The telco, which carries an AAA (lka) rating from Fitch Ratings Lanka, also has a share in Sri Lanka's cellular market through its subsidiary Mobitel.
Until the cable was commissioned this month, bilateral traffic of 600,000 minutes per month was routed via more expensive satellite links.
The undersea cable is a 20 million US dollar joint venture between Sri Lanka Telecom, owned by Japan's NTT and the government of Sri Lanka and the Maldive state telecom firm, Dhiraagu.
"We expect call charges to fall," Sri Lanka Telecom Chief Executive Officer Shoji Takahashi said.
"In addition to Maldivians and tourists, Indian guest workers also generate international traffic."
Dhiraagu has a network spanning 20 atolls in the Maldive Islands offering fixed and mobile services with international roaming.
SLT is connected to India through an undersea cable with Bharat Sanchar Nigam and is also connected to the SEA-ME-WE backbone.
Officials say tariffs will start to fall fro