Fixed-income exchange-traded funds are all the rage.

Vanguard said Wednesday it has filed plans with the Securities and Exchange Commission to offer exchange-traded shares for four of its existing bond mutual funds: the ( VBMFX) Total Bond Market Index Fund , ( VBISX) Short-Term Bond Index Fund , ( VBIIX) Intermediate-Term Bond Index Fund and ( VBLTX) Long-Term Bond Index Fund . The ETF share classes of each fund will carry an expense ratio of 0.11%.

The announcement comes as Barclays Global Investors launched eight fixed-income ETFs last week, ending a three-year drought for these kinds of products. Barclays, a unit of Barclays Bank ( BCS), is the biggest player in the U.S. ETF market with more than half of all assets under management and is currently the only firm that offers bond ETFs here. It now has 14.

Ameristock Funds also has five bond ETFs in registration, and other firms have said they are looking into them.

Vanguard is the nation's second-largest mutual fund manager with more than $1.1 trillion in assets, but is a relatively small player in the ETF industry. The 27 stock ETFs it currently offers have combined assets of about $22 billion.

"With Vanguard's equity ETFs gaining momentum in the marketplace, we look forward to broadening our offerings with a series of bond ETFs," Vanguard Chief Investment Officer Gus Sauter said in a statement.

"These four Vanguard bond ETFs will provide investors with broadly diversified exposure to the entire U.S. bond market and discrete segments of the market at an extremely low cost," he added.

Vanguard Total Bond Market is one of the largest bond mutual funds in the U.S., with some $40 billion in assets. It tracks the performance of the market-weighted Lehman Brothers Aggregate Bond Index and holds nearly 2,800 corporate, Treasury, agency and mortgage securities.

The three other bond funds that Vanguard will use as the basis for ETF shares are diversified funds that target specific maturity segments of the U.S. bond market.