The digital age left City Hall behind for about 12 hours between Sunday and Monday after a fiber optic glitch shut down the citys phone and computer network. 
    
An exact cause is not yet known, but Alexandria IT Director Tom Trobridge believes the outage likely stems from a problem with a strand of fiber optic cable. When information transmitted by light cant pass through the glass fiber optic strands the system crashes, he said. 
    
Technicians monitoring the citys networks noticed the outage about 11:30 p.m. Sunday, officials said. They alerted Comcast, which owns and manages the cable infrastructure, and the citys network was switched to another fiber optic strand. Phones and computer services, like payroll, accounting and budgeting were up and running by 11:30 a.m. Monday.
    
They just switched to a different light wave on existing fiber in the ground, Trobridge said. It was a hardware failure and thats about it.
    
Most city-owned buildings were hit by the outage, Trobridge said, but essential services like 911 calls or computer-aided dispatch were not affected. The cable in question is about 15 years old and approaching the average lifespan for fiber optic equipment, he said.
    
Vibrations over time, like cars passing above buried cable or temperature changes, can bend the fiber optic strands, Trobridge said. Eventually, they can clog and fail.