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Entry  Thu Oct 3 12:08:47 2019, gautam, Update, General, Make the Jenne-laser setup fiber-coupled PDFR_tabletop.pdfIMG_8014.JPG
    Reply  Thu Oct 3 14:32:37 2019, rana, Update, General, Make the Jenne-laser setup fiber-coupled 
       Reply  Thu Oct 3 14:54:33 2019, Koji, Update, General, Make the Jenne-laser setup fiber-coupled 
          Reply  Thu Oct 3 21:05:04 2019, aaron, Update, General, Make the Jenne-laser setup fiber-coupled PD_response.pdf
             Reply  Thu Oct 3 23:15:39 2019, Koji, Update, General, Make the Jenne-laser setup fiber-coupled 
             Reply  Fri Oct 4 00:30:31 2019, gautam, Update, General, Make the Jenne-laser setup fiber-coupled 
                Reply  Fri Oct 4 14:25:59 2019, aaron, Update, General, Make the Jenne-laser setup fiber-coupled PD_norm.pdfPD_AB.pdfJenneAM_fiberPD_cals.pdf
Message ID: 14940     Entry time: Fri Oct 4 14:25:59 2019     In reply to: 14937
Author: aaron 
Type: Update 
Category: General 
Subject: Make the Jenne-laser setup fiber-coupled 

Summary:

The fiber-coupled PD seems to have a factor of ~1.5 difference in responsivity compared to the free-space PD. There are some differences in the two ways I made the measurement that I don't yet understand.

Details

I measured relative responsivities of the fiber and free coupled NewFocus 1611 PDs (scaled by the Jenne AM transfer function).

I made the measurement in two ways, see attachment threeIn attachment oneI show the response for separately measuring the two PDs relative to a pickoff of the source (two-port thru calibration). In attachment two I measure the relative responses directly, without picking off a reference (three-port calibration). I scaled the transfer functions by their DC voltages; both PDs have transimpedances of 700 V/A.

However, there are some clear differences in the response (overall factor of 0.5dB offset that may be explained by a miscalibrated DC level; apparent periodicity in attachment 1) that I don't yet understand.The free path of the non-fiber PD is ~5-6 inches, which accounts for the ~45 degrees of phase advance of the fiber relative to free coupled PD signal. (12.7cm / (c / 300 MHz) * 360 degrees ~ 45 degrees)

I didn't find Agilent's manual very helpful for learning about the available calibration schemes, and didn't find a resource online that I liked -- is there a good one?
I think I want to characterize the WFS heads treating the DUT as a three-port device (AM in, ref PD, WFS segment PD).
Attachment 1: PD_norm.pdf  32 kB  Uploaded Fri Oct 4 20:02:50 2019  | Hide | Hide all
PD_norm.pdf
Attachment 2: PD_AB.pdf  33 kB  Uploaded Fri Oct 4 20:20:16 2019  | Hide | Hide all
PD_AB.pdf
Attachment 3: JenneAM_fiberPD_cals.pdf  35 kB  Uploaded Fri Oct 4 21:18:22 2019  | Hide | Hide all
JenneAM_fiberPD_cals.pdf
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