OM5 360x203It might sound antiquated to be called a name that applies to British sailors of old, but that name now carries a new connotation. No, it’s not related to the practice of eating limes to prevent the vitamin C deficiency known as scurvy, but it is related to that citrus fruit’s color.  You see, lime has just been standardized as the name and color for OM5 indoor cables.

At the January TIA TR-42 meeting, the optical fiber and cable subcommittee, TR-42.12, approved an addendum to the ANSI/TIA-598 color code standard making the color official. The decision came after just two ballots, with the approved document achieving publication authorization without dissention.  It will be published as ANSI/TIA-598-D-2 Optical Fiber Cable Color Coding – Addendum 2, Jacket Color for OM5 Indoor Fiber Cables.

So, what color is lime exactly?  After all, the name lime connotes a range of green shades.  To those who understand the nuances of color names, this lime is actually often called chartreuse.  If that fancy name does not conjure up a firm image, then think of the color of tennis balls. You know, that bright yellow-green that makes them so easy to see. 

But to be more scientific, all the colors defined in the ANSI/TIA-598 specification are defined using the Munsell color system.  The Munsell color space has three dimensions:

  • Hue refers to the color shade, such as blue, yellow, red. 

  • Chroma refers to color intensity, or how vivid the color appears, with a minimum of 0 and a practical maximum of about 12.

  • Value refers to the lightness. In the absence of any chroma, a value of 10 equates to white and a value of 0 equates to black, with progressive shades of gray in between. 

CLICK TO TWEET: It's official! Lime is the new color for OM5. It's SO CommScope's color!

OM5 lime is defined with a narrow hue variation just one unit wide in the green-yellow range.  It has a narrow value variation on the bright end of the range, set between 8 and 9.  And it has high chroma, with a minimum of 8 and unlimited maximum.  All of this means that lime is well separated from neighboring colors of yellow and green, also defined in ANSI/TIA-598.  So, this lime is very distinctive.

CommScope proposed this color for OM5 to set it apart from its predecessors, OM3 and OM4, which are colored aqua for both cable jacket and connecting hardware.  Following this precedent, it would be most intuitive to have OM5 connecting hardware match its lime jacket.  That’s a decision to be made in the first addendum to ANSI/TIA-568.3-D, the fiber and component structured cabling standard, now in its second ballot.  

The new color distinction signifies that OM5 is the first multimode fiber cable with laser-optimized bandwidth characteristics specified to cover wavelengths in the 850 nm to 950 nm range in support of short wavelength division multiplexed applications, such as 40G-BiDi, 40G-SWDM4, 100G-BiDi, and 100G-SWDM4, each capable of delivering those high data rates over a single pair of fibers. This great advancement in transmission capacity of MMF makes me happy there is a new limey in town!


About the Author

Paul Kolesar

Paul is an Engineering Fellow in the Enterprise Solutions division of CommScope in Richardson, TX.  He received his BSEE degree from Pennsylvania State University and MSEE degree from Fairleigh Dickinson University.

Employed with Bell Laboratories from 1981 to 2001, Paul designed and developed PBX circuit packs and fiber optic multiplexers, and in 1988 assumed systems engineering responsibility for optical fiber structured cabling systems within the SYSTIMAX SCS business.  He actively contributes to the development of industry standards within ISO/IEC regarding structured cabling, IEC TC86 on fiber optics, IEEE 802.3 on Ethernet; and chairs TIA TR-42.11 on optical systems.  He holds issued and pending patents on optical patch-panel design, array connectivity supporting parallel transmission and high-speed multimode transmission.  He conceptualized and drove the standardization of laser-optimized multimode fibers now known internationally as OM3 and OM4 for which he received the IEC 1906 Award in 2011.  These fibers have been specified within Ethernet and Fiber Channel standards to support low-cost VCSEL-based transmission systems from 1 Gb/s to 100 Gb/s and constitute the vast majority of optical media installed in data centers today. 

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2 comments for "Call me a Limey"
Stephen Hodgson Thursday, March 15, 2018 10:15 PM

Finally Commscope acknowledge that the outer sheath colour is important! You were kicking & screaming when I raised Erika Violet for OM4 with you, carrying on like pork chops that "it isn't a standard" and perpetuating the confusion with OM3 aqua sheaths. Well at least you're embracing what the end customer needs to be ab able to easily identify what fibre is what.

Paul Kolesar Friday, March 16, 2018 5:35 PM

Stephen Hodgson,
I must say I never heard the colloquialism "carrying on like pork chops". It does bring strange images to mind.
Putting that aside, neither the structured cabling standards nor the color coding standard dictate any color as normative. In other words, all sheath colors associations in ANSI/TIA-598 are informative in nature, so a customer is free to use what ever they wish. The color associations are for guidance and have been selected to delineate different fiber types by feature differences. For example, the colors delineate multimode fibers based on these features:
slate (gray) - 62.5um core
orange - 50um core, non-laser optimized
aqua - OM3 and OM4 (50 um core, 850 nm laser-optimized)
lime - OM5 (50um core, 850 nm to 950 nm laser-optimized a.k.a. wideband).
The reason the standard did not associate a different color for OM4 compared to OM3 is because the difference between them is the minimum modal bandwidth, which is not considered a feature. Here's why. Prior to OM3, there were many different bandwidths of MMF cable in the market. In fact, at that time IEC's MMF specification contained discussion of six bandwidth grades of 50um fiber and six of 62.5um fiber. We would have run out of color associations if we had tried to assign a unique color to each of these. Therefore we followed precedent by not changing the color association between OM3 and OM4. But OM5 adds a new feature with its wideband specification, thus its new color lime.
I'm glad that a new color will be helpful to you. Thanks for your comment.
Paul Kolesar

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