Verification of Laser Phase Error Measurement Using Speckle Analysis in Coherent Fiber Reflectometry

Phase error variance is an important figure in many laser applications such as coherent optical communication and interferometric optical diagnosis and is directly related to system performance. In this letter, we show that the phase error variance of a single-mode laser with a narrow linewidth can be measured as a function of relative delay without using any reference (local) beam. In addition, the results are in good agreement with those measured using the beat note of two identical lasers, one of which acts as a local beam. The new method, uniquely we believe, enables us to evaluate the phase error variance of lasers at continuous delays without using any reference (local) beam.