 Tue Jul 22 16:26:04 2014, Harry, Update, General, Fiber Mode Measurement 
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I repeated this process once more, this time using the computer controlled stage that the beam profiler is designed to be mounted to.
These data//fitting appears to be within error bars. The range of my measurements was limited when the beam width was near the effective aperture
of the profiler. |
 Mon Jul 28 17:25:32 2014, Harry, Update, General, Fiber Mode With Collimators
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Purpose
We want a measurement of the fiber modes at either end, with the collimators, because these will be the modes that we'll be trying to match in
order to couple light into the fibers, for FOL and/or future projects. |
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Fri Feb 6 18:06:18 2015, manasa, Update, General, Fiber Optic module for FOL
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I pulled out the Fiber Optic Module for FOL from the rack inside the PSL table enclosure and modified it. The beat PDs were moved into the box to
avoid breaking the fiber pigtail input to the PD.
The box has 3 input FC/APC connectors (PSL and AUX lasers) and 2 output FC/APC connectors (10% of the beatnote for the AUX |
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Fri Aug 15 17:24:44 2014, Harry, Update, General, Fiber Temp.
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Earlier today Q and I somewhat resurrected my old PER measurement setup so I could run the temperature characterization experiment.
Unfortunately, when I tried to use the fiber illuminator, no light came from the other end, causing me to fail my primary goal for the summer of
"don't break anything." The fiber has been re-spooled and labeled appropriately. Also sorry. |
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Thu Aug 14 18:10:46 2014, Harry, Update, General, Fiber Temperature Effects Setup
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Purpose
We want to characterize the sort of response the fibers have to temperature gradients along them (potentially altering indices of refraction, etc.)
Experimental Setup |
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Wed May 29 18:13:25 2019, gautam, Update, ALS, Fiber beam-splitters are now PM
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To maintain PM fibers all the way through to the photodiode, I had ordered some PM
versions of the 50/50 fiber beamsplitters from AFW technologies. They arrived some days ago, and today I installed them in the BeatMouth. Before installation,
I checked that the ends of the fibers were clean with the fiber microscope. I also did a little cleanup of the NW corner of the PSL table, where the 1um |
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Sun Mar 31 15:05:53 2019, gautam, Update, ALS, Fiber beam-splitters not PM
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I looked into this a little more today.
Looking at the beat signal between the PSL and EX beams from the NF1611 on a scope (50-ohm input), the signal Vpp was ~200 mV.
In
the time that I was poking about, the level dropped to ~150mVpp. seemed suspicious.
Thinking that this has to be related to the polarization |
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Thu Feb 12 12:16:04 2015, manasa, Update, General, Fiber shielding
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[Steve, Manasa]
The fibers around the PSL table were shielded to avoid any tampering. |
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Fri Oct 26 21:48:40 2007, waldman, Configuration, OMC, Fiber to 056
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I set up a 700 mW NPRO in Rana's lab and launched it onto a 50m fiber. I got a few mW onto the fiber, enough to see with a card before disabling the laser.
The fiber now runs along the hallway and terminates in rm 056. Its taped down everywhere someone might trip on it, but don't go out of your way to
trip on it or pull on it because you are curious. Tomorrow I will co-run a BNC cable and attenuate the NPRO output so it can only send a few mW and so |
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Wed Sep 22 16:35:45 2010, josephb, Update, CDS, Fibers pulled, new FB install tomorrow
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[Aidan, Tara, Joe]
We pulled out what used to be the LSC/ASC fiber from the 1Y3 arm rack, and then redirected it to the 1X1 rack. This will be used as the c1ioo
1PPS timing signal. So c1ioo is using the old c1iovme fiber for RFM communications back to the bypass switch, and the old LSC fiber for 1PPS. |
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Fri Apr 13 17:56:26 2018, gautam, Update, ALS, Fibers switched out
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I swapped the EX fiber for the PSL fiber in the polarization monitoring setup. There is a lot more power in this fiber, and one of the PDs was saturated.
I should really have put a PBS to cut the power, but I opted for putting an absorptive ND1.0 filter on the PD instead for this test. I want to monitor
the stability in this beam and compare it to the EX beam's polarization wandering. |
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Sat Apr 14 14:42:09 2018, gautam, Update, ALS, Fibers switched out
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It looks like the drift in polarization content in the PSL pickoff is actually much higher than that in the EX pickoff. Note that to prevent the P-pol
diode from saturating, I put an ND filter in front of the PD, so the Y axis actually has to be multiplied by 10 to compare power in S and P polarizations.
If this drift is because of the input (linear) polarization being poorly matched to one of the fiber's special axes, then we can improve the situation |
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Tue Apr 17 14:08:29 2018, gautam, Update, ALS, Fibers switched out
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A follow-up on the discussion from today's lunch meeting - Rana pointed out that rotation of the fiber in the mount by ~5degrees cannot account for
such large power fluctuations. Here is a 3 day trend from my polarization monitoring setup. Assuming the output fiber coupler rotates in its mount by 5
degrees, and assuming the input light is aligned to one of the fiber's special axes, then we expect <1% fluctuation in the power. But the attached |
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Fri Apr 20 00:26:34 2018, gautam, Update, ALS, Fibers switched out
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Summary:
I think the dominant cause for the fact
that we were seeing huge swing in the power coupled into the fiber was that the beam being sent in was in fact not linearly polarized, |
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Sat Jun 25 00:00:28 2011, Sonali, Update, Green Locking, Fibre Coupling.
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What I did today.
1. I tried to align the IR input beam by aligning the two mirrors, to couple input light into the fibre.
2.I was unsuccessful for a long time even though I tried a lot of tricks. |
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Thu Nov 4 03:13:46 2010, Suresh, Update, Locking, Fibre coupling 1064nm light at the south-end table
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[Kiwamu, Suresh]
We decided to use the 1064nm beam reflected from the Y1-1037-45-P mirror after the collimation lens following
the doubling crystal for coupling into the optical fiber (ref 3843 and 3847 |
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Thu Nov 4 19:00:57 2010, Suresh, Update, Locking, Fibre coupling 1064nm light at the south-end table
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The Fluke Visual Fault locator (Visifault) arrived and I used it to couple 1064nm light into the single mode fibre at
the south-end-table.
Procedure used: |
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Wed Feb 27 14:39:59 2013, Annalisa, Update, LSC, Fibre laid for RFPD audio
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[Annalisa, Jenne, Rana, Steve]
We installed the fibres on cable trays the 1Y2 and the Control Room.
Still to do: find a power supply for the Fiboxes and plug everything in. |
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Wed Feb 13 20:37:11 2008, John, Update, LSC, Fibre locking - Fiber
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Sam and I observed fringes in the light reflected from the Y arm. These fringes are due to the sidebands and not the carrier. To improve matters we plan
to reduce the RF AM and increase our modulation index. |
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Sat Jan 26 02:08:53 2008, John, Omnistructure, LSC, Fibres
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There is now a fibre running from the SP table to the ISCT at the Y-end. In the coming days I will try to mode match the beam from this fibre into the arm
through ETMY. To achieve this I will be altering the optical layout of this table. |
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Mon Feb 4 22:01:57 2008, John, Summary, LSC, Fibres auxiliary locking - Fibers
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I managed to couple ~75% of the light transmitted from the y arm, through the fibre, back to the SP table. I hoped that this would be a good way to match
the beam from the fibre into the arm. Still no flashes. It looks like the cameras just aren't sensitive enough. |
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Wed Jan 7 02:54:09 2015, Jenne, Update, LSC, Fiddling with DARM filters
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One of the things that we had talked about last night was the totally tiny amount of phase margin that we have in the CARM and DARM loops. DARM
seemed to be the most obnoxious loop last night, so I focused on that today, although the CARM and DARM loops are pretty much identical.
(Q tells me via email that the phase budget has the same ~14 degree discrepancy between what we expect and what we measure as his estimate last |
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Wed Jun 26 20:45:03 2019, gautam, Update, Cameras, Field of view options
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For the beam spot position tracking, I am wondering if there is any benefit to going for a wider field of view and getting the OSEMs in the frame? It
may provide some "anchor points" against which whatever algorithm can calibrate the spot position against. But there are also several point scatterers
visible in the current view, and perhaps the Gaussiam beam profile moving over them and tracking the scattered intensity from these point scatterers serves |
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Tue Sep 9 00:34:34 2014, Jenne, Update, LSC, Figuring out where to do DARM->AS55
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This afternoon, after Q and Manasa finished recovering from the activities of the morning, I aligned the IFO, and went to the Yend to touch up the alignment
of the green to the arm. I don't know if it was the alignment (I didn't do the PSL table), or I happened to have a good combination of laser temperatures,
or what, but the Yend ALS noise was super good. After that, the low frequency noise contribution is different lock-to-lock, and I haven't discerned |
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Tue Sep 9 14:25:46 2014, jamie, Update, LSC, Figuring out where to do DARM->AS55
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Quote:
I have made a ruidimentary lockloss plotting script, that I have put in ..../scripts/LSC/LockLossData, but I'm not satisfied with it yet. |
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Fri Aug 5 20:44:26 2011, jamie, Metaphysics, Treasure, Film crew here Monday morning
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Just a reminder that a film crew will be here Monday morning, filming Christian Ott for some Discovery channel show.
They are slated to be here from 8am to 12:30pm or so. They will take a couple of shots inside the lab, and the rest of the filming
should be of Christian in the control room (which they will "clean up" and fit with "sexy lighting"). I will try to be here the |
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Mon Aug 6 17:15:15 2012, Jenne, Update, ASS, Filter banks not working
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I was trying to load some filters into the ASS so that I can try it out, but for some reason the filter banks aren't working - clicking the on/off buttons
doesn't do anything, filters (which exist in the .txt file generated by foton) don't load.
I've emailed cds-announce to see if anyone has any ideas. |
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Tue Aug 7 00:22:10 2012, Jenne, Update, ASS, Filter banks working
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Quote:
I was trying to load some filters into the ASS so that I can try it out, but for some reason the filter banks aren't working - clicking the |
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Mon Oct 24 19:48:16 2011, Mirko, Update, Adaptive Filtering, Filter execution time
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Toyed around some more with the adaptive filters.
Execution time:
nTaps Downsampling factor Execution time average / max in ca. 3 min [us], (480
us available) |
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Thu Oct 28 02:01:51 2010, Kevin, Update, PSL, Filter for 2W Laser
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[Rana and Kevin]
I made a low pass filter for the piezo driver for the 2W laser that is now installed. The filter has a pole at 2.9 Hz. The transfer function is
shown in attachment 1. |
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Wed Oct 13 17:12:33 2010, josephb, yuta, Update, CDS, Filter name length problem found and fixed
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The missing filter files for ULPOS, URPOS, and so forth for the mode cleaner optics was due to the length of the names of the filters.
This was not a problem for the c1sus model because it was using its own name as the first 3 letters of its designation. A filter for the
sus model would be called something like BS_TO_COIL_MTRX_0_0, while for the mcs it would be called SUS_MC1_TO_COIL_MTRX_0_0, an extra 4 characters. |
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Fri Sep 26 00:19:54 2008, Jenne, Update, PSL, Filter-action with the PMC
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Written, but not posted on 24Sept2008:
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Fri Jun 6 11:19:13 2008, Caryn, Summary, PEM, Filtering MC_L and MC_F with PEM:ACC and microphone 8x
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Tried to filter MC_L and MC_F with acc/seis data and microphone data using wiener filter (levinson)
-Used get_mic_data.m and miso_filter_lev.m to make SISO filter for 2 minutes of IOO-MC_F data. Used PEM-AS_MIC signal as noise input data. Filters calculated |
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Wed Nov 30 02:04:26 2011, rana, den, jenne, kiwamu, jzweizig, Update, CDS, Filtering Noise issue tracked down ???
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You can read through all of our past tests to see what didn't work in tracking things down. As Den mentions, there was actually a lot of evidence
that there was some double->single precision action in the filter calculation causing the noise we saw.
However, it turns out that this is NOT the case. |
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Wed Nov 30 11:04:26 2011, josephb, Update, CDS, Filtering Noise issue tracked down ???
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Quote:
For now, I suppose we can just change this number to 1e-40 or so. I don't know how to calculate what the right number should be. Not sure |
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Wed Nov 30 11:36:12 2011, Den, Update, CDS, Filtering Noise issue tracked down ???
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Quote:
if((new_hist < 1e-20) && (new_hist > -1e-20)) new_hist = new_hist<0 ? -1e-20: 1e-20; |
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Wed Aug 1 22:37:21 2012, Jenne, Update, ASS, Filters installed in the ASS
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As part of trying to figure out what is going on with the ASS, I wanted to figure out what filters are installed on which lockins.
Each "DoF"(1-6) has a zpk(0.1,0.0001,1)gain(1000), which is a lowpass with 60dB of gain at DC, and unity gain at high frequencies.
For the lockins, since there are so many, I made a spreadsheet to keep track of them (attached). |
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Thu Sep 10 09:37:34 2015, Ignacio, Summary, IOO, Filters left on MCL static module
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The following MCL filters were left loaded in the T240-X and T240-Y FF
filter modules (filters go in pairs, both on):
FM7: SISO filters for MCL |
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Fri Jul 18 19:32:50 2014, Akhil, Summary, Electronics, Filters used inside the Frequency Counter
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Thanks Koji , for your hint for the brain teasing puzzle. I was looking into Filters that are usually used in devices like counters,
DSO and other scopes. I found that , to improve the quality of the measurement one of the best approach is averaging. I looked deeper into averaging |
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Mon Jul 21 12:16:27 2014, Akhil, Summary, Electronics, Filters used inside the Frequency Counter
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The expected bode plots for such a filter with L= 4 is attached and compared with the measured.
RXA: When comparing two things, please put them onto the same plot so that they can be compared. |
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Wed Aug 18 19:19:38 2010, Jenne, Update, SUS, Final 2 TTs suspended!
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[Jenne, Yoichi]
The final 2 Tip Tilts (#1 and #5) have been suspended. We have designated #5 the spare. It looks like there might be a teensy bit of
dust on the AR surface of the optic in #5, right near the edge of the coating. Not a critical issue if this one is the spare, although we should |
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Wed Feb 20 01:40:37 2013, Manasa, Update, Alignment, Final IFO alignment- in progress
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[Yuta, Sendhil, Jamie, Jenne, Rana]
1. After the MC centering, we tried to align the IFO using IPPOS and IPANG as reference. This did not recover the alignment perfectly. We were clipping |
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Mon Mar 25 16:51:43 2013, Chloe, Update, , Final QPD Circuit Design
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This is the final version of the QPD circuit I'm going to build. After playing around with the spatial arrangement, this should fit into the box that
I was planning to use, although it will be a rather tight fit. The pitch, yaw, and summing circuit will be handled with a quad op amp. Planning to meet
with Eric tomorrow to figure out the logistics of building things. |
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Fri Aug 28 00:59:55 2015, Ignacio, Update, IOO, Final SISO FF Wiener Filter for MCL
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This is my final SISO
Wiener filter for MCL that uses the T240-X seismo as its witness.
The main difference between this filter and the one on elog:11532 is the |
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Tue Jul 16 15:17:57 2019, Koji, HowTo, CDS, Final bit bug of the BIO CDS module
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Yutaro talked about the BIO bug in KAGRA elog. http://klog.icrr.u-tokyo.ac.jp/osl/?r=9536
I think I made the similar change for the 40m model somewhere (don't remember), but be aware of the presense of this bug. |
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Tue Sep 17 14:43:59 2019, gautam, HowTo, CDS, Final bit bug of the BIO CDS module
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Came across this while looking up the BIO situation at 1Y2. For reference, the fix Koji mentions can be seen in the attached screenshot (one example,
the other BIO cards also have a similar fix). The 16th bit of the BIO is grounded, and some bit-shifting magic is used to implement the desired output.
Quote:
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Fri Oct 4 22:22:03 2019, gautam, Update, CDS, Final incarnation of latch.py
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[KA, GV]
This elog is meant to be a summary of some of the many subtleties on the CM board. The latest schematic of the version used at
the 40m can be found at D1500308 . |
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Tue Oct 8 03:19:14 2019, Koji, Update, CDS, Final incarnation of latch.py
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Now with the CM board tested with the signal injected, it turned out that the latch logic was flipped. As the default state locked the digital levels,
the buttons other than the mbbo channels were inactive.
By giving 0 to C1:LSC-CM_LATCH_ENABLE, the modification of the digital state is enabled. And with the value of 1, the digital bits on the board |
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Thu Sep 11 11:29:14 2008, josephb, Configuration, Computers, Final netgear switch in place in 1Y2
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I've placed the final (of 4) Netgear prosafe 24 port switch at the very top of 1Y2. At that location, there are no holes left to screw into, so it has
4 rubber feet and is sitting on the top most signal generator. It has been plugged in and connected to the control room hub with a labeled cat6 ethernet
cable.
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Fri Aug 2 21:59:36 2013, Charles, Update, ISS, Finalized ISS Schematic (hopefully)
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Attached is the finalized schematic. The general circuit topology should remain the same from this point forward, although individual component values
are subject to change. I will also be adding some more annotations to ensure everything on the board is clear.
In general, I have finally included all of the correct components (i.e. front panel switches are now actually switches and front panel LEDs are |