HFBR-53D3 查看數據表（PDF） - HP => Agilent Technologies

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HFBR-53D3

1 x 9 Fiber Optic Transceivers for Fibre Channel

HP => Agilent Technologies 

4

APPLICATION SUPPORT

Optical Power Budget

and Link Penalties

The worst-case Optical Power

Budget (OPB) in dB for a fiber-

optic link is determined by the

difference between the minimum

transmitter output optical power

(dBm avg.) and the lowest receiver

sensitivity (dBm avg.). This OPB

provides the necessary optical

signal range to establish a working

fiber-optic link. The OPB is

allocated for the fiber-optic cable

length and the corresponding link

penalties. For proper link

performance, all penalties that

affect the link performance must

be accounted for within the link

optical power budget.

Data Line

Interconnections

Agilent’s HFBR/HFCT-53D3 fiber-

optic transceiver is designed to

directly couple to +5 V PECL

signals. The transmitter inputs

are internally dc-coupled to the

laser driver circuit from the

transmitter input pins (pins 7, 8).

There is no internal, capacitively-

coupled 50 Ohm termination

resistance within the transmitter

input section. The transmitter

driver circuit for the laser light

source is a dc-coupled circuit.

This circuit regulates the output

optical power. The regulated light

output will maintain a constant

output optical power provided the

data pattern is reasonably

balanced in duty factor. If the

data duty factor has long,

continuous state times (low or

high data duty factor), then the

output optical power will

gradually change its average

output optical power level to its

preset value.

As for the receiver section, it is

internally ac-coupled between the

preamplifier and the post-

amplifier stages. The actual Data

and Data-bar outputs of the post-

amplifier are dc-coupled to their

respective output pins (pins 2, 3).

Signal Detect is a single-ended,

+5 V PECL output signal that is

dc-coupled to pin 4 of the module.

Signal Detect should not be ac-

coupled externally to the

follow-on circuits because of its

infrequent state changes.

Caution should be taken to account

for the proper interconnection

between the supporting Physical

Layer integrated circuits and this

HFBR/HFCT-53D3 transceiver.

Figure 3 illustrates a

recommended interface circuit

for interconnecting to a +5 V dc

PECL fiber-optic transceiver.

Some fiber-optic transceiver

suppliers’ modules include

internal capacitors, with or

without 50 Ohm termination, to

couple their Data and Data-bar

lines to the I/O pins of their

module. When designing to use

these type of transceivers along

with Agilent transceivers, it is

important that the interface

circuit can accommodate either

internal or external capacitive

coupling with 50 Ohm termination

components for proper operation

of both transceiver designs. The

internal dc-coupled design of the

HFBR/HFCT-53D3 I/O

connections was done to provide

the designer with the most

flexibility for interfacing to

various types of circuits.

Eye Safety Circuit

For an optical transmitter device

to be eye-safe in the event of a

single fault failure, the transmitter

must either maintain normal, eye-

safe operation or be disabled.

In the HFBR-53D3 there are three

key elements to the laser driver

safety circuitry: a monitor diode,

a window detector circuit and

direct control of the laser bias.

The window detection circuit

monitors the average optical

power using the monitor diode. If

a fault occurs such that the

transmitter dc regulation circuit

cannot maintain the preset bias

conditions for the laser emitter

within ±20%, the transmitter will

automatically be disabled. Once

this has occurred, only an

electrical power reset will allow

an attempted turn-on of the

transmitter.

The HFCT-53D3 utilizes an

integral fiber stub along with a

current limiting circuit to

guarantee eye-safety. It is

intrinsically eye safe and does not

require shut down circuitry.

Signal Detect

The Signal Detect circuit provides

a deasserted output signal that

implies the link is open or the

transmitter is OFF. The Signal

Detect threshold is set to

transition from a high to low state

between the minimum receiver

input optional power and -30 dBm

avg. input optical power

indicating a definite optical fault

(e.g. unplugged connector for the

receiver or transmitter, broken

fiber, or failed far-end transmitter

or data source). A Signal Detect

indicating a working link is

functional when receiving

encoded 8B/l0B characters. The

Signal Detect does not detect

receiver data error or error-rate.

Data errors are determined by

Signal processing following the

transceiver.

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