CHATSWORTH, Calif. -  US Seismic Systems, Inc. (USSI), a subsidiary of Acorn Energy, Inc. (Nasdaq:ACFN), and Northrop Grumman Corporation (NYSE:NOC) have signed a licensing agreement involving several of Northrop Grumman's fiber-optic technology patents. Terms of the agreement are confidential. Northrop Grumman has an extensive portfolio of fiber-optic patents resulting from pioneering research in fiber optics spanning three decades. Northrop Grumman's licensed patents will be used by USSI in an ...