The scale and {HEAD ~ structure} of the first and second photodiodes and the magnitude of the reverse bias applied across each photodiode are selected to produce substantially the same dark current flowing through {TAIL ~ each photodiode} 
The scale and { HEAD ~ structure } of the first and second photodiodes and the magnitude of the reverse bias applied across each photodiode are selected to produce substantially the same dark current flowing through { TAIL ~ each photodiode }
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL