A high-speed acoustic data acquisition system using mostly COTS components

A data acquisition system has been developed at the Marine Physical Laboratory for recording digitized and multiplexed data from a variety of acoustic arrays and sampling systems. This system is composed of an industrial Pentium III CPU, a GPS time/frequency processor, a gigabit Ethernet interface, a high-speed parallel interface and a custom telemetry interface in a Compact-PCI chassis. A reconfigured version of this system could potentially fit into an eight inch diameter pressure case for autonomous deployment at sea. Control and programmability are provided by LabVIEW running under Windows NT or XP. The combination of the custom telemetry interface and high speed parallel interface provides a flexible, bi-directional channel for multiplexed serial data through coax or fiber at telemetry rates up to 200 MBaud. The custom telemetry interface can be reconfigured for a variety of existing and future telemetry systems utilizing coax and single or multimode fiber. The design of this interface exploits recent transceiver technology that exists for high bandwidth communication applications such as Fibre-Channel and ATM. This commercial technology provides the serializing/deserializing, coding/decoding, bit synchronization and byte framing required for the high-speed fiber link and can be operated synchronously or asynchronously using on-chip FIFOs. Data is recorded by the acquisition system in a standard format that does not require the translation usually required with proprietary data recording systems. Tests have shown that continuous data recording rates as high as 20 Mbytes/sec would be possible using high performance disk arrays. During a recent acoustic experiment off the coast of San Diego, data was recorded from a 128 element transducer array at a rate of 6.5 Mbytes/sec. The data was simultaneously moved via FTP over gigabit Ethernet to a UNIX workstation for archiving to DLT tape, allowing the acquisition system to record continuously for several days. The con figuration of this system and performance during the recent experiment is described, as well as other current and potential future applications.