A much-delayed alog: I completed DC and RF calibration checks on both IMC WFS using the 980 nm AM laser.  The conclusion is that the WFS work, by and large.  For two segments of WFS_B, the readout is about 15% lower than expected.  And for both WFS, segments (1, 2, 3, 4) in the DC outputs apparently correspond to segments (4, 3, 2, 1) in the RF outputs.  Details below.

Devices tested
WFS_A: head S1300267 / demod S1001018
WFS_B: head S1300268 / demod S1001034
WFS interface chassis S1200441

AM laser source
4 mW nominal output
0.1 Vpp RF drive at 24.078473 MHz
RF input calibration is 13 mW/V => RF power is 1.3 mW

Calibration factors
WFS PD responsivity at 980 nm is in the range 0.5-0.6 mA/mW
WFS PD DC transimpedance is 1 V/mA
WFS_A PD RF transimpedance is (0.38, 0.43, 0.37, 0.38) V/mA for segments (4, 3, 2, 1)
WFS_B PD RF transimpedance is (0.46, 0.47, 0.40, 0.46) V/mA for segments (4, 3, 2, 1)
WFS interface DC gain is 1 (gain setting = LOW)
Gain through demod board is 5 V(dc)/V(rf) (front panel) or 10 V(dc)/V(rf) (differential output to ADC)
ADC conversion is 1638 ct/V

Results
Colored as follows: up to 5% deviation 5-10% deviation 10-15% deviation)
 
Parameter
 
Measured WFS_A
 
Measured WFS_B
 
Expected value
 
 
DC SUM output (ct)
 
3820
 
3760
 
3300-3900
(4 mW * 0.5 or 0.6 mA/mW * 1 V/mA * 1 * 1638 ct/V)
 
 
Responsivity at 980 nm (mA/mW)
 
0.58
 
0.57
 
0.5-0.6
 
 
DC SEG1 output (ct)
 
940
 
470
 
bigger than zero, smaller than the DC SUM
 
 
DC SEG2 output (ct)
 
800
 
840
 
bigger than zero, smaller than the DC SUM
 
 
DC SEG3 output (ct)
 
1210
 
1200
 
bigger than zero, smaller than the DC SUM
 
 
DC SEG4 output (ct)
 
870
 
1250
 
bigger than zero, smaller than the DC SUM
 
 
I/Q SEG1 output (V p-p)
 
0.330
 
0.560
 
A:0.330 B:0.570
(A: capture fraction 870/3820 * 1.3 mW * 0.58 mA/mW * 0.38 V/mA * 5)
(B: capture fraction 1250/3760 * 1.3 mW * 0.57 mA/mW * 0.46 V/mA * 5)
 
 
I/Q SEG2 output (V p-p)
 
0.440
 
0.460
 
A:0.440 B:0.470
(A: capture fraction 1210/3820 * 1.3 mW * 0.58 mA/mW * 0.37 V/mA * 5)
(B: capture fraction 1200/3760 * 1.3 mW * 0.57 mA/mW * 0.40 V/mA * 5)
 
 
I/Q SEG3 output (V p-p)
 
0.320
 
0.340
 
A:0.340 B:0.390
(A: capture fraction 800/3820 * 1.3 mW * 0.58 mA/mW * 0.43 V/mA * 5)
(B: capture fraction 840/3760 * 1.3 mW * 0.57 mA/mW * 0.47 V/mA * 5)
 
 
I/Q SEG4 output (V p-p)
 
0.350
 
0.180
 
A:0.350 B:0.210
(A: capture fraction 940/3820 * 1.3 mW * 0.58 mA/mW * 0.38 V/mA * 5)
(B: capture fraction 470/3760 * 1.3 mW * 0.57 mA/mW * 0.46 V/mA * 5)
 
 
I/Q SEG1 output (ct p-p)
 
1040
 
1800
 
A:1070 B:1860
(A: expected SEG1 Vpp * 2 * 1638 ct/V)
(B: expected SEG1 Vpp * 2 * 1638 ct/V)
 
 
I/Q SEG2 output (ct p-p)
 
1400
 
1500
 
A:1450 B:1550
(A: expected SEG2 Vpp * 2 * 1638 ct/V)
(B: expected SEG2 Vpp * 2 * 1638 ct/V)
 
 
I/Q SEG3 output (ct p-p)
 
1000
 
1100
 
A:1110 B:1270
(A: expected SEG3 Vpp * 2 * 1638 ct/V)
(B: expected SEG3 Vpp * 2 * 1638 ct/V)
 
 
I/Q SEG4 output (ct p-p)
 
1120
 
600
 
A:1150 B:700
(A: expected SEG4 Vpp * 2 * 1638 ct/V)
(B: expected SEG4 Vpp * 2 * 1638 ct/V)