Comparing Open Path Technologies

Three companies currently sell and service TDL lasers in the USA for open path HF monitoring. They are Boreal Laser, Senscient, and NEO. Boreal Laser by far has the most HF experience and installations in operation. Neither of the other manufacturers have a permanent HF safety perimeter installation in the USA. All three require substantially stable structures and may be susceptible to light level failure modes from beam or alignment disruption. Beam block is best managed first by design in locations, mounting structures, and data filtering.

Boreal Laser

Boreal Laser offers a multichannel system specifically designed for perimeter and area monitoring around HF Alkylation operations. The system is a bistatic configuration (transceiver/reflector – two light passes are made through the sample space). The analyzer is located at a central location. Cables carry the laser to the transceiver and optical path, and return the detector signal to the central analyzer.

Advantages include:

  • There is usually no power required at the transceiver location
  • There is one primary analyzer service point located in a stable controlled environment
  • Stable structures and alignment are required at just one end of each path
  • System data interface is consolidated at one analyzer for up to 8 paths
  • Cost effective for multiple path systems
  • Adaptable to various applications with one analyzer using a variety of path components

Disadvantages include:

  • There is a single point failure potential
  • Less cost effective for 1-2 paths in many applications


The Senscient product is a single path bistatic configuration (transmitter/receiver – one light pass through the sample space). Power is required at both ends of the path, and data connection to at least the receiver end.

Advantages include:

  • Some redundancy for multipath systems
  • Cost effective for 1-2 path systems or widely dispersed locations

Disadvantages include:

  • Path distance limited to 60 meters by specification
  • Power required at both ends and data at one end
  • Critical alignment required and substantially stable structures needed at both ends
  • Dispersed maintenance and data retrieval
  • There are no known proven continuous HF installations


NEO products published include is a single and multi-path systems with monostatic and bistatic product designs. These are relatively new products with no proven installation base and limited product information.

Advantages include:

  • Some redundancy for multipath systems
  • Cost effective for 1-3 long path systems or dispersed geographies

Disadvantages include:

  • Dispersed maintenance and data retrieval
  • Tends to be expensive for multipath systems

Sensor System Reliability

The effectiveness of safety sensor systems can be estimated based on likely release scenarios, sensor characteristics, and sensor system reliability and design. ISA has developed guidelines for this analysis and services are available to evaluate system reliability. This is the basis of the Kenexis software.

The overall reliability of the system lies strongly in the reliability and resulting credibility of the sensors, their placement and maintenance to work with operations, and the management of operators’ understanding and confidence, and effective representation of the sensor information to the users. This is accomplished by well integrated system design and implementation from concept to maintenance.