Sheath-marking efforts elude harmonization

By WILLIAM B. GARDNER

"Harmonization" is a frequently stated objective in standards work. It refers to the laudable goal of ensuring that consistent standards emerge from the various standards bodies. Harmonization can be elusive if there is inadequate liaison and little overlap among the participants in the various committees. The evolution of sheath-marking standards illustrates the difficulty of achieving complete harmonization.

In the 1970s, the infant fiber-optics industry followed the Bell System`s practice of using white markings on black cable sheaths. If the original markings needed to be revised, the re-marking was done with yellow characters. This white and yellow standard was codified in Bell Communications Research`s (Bellcore`s--Morristown, NJ) tr-nwt-000020, "Generic Requirements for Optical Fiber and Optical Fiber Cable," Section 5.2. This practice was recently reaffirmed in Bellcore`s new Generic Requirement gr-20-core, Issue 2, March 1998.

An alliance called the Utility Location and Coordination Council recognized the need for a more comprehensive color scheme for buried plant. The council`s Uniform Color Code proposed orange markings on communications cables; red on power cables; yellow on gas, steam, and petroleum pipelines; blue on water lines; and green on sewers and drains. Unfortunately, the choice of orange didn`t harmonize with Bellcore`s Generic Requirement. Also, orange markings can turn brown over time. Fading isn`t a problem with white markings, since the titanium dioxide commonly used for this color is a notably stable pigment. The Uniform Color Code is voluntary and hasn`t gained universal acceptance for buried cables.

On the other hand, the Rural Electrification Administration`s PE90 standard is close to harmonization with Bellcore, since it prescribes white or silver markings, with yellow re-markings.

Meanwhile, a new issue of "icea Standard for Optical Fiber Outside Plant Communications Cable," ansi/icea S-87-640-1998, is now in draft form. It is a joint effort between the Insulated Cable Engineers Association (icea), which played the lead role in developing the draft standard, and the Telecommunications Industry Association`s Subcommittee FO-6.7 on Fiber Optic Cable. This document specifies "contrasting colors" without (so far) naming the colors. Part of the hesitation in choosing colors is due to anticipation of innovative marking methods. Lasers, for example, could create almost unlimited possibilities for texts, symbols, logos, etc., and the markings would be more permanent than inks. But lasers can create only a few colors (perhaps brown and gray).

What information do the cable markings contain? According to Bellcore`s gr-20-core, the name of the manufacturer and date of manufacture shall be indicated on each cable length, along with length markings. Another Bellcore document, sr-nwt-002014, contains the more elaborate Standard Optical Cable Code, which has not yet gained universal acceptance.

Meanwhile, the ansi C2 Committee recognized that an absence of harmonization could lead to confusion when contractors encounter black-sheathed cables in the field. So they created a new clause in the National Electrical Safety Code that mandates an identifying symbol on cable sheaths. For power cables, the symbol is a lightning bolt; for communications cables, it is a telephone handset. While debate over colors continues, these two symbols have gained widespread acceptance, both in the United States and abroad. q