A program to upgrade Vietnam's optical fiber network should open the way for a communications revolution in the country from 1996, including very-high- speed data transmissions and state-of-the-art television.

The upgrade and link with a regional project involving Thailand and Hong Kong is being undertaken in part by Australia's Telstra Corp. The firm, partly government owned, has a $200 million capital spending program in Vietnam.Telstra, which reckons it's the largest foreign investor in the sector, joined with the Ministry of Postal Service and Communications, the Communication Authority of Thailand and Hongkong Telecommunications Ltd. in the $173 million optical fiber project.

Installation of the submarine link between Vietnam, Hong Kong and Thailand will provide some 7,560 channels.

This project, along with the upgrade of the existing fiber optic cable, will give Vietnam "the capacity to offer more advanced services like online video, video on demand and very-high-speed data transmission," says Peter Allan, Telstra's Hanoi-based business manager.

The upgrade portion of the grand design focuses on the fiber optic cable between Hanoi, the coastal city of Danang and Ho Chi Minh City, the southern commercial center formerly known as Saigon.

Its carrying capacity will be boosted to 2.5 gigabytes from the current and ''very unreliable" 34 megabytes. This project uses technology from Canada's Northern Telecom Ltd., described as the world's latest.

The improved cable will be linked to five centers throughout the country providing a "very good, reliable, very-high-capacity backbone network throughout Vietnam," Mr. Allan told The Journal of Commerce.

Vietnam faces a capital investment of some $3 billion to meet projected communications demands to the end of the decade, he estimates.

Economists have pointed to the need to develop the underground cable network connecting cities and provinces as well as expansion of the domestic telephone network as priorities for general development.

"At the moment there are between 600,000 and 700,000 subscriber lines in

Vietnam. That is less than 1 percent penetration, or less than one telephone per 100 people," Mr Allan said.

The government has set a target of five telephones per 100 people by the year 2000.

Late last year, the target of a minimum one digital exchange in each of the country's 50 provinces was achieved. Now, "there is a big obligation to have at least one phone in every village," Mr. Allan said.

Linking often remote regions may also be done by satellite with a dish connected to telephone exchanges.