Compact fibre-coupled displacement sensor


Fibre sensor in LISA mission

Technology abstract

A major research-led UK university has developed a compact optical fibre displacement sensor capable of tracking motion millions of times smaller than the width of a human hair. Originally developed as a candidate technology for ESA’s spaceborne gravitational wave detector, LISA, the sensor is highly adaptable and can be retrofitted to existing systems, making it ideal for applications where non-contact, high-precision measurements are required. 

This sensor is highly adaptable, low cost, and can be retrofitted, making it ideal for a wide range of precision displacement monitoring applications.

- Helen Rogerson -

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Technology Description

The fibre-coupled sensor head is extremely compact (1 mm diameter x 1 cm long) and comprises a fused taper onto a single-mode fibre, a partially reflecting surface, and a GRIN lens. Interferometric readout is obtained through a radio frequency modulation-demodulation scheme. The readout technique is an extension of the so-called Schnupp or frontal modulation scheme.
The compact nature of the sensor head and its passive nature (in that it has no electronic elements at the head) means it can be fitted to apparatus where access is limited and doesn’t disturb the system through significant heat dissipation. The sensor head is low cost and so multiple sensors can be deployed in an array, again increasing the usefulness of the sensor and allowing for angular readouts.
The sensor is capable of 10 picometre motion tracking. Sensor resolution is 0.4 nm per square root of Hz at 1 mHz, and is better than 0.01 nm per square root of Hz at higher frequencies. 
The team behind this offer – the Institute for Gravitational Research at the University of Glasgow – has a wealth of experience and knowhow in the area of interferometric measurement.

Innovations & Advantages

• High-precision displacement measurement capability
• Compact, non-magnetic sensor head
• Low power dissipation
• Resolution of 0.4 nm per square root of Hertz at 1 mHz
• Resolution better than 0.01 nm per square root of Hertz at higher frequencies
• Measurement range of centimetres for a surface centimetres away
• Significant expertise and knowhow in interferometric measurement

Current and Potential Domains of Application


  • Candidate displacement sensor aboard ESA's LISA (Laser Interferometer Space Antenna) spacecraft, capable of tracking motion to 10 picometres



  • Industrial automation – production control, quality assurance, process monitoring
  • Machine building – machine monitoring, maintenance
  • R&D – product and process optimisation, test bench