HFBR-5208AEMZ 查看數據表（PDF） - Avago Technologies

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HFBR-5208AEMZ

1 x 9 Fiber Optic Transceivers for 622 Mb/s ATM/SONET/SDH Applications

Avago Technologies 

Applications Information

Typical BER Performance of HFBR-5208xxxZ Receiver versus Input Optical Power Level

The HFBR-5208xxxZ transceiver can be operated at Bit-

Error-Ratio conditions other than the required BER = 1

x 10-10 of the 622 MBd ATM Forum 622.08 Mb/s Physical

Layer Standard and the ANSI T1.646a. The typical trade-

off of BER versus Relative Input Optical Power is shown

in Figure 1. The Relative Input Optical Power in dB is

referenced to the Input Optical Power parameter value

in the Receiver Optical Characteristics table. For better

BER condition than 1 x 10-10, more input signal is needed

(+dB). For example, to operate the HFBR-5208xxxZ at a

BER of 1 x 10-12, the receiver will require an input signal

approximately 0.6 dB higher than the -26 dBm level re-

quired for 1 x 10-10 operation, i.e. -25.4 dBm.

10 -2

10 -3

LINEAR EXTRAPOLATION OF

10 -4 THROUGH 10 -7 DATA

10 -4

ACTUAL DATA

10 -5

10 -6

10 -7

10 -8

10 -9

10 -10

10 -11

10 -12

10 -13

10 -14

10 -15

-5 -4 -3 -2 -1 0 1 2 3

Figure 1. Relative Input Optical Power - dBm Average.

An informative graph of a typical, short fiber transceiver

link per-formance can be seen in Figure 2. This figure is

useful for designing short reach links with time-based

jitter requirements. This figure indicates Relative Input

Optical Power versus Sampling Time Position within the

receiver output data eye-opening. The given curves are

at a constant bit-error-ratio (BER) of 10-10 for four differ-

ent signaling rates, 155 MBd, 311 MBd, 622 MBd and 650

MBd. These curves, called “tub” diagrams for their shape,

show the amount of data eye-opening time-width for

various receiver input optical power levels. A wider data

eye-opening provides more time for the clock recovery

circuit to operate within without creating errors. The

deeper the tub is indicates less input optical power is

needed to operate the receiver at the same BER condition.

Generally, the wider and deeper the tub is the better. The

Relative Input Optical Power amount (dB) is referenced to

the absolute level (dBm avg.) given in the Receiver Optical

Characteristics table. The 0 ns sampling time position

for this Figure 2 refers to the center of the Baud interval

for the particular signaling rate. The Baud interval is the

reciprocal of the signaling rate in MBd. For example, at

622 MBd the Baud interval is 1.61 ns, at 155 MBd the Baud

interval is 6.45 ns. Test conditions for this tub diagram are

listed in Figure 2.

The HFBR-5208xxxZ receiver input optical power require-

ments vary slightly over the signaling rate range of 20

MBd to 700 MBd for a constant bit-error-ratio (BER) of

10-10 condition. Figure 3 illustrates the typical receiver

relative input optical power varies by <0.7 dB over this

full range. This small sensitivity variation allows the

optical budget to remain nearly constant for designs that

make use of the broad signaling rate range of the HFBR-

5208xxxZ. The curve has been normalized to the input

optical power level (dBm avg.) of the receiver for 622 MBd

at center of the Baud interval with a BER of 10-10. The data

patterns that can be used at these signaling rates should

be, on average, balanced duty factor of 50%. Momentary

excursions of less or more data duty factor than 50% can

occur, but the overall data pattern must remain balanced.

Unbalanced data duty factor will cause excessive pulse-

width distortion, or worse, bit errors. The test conditions

are listed in Figure 3.

Recommended Circuit Schematic

When designing the HFBR-5208xxxZ circuit interface, there

are a few fundamental guidelines to follow. For example, in

the Recommended Circuit Schematic, Figure 4, the differential

data lines should be treated as 50 ohm Microstrip or stripline

transmission lines. This will help to minimize the parasitic

inductance and capacitance effects. Proper termination of

the differential data signal will prevent reflections and ringing

which would compromise the signal fidelity and generate

unwanted electrical noise. Locate termination at the received

signal end of the transmission line. The length of these lines

should be kept short and of equal length to prevent pulse-

width distortion from occurring. For the high-speed signal

lines, differential signals should be used, not single-ended

signals. These differential signals need to be loaded symmetri-

cally to prevent unbalanced currents from flowing which will

cause distortion in the signal.

2

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