2

Overview

Avago Technologies’HFBR-5911LZ/ALZ optical transceiver

supports high-speed serial links over multimode optical

fiber at signaling rates of up to 1.25 Gb/s. Compliant

with the Small Form Factor (SFF) Multi Source Agreement

(MSA)for2x5pinLCDuplextransceiversandIEEE802.3

specification for Gigabit Ethernet (GbE) links (1000BASE-

SX), the part is interoperable and interchangeable with

other conformant devices. Supported Gigabit Ethernet

link lengths are described in Table 1, but the transceiver

can also be used for other high-speed serial applications,

such as iSCSI.

The SFF package of the HFBR-5911LZ/ALZ allows design-

ers of Gigabit Ethernet networking equipment to maxi-

mize their use of available board space. The footprint

of the HFBR-5911LZ/ALZ is significantly smaller than

those of other GbE transceivers formats - 25% smaller

thanSFPcageassemblies,30%smallerthantraditional

1 x 9 transceivers and 70% smaller than GBIC rail as-

semblies. The HFBR-5911LZ/ALZ trace keep-out area is

lessthan10%aslargeasthatrequiredbySFPtransceiv-

ers. For applications not requiring hot-pluggability, the

HFBR-5911LZ/ALZ offers a more space-efficient package

without the additional cost and complexity imposed by

pluggable architecture.

ModuleDiagrams

The major functional components of the HFBR-5911LZ/ALZ

are illustrated in Figure 2 page 9. The external configu-

ration of the transceiver is depicted in Figure 3 page 10

while the host board and front panel layouts defined by

theSFFMSAareshowninFigure4,page11.

TransmitterSection

The transmitter section consists of the Transmitter Optical

Subassembly (TOSA) and laser driver circuitry. The TOSA,

containingan850nmVCSEL(VerticalCavitySurfaceEmit-

ting Laser) light source, is located at the optical interface and

mates with the LC optical connector. The TOSA is driven by

acustomICwhichusestheincomingdifferentialPECLlogic

signals to modulate the laser diode drive current. This Tx laser

driver circuit regulates the optical output power at a constant

level provided that the incoming data pattern is dc balanced

(8B10Bcodeforexample).

Tx_Disable

The HFBR-5911LZ/ALZ accepts a TTL transmit disable

control signal input which shuts down the transmitter. 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 5 page 12.

A pull-down resistor enables the laser if the line is not

connected on the host board.

Host systems should allow a 10 ms interval between suc-

cessive assertions of this control signal.

EyeSafetyCircuit

The HFBR-5911LZ/ALZ provides Class 1 eye safety by

design and has been tested for compliance with the

requirements listed in Table 11. The eye safety circuit

continuously monitors optical output power levels and

will disable the transmitter upon detecting an unsafe

condition. Such unsafe conditions can be due to inputs

or faults within the transceiver.

ReceiverSection

The receiver section includes the Receiver Optical Subassem-

bly (ROSA) and the amplification/quantization circuitry. The

ROSA,containingaPINphotodiodeandcustomtransimped-

ance preamplifier, is located at the optical interface and mates

with the LC optical connector. The ROSA output is fed to a

custom IC that provides post-amplification and quantization.

SignalDetect

The post-amplification/quantizer IC also includes transition

detection circuitry that monitors the ac level of the incoming

optical signal and provides a TTL status signal to the host. An

adequate optical input results in a high output while a low

Signal Detect output indicates an unusable optical input. The

Signal Detect thresholds are set so that a low output indicates

a definite optical fault has occurred (e.g., disconnected or

broken fiber connection to receiver, failed transmitter, etc.).