AFBR-57J7APZ Datasheet, PDF (11/18 Pages) AVAGO TECHNOLOGIES LIMITED – Digital Diagnostic SFP, 850nm 6.144/7.3728 Gb/s, RoHS OBSAI/CPRI Compatible Optical Transceiver

Table 10. Transceiver Digital Diagnostic Monitor (Real Time Sense) Characteristics (TC = -40°C to 85°C, VccT, VccR = 3.3V ± 10%)
Parameter
Transceiver Internal
Temperature Accuracy
Transceiver Internal Supply
Voltage Accuracy
Symbol
T_INT
V_INT
Transmitter Laser DC Bias
I_INT
Current Accuracy
Transmitted Average Optical P_T
Output Power Accuracy
Received Average Optical
P_R
Input Power Accuracy
Min
Units
+/- 3.0 °C
+/- 0.1 V
+/- 10 %
+/- 3.0 dB
+/- 3.0 dB
Notes
Temperature is measured internal to the transceiver.
Valid from = -40°C to 85 °C case temperature.
Supply voltage is measured internal to the transceiver and
can, with less accuracy, be correlated to voltage at the SFP Vcc
pin. Valid over 3.3 V ± 10%.
I_INT is better than +/-10% of the nominal value.
Coupled into 50/125um multi-mode fiber.
Valid from 100 uW to 500 uW, avg.
Coupled from 50/125um multi-mode fiber.
Valid from 76 uW to 500 uW, avg.
Description of the Digital Diagnostic Data
Transceiver Internal Temperature
Temperature is measured on the AFBR-57J7APZ using
sensing circuitry mounted on the internal PCB. The
measured temperature will generally be cooler than laser
junction and warmer than SFP case and can be indirect-
ly correlated to SFP case or laser junction temperature
using thermal resistance and capacitance modeling. This
measurement can be used to observe drifts in thermal
operating point or to detect extreme temperature fluctu-
ations such as a failure in the system thermal control. For
more information on correlating internal temperature to
case or laser junction contact Avago Technologies.
Transceiver Internal Supply Voltage
Supply voltage is measured on the AFBR-57J7APZ using
sensing circuitry mounted on the internal PCB. Transmit
supply voltage (VccT) is monitored for this readback. The
resultant value can be indirectly correlated to SFP VccT
or VccR pin supply voltages using resistance modeling,
but not with the required accuracy of SFF-8472. Supply
voltage as measured will be generally lower than SFP Vcc
pins due to use of internal transient suppression circuitry.
As such, measured values can be used to observe drifts in
supply voltage operating point, be empirically correlated
to SFP pins in a given host application or used to detect
supply voltage fluctuations due to failure or fault in the
system power supply environment. For more information
on correlating internal supply voltage to SFP pins contact
Avago Technologies.
Transmitter Laser DC Bias Current
Laser bias current is measured using sensing circuitry
located on the transmitter laser driver IC. Normal varia-
tions in laser bias current are expected to accommo-
date the impact of changing transceiver temperature
and supply voltage operating points. The AFBR-57J7APZ
uses a closed loop laser bias feedback circuit to maintain
constant optical power. This circuit compensates for
normal VCSEL parametric variations in quantum efficien-
cy, forward voltage and lasing threshold due to changing
transceiver operating points. Consistent increases in laser
bias current observed at equilibrium temperature and
supply voltage could be an indication of laser degrada-
tion. For more information on using laser bias current for
predicting laser lifetime, contact Avago Technologies.
Transmitted Average Optical Output Power
Transmitted average optical power is measured using
sensing circuitry located on the transmitter laser driver
IC and laser optical subassembly. Variations in average
optical power are not expected under normal operation
because the AFBR-57J7APZ uses a closed loop laser bias
feedback circuit to maintain constant optical power.
This circuit compensates for normal VCSEL parametric
variations due to changing transceiver operating points.
Only under extreme laser bias conditions will significant
drifting in transmitted average optical power be observ-
able. Therefore it is recommended Tx average optical
power be used for fault isolation, rather than predictive
failure purposes.
Received Average Optical Input Power
Received average optical power is measured using
detecting circuitry located on the receiver preamp and
quantizer ICs. Accuracy is +/- 3.0 dB, but typical accuracy
is +/- 2.0 dB. This measurement can be used to observe
magnitude and drifts in incoming optical signal level for
detecting cable plant or remote transmitter problems.
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