1. Nature of light Ray or geometrical optics Wave or physical optics Quantum theory: W p =hf

2. Advantages of fibers Abundance of raw material Cheaper Low losses EMI immunity: Security Information capacity

3. Applications Undersea cables Along power lines Aircraft wiring Sensors Biomedical

4. Chapter 2: Optics review Ray theory (geometrical tracing) Light enters a fiber – critical angle - TIR Lenses: focus light onto fiber Focal point, distance, plane Thin lens, ideal lens Focal length formula

5. Thin Lens rules 1.Center rays are undeviated 2.Parallel rays pass through focal point 3.Rays parallel to center ray intersects it on focal plane 3.Rays pass through focal length emerge parallel to axis

6. Lenses Cylindrical lens – fig 2.10 Graded-index – fig 2.15 Collimating light out of fiber – fig 2.10 Imaging Image location and magnification Angular spread Example 2.4

10. Numerical Aperture It is important for an optical system to collect light over a wide incident angle Lens+Rx combination Max acceptance angle: tan  = d/2f Numerical aperture: NA = n o sin 

11. Numerical Aperture High and low NA fibers Long path fibers: NA (0.1 – 0.3) Short fibers: NA (0.4 – 0.5) Example 2.5 Derive NA of a fiber

12. Diffraction Transverse plane Power = intensity Central spot diameter Gaussian beams Compare to uniform beam Uniform Beam d = 2.44 f/D w o = f/  w Beam focusing

13. Diffraction Gaussian beam representation Beam collimation Beam diverges at at a constant full angle of  =2 /  w HW #1:2-6,2-8,2-9, due: a week

14. Free Space Optics The Canobeam DT-55 adjusts the beam according to the distance it must travel, maintaining beam focus and signal strength fully over its transmission range.