HFCT-721XPD Avago Technologies US Inc., HFCT-721XPD Datasheet - Page 9

• Manufacturer Part Number: HFCT-721XPD
• Description: Fiber Optic Transceiver,Module
• Manufacturer: Avago Technologies US Inc.

Specifications of HFCT-721XPD

• Data Rate: 10.52Gbps
• Wavelength: 1310nm
• Applications: General Purpose
• Voltage - Supply: 3.135 V ~ 3.465 V
• Connector Type: LC Duplex
• Mounting Type: Panel Mount
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Digital Diagnostic Interface and Serial Identification
The 2-wire serial interface is explicitly defined in the XFP
MSA Rev 4.0. 2-wire timing specifications and the structure
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 diagnostic information
providing the opportunity for Predictive Failure Identifica-
tion, Compliance Prediction, Fault Isolation and Compo-
nent Monitoring. T he upper address space tables are used
for less frequently accessed functions such as serial ID, user
writeable EEPROM, reserved EEPROM and diagnostics and
control spaces for future standards definition, as well as
Avago Technologies-specific functions.
Predictive Failure Identification
The diagnostic information allows the host system to
identify potential link problems. Once identified, a “fail
over” technique can be used to isolate and replace suspect
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 plant and remote
transmitter.
Fault Isolation
The diagnostic information can allow the host to pinpoint
the location of a link problem and accelerate system ser-
vicing and minimize downtime.
Component Monitoring
As part of host system qualification and verification, real
time transceiver diagnostic information can be combined
with system level monitoring to ensure performance and
operating environment are meeting application require-
ments.
Transceiver Internal Temperature
Temperature is measured on the HFCT-721XPD using s ens-
ing circuitry mounted on the internal PCB. The measured
temperature will generally be cooler than laser junction
and warmer than XFP case and can be indirectly correlated
to XFP 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 fluctuations such as a
failure in the system thermal control. For more informa-
tion on correlating internal temperature to case or laser
junction contact Avago Technologies.

Transmitter Laser dc Bias Current
Laser bias current is measured using sensing circuitry lo-
cated on the transmitter laser driver IC. Normal variations
in laser bias current are expected to accommodate the
impact of changing transceiver temperature and supply
voltage operating points. The HFCT-721XPD uses a closed
loop laser bias feedback circuit to maintain constant optical
power. T his c ircuit c ompensates f or n ormal l aser p arametric
variations i n q uantum e fficiency, f orward v oltage a nd l asing
threshold due to changing transceiver operating points.
Transmitted Average Optical Output Power
Variations in average optical power are not expected under
normal operation because the HFCT-721XPD uses a closed
loop laser bias feedback circuit to maintain constant optical
power. T his c ircuit c ompensates f or n ormal l aser p arametric
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 measurements are a valu-
able asset for installers to verify cable plant compliance.
Drifts in average power can be observed from the cable
plant and remote transmitter for potential predictive
failure use. Received average optical power can be used
for fault isolation.