It 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.
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!