4
Figure 4. MSA required power supply lter
V
CC
T
0.1 µF
0.1 µF 10 µF
1 µH
1 µH
0.1 µF 10 µF
3.3 V
SFP MODULE
V
CC
R
HOST BOARD
Functional Data I/O
Avago’s AFCT-571xZ transceiver is designed to accept
industry standard di erential signals. The transceiver
provides an AC-coupled, internally terminated data
interface. Bias resistors and coupling capacitors have
been included within the module to reduce the number
of components required on the customer’s board.
Figure 2 illustrates the recommended interface circuit.
Digital Diagnostic Interface and Serial Identi cation
The AFCT-571xZ family complies with the SFF-8074i
speci cation, which de nes the module’s serial identi -
cation protocol to use the 2-wire serial CMOS EEPROM
protocol of the ATMEL AT24C01A or similar. Standard
SFP EEPROM bytes 0-255 are addressed per SFF-8074i at
memory address 0xA0 (A0h).
As an enhancement to the conventional SFP interface
de ned in SFF-8074i, the AFCT-5715Z is also compliant
to SFF-8472 (the digital diagnostic interface for SFP).
This enhancement adds digital diagnostic monitoring
to standard SFP functionality, enabling failure predic-
tion, fault isolation, and component monitoring capa-
bilities.
Using the 2-wire serial interface, the AFCT-5715Z
provides real time access to transceiver internal supply
voltage and temperature, transmitter output power,
laser bias current and receiver average input power,
allowing a host to predict system compliance issues.
These ve parameters are internally calibrated, per the
MSA. New digital diagnostic information is accessed
per SFF-8472 using EEPROM bytes 0-255 at memory
address 0xA2 (A2h).
The digital diagnostic interface also adds the ability to
disable the transmitter (TX_DISABLE), monitor for Trans-
mitter Faults (TX_FAULT) and monitor for Receiver Loss
of Signal (RX_LOS).
Contents of the MSA-compliant serial ID memory are
shown in Tables 10 through 14. The SFF-8074i and
SFF-8472 speci cations are available from the SFF
Committee at http://www.s committee.org.
The I2C accessible memory page address 0xB0 is used
internally by SFP for the test and diagnostic purposes
and it is reserved.
Predictive Failure Identi cation
The diagnostic information allows the host system
to identify potential link problems. Once identi ed, a
fail-over technique can be used to isolate and replace
suspect devices before system uptime is impacted.
TX_FAULT
A laser fault or a low VCC condition will activate the
transmitter fault signal, TX_FAULT, and disable the laser.
This signal is an open collector output (pull-up required
on the host board); A low signal indicates normal laser
operation and a high signal indicates a fault. The TX_
FAULT will be latched high when a laser fault occurs and
is cleared by toggling the TX_DISABLE input or power
cycling the transceiver. The TX_FAULT is not latched
for Low VCC. The transmitter fault condition can also
be monitored via the two-wire serial interface (address
A2h, byte 110, bit 2).
Eye Safety Circuit
Under normal operating conditions, the laser power
will be maintained below the eye-safety limit. If the
eye safety limit is exceeded at any time, a laser fault will
occur and the TX_FAULT output will be activated.
Receiver Section
The receiver section for the AFCT-571xZ contains an
InGaAs/InP photo detector and a preampli er mounted
in an optical subassembly. This optical subassembly is
coupled to a post ampli er/decision circuit on a circuit
board. The design of the optical subassembly provides
better than 12 dB Optical Return Loss (ORL).
Connection to the receiver is provided via a LC optical
connector.
RX_LOS
The receiver section contains a loss of signal (RX_LOS)
circuit to indicate when the optical input signal power
is insu cient for Gigabit Ethernet compliance. A high
signal indicates loss of modulated signal, indicating link
failure such as a broken ber or a failed transmitter. RX_
LOS can be also be monitored via the two-wire serial
(address A2h, byte 110, bit 1).
