What Is an DFB-LD (Distributed Feedback Laser Diode)?
Overview
A DFB-LD (including DFB-type semiconductor laser) is a laser that utilizes the Bragg reflection of a diffraction grating formed along an active waveguide to unify the laser longitudinal mode. It provides high wavelength stability and narrow linewidth. Setting the pitch of the diffraction grating enables the required wavelength to be obtained.
DFB-LD schematic
Example DFB-LD spectrum
A DFB-LD is mainly used as the optical signal for high-capacity long-distance optical communication, as well as a wide range of new applications such as fiber sensing, 3D sensing, gas sensing, and disease diagnosis such as respiratory and vascular monitoring. In the field of gas sensing, it is used as the light source for gas sensors that detect methane gas leaks around factory pipes.
Anritsu provides DFB-LD with wavelengths from 1,270 nm to 1,742 nm, which have been used in various applications.
Anritsu DFB-LD modules comply with the RoHS directive. The module has a 14-pin butterfly shape and includes TEC for temperature control and PD for optical output monitor.
Features
- Optical output examples: 80 mW, 1,310 nm/40 mW, 1,550 nm/10 mW, 1,653 nm
- Single longitudinal mode
- Wavelength range: 1,270 nm to 1,742 nm
- Fiber: Single mode fiber (SMF)
- Optical connector: Supports various optical connectors
- 14-pin butterfly package
- Includes optical isolator, monitor photo diode, and cooler
Optical Sensing for Industry >
Measuring Gas with Light (Methane Gas Sensing) >
Applications
Gas Sensing
Gas sensor (gas detector):
Gas detectors use TDLAS (Tunable Diode Laser Absorption Spectroscopy) that emits a laser to detect gas. Gas molecules have unique infrared absorption spectral lines. A gas sensor passes laser light with a wavelength that matches the absorption line of the gas for measurement through the gas and modulates the drive current at high speed to sweep the wavelength. The gas sensor then measures the transmitted light intensity to measure a single independent absorption spectrum and thereby performs gas detection. The laser light of a DFB-LD is optimal for a gas sensor because its wavelength needs to match the absorption line and the oscillation linewidth needs to be narrower than the absorption line.
The absorption spectrum of methane gas is indicated below. The 1,653 nm absorption spectrum is often used for gas detection with the TDLAS method because it has sufficient absorption intensity and there is no other gas absorption spectrum nearby.
Anritsu provides 1,653 nm DFB modules for methane gas sensors.
We also have experience providing modules with different wavelengths for other gas sensors.
Optical Sensing for Industry >
Measuring Gas with Light (Methane Gas Sensing) >
