HFBR-0527P Avago Technologies US Inc., HFBR-0527P Datasheet - Page 4

• Manufacturer Part Number: HFBR-0527P
• Description: Fiber Optics, Evaluation Kit
• Manufacturer: Avago Technologies US Inc.

Specifications of HFBR-0527P

• Kit Contents: TX/RX Mods, Cable, Pol Kit, SW, Pwr. Sup
• Tool / Board Applications: Fiber Optic Transceivers
• Mcu Supported Families: HFBR-1527, HFBR-2526
• Main Purpose: Interface, Fiber Optics
• Embedded: No
• Utilized Ic / Part: HFBR-1527, HFBR-2526
• Primary Attributes: 125MBd, Communication up to 25m
• Secondary Attributes: 650nm LED, 1mm POF
• Description/function: Fiber Optic Kit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: HFBR-1527, HFBR-2526
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 516-2143; HFBR-0527P

Figure 4. Attributes of Encoding
Characteristics of Encoders
A Manchester encoder replaces each bit with two symbols,
for instance, a logic “1” is replaced by a (“1”,“0”) symbol, and
a logic “0” is replaced by a (“0”, “1”) symbol. Manchester
code is not very efficient since it doubles the fundamental
frequency of the data by substituting two symbols for each
bit transmitted. Block substitution codes such as 4B5B
replace 4-bit groups of data with a 5-bit symbol. Another
popular block substitution code is 5B6B, which replaces
each group of five bits with a 6-bit symbol. Substitution
codes encode the data more efficiently. If a Manchester
code is used to transmit data at 100 Mbits/second the fiber
optic channel must be capable of passing 200 M symbols/
second. Baud (Bd) is expressed in units of symbols/second,
thus the Manchester encoder in this example requires a
serial data link that can work at 200 MBd. If the Manchester
encoder is replaced by a 4B5B encoder, the 100 M bit/
second data can be sent at a signaling rate of 125 MBd. In
binary transmission systems the maximum fundamental
frequency of the data is half the symbol rate expressed in
Bd. When a Manchester encoder is used to send 100 M bit/
second data, at a symbol rate of 200 MBd, the maximum
fundamental frequency of the data is 100 MHz. By using
a 4B5B encoder, the same 100 M bit/second data can be
transmitted at 125 MBd, at a maximum fundamental
frequency of 62.5 MHz.
The minimum fundamental frequency that the fiber optic
link must pass is determined by the encoding rule chosen.
The run limit of the encoder determines the maximum
number of symbol periods that the encoder will allow
TAXIchip is a registered trademark of Advanced Micro Devices, Inc.
4
100 M BITS/SEC.
SERIAL DATA
SOURCE
0% TO 100% DUTY FACTOR (D.F.)
(100% EFFICIENT)
(50% EFFICIENT)
(80% EFFICIENT)
MANCHESTER
SCRAMBLER
ENCODER
ENCODER
4B5B
2 7 -1
40% TO 60% D.F.
≈
50% D.F.
50% D.F.
100 MBd
NRZ DATA
f o = 50 MHz
200 MBd
ENCODED DATA
f o = 100 MHz
125 MBd
ENCODED DATA
f o = 62.5 MHz
100 MBd
ENCODED DATA
f o = 50 MHz
before it forces a transition, thus the encoder’s run limit
determines the minimum fundamental frequency of
the encoded data. Manchester code will allow only two
symbol periods to pass without a transition. As many as
three symbol times without a transition will be allowed by
the 4B5B encoder used in the AMD TAXIchip
Figure 4 illustrates the attributes of various encoding
techniques. Figure 4 shows that as encoder efficiency
improves the bandwidth needed in the fiber optic com-
munication channel is reduced, or conversely, for a fixed
communication channel bandwidth the number of bits/
second that can be transmitted will go up as encoder
efficiency improves.
Total Solution Cost: 125 Mbd Link Costs
The cost of a 125 MBd link consists of the cost of the data
transceiver, and the cost of the media (cable and connec-
tors). For the recommended +ECL transceiver discussed in
this application note, the material costs in low volume are
approximately $28.
The total material cost for a logic-to-light transceiver is
under $25 in moderate volume, which compares favorably
with the cost of a wire transceiver solution capable of 125
MBd performance over 100 m spans, but the big advan-
tage of this low cost fiber optic technology is its ability to
provide better data integrity than comparably priced wire
alternatives.
TM
.