Use of fiber helical coils to obtain polarization insensitive fiber devices

•Fiber pigtails are coiled to produce polarization insensitive devices.•These devices allow the development of systems with full control of polarization.•The device polarization sensitivity limits the polarization control.

Using a new model for the description of the birefringence of a helical coil, it is shown that the birefringence effect on the signal polarization introduced by a fiber device can be canceled out by introducing two helical coils at the required orientation. Experimental results obtained using this modification in a polarization insensitive device (optical isolator) and in a non-polarization insensitive device working at two different wavelengths (wavelength division multiplexer) are presented and discussed. Such modified devices were used in the construction of an erbium-doped fiber amplifier (EDFA) with a full control of the input signal and pump states of polarization.