Dual Wavelength Differential Detection of Fiber Bragg Grating Sensors with a Pulsed DFB Laser

Abstract

We show how dual wavelength differential detection can be used to measure fiber Bragg grating sensors using nanosecond pulses from a single DFB laser diode, by taking advantage of its dynamic chirp. This can be performed in two ways: by measuring the reflected power from two separate pulses driven by two different currents, or by taking two delayed digitized samples within a single pulse. A prototype instrument using fast digitizing and processing with an FPGA is used to characterize the chirp, from which the performance can be optimized for both measurement schemes.

Keywords

• fiber Bragg grating
• fiber optic sensor
• dynamic chirp
• DFB laser