40m
QIL
Cryo_Lab
CTN
SUS_Lab
TCS_Lab
OMC_Lab
CRIME_Lab
FEA
ENG_Labs
OptContFac
Mariner
WBEEShop
|
40m Log |
Not logged in |
 |
|
Thu Jan 4 12:46:27 2018, gautam, Update, ALS, Fiber ALS assay 
|
Thu Jan 11 14:22:40 2018, gautam, Update, ALS, Fiber ALS assay
|
Thu Jan 11 20:51:20 2018, gautam, Update, ALS, Fiber ALS assay
|
Tue Jan 16 21:50:53 2018, gautam, Update, ALS, Fiber ALS assay
|
Thu Jan 18 00:35:00 2018, gautam, Update, ALS, Fiber ALS assay 
|
Fri Jan 19 11:34:21 2018, gautam, Update, ALS, Fiber ALS assay
|
Fri Jan 19 23:04:11 2018, gautam, Update, ALS, Fiber ALS assay
|
Wed Jan 24 00:33:31 2018, gautam, Update, ALS, Fiber ALS assay
|
Wed Jan 24 10:45:14 2018, gautam, Update, ALS, Fiber ALS assay
|
Thu Jan 25 23:59:14 2018, gautam, Update, ALS, Fiber ALS assay
|
Fri Jan 26 20:03:09 2018, gautam, Update, ALS, Fiber ALS assay
|
Wed Jan 31 15:45:22 2018, gautam, Update, ALS, Fiber ALS assay
|
Wed Jan 31 16:29:42 2018, gautam, Update, ALS, Modulation depths 
|
Wed Jan 31 16:33:53 2018, gautam, Update, ALS, ALS electronics at LSC rack
|
Wed Jan 31 22:32:11 2018, gautam, Update, ALS, ALS signal chain + power budget 
|
Thu Feb 1 01:24:56 2018, gautam, Update, ALS, D0902745 revamp underway
|
Fri Feb 2 00:26:34 2018, gautam, Update, ALS, D0902745 revamp underway
|
Fri Feb 2 13:16:55 2018, gautam, Update, ALS, ALS signals whitening switching 
|
Mon Feb 5 14:11:01 2018, gautam, Update, ALS, Huge harmonics in ALS channels 
|
Mon Feb 5 22:57:28 2018, gautam, Update, ALS, Huge harmonics in ALS channels
|
Tue Feb 6 11:13:26 2018, gautam, Update, ALS, Possible source of ground loop identified
|
Tue Feb 6 22:55:51 2018, gautam, Update, ALS, Possible source of ground loop identified
|
Thu Feb 8 00:33:20 2018, gautam, Update, ALS, D990694 characterization / THD measurement plan
|
Thu Feb 8 01:27:16 2018, Koji, Update, ALS, D990694 characterization / THD measurement plan
|
Fri Feb 9 13:37:44 2018, gautam, Update, ALS, THD measurement trial
|
Thu Feb 8 12:00:09 2018, gautam, Update, ALS, D990694 is NOT differential receiving
|
Thu Feb 8 13:13:14 2018, gautam, Update, ALS, D990694 pulled out  
|
Thu Feb 8 18:10:36 2018, gautam, Update, ALS, D990694 pulled out
|
Wed Feb 7 15:51:15 2018, gautam, Update, ALS, D0902745 revamp complete
|
Fri Feb 16 01:34:40 2018, gautam, Update, ALS, D0902745 in-situ testing 
|
Tue Feb 20 23:08:27 2018, gautam, Update, ALS, D0902745 in-situ testing
|
Thu Feb 22 00:09:11 2018, gautam, Update, ALS, D0902745 in-situ testing  
|
Sun Feb 25 00:03:12 2018, gautam, Update, ALS, Daughter board prototyping    
|
Mon Feb 26 20:55:56 2018, rana, Update, ALS, Daughter board prototyping
|
Tue Feb 27 21:10:45 2018, gautam, Update, ALS, Daughter board testing  
|
Wed Feb 28 19:13:25 2018, gautam, Update, ALS, ADC test for differential receiving in c1lsc
|
Fri Mar 2 01:45:06 2018, gautam, Update, ALS, new look ALS electronics
|
Mon Mar 5 17:27:34 2018, gautam, Update, ALS, new look ALS electronics - characterization
|
Thu Mar 8 00:40:25 2018, gautam, Update, ALS, new look ALS electronics - characterization
|
Thu Mar 8 19:38:37 2018, gautam, Update, ALS, digital unwhitening of daughter board
|
Thu Mar 8 23:50:27 2018, gautam, Update, ALS, First look at new ALS electronics
|
Fri Mar 9 01:07:01 2018, gautam, Update, ALS, First look at new ALS electronics
|
Mon Mar 12 22:08:31 2018, gautam, Update, ALS, Noisy POX
|
Mon Mar 12 23:57:31 2018, gautam, Update, ALS, Noisy POX 
|
Mon Mar 19 15:02:29 2018, gautam, Update, ALS, Noisy MC sensing
|
Thu Feb 1 15:31:12 2018, gautam, Update, ALS, ALS signal chain + power budget
|
Wed Feb 7 10:16:26 2018, gautam, Update, ALS, ALS signal chain + power budget
|
Thu Jan 25 13:18:41 2018, gautam, Update, ALS, Fiber ALS assay
|
|
Message ID: 13595
Entry time: Wed Jan 31 22:32:11 2018
In reply to: 13594
Reply to this: 13596
13597
13613
|
Author: |
gautam |
Type: |
Update |
Category: |
ALS |
Subject: |
ALS signal chain + power budget |
|
|
Summary:
I do not have an answer to the question "What is an appropriate gain for the IF amplifier stage in the D0902745 FET demod boards?", because of the following problems.
Deatils:
The plan is to lower the gain of the IF amplifier stage on the FET demodulator board from 100 to 10. As per Attachment #1, this will make the overall gain from RF beatnote from the Beat Mouth to the signal input to the D990694 whitening board +19dB, assuming "typical" values for the conversion loss of the mixer, and the various other passive components on the FET demod board. I've used numbers I measured a couple of weeks ago for the delay line loss and the cabling loss from the PSL table to the LSC rack. This in turn will set a limit on how much RF beat power we can handle, from the Beat Mouth. According to this power budget, if we have -5dBm of beat, we will have an input to the whitening board of ~6Vpp, which is about half its full range. The trouble is, I don't know what the transimpedance gain of the Fiber Beat PDs are. The datasheet suggests a "maximum gain" of 5e4 V/W, which presumably takes into account the InGaAs responsivity and the actual transimpedance gain. However, according to the last power budget I did inside the Beat Mouth, I had -8dBm of beat for a combined 400uW of PSL+EX light, which definitely does not add up. I've emailed the company to ask about the spec, haven't gotten anything useful yet...
The problem is further complicated by the fact that the fiber inside the Beat Mouth is NOT polarization maintaining, and so the actual relative polarizations of the arm IR light and the PSL IR light is unpredictable, and also uncontrolled. I suppose we could simply place a HWP before the fiber collimator at either end, and rotate the polarization until we get a desired amount of beat, but this still does not solve the problem of the polarization being uncontrolled.
I am going to characterize the demod board using E1100114. I am unsure as to the conversion loss of the mixer - the datasheet suggested a number of 8dB, but T1000044 suggests that the conversion loss is actually only 4dB. I figure it's best to just measure it. Would also be good to verify that the overall transfer function and noise of the IF amplifier stage match my expectation from the LISO model.
Option #1: Rana ordered 50ohm and 500ohm SMD resistors of the 0805 package size, I asked Steve to get a few more values just in case we want to twiddle with the gain of this stage further (specifically, I asked for values such that we can set it to x5, x3 and x1). But changing the feedback resistors modifies the overall TF shape - see e.g. Attachment #2. Need to also look at how the noise performance varies.
Another possibility is to turn down the gain of the IF amplifier stage to x10, retire the ZHL-3A, and use a lower gain amplifier in its place. We do have the recently acquired Teledyne amplifiers, but we would have to package it in such a way that it can be integrated into the existing Fiber ALS signal chain. This would allow us to handle significantly larger RF beatnote powers, which I expect we will have if we improve the mode matching into the fibers (provided the aforementioned polarization drift possibility doesn't hurt us too much).
A third possibility is to attenuate the power coupled into the fibers to lower the RF beatnote amplitude. I don't like this option so much because placing an ND filter or a PBS+HWP combo in the beam path is likely to screw up the mode-matching into the fiber collimator, which I have already spent so many hours trying to improve, but if it must be done, it must be done.
The correct option is of course the one that gives us the lowest ALS noise. It is not clear to me which one that is at this point. |
|
|
|
|