A cutback method for measuring low linear fibre birefringence using an electro-optic modulator

A new cutback method based on the use of phase discrimination is proposed for low-linear-fibre-birefringence measurement. In this destructive method, a detection scheme for determining the phase difference between two readily obtained signals is used to give the phase retardation of the test fibre directly. The detection scheme mainly consists of two wave plates, two sections of fibre and an electro-optic modulator. The features of this measurement scheme are two-fold. First, the aforementioned phase difference between two detected signals, and, accordingly, linear fibre birefringence, can be determined in a simple manner, compared with the conventional cutback method. Second, the test fibre can be short in length despite the existence of fibre cladding modes. Experiments show that the proposed method can give a reliable measurement of linear fibre birefringence.