Bookham New Focus 2307, User Manual, Page: 18 / 26

Large-Area Balanced Photoreceivers Frequency Response and Noise • 17
Common Mode Rejection
Using the Model 23X7 balanced photoreceivers with
equal signal powers on each photodiode results in an
output with reduced common mode signal. The
common-mode rejection ratio, or CMRR, is a
measurement of the effectiveness of the balanced
subtraction.
Figure 6 shows the CMRR of each model using the
following definition:
CMRR = 20 · log( V
out1
- V
out2
)/ V
out1
)
.
Figure 6:
Typical CMRR
for the
Model 2307
and Model
2317 at the low
gain settings
Model 2307 CMRR (Low gain setting)
-50
-40
-30
-20
-10
0
10
0 200 400 600 800 1000 1200 1400
Frequency (khz)
Frequency Response (dB)
I1,I2
I1-I2
Model 2317 CMRR (Low Gain setting)
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
5
0 100 200 300 400
Frequency (khz)
Frequency Response (dB)
I1,I2
I1-I2
23x7 LA Blncd Rcvr revA.fm Page 17 Tuesday, September 28, 2004 1:59 AM