ANDOVER, Mass., Aug. 23 -- Quantum Bridge Communications Inc. has signed a $50-million agreement to sell its Quantum Bridge Optical Access System. Advanced TelCom Group Inc., a provider of Internet and telephone services based in Santa Rosa, Calif., has agreed to purchase the systems over a three-year periodAdvanced TelCom will offer its 18,000 customers a wide range of high-bandwidth voice and data services over its fiber-based access network with the Quantum Bridge Optical Access System, the company said. ATG is focused on providing superior customer-centric service offerings to business customers in the markets we serve, said Curt Wheeling, co-founder andchief technology officer at ATG. The Quantum Bridge Optical Access System represents a highly affordable solution for delivering fiber to businesses withhigh-bandwidth e-commerce and data applications. This enables ATG to deliver a wealth of services to all its business customers regardless of size.