It's the Mark 48 Mod 7 Common Broadband Advanced Sonar System (CBASS)
"A followon version of the Mark 48 Mod 6 guidance and control hardware, called the Advanced Common Torpedo Guidance and Control Box (ACOT-GCB), will be introduced in FY05 in order to replace obsolete components. ACOT-GCB parts will be incorporated into the next-generation torpedo, the Mark 48 Mod 7 Common Broadband Advanced Sonar System (CBASS), planned to start testing in FY05. The CBASS torpedo is being developed as part of a cooperative program between the United States and Australia. Several software builds are currently under oversight. Block III upgrade is the final tactical software upgrade to the Mark 48 Mod 5. Block IV extends Block III capabilities and applies them to the Mark 48 Mod 6 weapon. The more sophisticated CBASS software follows the Block IV. In lieu of future Block upgrades, the program plans to employ a series of advanced processor builds (APBs) to both the Mod 6 and CBASS weapons as a more flexible means of introducing software changes."
Here's a link I found:
http://www.defence.gov.au/dmo/msd/sea1429/sea1429.cfm