Fidelity Investments, the biggest U.S. mutual fund company, Monday announced the launch of an Advisor municipal bond fund designed to help meet the income needs of investors with intermediate to long time horizons. With the launch of Fidelity Advisor Intermediate Municipal Income Fund, Boston-based Fidelity now offers 82 Advisor funds, including three national municipal bond funds with varying degrees of interest rate sensitivity. Doug McGinley manages the new fund.