19078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
Single mode fibre transmission apparatus
Chris F. Dimas, Anthony Knottenbelt, Peter SinclairSpectral Applied Research
June 17, 2014
Measuring light where it counts
29078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
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
39078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
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
49078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
Problem
•Light transmission degrades rapidly in single mode fibre when exposed to 405nm light, 0.01-0.5%/hr (0.3 - 11%/day)
•Light is cw laser, and below the damage threshold for fiber: 1MW/cm2 as opposed to 1GW/cm2
•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), 106-110
• 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
59078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
Techniques
laser •Detector is underfilled
•Detector is underfilled at beginning…
•Can measure light at the focus, off focus, and beamshape
laser
laser
1.
2.
3.
fibre
fibre
fibre
Detector (thermopile)
Detector (integrating sphere)
Lens
Lens
Camera
69078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
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
y = -0.0206x + 99.932
R2 = 0.9259
99.40
99.50
99.60
99.70
99.80
99.90
100.00
100.10
100.20
0 2 4 6 8 10 12 14 16 18
Time (hr)
Po
wer
Regression statisticsslope: -0.0000089std error: 0.0000000321
Detector (thermopile)
fibre
79078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
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
y = -0.0002x2 + 0.0306x + 99.909
R2 = 0.8423
y = -0.0002x2 + 0.0222x + 100.19
R2 = 0.986650.00
60.00
70.00
80.00
90.00
100.00
0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00 800.00 900.00 1000.00
Total Time on Burn-in (hrs.)
Po
wer
ou
tpu
t (n
orm
aliz
ed)
25.00
30.00
35.00
40.00
45.00
50.00
Po
wer
ou
tpu
t n
orm
aliz
ed (
scal
e fo
r C
3 50
% p
ow
er o
nly
)
Relay lens
Detector (integrating sphere)
Cannot test every production unit for 1000hrs!
More investigation required!!!
89078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
Beam profiles; before and after cleaning fibre
Before After cleaning
R
99078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
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
109078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
White light profilometry
119078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
Technique 3. Using beam profiles
laser
•Measuring the beam profile periodically throughout the test
Camera
Relay lens Detector (integrating sphere)
Collimating lens
fibre
129078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
Beam profile vs. Power out
E
C
139078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
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
y = 0.0003x + 0.9568
R2 = 0.9125
0.8
0.9
1
1.1
1.2
1.3
1.4
0 200 400 600 800 1000 1200
Time (hrs.)
E/C
(R
atio
, ed
ge
to c
entr
e)
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
c v, (C
oef
fici
ent
of
vari
atio
n i
n c
entr
e o
f p
rofi
le,
%)
149078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
Failure mode diagnosis
Rate of Degradation
(Transmission)
Rate of Increase of
Edge to Centre Ratio
Failure Mode
0.5%/hr >30%/1000hr Contamination of output
0.1%/hr 30%/1000hr Burning of input
0.01%/hr 30%/1000hr Pit formation/ LIPSS
159078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
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.
169078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada
Phone 905-326-5040 Fax 905-326-5041 [email protected] www.spectral.ca
Thank you!