Lenterra Optical Sensor Interrogator (LOI) offers fast, high resolution interrogation of FBG or WGM sensors.

Measures wall shear stress, drag flow force, temperature, strain and viscosity.
  • Many test and measurement applications have environmental or physical constraints that make the use of electrical sensors unsafe, impractical, or unusable.
  • Lenterra’s Optical Sensor Interrogator (LOI) is a compact, robust, fast measurement unit removes those limitations and liabilities.
  • Designed for the high resolution interrogation of optical sensors (Fiber Bragg Grating or Whispering Gallery Mode) in laboratory or industrial environments, the LOI delivers high accuracy, long term stability, streamlined installation, and premium performance under the harshest environmental conditions.
  • LOI is controlled by a standard PC through a USB interface and utilizes fast, low noise Distributed Feedback diode laser with narrow linewidth for full spectrum scanning. Custom software is used to communicate with probes and process and store collected data.
  • Adjustable photodiode gains allow for measurement of returned light intensity in a wide dynamic range.
  • Although designed for use with Lenterra’s in-line, real-time DFF and RealShear™ sensors, the unit can be used with third party FBG or WGM based optical sensors.

Typical results:

Ordering information:

Download Specification Sheet (PDF)


Model LOI-2F LOI-4F
Mechanical, Environmental, Electrical Properties
Length 40 cm (15.5″) 47 cm (18.5″)
Width 30 cm (11.7″)
Height 10.5 cm (4.2″)
Weight 4.7 kg (10.4 lbs) 6 kg (13.2 lbs)
Voltage requirements 100-240 VAC @ 47-63 Hz
Operating temperature From 0°C to 40 °C
Storage temperature From -10 °C to 50 °C
Optical Properties
Light source DFB diode laser
Central wavelength 1540-1560 nm
Linewidth, FWHM <10 MHz
Scan range:
via laser temperature1 3.7 nm
via laser current1, 2 1.2 nm
Scan rate:
via laser temperature1 0.1 nm/s
via laser current1 from 0.33 nm/s to 650 nm/s
Scan frequency (via laser current)3 from 0.25 Hz to 500 Hz
Wavelength increment1
at 0.25 Hz 0.8 pm
at 10 Hz 0.8 pm
at 100 Hz 0.7 pm 1.6 pm
at 500 Hz 2.9 pm 5.4 pm
FBG spectrum tracking repeatability1,4
at 0.25 Hz 0.5 pm
at 10 Hz 0.3 pm
at 100 Hz 0.2 pm
at 500 Hz 0.4 pm
Number of optical channels 2 4
Connector Duplex LC/PC Two FC/APC
Photodiode amplifier gain 105, 106, 107 V/A
Data Processing Capabilities
Interface USB
Software type LabVIEW based data acquisition and control software
Software capabilities Spectra recording, spectra averaging, spectra tracking, differential spectrum
(between channels 1 and 2) tracking, data logger, instrument control
Download Optical Sensor Interrogator Specification Sheet (PDF)

1Typical, actual values vary
2At 10 Hz scan frequency
3Custom orders for frequencies above 500 Hz
4One sigma

Specifications are subject to change without notice