AUTO BREVITY | Fiber Optic Lamp Monitors

The use of fiber optics for high speed data transmission is the norm in today's world. Everything from broadband Internet service to high definition cable television to digital telephone transmissions are done over fiber optic lines. Even the medical community is utilizing fiber optics to perform tasks today. One might think that this is a relatively new technology, but it isn't.

The first utilization of fiber optics in automobiles was to monitor the operation of exterior lighting, specifically front headlamp and turn signal, and rear tail lamp, brake light, and turn signal operation. Fiber optic tubes were attached at the light body at one end so that the tube was very close to the light bulb itself. The tube transmitted light from the source (the bulb) through the tube to a monitor unit located in a position where the driver could see it easily, to which the opposite end of the tube was attached to a lens (often colored) to indicate light operation. Front monitors were normally mounted on the top of each fender, and rear monitors were mounted to the center of the rear package tray, just below the rear window (see Mark III image above), or to the roof of the car in the headliner area above the rear window or as part of the rear garnish molding. On convertible models, such as the 1971-1976 Cadillac Eldorado and 1967-1969 Chevrolet Camaro, the rear monitor units were actually attached to the rear seat back. The 1968-1971 Corvette had the jeweled indicators for both front and rear lights mounted in the center console, near the transmission shift lever.

When the light bulb wasn't illuminated, the tube had no light to transfer, so the corresponding jewel in the monitor remained dark. When the bulb illuminated, this light passed through the tube to the monitor. Brake lights and signals were proportionately brighter, and the jewels in the monitor brightened and dimmed according to the amount of light being passed through the tube from the light bulb.

The tubes were covered with a protective coating, and care in handling must be exercised, as a broken or bent tube loses its ability to transmit light. Sharp twists and bends had to be avoided, and as these tubes age, they are more prone to breakage, so they must be treated very gently if handled today.

Chevrolet was the first to introduce fiber optics in 1967. Called the Vigilite Monitoring System, it was made available mid-year on full size models, Chevelles, and Camaros as an option. Priced at $26.35 on 1968 Camaros, it was rarely ordered and as such NOS systems can sell for upwards of $1,000 today. Complete used systems command high prices as well, often approaching NOS prices. In fact, this option is so rare that records indicate just 117 Chevelles were equipped with the light monitoring system in 1967, and only 1,755 Camaros were so equipped in 1968. It was even less popular on the 1969 Camaro, with just 1,450 installations.

RPO (Regular Production Option) U46 Light Monitoring System reached its peak in 1968-1969 on Chevrolets, and was discontinued after 1970. Other full size and specialty Oldsmobile and Buick models during this time also offered the monitoring system. It was not widely seen on General Motors vehicles until the 1968 Corvette came equipped with standard monitors, which were a bit more extensive than those seen on other models, as even the license plate light was monitored. These were dropped for Corvette after the 1971 model year.

In 1971, Cadillac introduced them as an option on all models, accompanied by a low washer fluid warning light on the instrument panel that illuminated with windshield wiper use when the washer fluid level became low. The monitors became standard on all Cadillacs for a time in 1972, before they returned to the options list late in the year. Optional for 1973 and 1974, they were once again added to the list of standard features for 1975 and beyond.

When the new 1969 Continental Mark III was introduced in April 1968, it included a rear lamp monitor as standard equipment. There was no front monitor available, even as an option, on the Mark IIIs. A rear lamp monitor was also made available for 1968 and 1969 Ford Thunderbirds, and it too only monitored the rear lights, with no provision made for the front lights. At just $25.91, it was a very rare option on the Thunderbirds, and was discontinued after just two years, which is a shame as when the rear lamp monitor is coupled with sequential turn signals, it's a real sight to see in the rear view mirror!