AFCT-5745Z datasheet(2/18 Pages) BOARDCOM

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Functional Description

Receiver Section Design

The receiver section for the AFCT-5745Z contains an

InGaAs/InP photo detector and a preamplifier mounted

in an optical subassembly. This optical subassembly is

coupled to a postamplifier/decision circuit on a circuit

board. The postamplifier is ac coupled to the preamplifier.

The coupling capacitors are chosen to pass the SONET/

SDH test pattern at 155 Mb/s, 622 Mb/s and 2.488 Gb/s

without significant distortion or performance penalty.

For multirate applications the sensitivity will meet the

maximum SONET specification for OC48 across all da-

tarates (-19dBm) for 223-1 PRBS patterns as well as for

dc balanced codes, e.g. 8B/10B. For codes that have a

significantly lower frequency content, jitter and pulse

distortion could be degraded.

Loss of Signal

The Loss of Signal (LOS) output indicates that the optical

input signal to the receiver does not meet the minimum

detectable level for compliant signals. When LOS is high

it indicates loss of signal. When LOS is low it indicates

normal operation. The Loss of Signal thresholds are set

to indicate a definite optical fault has occurred (eg., dis-

connected or broken fiber connection to receiver, failed

transmitter).

Transmitter Section Design

A schematic diagram for the transmitter is shown in Fig-

ure 1. The AFCT-5745xPZ incorporates an FP laser as its

optical source, the AFCT-5745xTPZ incorporates an DFB

laser as its optical source. All part numbers have been

designed to be compliant with IEC 825 and CDRH eye

safety requirements. The optical output is controlled by

a custom IC that detects the laser output via the monitor

photodiode. This IC provides both dc and ac current drive

to the laser to ensure correct modulation, eye diagram

and extinction ratio over temperature, supply voltage

and operating life.

TX_FAULT

The AFCT-5745Z modules feature a transmit fault control

signal output which when high indicates a laser transmit

fault has occurred and when low indicates normal laser

operation. A transmitter fault condition can be caused

by deviations from the recommended module operating

conditions or by violation of eye safety conditions. A fault

is cleared by cycling the TX_DISABLE control input.

TX_DISABLE

The AFCT-5745Z accepts a transmit disable control signal

input which shuts down the transmitter. A high signal

implements this function while a low signal allows nor-

mal laser operation. In the event of a fault (eg., eye safety

circuit activated), cycling this control signal resets the

module. The TX_DISABLE control should be actuated

upon initialization of the module.

Digital Diagnostic Interface and Serial Identification

(EEPROM)

The AFCT-5745Z complies with both SFF-8074i (SFP) and

SFF-8472 (Digital Diagnostic SFP) specifications available

from the SFF Committee at http://www.sffcommittee.org.

The AFCT-5745Z adds digital diagnostic monitoring to

standard SFP functionality, enabling failure prediction,

fault islolation, and component monitoring capabilities.

The transceiver continues to use the 2-wire I2C compat-

ible serial interface. Standard SFP EEPROM bytes 0-255

are addressed per SFF-8074i at memory address 0xA0

(A0h). New digital diagnostic information is accessed per

SFF-8472 using EEPROM bytes 0-255 at memory address

0xA2 (A2h).

The AFCT-5745Z 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 compli-

ance issues.

These 5 parameters are reported“internally”calibrated as

described in SFF-8472.

AFCT-5745Z Datasheet(PDF) 2 Page - Broadcom Corporation.

AFCT-5745Z Datasheet(HTML) 2 Page - Broadcom Corporation.

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