Sensing is technology for the non-contact quantitative measurement of objects in a remote location using a medium such as light, ultrasound, echoes, or X-rays. A typical example of optical sensing for industry is the measurement of temperature, vibration, and distortion via Stimulated Raman Scattering (SRS) inside optical fiber. In addition, emitted light can be used to measure thickness and surface roughness of an object because the time difference and wavelength of the scattered light that returns indicates the distance from the object.
Anritsu provides SLD (Super-Luminescent Diode) light sources, Wavelength Swept Light Sources, and DFB-LD (Distributed Feedback Laser Diode) light sources to use in optical sensing for industry.
An SLD light source provides output power equivalent to a laser diode and a wide oscillation spectrum width equivalent to an LED (Light Emitting Diode), as well as low coherence. Since it emits light with a narrow active layer equivalent to a laser diode, it is excellent for joining with optical fiber and can be used as the light source for measuring the thickness of objects (OCT).
A wavelength swept light source provides high-coherence wavelength swept light by performing continuous and mode hopping-free wavelength sweeping on a single longitudinal mode with narrow linewidth. Our swept light sources can improve position resolution and accuracy because they have a long coherence length that can expand their measurable distance up to 100 m, and the interference signal of OFDR can be measured with high SNR. In addition to medical OCT and film thickness measurement, this can be applied to OFDR for large structures, which requires longer length measurements.
A DFB-LD is a single longitudinal mode laser with narrow linewidth that has diffraction grating inside the laser diode. It is usually used as a light source for communication, but a DFB-LD with higher output can be used as a light source for gas sensing. For example, since a wavelength of 1,653 nm is easily absorbed by methane gas, the intensity of the 1,653 nm light reflected back can be observed to measure the gas concentration.
Some examples of the optimal applications for each light source are indicated below.
Optimal light source for length measurement: SLD, swept light source
- Industrial OCT (thickness measurement)
- Precision measurement (inspecting the uniformity of thin film, testing workpieces for burrs and scratches, atomic force microscopes)
- Vibration measurement (rotating body vibration)
- Infrastructure and plant measurement (displacement of large structures)
Optimal light source for position information measurement: SLD
- Displacement sensors
Optimal light source for confirming specific materials: DFB-LD
- Checking for hazardous substances such as methane gas
- Sorting plastics