AFBR-720XPDZ Datasheet, PDF (11/15 Pages) AVAGO TECHNOLOGIES LIMITED – 10GbE XFP 850 nm 10Gbps Optical Transceiver

Digital Diagnostic Interface and Serial Identification
Transceiver Internal Temperature
The 2-wire serial interface is explicitly defined in the XFP
MSA Rev 4.0. 2-wire timing specifications and the struc-
ture of the memory map are per XFP MSA Rev 2.0. The
normal 256 Byte I2C address space is divided into lower
and upper blocks of 128 Bytes. The lower block of 128
Bytes is always directly available and is used for diagnos-
tic information providing the opportunity for Predictive
Failure Identification, Compliance Prediction, Fault Isola-
tion and Component Monitoring. The upper address
space tables are used for less frequently accessed func-
tions such as serial ID, user writeable EEPROM, reserved
EEPROMand diagnostics and control spaces for future
standards definition, as well as Avago Technologies-spe-
cific functions.
Predictive Failure Identification
The diagnostic information allows the hostsystem to
identify potential link problems.Once identified, a “fail
over” technique can be used to isolate and replace sus-
pect devices before system uptime is impacted.
Compliance Prediction
The real-time diagnostic parameters can be monitored
to alert the system when operating limits are exceeded
and compliance cannot be ensured.As an example, the
real time average receive optical power can be used to
assess the compliance of the cable plantand remote
transmitter.
Fault Isolation
The diagnostic information can allow the host to pin-
point the location of a link problem and accelerate sys-
tem servicing and minimize downtime.
Component Monitoring
As partof hostsystem qualification and verification,
real time transceiver diagnostic information can be
combined with system level monitoring to ensure per-
formance and operating environmentare meeting ap-
plication requirements.
Temperature is measured on the AFBR-720XPDZ us-
ing sensing circuitry mounted on the internal PCB.
The measured temperature will generally be cooler
than laser junction and warmer than XFPcase and can
be indirectly correlated to XFPcase or laser junction
temperature using thermal resistance and capacitance
modeling. This measurementcan be used to observe
drifts in thermal operating pointor to detectextreme
temperature fluctuations such as a failure in the system
thermal control. For more information on correlating
internal temperature to case or laser junction contact
Avago Technologies.
Transmitter Laser DC Bias Current
Laser bias currentis measured using sensing circuitry
located on the transmitter laser driver IC. Normal varia-
tions in laser bias current are expected to accommodate
the impactof changing transceiver temperature and
supply voltage operating points. The AFBR-720XPDZ
uses a closed loop laser bias feedback circuit to maintain
constant optical power. This circuit compensates for nor-
mal laser parametric variations in quantum efficiency,
forward voltage and lasing threshold due to changing
transceiver operating points.
Transmitted Average Optical Output Power
Variations in average optical power are notexpected
under normal operation because the AFBR-720XPDZ
uses a closed loop laser bias feedback circuit to main-
tain constantoptical power. This circuitcompensates
for normal laser parametric variations due to changing
transceiver operating points. Only under extreme laser
bias conditions will significantdrifting in transmitted
average optical power be observable. Therefore it is rec-
ommended Tx average optical power be used for fault
isolation, rather than predictive failure purposes.
Received Average Optical Input Power
Received average optical power measurements are a
valuable asset for installers to verify cable plant compli-
ance. Drifts in average power can be observed from the
cable plant and remote transmitter for potential predic-
tive failure use. Received average optical power can be
used for fault isolation.
Auxilliary Monitors
In addition to the parameters mentioned above, 3.3V
Supply Voltage (AUX1) is also reported as auxilliary pa-
rameter 1.
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