AFBR-57J9AMZ Datasheet, PDF (2/17 Pages) AVAGO TECHNOLOGIES LIMITED – RoHS OBSAI/CPRI Compatible Optical Transceiver

Optical Interface
Light from Fiber
Receiver
Photo-Detector
Ampli cation
&
Quantization
Electrical Interface
Rate Select
RD+ (Receive Data)
RD- (Receive Data)
Rx Loss Of Signal
EEPROM
CONTROLLER
EEPROM
MOD-DEF2 (SDA)
MOD-DEF1 (SCL)
MOD-DEF0
Light to Fiber
Transmitter
VCSEL
Laser Driver &
Safety Circuit
TX_DISABLE
TD+ (Transmit Data)
TD- (Transmit Data)
TX_FAULT
Figure 1. Transceiver Functional Diagram
Digital Diagnostic Interface and Serial Identification
The 2-wire serial interface is based on ATMEL AT24C01A
series EEPROM protocol and signaling detail. Conven-
tional EEPROM memory, bytes 0-255 at memory address
0xA0, is organized in compliance with INF-8074. New
digital diagnostic information, bytes 0-255 at memory
address 0xA2, is compliant to SFF-8472. The new diag-
nostic information provides the opportunity for Predic-
tive Failure Identification, Compliance Prediction, Fault
Isolation and Component Monitoring.
Transmitter Section
The transmitter section includes consists of the Transmit-
ter Optical SubAssembly (TOSA) and laser driver circuitry.
The TOSA, containing an 850nm VCSEL (Vertical Cavity
Surface Emitting Laser) light source, is located at the
optical interface and mates with the LC optical connector.
The TOSA is driven by a custom IC which uses the
incoming differential high speed logic signal to modulate
the laser diode driver current. This Tx laser driver circuit
regulates the optical power at a constant level provided
the incoming data pattern is dc balanced (8B/10B code,
for example).
Transmit Disable (Tx_Disable)
The AFBR-57J9AMZ accepts a TTL and CMOS compat-
ible transmit disable control signal input (pin 3) which
shuts down the transmitter optical output. A high signal
implements this function while a low signal allows
normal transceiver operation. In the event of a fault (e.g.
eye safety circuit activated), cycling this control signal
resets the module as depicted in Figure 4. An internal
pull up resistor disables the transceiver transmitter until
the host pulls the input low. Host systems should allow
a 10ms interval between successive assertions of this
control signal. Tx_Disable can also be asserted via the
two-wire serial interface (address A2h, byte 110, bit 6)
and monitored (address A2h, byte 110, bit 7).
The contents of A2h, byte 110, bit 6 are logic OR’d with
hardware Tx_Disable (pin 3) to control transmitter
operation..
Transmit Fault (Tx_Fault)
A catastrophic laser fault will activate the transmitter
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 transmitter fault condition can also be
monitored via the two-wire serial interface (address A2,
byte 110, bit 2).
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