AFCT-57R5APZ datasheet(3/19 Pages) BOARDCOM

3 / 19 page

Figure 1. Transceiver functional diagram.

Transmitter Section

The transmitter section includes a 1310-nm Fabry Perot

(FP) laser and a transmitter driver circuit. The driver circuit

maintains a constant average optical power output

with Fibre Channel and Ethernet 8B/10B coded data.

Optical connection to the transmitter is provided via an

LC 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 AFCT-57R5APZ 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 10 ms 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).

Eye Safety Circuit

The AFCT-57R5APZ provides Class 1 (single fault tolerant)

eye safety by design and has been tested for compliance

with the requirements listed in Table 1. The eye safety

circuit continuously monitors the optical output power

level and will disable the transmitter upon detecting an

unsafe condition beyond the scope of Class 1 certifica-

tion. Such unsafe conditions can be due to inputs from

the host board (Vcc fluctuation, unbalanced code) or a

fault within the transceiver.

LIGHT FROM FIBER

LIGHT TO FIBER

PHOTO-DETECTOR

RECEIVER

AMPLIFICATION

& QUANTIZATION

RD+ (RECEIVE DATA)

RD– (RECEIVE DATA)

Rx LOSS OF SIGNAL

VCSEL

TRANSMITTER

LASER

DRIVER &

SAFETY

CIRCUITRY

TX_DISABLE

TD+ (TRANSMIT DATA)

TD– (TRANSMIT DATA)

TX_FAULT

ELECTRICAL INTERFACE

MOD-DEF2 (SDA)

MOD-DEF1 (SCL)

MOD-DEF0

CONTROLLER & MEMORY

OPTICAL INTERFACE

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