What Is a Wavelength Swept Light Source?
Overview
A wavelength swept light source emits laser light with a continuously sweeping wavelength. It is suitable for shape
measurement and displacement measurement utilizing OFDR (Optical Frequency Domain Reflectometry), an optical sensing
method using the coherence of laser light. The OFDR method is also widely known as the FMCW (Frequency Modulated
Continuous Wave) method.
Wavelength swept light sources are utilized as light sources for sensing in a wide range of fields, such as precision
measurement, vibration measurement, surface inspection, industrial applications such as OCT, medical applications such
as ophthalmology OCT and intravascular OCT, infrastructure/plant measurement applications such as
displacement/fluctuation of large structures, and length measurement.
The wavelength swept light sources of Anritsu provides high-coherence wavelength swept light by performing continuous
and mode hopping-free wavelength sweeping on a single longitudinal mode with narrow linewidth. These swept light
sources can be used to measure with wider distance and higher precision.
Anritsu wavelength sweep light sources improve the standard Littman arrangement with a unique optical arrangement so
MEMS scanning mirrors can be used to achieve high-speed wavelength sweeping. In this optical system, the area from the
effective cavity end facet to the reflection surface of the MEMS scanning mirror is comprised of an external cavity,
and of the multiple vertical modes determined by the cavity length, only one mode obtained by the wavelength
selectivity of the diffraction grating is selected for oscillation.
Overview of Anritsu wavelength swept light source
The graph below schematically depicts the wavelength selectivity of the diffraction grating caused by the rotation of
MEMS scanning mirror, and how the selected oscillation mode changes.
Oscillation mode changes of Anritsu wavelength swept light sources
Features
- Center wavelength : 1,550 nm (It can also support 1060 nm)
- Sweep frequency : 150 Hz*1 or 1,250 Hz*2
- Wavelength sweep width : 15 to 70 nm*1 or 30 to 110 nm*2
- Average optical output power : 10 mW or more
- Oscillation mode : Single longitudinal and mode-hop-free
- Coherence length (reference value) : 100 m or more*1 (Δλ=25 nm), 10 m or more*2 (Δλ=30 nm)
*1 AQB5500P/AQB5500D
*2 AQA5500P/AQA5500D
Note; This product does not comply with the EAC requirements.
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Applications
Precision Thickness Measurement
- Optical component thickness measurement: Measuring the thickness of transparent objects such as glass and lenses
- Thickness measurement and surface roughness measurement of film and steel plates
- Thickness measurement of semiconductor wafers
Vibration Measurement
- Rotating body vibration width measurement: Measuring the eccentricity and surface run-out of drills and disks,
etc.
- Vibrating body vibration width measurement and frequency measurement: Speakers, etc.
Surface Inspection
- Inspecting workpieces for burrs and scratches
- Fine bump measurement of solder surfaces
OCT (Optical Coherence Tomography)
OCT utilizes optical interference to perform tomography on the inside of objects and human bodies and can also be
used with beam scanning to measure three-dimensional structures in detail. It utilizes near infrared light to perform
non-destructive and non-contact imaging, which is used for inspecting thin film products for defects and inspection
for ophthalmological treatment.
OCT for Industry
- Thickness measurement of resin/plastic products and inspection for bonding areas
- Thickness measurement of semiconductor wafers
OCT for Medicine
- Eye axial length measuring instrument (biometer)
- Intravascular OCT: Higher resolution tomography than IVUS (Intravascular Ultrasound)
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FAQ about Wavelength Swept Light Source >
FAQ about OFDR >
