Jose Luis Sirvent Jonathan Emery Student Meeting 08– May -2012

 1.2 Coupling Efficiency VS D2 Variation

 2.1 Main problems (SMF): Signal Modulation ◦ Disk imperfections? NO! ◦ SMF Vibrations sensibility? NO! ◦ Fabry-Perot Interferometer? YES!

 2.2 Fabry-Perot Interferometer: Principle ◦ Optical waves interference due to:  path difference  Phase diference & Coherence lengh  R= Mirror reflectivity  R1= Fresnel reflectivity (Interface Silica/air)  Xo= Path Difefence ◦ Detection of movements in the order of ½ lamda

 Let’s simulate to verify! ◦ Real values: Fibre-disk= 200um  Fresnel Reflection (end of fiber): -17dB  Borofloat Reflectivity: 5%  Chrome Reflectivity: 60%  Displacement 2.5um  Solution: Avoid Fresnel reflections. Use APC Fiber ending

 Is the APC ending a solution? ◦ Let’s simulate: Real values again  Fresnel Reflection (end of fiber): -40dB  Borofloat Reflectivity: 5%  Chrome Reflectivity: 60%  Displacement 2.5um  It seems to work!  Practical verification?

 Practical verification: ◦ Results:  1. Fresnel Reflections reduced (not avoided)  2. Less light is collected back  3. Necessity of tilting the fiber a bit  4. Lens verification needed (Components ordered) PC Ending APC Ending

Proto glass disk pattern v3 [  m] mm 40 mm Chrome(brillant) [mm] Gap= 6 * Alpha 30 ° Track Glass disk line 1: Alpha = deg Edges (360 / Alpha)= (-2 * 6)  Gaps Glass disk line 2: Alpha = deg Edges (360 / Alpha)= (-2 * 6)  Gaps …………. (See table attached)

Proto glass disk pattern v3 [  m] Duty cycle= 50% Track shape 