AFCT-5701Z_15 Datasheet, PDF (4/20 Pages) AVAGO TECHNOLOGIES LIMITED – Optical Transceivers with Optional DMI for Gigabit Ethernet Fibre Channel

TX_FAULT
Functional Data I/O
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-570xZ contains an
InGaAs/InP photo detector and a preamplifier mounted
in an optical subassembly. This optical subassembly is
coupled to a post amplifier/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 insufficient for Fibre Channel compliance. A high
signal indicates loss of modulated signal, indicating
link failure such as a broken fiber or a failed transmit-
ter. RX_LOS can be also be monitored via the two-wire
serial (address A2h, byte 110, bit 1).
V_CCT
0.1 µF
V_CCR
0.1 µF
10 µF
1 µH
1 µH
0.1 µF 10 µF
3.3 V
SFP MODULE
HOST BOARD
Avago’s AFCT-570xZ transceiver is designed to accept
industry standard differential 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 Identification
The AFCT-570xZ family complies with the SFF-8074i
specification, which defines the module’s serial identi-
fication 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
defined in SFF-8074i, the AFCT-5705Z 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-5705Z pro-
vides 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 five 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 specifications are available from the SFF Commit-
tee at http://www.sffcommittee.org.
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.
Figure 4. MSA required power supply filter
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