Williams Tutorial Updated 11 14

Fiber and component metrology for high-speed communications:What the manual doesn’t tell youPaul Williams, Paul Hale, and Tracy ClementNational Institute of Standards and TechnologyBoulder, Colorado1. Polarization-mode dispersion (Williams)2. Transmitter/receiver frequency response (Hale and Clement)1Part 1. Polarization-mode dispersionPMD measurement advice for folks with turnkey measurement systemsAssumptions:A basic understanding of PMDA PMD measurement systemAn understanding of the measurement techniquesAvoid measurement traps that give false results.2Steps to a good PMD measurement1. Perform measurement “calibration”2. Understand limitations imposed by measurement conditions3. Choose measurement parameters correctly4. Be aware of measurement uncertaintiesAssumption: measurement system works correctly3Review: PMD DefinitionsOutput PSP_General Case:(slow)Output PSP+Input PSP_ (fast)Input PSP+(slow)(fast)• Birefringence affects propagation velocity and output polarization state• PMD is characterized by two Principal States of Polarization (PSP)• PSPs are wavelength-independent (to first order)• Propagation along PSPs is the fastest/slowest possible• PMD is the phenomenon, DGD (∆τ) is the magnitudeDifferential group delay (DGD): ∆τ =τ −τfast slow4Review: Time domain PMD measurementlow-coherence interferometery (INT)broadband sourceDet.∆τ Time (ps)• “Width” of delay histogram gives mean DGD• Measures only mean DGD ...