6.4.2 Application: PMF Crosstalk (Swept Wavelength)Use this application for crosstalk measurements in polarization maintain-ing fibers (PMF) using a swept laser source. The crosstalk is often ex-pressed by the Polarization Extinction Ratio (PER) which is given by theratio between the power levels of the two PMF axes (typically expressedin dB).Connect the instrument and the PMF according to the following setup1:ContinuouslyTunableLaser SourcePER AnalyzerLaser Output Polarimeter Input(SMF/PMF)Personal ComputerA1200TriggerInput(BNC)Inline Polarizer(optional) PMFPaddlesUSBGPIBGPIBTriggerOutputTo optimize the PER inside the PMF follow these steps:• Setup your device so that light is guided through the PMF. If youconnected your laser source using GPIB it will be controlled au-tomatically. Otherwise use the manual mode and setup the laserso that it permanently sweeps over the desired wavelength range(typically 5nm to 10nm). The sweep speed should be around 40nm/s.• If you use an Agilent laser source you have to configure it before sothat it appears under ”Light Sources” in the browser. Please runthe configuration wizard before to install the laser source properly.• Start the PER-application by double-clicking it.• Enter the correct center wavelength and the sweep range.• Click on ”PER WL Scan”• Now the current PER is measured in realtime by continuously eval-uating the circle-trajectory.• Optimize the input polarization into the PMF by trying to minimizethe radius of the circle.• Once a PER value is stable, you can click on ”PER Live” for real-time alignment.• Now the current PER is measured in realtime based on the recentlystored reference.1 Many tunable laser sources have a PMF output. Therefore, the limited PER insidethis output PMF can reduce measurement performance. An inline polarizer canreduce this effect.A1XXX/A2XXX/A3XXX User Guide 51
