1. Optical performance measurements of various fibre connections
in harsh environments
by Jan Koopstra et. all
STATUS
and
overview

2. Optical performance measurements of various fibre connections
in harsh environments
Purpose:
To determine the maximum acceptable return loss of a “bare” optical connector if implemented near by the R-EAM
To balance opinions versus real performances
Find a connector preferable with angled end face
Test range is in air, oil and in water up from atmospheric pressure to 600 Bar
Return Loss of optical connectors
*Insertion Loss of optical connectors (attenuation)
Fibre splice attenuation (bare splice and protected splice)
Optical loss of a penetrator from atmospheric pressure to 600 Bar
Ultimo BER tests
* Guided by the International Standard: IEC
“Fibre optic interconnecting devices and passive components-basic test and measurement procedures”

3. Components:
All (almost all) fibre used is standard single mode fibre SMF28e with primary coating from “Draka Comteq” (Lots of tests and knowledge about the behavior under various conditions among aging is can be found in literature)
If SMF28 fibre results are positive than results with the new “BendBright-XS” fibre G.655 gives inherently a better result. (Difficult to measure)
All (almost all) the “bare” connectors are supplied by “Diamond Kimberlite” Special ferrules are prepared in order to let water or oil penetrate easily into the spit sleeve up to the end faces of the optical connection
The splice protectors are from Corning (HPS-60S100) 60 mm
The used penetrators are home made and assembled and fitted in a pressure tank by Nikhef
An “aging” procedure has started last February by posing all the involved materials in Oil “Midel 7131” @ atmospheric pressure

4. F = 9.0 N
Reflections
(with APC better)

5. Test Program
Test schema
All test are finished by ultimate BER tests

6. Possible Return Loss implication nearby OM
Unwanted superposition
of optical CW power and reflected demodulated power
Modulated signal with uncorrelated
Smaller modulated signal (in red)
CW_laser light from shore
R-EAM
mirror
Short fibre length
from breakout box to R-EAM inside OM
Critical point: Connector end faces reflections
Estimated acceptable refection less than -70 dB

7. FC/APC optical connector under tests
FC/APC connecter
connector
mating ferule with C …
Zirconia alignment split-sleeve inside ferule
Test in Seawater

8. OCWR method (Optical Continuous Wave Reflectometry)
According to International standard IEC P
Step 1
Initial remaining optical power measuring at PM position P P P
Step 2
Initial optical reflected power measured at PM position P P P
Step 3
Initial optical total reflected power measured at PM position P P
RL=-10log [dB]
P reflected
P incident

9. Minimum fibre length and connecter with perfect Return Loss figure
split sleeve
mode field diameter
F = 90 N
cladding
core
Observations: more reflected light especially in the cladding
e.g. by connecter alignment displace (under influence of pressure?? by gap between end faces (dirt, scratches, not matching surfaces)
by hooked glued fibre in ferrule
by core diameter fluctuations in length
by core offset to cladding fibre dependent
by core ovalty
“Whispering gallery mode” (cladding modes) is Light loss due to reflected light is send back into the cladding and results in unstable fibre use and/or measurements
To avoid influence of this phenomena in the results extinguish this extra light
by using a few meters of fibre between connections or take a perfect connector
with > -60 dB return loss

10. This design was successfully tested for many months @ 600 bar, 20 ºC.
Penetrator design
Primary coating stripped over 30 mm length
Detail not tot scale
RVS 316 capillary tube,
1mm bore hole
3mm outer diameter
25 mm
RVS 316 capillary tube,
0.5 mm bore hole
1 mm outer diameter
100 mm
This design was successfully tested for many 600 bar, 20 ºC.
Condensed assembly procedure:
Strip primary coating of fiber and clean fiber surface
Insert stripped fiber section in 0,5 mm capillary
Insert 0.5 mm capillary in 1 mm capillary
Position assembly on hot plate and adjust hot plate to 80°C capillary temperature
Apply Epotek 353 ND potting on fiber and to capillary rims & observe soak-in of potting in 0.5 mm capillary

11. Penetrator Optical fibre Stainless steel insert
Stainless steel gland from Conax clamping the insert

12. First Results June 30th 2010
The first results are that we can construct and test the “home made” penetrators with a reliable repetition rate
No change in attenuation of the fibre at a pressure of 600 bar
A chain of 10 fusion splices with applied splice protectors showed no significant change in attenuation when pressurized at 600 bar
To be continued next week