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Tag Archive: single-mode fiber

  1. Single-Mode Optical Fiber Geometries

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    Understanding Optical Fiber Specifications

    This article in our technical series will focus on single-mode optical fiber geometries.

    If you subscribed to our Light Post Emails you know we previously covered bandwidth demand drivers and introductory standards as well as fiber optic dispersion.In this article we’ll work our way through a typical fiber specification, highlighting the importance of various single-mode optical fiber geometry specifications.

    Optical fiber core specifications

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    Cladding (Glass) Diameter – 125.0 ± 0.7 µm

    Cladding diameter is the outer diameter of the glass portion of the optical fiber. For telecommunications fibers, this diameter has been 125 microns (µm) for a very long time. On the other hand, the diameter tolerance has not always been 0.7 µm.

    Core Alignment Splicer Type Specifications

    During the 1980s, optical fibers had outer diameter tolerances as high as +/- 3.0 µm. As you can imagine, matching up fiber cores ranging from 122 to 128 µm in diameter could result in extremely high loss. This situation is why fusion splicing machines required additional technology to help align the fiber cores. This extra technology increased the price of the splicing units.

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    Mode Field Diameter (MFD)

    Mode field diameter (MFD) is another specification related to fiber geometry. In a typical G.652.D compliant single-mode optical fiber, not all of the light travels in the core; in fact, a small amount of light travels in the fiber cladding. The term MFD is a measure of the diameter of the optical power density distribution, which is the diameter in which 95% of the power resides.

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    Clad Non-Circularity of d 0.7 %

    Clad non-circularity measures a fiber’s deviation from perfectly round, and is measured as a percentage difference versus perfect.

    Core/Clad Concentricity Error (Offset) of d 0.5 ¼m, < 0.2 ¼m typically

    Core/clad concentricity error (CCCE) measures how well the core is centered in the fiber. CCCE is measured in microns and, of course, the closer the core is placed to perfect center, the better it is.

    Although the difference between 200 and 250 µm is not tremendously large, smaller diameter fibers can enable twice the fiber count in the same size buffer tube, while also still preserving long-term reliability.

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    Fiber Curl

    What is optical fiber curl?

    Fiber curl assesses the non-linearity of bare glass. In other words, fiber curl measures how straight the glass fiber is when no external stressors are present. If imbalanced stresses are frozen into a fiber during the draw process, curl can result. This curl can show up during the splicing of fiber optic ribbons or when fixed V-groove splicing machines are used.

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    In closing, fiber geekdom is a journey, not a destination, and there’s always more to learn. OFS has multiple decades of experience with fiber-optic cable networks. Please contact your local OFS representative if you would like additional information regarding optical fiber geometry specifications.

  2. Choosing the “Right” Optical Fiber – Single-Mode or Multimode?

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    A huge increase in digital devices, cloud computing and web services have helped fuel the tremendous demand for increased bandwidth while also pushing datacom rates to 100G and beyond. With these faster speeds and greater use, system designers might assume that single-mode optical fiber holds a growing advantage over multimode optical fiber for premises applications. However, it’s critical to remember that increased Ethernet speeds don’t necessarily mean that single-mode fiber is the best choice.

    While it’s true that single-mode fiber holds bandwidth and reach advantages, especially for longer distances, multimode fiber easily supports most distances needed by data center and enterprise networks, and at a significant cost savings over single-mode fiber.

    What’s the Difference?

    These two optical fiber types were primarily named for the different ways that they transmit light. Single-Mode optical fibers have a small core size (less than 10 microns) and allow only one mode or ray of light to be transmitted. These fibers were mainly designed for networks that involve medium to long distances, such as metro, access and long-haul networks.

    On the other hand, multimode fibers have larger cores that work to guide many modes at the same time. These larger cores make it much easier to capture light from a transceiver, helping to control source costs.


    View our Single Mode vs. Multimode Fiber Guide

    WHICH Multimode Fiber?

    Today, network designers and end users can choose from OM3, OM4 or OM5 grades of 50 micron multimode fibers. At one time in the 1980s, as data rates increased, 62.5 micron fiber was introduced because it allowed for longer reach to support campus applications. However, with the advent of gigabit speeds, users moved back to 50 micron fiber with its inherently higher bandwidth. Now 50 micron laser-optimized multimode OM3, OM4 and OM5 fibers offer major bandwidth and reach advantages for short-reach applications along with low system costs.

    The Future

    Industry standards groups such as IEEE (Ethernet), TIA, ISO/IEC and others continue to recognize multimode optical fiber as the short-reach solution for next-generation speeds. In fact, TIA issued a new standard for the next generation of multimode fiber called wide band (OM5) multimode fiber. This new version of 50 micron fiber can transmit multiple wavelengths using Short Wavelength Division Multiplexing (SWDM) technology, while maintaining OM4 backward compatibility. This capability lets end users gain greater bandwidth and higher speeds from a single fiber by simply adding wavelengths. The OFS version of this fiber is LaserWave® WideBand (OM5) Optical Fiber.

    In Short…

    Generally, 50 micron optical fiber continues to be the most cost-effective choice for enterprise and data center use up to the 500-600 meter range. Beyond that distance, single-mode optical fiber is necessary.

    The OFS LaserWave FLEX Multimode Optical Fiber family offers full performance range and has better optical and geometric specifications than standards require. However, if the network’s transmission distance requires the use of single-mode optical fiber, consider bend-insensitive, zero water peak (ZWP) full-spectrum fibers such as the OFS family of AllWave® Optical Fibers.