Measurement of Birefringence of a Polarization-Maintaining Fiber Using a Gain-Switched Distributed Feedback Laser with Delayed Optical Feedback

Abstract

We propose a simple method for measuring the birefringence of a polarization maintaining fiber (PMF). Our method is based on measurements of the spontaneous emission noise intensity variation in a gainswitched distributed feedback semiconductor laser with delayed optical feedback. The optical lengths of the PMF along both the fast and slow axes were measured separately with a resolution of 20 μm. From the measured optical lengths, the ratio of the birefringence to the refractive index of the fast axis was estimated to be (2.217 ± 0.012) × 10‒4. We checked the validity of the estimated value by comparing it with the measured value of (2.2452 ± 0.0002) × 10‒4 in a conventional method using a Sagnac interferometer.