PolaStay POS-002 Reset-Free Polarization Tracker Module

The POS-002 polarization tracker automatically adjusts the state of polarization (SOP) towards a reference SOP. It counteracts continuous input SOP variations as fast as 0.9 ms without resets. A feedback signal sets the reference SOP and can come from inside the module or from an external source.

The internal feedback version (POS-002-I) contains a fiber squeezer polarization controller, an in-line polarization monitor, digital and analog circuits, and a control algorithm. The error signal from the polarization monitor goes back to the polarization controller to keep a linear SOP at the output. The output fiber is typically PM fiber, with the SOP aligned to its slow axis.

The external feedback version (POS-002-E) replaces the internal polarization monitor with an external analog electrical feedback signal chosen by the user. Examples are a voltage proportional to the degree of polarization (DOP) measured by a polarimeter, the bit-error rate (BER) from a BER chip, the RF spectrum of a detected signal, or the optical power after a polarizer. The controller adjusts the polarization to maximize the feedback signal. The output fiber is typically single mode fiber.

The module does the same job as the POS-20X polarization stabilizer instruments, but in a compact form for integration into larger systems. Typical uses include PMD compensation, polarization demultiplexing, removing polarization fading in coherent detection and fiber sensor systems, and stabilizing polarization for coherent receivers.