedback) typically used over single-mode fiber.  However these are considerably more expensive due to the higher performance characteristics required for long-distance transmission on single-mode fiber.

In response, the industry developed a new high-speed laser light source called a Vertical Cavity Surface Emitting Laser (VCSEL). These VCSELs are inexpensive and well suited for low-cost 850 nm multimode transmission systems, allowing for data rates of 1 Gb/s and 10 Gb/s in the enterprise. With the emergence of these VCSELs, multimode fiber had to be “optimized” for operation with lasers.

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What’s the Difference Between a VCSEL and an LED?

VCSELs provide higher power, narrower spectral width, smaller spot size and faster data rates than LEDs. All of these advantages add up to a significant performance boost. This assumes, of course, the fiber itself does not hinder performance. To understand why this could occur, we need to recognize the differences between VCSELs and LEDs and how they transmit signals along a multimode fiber.

All LEDs produce a smooth, uniform output that consistently fills the entire fiber core and excites the many hundreds of modes in the fiber. The bandwidth of the fiber is determined by the aggregate performance of all the modes in the fiber. If a few modes lag behind or get ahead due to modal dispersion, they have little impact on bandwidth because many other modes are carrying the bulk of the signal.

The energy output of a VCSEL is smaller and more concentrated than that of an LED. As a result, VCSELs do not excite all the modes in a multimode fiber, but rather only a restricted set of modes. The bandwidth of the fiber is dictated by this restricted set of modes, and any modes that lag or get ahead have a much greater influence on bandwidth.

Typically, a VCSEL’s power would be concentrated in the center of the fiber, where older fibers were prone to defects or variations in the refractive index profile (the critical light-guiding property in the core of the fiber), resulting in poor transmission of the signal. That is why some fibers may actually perform poorly with a VCSEL compared to an LED.

To complicate matters, the power profile of a VCSEL is nonuniform and fluctuates constantly. It changes sharply across its face, varies from VCSEL to VCSEL and changes with temperature and vibrational fluctuations. Consequently, individual VCSELs will excite different modes in a certain fiber at any given time. And because different modes carry varying amounts of power, the fiber’s bandwidth can vary in an unpredictable manner.

Why are laser-optimized fibers the best choice for use with VCSELs?

With the advent of VCSELs, it became apparent that the traditional multimode fiber deployed for LED systems did not take full advantage of the performance benefits of VCSELs.

To fully capitalize on the benefits that VCSELs offered, fiber manufacturers developed laser-optimized multimode fiber (LOMMF). LOMMF is specifically designed, fabricated and tested for efficient and reliable use with VCSELs.

LOMMFs should have a well-designed and carefully controlled refractive index profile to ensure optimum light transmission with a VCSEL. Precise control of the refractive index profile minimizes modal dispersion, also known as Differential Mode Delay (DMD). This ensures that all modes, or light paths, in the fiber arrive at the receiver at about the same time, minimizing pulse spreading and, therefore, maximizing bandwidth. A good refractive index profile is best achieved through DMD testing.

VCSELs and LOMMF provide tremendous flexibility and cost efficiency in “freeing up” bandwidth bottlenecks in the enterprise today and well into the future. LOMMF is completely compatible with LEDs and other fiber optic applications (there are no special connectors or termination required and no effect on attenuation). LOMMF can be installed now and utilized at slower data rates until the need arises to increase network speed to 1 or even 10 Gb/s. At that point, you only need to upgrade the optics modules to VCSEL-based transceivers. There is no need to pull new cable.

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Can you use any laser-optimized fiber for 10 Gb/s?

No — it is important to note that not all laser-optimized fiber is 10 Gb/s capable. If 10 Gb/s capacity is in your future, you must make sure that the LOMMF you’re installing now is capable of handling 10 Gb/s. The first laser-optimized fibers, introduced to the market in the mid-1990s, were designed for 1 Gb/s applications. Available in both 62.5/125 µm and 50/125 µm designs, these fibers extended the reach capability of 1 Gb/s systems beyond what the industry standards stated. For instance, OFS 1 Gb/s Laser Optimized 62.5 Fiber can go 300 meters in cost-effective, 1 Gb/s 850 nm (1000BASE-SX) systems. 50/125 µm fibers offer even greater performance, with a reach of 600 meters or more. These 1 Gb/s LOMMFs, coupled with 850 nm VCSELs, allow for the lowest systems cost for building backbones and short-to medium-length campus backbones

How do you measure bandwidth for laser-optimized fiber?

Since LEDs have a uniform and consistent power profile that excites all the modes in a multimode fiber, the traditional OFL method of bandwidth measurement accurately predicts bandwidth of fiber for LED applications. But because VCSELs only excite some of the modes in a fiber, and in a varying manner, the OFL bandwidth measurement cannot predict what the fiber’s bandwidth would be if the fiber were to be used in a VCSEL application.

It should become clear now why fiber manufacturers developed laser-optimized fiber, and why DMD testing is so important. The refractive index has to be well designed and controlled to ensure that all modes exhibit minimal DMD and all arrive at the other end of the fiber at the same time. No matter which modes in the fiber are actually guiding the light, those modes will have minimal DMD and provide high bandwidth.

What should you look for in DMD testing?

DMD testing provides a clear picture of how individual mode groups carry light down the fiber, and which mode groups are causing DMD. In fact, that picture is so clear that the standards require fiber to be DMD-tested to ensure adequate bandwidth to the rated distances for 10 Gb/s applications.

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Tony Irujo is sales engineer for optical fiber at OFS, a world-leading designer, manufacturer and provider of optical fiber, fiber optic cable, connectivity, fiber-to-the-subscriber (FTTx)and specialty photonics products. Tony provides technical sales and marketing support for multimode and single-mode optical fiber.

Tony has 25 years of experience in optical fiber manufacturing, testing and applications. He started with SpecTran in 1993 as a quality and process engineer and transitioned to more customer-focused roles with Lucent and OFS. He represents OFS in the Fiber Optic LAN Section (FOLS) of the TIA, has authored several papers on fiber technology and applications and is a frequent speaker at industry events. Tony has a Bachelor of Science degree in Mechanical Engineering from Western New England College in Springfield, MA.

Now You See Optical Fiber — Now You Don’t

How do you make a great fiber optic solution even better? One way is to make the optical fiber less visible while also faster and easier to install.

The new InvisiLight® Indoor Living Unit (ILU) 600 Solution from OFS is setting a new benchmark for low-profile visibility. This new solution offers fast and virtually undetectable, indoor optical fiber installation for homes, offices, and multiple living units (MDUs).

To provide Wi-Fi coverage, Fiber-to-the-Home (FTTH) and Fiber-to-the-Business (FTTB) service providers often install compact Optical Network Terminals (ONTs) deep into subscriber homes and offices. This equipment can clash with the existing décor, upsetting customers, and also create deployment issues for installers. In fact, some customers actually cancel service orders when they realize that unsightly, conventional fiber optic cables or tapes will be installed in their homes. On top of this, tight spaces, corners, architectural features, and other factors can create barriers to indoor optical fiber deployments. Fortunately, the portfolio of InvisiLight Optical Solutions was specifically designed to help meet these challenges.

Launched in 2012, the original, award-winning InvisiLight ILU Solution offers installers an innovative and simple method for indoor optical fiber installation. The process involves adhering a 0.9 mm diameter optical fiber into either crevices along ceilings and walls or moldings and walls. The result is a protected optical fiber link that is virtually invisible.

While the InvisiLight 600 ILU Solution features an even smaller 0.6 mm optical fiber, it uses the same easy installation process and tools as the original InvisiLight Solution. And, with less than half the volume and weight, the InvisiLight 80×80 Module’s storage capacity is more than doubled from 10 to 25 meters (83 feet).

All InvisiLight products, including the ILU 600 Solution, feature leading-edge OFS EZ-Bend® Optical Fiber. This fiber’s 2.5 mm minimum bend radius easily handles the sharp corners often encountered when installers conform optical fiber to a building.

In fact, in a recent field trial in Europe, an InvisiLight Solution received excellent feedback, including:

We’re a big fan of EZ-Bend. I am amazed at some of the runs we have used it on with no apparent losses

(extreme bends, harsh pulls etc.).” – UK Service Provider

 

This is the best indoor solution we have seen. Adhesive and cable are very easy to work with. Cannot

believe the low loss measured. The end customer is impressed.” –  Large Ireland Network Services

Company and Ireland Service Provider

Rollable Ribbon Fiber Optic Cable Keeps on Rolling

Searching for a highly-dense fiber optic cable solution with a familiar, cost-effective central core design? Then look no further than the AccuRoll™ Dry Core (DC) Rollable Ribbon (RR) Fiber Optic Cable.

The newest member of the OFS outside plant (OSP) rollable ribbon fiber optic cable line, the AccuRoll DC RR Cable offers twice the fiber density of comparable, standard flat ribbon cables in a smaller and lighter-weight cable. And, this cable is the first and only central core rollable ribbon design that features familiar linear strength elements and a protective central core tube. This core tube delivers enhanced safety for the rollable ribbons beyond that offered by other flexible ribbon cables.

What Are Rollable Ribbons?                                                                                                                                                               The AccuRoll DC RR Cable features rollable ribbons, the most exciting technology breakthrough in OSP cabling in years. This technology literally doubles the density of a fiber optic cable while reducing that same cable’s size and weight.

Rollable ribbons are formed by partially bonding individual 250 micron optical fibers to each other at predetermined points. These flexible ribbons can be rolled into very tight bundles for twice the density. Inside the fiber optic cable, rollable ribbons behave much like traditional ribbons, allowing highly efficient splicing using traditional flat ribbon splicing machines and procedures. The rollable ribbons can also be easily broken out into single or multiple fibers and routed.

Why the AccuRoll DC RR Cable?                                                                                                                                                             As fiber counts rise, but duct space and cable storage remain at a premium, smaller, lighter weight, and more flexible rollable ribbon cables are an excellent alternative to traditional flat ribbon cable technologies.

Available with 144 to 432 fibers in both metallic and dielectric designs, there’s an AccuRoll DC RR Cable to meet the needs of your application. These fiber optic cables are an excellent choice for connecting data centers or in underground, direct buried, and lashed aerial deployments.

Think about it: doubling your network’s fiber density means doubling your transmission capacity, doubling your capability, and doubling your ability to get the job done.

Fiber Optic Solutions for the Home (FTTH)

Connecting the Home

Fiber to the Home (FTTH) is becoming increasingly more common as bandwidth usage is exploding. This tremendous growth is driven in part by the rapid increase in Internet-connected devices and the use of data-heavy applications such as video on demand. Service providers are working to meet this need for greater bandwidth by expanding the deployment of fiber optic cables to the premises and then into the home.

Service providers building these networks all face a common challenge: the expense of the last mile in the optical network. It is critical for service providers, utilities and municipalities to have an optimized set of deployment options that help to reduce both capital and operational expenses.

The solutions presented in this article meet these challenges with several fiber deployment options from the drop point to and into the home.

OFS FTTx Solutions for the Home can help residents take advantage of the Internet of Things (IoT), which is beginning to redefine how we work and live. These solutions focus on simplicity, cost-effectiveness and speed of installation, along with the pre- and post-installation customer experience, time to revenue generation and reliable subscriber connections that help to improve profitability for the service provider.

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PRE-TERMINATED vs. FIELD-TERMINATED DROPS

Pre-terminated drop solutions are increasingly used to install fiber to homes to save time and money in higher labor cost regions. Pre-terminated drop solutions consist of drop cables that are terminated and tested in the factory, and easily plugged into the drop terminal and home terminal in the field. Pre-terminated solutions offer lower costs and faster deployment and require less installation skill.

For low labor cost markets, field terminated solutions may be preferred. Field terminated solutions use drop cables which are terminated using fusion splicing or mechanical connectors in the field during installation. They offer easier inventory management, lower material costs and easier slack management, but take longer to install and require more highly skilled labor, along with expensive field termination tools and splicing machines, when compared to pre-terminated solutions.

A third approach, with one end of the drop cable pre-terminated, and the other end field terminated, can solve the slack issue and allow an easy plug-in to the drop terminal and field termination at the home.

OFS offers all three of these drop solution options to fit the unique needs of each service provider. OFS pre-terminated solutions are available with EZ- Bend® cables that can solve the slack management challenge. EZ-Bend fiber optic cables enable the slack to be tied into a very compact bundle.

Providers typically use a combination of aerial and underground solutions to connect the last mile in a network to individual homes. A variety of factors including climate and existing infrastructure can influence solution selection.

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CONNECTING OPTICAL FIBER TO THE HOME

OFS offers a complete portfolio of aerial and underground solutions including terminals, integrated splitters and drop cables to connect to the demarcation point of individual homes. From that location, a number of solutions can be leveraged to take optical fiber into the home.

Aerial deployment is typically lower in cost and preferred where poles are in place near homes. In this scenario, a SlimBox® Drop Terminal is installed on a pole, with or without splitters, and then connected by a drop cable to as many as 16 homes. Below grade drop deployment is preferred if there is an existing duct placed from the terminal location to the home, or if below grade cabling is required by local regulations.

First, an installer inserts a feeder or distribution cable into the terminal. The installer then extracts the number of fibers required and fusion splices them to a pre-terminated splitter or drop fiber. Aerial or underground drop cables are then deployed from the terminal to individual residences.

In the case of aerial cables, a drop cable is placed between the pole and a point near a home’s roof. The cable can be connected to a demarcation box and installed into the home through the attic or onto the side of the house at a demarcation box near the ground. To help avoid unsightly aerial cables, an aerial terminal can be connected to an underground drop cable. For aerial deployments, OFS offers the one to 24-fiber Mini LT Flat Drop Cable and the single-fiber Mini TB Flat Drop cable which contains 3 mm cordage that can be routed directly to an Optical Network Terminal (ONT).

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Underground drop cable options include the single-fiber EZ-Bend® 3.0 mm and 4.8 mm Ruggedized Cables and EZ-Bend Toneable Cables. The toneable cables enable easy above ground locating of buried cables to help avoid cable cuts when other underground systems are installed. These drop cables are installed from the aerial terminal down the pole to the ground, and are then buried to minimize disruption to landscaping, or pulled into existing duct. The cable is then connected into a demarcation box installed at the side of the house, ideally in a location close to the ONT on the inside.

EZ-Bend cables are preferred since their 2.5 mm bend radius allows the cables to be coiled, bent and tied without creating signal degradation. These cables can also be buried or stapled/clipped and bent around the outer perimeter walls of a home to reach an entry point closer to the preferred ONT location.

New home construction offers a win-win situation for construction companies and service providers. With the ability to “build in” optical fiber connectivity, new homes are futureproofed from the beginning, real estate values increase, and new home owners can become immediate subscribers without the expense of additional installation time. .

Subscribers can be connected faster using preterminated cables installed to and into homes during construction. OFS offers EZ-Bend 3.0 mm and 4.8 mm cables that can be installed independently or in ducts using typical home wiring techniques, such as stapling or zip-tying of the cables, to a location or media panel where the ONT would be later placed. The home owner can later perform a “self install” by receiving an ONT from the service provider, and simply plugging in an EZ-Bend cable assembly and a power adapter to the ONT. OFS also provides a SlimBox Wall Plate that discretely blends into a home’s décor and facilitates ONT connections in the same way as a power outlet.

Existing Homes can pose a challenge to network installers, given the wide variety of possible building architectures. In addition, home designs and construction materials can vary greatly from country to country and even within countries. OFS solutions are purposefully designed and optimized to suit a variety of homes globally and offer maximum flexibility to on-site installers.
Depending on the target market, a provider can choose the terminals and drop cables for an aerial, underground or hybrid solution. The solutions described are the most popular options and feature a variety of products as building block components. This modular product design approach allows service providers to also create custom solutions to meet the specific needs of their target markets.

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