Optical-frequency encoder using polarization-maintaining fibre

A new method for monitoring the frequency modulation of coherent laser light is presented. The measurement system is an optical-frequency encoder which utilizes multireflection in a short polarization-maintaining fiber. The multireflection in each orthogonal polarization mode of the fiber produces beat signals by sweeping the optical frequency. The resultant two beat signals are monitored as an increase or decrease in optical frequency by holding the two signals in phase quadrature. The experimental setup, the principle for obtaining quadrature signals, and the results of monitoring distributed-feedback laser-diode frequency modulation are presented.<
>