Technology White Paper Physical Layer Switch Simultaneous Processing and Recording of High-speed Sensor Data Introduction The Sensor Application Environment Surveillance and intelligence gathering applications demand sensors that generate high-speed, continuous data streams. Common sensor types include radar, sonar, infrared (IR), forward-looking IR (FLIR) and video. This raw sensor data must be processed at wire speed by Digital Signal Processors (DSPs), which transform the data into information that can be understood and analyzed by a human operator. During development of these high-speed sensor systems, a data recorder is often used in the lab to capture sensor data. The data is then played back repetitively to the DSP. This allows development engineers to fine tune the DSP algorithms. Deployed high-speed sensor systems pose different problems than in the lab. In deployed applications the data needs still to be sent to the DSP for processing in real-time. At the same time the high-speed sensor data needs to be recorded and archived for subsequent analysis and evaluation. How can high-speed streaming sensor data be simultaneously processed while also being recorded? The physical layer switch makes this possible. The Physical Layer Switch A Physical Layer Switch (PLS) is a hardware device that performs like an electronic patch panel. Users can send a command to a PLS to change connections without moving cables. The PLS handles data at the physical (PHY) or first layer of the OSI model of network architecture. Also known as a Layer 1 Switch, a PLS acts like a wire or cable on the hardware level, and therefore is not aware of and has no influence on the actual protocol or routing information contained within the data stream. The PLS is a non-blocking switch enabling the connection of any input to any output. The physical layer switch has the ability to copy input signals to multiple outputs. The single source of high-speed sensor data is brought into the PLS, and simultaneously sent to a data recorder, DSP, monitor, or other device. This key attribute makes the PLS a necessary component in any high-speed sensor application that requires data recording. Figure 1: Curtiss-Wright GLX4000 Page 1
Sensor Protocols Today s sensor applications use a wide range of highspeed protocols to transport the data to the DSP. The most common protocols are sfpdp, GbE and 10 GbE. The PLS supports all of these protocols. Serial Front Panel Data Port (sfpdp) VITA 17.1-2003 standard. Serial FPDP is a high-speed, low latency data streaming serial communication protocol that is widely used in the sensor market. Serial FPDP runs at 1.0625 and 2.5Gbps link rates and can operate over long distances (up to 10 km) using single mode fiber optic cable. Gigabit Ethernet (GbE). GbE is a widely accepted, inexpensive protocol that runs at 1.25Gbps over copper wire or fiber optic cable. GbE is also commonly used because of its ease of implementation and wide support. 10 Gigabit Ethernet (10 GbE). 10 GbE is an emerging high-speed sensor protocol running at 10.31Gbps over fiber optic cable. Its faster data rate makes it an ideal protocol for future high-speed sensor systems. In addition to providing higher speed, multiple GbE data links can be aggregated on one 10 GbE data link to reduce the number of cables to transport data. This is particularly attractive when long transmission distances are involved (toward sonar, aerostats, and remote radar). Recording Sensor Data In high-speed sensor systems, both lab and deployed, a data recorder is needed that can record the data at line speed without slowing the sensor down. As noted in the previous examples, the most common high-speed sensor protocols are sfpdp, GbE and 10 GbE. Curtiss- Wright Controls Electronic Systems family of Vortex Data Recorders has high-performance data recording solutions for these high-speed protocols. Figure 2: Vortex Data Recorders PLS Makes Recording Possible In high-speed sensor systems it is critical that you are able to copy data to a recorder without slowing down the sensor. The PLS allows the high-speed sensor data to be copied to multiple outputs. For sfpdp, GbE and 10 GbE sensor applications a PLS makes data recording possible. Page 2
Figure 3: sfpdp Applications sfpdp Sensor 1310nm 1 km GLX4000 Physical Layer Switch Digital Signal Processors 1 m 850nm 2 m Optical single-mode cables Optical multi-mode cables Copper cables Distance VR6211 sfpdp Data Recorder A sensor is sending its collected data using the VITA 17.1-2003 sfpdp protocol. Multiple channels are used, as is typical for transporting such large amounts of sensor information. The PLS makes the copying of the data to a sfpdp recorder possible. The recorded sfpdp data can then be played back through the PLS and sent to the DSP. In this application the PLS also conveniently converts the 1310nm media to other media types while copying. Page 3
Figure 4: GbE Application VLX2500 GbE Physical Layer Switch GbE Camera 1 Display 1 GbE Camera n Display n GbE Video Streams 1 - n SDRxE GbE Data Recorder A common sensor application is acquiring video images. In this scenario cameras collect data and send it via streaming GbE to a display. This data also needs to be recorded for post-session analysis. A PLS makes this possible. A PLS can copy the GbE data at line speed to multiple outputs. In the above application the GbE video data is being passed through the PLS to displays, while also being simultaneously sent to a recording device. Page 4
Figure 5: 10 GbE Application RT10000 10 GbE Physical Layer Switch Digital Signal Processor 10 GbE Sensor ABC...XYZ ABC...XYZ SDR1X 10 GbE Data Recorder Copyright 2009, Curtiss-Wright Controls Electronic Systems All Rights Reserved. MKT-ES-PhysicalLayerSwitch-010410v1 Next generation sensors require higher speed protocols such as 10 GbE. At these speeds copying the data is very difficult. The PLS makes it possible to copy the data to a data recorder. The PLS does this at line speed without slowing the sensor down. Page 5