aLIGO LHO Logbook

H1 CDS (ISC, PSL)

filiberto.clara@LIGO.ORG - posted 14:08, Tuesday 09 April 2024 - last comment - 12:35, Wednesday 17 April 2024(77062)

SPI Pick-off Fiber Length

WP 11805
ECR E2400083

Lengths for possible SPI Pick-off fiber. Part of ECR E2400083.

PSL Enclosure to PSL-R2 - 50ft
PSL-R2 to SUS-R2 - 100ft
SUS-R2 to Top of HAM3 (flange D7/D8) - 25ft
SUS-R2 to HAM3 (flange D5) - 20ft

Comments related to this report

jeffrey.kissel@LIGO.ORG - 16:28, Tuesday 09 April 2024 (77072)

Link

J. Kissel [for J. Oberling]

Jason also took the opportunity during his dust monitoring PSL incursion today to measure the distance between where the new fiber collimator would go on the PSL table to the place where it would exit at the point Fil calls the PSL enclosure.

He says 
SPI Fiber Collimator to PSL Enclosure = 9ft.

jeffrey.kissel@LIGO.ORG - 13:53, Thursday 11 April 2024 (77118)

Link

J. Kissel [for F. Clara, J. Oberling]

After talking with Fil I got some clarifications on how he defines/measures his numbers:
   - They *do* include any vertical traversing that the cable might need to go through,
   - Especially for rack-to-rack distances, always assumes that the cable will go to the bottom of the rack (typically 10 ft height from cable tray to rack bottom), 
   - He adds two feet (on either end) such that we can neatly strain relieve and dress the cable.

So -- the message -- Fil has already built in some contingency into the numbers above. 
(More to the point: we should NOT consider them "uncertain" and in doing so add an addition "couple of feet here" "couple of feet there" "just in case.")

Thanks Fil!

P.S. We also note that, at H1, the optical fibers exit the PSL at ground level on the +X wall of the enclosure between the enclosure and HAM1, underneath the light pipes. Then the immediately shoot up to the cable trays, then wrap around the enclosure, and then land in the ISC racks at PSL-R2. Hence the oddly long 50 ft. number for that journey.

Jason also reports that he rounded up to the nearest foot for his measurement of the 9ft run from where the future fiber collimator will go to the PSL enclosure "feed through."

jeffrey.kissel@LIGO.ORG - 12:35, Wednesday 17 April 2024 (77249)SEI, SYS

Link

Upon discussion with the SPI team, we want to minimize the number of "patch panel" "fiber feedthrough" connections in order to minimize loss and polarization distortion.

As such, we prefer to go directly from the "SPI pick-off in the PSL" fiber collimator directly to the Laser Prep Chassis in SUS-R2.
That being said purchase all of the above fiber lengths, such that we can re-create a "fiber feedthrough patch panel full" system as contingency plan.

So, for the baseline plan, we'll take the "original, now contingency plan" PSL-R2 to SUS-R2, 100 ft fiber run and use that to directly connect the "SPI pick-off in the PSL" fiber collimator directly to the Laser Prep Chassis in SUS-R2.

I spoke with Fil and confirmed that 100 ft is plenty enough to make that run (from SPI pick-off in PSL to SUS-R2).