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

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 61300-3-6 “Fibre optic interconnecting devices and passive components-basic test and measurement procedures”

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

F = 9.0 N Reflections (with APC better)

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

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

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

OCWR method (Optical Continuous Wave Reflectometry) According to International standard IEC 61300-3-6 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

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

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 months @ 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

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

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