Student : Chen – Fung Tsen Advisor : Sheng – Lung Huang

大綱 Introduction of OSA Basic block diagram Types of OSA - Interferometer- based optical spectrum analyzers ( 略 ) - Diffraction- grating- based optical spectrum analyzers Monochromator - Diffraction grating equation - Resolution / Grating resolve power - Compare of single / double monochromator Basic operation of OSA

OSA-Optical spectrum analyzer The OSA is used to show power levels as a function of wavelength. The range of the OSA is typically 600 nm to 1700 nm. The OSA has resolution bandwidths typically from 0.06 nm to 10 nm.

Basic block diagram

Tunable bandpass filter Prism-based optical spectrum analyzer Diffraction-grating-based optical spectrum analyzer Monochromator B: entrance slit C,E : concave mirror D : diffraction grating F: exit slit G : output light with “single” color

Diffraction grating equation Monochromator : The grating is rotated to select different wavelengths. (fixed position of entrance & exit slit)

Dispersion and Bandpass f : effective focal length

Resolution-Rayleigh criterion Two wavelength are just resolved when the maximum of one lies at the first minimum of the other. UnresolvedRayleigh criterionResolved

Grating resolving power δλ : smallest resolvable wavelength difference (resolution) m : diffraction order N : the number of grating blaze W : the ruled width of the grating

Double Monochromator

Compare of single/double monochromator Double monochromator Higher dynamic range : Filter shape is specified in terms of dynamic range. Additive dispersion : The reciprocal linear dispersion of the entire system is the sum of the reciprocal linear dispersions of each monochromator. Reduced stray light(unwanted light)

Optical spectrum analyzer Ex.YOKOGAWA AQ6370C / HP 71451B Spec: AQ6370CHP 71451B Wavelength range: 600 to 1700nm Wavelength resolution 0.02nm < 0.08 and 0.1 to 10 nm in a 1,2,5 sequence Dynamic range 78dB typ50dB Measuremen t speed 0.2 sec. (100nm span) 40 nm/50 ms

Basic operation of OSA Step : 1. Connecting Optical Fiber 2. Switching Power On 3. Set the Center wavelength 4. Set the Span (sweep width)

Set the Resolution Set the peak level wavelength as the Center wavelength. Press the Peak → Center Center of shortcut key to set the wavelength at the peak level to be displayed at the center of the screen. Set the peak level as the reference level