J. Kissel, T. Roocke

I was crossing the t's and dotting the i's on our documentation to better understand what calibration / compensation to install into the new SPI front-end / MEDM infrastructure. 

As such I was reconciling / validating the calibration info that Sina put in LHO:89739 (originally informed by derivations in E2600104) against the info Tom put in the three travelers 
    - S2500711 (Variant 1 for the HAM2 YAG444s), 
    - S2500712 (Variant 2 for the HAM3 4x FFD200s and one YAG444), and
    - S2500713 (Variant 3 for the HAM3 additional 2x FFD200s)

Two things were amiss:
(1) The values of resistors and capacitors were not consistent between Sina's "R4 Resistor value now (kohm)" and "C5 capacitor value now (pF)" columns, and what Tom stated in the traveler update. As such, I asked Tom to give me more detailed confirmation -- and he delivered excellently:
    S2500711 (Variant 1 for the HAM2 YAG444s)
    CH1-4 
        . R4 = 1.54kohm (P1.54KFCT-ND) 
        . C4 = 2.2nF (399-8171-1-ND)

    S2500712 (Variant 2 for the HAM3 4x FFD200s and one YAG444)
    CH1-2 
        . R4 = 4.99kohm (P4.99KFCT-ND) 
        . C4 = 560pF (PCC561BCT-ND)
    CH3-8 
        . R4 = 3.32kohm (P3.32KFCT-ND)
        . C4 = 1nF (PCC102BCT-ND)

    S2500713 (Variant 3 for the HAM3 additional 2x FFD200s)
    CH1-2 
        . R4 = 53.6kohm (P53.6KFCT-ND) 
        . C4 = 220pF (478-1484-1-ND)

(2) In our testing of the TIAs both *before* and *after* these component values were installed, we were comparing values measured power values with a Thorlabs S121C power meter (in [mW]) against the TIA ADC output voltage on the positive leg *only* (in [V]), after having verified that the negative leg consistently reported the negative of the positive leg on all channels. 

In E2600104-v1 the AA column for "PD Calibration" -- and thus Sina's "PD calibration (mW/V)" column in LHO:89739 is the ratio of the power and positive leg only, and thus missing a factor of 2.0.

So ... there's the updated table, with 
    - the transimpedance gain, "TIA gain" calculated as R4 * 2 [V_SE/V_DIFF], with the factor of two from the last ADC driver stage 
    - when engaged (rather than bypassed), the whitening stage with 
           z1 = 1 / ( 2*pi* (R1*C1 + R3*C2 + R3*C1) )
           z2 = (R1*C1 + R3*C2 + R3*C1) / ( 2*pi* (R1*C1*R3*C2) )
           p1 = 1 / ( 2*pi* (R1*C1) )
           p2 = 1 / ( 2*pi* (R3*C2))
    - FBR_PWRIN single-element PD Calibration at DC
            (power at PD) / ( 2 * (ADC volts pos leg) )
    - IFO single-element PD calibration at DC
            (SIG power + LO power) / ( 2 * (SIG ADC volts pos leg + LO ADC volts pos leg) )
    - QPD segment calibration
            percentage of voltage = ADC volts pos leg of each segment / (total pos leg voltage on all segments)
            (total power at QPD * percentage of voltage) / ( 2 * (ADC volts pos leg of each segment) ) 
    - a 16 bit ADC with 40 Vpp DIFFERENTIAL range, i.e. 40 / 2^16 = 6.1035e-4 [V/ct] or 2^16 / 40 = 1638.4 [ct/V] (see T1100538)
           


    DIGITAL NAME     ANALOG    R4        C4       TIA Gain   PD/SEG Calibration   TIA HF Pole    Whitening 
                     NAME      [kOhm]    [nF]     [V/A]      [mW/V]               [kHz]          (z1,z2:p1,p2) [Hz] 
QPDA
    OL_QPD_A_SEG1    CH1       1.54      2.20     3.08e3     2.0556               46.976         (0.394, 8.06e6: 39.8, 79.6e3)    
    OL_QPD_A_SEG2    CH2       1.54      2.20     3.08e3     2.0556               46.976         (0.394, 8.06e6: 39.8, 79.6e3)    
    OL_QPD_A_SEG3    CH3       1.54      2.20     3.08e3     2.0556               46.976         (0.394, 8.06e6: 39.8, 79.6e3)    
    OL_QPD_A_SEG4    CH4       1.54      2.20     3.08e3     2.0556               46.976         (0.394, 8.06e6: 39.8, 79.6e3)    


IFO
    IFO_MEAS_A       CH1       4.99      0.56     9.98e3     1.0959               56.955         bypassed
    IFO_MEAS_B       CH2       4.99      0.56     9.98e3     1.0619               56.955         bypassed
    IFO_REF_A        CH3       3.32      1.00     6.64e3     0.6042               47.938         bypassed
    IFO_REF_B        CH4       3.32      1.00     6.64e3     0.6304               47.938         bypassed   

QPDB
    OL_QPD_B_SEG1    CH5       3.32      1.00     6.64e3     0.3667               47.938         (0.394, 8.06e6: 39.8, 79.6e3)  
    OL_QPD_B_SEG2    CH6       3.32      1.00     6.64e3     0.3667               47.938         (0.394, 8.06e6: 39.8, 79.6e3)
    OL_QPD_B_SEG3    CH7       3.32      1.00     6.64e3     0.3667               47.938         (0.394, 8.06e6: 39.8, 79.6e3)
    OL_QPD_B_SEG4    CH8       3.32      1.00     6.64e3     0.3667               47.938         (0.394, 8.06e6: 39.8, 79.6e3)

POWER
    FBR_PWRIN_MEAS   CH1      53.60      0.22   107.2e3      0.1154               13.497         bypassed 
    FBR_PWRIN_REF    CH2      53.60      0.22   107.2e3      0.1176               13.497         bypassed 


I've updated E2600104 (the google sheet), exported it and uploaded that to -v2 to corroborate.