Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax Single mode fibre transmission apparatus Chris F. Dimas, Anthony Knottenbelt, Peter Sinclair Spectral Applied Research June 17, 2014 Measuring light where it counts

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax Company profile High-tech manufacturing facility located in Richmond Hill, Ontario Manufacture laser engines, specialized microscope systems (confocal, TIRF) Manufacture other fiber optic systems for biomedical OEM customer 35 Employees Large R&D department Last year was purchased by Andor Technology, and later by Oxford Instruments

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax 405nm laser+single mode fibre 405nm laser A Single mode Fiber - designed to carry light only directly down the fibre - the transverse mode Most common biophotonics applications: Fluorescence microscopy Therapeutics Etching, micromachining

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax Problem Light transmission degrades rapidly in single mode fibre when exposed to 405nm light, %/hr ( %/day) Light is cw laser, and below the damage threshold for fiber: 1MW/cm 2 as opposed to 1GW/cm 2 Possible causes:, LIPSS Gonshior, C. P., et al, (2013). Generation of periodic surface structures on silica fibre surfaces using 405nm CW diode lasers. Journal of Non-Crystalline Solids, 361(1), Contamination on end of fibre Solarization of fibre Defective AR coating Burning of input due to improper alignment Need to measure the degradation Precisely: +/-0.02%/hr Over a shorter period of time: 17 hrs., not 1000hrs Without damaging product

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax Techniques laser Detector is underfilled Detector is underfilled at beginning… Can measure light at the focus, off focus, and beamshape laser fibre Detector (thermopile) Detector (integrating sphere) Lens Camera

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax Technique 1. Directly at fibre laser Measuring rates of < -0.1%/hr +/- 0.02%/hr, linear decay Concluded rate after 17 hour test Realized that detector needed to be thermally controlled, laser needed to be thermally controlled, and that continuous monitoring of laser input power (to provide closed loop feedback) is, unfortunately, not possible Detector (thermopile) fibre

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax Techniques 2. At output of relay lens laser Corrected for laser thermal, detector thermal, rig dependency Measured higher degradation rates, not linear, but with quadratic component as well Beam profiles at fibre end showed widened beams for contaminated fibre ends (-0.5%/hr) Perhaps something similar going on even though surfaces were clean Relay lens Detector (integrating sphere) Cannot test every production unit for 1000hrs! More investigation required!!!

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax Beam profiles; before and after cleaning fibre Before After cleaning  R  

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax Beam profiles, cont.. In this instance, the change to the beam profile was more severe, did not have significant power degradation rate, and furthermore cleaning the end of the fibre did not improve the beam profile

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax White light profilometry

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax Technique 3. Using beam profiles laser Measuring the beam profile periodically throughout the test Camera Relay lens Detector (integrating sphere) Collimating lens fibre

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax Beam profile vs. Power out E C

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax Beam profile vs. Power out Shape of beam profile has a close correspondence to % power degradation Knowing the hours of exposure, know the % deg/hr, one shot-measurement

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax Failure mode diagnosis Rate of Degradation (Transmission) Rate of Increase of Edge to Centre Ratio Failure Mode 0.5%/hr>30%/1000hrContamination of output 0.1%/hr30%/1000hrBurning of input 0.01%/hr30%/1000hrPit formation/ LIPSS

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax Conclusions Prolonged exposure to 405nm laser light in single mode fibre in our case causes depression in fibre core The rate of power degradation and beam profile degradation can diagnose the root cause of failure in a fibre A beam profile gives a more application specific rate of degradation, in addition to allowing for a non-destructive and immediate diagnosis if the number of hours of exposure is known.

Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Phone Fax Thank you!